Does Drilling Induce Hearing Loss after Modified Radical Mastoidectomy? A Retrospective Study

Abstract

Introduction
Incidence of sensory neural hearing loss following mastoid surgery varies from 1.2 – 4.5%.There are various causes for postoperative sensorineural hearing loss during mastoid surgery. This study aims to identify whether there is any correlation between drilling and postoperative sensory neural hearing loss.

Methods
A retrospective study was conducted in the Department of ENT from January 2018 to June 2019. A total number of 68 patients above five years of age who underwent modified radical mastoidectomy for chronic otitis media squamous were included. Revision surgery, preoperative sensorineural hearing loss, injury to the ossicular chain during surgery, patients with lack of follow up or doubtful reports in mentally challenged were excluded from the study. The average bone conduction threshold was calculated from 500, 1000, 2000, 4000 Hz and compared using the Wilcoxon signed-rank test.

Results
There were 43 males and 25 females in the study with a median age of 23.5 years (16-55). The mean preoperative bone conduction threshold in the four frequencies of 500 Hz, 1kHz, 2kHz, 4kHz were -2.06dB, -2.06dB, 3.31dB, 4.63 dB respectively and the mean postoperative bone conduction thresholds were 1.03, 1.32, 5.29, 4.04 respectively. There was a decline of mean of 3.09 dB and 3.38dB only at the low-frequencies (500Hz and 1kHz) BC threshold respectively which were statistically significant, whereas at higher frequency there was no decline in average postoperative BC threshold.

Conclusion
There is no definite role of drill in inducing hearing loss and if present other causes of hearing loss should be sought in postoperative sensorineural hearing loss.