Anterior transcranial coronal view through the sphenoid bone with exposure of the clivus region. 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. A window in the upper clivus reveals the basilar artery on the pons, the pituitary gland, and the cavernous segment of the internal carotid 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. At the upper part of the image are the optic canals and superior orbital fissures (apex of the orbit) containing the optic nerve, ophthalmic artery, extraocular muscles, and associated neurovasculature to the orbital contents. Inferiorly the maxillary nerves pass through the foramen rotundum toward the pterygopalatine fossa and inferior to 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.)