Anatomy of the infralabyrinthine approach to the petrous apex

OBJECTIVE To study the anatomical dimension of the path to the petrous apex via the infralabyrinthine approach. METHODS Thirty dry temporal bones were dissected along the internal carotid canal. The distances from the vertical portion of the facial nerve to the genu of the internal carotid canal,the vertical portion of the facial nerve to the petrous apex,the genu of the internal carotid canal to the posterior surface of the petrous bone were measured. Ten heads of adult cadaver were dissected to gain access to the petrous apex via the infralabyrinthine approach. The horizontal and vertical dimensions of the approach window created were measured. RESULTS The vertical portion of the facial nerve to the lap of the internal carotid canal was (13.26±1.66)mm,portion of the facial nerve to the petrous apex was (34.48±1.07)mm,the lap of the internal carotid canal to the posterior surface of the petrous bone was (9.68±1.53)mm. The mean dimensions of the window in dissected bones were(5.76±3.38)mm vertically and (6.42±2.65)mm horizontally. Thirteen sides had been doing well with the infralabyrinthine approach. CONCLUSION The possibility of those anatomical variations should be considered when the infralabyrinthine approach is being planned to manage the petrous apex lesion. The infralabyrinthine approach is useful to the patients with good hearing.