A, Orbitozygomatic craniotomy and transcavernous approach to basilar apex. A, the inset (upper right) shows the scalp incision and the inset (lower right) shows the two-piece orbitozygomatic craniotomy. The frontal and temporal lobes have been retracted to expose the optic and oculomotor nerves and the anterior and middle cerebral and posterior communicating arteries. B, The exposure has been directed medially above the optic chiasm to the region of the anterior communicating artery. C, The carotid artery has been elevated to expose the basilar artery apex through the interval between the carotid artery and oculomotor nerve. The posterior clinoid process blocks access to the basilar artery. D, The anterior clinoid process and the roof of the cavernous sinus have been removed to provide access to the clinoid segment of the internal carotid artery and the posterior clinoid process. The upper dural ring extends medially from the upper margin of the anterior clinoid process. E, The posterior clinoid process has been removed to increase access to the upper portion of the basilar artery. F, The anterior part of the tentorial edge has been removed to expose the upper margin of the posterior trigeminal root in Meckel’s cave and to provide increased access to the upper part of the basilar artery. The trochlear nerve was preserved in opening the anterior part of the tentorial edge. Note the difference in the length of basilar arteries exposed in C and F. (Images courtesy of AL Rhoton, Jr.)