Circle of Willis Variant Anatomy

The Circle of Willis is a ring like configuration of arteries that feed the brain.

It is fed by the two carotid arteries and the basilar artery, with normally 6 arteries (3 per side) extending from the Circle of Willis to supply the cerebrum of the brain.

In some people a complete circle, or all 6 brain supplying arteries do not develop, and this is called variant anatomy of the Circle of Willis.