Aided Air Conduction Threshold as a Predictor of Cochlear Reserve in Otosclerosis Patients

Abstract

Otosclerosis classically presents with conductive deafness. However, mainly in older patients or those with a progressive (active) form of this disease, it presents with elevated bone conduction (BC) thresholds. In many cases, an elevation in the BC threshold during otosclerosis is not a true indicator of ‘cochlear reserve’ and this apparent loss can be corrected by surgery. It is generally accepted that in those patients, elevated BC thresholds are not due to pure sensorineural hearing loss but to the Carhart effect. Speech discrimination tests are routinely done, and the results of these tests determine if a patient is a good candidate for surgery. In most institutions, those with poor speech discrimination scores are considered to be poor candidates due to inadequate cochlear reserve. Using hearing-aid-assisted pure-tone audiometry, we developed an accurate method to identify suitable candidates for surgery among the patients with elevated BC thresholds. This method is meant to complement speech discrimination tests in predicting the success of surgery in those patients. Different variables render speech discrimination tests unreliable in many patients. The rationale behind the current study was the lack of an easy and accurate clinical method to determine if a patient has a good cochlear reserve, and to predict the postoperative hearing threshold outcome.