The anatomy of facial nerve decompression through transmastoid,extralabyrinthine,subtemporal approach

Objective To validate the feasibility and security of the facial nerve decompression through transmastoid extralabyrinthine subtemporal approach To get the data about this approach. Methods Under the operation microscope 20 adult temporal bones and 20 sides of cadaveric skulls were dissected through transmastoid extralabyrinthine subtemporal approach . Various distances of facial nerve and key mark were measured. Results 20 adult temporal bonesSD 1 the distance between choleariform process and the angle point of proximal end to distal end in geniculate ganglion was3.80±0.72 mm. 2 the length of horizontal segment was 11.14±0.73 mm.3 the length of labyrinthine segment was 3.35±0.68 mm. 4 the distance between basal turn of the cochlea and the labyrinthine segment was 1.04±0.14 mm. 5 the tegmen thickness in most distal point of labyrinthine segment was 2.82±0.64 mm. 6the shortest distance between facial canal in horizontal segment and the lateral semicircular canal was 1.27±0.21 mm.7the distance between facial canal in horizontal segment and middle point of anterior semicircular canal ampulla was 2.47±0.21 mm. 20 sides of cadaveric skullsSD 1the distance between long process of incus and horizontal segment was 2.33±0.26 mm. 2 the distance between short process of incus and facial nerve was 3.06±1.01 mm. 3 the distance between capitulum of malleus and the horizontal segment was 2.17±0.87 mm. 4 the distance between capitulum of malleus and tegmen tympani was 2.31±0.87 mm. 5 the length of vertical segment was 16.27±0.58mm. 6the angle of proximal end to distal end in geniculate ganglion was 74.3±2.47°. 7 7the angle of pyramidal segment was 110.2±8.30°. Conclusion This study provided the safe scope manipulation room and the angle of the transmastoid extralabyrinthine subtemporal approach and these data can be reference for the surgeon.