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Right Parasellar and Middle Fossa Regions

Surgical Correlation


Right superolateral view of parasellar and middle fossa regions.  The trigeminal nerve emerges from the pons and courses within the prepontine cistern before entering Meckel's cave, an aperture between the meningeal and periosteal dura at the trigeminal depression, a bony indentation at the petrous apex. Meckel's cave houses the trigeminal (Gasserian) ganglion and proximal roots of the ophthalmic, maxillary, and mandibular nerves. Temporal bone has been removed to expose the petrous segment of the internal carotid artery as well as the semicanal containing the tensor tympani muscle and the bony part of the Eustachian tube. Emerging from the anterior wall of the petrous bone are the greater superficial petrosal and lesser petrosal nerves. The former passes deep to the trigeminal ganglion towards foramen lacerum, while the latter leaves the middle ear cavity and courses toward the foramen ovale where its preganglionic parasympathetic fibers synapse in the otic ganglion to provide secretomotor supply to the parotid gland. Along the superior border of the petrous bone is the attachment of the tentorium cerebelli, which contains the superior petrosal sinus. The roof of the internal auditory canal has been removed to expose the facial and vestibulocochlear nerves. Both the cochlea and labyrinth are in view here as well. Along the upper right border of this image are the oculomotor, trochlear, and ophthalmic nerves converging on the superior orbital fissure and orbit. (Image courtesy of AL Rhoton, Jr.)