Arterial Anatomy and Collaterals

The posterior cerebral circulation provides blood supply to the posterior parts of the brain, which include the posterior portion of the cerebral cortex, cerebellum, and brainstem. The anatomy of the posterior circulation and the anastomosis with the circle of Willis greatly varies in each person. The major arteries of the posterior circulation include vertebral arteries, basilar artery, and posterior cerebral arteries. The circle of Willis provides primary collateral pathways from the anterior to posterior circulation and vice versa. Posterior circulation branches, such as the cerebellar arteries, also anastomose to form a collateral pathway. In this chapter, embryology, anatomy, and characteristics of the collateral system of the posterior circulation are described.