Right posterolateral view of auditory complex following subtotal petrosectomy and mastoidectomy. For orientation, the right border of the image is anterior, the left border is posterior. The sigmoid sinus is located posterior to the bony labyrinth and the semicircular canals have been drilled out. Anterior to the labyrinth is the fundus of the internal auditory canal where the facial nerve ends at the geniculate ganglion. The main trunk of the facial nerve continues posteriorly along the medial wall of the middle ear cavity just inferior to the lateral semicircular canal. Thereafter, is bends sharply to descend in the posterior wall as the mastoid segment of this nerve. Here it gives rise to the chorda tympani branch that arches across the middle ear cavity from posterior to anterior passing between the handle of the malleus and the incus. The malleus is shown attaching to the tympanic membrane across which is the medial end of the external auditory meatus. The stapedius muscle emerges from the pyramidal eminence on the posterior wall of the tympanic cavity and attaches to the neck of the stapes. The epitympanic recess opens posteriorly into the entrance (aditus) of the mastoid antrum within the mastoid process. 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. From the ganglion arise the three nerve divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3).  The ophthalmic and maxillary nerves course forward in the lateral wall of the cavernous sinus superior to which are the oculomotor and trochlear nerves. Within the cavernous sinus is the internal carotid artery. (Image courtesy of AL Rhoton, Jr.)