Endoscopic view of left anterior cerebellopontine angle and emergent cranial nerves. A portion of the pons is visible on the upper left border of the image while the rostral portion of the medulla is seen along the lower left border. The anterolateral surface of the cerebellum is visible in the center. The right and left vertebral arteries are shown converging to form the basilar artery at the pontomedullary junction. The vertebral arteries give rise to anterior spinal arteries that will descend onto the ventral surface of the spinal cord. A segment of the anterior inferior cerebellar artery can be seen following the facial and vestibulocochlear nerves toward the internal acoustic meatus. It gives rise to the labyrinthine artery that travels with these nerves into the meatus to supply the inner ear. The trigeminal nerve emerges from the lateral pons to course over the petrous apex to Meckel's cave. Inferior to the trigeminal nerve at the lateral pontomedullary sulcus emerge the facial (CNVII) and vestibulocochlear (CNVIII) nerves. Along the lateral medulla emerge in rostral-caudal sequence the glossopharyngeal (CNIX), vagus (CNX), and spinal accessory (CNXI) nerves, which travel to the jugular foramen. The hypoglossal (CNXII) nerve exits the sulcus between the medullary pyramid and olive to course toward the hypoglossal canal. (Image courtesy of AL Rhoton, Jr.)