Endoscopic transclival view of sellar and parasellar anatomy. The pituitary gland is shown contained within the sella turcica of the sphenoid bone. Lateral to this is the cavernous sinus containing the cavernous segment of the internal carotid artery. The carotid sympathetic nerve plexus can be seen on the surface of the artery. The upper clivus has been removed to expose the basilar sinus. The abducens nerve has penetrated the clival dura and courses to the lateral surface of the internal carotid artery within the cavernous sinus. Within the lateral wall of this sinus are the oculomotor, ophthalmic, and maxillary nerves. The oculomotor, ophthalmic, and abducens nerves converge on and traverse the superior orbital fissure to enter the orbit, while the maxillary nerve passes through the foramen rotundum to enter the pterygopalatine fossa. Inferior to this foramen is Vidian canal containing the Vidian nerve that also enters the pterygopalatine fossa. (Image courtesy of AL Rhoton, Jr.)