Applied anatomy of the modified translaryrinthine approach to the internal auditory canal surgery

Objective To study surgical methods of preserving facial nerve and audition, and to provide anatomic parameters and anatomic markers for removal of acoustic tumor via the modified translaryrinthine approach. Methods The removal of acoustic tumor via the modified translaryrinthine approach was simulated on 20 adult cadaveric heads, in each surgery the bow of the posterior semicircular canal and superior semicircular canal was removed, and the ampulla of the posterior semicircular canal and superior semicircular canal, and the lateral semicircular canal as well as the vestibule was kept. The length of the exposed internal auditory canal and the range of the operative field were measured. Results The shortest distance from the ampulla of the superior semicircular canal to the duramater inside the sigmoid sinus was ( 10.4 ± 2.0 ) mm, from the posterior margin of the lateral semicircular canal to the duramater inside the sigmoid sinus ( 6.4 ± 1.0 ) mm, from the duramater of the middle cranial fossa to the jugular bulb ( 13.8 ± 3.3 ) mm, the exposed length of the internal auditory canal was ( 5.8 ± 0.9 ) mm, which was 60.4% of its full length. Conclusion The operative field of the interior part of the internal auditory canal and the cerebellopontine angle can be obtained via the modified translaryrinthine approach satisfactorily; and at the same time, it was possible to preserve audition, and the posterior inferior margin of the lateral semicircular canal can be used as a marker for searching the internal auditory canal.