Using the Arcuate Eminence-Trigeminal Notch Line to Localize the Anterior Wall of the Internal Auditory Canal in a Subtemporal Approach: An Anatomical Study.

Background  This article aims to describe the regional anatomy of the anterior end of the arcuate eminence, the lateral end of the trigeminal notch, and the line connecting the two (i.e., the arcuate eminence-trigeminal notch line [ATL]) and to determine whether the ATL could be used as a landmark for localizing the internal auditory canal (IAC). Methods  Twenty sides of the middle cranial fossae were examined. The anterior end of the arcuate eminence, the lateral end of the trigeminal notch, the ATL, and other crucial structures were exposed. The relevant distance and angle of related structures in the anterior wall of the petrosal bone were measured. Results  The anterior end of the arcuate eminence and the lateral end of the trigeminal notch could be identified in all specimens. The anterior end of the arcuate eminence lay over the geniculate ganglia and the vestibule area, and could be visualized directly or determined from the intersection of the long axes of the greater superficial petrosal nerve and arcuate eminence. On the petrous ridge, the lateral end of the trigeminal notch was also the transitional point of the suprameatal tubercle and trigeminal notch. The ATL corresponded to the projection of the anterior wall of the IAC on the anterior surface of the petrous bone. Conclusion  The ATL corresponded to the projection of the anterior wall of the IAC on the anterior petrous surface and could be used as an alternative landmark for localizing the anterior wall of the IAC.