Petrous apex region. Surgical anatomy, lesions, and operative techniques.

The author describes the anatomy of the region of the petrous apex giving emphasis to the limits of surgical resection. The cochlea, located at the apex of the angle formed by the intersection of a line along the sphenopetrosal groove and a line from the facial hiatus to the internal auditory canal, has to be protected to preserve hearing. Surgical approaches can be divided in the posterior presigmoid approach that provides exposure to the posterior petrous bone and upper two thirds of the clivus, and the anterior subtemporal approach that provides exposure to the trigeminal ganglion, petrous carotid artery, Meckel's cave, and posterior cavernous sinus. Opening of Meckel's cave provides additional space for medial and inferior resection of the petrous apex. Two illustrative cases of primary petrous apex lesions are presented to demonstrate the surgical exposure obtained with each approach.