Evaluation of Sudden Deafness Utilizing Evoked Otoacoustic Emissions

Abstract

To identify the damaged cochlear region which might be responsible for sudden deafness (SD), pure tone audiometry and evoked otoacoustic emissions (EOAEs) were studied during treatment of patients with SD. Measurement was carried out once a week as a rule until hearing level was fixed. The patients with SD were classified into four (complete, prominent, partial recovery and unchanged) groups according to the degree of hearing improvement. At the initial measurement, the pure tone hearing levels and minimum detectable levels of EOAEs were mostly well matched in the complete recovery group while the former elevated more than in the other incomplete recovery groups. Using a linear regression analysis, the complete recovery group had a moderate correlation between them during the clinical course. Also correlation was found in the prominent and partial recovery groups in some degree while no correlation was found in the unchanged group, and even discrepancy was seen in some cases. These complicated results suggested multiple involvement of cochlea regions in SD. These damages seemed to exist sole or combined influence to the outer hair cells (OHCs) which are the generator of EOAEs in various extent. Main damaged region in SD seemed to be OHCs in the complete recovery group while multiple regions of the cochlea in the other groups even with a possibility of central part.