Evaluation of Sensorineural Hearing Loss Caused by Drill Burr (Types, Size and Speed of Drilling) In Ipsilateral and Contra Lateral Ear after Middle Ear Surgery

Abstract

Background and Objective- It has been observed that drilling during ear surgery can lead to noise induced sensorineural hearing loss in diseased and non-operated ear both. Hearing loss is caused by drill noise conducted to the non-operated ear by vibrations of the intact skull. This noise exposure results in dysfunction of the outer hair cells, which may produce hearing loss. Aim of our study is to evaluate the sensorineural hearing loss caused by various types of drill bit, various size of drill bit, speed of in diseased and non-operated ear during ear surgery. Method- Study design was prospective. Hearing assessment of all patients was done by tuning fork test and pure tone audiometry and patients with only mild, moderate and moderately severe conductive hearing loss were selected for study. Patients underwent middle ear surgeries like cortical mastoidectomy, radical mastoidectomy, modified radical mastoidectomy combined approached tympanoplasty and plain tympanoplasty after taking detailed informed consent. All patients underwent post-operative hearing assessment on 10 th post-operative day and after 2 months of operation. Result and Conclusions- Drilling at high speed (rpm) cause more sensorineural hearing loss thus according to our study best speed of drilling is 15000 rpm-25000 rpm. Larger sized burr produces more sensorineural hearing loss.always avoid the use of burrs of more than 7 mm size. We recommend use of <3 mm burr. Cutting burr produces more sensorineural hearing loss than diamond burr.