Variants of the circle of willis on non contrast magnetic resonance angiography

The Circle of Willis (CoW) distributes oxygenated blood throughout the brain and represents the only major anastomosis of the brain. The study of variations in CoW is crucial for avoiding confusion of the anomalies with aneurysms, evaluating collateral pathways in the intracerebral circulation, and enhancing pre-operative planning in patients undergoing surgery at the skull base.