Posterosuperior view of the right cerebellopontine angle. Bone has been removed from the posterior petrous portion at the internal acoustic meatus to visualize the facial (CN VII) and vestibulocochlear (CN VIII) nerves emerging from the pontomedullary junction. The nervus intermedius contains the sensory and parasympathetic fibers that run within the facial nerve. The vertebral artery gives rise to the posterior inferior cerebellar artery (PICA) that often passes between the vagus (CN X) and spinal accessory (CN XI) nerves before they enter the jugular foramen. The vertebral artery then gives rise to the basilar artery. The first branch of basilar artery, anterior inferior cerebellar artery (AICA), passes between CN VII and VIII. Most often, AICA gives off the labyrinthine artery that travels with CN VIII to supply the inner ear. The superior petrosal vein forms from the union of several veins before entering the superior petrosal sinus. It drains the anterior cerebellum and brainstem. A portion of the choroid plexus of the fourth ventricle can also be seen. (Image courtesy of AL Rhoton, Jr.)