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Right Anteroposterior Oblique View of Midbrain, Sella, and Floor of Middle Cranial Fossa

Surgical Correlation

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Right anteroposterior oblique view of midbrain, sella, and floor of middle cranial fossa. The cerebrum has been dissected away and the brainstem preserved in situ in this specimen. The left olfactory bulb and tract can be seen emerging from behind the crista galli in the anterior cranial fossa. The anterior petroclinoid ligament extends from the anterior clinoid process of the lesser wing of sphenoid to the petrous apex of the temporal bone. The remainder of the tentorium cerebelli is attached to the superior ridge of the petrous bone and to the transverse groove of the occipital bone. It divides the cranial cavity into supratentorial and infratentorial compartments. The tentorial notch or incisura is a U-shaped space that curves around the junction of the midbrain and pons to accommodate passage of the brainstem into the posterior fossa. The hyper-pigmented substantia nigra lies within the tegmentum of the midbrain posterior to the cerebral peduncles. The right oculomotor (CNIII) nerve can be seen leaving the ventral midbrain toward the lateral wall of the cavernous sinus. The nerve penetrates the dura between the anterior and posterior petroclinoid ligaments lateral to and in front of the posterior clinoid process. 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 middle cranial fossa is the lateral depression between the lesser wing of the sphenoid and petrous portion of the temporal bone. The dura mater has been stripped to reveal the trigeminal ganglion and its first division, the ophthalmic (CNV1) nerve, which courses to the orbit via the superior orbital fissure.  The ganglion lies in Meckel's cave on the trigeminal depression anteromedial to the trigeminal prominence, an elevation on the petrous ridge. The tentorium has been incised to expose 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 transverse sinus is exposed in the posterior tentorium at the junction of the occipital bone and petrous ridge where it continues as the sigmoid sinus. It receives the superior petrosal sinus, contained in the tentorial attachment to the petrous ridge, draining the cavernous sinus. (Image courtesy of PA Rubino)

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