Contralateral hearing aid use in adult cochlear implant recipients: retrospective analysis of auditory outcomes

OBJECTIVE

To investigate retrospectively the frequency of usage of bimodal stimulation among cochlear implant (CI) users, as well its clinical benefit relative to unilateral use.

DESIGN

All subjects had been monitored with the clinical Minimal Outcome Measurements test battery.

STUDY SAMPLES

103 adults with bilateral postlingual profound sensorineural hearing loss and unilateral CI use were extracted from the local database. These were divided into two groups: those who only used a CI and those who used bimodal stimulation.

RESULTS

The preoperative contralateral residual hearing in the bimodal group was significantly better than that of the CI-only group. In both groups, speech perception in quiet and in noise improved after CI, with no significant difference between postoperative unimodal conditions. For the bimodal group, an additional significant improvement was found for the bimodal condition compared to the unimodal.

CONCLUSION

Given the observed auditory benefit of bimodal stimulation in comparison to unimodal stimulation and given the finding that degree of residual hearing is not correlated with bimodal benefits, it is recommended to encourage CI recipients to continue contralateral HA use after CI. As a result of expanding CI criteria worldwide, the population of bimodal users is expected to grow in the near future.

Parental insights on Hearing Aid Usage in the ear Contralateral to unilateral Cochlear Implant among Children

AIM & OBJECTIVES

The aim of the present study was in three-fold: (a) to analyze the factors that affect the hearing aid (HA) continuation/discontinuation in children with unilateral cochlear implant (CI); (b) to understand the parent's knowledge on binaural benefit; and (c) to find out any association between the hearing aid continuation/discontinuation with implant age and/or with duration of hearing aid use prior to surgery.

METHOD

The study involved 97 participants who were parents of children with unilateral cochlear implants. A questionnaire with 30 questions was used to explore HA use and certain related perceptions, and a Likert scale was used for ranking responses.

RESULTS

& Discussion: Only 31.9% children were using HA consistently, post CI activation The principal factor for discontinuation of HA was its helpfulness prior CI whereas children wore HA only because they were instructed during counseling. Participants did not perceive functional benefit bimodal fitting due to superiority of CI performance and poor residual hearing. Also, it was found that there is no association between neither the implant age nor duration of HA use before CI with the HA continuation/discontinuation on Chi-square test.

CONCLUSIONS

The results suggest a need for structured comprehensive counseling and demonstration sessions to educate parents on binaural hearing to gain maximum benefits from non-invasive bimodal fitting.

Binaural summation, binaural unmasking and fluctuating masker benefit in bimodal and bilateral adult cochlear implant users

OBJECTIVES

The number of bilateral adult cochlear implant (CI) users and bimodal CI users is expanding worldwide. The addition of a hearing aid (HA) in the contralateral non-implanted ear (bimodal) or a second CI (bilateral) can provide CI users with some of the benefits associated with listening with two ears. Our was to examine whether bilateral and bimodal CI users demonstrate binaural summation, binaural unmasking and a fluctuating masker benefit.

METHODS

Direct audio input was used to present stimuli to 10 bilateral and 10 bimodal Cochlear^TM CI users. Speech recognition in noise (speech reception threshold, SRT) was assessed monaurally, diotically (identical signals in both devices) and dichotically (antiphasic speech) with different masking noises (steady-state and interrupted), using the digits-in-noise test.

RESULTS

Bilateral CI users demonstrated a trend towards better SRTs with both CIs than with one CI. Bimodal CI users showed no difference between the bimodal SRT and the SRT for CI alone. No significant differences in SRT were found between the diotic and dichotic conditions for either group. Analyses of electrodograms created from bilateral stimuli demonstrated that substantial parts of the interaural speech cues were preserved in the Advanced Combination Encoder, an n-of-m channel selection speech coding strategy, used by the CI users. Speech recognition in noise was significantly better with interrupted noise than with steady-state masking noise for both bilateral and bimodal CI users.

CONCLUSION

Bilateral CI users demonstrated a trend towards binaural summation, but bimodal CI users did not. No binaural unmasking was demonstrated for either group of CI users. A large fluctuating masker benefit was found in both bilateral and bimodal CI users.

Self-assessment of unilateral and bimodal cochlear implant experiences in daily life

Objective

The subjective experiences were assessed of cochlear implant (CI) users either wearing or not wearing a hearing aid (HA) at the contralateral ear.

Design

Unilateral CI-recipients were asked to fill out a set of daily-life questionnaires on bimodal HA use, hearing disability, hearing handicap and general quality of life.

Study sample

Twenty-six CI-recipients who regularly use a contralateral HA (bimodal group) and twenty-two CI-recipients who do not use a HA in the contralateral ear (unilateral group).

Results

Comparisons between both groups (bimodal versus unilateral) showed no difference in self-rated disability, hearing handicap or general quality of life. However within the group of bimodal listeners, participants did report a benefit of bimodal hearing ability in various daily life listening situations.

Conclusions

Bimodal benefit in daily life can consistently be experienced and reported within the group of bimodal users.

Effect of (Mis)Matched Compression Speed on Speech Recognition in Bimodal Listeners

Automatic gain control (AGC) compresses the wide dynamic range of sounds to the narrow dynamic range of hearing-impaired listeners. Setting AGC parameters (time constants and knee points) is an important part of the fitting of hearing devices. These parameters do not only influence overall loudness elicited by the hearing devices but can also affect the recognition of speech in noise. We investigated whether matching knee points and time constants of the AGC between the cochlear implant and the hearing aid of bimodal listeners would improve speech recognition in noise. We recruited 18 bimodal listeners and provided them all with the same cochlear-implant processor and hearing aid. We compared the matched AGCs with the default device settings with mismatched AGCs. As a baseline, we also included a condition with the mismatched AGCs of the participants' own devices. We tested speech recognition in quiet and in noise presented from different directions. The time constants affected outcomes in the monaural testing condition with the cochlear implant alone. There were no specific binaural performance differences between the two AGC settings. Therefore, the performance was mostly dependent on the monaural cochlear implant alone condition.

Balancing the Loudness in Speech Processors and Contralateral Hearing Aids in Users of Unilateral Cochlear Implants

Introduction  The use of cochlear implants and hearing aids (bimodal) has been growing with the expansion of the indication for them, and it is important to ensure protocols so that there is a balance of the loudness regarding the two devices.

Objective  To evaluate if the limited complex sounds present in the frequency bands of the current devices enable the balance of the loudness in adult users of bimodal stimulation, and to analyze if speech recognition improves after balancing.

Methods  A prospective cross-sectional study with convenience sampling. The sample was composed of 25 adults who had used either a cochlear implant for at least 6 months or a contralateral hearing aid, with a mean age of 46 years. The balancing of the loudness was performed in an acoustic room with the computer's sound box (0° azimuth at 70 dB SPL). The instrumental sounds were filtered through eight different frequency bands. The patients used both hearing devices and were asked if the sound was perceived to be louder in one of the ears or centrally. The speech test was evaluated with sentence silence (65 dB SPL) and/or noise signal ratio of 0 dB/+ 10 dB in free field at 0° azimuth, before and after balancing.

Results : Out of the 25 patients, 5 failed to achieve balance at every tested frequency, and 3 achieved balance at almost every frequency, except 8 kHz. There was a significant difference between the speech recognition test only in silence before and after balancing.

Conclusion : Most patients achieved sound equalization at all evaluated frequencies under the complex-sound protocol. Additionally, most patients experienced improved speech recognition after balancing.

Evaluating hearing performance with cochlear implants within the same patient using daily randomization and imaging-based fitting - The ELEPHANT study

Background

Prospective research in the field of cochlear implants is hampered by methodological issues and small sample sizes. The ELEPHANT study presents an alternative clinical trial design with a daily randomized approach evaluating individualized tonotopical fitting of a cochlear implant (CI).

Methods

A single-blinded, daily-randomized clinical trial will be implemented to evaluate a new imaging-based CI mapping strategy. A minimum of 20 participants will be included from the start of the rehabilitation process with a 1-year follow-up period. Based on a post-operative cone beam CT scan (CBCT), mapping of electrical input will be aligned to natural place-pitch arrangement in the individual cochlea. The CI’s frequency allocation table will be adjusted to match the electrical stimulation of frequencies as closely as possible to corresponding acoustic locations in the cochlea. A randomization scheme will be implemented whereby the participant, blinded to the intervention allocation, crosses over between the experimental and standard fitting program on a daily basis, and thus effectively acts as his own control, followed by a period of free choice between both maps to incorporate patient preference. With this new approach the occurrence of a first-order carryover effect and a limited sample size is addressed.

Discussion

The experimental fitting strategy is thought to give rise to a steeper learning curve, result in better performance in challenging listening situations, improve sound quality, better complement residual acoustic hearing in the contralateral ear and be preferred by recipients of a CI. Concurrently, the suitability of the novel trial design will be considered in investigating these hypotheses.

Trial registration

ClinicalTrials.gov: NCT03892941. Registered 27 March 2019.

The Cost-Effectiveness of Bimodal Stimulation Compared to Unilateral and Bilateral Cochlear Implant Use in Adults with Bilateral Severe to Profound Deafness

OBJECTIVES

An increasing number of severe-profoundly deaf adult unilateral cochlear implant (CI) users receive bimodal stimulation; that is, they use a conventional acoustic hearing aid (HA) in their nonimplanted ear. The combination of electric and contralateral acoustic hearing provides additional benefits to hearing and also to general health-related quality of life compared with unilateral CI use. Bilateral CI is a treatment alternative to both unilateral CI and bimodal stimulation in some healthcare systems. The objective of this study was to conduct an economic evaluation of bimodal stimulation compared with other management options for adults with bilateral severe to profound deafness.

DESIGN

The economic evaluation took the form of a cost-utility analysis and compared bimodal stimulation (CI+HA) to two treatment alternatives: unilateral and bilateral CI. The analysis used a public healthcare system perspective based on data from the United Kingdom and the United States. Costs and health benefits were identified for both alternatives and estimated across a patient's lifetime using Markov state transition models. Utilities were based on Health Utilities Index estimates, and health outcomes were expressed in Quality Adjusted Life Years (QALYs). The results were presented using the Incremental Cost-Effectiveness Ratio and the Net Monetary Benefit approach to determine the cost-effectiveness of bimodal stimulation. Probabilistic sensitivity analyses explored the degree of overall uncertainty using Monte Carlo simulation. Deterministic sensitivity analyses and analysis of covariance identified parameters to which the model was most sensitive; that is, whose values had a strong influence on the intervention that was determined to be most cost-effective. A value of information analysis was performed to determine the potential value to be gained from additional research on bimodal stimulation.

RESULTS

The base case model showed that bimodal stimulation was the most cost-effective treatment option with a decision certainty of 72 and 67% in the United Kingdom and United States, respectively. Despite producing more QALYs than either unilateral CI or bimodal stimulation, bilateral CI was found not to be cost-effective because it was associated with excessive costs. Compared with unilateral CI, the increased costs of bimodal stimulation were outweighed by the gain in quality of life. Bimodal stimulation was found to cost an extra £174 per person in the United Kingdom ($937 in the US) and yielded an additional 0.114 QALYs compared with unilateral CI, resulting in an Incremental Cost-Effectiveness Ratio of £1521 per QALY gained in the United Kingdom ($8192/QALY in the United States). The most influential variable was the utility gained from the simultaneous use of both devices (CI+HA) compared with Unilateral CI. The value of further research was £4,383,922 at £20,000/QALY ($86,955,460 at $50,000/QALY in the United States).

CONCLUSIONS

This study provides evidence of the most cost-effective treatment alternative for adults with bilateral severe to profound deafness from publicly funded healthcare perspectives of the United Kingdom and United States. Bimodal stimulation was found to be more cost-effective than unilateral and bilateral CI across a wide range of willingness-to-pay thresholds. If there is scope for future research, conducting interventional designs to obtain utilities for bimodal stimulation compared with unilateral CI would reduce decision uncertainty considerably.

The Benefits of Bimodal Aiding on Extended Dimensions of Speech Perception: Intelligibility, Listening Effort, and Sound Quality

The benefits of combining a cochlear implant (CI) and a hearing aid (HA) in opposite ears on speech perception were examined in 15 adult unilateral CI recipients who regularly use a contralateral HA. A within-subjects design was carried out to assess speech intelligibility testing, listening effort ratings, and a sound quality questionnaire for the conditions CI alone, CIHA together, and HA alone when applicable. The primary outcome of bimodal benefit, defined as the difference between CIHA and CI, was statistically significant for speech intelligibility in quiet as well as for intelligibility in noise across tested spatial conditions. A reduction in effort on top of intelligibility at the highest tested signal-to-noise ratio was found. Moreover, the bimodal listening situation was rated to sound more voluminous, less tinny, and less unpleasant than CI alone. Listening effort and sound quality emerged as feasible and relevant measures to demonstrate bimodal benefit across a clinically representative range of bimodal users. These extended dimensions of speech perception can shed more light on the array of benefits provided by complementing a CI with a contralateral HA.

Bimodal benefit for cochlear implant listeners with different grades of hearing loss in the opposite ear

OBJECTIVE

To determine speech perception in quiet and noise of adult cochlear implant listeners retaining a hearing aid contralaterally. Second, to investigate the influence of contralateral hearing thresholds and speech perception on bimodal hearing.

PATIENTS AND METHODS

Sentence recognition with hearing aid alone, cochlear implant alone and bimodally at 6 months after cochlear implantation were assessed in 148 postlingually deafened adults. Data were analyzed for bimodal summation using measures of speech perception in quiet and in noise.

RESULTS

Most of the subjects showed improved sentence recognition in quiet and in noise in the bimodal condition compared to the hearing aid-only or cochlear implant-only mode. The large variability of bimodal benefit in quiet can be partially explained by the degree of pure tone loss. Also, subjects with better hearing on the acoustic side experience significant benefit from the additional electrical input.

CONCLUSIONS

Bimodal summation shows different characteristics in quiet and noise. Bimodal benefit in quiet depends on hearing thresholds at higher frequencies as well as in the lower- and middle-frequency ranges. For the bimodal benefit in noise, no correlation with hearing threshold in any frequency range was found.

Children With Single-Sided Deafness Use Their Cochlear Implant

OBJECTIVES

To assess acceptance of a cochlear implant (CI) by children with single-sided deafness (SSD) as measured by duration of CI use across daily listening environments.

DESIGN

Datalogs for 7 children aged 1.1 to 14.5 years (mean ± SD: 5.9 ± 5.9 years old), who had SSD and were implanted in their deaf ear, were anonymized and extracted from their CI processors. Data for all available follow-up clinical appointments were included, ranging from two to six visits. Measures calculated from each datalog included frequency and duration of time the coil disconnected from the internal device, average daily CI use, and both duration (hr/day) and percentage of CI use (% daily use) in different intensity ranges and environment types. Linear mixed effects regression analyses were used to evaluate the relationships between CI experience, daily CI use, frequency of coil-offs, and duration of coil-off time. Nonlinear regression analyses were used to evaluate CI use with age in different acoustic environments.

RESULTS

Children with SSD used their CI on average 7.4 hr/day. Older children used their CI for longer periods of the day than younger children. Longitudinal data indicated consistent CI use from the date of CI activation. Frequency of coil-offs reduced with CI experience, but did not significantly contribute to hours of coil-off time. Children used their CI longest in environments that were moderately loud (50 to 70 dB A) and classified as containing speech-in-noise. Preschoolers tended to spend less time in quiet but more time in music than infants/toddlers and adolescents.

CONCLUSIONS

Children with SSD consistently use their CI upon activation in a variety of environments commonly experienced by children. CI use in children with SSD resembles reported bilateral hearing aid use in children but is longer than reported hearing aid use in children with less severe unilateral hearing loss, suggesting that (1) the normal-hearing ear did not detract from consistent CI use; and (2) a greater asymmetry between ears presents a significant impairment that may facilitate device use to access bilateral sound.

Self-Reported Usage, Functional Benefit, and Audiologic Characteristics of Cochlear Implant Patients Who Use a Contralateral Hearing Aid

Ninety-four unilateral CI patients with bimodal listening experience (CI plus HA in contralateral ear) completed a questionnaire that focused on attitudes toward hearing aid use postimplantation, patterns of usage, and perceived bimodal benefits in daily life. Eighty participants continued HA use and 14 discontinued HA use at the time of the questionnaire. Participant responses provided useful information for counseling patients both before and after implantation. The majority of continuing bimodal (CI plus HA) participants reported adapting to using both devices within 3 months and also reported that they heard better bimodally in quiet, noisy, and reverberant conditions. They also perceived benefits including improved sound quality, better music enjoyment, and sometimes a perceived sense of acoustic balance. Those who discontinued HA use found either that using the HA did not provide additional benefit over the CI alone or that using the HA degraded the signal from the CI. Because there was considerable overlap in the audiograms and in speech recognition performance in the unimplanted ear between the two groups, we recommend that unilateral CI recipients are counseled to continue to use the HA in the contralateral ear postimplantation in order to determine whether or not they receive functional or perceived benefit from using both devices together.

Cochlear implantation: a review of current clinical practice

Cochlear implants treat severe hearing loss by providing direct electrical stimulation to auditory nerve endings. This article reviews the clinical assessment, surgical procedure and outcomes, and looks at newer developments such as preservation of residual hearing and bilateral implantation.

Monaural Beamforming in Bimodal Cochlear Implant Users: Effect of (A)symmetric Directivity and Noise Type

OBJECTIVE

To evaluate monaural beamforming in bimodally aided cochlear implant (CI) users.

DESIGN

The study enrolled twelve adult bimodal listeners with at least six months of CI-experience and using a contralateral hearing aid (HA) most of the daytime. Participants were uniformly fitted with the same CI speech processor and HA, giving access to an identical monaural beamformer in both ears. A within-subject repeated measures design evaluated three directional configurations [omnidirectional, asymmetric directivity (in CI alone) and symmetric directivity (in both CI and HA)] in two noise types [stationary and fluctuating]. Bimodal speech reception thresholds (SRT) as well as listening effort ratings were assessed in a diffuse noise field.

RESULTS

Symmetric monaural beamforming provided a significant SRT improvement of 2.6 dB SNR, compared to 1.6 dB SNR for asymmetric monaural beamforming. Directional benefits were similarly observed in stationary and fluctuating noise. Directivity did not contribute to less listening effort in addition to improvement in speech intelligibility. Bimodal performance was about 7 dB SNR worse in fluctuating than in stationary noise.

CONCLUSIONS

Monaural beamforming provided substantial benefit for speech intelligibility in noise for bimodal listeners. The greatest benefit occurred when monaural beamforming was activated symmetrically in both CI and HA. Monaural beamforming does not bridge the gap between bimodal and normal hearing performance, especially in fluctuating noise. Results advocate further bimodal co-operation.

TRIAL REGISTRATION

This trial was registered in www.trialregister.nl under number NTR4901.

Bimodal Stimulation in Prelingually Deaf Children: Lessons from a Cross-sectional Survey

OBJECTIVE

(1) To survey the use of bimodal stimulation by prelingually deaf children receiving unilateral cochlear implantation and (2) to investigate demographic and audiologic factors explaining the use of bimodal stimulation.

STUDY DESIGN

Cross-sectional survey.

SETTING

Tertiary care institution.

SUBJECTS AND METHODS

The study included 44 unilaterally implanted prelingually deaf children from a single institution, with a minimum follow-up of 1 year. During routine follow-up visits, an examiner interviewed parents on their children's use of bimodal stimulation. At the same time, residual hearing and hearing aid gain in the contralateral ear were assessed.

RESULTS

Approximately half of patients (52%) used bimodal stimulation. On average, bimodal users showed better mean unaided and aided thresholds than nonbimodal users (P < .001). A mean 250- to 500-Hz unaided threshold ≤90 dB HL in the contralateral, nonimplanted ear was associated with a higher probability of bimodal use (P = .008). Parental satisfaction with the contralateral hearing aid was inversely correlated with mean 125- to 500-Hz and 1000- to 4000-Hz unaided thresholds (P < .001) and mean 250- to 500-Hz and 1000- to 4000-Hz aided thresholds (P < .001).

CONCLUSIONS

A mean 250- to 500-Hz unaided threshold ≤90 dB HL is associated with a higher probability of bimodal use by prelingually deaf children. Better residual hearing is associated with a higher degree of parental satisfaction with the contralateral hearing aid. This information could be useful to counsel parents of prelingually deaf children, when deciding between bimodal stimulation and simultaneous bilateral cochlear implantation.