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The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important?
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ANL-2511; No. of Pages 5 Auris Nasus Larynx xxx (2018) xxx–xxx Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Jeong Hun Jang a, Hyoung Ah Mun a, Oak-Sung Choo a, Hun Yi Park a, Yun-Hoon Choung a,b,* a b
Department of Otolaryngology, Ajou University School of Medicine, Suwon, Republic of Korea BK21 Plus Research Center for Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 July 2018 Accepted 18 September 2018 Available online xxx
Objective: The outcome of cochlear implantation (CI) is affected by various factors, including the manufacturer of the device. We validated the factors contributing to postoperative performance and evaluated the influence of different company devices on pure tone thresholds and postoperative performance. Methods: Our study included 56 postlingually deaf adults who underwent CI between June 2005 and March 2016. The ears were divided into groups according to the implant manufacturer: A (n = 32 ears) and B (n = 24 ears) groups. The prognostic factors for CI outcome were evaluated using speech perception at 3, 6 and 12 months postoperatively and compared across devices. Results: The duration of hearing aid use, age at CI, and mean pure tone threshold with the implant were correlated with postoperative speech perception. The mean pure tone thresholds with the implant (averages of 0.25, 0.5, 1, 2, 4 and 6 kHz) were 27.9 3.7 dB HL in the group A and 33.5 5.6 dB HL in the group B (P < 0.01). The open-set monosyllabic word, open-set disyllabic word and open-set sentence scores were not significantly different between the groups at 3, 6 and 12 months postoperatively. Conclusion: The mean pure tone threshold with implant differed between the devices; however, no device-related effect on postoperative performance was observed. Additional multifactorial analyses are needed to clarify the relationship between free-field pure tone threshold with implant and postoperative speech perception. © 2018 Elsevier B.V. All rights reserved.
Keywords: Cochlear implantation Brand Performance Auditory threshold Speech perception
1. Introduction As cochlear implantation (CI) is the most effective rehabilitation option for patients with severe-to-profound hearing loss, the improvement in speech perception after CI is of primary concern. Previous studies have shown that post-CI
* Corresponding author at: Department of Otolaryngology, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon 443-721, Republic of Korea. E-mail address: [email protected] (Y.-H. Choung).
performance depends on several factors, including demographic and hearing characteristics and the features of the implant device [1–4]. Several factors have been assessed for their effect on post-CI performance, including age at onset of hearing loss, age at implantation, duration of deafness, aetiology, preoperative hearing, survival and location of spiral ganglion cells, patency of the scala tympani, motivation, communication mode, electrode geometry, electrode number, duration and pattern of implant use and coding strategy. In a recent study of postlingually deaf adults, Lazard et al. [5] found that the most significant factors affecting speech
https://doi.org/10.1016/j.anl.2018.09.006 0385-8146/© 2018 Elsevier B.V. All rights reserved.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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perception after CI were pure-tone average threshold of the better ear, implant device manufacturer, percentage of active electrodes, the use of hearing aids during the period of profound hearing loss and the duration of moderate hearing loss. In another study by Spahr et al. which compared the brands of implant device showed different outcomes [6]. Thus, various studies comparing postoperative CI outcomes among implant devices showed inconsistency [6–8]. Of the possible factors affecting postoperative speech perception and hearing thresholds, we paid attention to the device manufacturer. The speech perception is affected by the manufacturer such as technical characteristics of processors, speech material used, test conditions, and strategy used. Further investigation of cochlear implant systems is warranted because various devices are used and the electrodes and coding strategies differ by manufacturer. It was reported that lower sound field threshold level with CI correlated with better speech recognition [9–11]. In particular, it was suggested that sound field threshold levels of 20 dB HL throughout the frequency rage was appropriate for optimal performance [11]. We investigated factors related to postoperative performance and evaluated the influence of various cochlear implant systems on pure tone threshold and postoperative performance. 2. Materials and methods Our study was reviewed and approved by the Institutional Review Board of XXXX University Hospital (No. AJIRBMED-SUR-12-326). The requirement for informed consent was waived. The study included 56 postlingually deaf patients (23 males and 33 females) who underwent CI at the XXXX University Hospital Hearing Centre between June 2005 and March 2016. Medical records, including otological examination, hearing status, temporal bone computed tomography and surgical records were reviewed retrospectively. Patients followed for less than 1 year or whose medical records were incomplete were excluded from the study. CI was performed in 32 right ears and 24 left ears. The mean age at CI was 56.6 15.9 years, and mean duration of deafness was 9.3 9.5 years. The mean duration of hearing aid use was 7.0 8.5 years. The mean preoperative pure tone average (averages of 0.5, 1, 2 and 4 kHz) of the ears that underwent CI was 93.8 14.1 dB HL and that of the contralateral ears was 91.5 17.9 dB HL (P = 0.064). The preoperative pure tone average of CI side was better than that of the contralateral side in 27 ears. The ears were divided into two groups according to cochlear implant manufacturer; A (Cochlear Corporation, Lane Cove, New South Wales, Australia, n = 32 ears) and B (MEDEL Corporation, Innsbruck, Austria, n = 24 ears) groups. The implant device and speech processor models are shown in Table 1. Postoperative mapping was performed for each implant system following the manufacturer’s protocol. The prognostic factors associated with clinical outcome were evaluated using speech perception at 3, 6 and 12 months postoperatively. Performance was assessed using open-set monosyllabic word, open-set disyllabic word and open-set sentence recognition test scores. Phonemically balanced words were used for the monosyllabic and disyllabic word tests, and
Table 1 The distribution of internal and external devices according to the device brands of the patients. Cochlear (n = 32)
MED-EL (n = 24)
Internal device
CI24R(CA) (n = 1) CI24RE(CA) (n = 9) CI 422 (n = 20) CI 512 (n = 3)
Speech processor
Freedom (n = 5) CP 810 (n = 4) CP 910 (n = 23)
Pulsar standard (n = 1) Sonata medium (n = 2) Sonata soft flex (n = 5) Concerto flex 28 (n = 14) Concerto flex 24 (n = 2) OPUS2 (n = 19) RONDO (n = 4) Duet 2 (n = 1)
the Korean version of the Central Institute for the Deaf (K-CID) was used for the sentence test. The patients in each group were tested using their everyday device settings. All tests were performed under quiet conditions at conversational levels (range, 57–62 dB SPL). Scores were reported as the percentage of words identified correctly. Audiologic tests included the pure tone thresholds with the implant in the free field and hearing in noise test (HINT). The mean of the thresholds at 0.25, 0.5, 1, 2, 4 and 6 kHz was used to calculate the pure tone average. HINT was performed using a HINT Pro 7.2 Audiometric system (BioLogic System, Mundelein, IL, USA) with Korean HINT sentences. Speakers were located 1 m from the subject’s head at ear level and placed at a 90- angle. Signal sentences were given from the front, and speech-spectrum noise was presented from implanted ear side. Under the fixed noise level of 65 dB, the presentation level of the sentences was adjusted based on the subject’s response. The HINT threshold was determined as the level of SNR (dB) at which the subject repeats 50% of the given sentences correctly. To increase the reliability of data, stabilized results at 6 months postoperatively were used for analysis. Statistical analyses were performed using the Statistical Package for the Social Sciences version 18.0 (SPSS Inc., Chicago, IL, USA). Correlation analyses was used to identify the factors related with auditory performance after CI and Student’s T test was used to compare the variables between groups. P-values <0.05 were deemed to indicate statistical significance. 3. Results 3.1. Prognostic factors related to speech perception Active portion of electrode was 98.5 6.1% and the mean pure tone threshold with the implant was 30.1 5.3 dB HL tested in a free field. Whether the CI was performed to ear with preoperative better hearing was not related with the mean pure tone thresholds with implant. The factors related to speech perception are shown in Table 2. As age at CI was younger, the speech perception was significantly better at 3, 6, and 12 months postoperatively. The lower mean pure tone threshold with the implant was related with better disyllabic word scores at postoperative 3 months and 12 months, respectively. Interestingly, as the duration of hearing aid use was shorter, monosyllabic word, disyllabic word and open-set sentence scores were significantly better at 6 months postoperatively.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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Table 2 Factors related with auditory performance 3 months, 6 months, and 12 months after cochlear implantation.
Postoperative 3 months
Postoperative 6 months
Test material
Preoperative factors
Postoperative factors
Monosyllable word Disyllable word
( ) Age at CI (R = 0.303, P = 0.026)
Sentence
Age at CI (R = 0.353, P = 0.009)
( ) Mean hearing threshold with device (R = 0.290, P = 0.033) ( )
Monosyllable word
Age at CI (R = hearing aid use Age at CI (R = hearing aid use Age at CI (R = hearing aid use
Disyllable word Sentence Postoperative 12 months
( )
0.345, P = 0.012) Duration of (R = 0.312, R = 0.023) 0.383, P = 0.005) Duration of (R = 0.401, P = 0.003) 0.446, P = 0.001) Duration of (R = 0.348, P = 0.011)
Monosyllable word Disyllable word
Age at CI (R = 0.566, P < 0.001) Age at CI (R = 0.364, P = 0.019)
Sentence
Age at CI (R = 0.501, P = 0.001)
( ) ( ) ( ) Mean hearing threshold with device (R = 0.338, P = 0.031) ( )
CI, cochlear implantation.
The monosyllabic words score was different at only 3 months postoperatively according to the preoperative hearing level in the CI side (P < 0.05). 3.2. Comparison between device manufacturers The patient characteristics did not differ significantly between two groups, indicating that the groups were relatively well matched (Table 3). The mean pure tone thresholds with the implant (averages of 0.25, 0.5, 1, 2, 4 and 6 kHz) were 27.9 3.7 dB HL in the group A and 33.5 5.6 dB HL in the group B, which was significantly different (P < 0.001). A comparison of pure tone thresholds at each frequency revealed that the groups were significantly different at 0.25, 0.5, 1, 2, 4 and 6 kHz (P < 0.05, each). In the case of HINT, however, mean SNR was 14.4 13.1 dB in group A (n = 10) and 12.2 6.2 dB in group B (n = 13), which showed no significant difference (P > 0.05). A comparison of speech perception revealed no significant differences between groups in the monosyllabic word, disyllabic word and open-set sentence scores at 3, 6 and 12 months postoperatively (Fig. 1). In the case of group A, the lower mean pure tone thresholds with implant was related to the better open-set sentence scores at 3 months postoperatively (R = 0.418, P = 0.019) and the younger age at CI was related to the better speech perception at 6 months (disyllabic words, R = 0.464, P = 0.009; open-set sentence, R = 0.376, P = 0.041) and 12 months (monosyllabic words, R = 0.584,
P = 0.005; open-set sentence, R = 0.619, P = 0.003) postoperatively. On the contrary, only age at CI was significantly negatively correlated with the speech perception at 3 months (open-set sentence, R = 0.492, P = 0.017), 6 months (monosyllabic words, R = 0.515, P = 0.014; open-set sentence, R = 0.543, P = 0.013) and 12 months (monosyllabic words, R = 0.546, P = 0.013) postoperatively in group B.
4. Discussion In this current study, older age at CI and longer duration of hearing aid use negatively affected the speech perception after CI (Table 2). Several studies described that age at implantation had a negative effect on performance [11–13]. Holden et al. [11] suggested that this negative relation could be explained by agerelated declines in hearing and cognition in postliguistically deaf adults. In that study, predominant effect of age at CI was the reduction in performance due to cognitive ability. Lazard et al. [5] developed a predictive model of speech perception based on the findings of a multicentre study of the factors associated with CI outcome in postlingually deaf adults. In that study, the prognostic factors were suggested as follows: the pure tone average of the better ear, the brand of device, the percentage of active electrodes, the use of hearing aids, and the duration of moderate hearing loss. Although our sample size was small, the duration of hearing aid use was negatively related with CI outcome (Table 2), which was similar with another
Table 3 Preoperative and intraoperative demographic data of the patients.
Age at CI (years) Deaf duration (years) Preoperative hearing threhshold in CI-side (dB HL) Preoperative hearing threhshold in contralateral side (dB HL) Duration of hearing aid use (years) Percentile of active electrode (%)
Group A
Group B
P-value
56.4 14.9 9.9 10.1 94.7 14.7 93.7 17.8 7.1 9.2 100
56.9 17.6 8.4 8.3 92.4 13.3 88.2 18.0 6.9 7.5 96.3 9.3
>0.05 >0.05 >0.05 >0.05 >0.05 >0.05
CI, cochlear implantation.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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Fig. 1. Comparison of speech perception scores among the groups at 3, 6 and 12 months postoperatively: (a) open-set monosyllabic word scores, (b) open-set disyllabic word scores and (c) open-set sentence scores.
study [11]. The use of hearing aid before the period of severe to profound hearing loss may dampen the cognitive changes that appear with age, and should be encouraged [13]. However, the preoperative hearing thresholds in this study were more than 90 dB HL, profound hearing loss. In this condition, early CI could be more preferable to the prolonged use of hearing aid. Because the National Health Insurance Programme covers CI for only one ear in postlingually deaf adults in our country, CI was not performed to all better ears preoperatively. This was indirectly supported that preoperative better hearing was not different from preoperative worse hearing in the ears to be implanted (93.3 15.3 dB HL, 94.3 13.2 dB HL; P > 0.05). The ears to be implanted was determined by various factors such as age, side of hearing aid use, duration of deafness and residual hearing. While we matched the groups according to duration of deafness, age at CI, duration of hearing aid use and preoperative hearing threshold in the CI and contralateral ears, the mean pure tone thresholds with the implant were significantly different. This threshold difference could be explained by several perspectives: MAP, coding strategy, and microphone. MAPs are programs that help to optimise the implant user’s access to sound by adjusting the input to the electrodes on the array that is implanted into the cochlea. MAPs are definitely different between two devices. In Cochlear device, the threshold (T-level) and comfortable loudness (C-level) levels are determined for each electrode and then the dynamic range between the T- and C-levels is programmed into the device, whereas in MED-EL devices, the C-level is determined and then the T-level is automatically set to 10% of the C-level. Coding strategy, the process of encoding the acoustic signal to electric representation, could also have an effect on the mean pure tone threshold with implant. Although the Continuous Interleaved Sampling (CIS) is utilized as basic coding strategy by all modern CI programming software, the actual coding strategy of each device brand was modified version of CIS such as Advanced Combination Encoder (ACE) and Fine Structure Processing (FSP). Different MAPs and coding strategies could be related to the difference of hearing threshold with implant, which requires further evaluation. Microphone specifications may also contribute to differences in the hearing threshold among implant devices. Dual microphones, which allow directional processing, have been shown to make objective improvements in speech understand-
ing in noise [14]. Thus, dual microphones provide the best strategy for optimising speech understanding in noisy situations [15]. In our study, dual microphones were used in all Cochlear devices, whereas MED-EL devices used a single microphone. Additionally, Cochlear devices used directional microphones, which could enhance the difference of mean pure tone threshold with cochlear implant between two groups. Although the mean pure tone threshold with the implant was relatively associated with postoperative speech perception in all ears and was significantly different between two groups, the monosyllabic word, disyllabic word and sentence scores did not differ significantly between groups. These findings suggest that the difference of pure tone thresholds according to the brand of devices have little effect on the postoperative speech perception, which could be indirectly supported by similar SNR in HINT between groups. Otherwise unknown factors may have minimised the different postoperative thresholds along time. Speech perception after CI has been shown to depend on implant system characteristics such as input dynamic range (IDR), signal processing specifications, electrode design and default strategy. Haumann et al. [7] compared speech perception in patients with MED-EL, Cochlear and Advanced Bionics implants and found no difference between devices in speech testing using a fixed signal-to-noise ratio. Similarly, Harris et al. [8] found no difference in speech and music perception in patients using Cochlear and MED-EL devices. In contrast, Spahr et al. [6] reported that differences in implant design, particularly the IDR and compression method, affected patient performance. The authors found that although increasing the IDR improved speech understanding of sentences presented at low input levels (54 dB SPL), it did not have a uniform effect on sentence material presented with background noise, suggesting that the effect of IDR on speech understanding varies according to a device. However, the speech processors used by Spahr et al. [6] were an early model that is now rarely used; thus, the effect of IDR on speech perception requires further evaluation. Furthermore, the level of test difficulty and test conditions contribute to differences in the performance of cochlear implant devices. Spahr et al. [6] reported that the performance of various devices differed according to test conditions such as vowel recognition, sentence difficulty, level of presentation and noise in the environment. In that study, a battery of tests equally
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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familiar to all patients was administered and were sensitive to various aspects of speech perception to obtain maximum differences in performance. In our study, the stimuli were presented at a comfortable volume in a quiet room using materials that were familiar to the subjects, which may have minimised differences in performance among the implant devices. It is difficult to compare MAP data among various devices because signal processing differs across CI systems [16]. Moreover, MAP data are obtained by electrical stimulation and the speech perception is evaluated using different speech materials; thus, MAP data are objective and the hearing threshold is subjective. Finally, the correlation between speech perception and threshold adjustment is not definite [17]. Our study has several limitations. As shown in Table 1, the sample size was small and our study utilised a heterogeneous mix of implant devices and speech processors. All these factors might affect the hearing threshold and performance as well, which may have led to erroneous conclusions. While the type of electrode was heterogeneous in group A (perimodiolar and straight), all electrode arrays were straight in group B. MAP and directional microphone are similar in speech processors in group A and the technical specification of speech processor was same in group B. 5. Conclusions Speech perception after CI may be affected by several prognostic factors. Although the free-field pure tone threshold differed among the implant systems assessed in our study, speech perception was not significantly different. Additional multifactorial analyses are needed to clarify the relationship between free-field pure tone threshold with implant and postoperative speech perception. Acknowledgements This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (NRF-2015R1C1A1A02036457). This work was supported by the faculty research fund of Ajou University School of Medicine. References [1] O’Donoghue GM, Nikolopoulos TP, Archbold SM. Determinants of speech perception in children after cochlear implantation. Lancet 2000;356(9228):466–8.
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[2] Gomaa NA, Rubinstein JT, Lowder MW, Tyler RS, Gantz BJ. Residual speech perception and cochlear implant performance in postlingually deafened adults. Ear Hear 2003;24(6):539–44. [3] Semenov YR, Martinez-Monedero R, Niparko JK. Cochlear implants: clinical and societal outcomes. Otolaryngol Clin North Am 2012;45 (5):959–81. [4] Kang DH, Lee MJ, Lee KY, Lee SH, Jang JH. Prediction of cochlear implant outcomes in patients with prelingual deafness. Clin Exp Otorhinolaryngol 2016;9(3):220–5. [5] Lazard DS, Vincent C, Venail F, Van de Heyning P, Truy E, Sterkers O, et al. Pre-, per- and postoperative factors affecting performance of postlinguistically deaf adults using cochlear implants: a new conceptual model over time. PLoS One 2012;7(11):e48739. [6] Spahr AJ, Dorman MF, Loiselle LH. Performance of patients using different cochlear implant systems: effects of input dynamic range. Ear Hear 2007;28(2):260–75. [7] Haumann S, Lenarz T, Buchner A. Speech perception with cochlear implants as measured using a roving-level adaptive test method. J Otorhinolaryngol Relat Spec 2010;72(6):312–8. [8] Harris RL, Gibson WP, Johnson M, Brew J, Bray M, Psarros C. Intraindividual assessment of speech and music perception in cochlear implant users with contralateral cochlear and MED-EL systems. Acta Otolaryngol 2011;131(12):1270–8. [9] Davidson LS, Skinner MW, Holstad BA, Fears BT, Richter MK, Matusofsky M, et al. The effect of instantaneous input dynamic range setting on the speech perception of children with the nucleus 24 implant. Ear Hear 2009;30(3):340–9. [10] Firszt JB, Holden LK, Skinner MW, Tobey EA, Peterson A, Gaggl W, et al. Recognition of speech presented at soft to loud levels by adult cochlear implant recipients of three cochlear implant systems. Ear Hear 2004;25(4):375–87. [11] Holden LK, Finley CC, Firszt JB, Holden TA, Brenner C, Potts LG, et al. Factors affecting open-set word recognition in adults with cochlear implants. Ear Hear 2013;34(3):342–60. [12] Blamey P, Arndt P, Bergeron F, Bredberg G, Brimacombe J, Facer G, et al. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants. Audiol Neurootol 1996;1(5):293–306. [13] Blamey P, Artieres F, Baskent D, Bergeron F, Beynon A, Burke E, et al. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants: an update with 2251 patients. Audiol Neurootol 2013;18(1):36–47. [14] Hersbach AA, Arora K, Mauger SJ, Dawson PW. Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users. Ear Hear 2012;33(4):e13–23. [15] Wolfe J, Parkinson A, Schafer EC, Gilden J, Rehwinkel K, Mansanares J, et al. Benefit of a commercially available cochlear implant processor with dual-microphone beamforming: a multi-center study. Otol Neurotol 2012;33(4):553–60. [16] Vaerenberg B, Govaerts PJ, Stainsby T, Nopp P, Gault A, Gnansia D. A uniform graphical representation of intensity coding in current-generation cochlear implant systems. Ear Hear 2014;35(5):533–43. [17] Busby PA, Arora K. Effects of threshold adjustment on speech perception in nucleus cochlear implant recipients. Ear Hear 2016;37 (3):303–11.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
ANL-2511; No. of Pages 5 Auris Nasus Larynx xxx (2018) xxx–xxx Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Jeong Hun Jang a, Hyoung Ah Mun a, Oak-Sung Choo a, Hun Yi Park a, Yun-Hoon Choung a,b,* a b
Department of Otolaryngology, Ajou University School of Medicine, Suwon, Republic of Korea BK21 Plus Research Center for Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 July 2018 Accepted 18 September 2018 Available online xxx
Objective: The outcome of cochlear implantation (CI) is affected by various factors, including the manufacturer of the device. We validated the factors contributing to postoperative performance and evaluated the influence of different company devices on pure tone thresholds and postoperative performance. Methods: Our study included 56 postlingually deaf adults who underwent CI between June 2005 and March 2016. The ears were divided into groups according to the implant manufacturer: A (n = 32 ears) and B (n = 24 ears) groups. The prognostic factors for CI outcome were evaluated using speech perception at 3, 6 and 12 months postoperatively and compared across devices. Results: The duration of hearing aid use, age at CI, and mean pure tone threshold with the implant were correlated with postoperative speech perception. The mean pure tone thresholds with the implant (averages of 0.25, 0.5, 1, 2, 4 and 6 kHz) were 27.9 3.7 dB HL in the group A and 33.5 5.6 dB HL in the group B (P < 0.01). The open-set monosyllabic word, open-set disyllabic word and open-set sentence scores were not significantly different between the groups at 3, 6 and 12 months postoperatively. Conclusion: The mean pure tone threshold with implant differed between the devices; however, no device-related effect on postoperative performance was observed. Additional multifactorial analyses are needed to clarify the relationship between free-field pure tone threshold with implant and postoperative speech perception. © 2018 Elsevier B.V. All rights reserved.
Keywords: Cochlear implantation Brand Performance Auditory threshold Speech perception
1. Introduction As cochlear implantation (CI) is the most effective rehabilitation option for patients with severe-to-profound hearing loss, the improvement in speech perception after CI is of primary concern. Previous studies have shown that post-CI
* Corresponding author at: Department of Otolaryngology, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon 443-721, Republic of Korea. E-mail address: [email protected] (Y.-H. Choung).
performance depends on several factors, including demographic and hearing characteristics and the features of the implant device [1–4]. Several factors have been assessed for their effect on post-CI performance, including age at onset of hearing loss, age at implantation, duration of deafness, aetiology, preoperative hearing, survival and location of spiral ganglion cells, patency of the scala tympani, motivation, communication mode, electrode geometry, electrode number, duration and pattern of implant use and coding strategy. In a recent study of postlingually deaf adults, Lazard et al. [5] found that the most significant factors affecting speech
https://doi.org/10.1016/j.anl.2018.09.006 0385-8146/© 2018 Elsevier B.V. All rights reserved.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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ANL-2511; No. of Pages 5 J.H. Jang et al. / Auris Nasus Larynx xxx (2018) xxx–xxx
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perception after CI were pure-tone average threshold of the better ear, implant device manufacturer, percentage of active electrodes, the use of hearing aids during the period of profound hearing loss and the duration of moderate hearing loss. In another study by Spahr et al. which compared the brands of implant device showed different outcomes [6]. Thus, various studies comparing postoperative CI outcomes among implant devices showed inconsistency [6–8]. Of the possible factors affecting postoperative speech perception and hearing thresholds, we paid attention to the device manufacturer. The speech perception is affected by the manufacturer such as technical characteristics of processors, speech material used, test conditions, and strategy used. Further investigation of cochlear implant systems is warranted because various devices are used and the electrodes and coding strategies differ by manufacturer. It was reported that lower sound field threshold level with CI correlated with better speech recognition [9–11]. In particular, it was suggested that sound field threshold levels of 20 dB HL throughout the frequency rage was appropriate for optimal performance [11]. We investigated factors related to postoperative performance and evaluated the influence of various cochlear implant systems on pure tone threshold and postoperative performance. 2. Materials and methods Our study was reviewed and approved by the Institutional Review Board of XXXX University Hospital (No. AJIRBMED-SUR-12-326). The requirement for informed consent was waived. The study included 56 postlingually deaf patients (23 males and 33 females) who underwent CI at the XXXX University Hospital Hearing Centre between June 2005 and March 2016. Medical records, including otological examination, hearing status, temporal bone computed tomography and surgical records were reviewed retrospectively. Patients followed for less than 1 year or whose medical records were incomplete were excluded from the study. CI was performed in 32 right ears and 24 left ears. The mean age at CI was 56.6 15.9 years, and mean duration of deafness was 9.3 9.5 years. The mean duration of hearing aid use was 7.0 8.5 years. The mean preoperative pure tone average (averages of 0.5, 1, 2 and 4 kHz) of the ears that underwent CI was 93.8 14.1 dB HL and that of the contralateral ears was 91.5 17.9 dB HL (P = 0.064). The preoperative pure tone average of CI side was better than that of the contralateral side in 27 ears. The ears were divided into two groups according to cochlear implant manufacturer; A (Cochlear Corporation, Lane Cove, New South Wales, Australia, n = 32 ears) and B (MEDEL Corporation, Innsbruck, Austria, n = 24 ears) groups. The implant device and speech processor models are shown in Table 1. Postoperative mapping was performed for each implant system following the manufacturer’s protocol. The prognostic factors associated with clinical outcome were evaluated using speech perception at 3, 6 and 12 months postoperatively. Performance was assessed using open-set monosyllabic word, open-set disyllabic word and open-set sentence recognition test scores. Phonemically balanced words were used for the monosyllabic and disyllabic word tests, and
Table 1 The distribution of internal and external devices according to the device brands of the patients. Cochlear (n = 32)
MED-EL (n = 24)
Internal device
CI24R(CA) (n = 1) CI24RE(CA) (n = 9) CI 422 (n = 20) CI 512 (n = 3)
Speech processor
Freedom (n = 5) CP 810 (n = 4) CP 910 (n = 23)
Pulsar standard (n = 1) Sonata medium (n = 2) Sonata soft flex (n = 5) Concerto flex 28 (n = 14) Concerto flex 24 (n = 2) OPUS2 (n = 19) RONDO (n = 4) Duet 2 (n = 1)
the Korean version of the Central Institute for the Deaf (K-CID) was used for the sentence test. The patients in each group were tested using their everyday device settings. All tests were performed under quiet conditions at conversational levels (range, 57–62 dB SPL). Scores were reported as the percentage of words identified correctly. Audiologic tests included the pure tone thresholds with the implant in the free field and hearing in noise test (HINT). The mean of the thresholds at 0.25, 0.5, 1, 2, 4 and 6 kHz was used to calculate the pure tone average. HINT was performed using a HINT Pro 7.2 Audiometric system (BioLogic System, Mundelein, IL, USA) with Korean HINT sentences. Speakers were located 1 m from the subject’s head at ear level and placed at a 90- angle. Signal sentences were given from the front, and speech-spectrum noise was presented from implanted ear side. Under the fixed noise level of 65 dB, the presentation level of the sentences was adjusted based on the subject’s response. The HINT threshold was determined as the level of SNR (dB) at which the subject repeats 50% of the given sentences correctly. To increase the reliability of data, stabilized results at 6 months postoperatively were used for analysis. Statistical analyses were performed using the Statistical Package for the Social Sciences version 18.0 (SPSS Inc., Chicago, IL, USA). Correlation analyses was used to identify the factors related with auditory performance after CI and Student’s T test was used to compare the variables between groups. P-values <0.05 were deemed to indicate statistical significance. 3. Results 3.1. Prognostic factors related to speech perception Active portion of electrode was 98.5 6.1% and the mean pure tone threshold with the implant was 30.1 5.3 dB HL tested in a free field. Whether the CI was performed to ear with preoperative better hearing was not related with the mean pure tone thresholds with implant. The factors related to speech perception are shown in Table 2. As age at CI was younger, the speech perception was significantly better at 3, 6, and 12 months postoperatively. The lower mean pure tone threshold with the implant was related with better disyllabic word scores at postoperative 3 months and 12 months, respectively. Interestingly, as the duration of hearing aid use was shorter, monosyllabic word, disyllabic word and open-set sentence scores were significantly better at 6 months postoperatively.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006
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Table 2 Factors related with auditory performance 3 months, 6 months, and 12 months after cochlear implantation.
Postoperative 3 months
Postoperative 6 months
Test material
Preoperative factors
Postoperative factors
Monosyllable word Disyllable word
( ) Age at CI (R = 0.303, P = 0.026)
Sentence
Age at CI (R = 0.353, P = 0.009)
( ) Mean hearing threshold with device (R = 0.290, P = 0.033) ( )
Monosyllable word
Age at CI (R = hearing aid use Age at CI (R = hearing aid use Age at CI (R = hearing aid use
Disyllable word Sentence Postoperative 12 months
( )
0.345, P = 0.012) Duration of (R = 0.312, R = 0.023) 0.383, P = 0.005) Duration of (R = 0.401, P = 0.003) 0.446, P = 0.001) Duration of (R = 0.348, P = 0.011)
Monosyllable word Disyllable word
Age at CI (R = 0.566, P < 0.001) Age at CI (R = 0.364, P = 0.019)
Sentence
Age at CI (R = 0.501, P = 0.001)
( ) ( ) ( ) Mean hearing threshold with device (R = 0.338, P = 0.031) ( )
CI, cochlear implantation.
The monosyllabic words score was different at only 3 months postoperatively according to the preoperative hearing level in the CI side (P < 0.05). 3.2. Comparison between device manufacturers The patient characteristics did not differ significantly between two groups, indicating that the groups were relatively well matched (Table 3). The mean pure tone thresholds with the implant (averages of 0.25, 0.5, 1, 2, 4 and 6 kHz) were 27.9 3.7 dB HL in the group A and 33.5 5.6 dB HL in the group B, which was significantly different (P < 0.001). A comparison of pure tone thresholds at each frequency revealed that the groups were significantly different at 0.25, 0.5, 1, 2, 4 and 6 kHz (P < 0.05, each). In the case of HINT, however, mean SNR was 14.4 13.1 dB in group A (n = 10) and 12.2 6.2 dB in group B (n = 13), which showed no significant difference (P > 0.05). A comparison of speech perception revealed no significant differences between groups in the monosyllabic word, disyllabic word and open-set sentence scores at 3, 6 and 12 months postoperatively (Fig. 1). In the case of group A, the lower mean pure tone thresholds with implant was related to the better open-set sentence scores at 3 months postoperatively (R = 0.418, P = 0.019) and the younger age at CI was related to the better speech perception at 6 months (disyllabic words, R = 0.464, P = 0.009; open-set sentence, R = 0.376, P = 0.041) and 12 months (monosyllabic words, R = 0.584,
P = 0.005; open-set sentence, R = 0.619, P = 0.003) postoperatively. On the contrary, only age at CI was significantly negatively correlated with the speech perception at 3 months (open-set sentence, R = 0.492, P = 0.017), 6 months (monosyllabic words, R = 0.515, P = 0.014; open-set sentence, R = 0.543, P = 0.013) and 12 months (monosyllabic words, R = 0.546, P = 0.013) postoperatively in group B.
4. Discussion In this current study, older age at CI and longer duration of hearing aid use negatively affected the speech perception after CI (Table 2). Several studies described that age at implantation had a negative effect on performance [11–13]. Holden et al. [11] suggested that this negative relation could be explained by agerelated declines in hearing and cognition in postliguistically deaf adults. In that study, predominant effect of age at CI was the reduction in performance due to cognitive ability. Lazard et al. [5] developed a predictive model of speech perception based on the findings of a multicentre study of the factors associated with CI outcome in postlingually deaf adults. In that study, the prognostic factors were suggested as follows: the pure tone average of the better ear, the brand of device, the percentage of active electrodes, the use of hearing aids, and the duration of moderate hearing loss. Although our sample size was small, the duration of hearing aid use was negatively related with CI outcome (Table 2), which was similar with another
Table 3 Preoperative and intraoperative demographic data of the patients.
Age at CI (years) Deaf duration (years) Preoperative hearing threhshold in CI-side (dB HL) Preoperative hearing threhshold in contralateral side (dB HL) Duration of hearing aid use (years) Percentile of active electrode (%)
Group A
Group B
P-value
56.4 14.9 9.9 10.1 94.7 14.7 93.7 17.8 7.1 9.2 100
56.9 17.6 8.4 8.3 92.4 13.3 88.2 18.0 6.9 7.5 96.3 9.3
>0.05 >0.05 >0.05 >0.05 >0.05 >0.05
CI, cochlear implantation.
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Fig. 1. Comparison of speech perception scores among the groups at 3, 6 and 12 months postoperatively: (a) open-set monosyllabic word scores, (b) open-set disyllabic word scores and (c) open-set sentence scores.
study [11]. The use of hearing aid before the period of severe to profound hearing loss may dampen the cognitive changes that appear with age, and should be encouraged [13]. However, the preoperative hearing thresholds in this study were more than 90 dB HL, profound hearing loss. In this condition, early CI could be more preferable to the prolonged use of hearing aid. Because the National Health Insurance Programme covers CI for only one ear in postlingually deaf adults in our country, CI was not performed to all better ears preoperatively. This was indirectly supported that preoperative better hearing was not different from preoperative worse hearing in the ears to be implanted (93.3 15.3 dB HL, 94.3 13.2 dB HL; P > 0.05). The ears to be implanted was determined by various factors such as age, side of hearing aid use, duration of deafness and residual hearing. While we matched the groups according to duration of deafness, age at CI, duration of hearing aid use and preoperative hearing threshold in the CI and contralateral ears, the mean pure tone thresholds with the implant were significantly different. This threshold difference could be explained by several perspectives: MAP, coding strategy, and microphone. MAPs are programs that help to optimise the implant user’s access to sound by adjusting the input to the electrodes on the array that is implanted into the cochlea. MAPs are definitely different between two devices. In Cochlear device, the threshold (T-level) and comfortable loudness (C-level) levels are determined for each electrode and then the dynamic range between the T- and C-levels is programmed into the device, whereas in MED-EL devices, the C-level is determined and then the T-level is automatically set to 10% of the C-level. Coding strategy, the process of encoding the acoustic signal to electric representation, could also have an effect on the mean pure tone threshold with implant. Although the Continuous Interleaved Sampling (CIS) is utilized as basic coding strategy by all modern CI programming software, the actual coding strategy of each device brand was modified version of CIS such as Advanced Combination Encoder (ACE) and Fine Structure Processing (FSP). Different MAPs and coding strategies could be related to the difference of hearing threshold with implant, which requires further evaluation. Microphone specifications may also contribute to differences in the hearing threshold among implant devices. Dual microphones, which allow directional processing, have been shown to make objective improvements in speech understand-
ing in noise [14]. Thus, dual microphones provide the best strategy for optimising speech understanding in noisy situations [15]. In our study, dual microphones were used in all Cochlear devices, whereas MED-EL devices used a single microphone. Additionally, Cochlear devices used directional microphones, which could enhance the difference of mean pure tone threshold with cochlear implant between two groups. Although the mean pure tone threshold with the implant was relatively associated with postoperative speech perception in all ears and was significantly different between two groups, the monosyllabic word, disyllabic word and sentence scores did not differ significantly between groups. These findings suggest that the difference of pure tone thresholds according to the brand of devices have little effect on the postoperative speech perception, which could be indirectly supported by similar SNR in HINT between groups. Otherwise unknown factors may have minimised the different postoperative thresholds along time. Speech perception after CI has been shown to depend on implant system characteristics such as input dynamic range (IDR), signal processing specifications, electrode design and default strategy. Haumann et al. [7] compared speech perception in patients with MED-EL, Cochlear and Advanced Bionics implants and found no difference between devices in speech testing using a fixed signal-to-noise ratio. Similarly, Harris et al. [8] found no difference in speech and music perception in patients using Cochlear and MED-EL devices. In contrast, Spahr et al. [6] reported that differences in implant design, particularly the IDR and compression method, affected patient performance. The authors found that although increasing the IDR improved speech understanding of sentences presented at low input levels (54 dB SPL), it did not have a uniform effect on sentence material presented with background noise, suggesting that the effect of IDR on speech understanding varies according to a device. However, the speech processors used by Spahr et al. [6] were an early model that is now rarely used; thus, the effect of IDR on speech perception requires further evaluation. Furthermore, the level of test difficulty and test conditions contribute to differences in the performance of cochlear implant devices. Spahr et al. [6] reported that the performance of various devices differed according to test conditions such as vowel recognition, sentence difficulty, level of presentation and noise in the environment. In that study, a battery of tests equally
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familiar to all patients was administered and were sensitive to various aspects of speech perception to obtain maximum differences in performance. In our study, the stimuli were presented at a comfortable volume in a quiet room using materials that were familiar to the subjects, which may have minimised differences in performance among the implant devices. It is difficult to compare MAP data among various devices because signal processing differs across CI systems [16]. Moreover, MAP data are obtained by electrical stimulation and the speech perception is evaluated using different speech materials; thus, MAP data are objective and the hearing threshold is subjective. Finally, the correlation between speech perception and threshold adjustment is not definite [17]. Our study has several limitations. As shown in Table 1, the sample size was small and our study utilised a heterogeneous mix of implant devices and speech processors. All these factors might affect the hearing threshold and performance as well, which may have led to erroneous conclusions. While the type of electrode was heterogeneous in group A (perimodiolar and straight), all electrode arrays were straight in group B. MAP and directional microphone are similar in speech processors in group A and the technical specification of speech processor was same in group B. 5. Conclusions Speech perception after CI may be affected by several prognostic factors. Although the free-field pure tone threshold differed among the implant systems assessed in our study, speech perception was not significantly different. Additional multifactorial analyses are needed to clarify the relationship between free-field pure tone threshold with implant and postoperative speech perception. Acknowledgements This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (NRF-2015R1C1A1A02036457). This work was supported by the faculty research fund of Ajou University School of Medicine. References [1] O’Donoghue GM, Nikolopoulos TP, Archbold SM. Determinants of speech perception in children after cochlear implantation. Lancet 2000;356(9228):466–8.
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[2] Gomaa NA, Rubinstein JT, Lowder MW, Tyler RS, Gantz BJ. Residual speech perception and cochlear implant performance in postlingually deafened adults. Ear Hear 2003;24(6):539–44. [3] Semenov YR, Martinez-Monedero R, Niparko JK. Cochlear implants: clinical and societal outcomes. Otolaryngol Clin North Am 2012;45 (5):959–81. [4] Kang DH, Lee MJ, Lee KY, Lee SH, Jang JH. Prediction of cochlear implant outcomes in patients with prelingual deafness. Clin Exp Otorhinolaryngol 2016;9(3):220–5. [5] Lazard DS, Vincent C, Venail F, Van de Heyning P, Truy E, Sterkers O, et al. Pre-, per- and postoperative factors affecting performance of postlinguistically deaf adults using cochlear implants: a new conceptual model over time. PLoS One 2012;7(11):e48739. [6] Spahr AJ, Dorman MF, Loiselle LH. Performance of patients using different cochlear implant systems: effects of input dynamic range. Ear Hear 2007;28(2):260–75. [7] Haumann S, Lenarz T, Buchner A. Speech perception with cochlear implants as measured using a roving-level adaptive test method. J Otorhinolaryngol Relat Spec 2010;72(6):312–8. [8] Harris RL, Gibson WP, Johnson M, Brew J, Bray M, Psarros C. Intraindividual assessment of speech and music perception in cochlear implant users with contralateral cochlear and MED-EL systems. Acta Otolaryngol 2011;131(12):1270–8. [9] Davidson LS, Skinner MW, Holstad BA, Fears BT, Richter MK, Matusofsky M, et al. The effect of instantaneous input dynamic range setting on the speech perception of children with the nucleus 24 implant. Ear Hear 2009;30(3):340–9. [10] Firszt JB, Holden LK, Skinner MW, Tobey EA, Peterson A, Gaggl W, et al. Recognition of speech presented at soft to loud levels by adult cochlear implant recipients of three cochlear implant systems. Ear Hear 2004;25(4):375–87. [11] Holden LK, Finley CC, Firszt JB, Holden TA, Brenner C, Potts LG, et al. Factors affecting open-set word recognition in adults with cochlear implants. Ear Hear 2013;34(3):342–60. [12] Blamey P, Arndt P, Bergeron F, Bredberg G, Brimacombe J, Facer G, et al. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants. Audiol Neurootol 1996;1(5):293–306. [13] Blamey P, Artieres F, Baskent D, Bergeron F, Beynon A, Burke E, et al. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants: an update with 2251 patients. Audiol Neurootol 2013;18(1):36–47. [14] Hersbach AA, Arora K, Mauger SJ, Dawson PW. Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users. Ear Hear 2012;33(4):e13–23. [15] Wolfe J, Parkinson A, Schafer EC, Gilden J, Rehwinkel K, Mansanares J, et al. Benefit of a commercially available cochlear implant processor with dual-microphone beamforming: a multi-center study. Otol Neurotol 2012;33(4):553–60. [16] Vaerenberg B, Govaerts PJ, Stainsby T, Nopp P, Gault A, Gnansia D. A uniform graphical representation of intensity coding in current-generation cochlear implant systems. Ear Hear 2014;35(5):533–43. [17] Busby PA, Arora K. Effects of threshold adjustment on speech perception in nucleus cochlear implant recipients. Ear Hear 2016;37 (3):303–11.
Please cite this article in press as: Jang JH, et al. The speech perception after cochlear implantation: The hearing gain difference according to the implant systems is important? Auris Nasus Larynx (2018), https://doi.org/10.1016/j.anl.2018.09.006