Acta Oto-Laryngologica. 2014; 134: 943–946
ORIGINAL ARTICLE
Drill-induced noise level during cochleostomy
HONG YU1,2*, BUSHENG TONG3*, QING ZHANG4, WEI ZHU1 & MAOLI DUAN2,3,4,5 1
Department of Otolaryngology, Head and Neck Surgery, First Hospital of Jilin University, Changchun, China, Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden, 3Department of Otolaryngology, Head and Neck Surgery, First Affiliated Hospital of Anhui Medical University, Hefei, China, 4Department of Otolaryngology, Head and Neck Surgery, Second Affiliated Hospital of Xi’an Jiaotong University, College of Medicine, Xi’an, China and 5Department of Neurotology, Department of Otolaryngology Head and Neck Surgery, Karolinska University Hospital, Stockholm, Sweden 2
Abstract Conclusions: Noise induced by drilling during cochleostomy is of high level and can cause acoustic trauma to the inner ear, particularly after the membranous labyrinth has been exposed. Our method utilizes non-invasive noise measurement and the equipment that is connected to the operative area can be sterilized, thus it can be applied to intraoperative recordings. Objectives: To investigate the noise level generated by otological electrical drills during the cochleostomy procedure and to further explore the feasibility of noise monitoring in vivo. Methods: Acoustic measurements during drilling on the promontory of cochleae were carried out on 16 human cadavers (19 ears) using an ER7C probe microphone system. Results: The peak noise level generated during cochleostomy differed obviously from specimen to specimen and ranged from 85.9 to 131.5 dB SPL. We found three cases in which the peak noise level exceeded 130 dB SPL when the running burr touched the endosteal membrane.
Keywords: Acoustic trauma, noise-induced hearing loss, ER7C, cochlear implantation, inner ear
Introduction Sensorineural hearing loss (SNHL) is still a global prominent disability, which has a profound impact on communication and quality of life. It is certainly accepted that exposure to high levels of noise can be harmful to the inner ear, resulting in a temporary and/or a permanent threshold shift. The developments and utilities of medical drills also bring this problem. To date, SNHL associated with the drilling procedure and accompanying noise has been widely investigated. It was reported that the incidence of a permanent SNHL following tympanomastoid surgery is between 1.2% and 4.5% [1]. Some experiments indicated that drilling or vibration of the temporal bone caused different degrees of hearing loss
in the high frequencies [2,3], while Urquhart et al. found that hearing loss could occur in a wide frequency range [4]. Evaluations concerning the noise levels and spectral characteristics produced by drilling in different surgical procedures also have been reported. Hilmi et al. showed that maximum noise transmission was 108 dBA at 4 kHz and dropped to 84 dBA at 8 kHz, and 40 dBA at 16 kHz [5]. Kylén and Arlinger reported that the noises conducted to the ipsilateral and contralateral ear were about 100 dB and 90–95 dB during drilling procedures in ear surgery [6]. If the ossicular chain is accidentally touched by a running burr, the equivalent noise levels generated ranged from 93 to 125 dB sound pressure level (SPL) [7]. Strömberg et al. monitored noise levels induced by drilling that ranged from 84 to
Correspondence: Wei Zhu, Department of Otolaryngology, Head and Neck Surgery, First Hospital of Jilin University, 130000, Changchun, China. Tel: +86 81875506. Fax: +86 88786160. E-mail: [email protected] and Maoli Duan, Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Karolinska Institute, SE-171 76 Stockholm, Sweden. Tel: +46 8 5177 0000. Fax: +46 8 348546. E-mail: [email protected] *These authors contributed equally to this work.
(Received 5 April 2014; accepted 12 May 2014) ISSN 0001-6489 print/ISSN 1651-2251 online Ó 2014 Informa Healthcare DOI: 10.3109/00016489.2014.927591
944
H. Yu et al.
125 dB SPL in cortical bone and from 85 to 117 dB SPL in the mastoid cavity [8]. Pau et al. found that the highest SPLs during cochleostomy exceeded 130 dB when the running burr touched the intact endosteal membrane [9]. The noise-induced hearing loss could lead to significant physiological changes in the organ of Corti and increase of permeability across the capillary vessels in the stria vascularis [10]. Fishman et al. found that no compound action potentials (CAPs) could be evoked acoustically at the drilling site (high frequencies) and towards the apex (low frequencies) in animal models, indicating that cochlear function was severely impaired by drilling cochleostomy [11]. Generally, rehabilitation and treatments for SNHL fall into two categories: hearing aids and cochlear implantation. Each of them has its disadvantages and tends to be appropriate for different patients. Until recently patients were faced with the choice between using a hearing aid plus cochlear implantation while they wanted to keep remaining hearing in the lower frequency. Thus, electric acoustic stimulation (EAS) has been developed, which has focused on combining amplification of preserved hearing and electrostimulation in the same ear to provide significant advantages for speech discrimination in a noisy background [12,13]. Therefore, it will benefit patients to minimize cochlear trauma and maximize residual hearing, which had been reported to be completely lost in at least 10–20% of recipients during cochlear implant surgery [14]. Together with modifications in surgical techniques and new types of electrode arrays, much attention has been paid to monitor drill-induced noise and minimize accompanying noise trauma to the inner ear. The aim of the present study was to measure noise levels generated by the drilling procedure during cochleostomy using human cadavers, and to further explore the feasibility of intraoperative noise monitoring in vivo. Material and methods Experiments were carried out on 16 cadavers (19 ears) that had been bequeathed for medical education and for research purposes with approval from the Medical Ethical Committee of Anhui Medical University and Xi’an Jiaotong University in China. None of the specimens showed any abnormality of the middle and inner ear. To access the promontory and the basal cochlear turn, wide mastoidectomy and posterior tympanotomy were performed in each ear, exposing the ossicular chain in the antrum and the labyrinth bone, which was left intact. All bone was removed between the annulus fibrosus of the tympanic and the facial nerve, which made it possible to
access the medial tympanic wall with the oval and round window as well as the promontory. During drilling, great care was taken to leave the sound conducting system completely intact and to keep the drill–bone interface moist by continuous spraying with saline solution. Noise intensity was measured during drilling on the promontory anterior-inferior to the round window with laminar ablation of bone using a 1 mm diamond burr. Recording of the noise level was performed using an ER7C probe microphone system (Etymotic Research Inc., Elk Grove Village, IL, USA). In brief, the open end of the silicone tube was held in the round window niche parallel to drilling, about 5 mm from the bone–drill interface. Each recording lasted 10 s. The max and root mean square (RMS) sound levels were analyzed as described in our previous paper [8]. Results Noise levels generated during each cochleostomy procedure are shown in Table I. Peak noise levels differed obviously from specimen to specimen, and ranged from 85.9 to 131.5 dB SPL, with an average of Table I. Individual noise levels generated by 1 mm diamond burr during drilling cochleostomy on different ears. Specimen
SPL peak noise level (dB SPL)
Linear RMS (dB SPL)
1
85.9
80.2
2
97.3
89.5
3
96.1
86.9
4
100.1
96.5
5
105.1
98.0
6
115.3
109.7
7
102.1
94.3
8
98.8
82.7
9
118.8
107.0
10
127.3
117.0
11
116.9
110.8
12
121.1
106.0
13
130.4
124.6
14
109.2
103.5
15
130.4
124.6
16
131.5
120.6
17
115.1
109.0
18
102.4
95.2
19
104.8
94.6
Average (mean ± SD)
110.9 ± 13.3
102.7 ± 13.4
RMS, root mean square; SD, standard deviation; SPL, sound pressure level.
Drill-induced noise level during cochleostomy 110.9 dB SPL. For specimens 13, 15, and 16 (3/19, 15.8%), the peak noise levels exceeded 130 dB SPL when the diamond burr touched the endosteal membrane. In addition, 2/19 (10.5%) of the recorded peak noises were between 120 and 130 dB SPL, 4/19 (21.1%) of the recorded peak noises were between 110 and 120 dB SPL, 6/19 (31.6%) of the recorded peak noises were between 100 and 110 dB SPL, 3/19 (15.8%) of the recorded peak noises were between 90 and 100 dB SPL, and only 1/19 (5.1%) of the recorded peak noises was below 90 dB SPL. More than half of the noise levels recorded (10/19, 52.6%) were between 100 and 120 dB SPL. Calculated linear RMS ranged from 80.2 to 124.9 dB SPL, with an average of 102.7 dB SPL. More than half of RMSs recorded (10/19, 52.6%) were between 90 and 110 dB SPL; none of the RMSs was above 130 dB SPL. Discussion Our recordings near the round window provided accurate evaluations of cochlear noise loading during drilling a cochleostomy. The sound pressures differed obviously from each specimen, and ranged from less than 90 dB SPL to more than 130 dB SPL. These different results could be due to the different conditions of the individual specimens, such as age, gender, bone density, and soft tissue structure. Actually, the application of otological drills will indeed generate loud noises. Our data showed that most of the detected peak noise levels (52.6%) were between 100 and 120 dB SPL, with an average of 110.9 dB SPL, which can definitely cause significant acoustic trauma to the inner ear, similar to conventional middle ear surgery. Furthermore, our results showed that the peak noise levels of three cases exceeded 130 dB SPL when the membranous labyrinth was touched by the running burr, which corresponded well with the records in a temporal bone model described by Pau et al. [9]. We think that this huge noise exposure is an extremely dangerous factor as regards damage of inner ear function. Our measurement is methodologically different from the estimations of equivalent airborne noise levels by means of laser Doppler vibrometry and accelerometer, while the records differed slightly. Pau et al. measured the level of intracochlear noise exposure during different drilling procedures on human temporal bone [9]. They were 103.8 dB with the 1 mm diamond burr when drilling on the promontory and 107.2 dB with the 2 mm diamond burr when the ‘blue line’ could be seen. Once the endosteal layer was exposed and touched by the cutter, maximum SPL could exceed 130 dB, which exceeds the noise level generated when the running
945
burr hits the ossicular chain [15]. Thus, their findings are similar to our results. In addition, our method does not increase any surgery procedures; we can measure noise level induced by drilling during the surgery routine. Furthermore, the method is non-invasive for measurement of noise level and can be applied in middle ear surgery and cochlear implantation in patients in the future. Meanwhile, the measurement can be performed at the round window and the silicone tube covering the microphone can easily be sterilized together with the rest of the equipment. Noise trauma has long been a concern when performing cochleostomy; more interest has been focused on minimizing the damage to the inner ear and remaining residual hearing. To successfully implement this strategy, a number of approaches have been investigated. They were as follows. (1) ‘Soft surgery,’ involving drilling a minimal cochleostomy, avoiding suction of the perilymph, and sealing the cochleostomy hole [16], or using low-speed drills or combined techniques to avoid direct mechanical and acoustic trauma [11,17]. (2) Using round window insertion techniques instead of a cochleostomy, which provided a reduced amount of drilling and minimized loss of perilymph and entry of bone dust into the scala tympani [18]. (3) Application of pharmacological agents, such as steroids and antioxidants to protect the inner ear against damage [19]. In the cadaver model, we confirmed that there are individual high noise exposures during cochleostomy, particularly after the membranous labyrinth has been exposed and touched, which could cause high sound pressure peaks of more than 130 dB SPL. Such a level is actually an extremely high risk to inner ear function. However, there is little information available as regards drill-induced noise level in actual cochleostomy; therefore, experiments in vivo are needed in the future. Acknowledgments This research project was supported by the Karolinska Institute, Tysta Skolan, Stockholm County Council (ALF-funding), Sweden and Anhui Medical University, Xi’an Jiaotong University, Jilin University, China. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References [1] Tos M, Lau T, Plate S. Sensorineural hearing loss following chronic ear surgery. Ann Otol Rhinol Laryngol 1984;93:403–9.
946
H. Yu et al.
[2] Doménech J, Carulla M, Traserra J. Sensorineural highfrequency hearing loss after drill-generated acoustic trauma in tympanoplasty. Arch Otorhinolaryngol 1989;246:280–2. [3] Farzanegan G, Ghasemi M, Panahi F, Raza M, Alghasi M. Does drill-induced noise have an impact on sensorineural hearing during craniotomy procedure? Br J Neurosurg 2010; 24:40–5. [4] Urquhart AC, McIntosh WA, Bodenstein NP. Drillgenerated sensorineural hearing loss following mastoid surgery. Laryngoscope 1992;102:689–92. [5] Hilmi OJ, Mckee RH, Abel EW, Spielmann PM, Hussain SS. Do high-speed drills generate high-frequency noise in mastoid surgery? Otol Neurotol 2012;33:2–5. [6] Kylén P, Arlinger S. Drill-generated noise levels in ear surgery. Acta Otolaryngol 1976;82:402–9. [7] Ikeya J, Kawano A, Nishiyama N, Kawaguchi S, Hagiwara A, Suzuki M. Long-term complications after cochlear implantation. Auris Nasus Larynx 2013;40:525–9. [8] Strömberg AK, Yin X, Olofsson A, Duan M. Evaluation of the usefulness of a silicone tube connected to a microphone in monitoring noise levels induced by drilling during mastoidectomy and cochleostomy. Acta Otolaryngol 2010; 130:1163–8. [9] Pau HW, Just T, Bornitz M, Lasurashvilli N, Zahnert T. Noise exposure of the inner ear during drilling a cochleostomy for cochlear implantation. Laryngoscope 2007;117:535–40. [10] Seki M, Miyasaka H, Edamatsu H, Watanabe K. Changes in permeability of strial vessels following vibration given to auditory ossicle by drill. Ann Otol Rhinol Laryngol 2001; 110:122–6. [11] Fishman AJ, Moreno LE, Rivera A, Richter CP. CO2 laser fiber soft cochleostomy: development of a technique using
[12]
[13]
[14]
[15]
[16] [17]
[18]
[19]
human temporal bones and a guinea pig model. Lasers Surg Med 2010;42:245–56. Gantz BJ, Turner C, Gfeller KE, Lowder MW. Preservation of hearing in cochlear implant surgery: advantages of combined electrical and acoustical speech processing. Laryngoscope 2005;115:796–802. Turner CW, Gantz BJ, Karsten S, Fowler J, Reiss LA. Impact of hair cell preservation in cochlear implantation: combined electric and acoustic hearing. Otol Neurotol 2010;31: 1227–32. James C, Albegger K, Battmer R, Burdo S, Deggouj N, Deguine O, et al. Preservation of residual hearing with cochlear implantation: how and why. Acta Otolaryngol 2005;125:481–91. Jiang D, Bibas A, Santuli C, Donnelly N, Jeronimidis G, O’Connor AF. Equivalent noise level generated by drilling onto the ossicular chain as measured by laser Doppler vibrometry: a temporal bone study. Laryngoscope 2007;117: 1040–5. Lehnhardt E. Intracochlear placement of cochlear implant electrodes in soft surgery technique. HNO 1993;41:356–9. Michaelides EM, Kartush JM. Implications of sound levels generated by otologic devices. Otolaryngol Head Neck Surg 2001;125:361–3. Havenith S, Lammers MJ, Tange RA, Trabalzini F, della Volpe A, van der Heijden GJ, et al. Hearing preservation surgery: cochleostomy or round window approach? A systematic review. Otol Neurotol 2013;34:667–74. Duan M, Qiu J, Laurell G, Olofsson A, Counter SA, Borg E. Dose and time-dependent protection of the antioxidant N-L-acetylcysteine against impulse noise trauma. Hear Res 2004;192:1–9.
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ORIGINAL ARTICLE
Drill-induced noise level during cochleostomy
HONG YU1,2*, BUSHENG TONG3*, QING ZHANG4, WEI ZHU1 & MAOLI DUAN2,3,4,5 1
Department of Otolaryngology, Head and Neck Surgery, First Hospital of Jilin University, Changchun, China, Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden, 3Department of Otolaryngology, Head and Neck Surgery, First Affiliated Hospital of Anhui Medical University, Hefei, China, 4Department of Otolaryngology, Head and Neck Surgery, Second Affiliated Hospital of Xi’an Jiaotong University, College of Medicine, Xi’an, China and 5Department of Neurotology, Department of Otolaryngology Head and Neck Surgery, Karolinska University Hospital, Stockholm, Sweden 2
Abstract Conclusions: Noise induced by drilling during cochleostomy is of high level and can cause acoustic trauma to the inner ear, particularly after the membranous labyrinth has been exposed. Our method utilizes non-invasive noise measurement and the equipment that is connected to the operative area can be sterilized, thus it can be applied to intraoperative recordings. Objectives: To investigate the noise level generated by otological electrical drills during the cochleostomy procedure and to further explore the feasibility of noise monitoring in vivo. Methods: Acoustic measurements during drilling on the promontory of cochleae were carried out on 16 human cadavers (19 ears) using an ER7C probe microphone system. Results: The peak noise level generated during cochleostomy differed obviously from specimen to specimen and ranged from 85.9 to 131.5 dB SPL. We found three cases in which the peak noise level exceeded 130 dB SPL when the running burr touched the endosteal membrane.
Keywords: Acoustic trauma, noise-induced hearing loss, ER7C, cochlear implantation, inner ear
Introduction Sensorineural hearing loss (SNHL) is still a global prominent disability, which has a profound impact on communication and quality of life. It is certainly accepted that exposure to high levels of noise can be harmful to the inner ear, resulting in a temporary and/or a permanent threshold shift. The developments and utilities of medical drills also bring this problem. To date, SNHL associated with the drilling procedure and accompanying noise has been widely investigated. It was reported that the incidence of a permanent SNHL following tympanomastoid surgery is between 1.2% and 4.5% [1]. Some experiments indicated that drilling or vibration of the temporal bone caused different degrees of hearing loss
in the high frequencies [2,3], while Urquhart et al. found that hearing loss could occur in a wide frequency range [4]. Evaluations concerning the noise levels and spectral characteristics produced by drilling in different surgical procedures also have been reported. Hilmi et al. showed that maximum noise transmission was 108 dBA at 4 kHz and dropped to 84 dBA at 8 kHz, and 40 dBA at 16 kHz [5]. Kylén and Arlinger reported that the noises conducted to the ipsilateral and contralateral ear were about 100 dB and 90–95 dB during drilling procedures in ear surgery [6]. If the ossicular chain is accidentally touched by a running burr, the equivalent noise levels generated ranged from 93 to 125 dB sound pressure level (SPL) [7]. Strömberg et al. monitored noise levels induced by drilling that ranged from 84 to
Correspondence: Wei Zhu, Department of Otolaryngology, Head and Neck Surgery, First Hospital of Jilin University, 130000, Changchun, China. Tel: +86 81875506. Fax: +86 88786160. E-mail: [email protected] and Maoli Duan, Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Karolinska Institute, SE-171 76 Stockholm, Sweden. Tel: +46 8 5177 0000. Fax: +46 8 348546. E-mail: [email protected] *These authors contributed equally to this work.
(Received 5 April 2014; accepted 12 May 2014) ISSN 0001-6489 print/ISSN 1651-2251 online Ó 2014 Informa Healthcare DOI: 10.3109/00016489.2014.927591
944
H. Yu et al.
125 dB SPL in cortical bone and from 85 to 117 dB SPL in the mastoid cavity [8]. Pau et al. found that the highest SPLs during cochleostomy exceeded 130 dB when the running burr touched the intact endosteal membrane [9]. The noise-induced hearing loss could lead to significant physiological changes in the organ of Corti and increase of permeability across the capillary vessels in the stria vascularis [10]. Fishman et al. found that no compound action potentials (CAPs) could be evoked acoustically at the drilling site (high frequencies) and towards the apex (low frequencies) in animal models, indicating that cochlear function was severely impaired by drilling cochleostomy [11]. Generally, rehabilitation and treatments for SNHL fall into two categories: hearing aids and cochlear implantation. Each of them has its disadvantages and tends to be appropriate for different patients. Until recently patients were faced with the choice between using a hearing aid plus cochlear implantation while they wanted to keep remaining hearing in the lower frequency. Thus, electric acoustic stimulation (EAS) has been developed, which has focused on combining amplification of preserved hearing and electrostimulation in the same ear to provide significant advantages for speech discrimination in a noisy background [12,13]. Therefore, it will benefit patients to minimize cochlear trauma and maximize residual hearing, which had been reported to be completely lost in at least 10–20% of recipients during cochlear implant surgery [14]. Together with modifications in surgical techniques and new types of electrode arrays, much attention has been paid to monitor drill-induced noise and minimize accompanying noise trauma to the inner ear. The aim of the present study was to measure noise levels generated by the drilling procedure during cochleostomy using human cadavers, and to further explore the feasibility of intraoperative noise monitoring in vivo. Material and methods Experiments were carried out on 16 cadavers (19 ears) that had been bequeathed for medical education and for research purposes with approval from the Medical Ethical Committee of Anhui Medical University and Xi’an Jiaotong University in China. None of the specimens showed any abnormality of the middle and inner ear. To access the promontory and the basal cochlear turn, wide mastoidectomy and posterior tympanotomy were performed in each ear, exposing the ossicular chain in the antrum and the labyrinth bone, which was left intact. All bone was removed between the annulus fibrosus of the tympanic and the facial nerve, which made it possible to
access the medial tympanic wall with the oval and round window as well as the promontory. During drilling, great care was taken to leave the sound conducting system completely intact and to keep the drill–bone interface moist by continuous spraying with saline solution. Noise intensity was measured during drilling on the promontory anterior-inferior to the round window with laminar ablation of bone using a 1 mm diamond burr. Recording of the noise level was performed using an ER7C probe microphone system (Etymotic Research Inc., Elk Grove Village, IL, USA). In brief, the open end of the silicone tube was held in the round window niche parallel to drilling, about 5 mm from the bone–drill interface. Each recording lasted 10 s. The max and root mean square (RMS) sound levels were analyzed as described in our previous paper [8]. Results Noise levels generated during each cochleostomy procedure are shown in Table I. Peak noise levels differed obviously from specimen to specimen, and ranged from 85.9 to 131.5 dB SPL, with an average of Table I. Individual noise levels generated by 1 mm diamond burr during drilling cochleostomy on different ears. Specimen
SPL peak noise level (dB SPL)
Linear RMS (dB SPL)
1
85.9
80.2
2
97.3
89.5
3
96.1
86.9
4
100.1
96.5
5
105.1
98.0
6
115.3
109.7
7
102.1
94.3
8
98.8
82.7
9
118.8
107.0
10
127.3
117.0
11
116.9
110.8
12
121.1
106.0
13
130.4
124.6
14
109.2
103.5
15
130.4
124.6
16
131.5
120.6
17
115.1
109.0
18
102.4
95.2
19
104.8
94.6
Average (mean ± SD)
110.9 ± 13.3
102.7 ± 13.4
RMS, root mean square; SD, standard deviation; SPL, sound pressure level.
Drill-induced noise level during cochleostomy 110.9 dB SPL. For specimens 13, 15, and 16 (3/19, 15.8%), the peak noise levels exceeded 130 dB SPL when the diamond burr touched the endosteal membrane. In addition, 2/19 (10.5%) of the recorded peak noises were between 120 and 130 dB SPL, 4/19 (21.1%) of the recorded peak noises were between 110 and 120 dB SPL, 6/19 (31.6%) of the recorded peak noises were between 100 and 110 dB SPL, 3/19 (15.8%) of the recorded peak noises were between 90 and 100 dB SPL, and only 1/19 (5.1%) of the recorded peak noises was below 90 dB SPL. More than half of the noise levels recorded (10/19, 52.6%) were between 100 and 120 dB SPL. Calculated linear RMS ranged from 80.2 to 124.9 dB SPL, with an average of 102.7 dB SPL. More than half of RMSs recorded (10/19, 52.6%) were between 90 and 110 dB SPL; none of the RMSs was above 130 dB SPL. Discussion Our recordings near the round window provided accurate evaluations of cochlear noise loading during drilling a cochleostomy. The sound pressures differed obviously from each specimen, and ranged from less than 90 dB SPL to more than 130 dB SPL. These different results could be due to the different conditions of the individual specimens, such as age, gender, bone density, and soft tissue structure. Actually, the application of otological drills will indeed generate loud noises. Our data showed that most of the detected peak noise levels (52.6%) were between 100 and 120 dB SPL, with an average of 110.9 dB SPL, which can definitely cause significant acoustic trauma to the inner ear, similar to conventional middle ear surgery. Furthermore, our results showed that the peak noise levels of three cases exceeded 130 dB SPL when the membranous labyrinth was touched by the running burr, which corresponded well with the records in a temporal bone model described by Pau et al. [9]. We think that this huge noise exposure is an extremely dangerous factor as regards damage of inner ear function. Our measurement is methodologically different from the estimations of equivalent airborne noise levels by means of laser Doppler vibrometry and accelerometer, while the records differed slightly. Pau et al. measured the level of intracochlear noise exposure during different drilling procedures on human temporal bone [9]. They were 103.8 dB with the 1 mm diamond burr when drilling on the promontory and 107.2 dB with the 2 mm diamond burr when the ‘blue line’ could be seen. Once the endosteal layer was exposed and touched by the cutter, maximum SPL could exceed 130 dB, which exceeds the noise level generated when the running
945
burr hits the ossicular chain [15]. Thus, their findings are similar to our results. In addition, our method does not increase any surgery procedures; we can measure noise level induced by drilling during the surgery routine. Furthermore, the method is non-invasive for measurement of noise level and can be applied in middle ear surgery and cochlear implantation in patients in the future. Meanwhile, the measurement can be performed at the round window and the silicone tube covering the microphone can easily be sterilized together with the rest of the equipment. Noise trauma has long been a concern when performing cochleostomy; more interest has been focused on minimizing the damage to the inner ear and remaining residual hearing. To successfully implement this strategy, a number of approaches have been investigated. They were as follows. (1) ‘Soft surgery,’ involving drilling a minimal cochleostomy, avoiding suction of the perilymph, and sealing the cochleostomy hole [16], or using low-speed drills or combined techniques to avoid direct mechanical and acoustic trauma [11,17]. (2) Using round window insertion techniques instead of a cochleostomy, which provided a reduced amount of drilling and minimized loss of perilymph and entry of bone dust into the scala tympani [18]. (3) Application of pharmacological agents, such as steroids and antioxidants to protect the inner ear against damage [19]. In the cadaver model, we confirmed that there are individual high noise exposures during cochleostomy, particularly after the membranous labyrinth has been exposed and touched, which could cause high sound pressure peaks of more than 130 dB SPL. Such a level is actually an extremely high risk to inner ear function. However, there is little information available as regards drill-induced noise level in actual cochleostomy; therefore, experiments in vivo are needed in the future. Acknowledgments This research project was supported by the Karolinska Institute, Tysta Skolan, Stockholm County Council (ALF-funding), Sweden and Anhui Medical University, Xi’an Jiaotong University, Jilin University, China. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References [1] Tos M, Lau T, Plate S. Sensorineural hearing loss following chronic ear surgery. Ann Otol Rhinol Laryngol 1984;93:403–9.
946
H. Yu et al.
[2] Doménech J, Carulla M, Traserra J. Sensorineural highfrequency hearing loss after drill-generated acoustic trauma in tympanoplasty. Arch Otorhinolaryngol 1989;246:280–2. [3] Farzanegan G, Ghasemi M, Panahi F, Raza M, Alghasi M. Does drill-induced noise have an impact on sensorineural hearing during craniotomy procedure? Br J Neurosurg 2010; 24:40–5. [4] Urquhart AC, McIntosh WA, Bodenstein NP. Drillgenerated sensorineural hearing loss following mastoid surgery. Laryngoscope 1992;102:689–92. [5] Hilmi OJ, Mckee RH, Abel EW, Spielmann PM, Hussain SS. Do high-speed drills generate high-frequency noise in mastoid surgery? Otol Neurotol 2012;33:2–5. [6] Kylén P, Arlinger S. Drill-generated noise levels in ear surgery. Acta Otolaryngol 1976;82:402–9. [7] Ikeya J, Kawano A, Nishiyama N, Kawaguchi S, Hagiwara A, Suzuki M. Long-term complications after cochlear implantation. Auris Nasus Larynx 2013;40:525–9. [8] Strömberg AK, Yin X, Olofsson A, Duan M. Evaluation of the usefulness of a silicone tube connected to a microphone in monitoring noise levels induced by drilling during mastoidectomy and cochleostomy. Acta Otolaryngol 2010; 130:1163–8. [9] Pau HW, Just T, Bornitz M, Lasurashvilli N, Zahnert T. Noise exposure of the inner ear during drilling a cochleostomy for cochlear implantation. Laryngoscope 2007;117:535–40. [10] Seki M, Miyasaka H, Edamatsu H, Watanabe K. Changes in permeability of strial vessels following vibration given to auditory ossicle by drill. Ann Otol Rhinol Laryngol 2001; 110:122–6. [11] Fishman AJ, Moreno LE, Rivera A, Richter CP. CO2 laser fiber soft cochleostomy: development of a technique using
[12]
[13]
[14]
[15]
[16] [17]
[18]
[19]
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