Influence of mastoid drilling on otoacoustic emissions of the nonoperated ear

Introduction: Drilling in mastoid surgeries can affect the nonoperated normal ear by transcranial transmission. This transient hearing loss can be assessed using distortion-product otoacoustic emissions (DPOAE). Objectives: To determine the effect of drilling on the DPOAE in the contralateral normal ear following mastoid surgeries and its relation with the duration of drilling. Study Design: This was a comparative, prospective, and case-control study. Materials and Methods: DPOAE was obtained for 20 patients who underwent mastoid surgery. DPOAE was measured at frequencies of 2, 3, 4, and 5 kHz with frequency ratio maintained at 1.22. DPOAE was recorded during the preoperative, immediate postoperative, 1st and 7th postoperative days. Twenty controls that underwent tympanoplasty were also analyzed pre- and post-operatively. Results: Significant deterioration in the DPOAE amplitudes was noticed during immediate postoperative period in all the four frequencies studied. No correlation was obtained between the duration of drilling and the change in amplitudes. Conclusion: A transient hearing loss is seen in the nonoperated ear following mastoid surgeries due to a drill-induced noise exposure.