Cochlear line: a novel landmark for hearing preservation using the anterior petrosal approach

The goal of this study was to develop a practical landmark for the safe and easy identification of the cochlea when performing anterior petrosectomy based on cadaver dissection results.The cochlear line was defined as the line drawn from the crossing point between the greater superficial petrosal nerve (GSPN) and the petrous internal carotid artery to the line drawn over the apex of the superior circumference of the dura of the internal auditory canal at a right angle. The validity of the cochlear line marking the anteromedial perimeter of the cochlea at the angle of the GSPN and the internal acoustic canal as a practical landmark were evaluated using 5 cadaver heads.The mean distance (± SD) measured from the cochlear line to the margin of the cochlear cavity was 2.25 ± 0.51 mm (range 1.50-3.00 mm).Anterior petrosectomy can be performed more efficiently by using the cochlear line as a key landmark to preserve the cochlea.