Early identification of hearing impairment in patients with type I diabetes mellitus

Objective: The aim of this study was to evaluate the cochlear micromechanic s and central auditory function in patients with type 1 diabetes mellitus a nd to identify the site of possible dysfunction. Methods: Cochlear activity was evaluated by recording distortion product ot oacoustic emissions (DPOAEs). DPOAEs were performed using an ILO 92 Otodyna mics Analyser. Functional changes in the retrocochlear auditory pathway wer e evaluated by auditory brainstem responses (ABRs). DPOAEs and ABRs were me asured in 42 normally hearing patients with type 1 diabetes mellitus aged 2 1 to 42 years. and 33 age- and sex-matched nondiabetic control subjects. Results: Both of the groups (diabetic and control) had normal and undiffere ntiated results in tonal and impedance audiometry. ABR peripheral transmiss ion time (wave I) and central trans mission rime (interpeak latencies I-V) were significantly delayed in the diabetic compared with normal subjects, a nd the mean amplitudes of various DPOAEs were significantly reduced in the diabetic patients compared with the control subjects. Conclusions: Combined use of different procedures for monitoring central an d peripheral portions of the auditory pathway in diabetic patients showed a lterations in cochlear micromechanics and the retrocochlear auditory pathwa y. Hearing impairment in diabetic patients is usually mild and subclinical, and can be detected early by accurate and objective audiometric methods.