A, The anterior end of the scalp incision is located near the midline behind the hairline. The posterior end is located at the zygomatic arch near the tragus. B, The scalp flap has been reflected downward using a subgaleal dissection. The fat pad, in which the facial nerve branches course, is exposed at the lower margin of the exposure. C, An incision through the superficial temporal fascia covering the lower part of the temporalis muscle allows the superficial fascia, with the fat pad that encloses the facial nerve branches, to be folded downward with the scalp flap. D, The keyhole, the site of a burr hole, which is located behind the anterior part of the superior temporal line, is outlined. The keyhole has the anterior fossa dura in its upper margin and the periorbita in its lower margin. The inset shows the burr holes and bone flap. E, The sphenoid ridge has been removed leaving a thin shell of bone over the roof and lateral wall of the orbit. The bone removal is extended downward to increase access to the middle fossa floor. F, The dura and sylvian fissure have been opened to expose the supra- and parasellar areas. The olfactory tract and the optic and oculomotor nerves are exposed. The posterior communicating and basilar arteries are seen through the opticocarotid triangle located between the optic nerve and carotid and anterior cerebral arteries. The posterior communicating artery courses medial to the oculomotor nerve in the suprasellar area. (Images courtesy of AL Rhoton, Jr.)