Download - Brain Herniation
Cerebral Herniation SyndromesImaging findings and clinical correlation
Cerebral Herniation SyndromesImaging findings and clinical correlation
Thomas E.F. Jongsma1, Esther Sanchez2, Paul R.. Algra1
From the departments of Radiology at
Medical Center Alkmaar, Alkmaar, The Netherlands 1
Free University Medical Center, Amsterdam, The Netherlands 2
Definition of Cerebral Herniation:
Definition of Cerebral Herniation:
Herniation of brain tissue from one compartment (separated by calvarial and /or dural boudaries) to another
CompartmentsCompartments
• Supratentorial• Right
• Left
• Infratentorial
• Spinal
Intracranial compartmentsIntracranial compartments
• Brain tissue in each compartment is contained by (relative) intracranial boundaries:• Falx cerebri
• Tentorium cerebelli
• Skull base (foramen magnum)
Falx cerebri
TentoriumCerebelli
Skull Base(Foramen Magnum)
Neurocranium
Intracranial compartmentsIntracranial compartments
Intracranial CompartmentsIntracranial Compartments
• For each compartment there are laws of Intracranial volume en pressure
• Each compartment abides these laws as good as possible
Intracranial volume Intracranial volume
• Intracranial volume is constant and described by “Monro-Kelly Doctrine”:
• Intracranial components are (almost) non-compressible
• Increase in one volume leads to decrease in another
Vol. Intracranial = V. Brain + V. CSF + V. Blood
Intracranial PressureIntracranial Pressure
http://www.trauma.org/archive/neuro/icp.html
Normal intracranial pressure: 5-15 mmHg
Intracranial PressureIntracranial Pressure
• Pressure components: • Cerebral Perfusion Pressure (CPP)
• Mean Arterial Pressure (MAP)
• Intracranial Pressure (ICP)
• CPP = MAP - ICP
• To maintain CPP: If ICP increases, MAP must increase (autoregulation)
Intracranial PressureIntracranial Pressure
• When MAP cannot increase:• Increased ICP decreases CPP
• Decreased CPP leads to tissue ischemia
• Tissue ischemia leads to edema
• Edema leads to increased ICP
• Further increased ICP leads to:
• Tissue death
When compartmental volume increases and
pressure increases, brain tissue moves from one
compartment to another
When compartmental volume increases and
pressure increases, brain tissue moves from one
compartment to another
Causes of volume increaseCauses of volume increase
• Tumour
• Blood• Subdural • Epidural • Parenchymous
• Ischemia
• Infection
Types of herniation :Types of herniation :• Subfalcine
• Transtentorial• Descending• Ascending
• Tonsillar / Foramen Magnum
• Transcranial / “Fungus Cerebri”
• Miscellaneous• Transalar/ Transsphenoidal • Middle ear encephalocele
Subfalcine HerniationSubfalcine Herniation
Mass effect in cerebral hemisphere forces brain tissue under the falx to
opposite side
Subfalcine Herniation:Structures involved
Subfalcine Herniation:Structures involved
• Falx
• Cingulate Gyrus
• Pericallosal Artery
• Anterior Cerebral Artery
• Corpus Callosum
Subfalcine Herniation: Imaging findings
Subfalcine Herniation: Imaging findings
• Ipsilateral cingulate gyrus is pushed down and under midline falx
• Contralateral cingulate gyrus is compressed
• Depression of ipsilateral corpus callosum and elevation / compression of contralateral corpus callosum
Acquired intracranail Herniation: MR Findings, Laine et al. AJR 1995;165: 967-973
Subfalcine HerniationSubfalcine Herniation
• Falx meningioma with extensive surrounding edema
Subfalcine HerniationSubfalcine Herniation
• Displaced pericallosal artery
• Contralateral cingulate gyrus compressed
• Compression of frontal horns of lateral ventricles
•Ipsilateral cingulate gyrus herniates under falx
•Depression / displacement of corpus callosum
Subfalcine Herniation: Complications and Clinical Signs
Subfalcine Herniation: Complications and Clinical Signs
• Compression of the parafalcine cortex may lead to contralateral leg paresis
• Anterior cerebral artery infarction may lead to ipsilateral frontal infarcts
• Increased ICP leads to somnolence
http://missinglink.ucsf.edu/lm/ids_104_cerebrovasc_neuropath/Case4/CerebralArteryDistribution.htm
Subfalcine Herniation:Complications
Subfalcine Herniation:Complications
• CT Angiogram of patient with subdural hematoma on the right shows displacement of anterior cerebral artery without evidence of infarction
Subfalcine Herniation:Complications
Subfalcine Herniation:Complications
• Right sided mass effect was treated by craniotomy. Hypodensity in the right frontal lobe exemplifies anterior cerebral artery infarct after prolonged subfalcine herniation
Transtentorial HerniationTranstentorial Herniation
Descending
Ascending
Descending Transtentorial Herniation
Descending Transtentorial Herniation
Supratentorial mass effect forces cerebral structures downward through
the opening (incisura) of the tentorium
Descending Transtentorial Herniation:Structures Involved
Descending Transtentorial Herniation:Structures Involved
• Tentorium• Uncus• Parahippocampal gyrus• Perimesencephalic cistern• Mesencephalon • Posterior cerebral artery
(-branches)• Anterior Choroidal Artery• Oculomotor Nerve (NIII)
Descending Transtentorial Herniation:Imaging Findings
Descending Transtentorial Herniation:Imaging Findings
• Asymmetry of ambient cistern (ipsilateral widening / contralateral effacement)
• Widening of contralateral temporal horn of lateral ventricle
• Herniated brain is forced medially and inferiorly beneath tentorium, into perimesencephalic cistern
• Compression of ipsilateral cerebral peduncle by uncus
• Compression of contralateral cerebral peduncle against tentorial edge (Kernohan’s Notch)
Acquired intracranail Herniation: MR Findings, Laine et al. AJR 1995;165: 967-973
Descending Transtentorial HerniationDescending Transtentorial Herniation
Chronic (hypodens) rightsided subdural hematoma with unilateral descending transtentorial herniation
Descending transtentorial herniationDescending transtentorial herniation
• Shift of midline structures
• Blood
• Compression of lateral ventricles
• Widened temporal horn
• Medial, downward displacement of uncus over right tentorial edge
Descending transtentorial herniationDescending transtentorial herniation
• Herniated uncus in perimesencephalic cistern
• Ipsilateral midbrain compression
• Asymmetric ambient cistern
Descending transtentorial herniationDescending transtentorial herniation
• Subdural collection on the left with massive descending transtentorial herniation
Descending transtentorial herniationClinical Findings
Descending transtentorial herniationClinical Findings
• Oculomotor (NIII) nerve palsy by compression of third cranial nerve against tentorial edge:
• Exotropic, hypotropic eye position (down and outward)
• Ipsilateral ptosis
• Ipsilateral fixed, dilated pupil
http://scalpelorsword.blogspot.com/2007/01/droopy-eye.html http://www.bartleby.com
Descending transtentorial herniationClinical Findings
Descending transtentorial herniationClinical Findings
• Classic localizing sign: Damage to the pyramidal tracts causes contralateral hemiparesis
• Kernohan’s (Notch) phenomenon: compression of contralateral cerebral peduncle against tentorial edge may result in ipsilateralhemiparesis: “False localizing sign”
Kernohan, J.W., & Woltman, H.W. (1929). Incisura of the crus due to contralateral brain tumor. Archives of Neurology and Psychiatry, 21, 274-287
Descending Transtentorial HerniationComplications
Descending Transtentorial HerniationComplications
• Focal infarction of uncus / parahippocampal gyrus
• Infarction by compression of posterior cerebral artery (-branches) against the tentorial edge
• Infarction by direct compression of the anterior choroidal artery by the uncus
• Brainstem (Duret) hemorrhage
Complications:Vascular structures at risk
Complications:Vascular structures at risk
• MRI images of the vascular structures around the uncus(posterior cerebral artery and anterior choroidal artery). The latter
originates from the anterior cerebral artery and traverses alongthe uncus dorsally (arrows)
Wiesmann et al. Identification and Anatomic Description of the Anterior Choroidal Artery by Use of 3D-TOF Source and 3D-CISS MR Imaging AJNR Am J Neuroradiol 2001; 22: 305-310
Complications:Vascular structures at risk
Complications:Vascular structures at risk
• Anterior choroidal artery compression may lead to infarcts in the posterior limb of the internal capsule and the lateral aspect of the thalamus
• Posterior cerebral artery compression leads to cerebellar and occipital lobe infarction but may also cause thalamic infarcts
http://rad.usuhs.mil/rad/herniation/herniation.html#intro
Complications:Duret Hemorrhage
Complications:Duret Hemorrhage
• Prolonged and progressive transtentorial herniation leads to stretching and eventually rupture of perforating arteries and venules in the brainstem causing punctate hemorrhage
Complications:Duret Hemorrhage
Complications:Duret Hemorrhage
• Extensive descending transtentorial herniation resulting from gunshot wound to the head; Initial CT scan shows Duret
hemorrhage
Ascending Transtentorial Herniation
Ascending Transtentorial Herniation
Posterior fossa mass forces cerebellar structures upwards
through tentorial incisura
Ascending Transtentorial HerniationStructures involved
Ascending Transtentorial HerniationStructures involved
• As in descending transtentorial herniation
• Quadrigeminal plate cistern can be involved
Ascending Transtentorial HerniationImaging findings
Ascending Transtentorial HerniationImaging findings
• Upward displacement of upper cerebellar surface
• Asymmetry/ effacement of ambient cisterns
• Compression of mesencephalon
• Asymmetry/ effacement of quadrigeminal plate cistern
• Often bilateral changes
Ascending Transtentorial HerniationAscending Transtentorial Herniation
Hemorrhagic arteriovenous malformation in the left cerebellar hemisphere with bilateral ascending transtentorial herniation
Ascending Transtentorial HerniationAscending Transtentorial Herniation
• Effacement of perimesencephalic cistern
• Upper surface of cerebellar hemisphere ascends through tentorial incisura
• Hemorrhagic lesion
Ascending Transtentorial HerniationAscending Transtentorial Herniation
• Effacement of quadrigeminal plate cisterns
• Herniation of cerebellum through tentorial incisura
Ascending Transtentorial HerniationAscending Transtentorial Herniation
• Right sided hemorrhagic contusions with mass effect in the right cerebellum causing unilateral ascending
transtentorial herniation
Ascending Transtentorial HerniationAscending Transtentorial Herniation
• Unilateral ascending transtentorial herniation on the right side with compression of the right cerebral peduncle
• Dilated temporal horn of left ventricle indicating onset of hydrocephalus
Ascending Transtentorial Herniationspecial notes
Ascending Transtentorial Herniationspecial notes
• Subtle imaging changes
• Less frequent (-ly noted?) than descending herniation
• Often bilateral (no asymmetry)
• Differing appearance of perimesencephalic cisterns with different gantry angles in CT may complicate imaging findings
Ascending Transtentorial HerniationClinical findings and Complications
Ascending Transtentorial HerniationClinical findings and Complications
• Slowly evolving posterior fossa mass effect will often present with signs of hydrocephalus: Headache, nausea, vomiting etc.
• Compression of arteries (posterior cerebral, superior cerebellar) may lead to cerebral / occipital or cerebellar infarction
• Rapidly expanding lesions present with emergency clinical findings due to compression of brainstem nuclei: respiratory failure, coma and death (often coexistent with foramen magnum herniation)
Tonsillar / Foramen Magnum Herniation
Tonsillar / Foramen Magnum Herniation
Posterior fossa mass effect forces cerebellar tonsils downward through
the foramen magnum
Tonsillar HerniationStructures involved
Tonsillar HerniationStructures involved
• Skull base / foramen magnum
• Cerebellar tonsils
• Posterior inferior cerebellar artery
Tonsillar HerniationTonsillar Herniation
• Right sided tonsillar herniation
Tonsillar HerniationTonsillar Herniation
• Anteriorly displaced cervical myelum
• Inferiorly displaced right cerebellar tonsil
Tonsillar HerniationSpecial notes
Tonsillar HerniationSpecial notes
• (Subtle) extension of cerebellar tonsils in the spinal canal may be seen in normal individuals or in Chiari I malformation
• Extension of 5 mm or more below the foramen magnum is considered abnormal
• Often coexisting with ascending transtentorial herniation
Aboullez etal. Position of cerebellar tonsils in the normal population and in patients with Chiari I malformation: A quantative approach with MR Imaging. J Comp Assist Tomogr 1985;9: 1033-1036
Tonsillar HerniationTonsillar Herniation
• Chiari I malformation with extension of the cerebellum in the upper cervical spinal canal in a patient with a frontal mass
Tonsillar HerniationClinical findings / Complications
Tonsillar HerniationClinical findings / Complications
• Compression of brain stem nuclei causes respiratory / cardiac failure, coma, death
• Compression of posterior inferior cerebellar artery (PICA) may cause cerebellar infarcts
• Patients with Chiari I malformation can be symptom free but may experience dysesthesia with cervical flexion: “ Lhermitte phenomenon”
Transcranial Herniation “Fungus Cerebri”
Transcranial Herniation “Fungus Cerebri”
Intracranial mass effect forces cerebral structures outward through
(iatrogenic) calvarial defect
Transcranial HerniationTranscranial Herniation
• Decompressive right frontal craniotomy in two patients with severe right sided mass effect. Cerebral structures herniate through calvarial defect. Note that there is no midline shift.
Mass effect is orientated away from contralateral hemisphere.
Transcranial HerniationComplications
Transcranial HerniationComplications
• Decompression usually improves patient survival by lowering intracranial pressure and preventing / undoing intracranial herniations
• Herniation may lead to infarction of herniated tissue
• Exposed brain / dura is prone to infection
MiscellaneousMiscellaneous
Transalar / Sphenoidal Herniation
Middle Ear Encephaloceles
Transalar / Sphenoidal Herniation
Transalar / Sphenoidal Herniation
Anterior cranial fossa mass effect forces cerebral structures over the edge of the
sphenoid bone into the middle cranial fossa
Transalar / Sphenoidal Herniation
Transalar / Sphenoidal Herniation
• Coexisting with other forms of herniation
• Rarely recognized; Imaging may show displacement of middle cerebral artery
• No specific clinical signs.
• Complications include (rarely) middle cerebral artery infarct
Middle ear (Skull base) encephalocele
Middle ear (Skull base) encephalocele
Cerebral structures bulge through (acquired) skull base defect
NO PRESSURE COMPONENTS
Middle Ear EncephaloceleMiddle Ear Encephalocele
• Left temporal bone defect with protruding cerebral tissue
Papanikolaou et al. Skull Base. 2007 September; 17(5): 311-316
Middle Ear EncephaloceleMiddle Ear Encephalocele
• Cerebral tissue protruding in left temporal bone
Middle Ear EncephaloceleMiddle Ear Encephalocele
• Focal osseous defect in left tegmen
• Protrusion of cerebral structures in epitympanic space surrounding theossicles
Skull base encephaloceleSkull base encephalocele
• May occur anywhere along the skull base
• Osseous defects may be iatrogenic or congenital
• No specific clinical findings