Ventrolateral perspective of the cerebellopontine angle. The basilar artery is the prominent midline arterial supply to the posterior fossa. The posterior inferior cerebellar artery (PICA, a branch of the vertebral artery) courses posterior to the hypoglossal nerve which exits the medulla in the sulcus between the pyramids and the inferior olives. The PICA has anterior medullary, lateral medullary, and tonsillomedullary segments visible here. The AICA is a branch of the basilar artery and courses laterally toward the facial and vestibulocochlear nerves before supplying the anterior inferior cerebellum. The cerebellopontine fissure is the fissure between the cerebellum and middle cerebellar peduncle of the pons and lies just lateral to the CN VII-VIII complex and the flocculus, and together comprises the cerebellopontine angle (CPA). (Image courtesy of AL Rhoton, Jr.)