BRAINSTEM STROKE SYNDROMES

Discussion will contain

• Basic neuro-anatomy of the brainstem from a clinician’s perspective

• Details of the blood supply of the brainstem• Various syndromes caused by stroke involving the

brainstem vessels

• RULE OF FOUR = a very simple way to remember various brainstem lesions.

• Clinical case examples

Located between the cerebrum and the spinal cord Provides a pathway for tracts running between higher and lower neural centers.

Consists of the midbrain, pons, and medulla oblongata.

Brainstem

Midbrain

Pons

Medullaobongata

Midbrain

Pons

Medullaoblongata

Ventral surface of brain stem

MidbrainCerebral peduncles

PonsBasis pontis

Medulla

Ventral – Lateral View

Posterior circulationVertebral artery branches 

Posterior inferior cerebellar Medulla, lower cerebellum

Basilar artery branches 

Anterior inferior cerebellar Lower and middle pons, anterior cerebellum

Superior cerebellar Upper pons, lower midbrain, upper cerebellum

Posterior cerebral Medial occipital and temporal cortex and subjacent white matter, posterior corpus callosum, upper midbrain

Thalamoperforate branches Thalamus

Thalamogeniculate branches Thalamus

8

• Brain stem arteries - anterior view 1. Posterior cerebral artery2. Superior cerebellar artery3. Pontine branches of the basilar artery4. Anterior inferior cerebellar artery5. Internal auditory artery6. Vertebral artery7. Posterior inferior cerebellar a.8. Anterior spinal artery

• 9. Basilar artery

MID-BRAIN STOKE SYNDROMES

Midbrain

Shortest brain stem,not more than2cm in length,lies in the posterior cranial Fossa.For descriptive purpose,divided intoDorsal tectum and right and left cerebralPeduncles.Each cerebral peduncles divide furtherinto ventral crus cerebri and a dorsalTegmentum by a pigmented lamina“ Substantia nigra”

Cerebral peduncles contains:-Descending fibers that go to the cerebellum via the pons-Descending pyramidal tracts

Running through the midbrain is the hollow cerebral aqueduct which connects the 3rd and 4th ventricles of the brain.

MidbrainCrus cerebri

Basis pedunculiSubstantia nigra

Crus cerebri(cerebral peduncle)

Cerebral aqueduct

Basis Tegmentum

Tectum

Ventral – Dorsal Organization

The roof of the aqueduct ( the tectum) contains the corpora quadrigemina

2 superior colliculi that control reflex movements of the eyes, head and neck in response to visual stimuli2 inferior colliculi that control reflex movements of the head, neck, and trunk in response to auditory stimuli

Corpora quadregemina

Superior colliculi larger and darker than inferior colliculi,the difference In colour due to superficial neurons inSuperior colliculi

Superior and inferior colliculi seperated by cruciform sulcus

Superior colliculi

Inferior colliculi

Internal structure Transverse section of midbrainCommon to both at inferior and superior colliculus:Crus cerebri (or basis pedunculi): - Consists of fibres descending from cerebral cortex. - Its medial one-sixth is occupied by coticopontine fibres from frontal lobe,lateral one-sixth fibres from temporal,occipital and parietal lobes,the intermediate two third by corticospinal and cortico- nuclear fibres.

Substantia nigra : - Present immediately behind and medial to basis pedunculi. - It appears dark as neuron within it contain pigment. ( neuromelanin )

Medial midbrain syndrome (paramedian branches of upper basilar and proximal posterior cerebral arteries)

• ON SIDE OF LESION Eye "down and out"

secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers

ON OPPOSITE SIDE• Paralysis of face, arm, and

leg: Corticobulbar and corticospinal tract descending in crus cerebri

Lateral midbrain syndrome (syndrome of small penetrating arteries arising from posterior cerebral artery)

On side of lesion• Eye "down and out"

secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers and/or third nerve nucleus

On side opposite lesion• Hemiataxia, hyperkinesias,

tremor: Red nucleus, dentatorubrothalamic pathway

Mid brain syndromes

Medial midbrain syndrome (paramedian branches of upper basilar and proximal posterior cerebral arteries)

• ON SIDE OF LESION Eye "down and out"

secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers

ON OPPOSITE SIDE• Paralysis of face, arm, and

leg: Corticobulbar and corticospinal tract descending in crus cerebri

Pontine syndromes

Pons

Pons

The pons shows a convex anterior surface with prominent transversely running fibres. These fibres collect to form bundles,the middle cerebellar peduncles.

The anterior surface of pons is marked in the midline by a shallow groove,the sulcus basilaris which lodges the basilar artery.

Pons

s

Sulcus basilaris

Subdivided into ventral and dorsal part

Ventral part of the pons contains

Pontine nuclei:•Recieves corticopontine fibres from frontal, temporal,parietal and occipital lobes of cerebrum•The efferent fibres form the transverse fibres of pons.

Vertically running corticospinal and corticopontine fibres.

Transversely running fibres arising in pontine nuclei

Pontine nuclei

The dorsal part of the pons may be regarded as continuation of the part of the medulla behind the pyramids.

Superiorly continous with the tegmentum of the midbrain.

Occupied predominately by reticular formation

Posterior surface help to form floor of fourth ventricle

The dorsal part is bounded laterally by inferior cerebellar peduncle in the lower part of the pons and superior cerebellar peduncle in upper part.

Dorsal part of pons

DORSAL PART

Midpons

Upper pons

Medial inferior pontine syndrome (occlusion of paramedian branch of basilar artery)

On side of lesion• Paralysis of conjugate gaze to side

of lesion (preservation of convergence): Center for conjugate lateral gaze(PPRF)

• Nystagmus: Vestibular nucleus• Ataxia of limbs and gait: Likely

middle cerebellar peduncle• Diplopia on lateral gaze:

Abducens nerveOn side opposite lesion• Paralysis of face, arm, and leg:

Corticobulbar and corticospinal tract in lower pons

• Impaired tactile and proprioceptive sense over one-half of the body: Medial lemniscus

Lateral inferior pontine syndrome (occlusion of anterior inferior cerebellar artery)

• On side of lesion• Horizontal and vertical nystagmus, vertigo,

nausea, vomiting, oscillopsia: Vestibular nerve or nucleus

• Facial paralysis: Seventh nerve• Paralysis of conjugate gaze to side of lesion:

Center for conjugate lateral gaze• Deafness, tinnitus: Auditory nerve or

cochlear nucleus• Ataxia: Middle cerebellar peduncle and

cerebellar hemisphere• Impaired sensation over face: Descending

tract and nucleus fifth nerve

• On side opposite lesion• Impaired pain and thermal sense over one-

half the body (may include face): Spinothalamic tract

Medial midpontine syndrome (paramedian branch of midbasilar artery)

• On side of lesion• Ataxia of limbs and gait (more

prominent in bilateral involvement): Pontine nuclei

• On side opposite lesion• Paralysis of face, arm, and

leg: Corticobulbar and corticospinal tract

• Variable impaired touch and proprioception when lesion extends posteriorly: Medial lemniscus

Lateral midpontine syndrome (short circumferential artery)

On side of lesion• Ataxia of limbs: Middle

cerebellar peduncle• Paralysis of muscles of

mastication: Motor fibers or nucleus of fifth nerve

• Impaired sensation over side of face: Sensory fibers or nucleus of fifth nerve

On side opposite lesion• Impaired pain and thermal

sense on limbs and trunk: Spinothalamic tract

Medial superior pontine syndrome (paramedian branches of upper basilar artery)

On side of lesion• Cerebellar ataxia (probably):

Superior and/or middle cerebellar peduncle

• Internuclear ophthalmoplegia: Medial longitudinal fasciculus

• Myoclonic syndrome, of palate, pharynx, vocal cords, respiratory apparatus, face, oculomotor apparatus, etc.: —central tegmental bundle.

On side opposite lesion• Paralysis of face, arm, and leg:

Corticobulbar and corticospinal tract

• Rarely touch, vibration, and position are affected(arm>leg): Medial lemniscus

Rt internuclear ophthalmoplegia

One and a half syndromeRT LT

Lateral superior pontine syndrome (syndrome of superior cerebellar artery)

On side of lesion• Ataxia of limbs and gait, falling to side of

lesion: Middle and superior cerebellar peduncles, superior surface of cerebellum, dentate nucleus

• Dizziness, nausea, vomiting; horizontal nystagmus: Vestibular nucleus

• Paresis of conjugate gaze (ipsilateral): Pontine contralateral gaze

• Miosis, ptosis, decreased sweating over face (Horner's syndrome): Descending sympathetic fibers

On side opposite lesion• Impaired pain and thermal sense on face,

limbs, and trunk: Spinothalamic tract• Impaired touch, vibration, and position

sense, more in leg than arm : Medial lemniscus (lateral portion)

MEDULLA OBLONGATA

Medulla is broad above ,joins with pons narrow below, continous with spinal cord

Length is about 3cm, width is about 2cm at its upper end

Surfaces shows series of fissuresAnterior median fissurePosterior median fissure

Medulla oblongata

Most inferior region of the brain stem.

Becomes the spinal cord at the level of the foramen magnum.

External structure of medulla

Ventral surface of medulla oblongata containsPyramid•elevation between anterior median and anterolateral sulcus•Formed due to decussation of corticospinal fibres.

Pyramid

Olive

Olive •Oval swelling between anterolateral posterolateral sulcus,half an inch long•Produced by large mass of gray matter called inferior olivary nucleus

External surface of medulla

Anterior median fissure

Pyramid

Anterolateral fissure

Olive

Medial medullary syndrome (occlusion of vertebral artery or of branch of vertebral or lower basilar artery)

On side of lesion• Paralysis with atrophy of

one-half half the tongue: Ipsilateral twelfth nerve

On side opposite lesion• Paralysis of arm and leg,

sparing face; impaired tactile and proprioceptive sense over one-half the body: Contralateral pyramidal tract and medial lemniscus

Lateral medullary syndrome (occlusion of any of five vessels may be responsible—vertebral, posterior inferior cerebellar, superior, middle, or inferior lateral medullary arteries)

On side of lesion• Pain, numbness, impaired sensation over one-

half the face: Descending tract and nucleus fifth nerve

• Ataxia of limbs, falling to side of lesion: Uncertain—restiform body, cerebellar hemisphere, cerebellar fibers, spinocerebellar tract (?)

• Nystagmus, diplopia, oscillopsia, vertigo, nausea, vomiting: Vestibular nucleus

• Horner's syndrome (miosis, ptosis, decreased sweating): Descending sympathetic tract

• Dysphagia, hoarseness, paralysis of palate, paralysis of vocal cord, diminished gag reflex: Issuing fibers ninth and tenth nerves

• Loss of taste: Nucleus and tractus solitarius• Numbness of ipsilateral arm, trunk, or leg:

Cuneate and gracile nuclei• Weakness of lower face: Genuflected upper

motor neuron fibers to ipsilateral facial nucleus

On side opposite lesion• Impaired pain and thermal sense over half the

body, sometimes face: Spinothalamic tract