full story brain herniation imaging dr ahmed esawy
TRANSCRIPT
IMAGING
BRAIN HERNIATION
Dr Ahmed Esawy
MBBS MSc MD
Dr Ahmed Esawy
CLASSIFICATION BRAIN HERNAITION
I Supratentorial herniation 1-Cingulate (subfalcinetransfalcine) 2-Uncal (descending transtentorial herniation DTH) 3-Central (bilateral DTH) 4-Transcalvarial 5-Tectal (posterior)
II-Infratentorial herniation
1-Upward (upward cerebellar or upward transtentorial) 2-Tonsillar (downward cerebellar
III-Sphenoidalar herniation Transalar Herniation Dr Ahmed Esawy
Brain herniation A brain herniation is when brain tissue cerebrospinal fluid and blood vessels are moved or
pressed away from their usual position inside the skull
Causes
Brain herniation occurs when something inside the skull produces pressure that moves brain
tissues This is most often the result of brain swelling from a
bullhead injury stroke
bullor brain tumor
Brain herniation can be a side effect of tumors in the brain including
Metastatic brain tumor
Primary brain tumour (brain tumoursmeningiomabase of skull tumours suprasellar tumours
Herniation of the brain can also be caused by other factors that lead to increased pressure
inside the skull including
bullAbscess
bullHemorrhage (intracerebral subdural extradual)
bullHydrocephalus
bullStrokes that cause brain swelling
bullSwelling after radiation therapy
Dr Ahmed Esawy
Pathology of Increased Intracranial Pressure
Increased intracranial pressure (ICP) - if gt 40 mm Hg cerebral hypoxia cerebral ischemia cerebral edema hydrocephalus and brain herniation
Cerebral edema Edema - Disruption of the blood brain barrier ndash vasodilatation ndash swelling
Hydrocephalus communicating type common in Total Body Irradiation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
CLASSIFICATION BRAIN HERNAITION
I Supratentorial herniation 1-Cingulate (subfalcinetransfalcine) 2-Uncal (descending transtentorial herniation DTH) 3-Central (bilateral DTH) 4-Transcalvarial 5-Tectal (posterior)
II-Infratentorial herniation
1-Upward (upward cerebellar or upward transtentorial) 2-Tonsillar (downward cerebellar
III-Sphenoidalar herniation Transalar Herniation Dr Ahmed Esawy
Brain herniation A brain herniation is when brain tissue cerebrospinal fluid and blood vessels are moved or
pressed away from their usual position inside the skull
Causes
Brain herniation occurs when something inside the skull produces pressure that moves brain
tissues This is most often the result of brain swelling from a
bullhead injury stroke
bullor brain tumor
Brain herniation can be a side effect of tumors in the brain including
Metastatic brain tumor
Primary brain tumour (brain tumoursmeningiomabase of skull tumours suprasellar tumours
Herniation of the brain can also be caused by other factors that lead to increased pressure
inside the skull including
bullAbscess
bullHemorrhage (intracerebral subdural extradual)
bullHydrocephalus
bullStrokes that cause brain swelling
bullSwelling after radiation therapy
Dr Ahmed Esawy
Pathology of Increased Intracranial Pressure
Increased intracranial pressure (ICP) - if gt 40 mm Hg cerebral hypoxia cerebral ischemia cerebral edema hydrocephalus and brain herniation
Cerebral edema Edema - Disruption of the blood brain barrier ndash vasodilatation ndash swelling
Hydrocephalus communicating type common in Total Body Irradiation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Brain herniation A brain herniation is when brain tissue cerebrospinal fluid and blood vessels are moved or
pressed away from their usual position inside the skull
Causes
Brain herniation occurs when something inside the skull produces pressure that moves brain
tissues This is most often the result of brain swelling from a
bullhead injury stroke
bullor brain tumor
Brain herniation can be a side effect of tumors in the brain including
Metastatic brain tumor
Primary brain tumour (brain tumoursmeningiomabase of skull tumours suprasellar tumours
Herniation of the brain can also be caused by other factors that lead to increased pressure
inside the skull including
bullAbscess
bullHemorrhage (intracerebral subdural extradual)
bullHydrocephalus
bullStrokes that cause brain swelling
bullSwelling after radiation therapy
Dr Ahmed Esawy
Pathology of Increased Intracranial Pressure
Increased intracranial pressure (ICP) - if gt 40 mm Hg cerebral hypoxia cerebral ischemia cerebral edema hydrocephalus and brain herniation
Cerebral edema Edema - Disruption of the blood brain barrier ndash vasodilatation ndash swelling
Hydrocephalus communicating type common in Total Body Irradiation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pathology of Increased Intracranial Pressure
Increased intracranial pressure (ICP) - if gt 40 mm Hg cerebral hypoxia cerebral ischemia cerebral edema hydrocephalus and brain herniation
Cerebral edema Edema - Disruption of the blood brain barrier ndash vasodilatation ndash swelling
Hydrocephalus communicating type common in Total Body Irradiation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Cingulate herniation (subfalcinetransfalcine)
Subfalcine herniation on CT In cingulate or subfalcine herniation the most common type the
innermost part of the frontal lobe is scraped under part of the falx cerebri
the dura mater at the top of the head between the two hemispheres of the
brain
Cingulate herniation can be caused when one hemisphere swells and pushes the cingulate gyrus by the falx cerebri cingulate herniation may present with abnormal posturing and coma
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
the cingulate gyrus lies on the medial aspect of the cerebral hemisphere It forms a major part of the limbic system which has functions in emotion and behaviour The frontal portion is termed the anterior cingulate gyrus (or cortex)
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Subfalcine herniation
most common bullsupratentorial mass in one hemicranium bullaffected hemisphere pushes across the midline under the inferior free margin of the falx extending into the contralateral hemicranium Subfalcine herniation imaging Axial and coronal images show that
bullcingulate gyrus bullanterior cerebral artery (ACA) bullinternal cerebral vein (ICV)
are pushed from one side to the other under the falx cerebri The ipsilateral ventricle appears compressed and displaced across the midline
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Subfalcine herniation
Complications
bull unilateral obstructive hydrocephalus ndashforamen of Monro occlusion bullPeriventricular hypodensity with blurred margins of the lateral ventricle ndashFluid accumulates in the periventricular white matter bullWhen severe the herniating ACA can be pinned against the inferior free margin of the falx cerebri bull secondary infarction of the cingulate gyrus
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Subfalcine herniation
from acute SDH
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
acute on chronic subdural hematoma Subfalcine herniation midline shift effacement of the ipsilateral lateral ventricle and enlargement of the contralateral occipital horn are present
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Coronal contrast-enhanced Ti-weighted image of patient with metastatic breast cancer Coronal MR imaging accurately shows ipsilateral cingulate gyrus (asterisk) displaced beneath falx with depression of corpus callosum There is compression of contralateral cingulate gyrus (straight arrow) and corpus callosum Pencailosal artery (curved arrow) is displaced beneath falx Lateral and third ventricles are also displaced
subfaicine herniation
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Degrees of subfalcine herniation A Axial CT scan of right parietal posttraumatic hemorrhage and subdural hematoma (arrowheads) some compression of right lateral ventricle is present with shift to left asso- ciated with mild deviation of anterior faix (arrow) B Axial CT scan of massive right infarct Right lateral ventricle is compressed and markedly displaced to opposite side Note that posterior falx remains non displaced despite massive shift including anterior faix (arrow) Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Paradoxical herniation
The postoperative CT image shows evidence of left craniectomy with a small amount of residual subdural fluid collection and blood
A repeat CT image upon returning after 4 months shows resolution of the subdural fluid collection and blood
after 4 months there is interval demonstration of concave deformity of the left cerebral hemisphere together with the overlying skin flap with associated distortion of the left ventricle and a new left subfalcine paradoxical herniation Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
the tentorium is a structure within the skull formed by the dura mater of the
meninges
Transtentorial herniation can occur when the brain moves either up or down across
the tentorium called ascending and descending transtentorial herniation
respectively however descending herniation is much more common
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending transtentorial herniation types bullUnilateral bullBilateral (centralldquo) Severe
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
In uncal herniation a common subtype of transtentorial herniation the innermost part of the temporal lobe the uncus can be squeezed so much that it moves towards the tentorium and puts pressure on the brainstem most notably the midbrain
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
The uncus is an anterior extremity of the Parahippocampal gyrus It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Parietal lobe
Superior temporal gyrus
Middle temporal gyrus
Pons
Medulla oblongata
Cerebral peduncle
Centrum semiovale
3rd ventricle
Inferior temporal gyrus
Petrous ridge of temporal bone
Parahippocampal gyrus
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pontine cistern pre-pontine cistern
bull Anterior to the pons Location
bull Basilar A
bull AICA
bull Ant Pontomesencephalic V
bull Cn 5
bull Cn 6
Contents
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pontine cistern
Basilar A
Ant Pontomesencephalic V Petrosal V
Superior petrosal sinus
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pontine cistern
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pontine cistern
AICA
BA Cn6 Cn6
BA
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Perimesencephalic cistern
1 Interpeduncular C
2 Crural C
3 Ambient C
4 Quadrigeminal C
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Quadrigeminal cistern vein of Galen cistern
bull Posterior to the quadrigeminal plate
bull Inferior to the splenium of corpus callosum amp
bull Superior to the cerebellum
Location
bull Vein of Galen
bull Precentral V
bull P3 of PCA
Contents
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Chiasmatic cistern Suprasellar cistern
bull Above the sella Location
bull Optic chiasm
bull Pituitary infundibulum
Contents
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
CP angle cistern
AICA
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Superior CP angle cistern
AICA
AICA AICA
AICA
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Inferior CP angle cistern
Cn
910
Cn 10
Cn 9
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations)
the second most common bulla hemispheric mass bullinitially produces subfalcine herniation bullAs the mass effect increases the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation
(Descending transtentorial herniations )
The uncus can squeeze the oculomotor nerve (aka CN III) which may affect the parasympathetic input to the eye on the side of the affected nerve Compression of the ipsilateral posterior cerebral artery Duret hemorrhages (tearing of small vessels in the parenchyma) in the median and paramedian zones of the mesencephalon and pons The sliding uncus syndrome represents uncal herniation without alteration in the level of consciousness and other sequelae mentioned above
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending transtentorial herniation
As DTH increases
hippocampus also herniates medially
quadrigeminal cistern compression
midbrain pushed toward the opposite side of the incisura
Descending transtentorial herniation
severe cases
entire suprasellar and quadrigeminal cisterns are effaced
The temporal horn can even be displaced almost into the midline
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Brain herniation 1 subfalcine 2 herniation of the uncus and hippocampal gyrus of the temporal lobe into the tentorial notch causing pressure on the third nerve and mid-brain 3 brainstem caudally 4 cerebellar tonsils through foramen magnum
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation is when the medial portion of the anterior temporal lobe is shifted into the suprasellar cistern It is a subset of descending transtenorial herniation which is when the cerebral hemisphere crosses the tentorium at the level of the incisura It can result in Infarct in the PCA distribution
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
A large right frontotemporal subdural hematoma is exerting mass effect on the right frontal and temporal lobes with resultant effacement of the suprasellar cistern and with right-sided uncal herniation
effaces the ipsilateral temporal horn causing dilatation of the contralateral temporal horn Subfalcine herniation and narrowing of the contralateral ambient and quadrigeminal plate cisterns are present
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Acute-on-chronic right temporal subdural hematoma exerts mass effect on the right temporal lobe causing ipsilateral temporal horn with effacement and dilatation of the contralateral temporal horn Narrowing of the contralateral ambient and quadrigeminal plate cisterns is present with ipsilateral widening of the ambient and quadrigeminal cisterns
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Duret hemorrhage with cerebral herniation Large left holohemispheric and parafalcine subdural hematoma (short black arrows a) results in midline shift (long black arrow a) and uncal (long white arrow b) herniation Downward brainstem herniation has led to classic Duret hemorrhage (short white arrow b) in the paramedian midbrain
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
descending transtentorial herniation A-C Axial diagram (A ) axial CT scan (B) and axial T2-weighted MR image (C) show components of left unilateral descending transtentorial herniation (straight arrows) Brainstem is rotated and displaced to opposite side and caudally producing widening of ipsilateral ambient cistern (curved arrows) Compression of neck of contralateral temporal horn results in its dilatation (asterisk
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending transtentonal herniation A and B Coronal diagram (A) and coronal Ti-weighted MR Image (B) show components of left unilateral descending transtentorial herniation (curved arrows) MR image shows extent of herniation across tentorium and deviation of brainstem
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
bilateral DTH
both hemispheres become swollen the whole central brain is flattened against the skull base
All the basal cisterns are obliterated
hypothalamus and optic chiasm are crushed against the sella turcica
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Central herniation(bilateral DTH) In central herniation the diencephalon and parts of the temporal lobes of both of the cerebral hemispheres are squeezed through a notch in the tentorium cerebelli
Radiographically downward herniation is characterized by obliteration of the suprasellar cistern from temporal lobe herniation into the tentorial hiatus with associated compression on the cerebral peduncles Upwards herniation on the other hand can be radiographically characterized by obliteration of the quadrigeminal cistern Intracranial hypotension syndrome has been known to mimic downwards transtentorial herniation
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Complete bilateral DTH
both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90deg to almost 0deg
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Complete bilateral DTH
Complications
bullCN III (oculomotor) nerve compression ndashCN III palsy bullPCA occlusion as it passes back up over the medial edge of the tentorium
ndashsecondary PCA (occipital) infarct Duret hemorrhage
diabetes insipidus due to the compression of the pituitary stalk
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
BILateral descending transtentorlal herniation Axial CT scan reveals bilateral descending transtentorial herniation with obliteration of perimesencephalic cisterns Dorsal midbrain is compressed and dongated anteroposteriorly causing pear-shaped deformity (asterisk) Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Nine-year-old boy with diffuse cerebral edema and central herniation secondary to treatment of DKA Juvenile Diabetic Ketoacidosis A Axial noncontrast CT scan shows diffuse cerebral edema with effacement of sulci and basal cisterns B Axial noncontrast CT scan obtained 2 days after A shows marked low-density infarcts in the gyrus recti and medial orbital gyri (arrows) globus pallidi hippocampiparahippocampal gyri hypothalamus midbrain and posterior right temporal lobe
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
CndashD Axial noncontrast T2-weighted (40001051) (C) and coronal postcontrast T1-weighted SPGR (144371) (D) MR images obtained 24 days after A show cavitary infarcts in the gyrus recti and medial orbital gyri (arrows) medial temporal lobes midbrain and thalami Enhancement is present within the thalamic and midbrain lesions There is diffuse cerebral atrophy
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Kernohan notch
bullKernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect resulting in indentation in the contralateral cerebral crus by the tentorium cerebelli This has also been referred to as Kernohan-Woltman notch phenomenon and false localising sign As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura contralateral cerebral peduncle is forced against the hard edge of the tentorium Pressure ischemia ipsilateral hemiplegia the false localizing sign
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
flair T1
T1+C
subfalcine and downward transtentorial Kernohan phenomenon
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
T1+C
FLAIR
T2
T2
ASTROCYTOMA
GII
DOWNWARD
TRANTENTORAIL
HERNIATION
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal herniation with Kernohan phenomenon
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
complications of transtentorial herniation Midbrain (Duretrsquos) hemorrhage Axial CT scan of patient with head trauma reveals left transtentorial herniation with deformity of brainstem Midline hemorrhage is seen within upper pons (arrow) caused by herniation
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Infratentorial herniation
DESCENDING TONSILLAR HERNIATION
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Tentorial incisure (also known as the tentorial notch or incisura tentorii) to
the anterior opening between the free edge of the tentorium cerebelli and theclivus for the passage of the brainstem Its located between the tentorial edges and communicates the supratentorial and infratentorial spaces
Tentorial incisure seen from above
The propensity of tonsillar herniation to follow descending tentorial herniation is related to the size and shape of the incisura If the incisura is small the patient will be less likely to have tonsillar herniation
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Downward Tonsillar herniation In tonsillar herniation also called downward cerebellar herniation] transforaminal herniation or coning the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord Tonsillar herniation of the cerebellum is also known as a Chiari malformation (CM) Cerebellar tonsillar ectopia (CTE) is a term used by radiologists to describe cerebellar tonsils that are low lying
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending Tonsillar herniation
bullThe cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum bullcongenital (eg Chiari 1 malformation) ndash mismatch between size and content of the posterior fossa bullAcquired ndashan expanding posterior fossa mass (tumour haemorrhagestroke abscess) pushing the tonsils downwardmdashmore common ndashintracranial hypotension abnormally low intraspinal CSF pressure tonsils are pulled downward
Diagnosing tonsillar herniation on NECT scans may be problematic Cisterna magna obliteration
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
life threatening tonsillar herniation exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla such as the respiratory and cardiac centres Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Sagittal T1-weighted magnetic resonance image of the brain Anatomic landmarks identified include the fourth ventricle (A) basion (B) medulla oblongata (C) cerebellar tonsil (D) opisthion (E) cerebellar hemisphere (F)
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
he distance is measured by drawing a line from the inner margins foramen magnum (basion to opisthion) and measuring the inferior most part of the tonsils As is to be expected values used vary somewhat from author to author
above foramen magnum normal lt5 mm also normal but the term benign tonsillar ectopia can be used gt5 mm Chiari 1 malformation
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
-A Drawing showing basion (B) opisthion (0) and cerebellar tonsil (T) in a normal patient B Midline sagittal section SE 50040 showing line from basion to opisthion in a nomal patient Measurements were from this
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
reference line Bottoms of tonsils have a normal rounded appearance and CSF is seen in a normal cisterna magna
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Coronal SE 70040 through medulla and tonsils The lower limits of foramen magnum are difficult to identify Coronal scans were not used for this reason
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending Tonsillar herniation MR much more easily diagnosed bullIn the sagittal plane ndashthe tonsillar folia become vertically oriented ndashthe inferior aspect of the tonsils becomes pointed ndashTonsils gt 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal especially if they are peg-like or pointed (rather than rounded)
In the axial plane T2 scans show that the tonsils are impacted into the foramen magnum ndashobliterating CSF in the cisterna magna ndashdisplacing the medulla anteriorly
Complications bullobstructive hydrocephalus bulltonsillar necrosis Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Normal anatomy of the cerebellum (left) Chiari I malformation (right) With the size of the posterior fossa too small the cerebellar tonsils may herniate through the skull into the spinal canal The tonsils block the flow of CSF (blue) and may cause fluid buildup inside the spinal cord called a syrinx
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
A Midline sagittal SE 50040 scan in a symptomatic patient Tonsils extend 11 cm below foramen magnum Tonsils are pointed and cisterna magna is obliterated The latter two findings were seen in both asymptomatic
symptomatic patients with low tonsils B Midline sagittal SE 50040 scan after decompression via suboccipital craniectomy Tonsils now have a normal rounded appearance
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Typical MRI manifestation of brain saggingMidsagittal T1-weighted MRI shows downward displacement of the cerebellar tonsil by 5 mm (arrow)
brain sagging which was defined as either cerebral aqueduct displacement ge18 mm or cerebellar tonsil displacement ge43 mm
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Typical MRI manifestation of the venous distension signT1-weighted MRI through the midportion of the dominant transverse sinus shows the venous distension sign (box)
subdural haematoma in patients with spontaneous intracranial hypotension
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
An MRI of the brain shows the cerebellar tonsils (arrow) herniating through the foramen magnum (yellow line)
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
With a loss in CSF volume there is a greater increase in blood volume This results in dural venous hyperemia and pachymeningeal venous engorgement and edema which can be identified on MR imaging as diffuse pachymeningeal enhancement Furthermore the decrease in volume of the suspending CSF results in downward descent of the brain and can cause descending central transtentorial herniation and tonsillar herniation A blood patch or surgical repair of the dural defect is usually required
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Intracranial hypotension (A) Coronal enhanced T1-weighted MR image demonstrates diffuse pachymeningeal enhancement (arrows) in a patient with severe postural headaches (B) Sagittal enhanced T1-weighted NM image reveals tonsillar herniation (arrow) descending transtentorial herniation (note downward descent of the brainstem loss of surrounding CSF spaces and flattening of the pons against the clivus) and pachymeningeal enhancement (arrowheads) (C) Postmyelogram CT scan of the thoracic spine shows an extradural accumulation of contrast (arrow) within die spinal canal consistent with a CSF leak The extradural and intradural confluent medium outlines the dura (arrowhead) at the T10 level A blood patch performed at this level resulted in resolution of the patients symptoms Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Tonsillar herniation Sagittal enhanced T I -weighted MR image demonstrates a large enhancing cerebellar mass causing both tonsillar herniation and ascending transtentorial herniation Note the inferior displacement of the tonsils (arrow) below the foramen magnum and the effacement of the surrounding CSF spaces The brainstem is compressed and displaced against the clivus and there is upward displacement of the superior cerebellar vermis (arrowhead) through the incisura Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Foramen magnumtonsillar herniation
child with a history of an Arnold-Chiari I malformation Image shows tonsillar herniation with compression of the central canal at the craniocervical junction and resultant syringohydromyelia in the visualized portion of the cervical spinal cord
T2- through the cervical spine was obtained in the same patient as in the previous image The cerebellar tonsils are projecting inferiorly below the level of the opisthion with compression of the central canal at the craniocervical junction Hyperintense syringohydromyelia in the visualized portion of the cervical spinal cord is demonstrated Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
tonsiliar herniation and ascending transtentorial herniation A Sagittal Ti -weighted MR image of patient with cerebellar astrocytoma Cerebeliar tonsils are displaced through foramen magnum compressing medulla and upper cervical cord Note that there is also ascending transtentorial herniation with tentorium bowed superiorly (curved arrow) B Axial contrast-enhanced Ti-weighted MR image shows cerebeliar tonsils (asterisks) displaced into foramen magnum Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
ASCENDING TRANSTENTORIAL HERNIATION
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Upward herniation
Increased pressure in the posterior fossa can cause the cerebellum to move up through the tentorial opening in upward or cerebellar herniationThe midbrain is pushed through the tentorial notch
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Ascending transtentorial herniation
caused by any expanding posterior fossa mass Neoplasms gt trauma
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
MR and CT findings of ascending transtentorial herniation include
Effacement of the superior cerebellar cistern superior displacement of the superior vermis through the incisura compression of the midbrain forward displacement of the pons against the clivus
can compress the posterior cerebral artery or superior cerebellar arteries against the tentorium resulting in infarctions can compress the aqueduct of Sylvius resulting in hydrocephalus Obstruction of venous outflow by compression of the vein of Galen and basal vein of Rosenthal may occur and further increase intracranial pressure
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
(5) ascending transtentorial
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Ascending transtentorial herniation (A) Axial T I - weighted MR image and (B) sagittal enhanced T I -weighted MR image demonstrate ascending transtentorial herniation in a patient with a cerebellar lung metastases Note the upward displacement of the superior cerebellar vermis (black arrows) through the incisura compression of the fourth ventricle and anterior displacement of the pons (arrowhead) against the clivus
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Ascending transtentorial herniation
Right parasagittal gadolinium-enhanced T1-weighted magnetic resonance image in a 9-year-old girl with a history of right cerebellar astrocytoma who presented with headaches and vomiting Heterogeneously enhancing mass is demonstrated in the right cerebellum with compression of the adjacent brainstem and fourth ventricle Ascending transtentorial herniation of the cerebellum is demonstrated through the incisura Descending tonsillar herniation also is present
Axial gadolinium-enhanced T1-weighted magnetic resonance image obtained at the level of the midbrain in the same patient as in the previous image A heterogeneously enhancing mass is seen in the right medial anterior cerebellum with mass effect on the right posterior lateral midbrain and fourth ventricle The image shows enlargement of the temporal horns of both lateral ventricles as a result of obstruction by the cerebellar mass at the level of the fourth ventricle Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
upward herniation from cerebellar infarction oedema
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
ascending transtentorial herniation Axial CT scan obtained after posterior fossa surgery with subsequent cerebellar hemorrhage and edema Perimesencephalic cistern is effaced Trapped temporal horns are caused by aqueductal compression and hydrocephalus
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
unilateral ascending transtentorial herniation A Axial CT scan of patient with right cere- bellar astrocytoma shows distortion of right quadrlgeminal cistern (arrow) and brainstem compression caused by upward herniation B Axial Ti-weighted MR image shows leftsided cerebellar cystic medulloblastoma with marked compression and rotation of midbrain Frequently midbrain is elevated and pons following midbrain is forced against clivus
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Sphenoidalar
herniation
Transalar Herniation
brain herniates across the greater sphenoid wing (GSW) or ala ascending gt descending
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
descending transalar herniation
Descending transphenoidal herniation occurs when anterior cranial fossa mass effect causes displacement of the posterior frontal lobe over the sphenoid wing into the middle cranial fossa
Ascending transalar herniation Ascending transphenoidal herniation is produced by middle cranial fossa mass effect which causes displacement of the anterior temporal lobe over the sphenoid ridge into the anterior cranial fossa
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
transalar herniation
Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing The middle cerebral artery can become compressed between the displaced brain and the sphenoid ridge resulting in middle cerebral artery infarction Although vascular compromise may occur with transphenoidal herniation it is rare Moreover the clinical features of this type of herniation are poorly defined
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
ascending transalar herniation Axial contrast-enhanced CT scan of patient with right temporal lobe gliobiastoma shows contrast filled right middle cerebral artery (arrow) displaced anteriorly Also present is asymmetry and effacement of ipsilateral sylvian fissure These changes indicate ascending transalar herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Transphenoidal herniation Sagittal enhanced Tl- weighted MR image demonstrates a large ring enhancing mass (arrowhead) in the right frontal lobe causing descending transphenoidal herniation (arrow)
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Descending transalar herniation A Coronal enhanced Ti-weighted MR image shows left frontal lobe glioblastoma When compared with normal right side medial orbital gyrus of left frontal lobe Is displaced over sphenold ridge into middle cranial fossa (arrow) B Sagittal enhanced Ti-weighted MR image shows tumor and resultant transalar herniation (arrow) Left syivian fissure is effaced Compare this image with normal right side C Sagittal enhanced Ti-weighted MR image shows normal position of right frontal lobe (asterisk) above sylvian fissure (arrow
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transdural
herniation
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Extracranial herniation Transcalvarial transduralTranscranial herniation the brain squeezes through a fracture or a surgical site in the skull Also called external herniation bullTraumatic ndashinfants or young children with a comminuted inward skull fracture bullIatrogenic ndasha burr hole craniotomy or craniectomy
MR best depicts these unusual herniations bullThe disrupted dura ndashdiscontinuous black line on T2WI ndashBrain tissue blood vessels and CSF are extruded through the defects into the subgaleal space
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Nonenhanced computed tomography (CT) scan of the brain at the level of the body of the lateral ventricles was obtained in a 37-year-old man who underwent a right frontotemporal decompression craniectomy for a large right frontal hematoma after a skiing accident A focal hypoattenuating infarct is seen in the right frontal lobe with an adjacent edematous brain parenchyma herniating through the right frontotemporal craniectomy defect The patient had communicating hydrocephalus with dilatation of the lateral ventricles
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
fungus cerebri A Axial CT scan of patient with chronic head injury shows left hemispheric encephalomaiacia and dilated lateral ventricle Brain tis- sue is identified herniating through calvarlal defect B Axial Ti-weighted MR image of patient with severe head trauma Swollen brain is seen herniating through calvarial defect (arrows outline margins of defect ) Hemorrhage is seen adjacent to defectrsquos anterior rim which may be result of herniatlon or initial injur
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
focal herniation Into surgical defect Coronal contrast- enhanced Ti-weighted MR image of patient following radical mastoidectomy for cholesteatoma that extended into epitympanum and mastoid antrum Postoperatively there Is dehiscence of tegmen tympani with focal herniatlon of temporal lobe into middle ear cavity (arrow) sur- rounded by enhancing granulation tissue This finding can easily be misinterpreted as middle ear mass Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Common CNS Herniations
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Cerebral Herniation Pathogenesis Site of
herniation Effect Clinical consequence
Transtentorial Ipsilateral 3rd cranial nerve
compression
Ipsilateral fixed dilated pupil
Ipsilateral 6th cranial nerve
compression
Horizontal diplopia convergent squint
Posterior cerebral artery
compression
Occipital infarction Cortical blindness
Cerebral peduncle
compression
Upper motor neurone signs
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure
Death
Foramen
magnum
Brainstem compression and
haemorrhage
Decerebrate posture Cardiorespiratory
failure Death
Acute obstruction of CSF
pathway
Decerebrate posture Cardiorespiratory
failure
Death Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
THANK YOU
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Pathogenesis
Supratentorial herniation common 3 sub types
Subfalcine herniation The cingulate gyrus of the frontal lobe (commonest) The brain can shift across falx cerebri
Central transtentorial herniation displacement of the basal nuclei and cerebral hemispheres downward
Uncal herniation Medial edge of the uncus and the hippocampal gyrus
infratentorial herniation Cerebellar (tonsillar) herniation - tonsil of the cerebellum is pushed through the foramen magnum and compresses the medulla leading to bradycardia and respiratory arrest
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Subfalcine Herniation in brain trauma
Contusion of the inferior temporal lobe (blue arrow) has resulted in diffuse edema (compressed and flattened gyri on the right)
This has resulted in subfalcine herniation of the cingulate gyrus (red arrow) with a secondary hemorrhagic infarction above that (black arrow) A midline shift from right to left is also present as is uncal herniation (yellow arrow)
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal Herniation
Inferior view The herniated uncus is bulging over the position of the tentorium (black arrows) and compressing the midbrain The two mammillary bodies (blue arrows) have been shifted to the patients right due to the pressure
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Uncal Herniation
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
acute brain swelling + Uncal Herniation
Swelling of the left cerebral hemisphere has produced a shift with herniation of the uncus of the hippocampus through the tentorium leading to the groove seen at the white arrow
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Cerebellar Tonsil - Herniation
Note the cone shape of the herniated tonsils around the medulla in this cerebellum specimen
Results in compression and Duret hemorrhages in the pons
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy
Transtentorial herniation
Transtentorial herniation at the base of the brain A prominent groove surrounds the displaced parahippocampal gyrus (arrow) The adjacent 3rd nerve (N) is compressed and distorted and the ipsilateral cerebral peduncle (P) is distorted with small areas of haemorrhage
Dr Ahmed Esawy