4. • Comprises of:
(Tracing from Below Upwards of VertebroBasilar System)
1) Paired vertebral arteries
2) Basilar artery
3) 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
25. 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
26. • 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
27. • 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???
28. • 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)
29. • Causes:
– Atheroma/Emboli @ Basilar
– Dissection @ Vertebral
– Fibromuscular dysplasia
• Two syndromes
– P 1 Syndrome
– P 2 Syndrome
PCA Syndromes:
30. • 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:
31. • 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:
32. • 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
33. • 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:
41. Occipital lobe-occlusion of both
calcarine arteries
Clinical features
1.Bilateral hemianopia-
cortical blindness (light
reflex preserved)
42.
43. Left occipital lobe with corpus
callosum infarction
Left
Clinical features
1.Right hemianopia
2.Alexia without
agraphia
44.
45. • 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
46. • 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
48. • 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
49. Basilar artery occlusion
Clinical features
1.Paralysis of all four limbs
2.Bulbar paralysis
3.Eye movements
abnormalities
4.Nystagmus
5.Coma
Note: The neurological
deficit is variable depending
upon the ischemia –
modifying factors.
50. • 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
52. Medial pontine syndrome – occlusion
of paramedian branch of basilar artery
A.IPSILATERAL
1.Gaze paresis
2.Cerebellar signs
B.CONTRALATERAL
1.Hemiparesis
2.Hemianaesthesia
53. 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
55. • 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
57. • Largest branch of vertebral artery
• One of the three major supplies of the cerebellum
• Also supplies the lateral medulla
• Wallenberg syndrome (=LMS)
PICA
58. • Posterior meningeal branch
• Arises from opposite the formen magnum
• Supplies Falx cerebri
MENINGEAL BRANCHES OF VERTEBRAL a.
59. • 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
60. • Atheromatous disease is rare.
• Fibromuscular dysplasia, dissection common here
• Rarely due to encroachment from osteophytic spurs
within vertebral foramina
LESIONS OF V2 & V3
61. • 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”
63. Lateral medullary syndrome
(Wallenberg Syndrome – PICA occlusion)
A. IPSILATERAL
1.Xth cranial nerve palsy
2.Cerebellar signs
3.Horner’s syndrome
4.Impaired pain, temperature
and touch on the upper
half of face
B. CONTRA LATERAL
1.Impaired pain and
temperature over the body
64.
65. 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.
66.
67. • 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