OBJECTIVETo investigate the safety range of drilling and fenestration on promontory inferior to the oval window in difficult stapedectomy via anatomical study of the relationship between the inferior margin of oval window and the endosteum of basal cochlear turn.

METHODSBy means of histological sections, the distances between the inferior margin of oval window and different locations of endosteum of basal cochlear turn, the corresponding height of the projecting endosteum and the thickness of promontory bone, on three vertical sections through the anterior, posterior and midpoint of the inferior edge of oval window were measured respectively.

RESULTSThe promontory bone inferior to the posterior point of the oval window was thickest, with an average thickness of about 1.1 mm. The endosteum of basal turn at this portion was lowest, with an average height of 0.2 mm. Furthermore, the shortest distance here between the inferior edge of oval window and the endosteum could be no more than 0.3 mm.

CONCLUSIONRelatively safe location of drilling on promontory should be selected on promontory inferior to the posterior point of the oval window, with the direction of drilling outward and downward.

Cochlea ; anatomy & histology ; Humans ; Oval Window, Ear ; anatomy & histology ; Stapes Surgery

Conductive hearing loss is a condition that can be corrected surgically in most cases. Stapedotomy is usually performed for patients with congenital ossicular anomaly or fixation. However, otologic surgeons have often encountered difficulty due to the complexity of stapes surgery. Moreover, congenital stapes fixation with anomalous facial nerve and oval window absence is an uncommon and dangerous condition. In such cases, vestibulotomy can be a surgical option to prevent facial nerve damage and improve hearing. The etiology can be explained by the embryological development of the middle ear structures. To prevent facial nerve damage and maximize the efficacy of surgery, the surgeon should have knowledge about this disease and take a computed tomography for double check before stapes surgery. We describe a case of congenital stapes fixation with aberrant facial nerve courses, a 15-year-old female who was treated with vestibulotomy and piston wire insertion.
Adolescent ; Ear, Middle ; Facial Nerve* ; Female ; Hearing ; Hearing Loss, Conductive ; Humans ; Oval Window, Ear ; Stapes Surgery ; Stapes* ; Surgeons