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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