Left lateral view of the cerebellopontine angle. A left retrosigmoid craniotomy reveals the cerebellopontine angle and the associated cerebrovascular and neurologic landmarks. The cerebellar hemisphere is retracted. The spinal accessory nerve courses rostrally from the medulla to enter the jugular foramen along with the glossopharyngeal and vagus nerves. The posterior inferior cerebellar artery (PICA) branches from the intradural vertebral artery and courses laterally around the medulla to supply the posterior inferior cerebellum. Superiorly, the facial and vestibulocochlear nerves leave the pontomedullary junction and course anterolaterally into the internal acoustic meatus. The anterior inferior cerebellar artery (AICA), a branch of the basilar artery, courses around the facial-vestibulocochlear nerve complex and gives off the labyrinthine artery, which courses along this complex into the acoustic meatus. The abducens nerve is visible deep (medially) emanating from the medial pontomedullary junction. (Image courtesy of AL Rhoton, Jr.)