Effects of Drilling in Mastoid Cavity over Hearing in the Contralateral Ear

In advanced otological surgeries, powered instruments form an indispensable part. The risk of deterioration to hearing in the operated ear is a commonly discussed issue, however, there remains a possibility of affecting the hearing in the contralateral ear due to transcranial vibration. So in this study we aimed to assess the possibility of the non-operated ear being affected by the noise generated during ear surgeries and whether it is temporary or permanent in nature. Methodology: This study included 63 patients diagnosed with unilateral disease who underwent mastoid surgery. Preoperatively all the patients were subjected to Pure tone audiometry (PTA), Transient evoked otoacoustic emission (TEOAE) and Distortion product otoacoustic emission (DPOAE). Patients were operated using both cutting and diamond burrs of ranging from sizes 1 - 6 mm. Total drilling time was recorded. Results: Post-operative hearing evaluation was done at 1 week, 4 weeks and 12 weeks. The sound emitted by various burrs was recorded by Sound Level Meter. Out of the total 58 patients that followed up, 46 showed change in at least one of the hearing parameters. Patients showing changes had a higher drilling time as compared to those with no changes. Of these, the changes associated with the total drilling time and with cutting burr time were found to be significant. The hearing changes seen on PTA, TEOAE and DPOAE were transient in nature with only one patient having a persistent decreased high frequency threshold at the end of 12 weeks. It was also found that cutting burrs produce more sound as compared to diamond burrs and a larger size burr of a type produces more sound than a smaller one of its type. Conclusion: The drilling of mastoid bone during ear surgeries can transiently impair the hearing in the contralateral ear which is of great significance in patients with only one hearing ear.

Audiological characteristics of the contralateral ear in patients with unilateral physical non-explosive ear trauma

Objectives:To document the frequency of occurrence and types of symptoms experienced in the contralateral ear in patients with unilateral physical non-explosive(UPN)ear trauma and to compare the audio metric and tympano metric parameters between asymptomatic and symptomatic contralateral ears.Design:Prospective analytical clinical study Setting:Specialized(Ear,Nose,and Throat)clinic of a tertiary health institution.Participants:Patients with UPN ear trauma who presented within the first week of the incident.Main outcome measures:Otologic symptoms in the contralateral ear in UPN ear trauma Results:Eighteen out of 53 patients(34.0%)experienced symptoms in the contralateral ear.The symptoms were tinnitus in 77.8%(14/18),hearing loss in 66.7%(12/18),and ear blockage in 27.8%(5/18).There was hearing loss in 38/53(71.7%)of contralateral ears.Hearing loss type and PTAv at the low frequencies were not significantly different(p=0.142),but other audiometric parameters were significantly different between asymptomatic and symptomatic contralateral ears(p<0.05 in all).Type C tympanogram was more prominent in the symptomatic contralateral ear.There was a statistically-significant difference in the type of tympanogram between the two categories of patients(p=0.018).There was no difference in acoustic reflex between the two categories of patients(p=0.095).Conclusions:The contralateral ear may be affected in up to one-third of patients with UPN ear trauma,and experience otologic symptoms similar to those of the traumatized ears.Audiologic and audiometric parameters were abnormal in most of the contralateral ears.The two ears must be assessed thoroughly in cases of UPN ear trauma.