Posterior Cerebral Circulation

Arterial Circulation of Brain

• Brain derive its arterial supply from two separate pathways:
• Anterior circulation which comprises of internal carotid artery and its branches
• Posterior circulation which consists of 2 vertebral arteries, 1 basilar artery, 2 posterior cerebral arteries and their branches

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  Anterior Cerebral Circulation

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  Posterior Cerebral Circulation

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Posterior Circulation

• Also known as vertebrobasilar circulation

• Posterior circulation consists of the following arteries:
• Posterior cerebral arteries
• Vertebral arteries
• Basilar artery
• Posterior inferior cerebellar arteries

• Caplan described three divisions of the vertebrobasilar system in the New England Medical Center-posterior circulation registry (NEMC-PCR):
• Proximal division
• Middle division
• Distal division (Most commonly involved in ischemic stroke)

Posterior Cerebral Artery

• Mostly arises from the basilar artery (70% cases)

• May arise from posterior communicating arteries (20% cases)

• Krayenbühl and Yasargil describe the following major parts of the posterior cerebral artery:
• P1: From the termination of the basilar artery to the posterior communicating artery
• P2: Run around the ambient cistern of the midbrain and pass above the tentorium cerebelli. It has anterior (P2A) and posterior segments (P2P).
• P3: Runs through the quadrigeminal cistern
• P4: Terminal part that ends in calcarine sulcus

• Terminal branches of the parieto-occipital and the calcarine arteries (branches of the P4 segment) are referred to as the P5 segment.

Figure 1: Distribution of Posterior Cerebral Artery

• Diagnostic features of PCA infarction are hemisensory loss and hemianopia without any motor involvement.

• Paresthesias in the face, limbs, and trunk (Lateral thalamus involvement)

• Hemiplegia (Lateral midbrain involvement)

• Weber's syndrome (Ipsilateral CN III palsy with contralateral hemiplegia)

• Signs of left posterior cerebral artery infarction:
• Alexia without agraphia (Non-existent reading comprehension)
• Anomic aphasia (Inability to name objects)
• Visual agnosia (Difficulty in understanding the nature and use of objects presented visually)
• Sensory aphasia
• Gerstmann syndrome

• Signs of right posterior cerebral artery infarction:
• Prosopagnosia (difficulty in recognizing familiar faces)
• Disorientation to place (Inability to recall routes)
• Difficulty visualizing objects or persons
• Visual neglect (Ignoring the left side of the visual field)

• Signs of bilateral posterior cerebral artery Infarction:
• Cortical blindness: Loss of binocular vision in the absence of ophthalmologic cause
• Anton-Babinski syndrome: Visual anosognosia with confabulation in presence of cortical blindness

Figure 2: Territories of Cerebral Vasculature

Source: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing: 2021 Jan, Contributed by Omid Shafaat, M.D.

Figure 1: Cerebral vasculature territories. ACA: anterior cerebral artery; MCA: middle cerebral artery; PCA: posterior cerebral artery; AICA: anterior inferior cerebellar artery; PICA: posterior inferior cerebellar artery; SCA: superior cerebellar artery.

Figure 2: Large right MCA infarction in non-contrast CT Brain

Vertebral Artery

• One on each side

• Arise from the posterosuperior aspect of the first part of the subclavian artery

• Runs in foramen transversarium of cervical vertebrae and pierce dura after reaching foramen magnum

• Ends by joining at the pontomedullary junction to form the basilar artery

• Subdivided into four parts:
• V1: From origin to foramen transversarium of C6 or C7
• V2: From point of entry in first foramen transversarium to last foramen transversarium
• V3: From exiting the last foramen to just before entering in the cranium
• V4: Intracranial portion of the vertebral artery after piercing dura matter

Basilar Artery

• Travels along ventral part of medulla rostrally

• Runs in basilar sulcus of the pons

• Gives off the following branches along its way:
• Anterior inferior cerebellar arteries
• Superior cerebellar arteries
• Paramedian perforating pontine arteries
• Posterior communicating arteries

• Terminates at the ponto-mesencephalic junction by bifurcating into the right and left posterior cerebral arteries

• Common presenting symptoms of posterior circulation stroke includes:
• Nausea or vomiting
• Dizziness or headache
• Horner’s syndrome
• Unilateral limb weakness
• Dysarthria
• Blurry vision or nystagmus
• Ataxia
• Babinski’s sign

• Wallenberg’s syndrome or lateral medullary infarction ➞ Due to occlusion of the posterior inferior cerebellar artery or the vertebral artery ➞ Decreased perception of pain and temperature on the ipsilateral face and the contralateral side of the trunk and limbs, vertigo, ataxia, dysphagia, dysarthria, unilateral arm weakness, dysphonia, horizontal and rotary nystagmus, and respiratory and cardiovascular dysfunction

• Vertebral basilar syndrome ➞ proximal posterior circulation affected ➞ Dizziness, nausea, vomiting, nystagmus, unilateral limb weakness, gait ataxia, trigeminal nerve abnormalities.

• Basilar artery occlusion ➞ Dizziness and headache, unilateral limb weakness, dysarthria, Facial nerve abnormalities, Babinski’s sign, and oculomotor abnormalities, “Locked in” syndrome (Ventral pons involvement).

Further Reading

• Kuybu, O., Tadi, P., & Dossani, R. H. (2021). Posterior Cerebral Artery Stroke. In StatPearls. StatPearls Publishing.

Bibliography

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• Tahir, R. A., Haider, S., Kole, M., Griffith, B., & Marin, H. (2019). Anterior Cerebral Artery: Variant Anatomy and Pathology. Journal of vascular and interventional neurology, 10(3), 16–22.

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• Searls DE, Pazdera L, Korbel E, Vysata O, Caplan LR. Symptoms and signs of posterior circulation ischemia in the new England medical center posterior circulation registry. Archives of neurology. 2012 Mar;69(3):346–351

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• Symptoms and signs of posterior circulation ischemia in the new England medical center posterior circulation registry. Searls DE, Pazdera L, Korbel E, Vysata O, Caplan LR Arch Neurol. 2012 Mar; 69(3):346-51

• Nouh, A., Remke, J., & Ruland, S. (2014). Ischemic posterior circulation stroke: a review of anatomy, clinical presentations, diagnosis, and current management. Frontiers in neurology, 5, 30. https://doi.org/10.3389/fneur.2014.00030

• D'Souza, D., Hacking, C. Brain arterial vascular territories. Reference article, Radiopaedia.org.(accessed on 07 Oct 2021) https://radiopaedia.org/articles/1085