The Circle of Willis provides collateral circulation at the base of the brain. Which artery most commonly (80% of cases) gives rise to the posterior communicating artery?

• A Internal carotid artery — the PComm arises from its posterior surface before the bifurcation ✓
• B Posterior cerebral artery — arising from the basilar artery
• C Middle cerebral artery — from its horizontal (M1) segment
• D Basilar artery — arising from its bifurcation

Explanation

The posterior communicating artery (PComm) arises from the posterior surface of the internal carotid artery just before the ICA bifurcates into the anterior and middle cerebral arteries; it runs backward to join the posterior cerebral artery. A PComm aneurysm compresses CN III (pupillomotor fibers), causing a painful third nerve palsy with pupil involvement — a neurosurgical emergency. In a 'fetal-type' PCA (20% of cases), the PComm is large and the PCA is supplied predominantly from the ICA, not the basilar.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.