Right lateral superior view of the middle fossa prior to anterior petrosectomy. For orientation, the bottom border of the image is superior; the top border is inferior. The trigeminal nerve occupies the middle of the field and from its ganglionic expansion, gives rise to its ophthalmic, maxillary, and mandibular nerve branches. The opthalmic and maxillary nerves are pure sensory. The mandibular nerve is both sensory and motor. Note the motor and sensory roots as they converge on the foramen ovale. The oculomotor and trochlear nerves converge on the ophthalmic nerve at the superior orbital fissure. The petrosphenoid ligament serves as a bridge beneath which will course the abducens nerve into the cavernous sinus. The superior petrosal sinus can be seen coursing on the superomedial edge of the petrous bone. Other bony landmarks of the petrous bone are projected in this image as a reminder of the location of other important regions and structures during operative procedures in this area. (Image courtesy of AL Rhoton, Jr.)