Effect of drill-induced noise on hearing in non-operated ear

BACKGROUND: The aim of this study was to evaluate the effect of drill-generated noise on hearing loss in non-operated ear and if any, was temporary or persistent. MATERIALS AND METHODS: In this prospective clinical study, 23 patients who had undergone mastoidectomy and normal contralateral hearing were enrolled. Patients were evaluated preoperatively and postoperatively (1 and 7 days) following surgery using low and high-frequency pure tone audiometry (PTA) and low and high-frequency transient evoked and distortion product otoacoustic emission (DPOAE) testing. RESULTS: Comparing preoperative and 1-day after surgery, PTA averages were significantly different at low frequencies, but no statistical significant differences were observed at 0.25 KHz and high-frequencies. Comparing 1-day after surgery and 7 days after surgery showed that, PTA averages at 0.5, 2 and 2 KHz were significantly different with no significant differences at the other average of thresholds in low and high frequencies; PTA average at 1 KHz was significantly different with, no significant differences at the other averages of thresholds in low and high frequencies. DPOAEs showed a significant difference preoperative and 1-day after surgery, 1-day and 7 days after, but DPOAEs were not significantly different. Transiently evoked otoacoustic emissions (TEOAEs) had a significant difference preoperative and 1-day after surgery, 1-day and 7 days after but when comparing preoperative and 7 days after surgery, TEOAEs were not significantly different. CONCLUSIONS: Drill-induced noise during ear surgery (mastoidectomy) can cause reversible changes in PTA, DPOAEs and TEOAEs in the non-operated ear.