Early Outcomes After Cochlear Implantation for Adults and Children With Unilateral Hearing Loss

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1 The Laryngoscope VC 2016 The American Laryngological, Rhinological and Otological Society, Inc. Early Outcomes After Cochlear Implantation for Adults and Children With Unilateral Hearing Loss Douglas P. Sladen, PhD; Matthew L. Carlson, MD; Brittany P. Dowling, AuD; Amy P. Olund, AuD; Kathryn Teece, AuD; Melissa D. DeJong, AuD; Alyce Breneman, AuD; Ann Peterson, MA; Charles W. Beatty, MD; Brian A. Neff, MD; Colin L. Driscoll, MD Objectives/Hypothesis: This study was designed to examine speech recognition and self-perceived health-related quality of life (HRQoL) received from cochlear implantation among a cohort of adults and children with a short duration of unilateral hearing loss greater than 6 months, but less than 2 years. Study Design: Single-subject repeated measures prospective study. Methods: This study assessed changes in speech recognition and self-perceived quality of life by prospectively analyzing data at the preoperative evaluation and at the 3-month and 6-month postactivation intervals. Measurement tools included Medical Outcomes Study Questionnaire Short Form 36, Nijmegen Cochlear Implant Questionnaire, Speech Spatial and Qualities of Hearing Comparative, and speech recognition measures in quiet and in noise. Results: Results indicated significant improvement in speech recognition, both in quiet and noise. Quality-of-life measures showed a significant increase in self-perceived benefit with disease-specific instruments, but remained constant with a generic HRQoL instrument. Conclusions: Cochlear implantation was a successful intervention for improved hearing in quiet and noise, and a selfperceived benefit for this group of adults and children with a short duration of unilateral hearing loss. Key Words: Cochlear implantation, unilateral hearing loss, single-sided deafness, sudden sensorineural hearing loss, quality of life, sound localization. Level of Evidence: 4 Laryngoscope, 127: , 2017 INTRODUCTION Sudden sensorineural hearing loss occurs in approximately 5 to 20 per 100,000 persons per year and is nearly always unilateral. 1 3 Unilateral hearing loss (UHL) impairs speech recognition on the affected side and results in loss of binaural hearing. The loss of binaural hearing is not inconsequential and is known to negatively affect speech recognition in noise, sound localization, and overall quality of life (QoL). 4 7 The advantages of binaural hearing arise from three mechanisms: head shadow, binaural squelch, and binaural summation. 8 The head shadow affect is not actually a binaural hearing process, but rather a consequence of hearing on both sides, which permits the listener to take advantage of a greater signal-to-noise ratio From the Department of Otorhinolaryngology, Division of Audiology, Mayo Clinic School of Medicine, Rochester, Minnesota, U.S.A. Editor s Note: This Manuscript was accepted for publication August 25, A portion of these data was presented at the American Cochlear Implant Alliance Meeting, Washington, DC, U.S.A., October 15, M.L.C. is a consultant for MED-EL GmbH. C.L.D. is a consultant for Advanced Bionics Corp., Cochlear Corp., and MED-EL GmbH. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Douglas P. Sladen, PhD, Department of Otolaryngology, Division of Audiology, Mayo Clinic, 200 First Street SW, Rochester, MN sladen.douglas@mayo.edu DOI: /lary (SNR) when speech is directed to either ear. The benefit of head shadow is pronounced in the high frequencies, amounting to 10 to 16 db above 1,000 Hz. 9 Binaural squelch occurs when input from both ears is analyzed by the brain and can provide a 2- to 4.9-dB improvement in speech recognition threshold. 8,10 Binaural summation occurs when identical signals arrive at the two ears. The redundant information received by the two ears can improve speech perception by 1 to 2 db in subjects with normal hearing. 11 Conventional treatment options for UHL include devices that route sound from the affected side to the normal hearing ear, such as a contralateral routing of sound hearing aid or an osseointegrated device. Though these devices generally offer improved speech recognition in noise, most reports suggest they do not result in improved accuracy of sound localization, and they do not restore binaural hearing. 12 Cochlear implants (CI) are unique in that they restore sound in the deafened ear rather than routing sound to the better hearing side. As such, cochlear implantation has been suggested as an alternative treatment for restoration of binaural hearing. It is important to note that a CI provides an adequate signal optimized for understanding speech, though it is a degraded signal compared to normal hearing. Therefore, it is possible that bilateral input, with normal hearing on one side and a CI on the other, will not successfully restore the binaural advantage. In fact, there is 1683

2 TABLE I. Participants Demographics. Participant Age at Implantation, yr Etiology of Deafness Duration of Deafness, mo Device 1 32 Otosclerosis 14 Concert Flex Idiopathic sudden SNHL 12 Concert Flex Idiopathic sudden SNHL 20 Concert Flex Idiopathic sudden SNHL 13 Concert Flex Otosclerosis 22 CI Vestibular schwannoma 18 Concert Flex Idiopathic sudden SNHL 23 CI Idiopathic sudden SNHL 20 CI Idiopathic sudden SNHL 21 Concert Flex Idiopathic sudden SNHL 23 Concert Flex Cholesteatoma 22 CI24RE(CA) Idiopathic sudden SNHL 18 Advantage MidScala Idiopathic sudden SNHL 21 CI Idiopathic sudden SNHL 22 CI Bacterial sepsis sudden SNHL 20 Synchrony Flex Idiopathic sudden SNHL 14 CI Idiopathic sudden SNHL 16 Synchrony Flex Idiopathic sudden SNHL 15 Synchrony Flex Idiopathic sudden SNHL 18 Synchrony Flex Idiopathic sudden SNHL 20 Synchrony Flex 28 SNHL 5 sensorineural hearing loss. some evidence that an asymmetric or degraded signal to one ear may actually interfere with binaural processing, such as understanding speech in noise. 13 The emerging research in this area, however, is promising, and demonstrates that patients with UHL who receive a CI on the impaired side may benefit from improved speech recognition, improved sound localization, and potentially improved speech recognition in some difficult listening situations In addition to speech recognition and localization, some investigators have noted that CI recipients with UHL report improved health-related QoL (HRQoL). 14,19 The aim of the current study was to examine if a CI would improve hearing to the affected side of those with UHL as well as provide partial hearing restoration to the binaural system and improved overall QoL. MATERIALS AND METHODS The current study utilized a prospective single-arm, repeated-measures design. Institutional review board (IRB# ) approval was obtained prior to study commencement. Participation in this study required at least moderate-to-severe sensorineural hearing loss in the ipsilateral ear and monosyllabic word scores of less than 50% when tested in the ipsilateral aided condition. The contralateral ear required normal hearing, defined as acoustic thresholds better than or equal to 25 db between 250 and 2,000 Hz. Participants At the time of this writing, 20 participants with UHL have been implanted and met inclusion criteria. Of those participants, 15 have reached the 6-month postactivation point and were included in the final data analysis. The entire group was comprised of 13 adults and two children, ranging in age from 11 to 65 years (mean 5 42 years). Duration of UHL and presence of tinnitus was determined through review of the medical records and/or patient report. Duration of deafness ranged between 12 and 23 months, with an average of 18 months. Demographic information for each participant is detailed in Table I. Materials Pure-tone air- and bone-conduction audiometry was tested using insert ER3 headphones (Etymotic Research, Inc., Elk Grove Village, IL) and a calibrated Astera audiometer (GN Otometrics A/S, Taastrup, Denmark). Speech recognition was assessed in quiet using the consonant-nucleus-consonant (CNC) word test and Arizona Biomedical Institute (AzBio) sentence test. 20,21 Speech recognition in diffuse noise was assessed using the Hearing In Noise Test (HINT) sentences. 22 The background noise for the HINT testing was comprised of restaurant noise replicating real-world competing background noise. 23 All testing was completed in a double-walled sound-attenuated booth. Three measures of HRQoL were utilized. Generic HRQoL was measured using the Medical Outcomes Study Questionnaire Short Form 36 (SF-36). 24 The SF-36 is comprised of 36 items that cover eight health domains. This measure was included because cochlear implantation of UHL is a new practice in the United States, and the authors intend to demonstrate that CI intervention is not harmful to overall HRQoL. Two disease-specific measures of HRQoL were also included: the Njimegen Cochlear Implant Questionnaire (NCIQ) and the Speech Spatial and Qualities of Hearing Comparative (SSQ-C). 25,26 The NCIQ consists of 60 items covering six

3 domains: self-perceived ability of basic sound processing, advanced sound processing, speech production, self-esteem, activity limitations, and social interactions. The SSQ-C is comprised of 46 questions that evaluate three domains: speech, spatial, and qualities. Procedures Pure-tone air- and bone-conduction thresholds were measured preoperatively, then again at initial activation and 3 months postactivation for both ears. Speech recognition in quiet was measured preoperatively, then again at 3 and 6 months postactivation. Speech recognition in quiet was measured for the implanted ear only at the preoperative then at 3 and 6 months postactivation. Speech understanding in noise was measured in the bilateral condition (implant on) and unilateral (implant off) condition at the 6-month postactivation test interval only. Preoperative testing was completed with a personal or loaned hearing aid set to National Acoustic Laboratories prescriptive targets within 5 db. 27 Speech recognition in quiet was tested in a sound booth at a calibrated 60 dba SPL presentation level, with the target speaker at 08 azimuth, and masking presented to the contralateral, normal-hearing ear using an insert earphone. Postactivation speech recognition in quiet was tested using a direct audio input cable from a laptop to the participants processor. The volume was set to 80%, then the participant was asked to judge if it was a comfortable volume. Adjustments were made up and down if necessary. Postactivation speech recognition in noise was tested with the sound processor on and off. Testing was completed using the Revitronix (Braintree, VT) R-SPACE environment simulation system. 23 This system consists of an eight-speaker array placed circumferentially around the subject s head. Each loudspeaker is placed at ear level at a distance of 2 feet from the subject. HINT sentence recognition was assessed with the target speech presented from 08 azimuth and noise presented from all eight speakers at a fixed 72 db SPL presentation level to approximate the average noise level of a restaurant. The presentation level of the sentences was varied adaptively in 2-dB steps to achieve the SNR needed for a speech reception threshold (SRT). The SF-36 and NCIQ assessment tools were administered preoperatively, then again at 6 months postactivation, whereas the SSQ-C was administered only at 6 months postactivation. Each was scored according to the instructions provided by the respective authors. Statistical Analysis Speech perception performance was scored as percent correct. The percent correct scores often fell below 20% or above 80%. To avoid the floor and ceiling effects, all speech perception data were subjected to an arcsine transformation prior to statistical analysis. 28 Data are therefore reported either as percent correct or as rationalized arcsine units (RAU). Statistical analyses were completed using IBM SPSS Statistical Package version (IBM, Armonk, NY). An a level of.05 was used to determine statistical significance. RESULTS Pure-Tone Audiometrics Preoperative air conduction thresholds for the implanted ears can be found in Figure 1. The pure-tone average (500, 1,000, 2,000 Hz average) was 78 db HL (standard deviation [SD] ) for the affected side and 12 db HL (SD 5 7.4) for the contralateral ear. There were four participants with mild high-frequency hearing Fig. 1. Preoperative hearing threshold data for each participant are shown by the dashed grey lines. The average preoperative hearing thresholds are shown by the solid black line. loss, though for the purpose of this study they were considered functionally UHL. The average pure-tone air-conduction threshold at 3 months postactivation was db HL (SD 5 20 db). Postoperative acoustic thresholds in the implanted ear ranged from 80 db HL to no response, beyond the range of what is considered functional hearing. CNC Word Test in Quiet The mean CNC word scores can be found in Figure 2. The average percent correct scores were 4.8% (SD 5 9.0%) at the preoperative interval, 38.8% (SD %) at the 3-month postactivation interval, and 42.3% (SD %) at the 6-month postactivation interval. Following arcsine transformation, the data were analyzed using a repeated measures analysis of variance (RM-ANOVA) using the CNC word score in RAU as the dependent variable, and test interval (preoperative, 3 months, and 6 months postactivation) as a within-subjects variable. Age at implantation was used as a covariate. Results showed a significant main effect (effect of the independent variable on the dependent variable) for test interval (F [2, 24] 5 8.7; P 5.001). The main effect of the test interval was followed up with post hoc pairwise comparisons using Bonferroni corrections. Results showed significant improvement in CNC word recognition in the unilateral condition between the preoperative and 3-month Fig. 2. Group average and standard deviation scores for CNC word and AzBio Sentence tests at the preoperative, 3-month, and 6-month postactivation test intervals. AzBio 5 Arizona Biomedical Institute; CNC 5 consonant-nucleus-consonant. 1685

4 TABLE III. Scores for Each Domain of the SF-36 Questionnaire for all Participants. Domain Preoperative 6-Month Postactivation Difference P Value Fig. 3. Group average speech reception thresholds in noise and standard deviations measured in an R-SPACE eight-speaker array with the implant on versus implant off. CI 5 cochlear implant; SNR 5 signal-to-noise ratio. postactivation intervals (P <.001). Although testing continued to show increasing benefit between 3 and 6 months postactivation, this difference did not achieve statistical significance (P 5.87). Age at implantation was not found to be a significant covariate (F[1,13] ; P 5.36). AzBio Sentences in Quiet Group average AzBio sentence scores were 8.8% (SD ), 60.1% (SD ), and 61.1% (SD ) at the preoperative, 3-, and 6-month postactivation test intervals, respectively (Fig. 2). The data were subjected to RM-ANOVA, with test interval as the within subjects factor and age at implantation as a covariate. Results showed a main effect for test interval (F[2, 24] 5 7.2; P <.003). Follow-up pairwise comparisons with Bonferroni corrections showed significant increase in performance between the preoperative and 3-month postactivation test interval (P <.001), but not between the 3- and 6-month postactivation intervals (P 5 1.0). Age at implantation was not found to be a significant covariate (F[1,13] 5 1.5; P 5.25). HINT Sentences in Diffuse Noise The average SRT in diffuse noise at the 6-month test interval was db SNR (SD 5 1.8) when tested with the CI on, and 1.5 db SNR (SD 5 2.2) when tested Physical functioning Role functioning/ physical Role functioning/ emotional Energy/fatigue Emotional well-being Social functioning Pain General health SF-36 5 Medical Outcomes Study Questionnaire Short Form 36. with the CI off (Fig. 3). The data were analyzed using a RM-ANOVA with the SRT in db SNR as the dependent variable and condition (CI on, CI off) as the within subjects variable. Results of the analysis showed a main effect for condition (F[1,14] ; P <.001). HRQoL Average total scores for each domain of the NCIQ and SF-36 can be found in Tables II and III, respectively. To investigate the effects of cochlear implantation on HRQoL, paired t tests were performed on the means of each domain of both the NCIQ and SF-36. Significant increases were found on all six domains of the NCIQ. However, there were no changes on any of the eight domains of the SF-36. Results of the SSQ-C at 6-months postactivation can be found in Fig. 4. Results show that this group of participants all rated their hearing as better with the implant, and none of them reported it was worse. Overall, results of the SSQ-C help qualify the other test results such that all participants reported improved hearing on all three domains. Tinnitus Suppression The participants of this study sought cochlear implantation for the sole purpose of hearing restoration, TABLE II. Scores for Six Domains of the NCIQ Questionnaire for all Participants. Domain Preoperative 6-Month Postactivation Difference P Value Basic sound perception Advanced sound perception Speech production Self-esteem Activities Social interactions NCIQ 5 Nijmegen Cochlear Implant Questionnaire. Fig. 4. Group average and standard deviation scores for the three domains of the SSQ-C. SSQ-C 5 Speech Spatial and Qualities of Hearing Comparative. 1686

5 though tinnitus relief was often a by-product of the procedure. Of the 20 participants implanted, 18 reported subjective tinnitus before implant surgery. Of those 18, 16 reported tinnitus relief, one reported no change, and one reported an increase in the severity of the tinnitus. Of the 16 individuals who reported tinnitus relief, 14 reported complete tinnitus relief, and two reported partial relief. DISCUSSION The current study examined performance outcomes of cochlear implantation among adults and children with short-duration UHL. It is worth reviewing that all participants had hearing thresholds better than or equal to 25 db HL through 2,000 Hz, and four participants had mild high-frequency sensorineural hearing loss. From a functional standpoint, these four subjects in essence also had unilateral hearing loss, not using a hearing aid and having better than 90% monosyllabic word understanding in the nonimplanted ear. Overall, cochlear implantation had a significant and positive effect on hearing for the affected side and overall binaural processes. Monosyllabic word recognition in quiet for the implanted ear improved significantly from 4.7% preoperatively to 42% at the 6-month postactivation interval. Though we are unable to make comparisons between adults and children given the small sample size, it is worth noting that one child included in this data scored 75% on the CNC word test on the implanted side, outperforming all other participants. Comparison of the overall group performance on monosyllabic word scores to previous research is limited, because only two other studies have used similar measures. Of those two, only one study reported group scores. 15,16 Friedmann et al. 15 reported on 16 patients with UHL who had an average CNC word score of 55% after 6 months of device use, whereas group average performance on the current study was only 41%. It is possible that methodological differences account for the disparity between the two reports. Specifically, Friedmann and colleagues tested CI performance by plugging and muffing the normal hearing ear in an effort to isolate the CI-only ear. In the current study, postactivation testing was completed using a direct audio input cable that directed the target sentence from a laptop computer to the participant s speech processor. The direct audio input cable allowed for isolation of the implanted side for testing, though there is no method for quantifying or verifying the presentation level. Friedmann and colleagues may not have provided sufficient masking of the contralateral ear by plugging and muffing when attempting to evaluate performance with the CI only. As a result, the test scores may be artificially inflated because the target speech was partially audible to the normal hearing ear. An interesting comparison is between speech recognition of participants in the current study to previous studies using CI recipients with bilateral hearing loss (BHL). For example, Holden et al. studied speech perception outcomes among a group of 114 adults who met the current US Food and Drug Administration (FDA) guidelines for cochlear implantation, and found an average CNC word score of 61% at 6 months postactivation. 29 Similarly, Sladen and Zappler examined patients with bilateral moderate-to-severe hearing loss who were unilaterally implanted. 30 In that study, the average CNC word score after 6 months of implant use was 58%, with no significant improvement in performance thereafter. There are several possible reasons for the disparity in word recognition scores reported in the current group of patients with UHL compared to previous reports of patients with BHL. The most likely explanation is that individuals with UHL have a normal hearing ear to rely on. In contrast, individuals with BHL have limited, if any, auditory cues for speech recognition other than the signal from the implant. One could speculate that individuals with BHL are simply better at making use of the cues available to them, because that is all they have. Another possibility is that comparable speech recognition takes longer to achieve for those with UHL compared to BHL. It is possible that this group will continue to improve at 12 months postactivation and beyond, unlike those with BHL who do not improve significantly after 6 months of device use. One aim of this study was to examine whether a cochlear implant restored sufficient hearing for binaural hearing, which is important for understanding speech in noise. The current study showed that speech perception performance in noise was significantly improved with the addition of the CI as compared to the unilateral hearing condition, suggesting that binaural processing is, at least in part, restored by the implant. The underlying reason for improvement is unknown, though the arrangement of speech and noise (speech at 08 and noise from all around) in this study suggests that speech in noise improvement came from true binaural hearing and not simply head shadow effect. It is possible that the improvement for speech in noise with the implant on was due to difference in timing and intensity cues to each ear (binaural squelch). However, because the speech signal was coming from the front and arriving at the two sides at the same time, it is also possible the benefit came from binaural summation. The benefits observed for speech in noise in the current study are in contrast to the results of Arndt et al. and Vermeire et al., who each reported no significant benefit with the addition of the CI when testing in noise after 6 months of device use. 14,19 Both studies used conditions for the speech in noise testing that included speech at 08, with noise presented at 08 (S 0 N 0 ), 908 (S 0 N 90 ), and 2708 (S 0 N 270 ). They found superior speech in noise recognition for all implant conditions except N 0 S 0, suggesting that the head shadow accounts for the observed improvement. In addition, Vermeire et al. reported that the masker was a speech-shaped noise presented at 65 db; Arndt and colleagues did not report the noise type. 14,19 The methods of the current study were markedly different such that restaurant noise was presented from an eight-speaker array arranged in a 3608 pattern at 72 db SPL. It is possible that the participants in this study were able to take advantage of the diffuse nature of the 1687

6 noise because it is a more real-world experience. As opposed to speech-shaped noise, the masker used in this study has intermittent dips in the noise, allowing participants to hear the target sentence more clearly. The long-term benefit for speech in noise is yet to be explored, and it is possible that the amount of benefit will continue to improve. The HRQoL outcomes showed significant improvement using the disease specific NCIQ. This finding clearly demonstrates that a CI does improve hearing loss related QoL for recipients with significant UHL. Group scores on the generic SF-36 did not change between the preoperative and 6-month postactivation intervals. In addition, the results from the SF-36 were in close alignment with the published normative values for the general population on this measure. 24 The results of the SF- 36 HRQoL scale are particularly important findings because they demonstrate that going outside the current FDA guidelines does not cause any harm to the overall health for this population. Previous reports have also found significant HRQoL benefits using disease-specific measures, though to the best of our knowledge, this is the first report of HRQoL using a generic scale. 14,19 The SSQ-C also clearly demonstrated a self-perceived benefit of cochlear implant use in everyday life. Together, the SSQ-C and NCIQ help illustrate the advantage of a CI for individuals with UHL in facets of their daily lives that have nothing to do with speech perception. There are several limitations that warrant discussion. First, these participants all had less than 2 years of UHL prior to implantation. The duration of hearing loss is known to be an important prognostic tool, and similar findings have been reported for individuals with UHL, though in a very small sample size. 31 It is possible that the current findings are not representative of a population with a longer duration of deafness. Another limitation is that the current cohort was comprised of predominantly younger adults who experienced sudden hearing loss and were not satisfied with existing treatment options. Specifically, the individuals sought out a treatment option that has not been traditionally available. As such, there may be a considerable selection bias toward enrollment of more motivated or committed subjects. Third, the data reported herein are preliminary data from the first 15 participants of the study who have 6 months of device use. Although the results of this investigation are promising, further study with a larger cohort over a longer period of time is warranted. CONCLUSION The results of the current study demonstrate the unequivocal benefits of cochlear implantation in both children and adults with UHL, using a strict definition of normal hearing in the contralateral ear. Moreover, these data show that the advantages of restoring binaural hearing reach beyond speech recognition in quiet into speech recognition in noise and HRQoL. Future clinical trials are warranted to establish firm candidacy criteria for patients with unilateral hearing loss. BIBLIOGRAPHY 1. Fetterman BL, Saunders JE, Luxford WM. Prognosis and treatment of sudden sensorineural hearing loss. Am J Otol 1996;17: Hughes GB, Freedman MA, Haberkamp TJ, Guay ME. Sudden sensorineural hearing loss. Otolaryngol Clin North Am 1996;29: Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg 2012;146:S1 S Blauert J. Spatial Hearing. Cambridge, MA: MIT Press; Wie OB, Pripp AH, Tvete O. 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