Posterior cerebral artery

Origin and course

The left and right posterior cerebral artery arises from the bifurcation of the basilar artery, which occurs at the superior border of the pons, posterior to the dorsum sellae. From there, the posterior cerebral artery continues laterally along the superior border of the pons. It courses parallely to the superior cerebellar artery, separated from it by the oculomotor nerve (CN III). Upon reaching the lateral border of the pons, the posterior cerebral artery curves around the cerebral peduncle to reach the medial surface of the cerebral hemispheres, where it supplies the temporal and occipital lobes.

General anatomy textbooks divide the posterior cerebral artery into three segments; P1, P2 and P3. However, the latest neuroanatomical classification which is used in neurosurgical practice divides the artery into the following four segments:

• P1: extends from the basilar bifurcation to the anastomosis with the posterior communicating artery
• P2: extends from the anastomosis with the posterior communicating artery to the part of the artery that lies in the perimesencephalic cistern on the posterior border of the lateral aspect of the midbrain.
• P3: extends from the posterior border of the lateral aspect of the midbrain to the origin of parieto-occipital and the calcarine arteries.
• P4: represent the terminal branches found in the calcarine fissure.

Branches and supply

Like the anterior and middle cerebral arteries, the posterior cerebral artery gives off branches that are divided into central and cortical branches. The central branches supply the subcortical structures and include the thalamoperforating, thalamogeniculate, and posterior choroidal arteries. Cortical branches are distributed to different parts of the cortex and are named accordingly, and involve the temporal, occipital, parieto-occipital and calcarine arteries. 

The thalamoperforating arteries are groups of small branches that arise from the P1 segment of the posterior cerebral artery. These branches penetrate the posterior perforated substance and supply either parts of the thalamus, or the third ventricle and the midbrain. 

The thalamogeniculate arteries are the next branches that spring out the P2 segment of the posterior cerebral artery. They supply the medial and lateral geniculate bodies and the pulvinar of the thalamus. 

The posterior choroidal arteries are usually given off as two branches from the P2 segment, a medial and lateral one. These branches supply the posterior portion of the thalamus and the choroid plexus.

The temporal branches are usually given off from the P2 segment as two or three branches, most commonly an anterior and posterior branch. These arteries supply the uncus, and the parahippocampal, medial and lateral occipitotemporal gyri.

The occipital branches usually consist of a lateral and medial branch. These branches supply the cuneus, lingual gyrus and posterolateral surface of the occipital lobe.

The parieto-occipital artery is one of the terminal branches of the posterior cerebral artery that arises from its P3 segment. It supplies the cuneus and precuneus.

The calcarine artery is the other  terminal branch of the posterior cerebral artery that springs out of its P3 segment. This artery often arises indirectly, as a branch of one of the occipital arteries. The calcarine artery supplies the visual cortex, inferior cuneus, and part of the lingual gyrus.

Anatomical variations

• Fetal posterior cerebral artery is a relatively common variant of the posterior circulation, having a unilateral incidence of 10%, and a bilateral incidence of 8%. This variant is characterized by a reduced size of the P1 segment of the posterior cerebral artery.
• Posterior cerebral artery fenestration is a rare variant that involves the splitting of a portion of the artery into two, then rejoining distally