Superior view of sellar and parasellar structures. The pituitary gland is seen in the center of this image where it rests in the sella turcica (between the tuberculum and dorsum sellae) and is covered by the diaphragma sellae. An opening in the center of this dural fold allows the pituitary stalk or infundibulum to connect to the hypothalamus. In front and behind the gland are anterior and posterior intercavernous venous sinuses that connect the right and left cavernous sinuses across the midline (dura removed). On the right side, the petroclinoid ligament has been selectively preserved. It is a dural fold that extends between the anterior and posterior clinoid processes and the petrous temporal bone (at its apex). It separates into two bands, anterior and posterior petroclinoid ligaments, to the respective clinoids. The anterior band forms the superior part of the cavernous sinus. Beneath it passes the oculomotor nerve into the lateral wall of the cavernous sinus. The trochlear nerve enters the lateral wall of the cavernous sinus superior to the petroclinoid ligament and courses between the oculomotor and ophthalmic nerves to the superior orbital fissure before entering the orbit. The trigeminal nerve crosses the apex of the petrous bone where it expands as the trigeminal or Gasserian ganglion. The ganglion lies in Meckel's cave on the trigeminal impression. From this sensory ganglion arise its three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3) coursing toward their openings of exit; superior orbital fissure, foramen rotundum, and foramen ovale, respectively. The venous plexus at the foramen ovale connects the pterygoid plexus in the infratemporal fossa with the cavernous sinus. Anteriorly, the optic nerves and ophthalmic arteries can be seen entering the optic canals to the orbits. Posteriorly, the basilar artery can be seen on the ventral surface of the pons adjacent to the clivus. (Image courtesy of PA Rubino)