G, The sphenoid sinus has been opened to expose the septa within the sinus. The sphenopalatine arteries cross the anterior face of the sphenoid. H, The septa within the sphenoid sinus, the sellar floor, and the lateral sinus wall have been removed to expose the cavernous carotid arteries, pituitary gland, and optic canals. I, The clivus has been opened to expose the dura facing the brainstem. The basilar sinus, which interconnects the posterior parts of the cavernous sinus, is situated between the layers of dura on the upper clivus. J, The clivus has been opened to expose the tortuous vertebral arteries, which join to form the basilar artery at the left lateral margin of the clival opening. Both AICA origins are exposed. A vein splits the right abducens nerve into two bundles adjacent to the brainstem. K, The frontal dura has been opened and the frontal lobes elevated to expose the olfactory and optic nerves, the internal carotid, and the anterior and middle cerebral arteries. L, Enlarged view. The subfrontal and clival openings are separated by the sella and pituitary gland. The lateral limit of the clival exposure is defined by the internal carotid arteries and optic nerves. The lamina terminalis is exposed above the optic chiasm. (Images courtesy of AL Rhoton, Jr.)