Right superior view of auditory complex following subtotal petrosectomy. The superior petrosal sinus can be seen coursing along the superior border of the petrous bone within the attachment of the tentorium cerebelli. The roof of the internal auditory canal has been drilled out to reveal the facial and vestibulocochlear nerves and a loop of the anterior inferior cerebellar artery. These nerves pass between the cochlear anteriorly and the labyrinth posteriorly. The facial nerve ends at the geniculate ganglion, which gives rise to the greater superficial petrosal nerve that courses anteriorly deep to the Gasserian (trigeminal) ganglion. The main trunk of the facial nerve (cut) is directed posteriorly within the facial canal just inferior to the lateral semicircular canal. The roof of the tympanic cavity has also been drilled out to show the malleus (attached to the tympanic membrane) and the incus. The epitympanum opens posteriorly into the aditus of the mastoid antrum within the mastoid process. The chorda tympani crosses the middle ear cavity from posterior to anterior passing between the handle of the malleus and the incus. The anterior wall has also been drilled out to reveal the tensor tympani muscle in its semicanal located just superior to the bony part of the Eustachian tube. The tensor attaches to the malleus and functions to dampen loud sounds. The tympanic membrane bounds the medial end of the external auditory meatus. Crossing the apex of the petrous bone is the cisternal part of the trigeminal nerve, which expands within Meckel's cave as the Gasserian (trigeminal) ganglion, a sensory ganglion of this nerve. The mandibular nerve can be seen arising from the ganglion and passing through the foramen ovale. Slightly posterolateral to this nerve is the middle meningeal artery emerging through the foramen spinosum from the infratemporal fossa.  (Image courtesy of AL Rhoton, Jr.)