Posterosuperior view of right lateral posterior cranial fossa. Bone has been removed from the posterior petrous portion at the internal acoustic meatus to visualize facial (CN VII) and vestibulocochlear (CN VIII) nerves. The posterior portion of the occipital bone as also been removed at the occipital condyle to visualize the inferior course of the internal carotid artery and internal jugular vein. The latter is a continuation of the jugular bulb through the jugular foramen. The vertebral artery can be seen ascending through the foramen magnum with the spinal accessory nerve (CN XI). The vertebral artery gives rise to the posterior inferior cerebellar artery (PICA) that often passes between 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 the basilar artery, usually the anterior inferior cerebellar artery (PICA), passes between CN VII and VIII. It gives rise to the labyrinthine artery which accompanies these nerves into the internal auditory meatus.  The superior petrosal vein (vein of Dandy) is an important venous drainage system in the posterior fossa. It drains the anterior cerebellum and brainstem and forms usually by union of the pontine trigeminal vein, vein of the cerebellopontine fissure, and the vein of the middle cerebellar peduncle.  (Image courtesy of AL Rhoton, Jr.)