Posterosuperior view of right cerebellopontine angle. The cerebellum has been reflected away to visualize the choroid plexus within the lateral recess of the 4th ventricle. 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. The facial (CN VII) and vestibulocochlear (CN VIII) nerves can be seen entering the internal acoustic meatus. The anterior inferior cerebellar artery (AICA) arises from the basilar artery and passes between CNs VII and VIII. The labyrinthine artery most commonly branches from AICA and accompanies CN VIII to the inner ear. Posterior inferior cerebellar artery (PICA) arises from the vertebral artery to supply the cerebellum. (Image courtesy of AL Rhoton, Jr.)