Localization of Brain
Stem Lesions
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Anatomy of the Brain Stem
Part of the brain that extends from:
The rostral plane of the Superior Colliculus
To the caudal end of the Medulla Oblongata at the Foramen Magnum
Contains Structures:
 Midbrain

Pons

Medulla Oblongata
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

Brain Stem anterior view
1. Optic chiasm
2. Optic nerve
3. Optic tract
4. Medial sulcus of the crus cerebri
5. Oculomotor nerve
6. Pons
7. Pyramidal eminence of the pons
8. Retroolivary fossa
9. Oliva
10. Posterolateral sulcus
11. Decusssation of the pyramids
12. Anterolateral sulcus
13. Lateral funiculus
14. Pyramid
15. Foramen caecum
16. Middle cerebellar pedunculus
17. Trigeminal nerve
18. Crus cerebri
19. Interpeduncular fossa,
posterior perforate substance
20. Mammillary body
21. Tuber cinereum
22. Infundibulum
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
Posterior view of the brain stem
1.Pineal gland
2.Thalamus ( Pulvinar )
3.Superior colliculus
4.Inferior colliculus
5.Lemniscal trigone
6.Frenulum veli
7.Superior medullary velum
8.Median sulcus
9.Gracile tubercle
10.Cuneate tubercle
11.Posterior intermediate sulcus
12.Posteromedian sulcus
13.Vagal trigone
14.Hypoglossal trigone
15.Striae medullares
16.Facial colliculus
17.Locus coeruleus
18.Parabrachial recess
19.Crus cerebri
20.Inferior collicular brachium
21.Medial geniculate body
22.Lateral geniculate body
23.Suoerior collicular brachium
24.Habenula
25.Habenular commissure
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
Brain Stem lateral view
1. Medial geniculate body
2. Inferior collicular brachium
3. Superior colliculus
4. Inferior colliculus
5. Superior cerebellar peduncle
6. Rhomboid Fossa
7. Gracile fascicle
8. Cuneate fascicle
9. Lateral funiculus
10. Pyramid
11. Posterolateral sulcus
12. Oliva
13. Retroolivary fossa
14. Bulbopontine sulcus
15. Pons
16. Trigeminal nerve
17. Lateral sulcus of the crus cerebri
18. Pontomesencephalic sulcus
19. Crus cerebri
20. Optic nerve
21. Optic tract
22. Lateral geniculate body
23. Leminiscal trigone
24. Middle cerebellar peduncle
25. Inferior cerebellar peduncle
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
Medulla Oblongata (Myelencephalon)


Most caudal Portion of the brainstem
Extends from
The Rostral border of the Pons
Rostral to the emergence of the first spinal roots
Join with the spinal cord at the Foramen Magnum
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Vascular supply
Barainstems large regional arteries
Has three types of branches



Para median branches:
supplying midline structures
Short circumferential:
supply ventrolateral & lateral surface
Long circumferential:
Supply posterior structures & Cerebellum
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
Brain stem arteries - anterior view

1. Posterior cerebral artery
2. Superior cerebellar artery
3. Pontine branches of the basilar artery
4. Anterior inferior cerebellar artery
5. Internal auditory artery
6. Vertebral artery
7. Posterior inferior cerebellar a.
8. Anterior spinal artery
9. Basilar artery
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Para median Bulbar
branches (Para median
portion)

Vertebral artery and
Anterior spinal artery
1.
Hypoglossal Nucleus
2.
Medial longitudinal
fascicules
3.
The pyramids
4.
Inferior Olivary Nucleus
(medial part)
Lateral bulbar branches
(Lateral portion)
 Intracranial vertebral
artery fourth segment or
the Posterior inferior
Cerebellar artery
 Occasionally the basilar
artery or the anterior
Inferior Cerebellar artery
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Medullary syndromes
Medial Medullary Syndrome
Cause:1. Occlusion of ( vertebral a.), (anterior spinal a.),
(basilar a. lower segment)
2.Vertebrobasilar dissection
3.Dolichoectasia of the vertebrobasilar system
4. Embolism and meningovascular syphilis
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Anterior Spinal a. occlusion (Slide 7)

Ipsilateral pyramid, medial lemniscus, hypoglossal nerve
Clinical Picture:
1.
Ipsilateral paresis, atrophy and fibrallation of the tongue
the protruded tongue deviates toward the lesion(HN) (away
from the hemiplegia
2.
Contra lateral hemiplegia (Py) (face is spared)
3.
Contra lateral loss of position and vibration sense (ML)
Pain and temperature spared spinothalamic tract is not
affected
4.
Occasional upbeat nystagmus (MLF involvement )
Bilateral involvemnt gives
1.
Quadriparesis
2.
Bilateral LMN lesion of the tongue
3.
Complete loss position and vibration sense
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Occasionally:
1.
2.
3.
4.
HN can be spared In Anterior spinal artery occlusion.
Only the pyramids can be damaged giving Pure motor hemiplegia
Central facial paresis Corticobulbar fibers descend ipsilaterally before
crossing to the facial nucelus of the other side.
Crossed motor hemiparesis Lesions of lower medulla of the crossed
fibers of the arm and uncrosseds fibers of to the leg.
Lateral Medulllary Syndrome( Wallenberg)
Intracranial vertebral artery or posterior inferior cerebellar artery occlusion
Causes:
1.
Spontaneous discection of the vertebral artery
2.
Medullary neoplasms Usually metastasis
3.
Cocaine abuse
4.
Abscess
5.
Demyelinating disease
6.
Radionecrosis, Hematoma, trauma, neck manipulations
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Characteristic Clinical Picture are:
Results of wedge shaped damage to the lateral medulla
Ipsilateral facial hypalgesia & thermoanestesia (Trigeminal spinal
n.and tract) Ipsilateral facial pain
2.
Contra lateral trunk & extremity hypalgesia & thermoanesthesial (due
to Spinothalmic tract)
3.
Ipsilatral palatal pharyngeal and vocal cord paralysis wit dysphagia
and dysarthria (Nucleus Ambiguus)
4.
Ipsilatral Horners syndrome (Descending sympathetic fibers)
5.
Vertigo, nausea, and vomiting (Vestibular nuclei)
6.
Ipsilateral Cerebellar signs (Inferior cerebellar peduncle and
cerebellum)
7.
Occasionally Hiccups (Medullary respiratory centers) Diplopia (Lower
Pons)
Rostral medulla( Severe dysphagia, Hoarsness of voice , Facial paresis)
Caudal medulla (Marked vertigo, nystagmus, gait ataxia)09
1.
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Rare manifestatios of Wallenberg’s Syndrome:
1.
Wild arm ataxia ( Lateral Cuneate n.)
2.
Ipsilateral limb cllumsiness ( Subolivary area)
3.
Central pain associated with allodynia
4.
Contralateral hyperhydrosis with ipsilatral anhydrosis
5.
Inability to sneeze ( Spinal n.of trigeminal N.)
6.
Loss of taste (N.Tractus Solitarius) lateral zone
7.
Autonomic dysfunction ( N.Tractus Solitarius Medial caudal zone)
8.
Failure of Automatic breating( n. Ambigiuus adjecent Reticular Formation)
Ocular motor abnormalities:
1.
Dysfunction of ocular alignment ( Otolithic vestibular n. damage) Elevation of
the contralateral eye with out vertical displacement of the ipsilatral eye.
Rssulting in diplopia, head tilt , environmental tilt
2.
Torsional nystagmus
3.
Nystagmus
4.
Smooth pursuit and gaze holding abnormality( Cerebe;ar
FlloculusParaaflloculusassoing through the inferior peduncle.
5.
Lateropulsion or ipsupulsion
6.
Abnormalities of saccades (Cerebellum –Amplitudes control not speed ) patients
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have contralateral hypometra and ipsilateral hypermetra
Other lesions
1.
2.
3.
4.
5.
6.
Isolated vertigo with ipsilatral lateropulsion of the trunk
(Medial branch of PICA)
Bilateral cerebellar infarction (PICA) Vertigo, Nystagmus
Retropullsion,ataxia,upsidedown vision)
Babinski-Nageotte syndrome (Hemimedullary syndrome)
L+M syndrome Intracranial vertebral a.
Tegmeental medullary lesion –Medullary satiety
Opalski syndrome LM synd. Ipsilateral hemiplegia Lower
med. Lesion f corticospinal tract after pramidal decusation
Lateral pontomedullary syndrome LM synd. + Pontine
findigs (Vll +VIII nerves smptoms
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THE PONS

Anatomy of the Pons
Part of metencephalon
Extending caudal plane of striae medullaris posteriorly
To pontomedullar sulcus anteriorly
Inferrior colliculus dorsally and cerebellar peduncles ventrally
Dorsal part referred as Tegmentum
Ventral part as Basis pontis or Ponto cerebellar portion
Contains Cranial Nerve nuclei,Fiber tracts
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Vascular supply
Paramedian Vessels 4-6 in number
arising from the Basilar a.
supply –Medial basal pons,
pontine nuclei
cortico spinal
fibers
medial leminiscus
Short circumferential a.
arise from Basilar a. enter the
brachium pontis supply
Ventrolateral basis pontis
Long circumferential
Superior cerebellar a..
Arise from Basilar a.
Suply : the dorsolateral pons
Brachium pontis
Dorsal Retiular formation
Periaquidctal region
Ventrolateral pontine tegmentum
occasionaliy
Anterior inferior cerebellar a. arise
mostly from the basilar a.
supply: lateral tegmentum of
the lower two thirds of the
pons
Ventrolateral cerebellum
Internal auditory a. arise from
Basilar a.
Supply: Auditory ,Facial , vestibular
Ns
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Pontine Syndromes
Ventral pontine syndrome

(Millard –Gubler syndrome)

Lesion of the ventrocaudal pons

Involves basis pontis

And fascicles of cranial nerves
Vll,Vl
1.
2.
3.
Contralateral hemiplegia
(Pyramidal tract)
Ipsiaeral lateral rectus paresis
wit diplopia
Ipsilateral peripheral facial
paresis





1.
2.
Raymond syndrome
Lesion of the ventromedial
pons
Affects ipsilaterl Vl N
Corticospinal tract
Spares Vll N.
Ipsilateral rectus paresis
Contralateral hemiplegia
sparing the face (Pyramidal
tract)
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Pure Motor Hemiparesis
 Lacunar infarcts in the basis
pontis

Involving the corticospinal tract

Motor hemiparesis without facial
involvement
Other lesions that can give similar
findings:
internal capsule (Po. Limb)
Cerebral peduncle
Medullary pyramid
Vertigo ,dysartira, & gait
abnormality favor pontine
lesions
Dysarthria-Clumsy hand syndrome

Vascular leions in the basis
pontis

At the junction of the upper one
third and the lower two thirds

Usually lacunar lesions
Facial weakness
Severe dysarthria
Dysphagia
Clumsiness and paresis of the hand
Similar findings in:
Genu of the internal capsule
Deep cerebellar hemorhage
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Ataxic Hemipresis

Lesions basis pontis (U1/3 +L2/3)

Lacunar lesions mostly

Homolateral ataxia & crural
paresis

More severe in the lower limb

Occasional :Dysarthria,
nystagmus, paresthesia
Similar findings in:
Thalamocapsular lesions
Contralat. post.limb. of int.
capsule
Contralat. Red nucleus
Superficial infarcts in the territory
of superficial ant.cerebral a.
Para central area
Locked in syndrome

Bilateral ventral pontine lesion

Due to: Infarction. Tumor.
Trauma. Haemorrhage. Central
pontine myelinolysis
1.
Quadriplegia Cort.Sp. Lesions
bilat.
2.
Aphasia involvement of
Cort.Bul. Fibers the lower
cranial nerve n.
3.
Occ. Involvement of Vll N
fascicles
Patient is fully awake NO damage
to the Reticular Formation or
supranuclear oculomotoor
pathway
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Dorsal Pontine Syndrome
Foville sndrome

Involves dorsa pontine
tegmentum

In the caudal third of the pons

It consists of:
1.
Contralateral hemiplegia due
to corticospinal tract invovment
2.
Ipsilateral facial palsy Vll N
3.
Inabality to move te eye
conjugately to ipsilateral side
due to Vl N. or paramedian
pontine Reticular formation



1.
2.
3.
Raymond-Cestan-Chenais
syndrome
Rostral lesion of the dorsal
pons
It consists of :
Cerbellar signs Ataxia it coarse
Rubral tremors
Contralatral sensory modalities
are reduced ( medial lemniscus
& spinothalamic tract)
Ventral extension –
contralateral hemiparesis
(corticospinal tract)
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Paramedian Pontine syndrome
Several clinical syndromes exist
1.
Unilateral mediobasal infarcts
wit Facio-bracio-crual
hemiparesis Dysarthria &and
homolateral or bilateral ataxia
2.
Unilateral mediolatral basal
infarcts: ataxia dysarthria
slight hemiparesis , ataxic
hemiparesis or clumsy hand
dysarthria syndrome
Unilateral mediocentral or
mediotegmental infarcts
Clumsy hand –dysarthria syndrome
Ataxic hemiparesis
Without sensory or eye mov’t disoders
hemiparesis with contralateral
facial or abducens palsy
4.
Bilateral centrobasal infarcts
Pseudobulbar palsy & bilateral
sensorimotor disturbance
Common causes are Small vessel
disease, vertebrobasilar large
vessel disease & Cardiac
embolism less commmonly
3
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Lateral Pontine syndrome

Marie_Foix Syndrome

Lesions affecting the brachium pontis
Isilatral cerebelar ataxia ( celebellar connections)
Contralatral hemiparesis ( corticospinal tracts)
Contralatral hemianesthesia for pain and tempature
( spinothalamic tracts)



Others
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The mesencephalon
Anatomy of the mesencephalon
Rostrally Superior Colliculus-Mamillary body plane

Caudally the plane just caudal to the Inferior Colliculus

Divided in to:
dorsal Tectum
the tegmentum and
the cerebral peduncle
Contains ascending and descending tracts reticular nuclei and well delinated
nuclear mases

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Vascular supply of the Mecencephalon
Includes Paramedian and Circumferential vessels

Paramedian vessels
Arise from the origins of the Posterior Cerebral a.
1.
Thalamoperforating (supplying the thalmus
2.
Pedunclar ( supplying the media peduncle) (Midbrain tegmentum
including Oculomotor n. the Red n. & SN)
Circumferential a.
Circumferential perpendicular aa.
1.
Quadrigemnial aa.(from PCA supply Sup. & Inf. Colliculi)
2.
Superior cerebellar aa. (Supply Cerebral pedunclesBrachium
conjunctivum, superior cerebelum)
3.
Posterior chroidal aa. (supply Cereberal Peduncle lat.sup. Colliculi,
Thalamus,Choroid Plexus of the third ventricle)
4.
Anterior Choroidal aa.( From Int. Carotid or MCA) Cerebrl peduncle &
supramecencephalic structure
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5.
Posterior Cerebral aa ( Gives branch to Mecencephalic vesels)

Mesencephalic Syndromes
Ventral Cranial Nerve lll
Fascicular Syndrome (Weber)

Lesion Cerebral Peduncle esp.
medial peduncle

May damage pyramidal fibers

Fascicle of third nerve
Consists of:

Contralateral Hemiplegia
including te lower face(CoS
CoB)

Ipsilateral oculomotor paresis +
parasymp. Cranial N. /// (Dilated
pupil)

Dorsal Cranial N /// faciclular
syndrome(Benedikt)

Lesion affecting the tegmentum

May affect Brachium conj., Red
n.

Cranial N. ///
Consists of:

Ipsilateral oculomotor paredis
wit dilated pupil

Contralatera Involuntary mov’t
like intention temor ,hemichorea,
hemiatetosis (Destruction Red n.)

Dorsal Red n lesions =
Brachium conj. Can give similar
findings (Claude synd.)

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Dorsal Mesencephalic syndromes

Mainly neuroophthalmologic
abnormalities

(Sylvian aqueduct synd.
Parinaud synd.)

Commonly seen in:
Hydrocephalus
Tumors of Pineal origin
Consists of :
1.
Paralysis of conj. Upward gaze
(downward occ.)
2.
Pupillary abnormality(
usu,Large
3.
Convergence retraction
Nystagmus o upward gaze
4.
Pathalogic lid
retractionCollier‘s sign
5.
Lid lag
6.
“Pseudo abducens palsy”
Top of the Basilar Syndrome

Oclusive vascular disease rostral
BA

Usually embolic

Giant aneurysms

Vasculits

Cerbral angiography
Gives infarction of:
mid brain thalamus portion of
temporal and occipital lobe

Consists of :
1.
Disorders of eye mov’t
2.
Pupillary abnormality
3.
Behavioral abnormality
4.
Visual field defects
5.
Motor and sensory deficits
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