Posterior circulation strokes can be differentiated from anterior circulation strokes based on clinical features. Posterior circulation strokes often present with vertigo, unsteadiness, crossed hemiplegia, bilateral deficits, cerebellar signs, ocular findings, dissociated sensory loss, and Horner's syndrome. The vertebrobasilar system supplies structures such as the cerebellum, medulla, pons, midbrain, thalamus, and occipital and temporal lobes. Common syndromes include lateral medullary syndrome and superior cerebellar artery occlusion. Infarctions in different vascular territories can produce characteristic clinical deficits.

1. Posterior circulation stroke syndromes

2. 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

3. ANATOMY

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

5. 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

7. CIRCLE OF WILLIS – a note

8. CIRCLE OF WILLIS – a note

14. Posterior circulation
Lateral view

24. DISCUSSION

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:

34. MID BRAIN

35. Weber syndrome-occlusion of
perforating branch of posterior cerebral
artery
Clinical features
1.Ipsilateral
a.3rd nerve palsy
2.Contralateral
a.hemiplegia

36. Benedikt syndrome-occlusion of
perforating branch of posterior cerebral
Clinical features
1.Ipsilateral
a.3rd nerve palsy
2.Contralateral
a.cerebellar ataxia

38. 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

39. Occipital lobe-optic pathway and visual
reflexes

40. Occipital lobe-occlusion of left
calcarine artery
Clinical features
1.Right Hemianopia

41. Occipital lobe-occlusion of both
calcarine arteries
Clinical features
1.Bilateral hemianopia-
cortical blindness (light
reflex preserved)

43. Left occipital lobe with corpus
callosum infarction
Left
Clinical features
1.Right hemianopia
2.Alexia without
agraphia

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

47. Structures
supplied by
BASILAR

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

51. Pons-Lower

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

54. Vertebral
artery

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

56. • Branches:
– Anterior spinal artery
– Posterior spinal artery
– Posterior inferior cerebellar artery
VERTEBRAL… contd

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”

62. Medulla

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

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.

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

68. THANK YOU
Dr.Karthik Raghavan
Postgraduate MD (Int. Med)
SRM Medical College & Hospital