Circle of Willis Diagram

If the circle of Willis is blocked, it can often compensate by rerouting blood flow through alternate pathways. However, if this collateral circulation is insufficient, it may lead to reduced blood supply to parts of the brain, causing ischemia or a stroke.

The circle of Willis is a ring of interconnected arteries at the base of the brain. It ensures consistent blood flow by rerouting blood if a blockage or narrowing occurs in one of the main arteries supplying the brain.

The most common anomaly is hypoplasia (underdevelopment) of one or both posterior communicating arteries (PCOMs). This can affect the circle’s ability to provide collateral blood flow.