The cerebellum is perfused by the vertebrobasilar system of arteries (eFig. 9.42). Before merging and forming the basilar artery, each vertebral artery gives rise to a PICA and posterior spinal artery and contributes to the formation of the anterior spinal artery (eFig. 9.71). The PICA perfuses the inferior portion of the cerebellum. At the level of the caudal pons, the AICA branches off the basilar artery and perfuses the anterior and lateral portion of the cerebellum, as well as the middle and inferior cerebellar peduncles (eFig. 9.71). Just before the midbrain, the superior cerebellar arteries branch off of the basilar artery and supply the superior cerebellar peduncles and superior portion of the cerebellar hemispheres (eFig. 9.71).