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Superolateral Views of Right Orbit, Middle Fossa, and Petrous Bone

Surgical Correlation

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Superolateral views of right orbit, middle fossa, and petrous bone. Bones of the anterior and middle fossa floors have been removed to show underlying contents. The trigeminal nerve crosses the apex of the petrous bone and its ganglion occupies the trigeminal depression. From here, its ophthalmic branch (sensory only) passes forward through the superior orbital fissure to enter the orbit. Its lacrimal nerve branch courses along the upper lateral wall of the orbit toward the lacrimal gland. The maxillary branch (sensory only) of the trigeminal nerve passes through the foramen rotundum to the pterygopalatine fossa. The mandibular branch (both sensory and motor) passes through the foramen ovale to enter the roof of the infratemporal fossa. The superior head of the lateral pterygoid muscle can be seen in this fossa. Lateral to this is the inferior boundary of the temporal fossa showing cross-sectional fibers of the temporalis muscle.  Posterior to the trigeminal ganglion the roof of the internal auditory canal has been drilled to expose the facial and superior vestibular  nerves. At the end of the canal the facial nerve ends at the geniculate ganglion from which arises the greater superficial petrosal nerve carrying preganglionic parasympathetic fibers. The main trunk of the facial nerve bends posteriorly to course along the medial wall of the tympanic cavity inferior to the lateral semicircular canal.  The anterior surface of the petrous bone was also drilled to show the petrous segment of the internal carotid artery. The oculomotor, trochlear, and abducens nerves are shown converging on the superior orbital fissure to enter the orbit with the ophthalmic nerve. These nerves are associated with the cavernous sinus. In the orbit, the lateral rectus follows along the lateral orbital wall to insert on the eyeball. The broad levator palpebrae superioris muscle (elevator of the eyelid) lays over the superior rectus muscle. The frontal branch of the ophthalmic nerve can be seen running anteriorly superficial to these muscles. (Image courtesy of AL Rhoton, Jr.)

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