Effect of Drill Induced Noise on Contralateral Normal Ear Following Cortical Mastoidectomy

Chronic suppurative otitis media (CSOM) is a long standing infection of the middle ear cleft. Mastoidectomy, with or without tympanoplasty, is the preferred treatment for CSOM. However, the drill used during ear surgery generates noise that may potentially cause hearing damage in both the operated and opposite inner ear, leading to temporary or permanent hearing loss.

The study included patients diagnosed with CSOM who underwent surgeries in the Otorhinolaryngology department. Postoperatively, all patients were followed up on the 7th day and 1 month after the surgery. Pure Tone Audiometry (PTA) was performed to evaluate the hearing outcomes.

A total of 61 patients were included in the study. The mean preoperative PTA of contralateral ear bone conduction among the study participants was 6.48. At the 7th day post-operation, the mean post-operative PTA of contralateral ear bone conduction for the same participants was 7.77. This difference was statistically significant according to the Paired T-test (P = 0.001).However, when evaluating the mean preoperative PTA of contralateral ear bone conduction (6.48) and the mean post-operative PTA at 1st month (6.02), the difference was not statistically significant (P = 0.208).Additionally, there was no statistical difference in air conduction and air-bone gap before and after surgery.

The study suggests that mastoid drilling is associated with a significant temporary hearing loss in the contralateral ear immediately after surgery, which eventually recovers within a month. However, the hearing loss is considered negligible and not statistically significant in the long term. It is worth considering additional audiological investigations, such as otoacoustic emissions, to detect this type of hearing loss more accurately.