Posterior cerebral artery

The posterior cerebral arteries are the terminal branches of the basilar artery and supply the occipital lobes and posteromedial temporal lobes.

Summary

• origin: terminal branches of the basilar artery

• course: from basilar towards occiput

• main branches

  • posterior communicating artery (not really a branch, see embryology below)

  • medial and lateral posterior choroidal arteries

  • calcarine artery

• supply: occipital lobes and posteromedial temporal lobes

Gross anatomy

The posterior cerebral artery is divided into four (or sometimes five) segments ^8,11. It is worth noting that the definition of the distal segments (P3 and P4) differs between Terminologia Anatomica and routine clinical neuroradiological/neurosurgical articles. This article will only cover the latter.

• P1: pre-communicating segment

  • originates at the termination of the basilar artery

  • terminates to the posterior communicating artery (PCOM), within the interpeduncular cistern

  • origin of the artery of Percheron variant (supplying the bilateral medial thalami)

• P2: post-communicating segment

  • from the PCOM around the midbrain

    • P2A (anterior): sub-segment courses through the crural cistern

    • P2P (posterior or ambient): sub-segment courses through the ambient cistern

  • terminates at the origin of the lateral occipital artery/lateral temporal trunk, as it enters the quadrigeminal cistern

• P3: quadrigeminal segment

  • ​courses posteromedially through the quadrigeminal cistern

  • terminates as it enters the sulci of the occipital lobe

• P4: cortical segment

  • ​within the sulci of the occipital lobe

  • e.g. calcarine artery, within the calcarine fissure

• P5: terminal branches

  • terminal branches of the calcarine artery and parieto-occipital artery ¹¹

Branches

Location and presence of branches are variable¹¹.

P1

• posterior communicating artery (not really a branch, see embryology below)

• posterior thalamoperforator

• collicular (quadrigeminal) artery

• short and long circumflex arteries

P2

• medial posterior choroidal arteries

• thalamogeniculate perforator

• peduncular perforator

• lateral occipital artery/lateral temporal trunk (most reliably present)

  • anterior temporal branches

  • intermediate temporal branches (variable)

  • posterior temporal branches

P3

• lateral posterior choroidal arteries

• temporo-occipital artery (also commonly arises from P2)

• splenial artery (variable origin as it may also commonly arise from a medial occipital artery/P4 segment)

P4

• calcarine artery

• parieto-occipital artery

P5

Terminal branches of the calcarine and parieto-occipital arteries.

Supply

The posterior cerebral artery curls around the cerebral peduncle to provide supply to the tegmentum and majority of the midbrain (excluding the crus cerebri). Branches of PCOM, P1 and P2 supply the thalamus. The artery then passes above the tentorium to supply the posteromedial surface of the temporal lobe and the occipital lobe, and the splenium of the corpus callosum. The visual cortex responsible for the contralateral field of vision lies in its territory. The macular part of the visual cortex often receives a dual blood supply from the PCA and the MCA, which explains the "macular sparing" phenomenon in some patients following a PCA infarct.

Embryology

The fetal posterior cerebral artery arises as the posterior division of the internal carotid artery. These then fuse in the midline to form the superior most of the basilar artery ⁹. The proximal portion of the fetal posterior cerebral artery then reduces in caliber remaining as the posterior communicating artery. As such, from an embryologic point of view, the posterior communicating artery is a branch of the internal carotid artery even though in a minority of individuals normal flow in the posterior communicating artery is from posterior to anterior ¹⁰.

Variant anatomy

• fetal posterior cerebral artery: unilateral incidence 13-15%, bilateral incidence 0.5% ⁹

• fenestration: rare

• duplicated: rare, fetal origin and normal origin on the same side ⁶

Related pathology

• posterior cerebral artery infarction