Magnified view of right cavernous sinus, brainstem, and sellar structures. The left olfactory bulb and tract can be seen emerging from behind the crista galli near the top border of the image and coursing on the floor of the anterior cranial fossa. At the left border, the hyper-pigmented substantia nigra lies within the tegmentum of the midbrain posterior to the cerebral peduncles. The oculomotor (CNIII) nerves can be seen leaving the ventral midbrain, passing through the interpeduncular fossa toward the superior lateral wall (removed) of the cavernous sinus. In their course they pass caudal to the posterior cerebral artery, between this and the superior cerebellar artery, both branches of the midline basilar artery. They penetrate the dura between the anterior and posterior petroclinoid ligaments lateral to and in front of the posterior clinoid process. The right trochlear (CNIV) nerve is seen leaving the dorsal surface of the midbrain and curving around the cerebral peduncle to gain the lateral wall of the cavernous sinus. It also passes between these two arteries and penetrates the dura between the free and attached edges of the tentorium cerebelli. Ventral to the midbrain is the body of the sphenoid featuring the sella turcica, the midline depression containing the pituitary gland and distal pituitary stalk through the opening of the diaphragma sellae. The sella is bounded anteriorly by the tuberculum sellae and posteriorly by the dorsum sellae and its posterior clinoid processes. In this view, medial to the anterior clinoid processes are the optic nerves (CNII) emerging from the optic canals and the supraclinoid internal carotid arteries. The bone of the planum sphenoidale, anterior to the tuberculum, has been removed to expose the sphenoid sinus. The middle cranial fossa is the lateral depression between the lesser wing of the sphenoid and petrous portion of the temporal bone. The meningeal dura lateral to the body of the sphenoid has been stripped to reveal the cavernous sinus, the cavernous internal carotid artery, and the trigeminal ganglion and its three divisions: ophthalmic (CNV1), maxillary (CNV2), and mandibular (CNV3) coursing toward their openings of exit; superior orbital fissure, foramen rotundum, and foramen ovale, respectively. The trigeminal nerve crosses the apex of the petrous bone and expands as the trigeminal ganglion, which lies in Meckel's cave on the trigeminal depression anteromedial to the trigeminal prominence, an elevation on the petrous ridge. The ophthalmic nerve passes through the superior orbital fissure in company with the oculomotor, trochlear, and abducens (not in view) nerves. The greater superficial petrosal nerve can be seen leaving its hiatus on the anterior surface of the petrous bone. It passes deep to the mandibular nerve toward the foramen lacerum and pterygoid canal to unite with the deep petrosal nerve to form Vidian nerve. The tentorium has been incised to expose part of the rostral cerebellum. This surface is supplied by the medial and lateral branches of the superior cerebellar arteries that course posteriorly in the pontomesencephalic sulcus above the superior cerebellar peduncles before ramifying. The superior petrosal sinus has been exposed in the tentorial attachment to the petrous ridge and drains the cavernous sinus to the transverse sinus. (Image courtesy of PA Rubino)