Figure 1: The TL approach is summarized. The spine of Henle at the posterosuperior margin of the external meatus (inset image) is a superficial landmark that estimates the deep location of the lateral semicircular canal and the tympanic segment of the facial nerve. The mastoidectomy has been completed and the dural venous sinuses and the facial nerve are skeletonized while a thin layer of bone is left over them. The semicircular canals are apparent. The dura, bounded by the sigmoid and superior petrosal sinuses, the jugular bulb, and the labyrinth, is the Trautmann triangle (left upper image). The tympanic segment of the facial nerve courses between the lateral canal and the stapes in the oval window, and then turns inferiorly as the mastoid segment (right upper image). The semicircular canals and vestibule have been resected and the dura covering the IAC has been incised to expose the cranial nerve (CN) VII/VIII complex (left lower image). The dura has been further resected to reveal the CP angle. The limits of the exposure include an anteriorly positioned sigmoid sinus, a high-riding jugular bulb, or a low middle fossa plate. The jugular bulb may be situated as high as the posterior wall of the IAC and be found at the posterior meatal wall during the TL and RS approaches. (Images courtesy of AL Rhoton, Jr.)