Tehran University Medical Journal

Background: The damaging effect of exposure to loud noise on the structures of internal ear has been studied from many years ago. The effect of drill-generated noise on the non-operated ear is one of the problems that are less discussed. This study aims to evaluate the hearing loss that occurs in the non-operated ear in patients who undergo mastoidectomy by use of PTA (pure tone audiometery) and DPOAE (distortion product otoacoustic emission).

Materials and Methods: In this descriptive- analytic study, 49 patients who underwent mastoidectomy in Amir-Alam and Iman Khomeini hospitals, were evaluated for noise trauma generated by drilling on the non-operated ear. Patients were between 9-55 years old (mean age= 29) and they consisted of 25 males and 24 females. The patient's preoperative state were measured by PTA and DPOAE on the opposite ear also the postoperative state were re-evaluated by PTA and DPOAE.

Results: As a result, in 4 cases a significant change in PTA thresholds were observed, while two of them showed recovery after one month. Seven cases showed significant change in DPOAE amplitudes, of whom five cases recovered later.

Conclusion: In conclusion, the drill-induced hearing loss on the non-operated ear occurs in a few patients and it is often reversible.