Fig. 5. Representation of cranial nerves and related basal structures in the area of the midbrain, middle fossa, cavernous sinus, and orbital apex. The roof of the right orbit, sphenoid wing, floor of middle fossa, and petrous ridge have been sectioned; a section of the tentorial edge is removed to demonstrate the course of trochlear nerve (4). The cerebellum is retracted to show structures in the posterior fossa. Cross-section of the midbrain is at level of superior colliculi and red nuclei. (2, optic nerves and chiasm; 3, oculomotor nerves [note relationship to posterior cerebral and posterior communicating arteries]; 4, trochlear nerve in edge of tentorium; 5, trigeminal nerve [51, ophthalmic division; 52, maxillary division; 53, mandibular division]; 6, abducens nerve [note course up clivus and passage under petroclinoid ligament into posterior aspect of cavernous sinus]; 7, facial nerve; 8, acoustic nerve)