Right posteromedial view of the petrous portion of temporal bone. The trigeminal nerve (CN V) passes inferior to the superior petrosal sinus where the trigeminal ganglion occupies Meckel's cave at the apex of the petrous portion of the temporal bone. The nervus intermedius, facial (CN VII), and vestibulocochlear (CN VII) nerves are shown entering the internal acoustic (auditory) meatus. Similarly, the glossopharyngeal (CN IX), vagus (CN X), and spinal accessory (CN XI) nerves course toward the jugular foramen. In addition, the jugular bulb, the continuation of the sigmoid sinus also passes through this foramen to become the internal jugular vein. The inferior petrosal sinus is seen descending along the petroclival fissure. It passes through the jugular foramen to empty into the jugular vein. The arcuate eminence is a bony elevation on the anterior surface of the petrous bone that marks the location of the superior semicircular canal. Bone has been removed from the posterior petrous portion to visualize the superior and posterior semicircular canals as well as the endolymphatic sac, a blind pouch filled with endolymph that connects the endolymph compartment of the inner ear with the dura mater in the posterior fossa. (Image courtesy of AL Rhoton, Jr.)