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Posterior cerebral artery

The Posterior Cerebral Artery (PCA) is a critical vessel in the brain’s posterior circulation, responsible for supplying blood to the occipital lobes, inferior temporal lobes, thalamus, and other deep structures. It plays a vital role in vision, sensory integration, and memory by delivering oxygenated blood to these areas. Any compromise in its blood flow can result in significant neurological deficits, most notably affecting vision.

Synonyms

  • PCA

  • Posterior cerebral arteries (plural, referring to right and left sides)

  • Arteria cerebri posterior (Latin)

  • Terminal branch of the basilar artery

Origin and Course

  • The PCA typically arises as the terminal branch of the basilar artery at the level of the midbrain.

  • Sometimes, the initial segment (P1) can arise from the internal carotid artery via the posterior communicating artery (fetal origin of PCA).

  • The artery curves laterally and posteriorly around the midbrain, passing above the tentorium cerebelli.

  • It then travels in the ambient cistern, passing around the cerebral peduncles.

  • The PCA divides into several cortical branches supplying the occipital and inferior temporal lobes.

  • It has four segments:

    • P1 (pre-communicating segment): from the basilar bifurcation to the posterior communicating artery

    • P2 (post-communicating segment): from the posterior communicating artery to the posterior edge of the midbrain

    • P3 (quadrigeminal segment): in the quadrigeminal cistern

    • P4 (cortical segment): small terminal branches on the brain’s surface

Function

  • Supplies the occipital lobes (primary visual cortex), thus crucial for vision.

  • Supplies the inferior temporal lobes (important for visual memory).

  • Gives branches to the thalamus (sensory integration) and midbrain (motor control and consciousness).

  • Involved in supplying the choroid plexus of the lateral and third ventricles.

MRI Appearance

  • On MR angiography (MRA), the PCA appears as a paired artery arising from the basilar artery and curving around the midbrain.

  • Flow voids seen on T2-weighted images indicate normal flow within the PCA.

  • Acute PCA infarct is seen as restricted diffusion (hyperintensity on DWI and hypointensity on ADC) in the occipital lobe or thalamus.

  • Chronic infarcts appear as areas of encephalomalacia and volume loss in PCA territories.

  • Susceptibility-weighted imaging (SWI) may show blooming if there is associated hemorrhage.

CT Appearance

  • On non-contrast CT, the PCA itself is not directly visualized unless there is vascular calcification or thrombosis.

  • Acute PCA infarcts appear as areas of hypoattenuation (low density) in the occipital lobe or thalamus.

  • Loss of gray-white differentiation and subtle swelling may be seen in the early phase of infarct.

  • CT angiography (CTA) can delineate the course of the PCA and show any occlusion, stenosis, or aneurysm.

  • Chronic infarcts are seen as areas of encephalomalacia and ex vacuo dilatation of the occipital horn of the lateral ventricle.

MRI images

Posterior cerebral artery artery coronal t2 3T MRI image

MRI images

Posterior cerebral artery artery sagittal t2 3T MRI image

MRI images

Posterior cerebral artery axial t2 3T MRI image

CT image

Posterior cerebral artery ct image