Cochlear Implantation For Single-sided Deafness Research Articles

Binaural Perception in Single-Sided Deaf Cochlear Implant Users with Unrestricted or Restricted Acoustic Hearing in the Non-Implanted Ear

Cochlear implantation (CI) can benefit patients with single-sided deafness (SSD) in terms of sound localization, speech understanding in noise, tinnitus severity, and quality of life (QoL). In previous studies, CI outcomes have been largely reported for SSD patients with normal “unrestricted” hearing in the contralateral ear. However, SSD patients may often have some degree of hearing loss in the contralateral ear (“restricted” acoustic hearing). In this study, we report results from a French clinical trial for CI in in SSD patients (NCT02204618). Localization, speech reception thresholds (SRTs) in noise, tinnitus severity, and QoL were evaluated in 18 SSD patients 1 year after CI. Data were analyzed for 2 subject groups according to the pure-tone average thresholds in the non-implanted ear: unrestricted acoustic hearing (UNRES; ≤25 dB HL; n = 10) and restricted acoustic hearing (RES; > 25 dB HL; n = 8). Across all subjects, localization was significantly better with the CI on than off (p = 0.005); there was no significant difference between subject groups (p = 0.301). When speech and noise were co-located (S0N0), there was no significant difference in SRTs with the CI on or off (p = 0.480); SRTs were significantly better for the UNRES than for the RES group (p = 0.005). When speech and noise were spatially separated (S_CIN_NH), SRTs were significantly better with the CI on than off (p < 0.001). While SRTs were better for the UNRES than for the RES group (p = 0.024), the CI benefit was more than 50% greater for the RES group due to the restoration of high-frequency speech cues. Questionnaire data showed that tinnitus severity was significantly reduced (p = 0.045) and QoL was significantly improved after one year of experience with the CI (p < 0.001). Age at testing was significantly correlated with SRTs for the S0N0 condition; duration of deafness was correlated with SRTs for the S_CIN_NH condition. There were relatively few correlations between behavioral and subjective measures, suggesting that both were valuable when assessing CI benefits for SSD patients. The present data suggest that indications for CI should be expanded to include unilaterally deaf patients who have normal hearing or mild-to-moderate hearing loss in the non-implanted ear.

Single Sided Deaf Cochlear Implant Users in the Difficult Listening Situation: Speech Perception and Subjective Benefit.

Patients with single-sided deafness (SSD) have great difficulties in listening situations which rely on binaural auditory processing. The purpose of this study was to examine to which extent a cochlear implant (CI) can improve speech perception outcomes in various noisy listening environments. Additionally, the ability to use interaural level differences for sound localization and subjective benefit with the CI were assessed. Ten single-sided deaf patients with CI were tested in different loudspeaker configurations with and without the CI. A multi-source noise field (MSNF) with uncorrelated noise from four different directions was used in addition to a setup with the signal from the CI side and noise from the normal-hearing side (SCINNH, azimuth of ±45 degrees). Ten normal-hearing subjects were used as a control for the setup. Speech understanding was measured by an adaptive sentence test (Oldenburg Sentence Test, OLSA) in stationary speech shaped noise and temporally modulated noise to assess the benefit in each listening situation. Sensitivity to interaural level differences was measured in a lateralization experiment. Furthermore, patients completed the Bern Benefit in Single-Sided Deafness (BBSS) questionnaire to assess subjective benefit with the CI. An overall average benefit in speech reception threshold (SRT) of 1.6 dB (±0.6 dB standard error of the mean [SEM]) was observed in the binaural listening condition (with CI) in all conditions. In the MSNF setup thresholds improved by 0.4 dB (±0.5 dB SEM) and in the SCINNH configuration by 2.7 dB (±0.7 dB SEM). The choice of masking noise effect also had a significant effect on the SRT outcome. The lateralization performance of the SSD users was on a par with the normal hearing group. BBSS scores reflect the overall benefit with the CI apparent in the speech test results. Patients with single-sided deafness do benefit from a CI in difficult listening environments and are able to localize sound based on interaural level differences. Considering these outcomes, cochlear implantation represents a promising treatment option for patients with single-sided deafness.

Interaural Time Difference Perception with a Cochlear Implant and a Normal Ear.

Currently there is a growing population of cochlear-implant (CI) users with (near) normal hearing in the non-implanted ear. This configuration is often called SSD (single-sided deafness) CI. The goal of the CI is often to improve spatial perception, so the question raises to what extent SSD CI listeners are sensitive to interaural time differences (ITDs). In a controlled lab setup, sensitivity to ITDs was investigated in 11 SSD CI listeners. The stimuli were 100-pps pulse trains on the CI side and band-limited click trains on the acoustic side. After determining level balance and the delay needed to achieve synchronous stimulation of the two ears, the just noticeable difference in ITD was measured using an adaptive procedure. Seven out of 11 listeners were sensitive to ITDs, with a median just noticeable difference of 438μs. Out of the four listeners who were not sensitive to ITD, one listener reported binaural fusion, and three listeners reported no binaural fusion. To enable ITD sensitivity, a frequency-dependent delay of the electrical stimulus was required to synchronize the electric and acoustic signals at the level of the auditory nerve. Using subjective fusion measures and refined by ITD sensitivity, it was possible to match a CI electrode to an acoustic frequency range. This shows the feasibility of these measures for the allocation of acoustic frequency ranges to electrodes when fitting a CI to a subject with (near) normal hearing in the contralateral ear.

Cortical reorganization after cochlear implantation for adults with single-sided deafness.

BackgroundAdults with single sided deafness (SSD) have lost binaural function, which limits sound source localization, speech understanding in noise, and quality of life. For SSD patients, restoration of bilateral auditory input is possible only with a cochlear implant (CI). In this study, cortical auditory evoked potentials (CAEPs) and behavioral performance were measured in left-implanted (SSD-CI-L) and right-implanted (SSD-CI-R) patients before and after cochlear implantation. We hypothesized that improvements in behavioral performance would be accompanied by changes in CAEPs after cochlear implantation.DesignProspective longitudinal study.SettingTertiary referral center.MethodNine right-handed adult SSD CI patients participated in the study. CAEPs were recorded before cochlear implantation and at 6 and 12 months post-implantation. CAEPs were elicited using speech stimuli (/ba/) delivered in sound field at 70 dBA. Global field power (GFP) latency and amplitude were calculated for P1, N1 and P2 peaks at each test session. CAEP were analyzed at frontocentral (Cz) and temporal (P7, P8, T7 and T8) and mastoid electrodes (M1 and M2) contralateral to the CI ear. Behavioral measures (sentence recognition in noise, with and without spatial cues) were collected at the same test sessions as for CAEPs. Speech performance and CAEPs were also measured in a control group of normal-hearing (NH) subjects.ResultsWhile increased N1 amplitude was observed in the scalp potential maps for GFP and Cz for SSD-CI-L patients after implantation, the changes were not statistically significant. Peak CAEP amplitude at electrodes to contralateral to the CI ear increased after cochlear implantation for all SSD-CI patients, but significant increases were observed only for mastoid sites. Peak latencies for some components at temporal and mastoid sites remained significantly longer than for the NH control group, even after cochlear implantation. For SSD-CI-R patients, P2 peak amplitude for baseline GFP and Cz was significantly lower than for the NH control group. A significant improvement for speech understanding in noise was observed at 12 months post-implantation when speech was presented to the CI ear and noise to the non-implanted ear.ConclusionAfter cochlear implantation, speech understanding significantly improved when speech and noise were spatially separated. The increased N1 amplitude for SSD-CI-L patients and the increased bilateral activation for all SSD-CI patients may reflect cortical reorganization and restoration of binaural function after one year of experience with the CI. However, because of the limited number of SSD patients, significant changes in cortical activity after cochlear implantation were often difficult to observe.

Modeling Speech Intelligibility of Simulated Bimodal and Single-Sided Deaf Cochlear Implant Users

Modeling Speech Intelligibility of Simulated Bimodal and Single-Sided Deaf Cochlear Implant Users

Effects of Training on Lateralization for Simulations of Cochlear Implants and Single-Sided Deafness.

While cochlear implantation has benefitted many patients with single-sided deafness (SSD), there is great variability in cochlear implant (CI) outcomes and binaural performance remains poorer than that of normal-hearing (NH) listeners. Differences in sound quality across ears—temporal fine structure (TFS) information with acoustic hearing vs. coarse spectro-temporal envelope information with electric hearing—may limit integration of acoustic and electric patterns. Binaural performance may also be limited by inter-aural mismatch between the acoustic input frequency and the place of stimulation in the cochlea. SSD CI patients must learn to accommodate these differences between acoustic and electric stimulation to maximize binaural performance. It is possible that training may increase and/or accelerate accommodation and further improve binaural performance. In this study, we evaluated lateralization training in NH subjects listening to broad simulations of SSD CI signal processing. A 16-channel vocoder was used to simulate the coarse spectro-temporal cues available with electric hearing; the degree of inter-aural mismatch was varied by adjusting the simulated insertion depth (SID) to be 25 mm (SID25), 22 mm (SID22) and 19 mm (SID19) from the base of the cochlea. Lateralization was measured using headphones and head-related transfer functions (HRTFs). Baseline lateralization was measured for unprocessed speech (UN) delivered to the left ear to simulate SSD and for binaural performance with the acoustic ear combined with the 16-channel vocoders (UN+SID25, UN+SID22 and UN+SID19). After completing baseline measurements, subjects completed six lateralization training exercises with the UN+SID22 condition, after which performance was re-measured for all baseline conditions. Post-training performance was significantly better than baseline for all conditions (p < 0.05 in all cases), with no significant difference in training benefits among conditions. Given that there was no significant difference between the SSD and the SSD CI conditions before or after training, the results suggest that NH listeners were unable to integrate TFS and coarse spectro-temporal cues across ears for lateralization, and that inter-aural mismatch played a secondary role at best. While lateralization training may benefit SSD CI patients, the training may largely improve spectral analysis with the acoustic ear alone, rather than improve integration of acoustic and electric hearing.

Contralateral suppression of human hearing sensitivity in single-sided deaf cochlear implant users

Cochlear implants (CIs) are being implanted in people with unilateral hearing loss because they can improve speech intelligibility and sound source localization. Though designed to restore the afferent auditory stimulation, the CI possibly restores some efferent effects. The present study aimed at investigating this possibility.Five single-sided deaf CI users with less than 30 dB hearing loss up to 4 kHz in their acoustic ear participated in the study. Absolute thresholds for their acoustic ears were measured for pure tones of 500 and 4000 Hz with durations of 10 and 200 ms in the presence and in the absence of contralateral broadband electrical stimulation (CBES) delivered with the CI. The electrical stimulus consisted of pulse trains (symmetric biphasic pulses with phase duration 36 μs) on all 16 electrodes sequentially stimulated at a rate of 843 Hz. Its intensity was set to sound as loud as broadband noise at 50 or 60 dB SPL in the acoustic ear. Thresholds were measured using a three-interval, three-alternative, forced-choice procedure with a two-down, one-up adaptive rule to estimate the level for 71% correct in the psychometric function.Thresholds measured without the CBES were lower for the longer than for the shorter tones, and the difference was larger at 500 than at 4000 Hz. CBES equivalent to 50 or 60 dB SPL caused significant threshold elevation only for short (10 ms) and low frequency (500 Hz) acoustic tones of 1.2 and 2.2 dB. These increases appear smaller than previously reported for normal hearing listeners in related experiments. These results support the notion that for single-sided deaf CI users, the CI modulates hearing in the acoustic ear. The possible mechanisms that may be contributing this effect are discussed.

Cochlear Implantation for Single-Sided Deafness: Observations in Poor Performers

Abstract Objectives Patients with single-sided deafness can nowadays receive a cochlear implant. A majority of these patients are well adapted and benefit from the implant. The aim of this study was to evaluate the reasons for poor performance in a group of patients with single-sided deafness, who received a cochlear implant. Design A total of 65 patients were enrolled into a retrospective case series. Seven poor performers were present in the group. Freiburger monosyllabics, localization testing, and radiologic images were evaluated. Results Localization testing showed the absence of lateralization ability in three patients, whereas the Freiburger monosyllabic word scores improved in three patients. One patient had no speech perception after 1 year of rehabilitation. Findings of magnetic resonance imaging (MRI) revealed cerebral involvement in five patients. Conclusion Various factors influence the outcome in unilateral cochlear implantation in patients with single-sided deafness. These reasons may be preoperative, operative, or postoperative. Nevertheless, the majority of patients benefit from these implants.

Event-related neuronal responses to acoustic novelty in single-sided deaf cochlear implant users: Initial findings

Objective: A cochlear implant (CI) is an auditory prosthesis restoring profound hearing loss. However, CI-transmitted sounds are degraded compared to normal acoustic hearing. We investigated cortical responses related to CI-degraded against acoustic listening.Methods: Event-related potentials (ERPs) were recorded from eight single-sided deaf CI users who performed a three-stimulus oddball task, separately with their normal hearing ear and CI ear. The oddball tones were occasionally intermitted by novel sounds. ERP responses were compared between electric and acoustic listening for the auditory (N1) and auditory-cognitive (Novelty P3, Target-P3) ERP components.Results: CI-degraded listening was associated with attenuated sensory processing (N1) and with attenuated early cortical responses to acoustic novelty whereas the late cortical responses to acoustic novelty and the target-P3 did not differ between NH and CI ears.Conclusion: The present study replicates the CI-attenuation of Novelty-P3 amplitudes in a within-subject comparison. Further, we show that the CI-attenuation of Novelty-P3 amplitudes extends to early cortical responses to acoustic novelty, but not to late novelty responses.Significance: The dissociation into CI-attenuated P3 early Novelty-P3 amplitudes and CI-unaffected late Novelty-P3 amplitudes represents a cortical fingerprint of CI-degraded listening. It further contributes to general claims of distinct auditory Novelty-P3 sub-components.

Patient benefit from Cochlear implantation in single-sided deafness: a 1-year follow-up.

The objective of the study was to evaluate the quality of life and benefit in patients with single-side deafness before and 1year after cochlear implantation. In a prospective observational study design, ten adult patients with single-sided deafness undergoing cochlear implantation were included. All patients had on the implantation side no speech discrimination with normal hearing aids. The contralateral side was normal or marginal hearing loss. For determining the subject benefit from cochlear implantation, each patient answered standardized questionnaires directly before implantation and 1year after. Regarding the questionnaire Speech, Spatial and Qualities of Hearing (SSQ), the tests yielded a significant difference in the subdomains "speech intelligibility" and "spatial hearing". The Nijmegen Cochlear Implant Questionnaire (NCIQ) showed a significant difference in the subdomain "basic sound perception", but not in the total score. The Glasgow Hearing Aid Benefit Profile (GHABP) showed on average moderate satisfaction in the subdomains "hearing aid benefit" and "residual disability". In general quality of life, no significant difference was found measured by the questionnaire EQ-5D-3L. One year after cochlear implantation, most patients with single-sided deafness showed benefits in hearing as measured by validated questionnaires However, not all patients reported a significant improvement in general quality of life. Therefore, it is important to inform patients adequately and offer alternative treatments before implantation.

Intelligibility in speech maskers with a binaural cochlear implant sound coding strategy inspired by the contralateral medial olivocochlear reflex

We have recently proposed a binaural cochlear implant (CI) sound processing strategy inspired by the contralateral medial olivocochlear reflex (the MOC strategy) and shown that it improves intelligibility in steady-state noise (Lopez-Poveda et al., 2016, Ear Hear 37:e138-e148). The aim here was to evaluate possible speech-reception benefits of the MOC strategy for speech maskers, a more natural type of interferer. Speech reception thresholds (SRTs) were measured in six bilateral and two single-sided deaf CI users with the MOC strategy and with a standard (STD) strategy. SRTs were measured in unilateral and bilateral listening conditions, and for target and masker stimuli located at azimuthal angles of (0°, 0°), (−15°, +15°), and (−90°, +90°). Mean SRTs were 2–5 dB better with the MOC than with the STD strategy for spatially separated target and masker sources. For bilateral CI users, the MOC strategy (1) facilitated the intelligibility of speech in competition with spatially separated speech maskers in both unilateral and bilateral listening conditions; and (2) led to an overall improvement in spatial release from masking in the two listening conditions. Insofar as speech is a more natural type of interferer than steady-state noise, the present results suggest that the MOC strategy holds potential for promising outcomes for CI users.

Cochlear implantation for single-sided deafness and tinnitus suppression

ObjectiveTo quantify the potential effectiveness of cochlear implantation for tinnitus suppression in patients with single-sided deafness using the Tinnitus Handicap Inventory. MethodsThe study included 12 patients with unilateral tinnitus who were undergoing cochlear implantation for single-sided deafness. The Tinnitus Handicap Inventory was administered at the patient's cochlear implant candidacy evaluation appointment prior to implantation and every cochlear implant follow-up appointment, except activation, following implantation. Patient demographics and speech recognition scores were also retrospectively recorded using the electronic medical record. ResultsA significant reduction was found when comparing Tinnitus Handicap Inventory score preoperatively (61.2±27.5) to the Tinnitus Handicap Inventory score after three months of cochlear implant use (24.6±28.2, p=0.004) and the Tinnitus Handicap Inventory score beyond 6months of CI use (13.3±18.9, p=0.008). Further, 45% of patients reported total tinnitus suppression. Mean CNC word recognition score improved from 2.9% (SD 9.4) pre-operatively to 40.8% (SD 31.7) by 6months post-activation, which was significantly improved from pre-operative scores (p=0.008). ConclusionThe present data is in agreement with previously published studies that have shown an improvement in tinnitus following cochlear implantation for the large majority of patients with single-sided deafness.

Expanding Cochlear Implant Criteria: Real World Applications and Outcomes

This article discusses the evolution, current criteria, expanded/expanding indications, and potential future indications for cochlear implants. Some of these areas of expansion include earlier implantation in pediatrics, electroacoustic stimulation for both adults and pediatrics, cochlear implants for single-sided deafness, significant asymmetric hearing loss, and cases of severe debilitating tinnitus associated with hearing loss. Note: Some of the discussion in this article is viewed/regarded as off label from the current Food and Drug Administration (FDA) criteria. The authors' intent for this article is for it to be a helpful overview in the current trends that are changing in cochlear implants. This article is not indented to be a definitive paper about new trends in cochlear implants.

Consequences of Stimulus Type on Higher-Order Processing in Single-Sided Deaf Cochlear Implant Users

Single-sided deaf subjects with a cochlear implant (CI) provide the unique opportunity to compare central auditory processing of the electrical input (CI ear) and the acoustic input (normal-hearing, NH, ear) within the same individual. In these individuals, sensory processing differs between their two ears, while cognitive abilities are the same irrespectively of the sensory input. To better understand perceptual-cognitive factors modulating speech intelligibility with a CI, this electroencephalography study examined the central-auditory processing of words, the cognitive abilities, and the speech intelligibility in 10 postlingually single-sided deaf CI users. We found lower hit rates and prolonged response times for word classification during an oddball task for the CI ear when compared with the NH ear. Also, event-related potentials reflecting sensory (N1) and higher-order processing (N2/N4) were prolonged for word classification (targets versus nontargets) with the CI ear compared with the NH ear. Our results suggest that speech processing via the CI ear and the NH ear differs both at sensory (N1) and cognitive (N2/N4) processing stages, thereby affecting the behavioral performance for speech discrimination. These results provide objective evidence for cognition to be a key factor for speech perception under adverse listening conditions, such as the degraded speech signal provided from the CI.

Current concepts in the management of idiopathic sudden sensorineural hearing loss.

The purpose of this manuscript is to review the initial management strategies for idiopathic sudden sensorineural hearing loss, with an emphasis on the role that steroids play in treatment of this condition, and discuss options for auditory rehabilitation of persistent unilateral hearing loss. Recent data suggest that hearing improvement may be greater for patients initially treated with both systemic and intratympanic steroid when compared with those treated with systemic steroids alone. Salvage intratympanic steroids have been shown to confer hearing benefit if initial management fails. The ideal dosing regimen for intratympanic steroids has not been established, but evidence supports that higher dosing strategies are advantageous. Cochlear implantation has emerged as a strategy for auditory rehabilitation of persistent unilateral hearing loss. Recent studies have demonstrated high patient satisfaction, subjective improvement in tinnitus, and objective performance benefit after cochlear implantation for single-sided deafness. Patients can be offered steroid therapy in the initial management of idiopathic sudden sensorineural hearing loss, but should be counseled that the efficacy of steroids remains unclear. If patients fail to improve with initial management, salvage intratympanic steroid administration should be considered. If hearing loss persists long term, options for auditory rehabilitation should be discussed.

The benefits of cochlear implants for single-sided deafness for sound localization with multiple concurrent sources

Individuals with single-sided deafness (SSD) who receive a cochlear implant (CI) realize some benefit for localization and speech perception in noise. Previous studies of SSD-CIs examined simple conditions involving speech perception in the presence of a single noise masker or single-source localization. However, some of the most important benefits of two ears arise in multisource situations where binaural cues and head turning can facilitate the perceptual separation of spatial separated sources. Eight SSD-CI listeners performed a sound-localization task in a multisource environment pre-implantation and at least 3 months post-implantation. Environmental sounds were presented from a spherical loudspeaker array. The target sound was presented alone, or concurrently with one or three additional sources. The target was cued by being added to or removed from the mixture after a 6-s delay. A head-mounted tracker monitored head movements during the task. The CI substantially improved localization accuracy, reducing the mean azimuthal error by as much as 34%, while reducing the amount of head turning by as much as 44%, even during periods when the target sound was not present. For SSD-CI listeners, bilateral auditory input can improve environmental-sound localization in a complex mixture, while reducing the amount of head-turning effort required. [The opinions and assertions presented are the private views of the authors and are not to be construed as official or as necessarily reflecting the views of the Department of Defense.]

Sound Source Localization by Normal-Hearing Listeners, Hearing-Impaired Listeners and Cochlear Implant Listeners

Objective: Our primary aim was to determine whether listeners in the following patient groups achieve localization accuracy within the 95th percentile of accuracy shown by younger or older normal-hearing (NH) listeners: (1) hearing impaired with bilateral hearing aids, (2) bimodal cochlear implant (CI), (3) bilateral CI, (4) hearing preservation CI, (5) single-sided deaf CI and (6) combined bilateral CI and bilateral hearing preservation. Design: The listeners included 57 young NH listeners, 12 older NH listeners, 17 listeners fit with hearing aids, 8 bimodal CI listeners, 32 bilateral CI listeners, 8 hearing preservation CI listeners, 13 single-sided deaf CI listeners and 3 listeners with bilateral CIs and bilateral hearing preservation. Sound source localization was assessed in a sound-deadened room with 13 loudspeakers arrayed in a 180-degree arc. Results: The root mean square (rms) error for the NH listeners was 6 degrees. The 95th percentile was 11 degrees. Nine of 16 listeners with bilateral hearing aids achieved scores within the 95th percentile of normal. Only 1 of 64 CI patients achieved a score within that range. Bimodal CI listeners scored at a level near chance, as did the listeners with a single CI or a single NH ear. Listeners with (1) bilateral CIs, (2) hearing preservation CIs, (3) single-sided deaf CIs and (4) both bilateral CIs and bilateral hearing preservation, all showed rms error scores within a similar range (mean scores between 20 and 30 degrees of error). Conclusion: Modern CIs do not restore a normal level of sound source localization for CI listeners with access to sound information from two ears.

Interaural stimulation timing in single sided deaf cochlear implant users

The interaural time difference (ITD) is an important cue for the localization of sounds. ITD changes as little as 10 μs can be detected by the human auditory system. By provision of one ear with a cochlear implant (CI) ITD are altered due to the partial replacement of the peripheral auditory system. A hearing aid (HA), in contrast, does not replace but adds a processing delay component to the peripheral auditory system extending ITD. The aim of the present study was to quantify interaural stimulation timing between these different modalities to estimate the need for central auditory temporal compensation in single sided deaf CI users or bimodal CI/HA users. For this purpose, wave V latencies of auditory brainstem responses evoked either acoustically (ABR) or electrically via the CI (EABR) have been measured. The sum of delays consisting of CI signal processing measured in the MED-EL OPUS2 audio processor and EABR wave V latencies evoked on different intracochlear sites allowed an estimation of the entire CI channel-specific delay for MED-EL MAESTRO CI systems. We compared these values with ABR wave V latencies measured in the contralateral normal hearing or HA provided ear in different frequency bands. The results showed that EABR wave V latencies were consistently shorter than those evoked acoustically in the unaided normal hearing ear. Thus, artificial delays within the audio processor can be implemented to adjust interaural stimulation timing. The currently implemented group delays in the MED-EL CI system turned out to be reasonably similar to those of the unaided ear. For adjustment of CI and contralateral HA, in contrast, an adjustable additional across-frequency delay in the range of 1–11 ms implemented in the CI would be required. Especially for bimodal CI/HA users the adjustment of interaural stimulation timing may induce improved binaural hearing, reduced need for central auditory temporal compensation and increased acceptance of the CI/HA provision.

CINGLE-trial: cochlear implantation for siNGLE-sided deafness, a randomised controlled trial and economic evaluation.

BackgroundIndividuals with single-sided deafness (SSD) have problems with speech perception in noise, localisation of sounds and with communication and social interaction in their daily life. Current treatment modalities (Contralateral Routing of Sound systems [CROS] and Bone Conduction Devices [BCD]) do not restore binaural hearing. Based on low level of evidence studies, CROS and BCD do not improve speech perception in noise or sound localisation. In contrast, cochlear implantation (CI) may overcome the limitations of CROS and BCD, as binaural input can be restored. Promising results have previously been achieved on speech perception in noise, sound localisation, tinnitus and quality of life.Methods and designA single-center Randomised Controlled Trial (RCT) was designed to compare all treatment strategies for SSD. One hundred and twenty adult single-sided deaf patients (duration of deafness >3 months and maximum 10 years; pure tone average at 0.5, 1, 2, 4 kHz, deaf ear: threshold equal to or more than 70 dB, better ear: threshold of maximum 30 dB) will be included in this trial and randomised to CI, ‘first BCD, then CROS’ or ‘first CROS, then BCD’-groups. After the trial period, patients in the two latter groups may choose with which treatment option they continue. Outcomes of interest are speech perception in noise, sound localization, tinnitus and quality of life. These outcomes will be measured during a baseline visit and at follow up visits, which will take place at 6, 12, 18, 24, 36, 48 and 60 months after onset of treatment. Furthermore, an economic evaluation will be performed and adverse events will be monitored.DiscussionThis RCT allows for a comparison between the two current treatment modalities for single-sided deafness and a new promising treatment strategy, CI, on a range of health outcomes: speech perception in noise, sound localization, tinnitus and quality of life. Additionally, we will be able to answer the question if the additional costs of CI are justified by increased benefits, when compared to current treatment strategies. This study will inform health policy makers with regard to reimbursement of CI.Trial registrationNetherlands Trial Register (www.trialregister.nl): NTR4580.

Release from informational masking in a monaural competing-speech task with vocoded copies of the maskers presented contralaterally.

Single-sided deafness prevents access to the binaural cues that help normal-hearing listeners extract target speech from competing voices. Little is known about how listeners with one normal-hearing ear might benefit from access to severely degraded audio signals that preserve only envelope information in the second ear. This study investigated whether vocoded masker-envelope information presented to one ear could improve performance for normal-hearing listeners in a multi-talker speech-identification task presented to the other ear. Target speech and speech or non-speech maskers were presented unprocessed to the left ear. The right ear received no signal, or either an unprocessed or eight-channel noise-vocoded copy of the maskers. Presenting the vocoded maskers contralaterally yielded significant masking release from same-gender speech maskers, albeit less than in the unprocessed case, but not from opposite-gender speech, stationary-noise, or modulated-noise maskers. Unmasking also occurred with as few as two vocoder channels and when an attenuated copy of the target signal was added to the maskers before vocoding. These data show that delivering masker-envelope information contralaterally generates masking release in situations where target-masker similarity impedes monaural speech-identification performance. By delivering speech-envelope information to a deaf ear, cochlear implants for single-sided deafness have the potential to produce a similar effect.