In this study we evaluated the cochlear function in patients with diabetes mellitus by pure tone audiometry and transient otoacoustic emission (TOAE) test technique. Diabetic patients showed significant sensor neural hearing loss in both low and high frequencies of sound compared to control subjects on pure tone measurements. TOAEs by low and high frequency bands in diabetic patients were significantly lower than the controls. In 9 of 26 patients (34.6 %) with pure tone thresholds under 30 dB, surprisingly otoacoustic emissions (OAE) were not determined both in low and high frequencies. Our results indicate that diabetic sensor neural hearing loss results from dysfunction of outer hair cells (OHC). The OAE test specifically reflects the function of OHCs. The test is sensitive in the early stages of hearing impairment in diabetes mellitus.
Keywords: Diabetes mellitus, hearing loss, otoacuostic emissions