Posterior circulation stroke syndromes

Differentiating features between anterior and posterior circulation stroke

Clinical features Posterior circulation Anterior circulation

A.History

1.Vertigo Present Absent

2.Unsteadiness Present Absent

B.Physical findings

1.Crossed hemiplegia Present Absent

2.Bilateral deficits Present Absent

3.Cerebellar signs Present Absent

4.Ocular findings(LMN/INO/Gaze deviation to paralysed side) Present Absent

5.Dissociated sensory loss Present Absent

6.Sensory loss over V1 and V2 Present Absent

7.Horners syndrome Present Absent

ANATOMY

• Comprises of:

(Tracing from Below Upwards of VertebroBasilar System)

1) Paired vertebral arteries2) Basilar artery3) Paired posterior cerebral arteries

• Vertebrals join to form basilar at the pontomedullary junction• Basilar divides into two posterior cerebrals in the interpeduncular fossa.• These 3 give rise to long & short circumferential branches and to

smaller deep penetrating branches.• Supply: Cerebellum, Medulla, Pons, midbrain, subthalamus, thalamus,

hippocampus and medial temporal & occipital lobes

POSTERIOR CIRCULATION

VERTEBROBASILAR SYSTEM - Branches• Vertebral Artery

• Anterior spinal artery

• Posterior spinal artery

• Posterior inferior cerebellar artery

• Basilar artery

• Superior cerebellar artery

• Pontine arteries

• Anterior inferior cerebellar artery

• Posterior cerebral artery

• Central - Thalamoperforate arteries &

Thalamogeniculate arteries

• Choroidal arteries

• Callosal

• Cortical branches

CIRCLE OF WILLIS – a note

CIRCLE OF WILLIS – a note

Posterior circulation

Lateral view

DISCUSSION

Posterior Cerebral Artery:- (PCA)

• Terminal branch of the basilar artery• Paired• At the interpeduncular fossa

• Branches:

• P 1 segment: Proximal PCA prior to junction of PCA with posterior communicating (=Precommunal segment)

• Penetrating branches of P1:Thalamogeneculate, Percheron, posterior choroidal)

• P 2 segment: Distal PCA (distal to junction of PCA and posterior communicating)

PCA

• 75% cases: from bifurcation of basilar artery

• 20% cases: One PCA arises from ipsilateral ICA via posterior communicating artery

• 5% cases: BOTH PCAs originate from respective ipsilateral ICAs. The P1 segment (precommunal) of the true PCA is atretic in such cases.

PCA - ORIGINS

• The artery of Percheron is a rare variant of the posterior cerebral circulation.

• The term is used to refer to a solitary arterial trunk that branches from one of the proximal segments of either posterior cerebral artery.

• It supplies blood to the paramedian thalami and the rostral midbrain bilaterally.

• Percheron infarct: bilateral thalamic and mesencephalic infarctions ; clinically, often obtunded, comatose, or agitated, with associated hemiplegia or hemisensory loss

PERCHERON???

• Supplies posterior cranial fossa structures:– Medial area of occipital lobe

– Inferior temporal lobe

– Midbrain

– Thalamus

• Lesion causes:– Visual agnosia

– Hemianopsia

– Alexia

– Loss of smell

POSTERIOR CEREBRAL ARTERY (PCA)

• Causes:– Atheroma/Emboli @ Basilar– Dissection @ Vertebral– Fibromuscular dysplasia

• Two syndromes– P 1 Syndrome– P 2 Syndrome

PCA Syndromes:

• Area infarcted:– Ipsilateral subthalamus– Medial thalamus– Ipsilateral cerebral peduncle– Midbrain

• Weber’s/Claude’s syndrome can occur

• Contralateral hemiballismus +/-

• Art. of Percheron occlusion: Upward gaze paresis, drowsiness, abulia

P 1 syndrome:

• B/L Prox PCA occlusion: Extensive infarction:– Coma, Unreactive pupils, b/l pyramidal signs, decerebrate rigidity

• Penetrating branches of thalamic and thalamogeniculate arteries if occluded:

– Less extensive syndromes

• Thalamic Dejerine-Roussy syndrome:– Contralateral hemisensory loss– Followed by agonising, searing, burning pain– Persistent, poor response to analgesics– Anticonvulsants (Carbamazepine, gabapentin) & TCAs used.

P 1 syndrome… contd:

• Infarction of:– Medial temporal and occipital lobes

• Contralateral homonymous hemianopia with macular sparing

• Occasional only the upper quadrant is involved.• Dominant medial temporal lobe and hippocampal

lesions: Acute disturbances in memory – usually recovers• Alexia without Agraphia• Visual agnosia• Amnestic aphasia• Peduncular hallucinosis

P 2 syndrome

• Anton’s blindness• Gun barrel vision• Balint’s syndrome• Palinopsia• Asimultanagnosia

• Embolic occulsion of top of basilar:– HALLMARK is sudden onset of bilateral signs, including ptosis,

pupillary asymmetry or lack of reaction to light, somnolence.

P 2 syndrome… contd:

MID BRAIN

Weber syndrome-occlusion of perforating branch of posterior cerebral

arteryClinical features

1.Ipsilateral

a.3rd nerve palsy

2.Contralateral

a.hemiplegia

Benedikt syndrome-occlusion of perforating branch of posterior cerebral

Clinical features

1.Ipsilateral

a.3rd nerve palsy

2.Contralateral

a.cerebellar ataxia

Thalamus-occlusion of thalamo geniculate branches of posterior

cerebral artery Contralateral

1.Sensory loss

2.Spontaneous pain

3.Choreo athetosis

4.Ataxic tremor

5.Mild hemiparesisTHALAMUS

Occipital lobe-optic pathway and visual reflexes

Occipital lobe-occlusion of left calcarine artery

Clinical features

1.Right Hemianopia

Occipital lobe-occlusion of both calcarine arteries

Clinical features

1.Bilateral hemianopia-

cortical blindness (light

reflex preserved)

Left occipital lobe with corpus callosum infarction

Left

Clinical features

1.Right hemianopia

2.Alexia without

agraphia

• Commences as the union of

both vertebral arteries

• Terminates by dividing into

two Posterior cerebral arteries.

• Branches:

– AICA

– Pontine arteries

– Superior cerebellar artery

– PCA

BASILAR ARTERY

• Three groups:– Paramedian, 7-10 in number, supply a wedge of pons on

either side of midline– Short circumferential, 5-7, supply lateral 2/3rd of Pons, middle

& superior cerebellar peduncles.– Bilateral long circumferentials (curve around pons to supply

cerebellum):• Superior cerebellar art• Anterior inferior cerebellar art

Basilar artery – Branches

Structures supplied by BASILAR

• Complete basilar occlusion– Constellation of bilateral long tract signs (sensory & motor)

with signs of cranial nerve & cerebellar dysfunction.

• “Locked-in” state:– Preserved consciousness with quadriplegia & cranial nerve

signs.

Basilar syndromes

Basilar artery occlusionClinical features

1.Paralysis of all four limbs2.Bulbar paralysis3.Eye movements abnormalities4.Nystagmus5.Coma

Note: The neurological deficit is variable depending upon the ischemia – modifying factors.

• Severe ipsilateral cerebellar ataxia• Nausea & vomitings• Dysarthria• Contralateral loss of pain & temperature over extremities,

body & face.• Partial deafness, ataxic tremor of ipsilateral UL, Horner’s

syndrome & Palatal myoclonus rare

Superior cerebellar artery occlusion

Pons-Lower

Medial pontine syndrome – occlusion of paramedian branch of basilar artery

A.IPSILATERAL

1.Gaze paresis

2.Cerebellar signs

B.CONTRALATERAL

1.Hemiparesis

2.Hemianaesthesia

Lateral pontine syndrome-occlusion of anterior inferior cerebellar artery

A.IPSILATERAL

1.LMN VIIth nerve palsy

2.Gaze palsy

3.Deafness,tinnitus

4.Cerebellar signs

B.CONTRALATERAL

1.Impairment of pain and temperature on the body

Vertebral artery

• Commences as a branch of the subclavian on left and brachiocephalic on right and terminates by joining to form the basilar artery

• Four parts:– V-1: Preforaminal- origin to entrance into C5 or C6 foramen– V-2: Foraminal- vertebral foramina C6 to C2– V-3: C2 to dura- passes through transverse foramen and

circles around the arch of the atlas to pierce the atlas at the formen magnum

– V-4: Intradural-courses upwards and joins other to form basilar. Gives branches that supply BS & cerebellum.

VERTEBRAL ARTERY

• Branches:– Anterior spinal artery– Posterior spinal artery– Posterior inferior cerebellar artery

VERTEBRAL… contd

• Largest branch of vertebral artery• One of the three major supplies of the cerebellum• Also supplies the lateral medulla• Wallenberg syndrome (=LMS)

PICA

• Posterior meningeal branch• Arises from opposite the formen magnum• Supplies Falx cerebri

MENINGEAL BRANCHES OF VERTEBRAL a.

• Predilection for V1 and V4• Usually lesion of one vertebral does not cause TIAs.• TIAs occur if one is atretic and other is developing

occlusion.• Symptoms:

– Syncope– Vertigo– Alternating hemiplegia– ‘Sets the stage for thrombosis’

• Stenosis proximal to origin of PICA can threaten lateral medulla & posterior inferior surface of cerebellum.

ATHEROTHROMBOTIC LESIONS – V1 & V4

• Atheromatous disease is rare.• Fibromuscular dysplasia, dissection common here• Rarely due to encroachment from osteophytic spurs

within vertebral foramina

LESIONS OF V2 & V3

• Subclavian occluded proximal to origin of vertebral.

• Leads of reversal in the direction of blood flow in the ipsilateral vertebral artery.

• Exercise of ipsilateral arm may increase demand on vertebral flow, leading to posterior circulation TIAs.

“SUBCLAVIAN STEAL”

Medulla

Lateral medullary syndrome(Wallenberg Syndrome – PICA occlusion)

A. IPSILATERAL1.Xth cranial nerve palsy2.Cerebellar signs3.Horner’s syndrome4.Impaired pain, temperature

and touch on the upper half of face

B. CONTRA LATERAL1.Impaired pain and

temperature over the body

Medial medullary syndrome – Anterior Spinal Artery occlusion

A.IPSILATERAL

1.XIIth nerve palsy

B.CONTRALATERAL

1.Hemiplegia – sparing the

face

2.Hemianaesthesia sparing the

face.

• Can lead to sudden respiratory arrest• Due to raised ICP in the posterior fossa• Symptoms:

– Drowsiness– Babinski signs– Dysarthria– Bifacial weakness maybe absent, or present only briefly,

before respiratory arrest ensues.– Gait unsteadiness, headache, dizziness, nausea and vomiting

maybe the only early symptoms and signs and should arouse suspicion.

• D/D: Viral labrynthitis (Headache, neck stiffness & unilateral dysmetria favor stroke)

CEREBELLAR INFARCTION

THANK YOU

Dr.Karthik RaghavanPostgraduate MD (Int. Med)SRM Medical College & Hospital