Right superolateral view of middle and anterior cranial fossae. The squamous portion of temporal bone, frontal bone, and petrous bone overlying the bony labyrinth have been removed. The optic nerve (CN II) enters the orbit via the optic canal while the following nerves enter the orbit via the superior orbital fissure: oculomotor (CN III), trochlear (CN IV), ophthalmic (CN V1), and abducens (CN VI). In Meckel’s cave, the trigeminal (Gasserian) ganglion gives rise to the trigeminal nerve (CN V). The remaining branching of trigeminal nerve, maxillary (CN V2) and mandibular (CN V3), exit through the foramen rotundum and ovale, respectively. The facial (CN VII) and vestibulocochlear (CN VIII) nerves enter the inner ear through the internal acoustic meatus. The multiple segments of the facial nerve can be seen along its lengthy intraosseous course. From its mastoid segment arises 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. From the geniculate ganglion arises the greater superficial petrosal nerve that passes forward deep to the trigeminal ganglion. The tentorium cerebelli separates the occipital lobe from the cerebellum and contains the superior petrosal sinus along its attachment to the petrous ridge. This sinus empties posteriorly into the transverse sinus contained within the attachment of the tentorium to the transverse groove of the occipital bone. The sigmoid sinus begins at the junction of the superior petrosal sinus and transverse sinus and exits the jugular foramen as the internal jugular vein. The orbit is largely drained by the superior ophthalmic vein, which passes through the superior orbital fissure to end in the cavernous sinus. The internal carotid artery courses within this sinus along with the abducens nerve after its passage through Dorello's canal.  (Image courtesy of AL Rhoton, Jr.)