Posterior Perspective of Brainstem, Cerebellopontine Angle, and Jugular Foramen. The diamond-shaped fourth ventricle is demonstrated.  The lateral recess of the fourth ventricle tapers and continues as the foramen of Luschka, through which choroid plexus is seen extending into the cisternal space beneath the flocculus. The glossopharyngeal, vagus, and spinal accessory nerves can be seen traversing to the jugular foramen. Further superiorly, the facial and vestibulocochlear nerves traverse the cerebellopontine cistern to enter the internal auditory canal. The vertebral artery (V4) passes anterior to the cranial nerves, while the posterior inferior cerebellar artery (PICA) courses posteriorly to perfuse the inferior cerebellum and choroid plexus of the caudal fourth ventricle. (Image courtesy of AL Rhoton, Jr.)