Surgical Anatomy of the Infralabyrinthine Approach

Objective The objective of this study is to demonstrate the surgical anatomy of the infralabyrinthine approach (ILA) and ways to prevent complications based on the complex anatomy. Study Design Cadaveric study. Setting Ankara University Faculty of Medicine, Department of Anatomy. Subjects and Methods Temporal bones were selected from 30 sides of 20 fixed human cadaver heads. Computed tomography (CT) scans of the heads were performed and, afterward, the cadavers were dissected using a surgical microscope and electric drill. Results An appropriate tract could be achieved in 73.3% of the dissections by applying slight pressure to the jugular bulb (JB). The narrowest portion of the ILA was defined as the inner window, which was located superior-inferiorly between the inferior border of the cochlea and the inferior wall of the petrous apex and anterior-posteriorly between the posterior wall of the carotid canal and the cochlear opening of the cochlear aqueduct. The ILA could not be performed when the distances between the facial nerve-JB and JB-cochlea were less than 2.9 mm and 2.6 mm, respectively, on CT scan. Conclusion Close attention should be paid to the access and inner window during preoperative temporal bone imaging to assess for ILA. The detailed anatomy of the route, measurements of the topography of the cochlea from the mastoid view, and angles of the route are defined to prevent complications.