Dictionary.net

a ring of arteries at the base of the brain

a ring of arteries at the base of the brain

A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY, MIDDLE CEREBRAL ARTERY, POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.

A loop of vessels near the base of the brain.

A roughly circular channel of communication between the arteries of the base of the brain, formed by the anterior, middle, and posterior cerebral and the anterior and posterior communicating arteries.