POSTERIOR CIRCULATION

STROKEDR.SARATH CHANDRA CHERUKURI

1st year PG in general medicineKATURI MEDICAL COLLEGE

Stroke or CVA is defined as abrupt onset of neurologic deficit that is attributable to a focal vascular cause.

Stroke has occured if the neurologic signs and symptoms last for >24 hours

WHAT IS STROKE?

It is composed of the paired vertebral artery,basilar artery&paired PCA’s

These major arteries give rise to short&long circumferential branches that supply the cerebellum,medulla,pons,midbrain,thalamus,hippocampus and medial temporal&occipital lobes

PCA syndromes usually result from atheroma or emboli at the top of basilar artery,fibromuscular dysplasia or vertebral artery dissection

STROKE WITHIN POSTERIOR CIRCULATION:

TERRITORY OF PCA:

TERRITORY OF PCA:

P1 SYNDROME:infarction usually occurs in the I/L subthalamus&medial thalamus and in I/L cerebral peduncle&midbrain

P2 SYNDROME:Cortical temporal and occipital lobe signs

SYNDROMES IN OCCLUSION OF PCA:

The VERTEBRAL artery has 4 segments V1,V2,V3&V4

The fourth segment courses upward to join the other vertebral artery to form the basilar artery

Only V4 gives rise to branches that supply the brainstem&cerebellum

The PICA,in its proximal segment supplies the lateral medulla and in its distal branches the inferior surface of cerebellum

BLOOD SUPPLY OF MEDULLA:

MEDULLARY SYNDROMES:

ON SIDE OF LESION:1) Pain,numbness,impaired sensation over

one-half of face:5th nerve nucleus2) Ataxia:restiform body,cerebellar

hemisphere,spinocerebellar tract3) Nystagmus,diplopia,vertigo,nausea,vomtin

g:vestibular nucleus4) Horner’s syndrome:descending

sympathetic tract5) Dysphagia,paralysis of palate,vocal

cord,diminished gag reflex:fibres of 9th&10th nerves

LATERAL MEDULLARY SYNDROME:

6)Loss of taste:nucleus&tractus solitarius

7)Numbness of I/L arm,trunk&leg: cuneate&gracile nucleus

8)Weakness of lower face:UMN fibres to I/L facial nucleus

ON SIDE OPPOSITE LESION:

1) Impaired pain&thermal sense over half the body,sometimes face:Spinothalamic tract

On the side of lesion:1) Paralysis with atrophy of half the tongue:

I/L 12th nerve

On the side opposite lesion:

1) Paralysis of arm&leg sparing face;impaired tactile&proprioceptive sense over one half of the body:C/L pyramidal tract&medial leminiscus

MEDIAL MEDULLARY OR DEJERINE SYNDROME:

Branches of basilar artery supply the base of the pons&superior cerebellum and fall into 3 groups:

1) Paramedian,7-10 in number supply a wedge of pons on either side of midline

2) Short circumferential,5-7 that supply lateral two-thirds of pons&middle,superior cerebellar peduncle

3) B/L long circumferential(SCA&AICA) course around pons to supply the cerebellar hemispheres

BLOOD SUPPLY OF PONS:

INFERIOR PONTINE SYNDROMES:

MEDIAL INFERIOR PONTINE SYNDROME: ON THE SAME SIDE:1) Paralysis of conjugate gaze to the side of

lesion2) Nystagmus:vestibular nucleus3) Ataxia:middle cerebellar peduncle4) Diplopia on lateral gaze:abducens nerve

ON THE OPPOSITE SIDE:1) Paralysis of face,arm&leg:CB&CS tracts2) Impaired tactile&proproiceptive sense

over one-half of body:medial leminiscus

LATERAL INFERIOR PONTINE (AICA) SYNDROME:

ON THE SIDE OF LESION:1) Horizontal&vertical gaze

nystagmus,vertigo,nausea,vomting:vestibular nerve or nucleus

2) Facial paralysis:7th nerve3) Ataxia:middle cerebellar

peduncle&cerebellar hemisphere4) Impaired sensation over face:descending

tract&5th nucleus ON THE SIDE OPPOSITE LESION:1) Impaired pain and thermal sense over

one-half of body

MIDPONTINE SYNDROMES:

ON THE SIDE OF LESION:

1) Ataxia of limbs and gait-pontine nucleii

ON THE SIDE OPPOSITE LESION:

1) Paralysis of face,arm&leg:corticobulbar and corticospinal tracts

2) Variable impaired touch and proprioception:medial leminiscus

MEDIAL MIDPONTINE SYNDROME:

ON THE SIDE OF LESION:

1) Ataxia:middle cerebellar peduncle Paralysis of muscles of mastication:motor

fibres or nucleus of 5th nerve

ON THE SIDE OPPOSITE LESION:

1) Impaired pain and thermal sense on limbs and trunk:spinothalamic tract

LATERAL MIDPONTINE SYNDROME:

SUPERIOR PONTINE SYNDROME:

MEDIAL SUPERIOR PONTINE SYNDROME:

ON THE SIDE OF LESION:1) Cerebellar ataxia:superior/middle

cerebellar peduncle2) Internuclear ophthalmoplegia:MLF3) Myoclonic syndrome,palate,pharynx,vocal

cords-dentate projection,inferior olivary nucleus

ON THE SIDE OPPOSITE LESION:1) Paralysis of face,arm&leg:CB&CS tract2) Rarely touch,vibration&position:medial

leminiscus

LATERAL SUPERIOR PONTINE SYNDROME OR SCA OR MILLS’ SYNDROME:

ON SIDE OF LESION:1) Ataxia:middle&superior cerebellar

peduncles,dentate nucleus2) Dizziness,nausea,horizontal

nystagmus:Vestibular nucleus3) Horner’s syndrome:descending sympathetic

tract4) Tremor:red nucleus,superior cerebellar

peduncle

ON SIDE OPPOSITE LESION:

1) Impaired pain&thermal sense on face,limbs&trunk:spinothalamic tract

2) Impaired touch,vibration&position sense:medial leminiscus

MILLARD-GUBLER SYNDROME:I/L LMN type facial nerve palsy&C/L hemiparesis due to involvement of 7th nerve nucleus&CST

FOVILLE’S SYNDROME:I/L LMN type facial nerve palsy&horizontal gaze palsy with C/L hemiparesis due to involvement of horizontal gaze centre,7th nerve nucleus&CST

RAYMOND’S SYNDROME:I/L abducens palsy C/L hemiparesis due to involvement of 6th cranial nerve&CST

CLASSICAL PONTINE SYNDROMES:

MIDBRAIN SYNDROMES:

MEDIAL MIDBRAIN SYNDROME:1) ON THE SIDE OF LESION:Eye”down&out”

secondary to unopposed action of 4th&6th cranial nerves,with dilated&unresponsive pupil(3rd cranial nerve)

2) ON SIDE OPPOSITE LESION:paralysis of face,arm,leg(CB&CS tracts in crus cerebri)

LATERAL MIDBRAIN SYNDROME:1) ON THE SIDE OF LESION:eye down&out2) ON THE OPP. SIDE:

hemiataxia,hyperkinesias,tremor:Red nucleus,dentatorubrothalamic pathway

WEBER’S syndrome:third nerve palsy on the I/L side due to involvement of occulomotor nerve fascicles,Hemiplegia on C/L side due to superior cerebral peduncle involvement

CLAUDE’S syndrome:I/L 3rd nerve palsy,C/L ataxia&tremor due superior cerebellar peduncle involvement

BENEDIKT’S syndrome:3rd nerve palsy on I/L side&C/L side hemiparesis&ataxia due involvement of red nucleus,SCP

CLASSICAL MIDBRAIN SYNDROMES:

Lesion is dorsal midbrain Structures involved are quadrigeminal plate

region,periaqeuductal gray matter Clinical findings: impaired upgaze;

convergence&retraction nystagmus

NOTHNAGEL’S SYNDROME:it is more a variant of parinaud’s with U/L or B/L 3rd nerve palsy.lesion is in midbrain tectum

PARINAUD’S SYNDROME:

C/L homonymous hemianopia with visual sparing is the usual manifestation

ACUTE MEMORY DISTURBANCES:due to medial temporal lobe&hippocampus involvement on the dominant side

ALEXIA without agraphia:due to dominant hemisphere plus splenium of corpus callosum involvement

PEDUNCULAR HALLUCINOSIS:due to occlusion of PCA

P2 SYNDROME:

ANTON’S syndrome:B/L infarction in distal PCA produces cortical blindness

If the visual association areas are spared and only calcarine cortex is involved,patient may be aware of his blindness

BALINT’S syndrome:disorder of orderly visual scanning of the environment due to bilateral visual association area lesions,resulting from infarctions secondary to low flow in the watershed areas between the distal PCA&MCA territories

Pallinopsia&asimultognosia may also be seen

THANK YOU