Anterior transsphenoidal coronal view with resection of clivus. A window in the lower clivus reveals the upper portion of the medulla oblongata, the right and left vertebral arteries, and origin of the basilar artery. The pharyngotympanic (Eustachian) tubes can be seen connected to the anteroinferior aspect of the petrous bone and communicate the tympanic cavity with the nasopharynx. The upper portion of this field shows the posterior wall of the sphenoid sinus (within the body of the sphenoid). Through the thin bony wall the anterior surface of the pituitary gland, as it rests within the sella turcica, is in view. The cavernous segments of the internal carotid artery are also in view as they course along the lateral surfaces of the sphenoid body. At the superolateral border of the body of the sphenoid is the apex of the orbit containing the optic nerve, extraocular muscles, and associated neurovasculature to the orbital contents. Inferolaterally the maxillary nerves pass through the foramen rotundum toward the pterygopalatine fossa. Inferomedial to the foramen rotundum near the floor of the sphenoid sinus are the pterygoid canals transmitting the nerve of the pterygoid canal (Vidian nerve) to the pterygopalatine fossa and pterygopalatine ganglion. The hypoglossal canals are included in the dissection field and contain the hypoglossal nerve. (Image courtesy of AL Rhoton, Jr.)