Influence of drilling on the distortion product otoacoustic emissions in the non-operated ear.

OBJECTIVE

To determine possible changes in the outer hair cell (OHC) function related to drill noise exposure.

METHODS

Distortion product otoacoustic emissions (DPOAE) were measured at frequencies of f(2) = 2, 3, 4 and 5 kHz, and a frequency ratio f(1)/f(2) = 1.22. The f(1) and f(2) levels were delivered at 65 dB SPL. DPOAE amplitudes were compared in 13 patients both before and after mastoidectomy, and between these patients and 5 patients who underwent tympanoplasty.

RESULTS

The DPOAE amplitudes were significantly decreased at 2 and 4 kHz (p = 0.01 and p = 0.013, respectively) immediately after the mastoidectomy, and still differed from the preoperative results at these frequencies on the first post-mastoidectomy day. After the various individual fluctuations, the DPOAE amplitudes remained decreased in some of the patients at the end of the study.

CONCLUSIONS

Drill-induced noise during mastoidectomy can cause reversible changes in DPOAE in the non-operated ear. OHC function may be diminished during the period after mastoid surgery, and last >1 month.