Superior view of the left petrous region after petrosectomy. For orientation, the left side of this image is rostral. The tentorium has been removed and the superior petrosal sinus has been cut prior to its connection with the transverse sinus at the transverse-sigmoid sinus junction. The semicircular canals of the inner ear remain. The facial nerve exits the cerebellopontine angle and courses with the vestibulocochlear nerve in close proximity with the anterior inferior cerebellar artery. The facial nerve sends the greater superficial petrosal nerve anteriorly at the level of the geniculate ganglion. The petrous segment of the internal carotid artery is visible, as is the basilar artery deeply. The trigeminal nerve emerges from the lateral pons and courses into Meckel’s cave to become the Gasserian (trigeminal) ganglion, and the mandibular division (V3) is shown here. The tensor tympani muscle is located inferior to the geniculate ganglion on its course to the middle ear and malleus where it functions to dampen loud sounds. (Image courtesy of AL Rhoton, Jr.)