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Year : 2018  |  Volume : 24  |  Issue : 2  |  Page : 95-97

Influence of mastoid drilling on otoacoustic emissions of the nonoperated ear

Department of Otorhinolaryngology, Yenepoya Medical College, Mangalore, Karnataka, India

Date of Web Publication4-Sep-2018

Correspondence Address:
Dr. Mubeena
Flat No.: 608, Meridiyen Apartments, Yenepoya Staff Quarters, Deralakatte, Mangalore, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/indianjotol.INDIANJOTOL_139_17

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Introduction: Drilling in mastoid surgeries can affect the nonoperated normal ear by transcranial transmission. This transient hearing loss can be assessed using distortion-product otoacoustic emissions (DPOAE). Objectives: To determine the effect of drilling on the DPOAE in the contralateral normal ear following mastoid surgeries and its relation with the duration of drilling. Study Design: This was a comparative, prospective, and case–control study. Materials and Methods: DPOAE was obtained for 20 patients who underwent mastoid surgery. DPOAE was measured at frequencies of 2, 3, 4, and 5 kHz with frequency ratio maintained at 1.22. DPOAE was recorded during the preoperative, immediate postoperative, 1st and 7th postoperative days. Twenty controls that underwent tympanoplasty were also analyzed pre- and post-operatively. Results: Significant deterioration in the DPOAE amplitudes was noticed during immediate postoperative period in all the four frequencies studied. No correlation was obtained between the duration of drilling and the change in amplitudes. Conclusion: A transient hearing loss is seen in the nonoperated ear following mastoid surgeries due to a drill-induced noise exposure.

Keywords: Distortion-product otoacoustic emissions, mastoidectomy, nonoperated ear, sensorineural hearing loss

How to cite this article:
Badarudeen S, Mubeena, Somayaji G. Influence of mastoid drilling on otoacoustic emissions of the nonoperated ear. Indian J Otol 2018;24:95-7

How to cite this URL:
Badarudeen S, Mubeena, Somayaji G. Influence of mastoid drilling on otoacoustic emissions of the nonoperated ear. Indian J Otol [serial online] 2018 [cited 2021 Jul 30];24:95-7. Available from: https://www.indianjotol.org/text.asp?2018/24/2/95/240567

  Introduction Top

Drilling forms an important component of mastoid procedures. In the contralateral normal ear, drilling can result in a transient hearing loss by transcranial transmission. The transcranial attenuation of sound conducted through bone is considered to be low during transmission through the bone.[1],[2] These factors imply the possibility of an acoustic trauma to the contralateral cochlea. Acoustic trauma initially targets outer hair cells (OHCs) resulting in reduced otoacoustic emissions when damaged. Hence, transient hearing loss in the nonoperated ear can be better assessed using distortion-product otoacoustic emissions (DPOAE) which helps in rapid assessment of the OHC function.

  Materials and Methods Top

The study was undertaken following approval from the Institutional Ethical Committee. Written and informed consent was obtained from all the patients included in the study. In this comparative, prospective, case–control study, twenty patients who underwent mastoid procedures, namely modified radical mastoidectomy or cortical mastoidectomy, were enrolled from the Department of Otorhinolaryngology over a period of 1 year. Simultaneously, 20 patients following tympanoplasty were taken up as controls. Patients with normal otoscopic findings, pure-tone audiometry, and DPOAE values in the contralateral ear in both the groups were included in the study. Patients with bilateral middle ear disease are excluded from the study. Hearing assessment of patients in the study groups was done using DPOAE measurements recorded during the preoperative, immediate postoperative periods, and during the 1st and 7th postoperative days. Controls were evaluated using two recordings of DPOAE taken during the preoperative and immediate postoperative periods. DPOAE amplitudes were recorded using neuro-audio measuring device for four different frequencies of 2, 3, 4, and 5 kHz with f1 and f2 delivered at a constant frequency ratio f1/f2 of 1.22. All mastoid surgeries were done with MIO micromotor (35,000 rpm; Nakanishi, INC., Tochigi, Japan) drill system with both cutting and diamond burrs. Duration of drilling in mastoid cases was also accounted for and used for comparison with DPOAE in different time periods. The results obtained were statistically analyzed using paired t-test and independent t-tests. The operated ear was not evaluated using DPOAE as the presence of blood in the postoperative cavity could alter the readings.

  Results and Analysis Top

The study analyzed 20 patients, 12 males and 8 females, who were taken up for mastoid surgeries. Among the study population, 10 patients were diagnosed as unsafe otitis media and underwent modified radical mastoidectomy while the other 10 patients had undergone cortical mastoidectomy with tympanoplasty for active mucosal type of disease. Depending on the type of surgery undertaken, duration of drilling ranged from 60 to 180 min in these patients. Duration of drilling in cortical mastoidectomy was up to a maximum of 90 min while modified radical mastoidectomy was longer ranging up to 180 min.

On assessment of the study population, a significant difference was noticed in the immediate postoperative period in all frequencies as depicted in [Figure 1]. This difference obtained during the immediate postoperative period was found to be statistically significant. Maximum changes in the DPOAE values were noticed at a frequency of 4 kHz in these patients. A significant change in DPOAE was not detected in the 1st postoperative day in comparison to DPOAE immediately after surgery. Recovery in the DPOAE values was noticed by the 7th postoperative day with significant difference obtained at 2 and 5 kHz.
Figure 1: Change in the distortion-product otoacoustic emission amplitudes between the pre- and post-operative periods

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On comparison of DPOAE with the duration of drilling, no significant correlation was obtained in any of the frequencies during the postoperative periods for all patients. It was observed that deterioration in the amplitudes in the immediate postoperative period in comparison to preoperative values was more in patients with increased drilling time of >60 min, but a statistically significant change could not be obtained [Figure 2].
Figure 2: Change in distortion-product otoacoustic emission amplitudes with duration of drilling for 2 kHz

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In the control group, obvious change could not be detected between the preoperative and immediate postoperative amplitudes in any of the frequencies.

  Discussion Top

Noise generated from the drill has the potential to cause sensorineural hearing loss in the operated and the contralateral ear.[3],[4],[5] Drill-related hearing loss in the operated ear could be due to acoustic trauma, drill touching the ossicles, or manipulation of the stapes footplate during surgery. In the contralateral normal ear, a transient sensorineural hearing loss is expected following drill-related ear surgeries as proposed by Lela Migirov and Michael Wolf, who were able to notice alterations in 9 out of the 13 patients during the postoperative period. Involvement of the nonoperated ear can be explained by the transcranial transmission of the noise generated by the drill.[5]

The nonoperated ear is expected to be exposed to noise which is about 5–10 dB less than the exposure to the operated ear due to negligible interaural attenuation of sound.[6] Kylén and Arlinger were able to determine that the operated ear was exposed to noise levels of about 100 dB and more, thus indicating an almost similar level of exposure in the nonoperated ear.[1] They also depicted that the speed of the drill or site of drilling did not affect the noise exposure. The noise exposure in the contralateral ear was detected to be in excess of 90 dB according to the study by Hickey and O'Connor.[7] However, previous studies based on audiometry by Urquhart et al. and Hornung and Ostfeld had not observed any significant hearing loss during the postoperative period.[8],[9],[10],[11]

In the current study, the effect of drill-generated noise on the nonoperated normal ear was studied using DPOAE which gave an assessment of the OHCs likely to be damaged during noise exposure. OAE measurements have the capability to differentiate the mild variations in the cochlea on exposure to noise.[12] The study was able to detect deterioration in the DPOAE values at all frequencies studied during the immediate postoperative period with maximum variation seen at 4 kHz. This evaluation was in accordance with the assessment done by Shenoy et al., who demonstrated a reduction in the DPOAE postoperatively in the normal ear in 45 patients.[4] They were able to observe maximum change in the frequencies of 2 and 4 kHz. This observation was also made by Migirov and Wolf where variations were noticed only at 2 and 4 kHz, stating this depiction to be related to the sensitivity of the tonotopical areas of the cochlea to the drilling.[5] They stated that DPOAE changes following mastoidectomy may be due to the increased permeability of blood vessels of the stria vascularis and resultant injury to the organ of Corti from vibrations of the temporal bone. da Cruz et al. detected a transient, reversible change in amplitudes only in two patients postoperatively among the 12 patients studied.[13] Similar changes in the normal ear were also obtained on studying the transient-evoked OAEs by Ferber-Viart et al.[14]

In the present study, we were able to observe a recovery in the DPOAE amplitudes in the 7th postoperative day in comparison to the previous values, in majority of the patients. The values were still in the recovering stage in the 7th postoperative day and had not reached the preoperative values. The recovery was noticed during the 1st postoperative day with complete recovery by the 7th day in previous studies.[4] Complete recovery was observed in 72 h by Karatas et al.[15]

Migirov and Wolf concluded that the values obtained in the 1st postoperative day were still in the recovery stage and attained complete recovery by the end of 4 weeks which could explain the recovering values in postoperative day 7 in our study.[5] In some patients, they were able to demonstrate an initial improvement in the DPOAE amplitudes in the 1st postoperative day followed by a deterioration which remained reduced till the end of the study. This finding was also observed in 6 patients in the current study.

The duration of drilling was also determined in this study and compared with the DPOAE amplitudes. We were unable to observe any statistically significant relation between the time taken for drilling and the values on DPOAE. It was observed that deterioration in the amplitudes postoperatively was more with increase in the duration of drilling in >50% of the patients but was not statistically significant. The study by Palva and Sorri on the nonoperated ears in patients who underwent mastoidectomy demonstrated that hearing loss occurred more frequently and more severely in patients with increased drilling times. Similar observations were also seen in previous studies.[4],[16]

  Conclusion Top

In conclusion, from our study, we were able to ascertain the presence of a transient hearing loss immediately following surgery in patients undergoing mastoidectomy, which began to show recovery by the 7th postoperative day. This could be explained as the effect of the drill-induced noise exposure. This transient reduction in hearing failed to show any direct correlation with the time taken for drilling. Complete recovery was not observed in this study by the 7th postoperative day; hence, long-term hearing follow-up of these patients is warranted.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Kylén P, Arlinger S. Drill-generated noise levels in ear surgery. Acta Otolaryngol 1976;82:402-9.  Back to cited text no. 1
Holmquist J, Oleander R, Hallén O. Peroperative drill-generated noise levels in ear surgery. Acta Otolaryngol 1979;87:458-60.  Back to cited text no. 2
Doménech J, Carulla M, Traserra J. Sensorineural high-frequency hearing loss after drill-generated acoustic trauma in tympanoplasty. Arch Otorhinolaryngol 1989;246:280-2.  Back to cited text no. 3
Shenoy VS, Vanka S, Rao RA, Prasad V, Kamath PM, Bhat J, et al. Effect of mastoid drilling on the distortion product otoacoustic emissions in the non operated ear. Am J Otolaryngol 2015;36:832-6.  Back to cited text no. 4
Migirov L, Wolf M. Influence of drilling on the distortion product otoacoustic emissions in the non-operated ear. ORL J Otorhinolaryngol Relat Spec 2009;71:153-6.  Back to cited text no. 5
Man A, Winerman I. Does drill noise during mastoid surgery affect the contralateral ear? Am J Otol 1985;6:334-5.  Back to cited text no. 6
Hickey SA, O'Connor AF. Measurement of drill-generated noise levels during ear surgery. J Laryngol Otol 1991;105:732-5.  Back to cited text no. 7
Urquhart AC, McIntosh WA, Bodenstein NP. Drill-generated sensorineural hearing loss following mastoid surgery. Laryngoscope 1992;102:689-92.  Back to cited text no. 8
Hornung S, Ostfeld E. Bone conduction evaluation related to mastoid surgery. Laryngoscope 1984;94:547-9.  Back to cited text no. 9
Hallmo P, Mair IW. Drilling in ear surgery. A comparison of pre- and postoperative bone-conduction thresholds in both the conventional and extended high-frequency ranges. Scand Audiol 1996;25:35-8.  Back to cited text no. 10
Tos M, Trojaborg N, Thomsen J. The contralateral ear after translabyrinthine removal of acoustic neuromas: Is there a drill-noise generated hearing loss? J Laryngol Otol 1989;103:845-9.  Back to cited text no. 11
Hall AJ, Lutman ME. Methods for early identification of noise-induced hearing loss. Audiology 1999;38:277-80.  Back to cited text no. 12
da Cruz MJ, Fagan P, Atlas M, McNeill C. Drill-induced hearing loss in the nonoperated ear. Otolaryngol Head Neck Surg 1997;117:555-8.  Back to cited text no. 13
Ferber-Viart C, Duclaux R, Dubreuil C, Colleaux B, Sanlaville N. Transient evoked otoacoustic emissions in nonsurgical ear. Int J Neurosci 1996;86:207-16.  Back to cited text no. 14
Karatas E, Miman MC, Ozturan O, Erdem T, Kalcioglu MT. Contralateral normal ear after mastoid surgery: Evaluation by otoacoustic emissions (mastoid drilling and hearing loss). ORL J Otorhinolaryngol Relat Spec 2007;69:18-24.  Back to cited text no. 15
Palva A, Sorri M. Can an operation of deaf ear be dangerous for hearing? Acta Otolaryngol Suppl 1979;360:155-7.  Back to cited text no. 16


  [Figure 1], [Figure 2]

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