Posterosuperior view of the right cerebellopontine angle. The facial (CN VII) and vestibulocochlear (CN VIII) nerves can be seen entering the internal acoustic meatus and the glossopharyngeal (CN IX), vagus (CN X), and spinal accessory nerves (CN XI) can be seen entering the jugular foramen. 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. Union of the vertebral arteries give rise to the basilar artery. Its anterior inferior cerebellar artery (AICA) branch 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 foramen of Luschka communicates the fourth ventricle to the subarachnoid space of the cerebellopontine cistern. This opening lies posterior to the root of the glossopharyngeal nerve. (Image courtesy of AL Rhoton, Jr.)