Posterior cerebral arteries

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Latin	arteria cerebri posterior

The posterior cerebral arteries (PCAs) are vital components of the cerebral circulation that supply blood to the occipital lobe, the inferior temporal lobe, and various deep structures of the brain. They are part of the Circle of Willis, a critical anastomotic system that provides collateral circulation to the brain.

Anatomy

The posterior cerebral arteries arise from the bifurcation of the basilar artery at the level of the pons and the midbrain. Each PCA travels laterally and posteriorly around the midbrain, giving off several branches that supply different regions of the brain.

Segments

The PCA is divided into four segments:

• P1 segment: This segment extends from the origin of the PCA at the basilar artery bifurcation to the posterior communicating artery. It is also known as the pre-communicating segment.

• P2 segment: This segment extends from the posterior communicating artery to the quadrigeminal cistern. It is also known as the ambient segment.

• P3 segment: This segment extends from the quadrigeminal cistern to the calcarine sulcus. It is also known as the quadrigeminal segment.

• P4 segment: This segment is the cortical segment, supplying the occipital lobe and the inferior temporal lobe.

Branches

The posterior cerebral artery gives rise to several important branches:

• Cortical branches: These branches supply the occipital lobe and the inferior part of the temporal lobe.

• Central branches: These branches supply deep structures such as the thalamus, the midbrain, and the choroid plexus of the third and lateral ventricles.

• Calcarine artery: This is a significant branch that supplies the primary visual cortex located in the occipital lobe.

Function

The primary function of the posterior cerebral arteries is to supply oxygenated blood to the occipital lobes, which are responsible for processing visual information. They also supply parts of the temporal lobes, the thalamus, and the midbrain, which are involved in various sensory and motor functions.

Clinical Significance

Posterior Cerebral Artery Stroke

A stroke in the territory of the posterior cerebral artery can lead to a variety of symptoms depending on the specific area affected. Common symptoms include:

• Visual disturbances: Due to the involvement of the occipital lobe, patients may experience visual field defects such as homonymous hemianopia.

• Thalamic syndrome: If the thalamus is affected, patients may experience sensory disturbances, pain, and other sensory abnormalities.

• Memory problems: Involvement of the temporal lobe can lead to memory deficits.

Aneurysms

Aneurysms can occur in the posterior cerebral artery, although they are less common than in the anterior circulation. Rupture of a PCA aneurysm can lead to subarachnoid hemorrhage, which is a medical emergency.

Imaging

The posterior cerebral arteries can be visualized using various imaging techniques such as magnetic resonance angiography (MRA) and computed tomography angiography (CTA). These imaging modalities help in diagnosing conditions such as strokes, aneurysms, and other vascular abnormalities.

See Also

• Circle of Willis
• Basilar artery
• Cerebral circulation