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Effect of mastoid drilling on the distortion product otoacoustic emissions in the non operated ear
AM ER IC AN JOURNAL OF OT OLA RYNGOLOGY– H E A D A N D NE CK M E D ICI N E AN D S U RGE RY 3 6 (2 0 1 5) 8 32 – 8 3 6
Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/amjoto
Original contribution
Effect of mastoid drilling on the distortion product otoacoustic emissions in the non operated ear Vijendra S. Shenoy, MS⁎, Siddharth Vanka, MS, Raghavendra A. Rao, MS, Vishnu Prasad, MS, Panduranga M. Kamath, MS, Jayashree Bhat, PhD Dept of ENT and Head & neck surgery, Kasturba Medical College, Manipal University, Mangalore, India
ARTI CLE I NFO
A BS TRACT
Article history:
Objective: To monitor the effect of mastoid drilling on the non-operated ear distortion
Received 9 May 2015
product otoacoustic emissions. Materials and methods: Distortion product otoacoustic emissions (DPOAEs) were measured at frequencies of f 2 = 2, 3, 4 and 5 kHz, and a frequency ratio f 1 /f 2 = 1.22. DPOAEs were measured in 49 cases, pre and post-operatively who underwent mastoid drilling procedures, compared
with each
other
and with 49 controls who underwent
myringoplasty and myringotomy procedures. Results: Amplitudes of DPOAEs decreased significantly in those who underwent mastoidectomies over all the measured frequencies in the immediate post-operative period but had recovered by the seventh post operative day. Conclusion: Drill induced noise can cause temporary decrease in the DPOAEs postoperatively and hence temporary hearing loss for a period of one week. © 2015 Elsevier Inc. All rights reserved.
1.
Introduction
Surgical procedures of the ear are always a fine balance of work to improve the existing hearing or preserve what is left in the process of clearing the disease process. Hence it is important to minimise the iatrogenic damage to the anatomy during the surgical procedure. Drilling is an important component in many mastoid procedures. The shrill produced from the drill can produce sounds up to 107 dB [1] well above the safe limit levels. The non-operated ear will be exposed to sounds just 5 dB less due to trans cranial attenuation and air conduction [2]. This high intensity noise has the theoretical possibility of producing sensorineural hearing loss in the non-operated ear, many a times the only ear with intact hearing. This problem of noise induced acoustic trauma to the non-operated ear is a less
researched topic. Pure tone audiograms in previous studies [3] showed no changes in the hearing thresholds, but the fine changes and effects on the outer hair cells [4] will be easily missed in such tests. DPOAEs can accurately monitor the outer hair cell functions and hence can be employed in their testing. In the present study we studied these possible deleterious effects by monitoring pre-operative and serial post-operative DPOAE measurements, and determined the duration of the effects and time taken for their recovery as well.
2.
Materials and methods
A comparative and prospective study was conducted on the 49 patients who underwent modified radical mastoidectomy
⁎ Corresponding author at: Department of Otolaryngology, Kasturba Medical college hospital, Attavar, Mangalore-575 001, Manipal University, Karnataka State, India. Tel.:+91 824 2445858; fax: +91 824 2428379. E-mail address: [email protected] (V.S. Shenoy). http://dx.doi.org/10.1016/j.amjoto.2015.07.013 0196-0709/© 2015 Elsevier Inc. All rights reserved.
AM ER IC AN JOURNAL OF OT OLARYNGOLOGY – H E A D A N D NE CK M E D IC IN E A ND S U RGE RY 3 6 (2 0 1 5) 8 32– 8 3 6
or cortical mastoidectomy (study group) and 49 patients who underwent myringotomy/myringoplasty surgeries (control group). Patients with features like cholesteotoma; attic-deep retractions, perforations, outer wall destructions; sigmoid sinus thrombus; tegmen erosion; chronic otitis with facial palsy were included in the unsafe type of chronic otitis media and subjected to canal wall down procedure. Normal preoperative pure tone audiometry and normal otoscopic findings in the non-operating ear in both groups were the inclusion criteria. Patient’s medical records were reviewed for age and the surgical technique used & the pre and post operative DPOAE amplitudes and the duration of surgeries were compared in each group and in between the two groups. DPOAEs were be obtained prior to surgery, immediately after surgery in the post op room, one day post operative period and one week post op. All the surgeries were done by the primary author. The drill used was Marathon Micro Motor N7R. The drill speed was between 20 and 40,000 RPM; the burr diameter was between 1 and 4.5 mm (cutting and diamond). Stimulus presentation data recording & spectrum analysis were carried out using the GSI AUDERA portable DPOAE measuring device. The F1 and F2 LEVELS were delivered at 65 dB. Frequencies F2 = 2, 3, 4 & 5 kHz & a frequency ratio of F2/F1 = 1.22. The values were compared and statistical analysis was done using student’s chi square test, with help of the institution’s statistician. Study was approved by the institutional ethical committee.
3.
Results
The mean age in the case group was 32 and the mean age in the control group was 27. In the case group 26 males and 23 females were included. In the control group 29 males and 20 females were included. Of the 49 patients in the case group 30 patients were having safe type of CSOM who underwent cortical mastoidectomy with myringoplasty, whereas 19 patients presented with unsafe type of CSOM who underwent modified radical mastoidectomy procedures. Of the 49 patients in the control group 34 patients who presented with safe type of CSOM underwent myringoplasty and 3 patients with ASOM and 12 patients with secretory otitis media underwent myringotomies, both procedures which lack drilling. Of the 49 patients in the case group the duration of mastoid drilling in the cortical mastoidectomy procedures was under 60 min, whereas the MRM procedures were longer. 5 procedures were ranging between 60 and 180 min and 12 procedures were longer than 180 min.
3.1. Changes in the DPOAE amplitudes in case and control group pre and post operatively (till 7th Post op day) There was a change in the amplitudes of DPOAEs in the immediate post-operative period over all the 4 frequencies in the case group. All the changes were statistically very significant (p < 0.001) observed over 45 cases. 4 cases did not show any change in the DPOAEs. Maximum changes in the pre op and immediate post op amplitudes of DPOAEs were recorded in 2 and 4 kHz. Recovery was noticed by post operative day 1 and complete recovery was seen by post operative day 7 (Table 1 and Chart 1).
833
Pre operative amplitudes of the DPOAEs in the control group were similar to those of the case group without any statistically significant differences between them. No changes of statistical significance were noticed in the control group over all the frequencies in the post-operative period (Table 2 and Chart 1).
3.2. Recovery of DPOAEs vs mastoid drilling duration in case group When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 2 kHz was significant (p < 0.001). The mean difference between pre op and post op day 7 was 1.21 which was not significant (p = 1.000) i.e. they had recovered by day 7. When mastoid drilling was > 60 min the mean difference between pre op and day 7 post op was 2.600 (p = 0.057), which was not significant but they were still recovering by day 7 (Table 3 and Chart 2). When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 3 kHz was significant (p = 0.048) whereas when the mastoid drilling >60 there was difference in mean difference but it was not significant (p = 0.138, p =0.565) i.e. the DPOAEs have recovered by post op day 1 (Table 3 and Chart 3). When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 4 kHz was significant (p = <0.001), when mastoid drilling >60 mean difference was significant (p = 0.009) i.e. the DPOAEs have not recovered by post op day 1 in both groups, but no significant difference was noticed between pre op and the post op day 7 amplitudes (p = 0.65 and 1.000 respectively for < 60 min and > 60 min duration) i.e. the DPOAEs had recovered by day 7 (Table 3 and Chart 4). In both the groups with < 60 and > 60 min duration of mastoid drilling the difference in pre and post op day 1 DPAOEs at 5 kHz was not significant (p = 0.215 and p = 1.000) i.e. they had recovered by day1 post op (Table 3).
4.
Discussion
The cause of sensorineural hearing loss in patients undergoing drill associated ear surgeries could be due to drill touching the ossicles, acoustic trauma or surgical manipulation of foot plate. But the opposite ear is spared by all the other factors except noise of the drill through bone conduction. Interaural attenuation of sound intensity by conduction is negligible and the noise reaching the opposite ear is only slightly less than that present in the operated ear [2].The recorded sound that presented to the contralateral ear varied in different studies from 82 dB [2] to excess of 90 dB at the level of the cochlea [5]. Kylen and Arlinger [6] found that levels of drill-generated noise increased with increasing pressure on the burr up to a force of 4 N, above which they remained constant. An experienced otological surgeon was found to use a pressure of between 8 and 10 N whilst drilling. In this study, we demonstrated a negative effect of drillgenerated noise on the contralateral normal ear and investigated the duration of this negative effect. To date, various reports about the hearing changes after mastoid surgery have been published [3,7]. In these reports, pure tone audiograms
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AM ER IC AN JOURNAL OF OT OLA RYNGOLOGY– H E A D A N D NE CK M E D ICI N E AN D S U RGE RY 3 6 (2 0 1 5) 8 32 – 8 3 6
Table 1 – Differences between pre op and post op period DPOAEs in case group.
25
Group Dependent (I) time Variable
20
Cases
DPOAE
Pre
2 kHz
Post immed Post 1 day
3 kHz
Pre
Post immed Post 1 day
4 kHz
Pre
Post immed Post 1 day
5 kHz
Pre
Post immed Post 1 day
(J) time
Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days
Mean p Difference (I − J) 18.755
.000
7.959 1.122
.000 1.000
−10.796 −17.633
.000 .000
−6.837
.000
8.367
.000
2.510 .286
.004 1.000
−5.857 −8.082
.000 .000
−2.224
.015
11.918
.000
4.592 .714
.000 1.000
−7.327 −11.204
.000 .000
−3.878
.000
2.959
.000
1.000 .286
.017 1.000
−1.959 −2.673
.000 .000
−.714
.194
[3,8], high-frequency audiometry [9], electrocochleography [10], auditory brainstem response [11] and OAE measurement [10,12,13] were used for the assessment of the audiologic results of the drill-generated noise. The mean duration of drilling in our study was found to be 82.65 min (range of 20–240 min), the mean duration was 72 (60–90 min) in the study of Lela Migirov and Michael Wolf [12] and was 47.86 min (range: 18–98 min) in the study of Erkan Karatas et al. [13]. In the study by Da Cruz et al. [9] the drilling ranged from 90 min to several hours.
15 10 5 0 Pre op
Immediate Post op day 1Post op day7 2khz(cases) post op 3khz(cases) 4khz(cases) 5khz(cases) 2khz(control) 3khz(control)
Chart 1 – DPOAE changes in case and control group from preop to post op 7th day.
In this study of 49 patients we noticed decrease in the DPOAEs in 45 patients. Lela Migirov and Michael Wolf [12] studied 13 patients and noticed alterations in 9 patients. In the study by Da Cruz et al. [9] 2 out of the 12 patients had altered amplitudes. Tos et al. [3] and Hallmo and Mair [14] failed to find significant postoperative hearing changes in the ears contralateral to mastoidectomy ears. In our study we noticed changes in all the tested frequencies (2, 3, 4, 5 kHz). In the study by Lela Migirov [12] only frequencies 2 and 4 were found to be affected; in the study of Erkan Karatas [13] frequencies 2319, 2759, 3284 and 5164 Hz were noticed to be most affected. Lela Migirov [12] explained that the fact that 2 kHz and 4 kHz were the mainly affected frequencies can be related to the sensitivity of the setonotopical regions in the cochlea to the drilling. However pure tone audiometry had missed to show these changes in studies by Tos et al. [3] and Hornung and Ostfeld [15]. High frequency audiometry successfully detected the temporary threshold elevations in the study by Hegewald et al. [7]. They reported temporary hearing threshold changes at 2 to11 kHz frequencies in mastoidectomised patients during postoperative 48 h. Hall and Lutman [4] concluded in their study that various OAE measurement techniques have the potential to distinguish small changes in cochlear function in ears exposed to noise. We noticed that the recovery has started by the post op day 1, a finding which coincided with the studies of Lela Migirov [12] and Erkan Karatas et al. [13]. Most of the subjects recovered to the preoperative levels by day 7 in our study (except 1 subject whose DPOAE was significantly lower). Erkan Karatas et al. [13] noticed full recovery by 72–96 h; Lela Migirov et al. [12] noticed that few subjects were still recovering after 4 weeks. In our study we noticed that when the drilling was more than 60 min there was a greater difference in the pre and post op DPOAE levels but there was no statistical difference in the group with < 60 min drilling duration. But it was surprising to
835
AM ER IC AN JOURNAL OF OT OLARYNGOLOGY – H E A D A N D NE CK M E D IC IN E A ND S U RGE RY 3 6 (2 0 1 5) 8 32– 8 3 6
Table 2 – DPOAEs in the control group pre and post operatively.
25
Descriptives
15
group Controls
DPOAE 2 kHz
3 kHz
4 kHz
5 kHz
Pre Post Post Post Pre Post Post Post Pre Post Post Post Pre Post Post Post
immed 1 day 7 days immed 1 day 7 days immed 1 day 7 days immed 1 day 7 days
N
Mean
Std. Deviation
49 40 49 49 49 40 49 49 49 40 49 49 49 40 49 49
20.94 20.75 18.69 20.61 17.18 16.98 16.76 17.08 12.88 12.93 11.86 12.78 10.27 10.30 10.18 10.29
1.049 .899 5.554 1.151 .808 .800 1.128 .759 .807 .764 3.208 1.066 .730 .648 .858 .540
20 <60 min drilling
10 5
60-180 min of drilling
0
>180 min of drilling
Chart 2 – Differences in recovery of DPOAEs at 2 kHz depending on duration of mastoid drilling.
note that the prior group had faster recovery. It may be due to the fact that all the cases where the drilling time was more than 60 min were “unsafe” ears and a significant part of drilling in these cases was performed by diamond burr. Hence even though the drilling process was longer on the whole it was well distributed with intermittent rests to drilling. The study of Palva and Sorri [16] noticed that hearing loss on the non-operated ears in patients who had undergone simple or radical mastoidectomy occurred more frequently and more severely in patients with drilling times of more than 3 h. We
also noticed a change in the patterns of the decrease in the DPOAEs at various frequencies studied; the changes noticed at 2 and 4 kHz and the changes noticed at 3 and 5 kHz were similar in pattern though difference in the overall pre and post-operative remained significant in both the subgroups. It has been noted that the 2 and 4 kHz groups had not recovered by post op day 1and had taken > 1 day and < 1 week duration for their recovery to pre-operative levels, whereas those in the 3 and 5 kHz frequencies had recovered by post op day1. Our findings showed that DPOAE significantly decreased in the non-operated ear immediately after mastoidectomy at 2, 3, 4 and 5 kHz, and that recovery had already begun during the first day after surgery and continued during the following week. The DPOAE fluctuations recorded throughout the study finally ended up in non-significant decreases in the DPOAE
Table 3 – Differences in recovery of DPOAEs depending on duration of mastoid drilling. 2 kHz 3 kHz 4 kHz 5 kHz group
durat
(I) time
(J) time
Mean Difference (I − J)
Sig.
Mean Difference (I − J)
Sig.
Mean Difference (I − J)
Cases
<60
Pre
Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post
18.813⁎ 10.188⁎ 1.219 −8.625⁎ −17.594⁎
.000 .000 1.000 .000 .000
8.156⁎ 2.875⁎ .750 −5.281⁎ −7.406⁎
.000 .048 1.000 .000 .000
12.219 6.406 1.156 −5.813 −11.063
−8.969⁎ 19.600⁎ 7.200⁎ 2.600 −12.400⁎ −17.000⁎
.000 .000 .000 .057 .000 .000
−2.125 8.800⁎ 3.400 −.600 −5.400⁎ −9.400⁎
.290 .000 .138 1.000 .006 .000
−4.600⁎ 18.250⁎ 2.333 .250 −15.917⁎ −18.000⁎
.001 .000 .128 1.000 .000 .000
−4.000 8.750⁎ 1.167 −.583 −7.583⁎ −9.333⁎
−2.083
.233
−1.750
Post immed Post 1 day 60–180
Pre
Post immed Post 1 day >180
Pre
Post immed Post 1 day
immed 1 day 7 days 1 day 7 days immed 7 days immed 1 day 7 days 1 day 7 days immed 7 days immed 1 day 7 days 1 day 7 days immed 7 days
Sig.
Mean Difference (I − J)
Sig.
.000 .000 .650 .000 .000
1.938⁎ .875 .094 −1.063 −1.844⁎
.000 .215 1.000 .067 .000
−5.250 13.000 3.200 .800 −9.800 −12.200
.000 .000 .009 1.000 .000 .000
−.781 4.200⁎ 2.800⁎ 1.600 −1.400 −2.600⁎
.363 .000 .002 .117 .224 .004
.056 .000 .565 1.000 .000 .000
−2.400 10.667 .333 −.500 −10.333 −11.167
.070 .000 1.000 1.000 .000 .000
−1.200 5.167⁎ .583 .250 −4.583⁎ −4.917⁎
.416 .000 1.000 1.000 .000 .000
.083
−.833
.922
−.333
1.000
836 20 18 16 14 12 10 8 6 4 2 0
AM ER IC AN JOURNAL OF OT OLA RYNGOLOGY– H E A D A N D NE CK M E D ICI N E AN D S U RGE RY 3 6 (2 0 1 5) 8 32 – 8 3 6
5.
<60 min drilling 60-180 min of drilling >180 min of drilling
Conclusion
Our results clearly indicate the temporary influence of the drill induced noise on the contralateral ear with the deteriorated amplitudes on day 0 and progressive improvement leading to preoperative normal values within a week. DPOAEs of the contralateral normal ear were found to be affected immediately after the surgery, and progressive improvement was detected with full recovery at 1 week. None of the patients had a permanent deterioration of OAE amplitudes.
REFERENCES
Chart 3 – Difference in recovery of DPOAEs at 3 kHz depending on the duration of drilling.
amplitudes compared to the preoperative ones in the study patients. The otologic drill is not only the source of the noise but also a strong vibration generator, and a strong oscillation is transmitted into the cochlea. Movement of the cochlear sections by burr stimulation can cause more damage to the cochlea than noise alone [12]. Post mastoidectomy DPOAE changes were explained by increased permeability of blood vessels of the stria vascularis and resultant injury of the organ of Corti following vibration of the temporal bone [17]. The sound produced by the drill burr may exceed a safe level, but the intermittent nature of the drilling during mastoidectomy may allow the ear sufficient time to recover [8]. Surgeons should pay more attention to vibration and lessen the magnitude of drill-induced hearing loss by selecting burs and drills that minimise the vibration of the temporal bone [10]. The best way to decrease the negative effect of drill noise was to diminish drilling time during the surgery. This could be achieved by best instruments, surgical experience and dexterity [13].
16 14 12 10 8 6 4 2 0
<60 min of drilling 60-180 min of drilling >180 min of drilling
Chart 4 – Difference in recovery of DPOAEs at 4 kHz depending on the duration of drilling.
[1] Spencer MG, Reid A. Drill-generated noise levels in mastoid surgery. J Laryngol Otol 1985;99(10):967–72. [2] Man A, Winerman I. Does drill noise duringmastoid surgery affect the contralateral ear? Am J Otolaryngol 1985;6:334–5. [3] Tos M, Trojaborg N, Thomsen J. The contralateralear after translabyrinthine removal of acoustic neuromas: is there a drill-generated hearing loss? J Laryngol Otol 1989;103:845–9. [4] Hall AJ, Lutman ME. Methods for early identification of noiseinduced hearing loss. Audiology 1999;38:277–80. [5] Hickey SA, O’Connor AF. Measurement of drill-generated noise levels during ear surgery. J Laryngol Otol 1991;105: 732–5. [6] Kylén P, Arlinger S. Drill-generated noise levels in ear surgery. Acta Otolaryngol 1976;82:402–9. [7] Hegewald M, Heitman R, Weiderhold ML, et al. Highfrequency electrostimulation hearing after mastoidectomy. Otolaryngol Head Neck Surg 1989;100:49–56. [8] Urguhart AC, McIntosh WA, Bodenstein NP. Drill-generated sensorineural hearing loss following mastoid surgery. Laryngoscope 1992;102:689–92. [9] Da Cruz MJ, Fagan P, Atlas M, et al. Drill-induced hearing loss in the nonoperated ear. Otolaryngol Head Neck Surg 1997; 117:555–8. [10] Zou J, Bretlau P, Pyykkö I, et al. Sensorineural hearing loss after vibration: an animal model for evaluating prevention and treatment of inner ear hearing loss. Acta Otolaryngol 2001;121:143–8. [11] Domenech J, Carulla M, Traserra J. Sensorineural highfrequency hearing loss after drill-generated acoustic trauma in tympanoplasty. Arch Otorhinolaryngol 1989;246:280–2. [12] 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(3):153–6. [13] Karatas E, Miman MC, Ozturan O, et al. Contralateral normal ear after mastoid surgery: evaluation by otoacoustic emissions (mastoid drilling and hearing loss). ORL J Otorhinolaryngol Relat Spec 2007;69(1):18–24. [14] 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. [15] Hornung S, Ostfeld E. Bone conduction evaluation related to mastoid surgery. Laryngoscope 1984;94:547–9. [16] Palva A, Sorri M. Can an operation on a deaf ear be dangerous for hearing? Acta Otolaryngol Suppl 1979;360:155–7. [17] Miyasaka H. Morphological changes in the stria vascularis and hair cells after mastoid vibration using a cutting bur (in Japanese). Nippon Jibiinkoka Gakkai Kaiho 1999;102:1249–57.
Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/amjoto
Original contribution
Effect of mastoid drilling on the distortion product otoacoustic emissions in the non operated ear Vijendra S. Shenoy, MS⁎, Siddharth Vanka, MS, Raghavendra A. Rao, MS, Vishnu Prasad, MS, Panduranga M. Kamath, MS, Jayashree Bhat, PhD Dept of ENT and Head & neck surgery, Kasturba Medical College, Manipal University, Mangalore, India
ARTI CLE I NFO
A BS TRACT
Article history:
Objective: To monitor the effect of mastoid drilling on the non-operated ear distortion
Received 9 May 2015
product otoacoustic emissions. Materials and methods: Distortion product otoacoustic emissions (DPOAEs) were measured at frequencies of f 2 = 2, 3, 4 and 5 kHz, and a frequency ratio f 1 /f 2 = 1.22. DPOAEs were measured in 49 cases, pre and post-operatively who underwent mastoid drilling procedures, compared
with each
other
and with 49 controls who underwent
myringoplasty and myringotomy procedures. Results: Amplitudes of DPOAEs decreased significantly in those who underwent mastoidectomies over all the measured frequencies in the immediate post-operative period but had recovered by the seventh post operative day. Conclusion: Drill induced noise can cause temporary decrease in the DPOAEs postoperatively and hence temporary hearing loss for a period of one week. © 2015 Elsevier Inc. All rights reserved.
1.
Introduction
Surgical procedures of the ear are always a fine balance of work to improve the existing hearing or preserve what is left in the process of clearing the disease process. Hence it is important to minimise the iatrogenic damage to the anatomy during the surgical procedure. Drilling is an important component in many mastoid procedures. The shrill produced from the drill can produce sounds up to 107 dB [1] well above the safe limit levels. The non-operated ear will be exposed to sounds just 5 dB less due to trans cranial attenuation and air conduction [2]. This high intensity noise has the theoretical possibility of producing sensorineural hearing loss in the non-operated ear, many a times the only ear with intact hearing. This problem of noise induced acoustic trauma to the non-operated ear is a less
researched topic. Pure tone audiograms in previous studies [3] showed no changes in the hearing thresholds, but the fine changes and effects on the outer hair cells [4] will be easily missed in such tests. DPOAEs can accurately monitor the outer hair cell functions and hence can be employed in their testing. In the present study we studied these possible deleterious effects by monitoring pre-operative and serial post-operative DPOAE measurements, and determined the duration of the effects and time taken for their recovery as well.
2.
Materials and methods
A comparative and prospective study was conducted on the 49 patients who underwent modified radical mastoidectomy
⁎ Corresponding author at: Department of Otolaryngology, Kasturba Medical college hospital, Attavar, Mangalore-575 001, Manipal University, Karnataka State, India. Tel.:+91 824 2445858; fax: +91 824 2428379. E-mail address: [email protected] (V.S. Shenoy). http://dx.doi.org/10.1016/j.amjoto.2015.07.013 0196-0709/© 2015 Elsevier Inc. All rights reserved.
AM ER IC AN JOURNAL OF OT OLARYNGOLOGY – H E A D A N D NE CK M E D IC IN E A ND S U RGE RY 3 6 (2 0 1 5) 8 32– 8 3 6
or cortical mastoidectomy (study group) and 49 patients who underwent myringotomy/myringoplasty surgeries (control group). Patients with features like cholesteotoma; attic-deep retractions, perforations, outer wall destructions; sigmoid sinus thrombus; tegmen erosion; chronic otitis with facial palsy were included in the unsafe type of chronic otitis media and subjected to canal wall down procedure. Normal preoperative pure tone audiometry and normal otoscopic findings in the non-operating ear in both groups were the inclusion criteria. Patient’s medical records were reviewed for age and the surgical technique used & the pre and post operative DPOAE amplitudes and the duration of surgeries were compared in each group and in between the two groups. DPOAEs were be obtained prior to surgery, immediately after surgery in the post op room, one day post operative period and one week post op. All the surgeries were done by the primary author. The drill used was Marathon Micro Motor N7R. The drill speed was between 20 and 40,000 RPM; the burr diameter was between 1 and 4.5 mm (cutting and diamond). Stimulus presentation data recording & spectrum analysis were carried out using the GSI AUDERA portable DPOAE measuring device. The F1 and F2 LEVELS were delivered at 65 dB. Frequencies F2 = 2, 3, 4 & 5 kHz & a frequency ratio of F2/F1 = 1.22. The values were compared and statistical analysis was done using student’s chi square test, with help of the institution’s statistician. Study was approved by the institutional ethical committee.
3.
Results
The mean age in the case group was 32 and the mean age in the control group was 27. In the case group 26 males and 23 females were included. In the control group 29 males and 20 females were included. Of the 49 patients in the case group 30 patients were having safe type of CSOM who underwent cortical mastoidectomy with myringoplasty, whereas 19 patients presented with unsafe type of CSOM who underwent modified radical mastoidectomy procedures. Of the 49 patients in the control group 34 patients who presented with safe type of CSOM underwent myringoplasty and 3 patients with ASOM and 12 patients with secretory otitis media underwent myringotomies, both procedures which lack drilling. Of the 49 patients in the case group the duration of mastoid drilling in the cortical mastoidectomy procedures was under 60 min, whereas the MRM procedures were longer. 5 procedures were ranging between 60 and 180 min and 12 procedures were longer than 180 min.
3.1. Changes in the DPOAE amplitudes in case and control group pre and post operatively (till 7th Post op day) There was a change in the amplitudes of DPOAEs in the immediate post-operative period over all the 4 frequencies in the case group. All the changes were statistically very significant (p < 0.001) observed over 45 cases. 4 cases did not show any change in the DPOAEs. Maximum changes in the pre op and immediate post op amplitudes of DPOAEs were recorded in 2 and 4 kHz. Recovery was noticed by post operative day 1 and complete recovery was seen by post operative day 7 (Table 1 and Chart 1).
833
Pre operative amplitudes of the DPOAEs in the control group were similar to those of the case group without any statistically significant differences between them. No changes of statistical significance were noticed in the control group over all the frequencies in the post-operative period (Table 2 and Chart 1).
3.2. Recovery of DPOAEs vs mastoid drilling duration in case group When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 2 kHz was significant (p < 0.001). The mean difference between pre op and post op day 7 was 1.21 which was not significant (p = 1.000) i.e. they had recovered by day 7. When mastoid drilling was > 60 min the mean difference between pre op and day 7 post op was 2.600 (p = 0.057), which was not significant but they were still recovering by day 7 (Table 3 and Chart 2). When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 3 kHz was significant (p = 0.048) whereas when the mastoid drilling >60 there was difference in mean difference but it was not significant (p = 0.138, p =0.565) i.e. the DPOAEs have recovered by post op day 1 (Table 3 and Chart 3). When the duration of mastoid drilling was less than 60 min the mean difference between pre op and post op day 1 DPOAE amplitude at 4 kHz was significant (p = <0.001), when mastoid drilling >60 mean difference was significant (p = 0.009) i.e. the DPOAEs have not recovered by post op day 1 in both groups, but no significant difference was noticed between pre op and the post op day 7 amplitudes (p = 0.65 and 1.000 respectively for < 60 min and > 60 min duration) i.e. the DPOAEs had recovered by day 7 (Table 3 and Chart 4). In both the groups with < 60 and > 60 min duration of mastoid drilling the difference in pre and post op day 1 DPAOEs at 5 kHz was not significant (p = 0.215 and p = 1.000) i.e. they had recovered by day1 post op (Table 3).
4.
Discussion
The cause of sensorineural hearing loss in patients undergoing drill associated ear surgeries could be due to drill touching the ossicles, acoustic trauma or surgical manipulation of foot plate. But the opposite ear is spared by all the other factors except noise of the drill through bone conduction. Interaural attenuation of sound intensity by conduction is negligible and the noise reaching the opposite ear is only slightly less than that present in the operated ear [2].The recorded sound that presented to the contralateral ear varied in different studies from 82 dB [2] to excess of 90 dB at the level of the cochlea [5]. Kylen and Arlinger [6] found that levels of drill-generated noise increased with increasing pressure on the burr up to a force of 4 N, above which they remained constant. An experienced otological surgeon was found to use a pressure of between 8 and 10 N whilst drilling. In this study, we demonstrated a negative effect of drillgenerated noise on the contralateral normal ear and investigated the duration of this negative effect. To date, various reports about the hearing changes after mastoid surgery have been published [3,7]. In these reports, pure tone audiograms
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AM ER IC AN JOURNAL OF OT OLA RYNGOLOGY– H E A D A N D NE CK M E D ICI N E AN D S U RGE RY 3 6 (2 0 1 5) 8 32 – 8 3 6
Table 1 – Differences between pre op and post op period DPOAEs in case group.
25
Group Dependent (I) time Variable
20
Cases
DPOAE
Pre
2 kHz
Post immed Post 1 day
3 kHz
Pre
Post immed Post 1 day
4 kHz
Pre
Post immed Post 1 day
5 kHz
Pre
Post immed Post 1 day
(J) time
Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days Post immed Post 1 day Post 7 days Post 1 day Post 7 days Post immed Post 7 days
Mean p Difference (I − J) 18.755
.000
7.959 1.122
.000 1.000
−10.796 −17.633
.000 .000
−6.837
.000
8.367
.000
2.510 .286
.004 1.000
−5.857 −8.082
.000 .000
−2.224
.015
11.918
.000
4.592 .714
.000 1.000
−7.327 −11.204
.000 .000
−3.878
.000
2.959
.000
1.000 .286
.017 1.000
−1.959 −2.673
.000 .000
−.714
.194
[3,8], high-frequency audiometry [9], electrocochleography [10], auditory brainstem response [11] and OAE measurement [10,12,13] were used for the assessment of the audiologic results of the drill-generated noise. The mean duration of drilling in our study was found to be 82.65 min (range of 20–240 min), the mean duration was 72 (60–90 min) in the study of Lela Migirov and Michael Wolf [12] and was 47.86 min (range: 18–98 min) in the study of Erkan Karatas et al. [13]. In the study by Da Cruz et al. [9] the drilling ranged from 90 min to several hours.
15 10 5 0 Pre op
Immediate Post op day 1Post op day7 2khz(cases) post op 3khz(cases) 4khz(cases) 5khz(cases) 2khz(control) 3khz(control)
Chart 1 – DPOAE changes in case and control group from preop to post op 7th day.
In this study of 49 patients we noticed decrease in the DPOAEs in 45 patients. Lela Migirov and Michael Wolf [12] studied 13 patients and noticed alterations in 9 patients. In the study by Da Cruz et al. [9] 2 out of the 12 patients had altered amplitudes. Tos et al. [3] and Hallmo and Mair [14] failed to find significant postoperative hearing changes in the ears contralateral to mastoidectomy ears. In our study we noticed changes in all the tested frequencies (2, 3, 4, 5 kHz). In the study by Lela Migirov [12] only frequencies 2 and 4 were found to be affected; in the study of Erkan Karatas [13] frequencies 2319, 2759, 3284 and 5164 Hz were noticed to be most affected. Lela Migirov [12] explained that the fact that 2 kHz and 4 kHz were the mainly affected frequencies can be related to the sensitivity of the setonotopical regions in the cochlea to the drilling. However pure tone audiometry had missed to show these changes in studies by Tos et al. [3] and Hornung and Ostfeld [15]. High frequency audiometry successfully detected the temporary threshold elevations in the study by Hegewald et al. [7]. They reported temporary hearing threshold changes at 2 to11 kHz frequencies in mastoidectomised patients during postoperative 48 h. Hall and Lutman [4] concluded in their study that various OAE measurement techniques have the potential to distinguish small changes in cochlear function in ears exposed to noise. We noticed that the recovery has started by the post op day 1, a finding which coincided with the studies of Lela Migirov [12] and Erkan Karatas et al. [13]. Most of the subjects recovered to the preoperative levels by day 7 in our study (except 1 subject whose DPOAE was significantly lower). Erkan Karatas et al. [13] noticed full recovery by 72–96 h; Lela Migirov et al. [12] noticed that few subjects were still recovering after 4 weeks. In our study we noticed that when the drilling was more than 60 min there was a greater difference in the pre and post op DPOAE levels but there was no statistical difference in the group with < 60 min drilling duration. But it was surprising to
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Table 2 – DPOAEs in the control group pre and post operatively.
25
Descriptives
15
group Controls
DPOAE 2 kHz
3 kHz
4 kHz
5 kHz
Pre Post Post Post Pre Post Post Post Pre Post Post Post Pre Post Post Post
immed 1 day 7 days immed 1 day 7 days immed 1 day 7 days immed 1 day 7 days
N
Mean
Std. Deviation
49 40 49 49 49 40 49 49 49 40 49 49 49 40 49 49
20.94 20.75 18.69 20.61 17.18 16.98 16.76 17.08 12.88 12.93 11.86 12.78 10.27 10.30 10.18 10.29
1.049 .899 5.554 1.151 .808 .800 1.128 .759 .807 .764 3.208 1.066 .730 .648 .858 .540
20 <60 min drilling
10 5
60-180 min of drilling
0
>180 min of drilling
Chart 2 – Differences in recovery of DPOAEs at 2 kHz depending on duration of mastoid drilling.
note that the prior group had faster recovery. It may be due to the fact that all the cases where the drilling time was more than 60 min were “unsafe” ears and a significant part of drilling in these cases was performed by diamond burr. Hence even though the drilling process was longer on the whole it was well distributed with intermittent rests to drilling. The study of Palva and Sorri [16] noticed that hearing loss on the non-operated ears in patients who had undergone simple or radical mastoidectomy occurred more frequently and more severely in patients with drilling times of more than 3 h. We
also noticed a change in the patterns of the decrease in the DPOAEs at various frequencies studied; the changes noticed at 2 and 4 kHz and the changes noticed at 3 and 5 kHz were similar in pattern though difference in the overall pre and post-operative remained significant in both the subgroups. It has been noted that the 2 and 4 kHz groups had not recovered by post op day 1and had taken > 1 day and < 1 week duration for their recovery to pre-operative levels, whereas those in the 3 and 5 kHz frequencies had recovered by post op day1. Our findings showed that DPOAE significantly decreased in the non-operated ear immediately after mastoidectomy at 2, 3, 4 and 5 kHz, and that recovery had already begun during the first day after surgery and continued during the following week. The DPOAE fluctuations recorded throughout the study finally ended up in non-significant decreases in the DPOAE
Table 3 – Differences in recovery of DPOAEs depending on duration of mastoid drilling. 2 kHz 3 kHz 4 kHz 5 kHz group
durat
(I) time
(J) time
Mean Difference (I − J)
Sig.
Mean Difference (I − J)
Sig.
Mean Difference (I − J)
Cases
<60
Pre
Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post Post
18.813⁎ 10.188⁎ 1.219 −8.625⁎ −17.594⁎
.000 .000 1.000 .000 .000
8.156⁎ 2.875⁎ .750 −5.281⁎ −7.406⁎
.000 .048 1.000 .000 .000
12.219 6.406 1.156 −5.813 −11.063
−8.969⁎ 19.600⁎ 7.200⁎ 2.600 −12.400⁎ −17.000⁎
.000 .000 .000 .057 .000 .000
−2.125 8.800⁎ 3.400 −.600 −5.400⁎ −9.400⁎
.290 .000 .138 1.000 .006 .000
−4.600⁎ 18.250⁎ 2.333 .250 −15.917⁎ −18.000⁎
.001 .000 .128 1.000 .000 .000
−4.000 8.750⁎ 1.167 −.583 −7.583⁎ −9.333⁎
−2.083
.233
−1.750
Post immed Post 1 day 60–180
Pre
Post immed Post 1 day >180
Pre
Post immed Post 1 day
immed 1 day 7 days 1 day 7 days immed 7 days immed 1 day 7 days 1 day 7 days immed 7 days immed 1 day 7 days 1 day 7 days immed 7 days
Sig.
Mean Difference (I − J)
Sig.
.000 .000 .650 .000 .000
1.938⁎ .875 .094 −1.063 −1.844⁎
.000 .215 1.000 .067 .000
−5.250 13.000 3.200 .800 −9.800 −12.200
.000 .000 .009 1.000 .000 .000
−.781 4.200⁎ 2.800⁎ 1.600 −1.400 −2.600⁎
.363 .000 .002 .117 .224 .004
.056 .000 .565 1.000 .000 .000
−2.400 10.667 .333 −.500 −10.333 −11.167
.070 .000 1.000 1.000 .000 .000
−1.200 5.167⁎ .583 .250 −4.583⁎ −4.917⁎
.416 .000 1.000 1.000 .000 .000
.083
−.833
.922
−.333
1.000
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5.
<60 min drilling 60-180 min of drilling >180 min of drilling
Conclusion
Our results clearly indicate the temporary influence of the drill induced noise on the contralateral ear with the deteriorated amplitudes on day 0 and progressive improvement leading to preoperative normal values within a week. DPOAEs of the contralateral normal ear were found to be affected immediately after the surgery, and progressive improvement was detected with full recovery at 1 week. None of the patients had a permanent deterioration of OAE amplitudes.
REFERENCES
Chart 3 – Difference in recovery of DPOAEs at 3 kHz depending on the duration of drilling.
amplitudes compared to the preoperative ones in the study patients. The otologic drill is not only the source of the noise but also a strong vibration generator, and a strong oscillation is transmitted into the cochlea. Movement of the cochlear sections by burr stimulation can cause more damage to the cochlea than noise alone [12]. Post mastoidectomy DPOAE changes were explained by increased permeability of blood vessels of the stria vascularis and resultant injury of the organ of Corti following vibration of the temporal bone [17]. The sound produced by the drill burr may exceed a safe level, but the intermittent nature of the drilling during mastoidectomy may allow the ear sufficient time to recover [8]. Surgeons should pay more attention to vibration and lessen the magnitude of drill-induced hearing loss by selecting burs and drills that minimise the vibration of the temporal bone [10]. The best way to decrease the negative effect of drill noise was to diminish drilling time during the surgery. This could be achieved by best instruments, surgical experience and dexterity [13].
16 14 12 10 8 6 4 2 0
<60 min of drilling 60-180 min of drilling >180 min of drilling
Chart 4 – Difference in recovery of DPOAEs at 4 kHz depending on the duration of drilling.
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