Corpus: Posterior communicating artery

The posterior communicating artery, or PCOM for short, is a branch of the internal carotid artery. Together with other vessels, the right and left posterior communicating arteries form part of the cerebral arterial circle (Circle of Willis).

2.1. Course

The posterior communicating artery is, on average, 14 mm long and 1.2 mm in diameter. After branching from the terminal segment of the internal carotid artery (C7 segment), it crosses the optic tract. It then runs posteriorly and medially through the interpeduncular cistern, joining the posterior cerebral artery, a branch of the basilar artery, at nearly a right angle. This connection links the anterior and posterior cerebral circulations.

2.2. Branches

The PCOM gives off several small branches, known as the posteromedial central arteries, some of which also arise from the posterior cerebral artery. The largest branch is the anterior thalamoperforating artery or thalamotuberal artery, which supplies the subthalamus and the anterior and ventral sections of the thalamus. Other branches include:

• Chiasmatic branch: Supplies the posterior parts of the optic chiasm
• Tuber cinereum branch: Supplies the optic tract and tuber cinereum
• Mamillary arteries: Supply the mammillary bodies
• Hypothalamic branch: Supplies the posterior part of the hypothalamus

2.3. Norm variants

During embryogenesis, the PCOM serves as the caudal terminal branch of the internal carotid artery and supplies the hindbrain. As development progresses, the basilar artery assumes this role, leading to the regression of the proximal section of the primitive PCOM into the definitive PCOM. However, in approximately 12 % of cases, if the vessel remains wide-lumened, it forms the initial segment of a posterior cerebral artery originating from the internal carotid artery, known as a fetal-type PCOM or fetal PCA. In about 35 % of cases, the PCOM is hypoplastic. Other rare variants include:

• Duplication of the PCOM
• Fenestration of the PCOM (very rare)
• Infundibular origin of the PCOM
• Origin of the anterior choroidal artery from the PCOM

The posterior communicating artery is the second most common site for cerebral aneurysms. These aneurysms can have significant clinical implications, including the risk of rupture leading to subarachnoid hemorrhage.