Surgical anatomy of the transcanal infracochlear approach.

Abstract

The objective of this study is to describe the detailed surgical anatomy of the infracochlear approach to prevent complications and to compare the postauricular transcanal microscopic and endoscopic approaches to reach the petrous apex. Cadaver heads were dissected using a binocular surgical microscope, endoscopes, and an electric drill. The dimensions of the access field that could be reached and manipulated with surgical instruments and straight drill via postauricular transcanal microscopic and endoscopic approaches were evaluated. Both postauricular microscopic and transcanal endoscopic approaches were considered to be inapplicable in cases with a tympanic cavity located jugular bulb closer than 3mm to the cochlea. This relationship was seen in 3 (9%) sides of the cadavers. In 4 specimens (12%), a cochlear aqueduct with an open lumen was detected. Both postauricular microscopic and transcanal endoscopic approaches reached a nearly identic dissection area. Detailed anatomy of the approach and measurements about the topography of the third portion of the facial nerve from the tympanic cavity were presented. Both traditional microscopic postauricular and endoscopic transcanal approaches provided comparable access areas to the inferior petrous apex with wide exposure, and radiologic measurements were compatible. A tympanic cavity located jugular bulb in close relation with cochlea was the only instance that restricted the applicability of this technique.