brain presentation

8/2/2019 Brain Presentation

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Brain brainstem andcerebellumBeatriz Junqueira-Duarte

Diagnostic ImagingPGY 1, University of Toronto


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Outline Topics:

Brainstem:

Midbrain;

Pons;

Medulla oblongata; Cerebellum.

For each topic:

Anatomy;

Images +/- Pathology;

Cases.


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Normal Anatomy

Pineal gld (with cyst)

Midbrain tectum

Pituitarycerebellum

Pons

Medulla

Midbrain

Cerebellar tonsils


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Posterior fossa

metastasisLeiomyosarcoma

PATIENT HAD LEIOMYOSARCOMA!!!


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Brainstem


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Brainstem Conduit between:

Cerebral cortex; Cerebellum;

Spinal cord;

Gray matter formations;

10/12 cranial nerves hastheir nuclei in it:

CN 3-4: Midbrain;

CN 5-8: Pons; CN 9-12: Medulla;

White matter tracts.


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Reticular formation Tegmentum:

In all 3 segments; Functions:

Complex motor patterns;

Aspects of respiratory and

cardiovascular activity;

Regulation ofconsciousness;

Reticular formation:

Central core;

CN nuclei;

Ascending + descendingtracts.


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BrainstemMidbrain


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Midbrain Junction of the middle and

posterior cranial fossa;

Surrounds the cerebralaqueduct:

Connects the 3rd and 4th

ventricles.

midbrain

Left cerebral peduncle


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Midbrain 3 major segments

Tectum

Aka, quadrigeminal plate:

Superior colliculi pair; Inferior colliculi pair;

White matter tracts;

Tegmentum

White matter tract;

Gray matter formation: Substancia nigra;

Red nucleus;

Periaqueductal gray

matter; CN nuclei.

Cerebral peduncles


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MidbrainTectum / Quadrigeminal plate

Dorsal surface of the midbrain;

Colliculis:

4 rounded protuberances;

Superior colliculi pair: Visual reflexes that coordinate

eye movements w movs/ ofthe head and neck;

Inferior colliculi pair:

Relay station for the auditorypathway, providing auditoryinformation to the thalamus.


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MidbrainCerebral peduncles

Anterior to the cerebral aqueduct;

White matter axons:

Corticospinal;

Corticobulbar;

Corticopontine;

Cerebral cortex internal capsule

cerebral peduncles pontine bulb

medullary pyramids spinal cord.


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Midbrain - TegmentumWhite matter tracts

Medial longitudinalfasciculus:

Oculomotor-vestibular;

Medial lemniscus: Somatosensory;

Lateral lemniscus:

Auditory;

Spinothalamic tract:

Somatosensory;

Central tegmental tract:

Motor.


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Midbrain Tegmentum

Gray matter formation

Substantia nigra:

Broad layer of cellsthat contain melanin;

Production ofdopamin:

Control ofmuscular reflexes.


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Midbrain Tegmentum

Red nucleus:

Tract of motor nerve fibers;

Relay station betweencerebellum and the cerebralhemispheres;

Contributes to coordination ofmovs/ and sense of balance;

Periaqueductal gray matter:

Surrounds the cerebral

aqueduct;

Receives sensory input thatconveys pain andtemperature to the brain.

Gray matter formation


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Midbrain


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MidbrainOculomotor CN3

Superior colliculus level;

Paramedian, anterior tocerebral aqueduct;

Motor nuclei consists of fiveindividual motor subnuclei thatsupply individual extraocularmuscles;

Edinger-Westphal

parasympathetic nuclei: Dorsal to CN3 nucleus in

periaquaductal grey;

CN3 fibers course anteriorlythrough midbrain to exit at

interpeduncular fossa.

Trochlear CN4

Inferior colliculus level;

Paramedian, anterior tocerebral aqueduct;

Dorsal to medial longitudinalfasciculus;

CN4 fibers course posteriorlyaround cerebral aqueduct,

decussate in superiormedullary velum;

CN4 exits dorsal midbrainjust inferior to inferior

colliculus.


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Cranial nerves - Midbrain


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MidbrainBlood supply

Small perforating branchesfrom:

Basilar artery;

Superior cerebellar artery; Posterior cerebral arteries.


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MidbrainAdjacent CSF cisterns

Interpeduncular:

Anterior;

CN3;

Ambient (perimesencephalic):

Lateral;

CN4;

Quadrigeminal plate:

Posterior;

CN4.


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What is seen in imaging? CN3: level of superior colliculus, in interpeduncular fossa;

CN4: level of inferior colliculus, seen dorsally and in ambient cistern as wraps aroundmidbrain;

Cerebral aqueduct: Signal varies due to flow artifact;

CN nuclei and white matter tracts can be identified by typical location, but are not

resolved on imaging;

Substantia nigraand red nucleuswell seen.


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Midbrain Coronal T2-weighted MRI:

1, Lateral ventricle;

2, Cingulate gyrus;

3, Corpus callosum;

4, Superior temporal gyrus;

5, Middle temporal gyrus;

6, Inferior temporal gyrus;

7, Spinal cord;

8, Medulla;

9, Pons; 10, Red nucleus;

11, Thalamus.


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BrainstemPons


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Pons Between midbrain and

medulla oblongata;

Posterior to the clivus* andanterior to the cerebellum;

Literally means bridge;

Relay signals between thespinal cord, cerebral andcerebellar cortices;

4th ventricle: Between dorsal pons/upper

medulla and cerebellum.

*Basilar occipital bone w sphenoid bone.


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Pons 2 major segments

Ventral (anterior) pons:

Aka, pontine bulb or belly;

White matter axons:

Corticospinal;

Corticobulbar;

Corticopontine;

Cerebral cortex internalcapsule cerebral

peduncles pontine bulb medullary pyramids

spinal cord.

Dorsal tegmentum:

White matter tracts;

CN nuclei;

Continuous with:

Midbrain tegmentumsuperiorly;

Medullary tegmentuminferiorly.


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Pons tegmentumWhite matter tracts



Medial lemniscus: Somatosensory;

Lateral lemniscus:

Auditory;


Somatosensory;


Motor;

Trapezoid body:

Auditory.


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Pons tegmentumTrigeminal CN5

Nucleus located throughoutbrainstem and upper cord;

Bulk of motor, main sensory

and mesencephalic nucleilocated in pons.

Abducent CN6

Nucleus located in pontinetegmentum near midline,anterior to fourth ventricle;

Axons of facial nerve (CN7)loop around abducensnucleus creating a bulge infloor of fourth ventricle, thefacial colliculus.


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Pons tegmentumFacial CN7

CN7 has three main nucleiwithin pons:

Motor;

Superior salivatory;

Solitary tract;

Located in ventrolateralaspect of tegmentum of

lower pons.

Vestibulocochlear CN8

CN8 has cochlear andvestibular nuclei:

Vestibular nuclei beneath

lateral recess along floor of

fourth ventricle (rhomboidfossa);

Dorsal and ventral cochlearnuclei on lateral surface of

inferior cerebellar peduncle(restiform body).


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Cranial nerves - Pons


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Pons Cerebellopontine angle (CPA).


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Pons Rhomboid fossa of the 4th ventricle:

Rostral half is formed by dorsal surface of the pons


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What is it?

pons

3

1

2


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PonsAdjacent CSF cisterns

Prepontine cistern:

Anterior;

CN5 & 6;

CPA cistern: Lateral;

CN7 & 8.


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PonsBlood supply

Medial branches of:

Superior cerebellar arteries;

Perforating branches ofbasilar artery.


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What is seen in imaging? CN root entry and exit zones visualized:

CN5 root entry zone at mid lateral pons;

CN6 exit anteriorly at pontomedullary junction;

CN7 exit lateral brainstem at pontomedullary junction;

CN8 enters post. to CN7 at pontomedullary junction;

CN nuclei not resolved on conventional imaging;

Specific white matter tracts can be identified by typical

location, but are not resolved on imaging; Cerebellopontine angle (CPA): junction between pons

and cerebellum.

P ti


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Prepontine

meningiomaDURAL-BASED MASS!!!


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Brainstem

Medulla Oblongata


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Medulla Oblongata From pons to foramen

magnum, where it continues

as the spinal cord;

All fiber tracts between thebrain and the spinal cord;

Inferior 4th ventricle: Posterior to the medulla;

Centers that control:

HR, BP and RR.


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Medulla Oblongata

Anterior median fissure;

Posterior median fissure;

Two symmetric halves.

medulla

Cerebellar tonsils

cerebellum


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Medulla Oblongata

Junction of medullawith cervical spinalcord


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Medulla Oblongata2 major segments

Ventral (anterior) medulla Pyramidal tract;

Olive.

Tegmentum (posterior) White matter tracts;

CN nuclei.


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Medulla Oblongata ventralPyramids

Either side of ant. median fissure;

Corticospinal tract:

Voluntary motor control;

Corticobulbar tract;

Inferior decussation ofpyramids;

Cerebral cortex internal capsule cerebral peduncles pontinebulb medullary pyramids

spinal cord.


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Medulla Oblongata ventralOlives

Lateral surface of themedulla oblongata;

Rounded oval prominence;

Nuclei involved in:

Coordination;

Balance;

Modulation of sound

impulses from inner ear.

(2) aka, postolivary sulcus

(1) aka, preolivary sulcus

(1)

(2)

Medulla Oblongata


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Medulla Oblongata

tegmentum

White matter tracts



Medial lemniscus: Auditory;


Somatosensory;


Motor;

Spinocerebellar tract:

Somatosensory.

Medulla Oblongata


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Medulla Oblongata

tegmentum

Glossopharyngeal CN9

CN9 nuclei is in upper andmid medulla:

Nucleus ambiguus;

Solitary tract nucleus;

Inferior salivatory nucleus;

Sensory fibers terminate inspinal nucleus CN5;

CN9 exits medulla inpostolivary sulcus aboveCN10.

Vagus CN10

CN10 nuclei in upper andmid medulla:

Nucleus ambiguus;

Solitary tract nucleus;

Dorsal vagal nucleus;

Sensory fibers terminate inspinal nucleus CN5

CN10 exits medulla inpostolivary sulcus betweenCN9 and 11.

Medulla Oblongata


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Medulla Oblongata

tegmentum

Accessory CN11

Bulbar nuclei in lowernucleus ambiguus in upperand mid medulla;

CN11 exits medulla inpostolivary sulcus belowCN10.

Hypoglossal CN12

CN12 nuclei in mid medulla,dorsally results inhypoglossal eminence ortrigone (bulge in fourth

ventricle);

CN12 exits anterior medullain pre-olivary sulcus.


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Cranial nerves - Medulla

Medulla


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Medulla

OblongataBlood supply

Distal vertebral arteries;

Posterior inferior cerebellararteries;

Anterior spinal artery.


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What is seen in imaging? Medullary olives and pyramids well seen; CN9-12 seen as they exit medulla:

CN9-11 postolivary sulcus;

CN12 pre-olivary sulcus;

CN nuclei and white matter tracts can be identified by typical location,but are not resolved on imaging.

Medulla


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Medulla

Oblongata Axial T1-weighted MRI:

1, Nasal concha;

2, Left maxillary sinus;

3, Clivus;

4, Medulla;

5, Cerebellar tonsil;

6, Cerebellar peduncle.

ROUND DENSE ARISES FROM THE


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Medulloblastoma

ROUND, DENSE, ARISES FROM THEROOF OF THE 4TH VENTRICLE!!!


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Cerebellum


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Cerebellum Posterior fossa;

Posterior to the brainstemand 4th ventricle;

Uses brainstem to connectwith the cerebrum to:

Muscle tone; Posture;

Balance;

Coordination.

cerebellum


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Cerebellum 2 Cerebellar hemispheres;

Midline

vermis: Connects hemispheres.

Three surfaces:

Superior, inferior and

anterior;

3 paired peduncles:

Connects to brainstem;

Cortical gray matter;

Central white matter;

4 paired deep gray nuclei.


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Cerebellum Divided into lobes and

lobules by transverse

fissures.


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CerebellumLobules of Superior Vermis Associated Hemispheric lobules pair

Lingula (anterior) Wing of lingula

Central lobule Wing of central lobule

Culmen Quadrangular lobule

Declive Simple lobule

Folium (posterior) Superior semilunar lobule

Lobules of Inferior Vermis Associated Hemispheric lobules pair

Tuber Inferior semilunar lobule

Pyramid Biventricular lobuleUvula Tonsils

Nodule Flocculus


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Cerebellum Cerebellar tonsils:

2 Rounded prominences;

Inferomedial part of theinferior surface.

cerebellum

Cerebellar tonsils


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Arnold-Chiari malformation


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CerebellumCerebellar peduncles

3 pairs of nerve fiber tracts;

Superior cerebellarpeduncles:

Midbrain;

Middle cerebellum peduncles:

Pons;

Inferior cerebellum peduncles:

Medulla oblongata.


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Cerebellum4 paired deep gray nuclei

Dentate nuclei:

Largest;

Most lateral;

Project to thalamus via

superior cerebellarpeduncles;

From thalamus to precentralgyrus (motor cortex).


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CerebellumMiddle cerebellar peduncle

cerebellum


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Cerebellum

Coronal T2-weighted cut.

Brain MRI:

1, Lateral ventricle;

2, Fornix;

3, Colliculus;

4, Cerebellar hemisphere;

5, Middle cerebellar

peduncle;

6, 4th ventricle;

7, Tentorium cerebelli.

Cerebellum Quadrigeminal platecistern:


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Adjacent CSF cisterns

CPA cistern:

Lateral;

Cisterna magna:

Inferior;

cistern:

Posterior to midbrain,above cerebellum

Superior cerebellar cistern:

Above cerebellum, below

tentorium.


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CerebellumBlood supply

Superior cerebellar artery;

Anterior inferior cerebellarartery;

Posterior inferior cerebellar

artery.


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Cerebellum blood supply


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Cerebellar Infarct

CNS lymphoma


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y pinvolving Cerebellum


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Quick Review!!!


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Questions! Which part of the midbrain is unique (no correspondent

in other segments of brainstem)?

Where is the cerebral aqueduct?

Where is the 4th ventricle?


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Vessels


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Cranial nerves


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Cases

Case 1


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Thin-walled, well-delineated, ring-enhancingcystic-appearing mass


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Cerebellar abscess

Case 2


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Rapid correction ofhyponatremia!!!


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Central Pontine Myelinolysis

Case 3


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CSF peritoneal shunt catheter previously!!!


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Endometrial tissue CSF peritoneal shunt catheter previously;

Case 4 (1/2)


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Multiple plaques involving corpus callosum and pons!!!

Case 4 (2/2)


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CSF positive for oligoclonal bands!!!


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Multiple Sclerosis

Case 5Avidly enhancing cylindrical (IAC) or "ice cream on cone" (CPA-IAC) mass!!!


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Location: within CPA cistern!!!


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Acoustic Neuroma

Case 6Soft or "plastic" tumor!!!


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Heterogenous signal. 2/3 infratentorial usually from floor of the 4thventricle, sometimes only in CPA cistern.


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Ependymoma

Case 7CSF-like mass insinuates cisterns, encases

/ l !!!


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nerves/vessels!!!Lobulated, irregular, "cauliflower-like" masswith "fronds!!!

E id id


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Epidermoid

Intracranial

h t i


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hypotension

R f


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References Sectional anatomy for imaging professionals;

Clinically oriented anatomy;

StatDx;

http://radiopaedia.org/;

http://www.info-radiologie.ch/mri_sagittal_brain_t1.php#lsm1_1


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THANK YOU FOR YOURATTENTION!!!Imaging thanks:

Dr. Eugene YuDr. Kieran Murphy

brain presentation

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