Cochlear Implantation for Single-Sided Deafness: A Multicenter Study

Transcription

1 The Laryngoscope VC 2016 The American Laryngological, Rhinological and Otological Society, Inc. Cochlear Implantation for Single-Sided Deafness: A Multicenter Study Douglas P. Sladen, PhD; Christopher D. Frisch, MD; Matthew L. Carlson, MD; Colin L.W. Driscoll, MD; Jennifer H. Torres, MA, CCC-A2; Daniel M. Zeitler, MD Objectives/Hypothesis: To report the preliminary outcomes of patients with single-sided deafness and asymmetric hearing loss undergoing cochlear implantation at two centers. Study Design: Retrospective review and prospective data collection. Methods: Patients with single-sided deafness who underwent cochlear implantation at two centers were included. Preand postoperative measures included monosyllabic word and sentence recognition in quiet for the ear implanted, and sentence recognition in noise in the best-aided bilateral condition. Results: Average monosyllabic word recognition scores in quiet improved significantly from 11.3% (standard deviation [SD] 15.6%) preoperatively to 48.7% (SD 24.2%) at the 3-month postactivation interval, although they did not increase significantly between the 3-month and 6-month intervals. Sentence recognition scores in quiet increased significantly from 18.4% (SD 28.5%) preoperatively to 65.9% (SD 17.9%) at the 3-month postactivation interval, but not between the 3-month and 6- month intervals. Sentence recognition in noise in the best-aided bilateral condition increased from 59% (SD 16.3%) preoperatively to 72% (SD 16.0%) at 6-months postactivation, though the difference was not statistically significant. Thirteen of the participants reported tinnitus prior to surgery. Of those, 12 reported that tinnitus was improved after implantation, and one reported that tinnitus was unchanged. Conclusion: Preliminary results suggest that speech recognition in a singly deafened ear is significantly improved after cochlear implantation, although speech recognition in noise measured in the bilateral condition remains the same at 6- months postactivation. Key Words: Cochlear implant, single-sided deafness, signal-to-noise ratio, tinnitus, speech understanding in noise, sudden sensorineural hearing loss. Level of Evidence: 4. Laryngoscope, 127: , 2017 INTRODUCTION Single-sided deafness (SSD) is characterized by unilateral hearing loss in the presence of normal or nearnormal hearing in the opposite ear. Previous research demonstrates that SSD affects some 18.1 million people in the United States and significantly impacts quality of life, resulting in increased stress and a feeling of exclusion in social settings. 1 3 Those affected by SSD have decreased hearing sensitivity, degraded speech recognition, and usually some degree of tinnitus. In fact, more From the Department of Otolaryngology Head and Neck Surgery, Mayo Clinic (D.P.S., C.D.F., M.L.C., C.L.W.D.), Rochester, Minnesota; the Denver Ear Associates (J.H.T.), Denver, Colorado; and the Department of Otolaryngology Head and Neck Surgery, Virginia Mason Medical Center (D.M.Z.), Seattle, Washington, U.S.A. Editor s Note: This Manuscript was accepted for publication April 26, Presented in part as a poster at The American Academy of Otolaryngology Head and Neck Surgery Annual Meeting, Orlando, Florida, U.S.A., September 21 24, C.L.W.D. is a consultant for Advanced Bionics Corporation, Cochlear Corporation, and MED-EL GmbH. D.M.Z. is a consultant for Med-El Corporation and Cochlear Corporation. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Daniel M. Zeitler, MD, FACS, Virginia Mason Medical Center, 1100 Ninth Avenue, Mailstop X10-ON, Seattle, WA Daniel.zeitler@virginiamason.org DOI: /lary than 90% of adults who experience unilateral sudden sensorineural hearing loss (SSNHL) also report ringing in their ears. 4 Perhaps most disturbing among patients with SSD is the loss of binaural function affecting sound localization and speech understanding in complex listening environments. Binaural hearing is the result of 1) binaural squelch: the ability of the brain to separate speech from noise, 2) binaural summation: redundancy of auditory input, and 3) the head shadow effect: the decrease in loudness as sound moves from one side of the head to the other. 5,6 Current treatment options for SSD consist of routing the signal from the impaired ear to the normal hearing contralateral side using contralateral routing of signal (CROS) aids/bicros aids or an auditory osseointegrated implant system. Previous research has demonstrated that both are effective to overcome head shadow effect and detect sounds from the affected side, although they do not restore binaural hearing because the brain only receives input from one side. 7 9 In fact, research in this area demonstrates that rerouting the signal to the normal hearing side provides little improvement in sound localization and modest improvement for understanding speech in noisy conditions. 7 9 Cochlear implants (CI) have been suggested as an alternative treatment option for individuals with SSD. 223

2 Fig. 1. Preoperative air conduction hearing thresholds for the implanted ear. The emerging research is positive and suggests that CIs offer partial hearing restoration for the implanted ear, although outcomes related to binaural hearing are mixed. Speech recognition in the ear implanted, when measured in quiet, has been shown to improve significantly following implantation. 10,11 Speech recognition in noise, however, is highly variable and test parameters vary considerably among investigators, making direct comparison difficult. For example, Vermiere, Tavora- Viera, and Stelzig each presented speech and noise from a front center speaker (S0N0) and used an adaptive procedure to find the signal-to-noise ratio (SNR) needed for 50% correct, although speech materials varied among them. 10,12,13 Vermiere et al. found a statistically significant decrease in the SNR needed for sentence understanding, and the other two did not. 10 Later, a metaanalysis pooling all three studies demonstrated a mean decrease in SNR necessary for 50% correct. 14 In other research, Stelzig et al. and Arndt et al. each presented speech and noise at 65-dB sound pressure level (SPL) from S0N0 and found no difference in sentence recognition following cochlear implantation. 13,15 Zeitler et al. showed subjects undergoing CI for SSD demonstrated significant improvement in sentence scores in complex noise environments in the binaural condition, with the greatest improvements when speech is presented to the implanted ear. These same subjects also showed significant improvements in sound source localization, with some subjects localizing sound at or near the accuracy of normal hearing listeners. 16 Other studies have also reported significant improvement for localization among patients with SSD, decreased tinnitus, and improved self-perceived benefit on the Speech Spatial and Qualities of Hearing questionnaire. 17 Reports of tinnitus suppression after implantation have been reported by several investigators. 15,18 In one study, Arts et al. examined the impact of implantation on tinnitus among patients with SSD by pooling data from several reports. 18 The data were treated as a multicenter study and subjected to matched t tests. Results demonstrated improved tinnitus between preoperative and 1-, 3-, 6-, and 24- month postoperative test intervals. 224 The purpose of this study was to complete a preliminary evaluation of speech recognition in quiet and in noise among a group of adults and children with SSD. Data was compiled from two separate centers. MATERIALS AND METHODS The current study was a multisite, single-arm repeated measures research design. Each participating center obtained institutional review board approval from their respective center. Participants The participants in this study had mild to severe sensorineural hearing loss with 40% consonant-nucleus-consonant (CNC) word recognition on the affected side. A pure tone average of 30 db HL or better and a mean word recognition score of 99.3% (standard deviation [SD] 2.8%) were present on the contralateral side. Thus, all patients had truly normal hearing in the nonimplanted ear. The preoperative air conduction hearing thresholds for the ear implanted can be found in Figure 1. The total sample was comprised of 23 individuals (17 adults, 6 children). The adults ranged in age from 31 to 62 years, and the children ranged in age from 5 to 15 years. Duration of hearing loss was defined as the time between onset of hearing loss and time of implantation. Duration of hearing loss ranged from 0.5 to 9.5 years with an average of 4.0 years. In all, there were 10 left ears and 13 right ears implanted. Demographic information for all participants can be found in Table I. Materials Speech understanding was assessed using the CNC word test and the AzBio sentence test. 19,20 The CNC word test is comprised of 10 lists, each containing 50 monosyllabic words produced by a single male talker. The AzBio Sentence Test is comprised of 15 lists of 20 sentences, each produced by two male and two female talkers and scored for each word repeated correctly. Procedures Prior to preoperative aided testing, participants hearing aids were set to National Acoustic Laboratories (prescriptive targets). 21 Participants who did not use hearing aids on a fulltime basis were required to complete a 30-day trial before CI candidacy determination.

3 TABLE I. Participant Demographics. Participant Age at Implantation (yrs) Etiology of Deafness Duration of Deafness (yrs) AOI Conversion Device Congenital 5.8 Med-El Synchrony Flex SSNHL 1.5 Med-El Concert Flex SSNHL 6.0 Med-El Concert Flex Congenital 8.9 Med-El Concert Flex Congenital Med-El Concert Flex Progressive Med-El Concert Standard SSNHL 2.5 Med-El Concert Flex MD 3.0 AB HiFocus Mid-Scala Iatrogenic p NSGY 0.5 Med-El Concert Flex SSNHL 1.5 Med-El Concert Flex SSNHL 1.0 Med-El Concert Flex SSNHL 11.0 Med-El Concert Flex SSNHL 1.0 Med-El Concert Flex Ear Sx 2.0 Cochlear Nucleus Acoustic neuroma 0.9 Med-El Concert Flex Meningitis 0.8 Cochlear Nucleus SSNHL 1.9 Cochlear Nucleus SSNHL 1.0 Med-El Concert Flex SSNHL 1.0 Med-El Concert Flex Ear Sx Cochlear CI24 RE(CA) SSNHL 2.0 AB HiFocus Mid-Scala Labyrinthitis 5.0 Cochlear Nucleus SSNHL 2.0 Cochlear Nucleus 422 SSNHL 5 sudden sensorineural hearing loss; MD 5 Meniere s Disease; Sx 5 surgery; p NSGY 5 after neurosurgical procedure; AOI 5 auditory osseointegrated implant; AB 5 Advanced Bionics Cochlear Corporation (NSW, Australia), Advanced Bionics (Valencia, CA, USA), Med-El (Innsbruck, Austria). Testing was completed in quiet in a sound field using recorded stimuli at a calibrated presentation level of 60 db SPL (Aweighted [SPL(A)]). The contralateral ear was either masked (center 1) or plugged and muffed (center 2). Speech in noise was measured with the impaired ear-aided and the contralateral ear unoccluded in a 15 db SNR with speech at 65 db SPL(A). Speech and noise both originated from a single speaker at 0-degree azimuth. Postoperatively, speech understanding in quiet was measured using a direct audio input (DAI) cable (center 1), or as described above with the contralateral ear plugged and muffed (center 2). Patients tested using DAI were asked to set the volume at a comfortable loudness level prior to starting the test. Speech understanding in noise was tested in the aided bilateral condition with the CI in place. All testing was completed using an omnidirectional program with user settings. Each participant was administered one list per condition at each time interval. Responses were recorded and scored by the experimenter. All speech perception scores were calculated as percent correct. Due to the combination of retrospective and prospective data, not all participants completed testing at each time interval. Statistical analyses were completed using IBM SPSS Statistical Package (IBM Corp., Armonk, NY). An alpha level of 0.05 was used to determine statistical significance. and 6-month postactivation intervals. Individual patient scores for each time interval can be found in Figure 2. Pediatric patients are represented with open symbols. Mean CNC word scores were 11.3% (SD 15.6%) preoperatively, 48.7% (SD 24.2%) at the 3-month postactivation interval, and 44.7% (SD 20.0%) at 6-month postactivation interval. The data were analyzed using a repeated measures analysis of variance (RM-ANOVA) using CNC word score in percent correct as the dependent variable, and test interval (preoperative, 3-month, and 6-month RESULTS Consonant-Nucleus-Consonant Word Understanding in Quiet Performance on CNC word test was completed on 20 participants preoperatively and 13 participants at 3- Fig. 2. Individual patient scores for CNC words in quiet for the preoperative, 3-month, and 6-month postactivation test intervals. Pediatric patients are represented with open symbols. CNC 5 consonant-nucleus-consonant. 225

4 individual patient scores for the preoperative and 6- month postactivation test intervals can be found in Figure 4. Pediatric patients are represented with open symbols; mean percent correct scores were 59% (SD 16.3%) preoperatively and 72% (SD 16.0%) at 6- months postactivation. Scores were analyzed using a Student t test and showed no significant difference between the preoperative and 6-month test interval t(8) , P Fig. 3. Individual patient scores for AzBio sentences in quiet for the preoperative, 3-month, and 6-month postactivation test intervals. Pediatric patients are represented with open symbols. Tinnitus Suppression The subjective presence of tinnitus was recorded pre- and postoperatively. Among the 23 participants, 13 described having tinnitus before surgery. Of them, 12 (92%) participants reported that their tinnitus was improved after surgery. One person reported no change in tinnitus after surgery. postactivation) as a within-subjects variable. Results showed a significant main effect of test interval, F (2, 20) , P < The main effect of test interval was followed up with post-hoc pairwise comparisons using Bonferonni corrections, which showed significant improvement in CNC word recognition for the ear implanted between the preoperative and 3-month postactivation intervals, P , but not between the 3- month and 6-month postactivation intervals, P AzBio Sentence Understanding in Quiet Average AzBio sentence recognition scores in quiet were present for 18 participants preoperatively, 11 participants at 3-months postactivation, and nine participants at 6-months postactivation. Individual patient scores at the three test intervals can be found in Figure 3. Pediatric patients are represented with open symbols. Mean AzBio sentence scores were 18.4% (SD 28.5%) preoperatively, 65.9% (SD 17.9%) at the 3-month postactivation interval, and 66.0% (SD 18.2%) at the 6-month postactivation interval. The data were analyzed using RM-ANOVA with test interval and listening condition as within-subject factors. The results demonstrated a significant main effect of test interval F(2,12) , P < The main effect of test interval was followed up with pairwise comparisons with Bonferonni corrections, which showed significant improvement for the unilateral condition between preoperative and 3-month postactivation intervals, P <.001, but not between the 3-month and 6-month postactivation test intervals, P DISCUSSION Single-sided deafness impairs auditory function of one ear and leads to deficits for speech in noise understanding and localization. Current treatment options have been limited to devices that route the signal from the affected side to the side with normal hearing but do not restore binaural hearing. Cochlear implantation has been offered as an alternative treatment option and one that can restore true binaural hearing. The emerging literature is encouraging, although comprised of reports with small sample sizes, variable follow-up, heterogeneous populations, differing test parameters, and variable outcomes. The purpose of this study was to evaluate speech recognition performance in a group of adults and children with SSD through a multicenter design. Results of the current study clearly demonstrate that CI can provide partial hearing restoration and can significantly improve both word and sentence scores in the ear implanted when measured in quiet. This finding is in agreement with previous reports. 10,11,22 The degree of improvement, however, is less than the improvement AzBio Sentence Understanding in 15 db Signalto-Noise Ratio Average AzBio sentence recognition scores in 15 db SNR quiet were present for 10 individuals preoperatively, two individuals at 3-months postactivation, and eight people at 6-months postactivation. Due to the exceptionally low number of scores at 3-months postactivation, statistical analysis was completed using only the preoperative and 6-month postactivation scores. The 226 Fig. 4. Individual patient scores for AzBio sentences in 15 db signal-to-noise ratio at the preoperative and 6-month postactivation test intervals. Pediatric patients are represented with open symbols.

5 observed in adults and children with bilateral hearing loss. Specifically, the current study found that CNC word recognition was, on average, 44% at 6-months postactivation, whereas studies using adults with bilateral hearing loss, also with 6 months of use, have an average CNC word score of 61%. 23 The primary explanation for this finding is that patients with normal hearing in one ear continue to rely heavily on their good ear because of the natural sound quality, which may reduce the rate of improvement and maximum rehabilitation potential of the deaf ear. In contrast to speech recognition in quiet, the current study found that speech recognition in noise was not significantly improved after CI, although the scores at 6-months postactivation were higher than those obtained before surgery. As noted earlier, several previous investigators have reported similar findings. However, one recent study by Mertens et al. suggests that speech-in-noise improvement may not emerge until after several years of implant use. 24 In that study, 12 adults with SSD and CI were followed through 36 months of implant use. Speech-in-noise performance was measured with CI on and CI off using various testing parameters, including presentation of both speech and noise from the front, as well as spatially separated signals (S 0 N 0, S 0 N CI,S CI N 0 ). Results demonstrated improved speech in noise for S 0 N CI after 12 months of implant use, whereas improved performance for S 0 N 0 was not observed until 36 months of implant use. Tinnitus suppression continues to be an indirect benefit of implantation among patients with SSD. As seen in the current study, the majority of patients who had tinnitus prior to surgery had a reduction in selfreported tinnitus severity following implantation with the device on, and in many cases also with the device off. The exact underlying reason of tinnitus suppression is not known, although there is speculation that the implant increases afferent stimulation, which offsets one possible underlying cause. 18 There are several limitations associated with the current study. First, the relatively small sample size makes statistical comparisons less robust and limits generalizability of the data. Larger sample sizes are needed to understand the variability in performance within this population. Another limitation is that data was collected retrospectively from two separate centers, each with unique test protocols. For example, center 2 measured speech recognition in the implanted ear with the contralateral ear plugged and muffed, whereas center 1 used masking on the contralateral side. It is unknown if these two methods are equivalent. Another limitation of this study is the condition of the participants sound processors. Each participant was tested using the sound processor and program that they use in everyday life. There was no control regarding the volume setting, the presence of noise suppression circuits, or input mixing ratios. It is possible that some participants have much higher volume settings than others. Demographic factors also limit the current study. For example, the group studied here was comprised of children and adults with various etiologies and durations of deafness. Although the majority (12 of 23 or 52%) had SSNHL, other causes of hearing loss were also represented. The numbers, however, are not large enough to analyze outcomes by etiology. In addition, longer durations of deafness were observed in many of these cases. We know from previous work that duration of deafness negatively impacts CI performance and may have played a role in our patients being implanted after longer periods of nonusable hearing. 23 Our mean duration of deafness (4.0 years) is skewed by three of six of the children in whom congenital hearing loss and long delays to implantation occurred. Future studies with higher numbers of patients in this category will be needed to determine if significant differences in performance occur. CONCLUSION Rehabilitation of SSD with CI significantly improves speech understanding in the deafened ear and reduces or eliminates tinnitus in most subjects. Speech understanding in noise remains unchanged between the 3-months and 6-months postactivation test intervals. It is possible that performance on speech in noise will continue to improve that and benefits will be realized with longer-term implant experience. BIBLIOGRAPHY 1. Hanson H. 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