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

[Audiological outcome of bimodal CI users over time and depending on different influencing factors]

BACKGROUND

Hearing-impaired persons with asymmetric hearing loss and a unilateral indication for a cochlear implant (CI) generally benefit from a bimodal hearing solution. The influence of bimodal fitting on speech comprehension (SC) over time has not yet been sufficiently investigated. The present study examines the influence of bimodal fitting on SC in bimodally fitted CI users with postlingual deafness at least 36 months after implantation and analyzes possible influencing factors.

METHODS

Included in this retrospective longitudinal study were 54 bimodally fitted speech-competent CI users with at least 36 months of CI experience. Audiometric data of these CI users at predefined timepoints were compared.

RESULTS

The change in the results of the Freiburg monosyllabic test (FT) over 36 months was significant (p < 5%) for the deafness group at <10 years for both the 65 dB sound pressure level (SPL) and at 80 dB SPL and also significant for the deafness group ≥10 years for 65 dB SPL. In the Oldenburg sentence test (OlSa) there was a highly significant change (p < 0.1%) for S0, S0N0, and S0NCI configurations and a very significant change (p < 1%) for S0NHA (HA: hearing aid). Age at implantation as a possible influencing factor could not be confirmed in the FT. In contrast, the duration of deafness was a negative influencing factor for SC with CI in the FT, whereas a longer duration of deafness was associated with worse results in the FT. The degree of hearing loss in the ear fitted with an HA did not influence SC. The median bimodal benefit (here: difference in SC with bimodal fitting compared to unilateral HA fitting for FT at 65 dB SPL) was 10% over the total study period. For a median of 79% of the test subjects, the bimodal benefit was found over the entire period of 36 months.

CONCLUSION

Over time, SC improves significantly with a CI for the bimodal test subjects. The investigated influencing factors (age, duration of deafness, and degree of hearing loss in the contralateral ear) support the indication for bimodal provision in accordance with the guideline in Germany for cochlear implantation-regardless of age, duration of deafness, and hearing ability of the contralateral ear.

Impact of unilateral vs. bilateral evaluation on cochlear implant candidacy

BACKGROUND

The indication criteria for cochlear implantation differ considerably across regions.

OBJECTIVES

To estimate the effects of different candidacy criteria on the number of cochlear implant (CI) candidates.

METHODS

We analysed a very large clinical audiological database comprising pure-tone thresholds and speech-audiometric data in order to identify CI candidates on the basis of different audiometric candidacy criteria. In particular, we simulated the effects of three different CI candidacy criteria.

RESULTS

The bilateral evaluation of CI candidacy has the strongest influence on the number of potential CI candidates. Additionally, the cut-off criteria for middle-ear implants have a large effect on numbers of candidates when air conduction has deteriorated.Conclusions and Significance: Expanding the indication criteria opens up the possibility of improving the accurate identification of individual cases suitable for cochlear-implant provision.

Associations between illness perceptions, word recognition, and perceived sound quality in cochlear implant users

OBJECTIVE

Illness perceptions refer to thoughts and ideas an individual has about an illness. The aim was to understand how cochlear implant (CI) users' illness perceptions, in addition to their monosyllabic word recognition abilities, are associated with their self-perceived sound quality.

DESIGN

Data were collected during routine CI check-up appointments. Participants completed the Brief Illness Perception Questionnaire (assessing their illness perceptions) and the Hearing Implant Sound Quality Index (assessing their subjective sound quality). Additionally, monosyllabic word recognition abilities were measured with the Freiburg Monosyllable Word Test. Hierarchical regression analysis were utilised to model users' sound quality ratings. Participants' age was entered first as a control variable. In the next step, monosyllabic word recognition was entered. Finally, participants' illness perceptions were entered.

STUDY SAMPLE

Fifty-five participants with unilateral CI provision.

RESULTS

Monosyllabic word recognition was significant in the second step. When illness perceptions and monosyllabic word recognition were both included in the third step, illness perceptions, but not monosyllabic word recognition, were significant. The model explained 22% of the variance of subjective sound quality.

CONCLUSIONS

Monosyllabic word recognition abilities and illness perceptions of CI users are important for their self-reported sound quality, but illness perceptions appear to be potentially more relevant.

Outcome Prediction of Speech Perception in Quiet and in Noise for Cochlear Implant Candidates Based on Pre-Operative Measures

(1) Background: The fitting of cochlear implants (CI) is an established treatment, even in cases with considerable residual hearing but insufficient speech perception. The aim of this study was to evaluate a prediction model for speech in quiet and to provide reference data and a predictive model for postoperative speech perception in noise (SPiN) after CI provision. (2) Methods: CI candidates with substantial residual hearing (either in hearing threshold or in word recognition scores) were included in a retrospective analysis (n = 87). Speech perception scores in quiet 12 months post-surgery were compared with the predicted scores. A generalized linear model was fitted to speech reception thresholds (SRTs) after CI fitting to identify predictive variables for SPiN. (3) Results: About two-thirds of the recipients achieved the expected outcome in quiet or were better than expected. The mean absolute error of the prediction was 13.5 percentage points. Age at implantation was the only predictive factor for SPiN showing a significant correlation (r = 0.354; p = 0.007). (4) Conclusions: Outcome prediction accuracy for speech in quiet was comparable to previous studies. For CI recipients in the included study population, the SPiN outcome could be predicted only based on the factor age.

Comparison of speech perception in bimodal cochlear implant patients with respect to the cochlear coverage

BACKGROUND

The hearing success of patients with bimodal fitting, utilizing both a cochlear implant (CI) and a hearing aid (HA), varies considerably: While some patients benefit from bimodal CI and HA, others do not.

OBJECTIVES

This retrospective study aimed to investigate speech perception in bimodally fitted patients and compare it with the cochlear coverage (CC).

METHODS

The CC was calculated with the OTOPLAN software, measuring the cochlear duct length on temporal bone CT scans of 39 patients retrospectively. The patients were categorized into two groups: CC ≤ 65% (CC500) and CC > 65% (CC600). Monaural speech intelligibility for monosyllables at a sound pressure level (SPL) of 65 dB in a free-field setting was assessed before and after CI at various time points. The two groups, one with preoperative HA and one with postoperative CI, were compared. Additionally, speech intelligibility was correlated with CC in the entire cohort before CI and at the last available follow-up (last observation time, LOT).

RESULTS

Overall, there was no significant difference in speech intelligibility between CC500 and CC600 patients, with both groups demonstrating a consistent improvement after implantation. While CC600 patients tended to exhibit earlier improvement in speech intelligibility, CC500 patients showed a slower initial improvement within the first 3 months but demonstrated a steeper learning curve thereafter. At LOT, the two patient groups converged, with no significant differences in expected speech intelligibility. There was no significant relationship between unimodal/unilateral free-field speech intelligibility and CC. Interestingly, patients with a CC of 70-75% achieved the highest speech intelligibility.

CONCLUSION

Despite of the lack of a significant correlation between CC and speech perception, patients appeared to reach their maximum in unimodal/unilateral speech perception primarily at a coverage level of 70-75%. Nevertheless, further investigation is warranted, as CC500 was associated with shorter cochlear duct length, and different types of electrodes were used in both groups.

Effects of noise and noise reduction on audiovisual speech perception in cochlear implant users: An ERP study

OBJECTIVE

Hearing with a cochlear implant (CI) is difficult in noisy environments, but the use of noise reduction algorithms, specifically ForwardFocus, can improve speech intelligibility. The current event-related potentials (ERP) study examined the electrophysiological correlates of this perceptual improvement.

METHODS

Ten bimodal CI users performed a syllable-identification task in auditory and audiovisual conditions, with syllables presented from the front and stationary noise presented from the sides. Brainstorm was used for spatio-temporal evaluation of ERPs.

RESULTS

CI users revealed an audiovisual benefit as reflected by shorter response times and greater activation in temporal and occipital regions at P2 latency. However, in auditory and audiovisual conditions, background noise hampered speech processing, leading to longer response times and delayed auditory-cortex-activation at N1 latency. Nevertheless, activating ForwardFocus resulted in shorter response times, reduced listening effort and enhanced superior-frontal-cortex-activation at P2 latency, particularly in audiovisual conditions.

CONCLUSIONS

ForwardFocus enhances speech intelligibility in audiovisual speech conditions by potentially allowing the reallocation of attentional resources to relevant auditory speech cues.

SIGNIFICANCE

This study shows for CI users that background noise and ForwardFocus differentially affect spatio-temporal cortical response patterns, both in auditory and audiovisual speech conditions.

[Speech perception as a function of cochlear coverage-comparison in bimodally hearing cochlear implant patients. German version]

BACKGROUND

Hearing success in bimodally hearing patients with a cochlear implant (CI) and a hearing aid (HA) exhibits different results: while some benefit from bimodal CI and HA, others do not.

OBJECTIVE

The aim of this study was to investigate hearing success in terms of speech perception in bimodally fitted patients in relation to the cochlear coverage (CC) of the CI electrodes.

MATERIALS AND METHODS

Using the OTOPLAN software (CAScination AG, Bern, Switzerland), CC was retrospectively measured from CT scans of the temporal bone of 39 patients, who were then categorized into two groups: CC ≤ 65% (CC⁵⁰⁰) and CC > 65% (CC⁶⁰⁰). Monaural speech intelligibility for monosyllables at a sound pressure level (SPL) of 65 dB in open field was assessed at various timepoints, preoperatively with HA and postoperatively with CI, and compared between the groups. In addition, speech intelligibility was correlated with CC in the entire cohort before surgery and during follow-up (FU).

RESULTS

Overall, no significant differences in speech intelligibility were found between CC⁵⁰⁰ and CC⁶⁰⁰ patients at any of the FU timepoints. However, both CC⁵⁰⁰ and CC⁶⁰⁰ patients showed a steady improvement in speech intelligibility after implantation. While CC⁶⁰⁰ patients tended to show an earlier improvement in speech intelligibility, CC⁵⁰⁰ patients tended to show a slower improvement during the first 3 months and a steeper learning curve thereafter. The two patient groups converged during FU, with no significant differences in speech intelligibility. There was no significant relationship between unimodal/unilateral free-field speech intelligibility and CC. However, patients with a CC of 70-75% achieved maximum speech intelligibility.

CONCLUSION

Despite a nonsignificant correlation between CC and speech discrimination, patients seem to reach their maximum in unimodal/unilateral speech understanding mainly at 70-75% coverage. However, there is room for further investigation, as CC⁵⁰⁰ was associated with a shorter cochlear duct length (CDL), and long and very long electrodes were used in both groups.

Towards personalized and optimized fitting of cochlear implants

A cochlear implant (CI) is a neurotechnological device that restores total sensorineural hearing loss. It contains a sophisticated speech processor that analyzes and transforms the acoustic input. It distributes its time-enveloped spectral content to the auditory nerve as electrical pulsed stimulation trains of selected frequency channels on a multi-contact electrode that is surgically inserted in the cochlear duct. This remarkable brain interface enables the deaf to regain hearing and understand speech. However, tuning of the large (>50) number of parameters of the speech processor, so-called "device fitting," is a tedious and complex process, which is mainly carried out in the clinic through 'one-size-fits-all' procedures. Current fitting typically relies on limited and often subjective data that must be collected in limited time. Despite the success of the CI as a hearing-restoration device, variability in speech-recognition scores among users is still very large, and mostly unexplained. The major factors that underly this variability incorporate three levels: (i) variability in auditory-system malfunction of CI-users, (ii) variability in the selectivity of electrode-to-auditory nerve (EL-AN) activation, and (iii) lack of objective perceptual measures to optimize the fitting. We argue that variability in speech recognition can only be alleviated by using objective patient-specific data for an individualized fitting procedure, which incorporates knowledge from all three levels. In this paper, we propose a series of experiments, aimed at collecting a large amount of objective (i.e., quantitative, reproducible, and reliable) data that characterize the three processing levels of the user's auditory system. Machine-learning algorithms that process these data will eventually enable the clinician to derive reliable and personalized characteristics of the user's auditory system, the quality of EL-AN signal transfer, and predictions of the perceptual effects of changes in the current fitting.

An overview of factors affecting bimodal and electric-acoustic stimulation (EAS) speech understanding outcomes

Improvements in device technology, surgical technique, and patient outcomes have resulted in a broadening of cochlear implantation criteria to consider those with increasing levels of useful low-to-mid frequency residual acoustic hearing. Residual acoustic hearing allows for the addition of a hearing aid (HA) to complement the cochlear implant (CI) and has demonstrated enhanced listening outcomes. However, wide inter-subject outcome variability exists and thus identification of contributing factors would be of clinical interest and may aid with pre-operative patient counselling. The optimal fitting procedure and frequency assignments for the two hearing devices used in combination to enhance listening outcomes also remains unclear. The understanding of how acoustic and electric speech information is fundamentally combined and utilised by the listener may allow for the optimisation of device fittings and frequency allocations to provide best bimodal and electric-acoustic stimulation (EAS) patient outcomes. This article will provide an overview of contributing factors to bimodal and EAS listening outcomes, explore areas of contention, and discuss common study limitations.

Spatial speech-in-noise performance in simulated single-sided deaf and bimodal cochlear implant users in comparison with real patients

OBJECTIVE

Speech reception thresholds (SRTs) in spatial scenarios were measured in simulated cochlear implant (CI) listeners with either contralateral normal hearing, or aided hearing impairment (bimodal), and compared to SRTs of real patients, who were measured using the exact same paradigm, to assess goodness of simulation.

DESIGN

CI listening was simulated using a vocoder incorporating actual CI signal processing and physiologic details of electric stimulation on one side. Unprocessed signals or simulation of aided moderate or profound hearing impairment was used contralaterally. Three spatial speech-in-noise scenarios were tested using virtual acoustics to assess spatial release from masking (SRM) and combined benefit.

STUDY SAMPLE

Eleven normal-hearing listeners participated in the experiment.

RESULTS

For contralateral normal and aided moderately impaired hearing, bilaterally assessed SRTs were not statistically different from unilateral SRTs of the better ear, indicating "better-ear-listening". Combined benefit was only found for contralateral profound impaired hearing. As in patients, SRM was highest for contralateral normal hearing and decreased systematically with more severe simulated impairment. Comparison to actual patients showed good reproduction of SRTs, SRM, and better-ear-listening.

CONCLUSIONS

The simulations reproduced better-ear-listening as in patients and suggest that combined benefit in spatial scenes predominantly occurs when both ears show poor speech-in-noise performance.

Different modes of cochlear implantation in children: a comparative study on hearing and speech rehabilitation effects

Objective

To study the effectiveness of unilateral cochlear implantation, binaural-bimodal hearing devices, and bilateral cochlear implantation in children with inner-ear malformation.

Methods

This study comprised 261 patients who were allocated to inner-ear malformation or control groups. Twenty-four months after surgery, aided sound-field thresholds were tested, and the Meaningful Auditory Integration Scale, Infant-Toddler Meaningful Auditory Integration Scale, Meaningful Use of Speech Scale, Categories of Auditory Performance scale and Speech Intelligibility Rating test were completed.

Results

Aided sound-field thresholds were significantly better for bilateral cochlear implantation patients than for unilateral cochlear implantation or binaural-bimodal hearing device patients. There was no significant difference in Meaningful Auditory Integration Scale, Infant-Toddler Meaningful Auditory Integration Scale, or Categories of Auditory Performance scores among the three groups. The binaural-bimodal hearing device patients outperformed unilateral cochlear implantation patients on both Meaningful Use of Speech Scale and Speech Intelligibility Rating scores. No statistical difference was observed between the two subgroups.

Conclusion

Children who received bilateral cochlear implants have the best auditory awareness in a quiet environment. Children with binaural-bimodal hearing devices have better voice control and verbal skills than unilateral cochlear implantation patients, and people are more likely to understand them. Children with inner-ear malformations benefit from cochlear implantation.

Cochlear implantation in patients with asymmetric hearing loss: reporting and discussing the benefits in speech perception, speech reception threshold, squelch abilities, and patients’ reported outcomes

Objectives

This study presents the results obtained in a group of patients with asymmetric hearing loss undergoing cochlear implantation at our institution. Prognostic factors are discussed in relation to different rehabilitative approaches for asymmetric hearing loss remediation. The current literature is also discussed.

Methods

Nineteen adult patients with post-verbal asymmetric hearing loss were enrolled. The results were assessed by means of a speech perception test, completed in silence and with background noise, and a speech reception threshold test (Oldenburg Sentence Test). The subjectively perceived benefits were assessed using the Speech, Spatial and Qualities of Hearing Scale.

Results

Statistically significant improvements were achieved by all patients in terms of speech perception and speech reception threshold, and in subjective benefits.

Conclusion

The results confirm the literature findings which suggest that patients with asymmetric hearing loss generally gain substantial benefit from cochlear implantation because of the binaural input, with significant improvement in speech perception abilities in noise, speech reception threshold, and squelch abilities.

Comparison of Speech Test Outcomes After Cochlear Implantation in Patients With and Without Asymmetric Hearing Loss

OBJECTIVES

Determine whether asymmetric hearing loss (AHL) affects postoperative speech outcomes in cochlear implant (CI) patients.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary care hospital.

PATIENTS

Adult English-speaking patients with unilateral CIs implanted between 2014 and 2018 were stratified into NonAHL and AHL groups based on preoperative AzBio scores in quiet from the nonimplanted ear (0-50% vs. 51-100%, respectively).

INTERVENTIONS

CI surgery in the poorer performing ear.

MAIN OUTCOME MEASURES

Postoperative consonant-nucleusconsonant (CNC) word and AzBio sentence test scores in quiet and/or noise at +5 dB signal-to-noise ratio (SNR).

RESULTS

Of 512 patients, 33 non-AHL and 27 AHL patients were included. Average ages were 65.6 and 63.6 years, respectively. As expected, preoperative AzBio scores in quiet from the nonimplanted ear were higher in the AHL group (95% confidence interval [95%CI]: 66.4-76.4%) than the non-AHL group at baseline (95%CI: 12.3-23.6%). In both cohorts, AzBio scores in quiet from the implanted ear improved from baseline, with 24-month scores (95%CI: 73.8 - 84.9%) being higher than preoperative scores (95%CI: 13.2-23.1%). There were also significant differences in AzBio scores in quiet between cohorts overall (p  = 0.0120) on mixed model analysis, with the AHL group performing ∼6.4% better than the non-AHL group; however, differences were not significant when scores were stratified by time. In addition, there were no significant differences in CNC in quiet and AzBio scores in noise at +5 dB SNR between cohorts (p  = 0.1786 and p  = 0.6215, respectively).

CONCLUSIONS

After CI, patients with AHL can achieve scores on word and sentence tests at least comparable to traditional CI candidates, supporting the expansion of CI candidacy to include patients with AHL.

Modelling speech reception thresholds and their improvements due to spatial noise reduction algorithms in bimodal cochlear implant users

•

This paper compares two modelling approaches to predict the speech recognition ability of bimodal CI users and the benefit of using beamformers.

•

The modelling approaches vary in computational complexity and fitting requirements.

•

A complex cafeteria spatial scenario with three localized single noise source scenario and a diffuse multi-talker babble noise is used.

•

The automatic speech recognizer is more accurate across the different spatial scenarios and noise types and requires less fitting compared to the statistical modelling approach.

Spatial noise reduction algorithms (“beamformers”) can considerably improve speech reception thresholds (SRTs) for bimodal cochlear implant (CI) users. The goal of this study was to model SRTs and SRT-benefit due to beamformers for bimodal CI users. Two existing model approaches varying in computational complexity and binaural processing assumption were compared: (i) the framework of auditory discrimination experiments (FADE) and (ii) the binaural speech intelligibility model (BSIM), both with CI and aided hearing-impaired front-ends. The exact same acoustic scenarios, and open-access beamformers as in the comparison clinical study Zedan et al. (2021) were used to quantify goodness of prediction. FADE was capable of modeling SRTs ab-initio, i.e., no calibration of the model was necessary to achieve high correlations and low root-mean square errors (RMSE) to both, measured SRTs (r = 0.85, RMSE = 2.8 dB) and to measured SRT-benefits (r = 0.96). BSIM achieved somewhat poorer predictions to both, measured SRTs (r = 0.78, RMSE = 6.7 dB) and to measured SRT-benefits (r = 0.91) and needs to be calibrated for matching average SRTs in one condition. Greatest deviations in predictions of BSIM were observed in diffuse multi-talker babble noise, which were not found with FADE. SRT-benefit predictions of both models were similar to instrumental signal-to-noise ratio (iSNR) improvements due to the beamformers. This indicates that FADE is preferrable for modeling absolute SRTs. However, for prediction of SRT-benefit due to spatial noise reduction algorithms in bimodal CI users, the average iSNR is a much simpler approach with similar performance.

Effect of adaptive beamforming and noise reduction algorithms on speech intelligibility and noise tolerance in bimodal cochlear implant users

OBJECTIVE

To evaluate the effect of a directional microphone (beamformer) and continuous noise reduction algorithms (CNRs) in bimodally aided cochlear implant (CI) users and to find the optimum hearing aid (HA) and CI settings of the beamformer and CNRs.

METHODS

Speech reception threshold (SRT) and acceptable noise level (ANL) were assessed in twelve adult CI users for unilateral CI, unilateral HA and bimodal listening. To assess the effect of the UltraZoom beamformer and the ClearVoice™ and NoiseBlock CNRs on SRT and ANL, speech was presented from the front in multi-source speech-shaped noise.

RESULTS

With unilateral CI, application of UltraZoom resulted in a significant improvement of the median SRT and ANL by 3.8 and 4.3 dB, respectively. For bimodal listening with UltraZoom, a significant improvement of 3.5 dB in median SRT was found. There was no significant effect of using the CNRs on speech intelligibility in noise or noise tolerance in either listening condition.

CONCLUSION

UltraZoom should be applied on the CI to improve speech intelligibility in face to face conversations with multi-source background noise. However, due to the heterogeneous data, no recommendations for the settings of UltraZoom on the HA or of ClearVoice/NoiseBlock on either device can be given.

TRIAL REGISTRATION

German Clinical Trials Register identifier: DRKS00010807.

Speech comprehension across multiple CI processor generations: Scene dependent signal processing

OBJECTIVES

In clinical practice, characterization of speech comprehension for cochlear implant (CI) patients is typically administered by a set of suprathreshold measurements in quiet and in noise. This study investigates speech comprehension of the three most recent cochlear implant sound processors; CP810, CP910, and CP1000 (Cochlear Limited). To compare sound processor performance across generations and input dynamic range changes, the state-of-the art signal processing technologies available in each sound processor were enabled. Outcomes will be assessed across a range of stimulation intensities, and finally analyzed with respect to normal hearing listeners.

METHODS

In a prospective study, 20 experienced postlingually deafened CI patients who received a Nucleus CI in the ENT department of the University Hospital of SH in Kiel were recruited. Speech comprehension was measured in quiet at 40, 50, and 65 dBSPL with monosyllabic words as well as by speech reception threshold for two-digit numbers. In noise, speech reception thresholds were measured with the adaptive German matrix test with speech and noise in front.

RESULTS

We found that high levels of open-set speech comprehension are achieved at suprathreshold presentation levels in quiet. However, results at lower test levels have remained mostly unchanged for tested sound processors with default dynamic range. Expanding the lower limit of the acoustic input dynamic range yields better speech comprehension at lower presentation levels. In noise the application of ForwardFocus improves the speech reception. Overall, a continuous improvement for speech perception across three generations of CI sound processors was found.

CONCLUSIONS

Findings motivate further development of signal pre-processing, an additional focus of clinical work on lower stimulation levels, and automation of ForwardFocus.

LEVEL OF EVIDENCE

2.

Sound Localization Bias and Error in Bimodal Listeners Improve Instantaneously When the Device Delay Mismatch Is Reduced

Users of a cochlear implant (CI) in one ear, who are provided with a hearing aid (HA) in the contralateral ear, so-called bimodal listeners, are typically affected by a constant and relatively large interaural time delay offset due to differences in signal processing and differences in stimulation. For HA stimulation, the cochlear travelling wave delay is added to the processing delay, while for CI stimulation, the auditory nerve fibers are stimulated directly. In case of MED-EL CI systems in combination with different HA types, the CI stimulation precedes the acoustic HA stimulation by 3 to 10 ms. A self-designed, battery-powered, portable, and programmable delay line was applied to the CI to reduce the device delay mismatch in nine bimodal listeners. We used an A-B-B-A test design and determined if sound source localization improves when the device delay mismatch is reduced by delaying the CI stimulation by the HA processing delay (τ_HA). Results revealed that every subject in our group of nine bimodal listeners benefited from the approach. The root-mean-square error of sound localization improved significantly from 52.6° to 37.9°. The signed bias also improved significantly from 25.2° to 10.5°, with positive values indicating a bias toward the CI. Furthermore, two other delay values (τ_HA –1 ms and τ_HA +1 ms) were applied, and with the latter value, the signed bias was further reduced in some test subjects. We conclude that sound source localization accuracy in bimodal listeners improves instantaneously and sustainably when the device delay mismatch is reduced.

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.

Post-lingual deaf adult cochlear implant users' speech and voice characteristics: cochlear implant turned-on versus turned-off

BACKGROUND

A time-period of turning off cochlear implant (CI) might affect the speech and voice features of the CI users due to loss of auditory feedback monitoring.

OBJECTIVES

To evaluate Persian-speaking CI users' speech and voice parameters in a device-on/off experiment.

MATERIAL AND METHODS

Forty-eight Persian-speaking adults with post-linguistic deafness who had received a unilateral CI and 50 normally-hearing counterparts were recruited. All CI users had to fulfill three phases of speech sampling, including the device-on, device-off (a 5-hourly period), and once again device-on phase. Their Fundamental frequency, Jitter, Shimmer, Harmonics-to-noise ratio, hyper-nasality score, and the percentage of speech intelligibility were assessed for both groups.

RESULTS

The findings revealed that the CI-on/off conditions significantly changed cochlear implanted participants' F0, Shimmer, HNR, and hyper-nasality values. However, no statistical differences were observed in Jitter and the percentage of speech intelligibility between the CI and control groups.

CONCLUSIONS

A short-term auditory deprivation in CI recipients could degrade the speech and voice quality in CI users, so that could change the quality of their speech resonance into hyper-nasality. However, when the CIs were turned on again, the quality of their speech and voice returned to normal-sounding.

Spatial Release From Masking in Bimodal and Bilateral Pediatric Cochlear Implant Recipients

Purpose Traditional clinical measures of cochlear implant (CI) recipient performance may not fully evaluate the benefit of bimodal listening (hearing aid contralateral to a CI). The clinical assessment of spatial release from masking (SRM) may be a sensitive measure of the benefit of listening with bimodal stimulation. This study compared the SRM of pediatric bimodal and bilateral CI listeners using a clinically feasible method, and investigated variables that may contribute to speech recognition performance with spatially separated maskers. Method Forty pediatric bimodal (N = 20) and bilateral CI (N = 20) participants were assessed in their best aided listening condition on sentence recognition in a four-talker masker. Testing was completed with target and masker colocated at 0° azimuth, and with the masker directed at 90° to either ear. SRM was calculated as the difference in performance between the colocated and each 90° condition. A two-way mixed-methods analysis of variance was used to compare performance between groups in the three masker conditions. Multiple regression analyses were conducted to investigate potential predictors for SRM asymmetry including hearing history, unaided thresholds, word recognition, duration of device use, and acoustic bandwidth. Results Both groups demonstrated SRM, with significantly better recognition in each 90° condition as compared to the colocated condition. The groups did not differ significantly in SRM. The multiple regression analyses did not reveal any significant predictors of SRM asymmetry. Conclusions Bimodal and bilateral CI listeners demonstrated similar amounts of SRM. While no specific variables predicted SRM asymmetry in bimodal listeners, pediatric bimodal and bilateral CI recipients should expect similar amounts of SRM regardless of the side of the masker. SRM asymmetry in pediatric bimodal listeners may signal a need for consideration of a second CI.

Cochlear Implantation in Candidates With Moderate-to-Severe Hearing Loss and Poor Speech Perception

OBJECTIVES/HYPOTHESIS

To determine the improvement in word recognition score (WRS65 ) after cochlear implant (CI) surgery in hearing aid (HA) users with preoperative hearing threshold ≤80 dB HL and inadequate speech recognition scores with HA. Secondarily, to identify predictive factors for WRS65 with a CI (WRS65 [CI]) 6 months after surgery, derived from the standard German CI preoperative assessment.

STUDY DESIGN

Retrospective chart review.

METHODS

Retrospective review of all adult patients who received a Nucleus cochlear implant in the ear, nose, and throat department of the University Hospital of Erlangen between January 2010 and April 2019. The inclusion criteria were a preoperative hearing threshold ≤80 dB HL in the ear to receive the implantation, German as the native language, and at least 6 months postimplantation care at our center.

RESULTS

The inclusion criteria were met by 128 patients. All but two patients (98.4%) showed a significant improvement, WRS65 (CI) versus WRS65 with an (HA) (WRS65 [HA]), of at least 15 percentage points (pp). The median improvement was 55 pp with a median WRS65 (CI) of 70%. Three preoperative audiometric measures, the maximum word recognition score, age at implantation, and WRS65 (HA) were identified as predictive factors for WRS65 (CI). For three-quarters of the CI recipients, the score was not poorer than 12 pp below the predicted WRS65 (CI).

CONCLUSIONS

For patients with a hearing loss ≤80 dB HL, cochlear implantation should be considered when speech perception with an HA is insufficient. The prediction model can support counseling in this patient group.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E940-E945, 2021.

Bimodal cochlear implantation in elderly patients

OBJECTIVE

Bimodal stimulation is a standard option for asymmetric hearing loss in adults. Questions have been raised whether receiving two stimulations may conflict in elderly listeners where the central integration of an acoustic/electrical signal may be very important to obtain benefit in terms of speech perception.

DESIGN

Clinical retrospective study.

STUDY SAMPLE

The outcomes from 17 bimodal cochlear implant (CI) users were analysed. The test material consisted of speech audiometry in quiet and in noise (STARR and Matrix).

RESULTS

Bimodal PTA and speech perception both in quiet and in noise were significantly better than CI or HA alone. Age showed a significant effect on bimodal STARR outcomes. Similarly, bimodal STARR scores improved significantly in comparison to Better Ear.

CONCLUSION

Both Matrix and STARR tests were very difficult for many elderly CI listeners from the present study group, especially in unilateral listening condition. The performance improved significantly, emphasising a good integration of acoustic and electric hearing in this group of elderly bimodal listeners. Overall results highlighted how a specific study, based on speech perception in noise in the elderly listeners, might shed light on the effect of speech test modality on bimodal outcomes.

Nordic results of cochlear implantation in adults: speech perception and patient reported outcomes

BACKGROUND

Although cochlear implantation (CI) is widely performed in postlingually hearing-impaired adults in the Nordic countries, the literature on hearing outcomes remains scarce. Aims/objectives: To evaluate and correlate hearing outcomes after implantation.

METHODS

Prospective evaluation of 40 adult first-implantation recipients pre- and post-implantation with Dantale, the Danish Hearing in Noise Test (HINT), the Nijmegen Cochlear Implant Questionnaire (NCIQ) and the Speech, Spatial and Qualities of Hearing Scale (SSQ12).

RESULTS

Dantale_mean increased from 50% (95% CI [41.7,58.4])) to 73% (95% CI [66.6,80.1]) and 19% (95% CI [13.3,25.1]) to 40%(95% CI [32.1,46.7]) (quiet/noise). HINT_words increased from 71% (95% CI [58.8,83.8]) to 83% (95% CI [69.8,95.4]) and 59% (95% CI [46.2,70.6]) to 73% (95% CI [63.3,82.8]) (quiet/noise). NCIQ_mean changed from 277 (95% CI [252.4,301.6]) to 396 (95% CI [366.7,424.7]) and SSQ12_mean from 27 (95% CI [21.3,31.8]) to 48 (95% CI [39.4,55.6]). Correlations coefficients were r _s = 0.39-0.74 (p < .01) between Dantale/HINT, rs = 0.78 (p < .0001) between NCIQ/SSQ12, r _s = 0.41-0.59 (p < .01) between NCIQ/SSQ12 and Dantale and r _s = 0.24-0.41 (ns) between NCIQ/SSQ12 and HINT.

CONCLUSION

The study documents a high auditory performance and patient-perceived improvement after implantation and advocate broader awareness of implantation as treatment option in the growing population of severe-to-profound hearing-impaired adults. Correlations between hearing measures may influence future evaluation practices.

Evaluation of a synthetic version of the digits-in-noise test and its characteristics in CI recipients

OBJECTIVE

The goal of this study was the evaluation of a synthetic version of the Digits-in-Noise (DiN) in participants with normal hearing. Additionally, the basis characteristics of the DiN in CI recipients were investigated.

DESIGN AND STUDY SAMPLE

Twenty participants with normal hearing and 21 CI recipients with a Nucleus®-System ran two to three adaptive and up to five fixed measurements. Afterwards the discrimination function was measured with fixed signal-to-noise ratios.

RESULTS

All subjects were able to perform the DiN within three minutes per test run. The median speech reception threshold (SRT) for the NH was -8.1 dB_SNR, with a median steepness of 23%/dB_SNR. The median absolute test-retest difference in the NH group was 0.4 dB (range: 0 to 1.5 dB). In the CI group, the SRTs range from -6.6 to +12.4 dB_SNR with a median test-retest difference of 0.4 dB (range: 0 to 6.1 dB).

CONCLUSION

The synthetic DiN is a valuable complement of the audiometric test battery in CI recipients. The excellent applicability is also particularly helpful in poor performing CI recipients. With its small time exposure, it is a time- and cost-saving test, which could also be used at home via app to check the individual hearing success.

Improved binaural speech reception thresholds through small symmetrical separation of speech and noise

Speech perception in noise is challenging and is improved by binaural hearing. Since signal processing of assistive hearing devices often modifies or masks the peripheral binaural head-shadow or better-ear effects, central binaural processing should be measured separately. In a prospective study, 10 listeners with normal hearing were tested with the German matrix sentence test in a set-up with two loudspeakers located at opposite angles in the horizontal plane with respect to S₀N₀. The speech reception threshold (SRT) was investigated depending on the separation angle between speech and noise. The lowest (best) SRT was obtained for a separation of target and interfering source from S₀N₀ at an angle of about S_±60°N_∓60°. The derived normative curve was comparable to SRTs predicted by the binaural-speech-intelligibility-model. The systematic separation of signal and noise showed a significant improvement in speech intelligibility for normal-hearing people even for small separation angles. This experimental setting was verified. This study aimed to assess the effect of small sound source separation on binaural hearing and speech perception.

Listening in Noise Remains a Significant Challenge for Cochlear Implant Users: Evidence from Early Deafened and Those with Progressive Hearing Loss Compared to Peers with Normal Hearing

Cochlear implants (CIs) are the state-of-the-art therapy for individuals with severe to profound hearing loss, providing them with good functional hearing. Nevertheless, speech understanding in background noise remains a significant challenge. The purposes of this study were to: (1) conduct a novel within-study comparison of speech-in-noise performance across ages in different populations of CI and normal hearing (NH) listeners using an adaptive sentence-in-noise test, and (2) examine the relative contribution of sensory information and cognitive–linguistic factors to performance. Forty CI users (mean age 20 years) were divided into “early-implanted” <4 years (n = 16) and “late-implanted” >6 years (n = 11), all prelingually deafened, and “progressively deafened” (n = 13). The control group comprised 136 NH subjects (80 children, 56 adults). Testing included the Hebrew Matrix test, word recognition in quiet, and linguistic and cognitive tests. Results show poorer performance in noise for CI users across populations and ages compared to NH peers, and age at implantation and word recognition in quiet were found to be contributing factors. For those recognizing 50% or more of the words in quiet (n = 27), non-verbal intelligence and receptive vocabulary explained 63% of the variance in noise. This information helps delineate the relative contribution of top-down and bottom-up skills for speech recognition in noise and can help set expectations in CI counseling.

Bimodal Benefits for Lexical Tone Recognition: An Investigation on Mandarin-speaking Preschoolers with a Cochlear Implant and a Contralateral Hearing Aid

Pitch perception is known to be difficult for individuals with cochlear implant (CI), and adding a hearing aid (HA) in the non-implanted ear is potentially beneficial. The current study aimed to investigate the bimodal benefit for lexical tone recognition in Mandarin-speaking preschoolers using a CI and an HA in opposite ears. The child participants were required to complete tone identification in quiet and in noise with CI + HA in comparison with CI alone. While the bimodal listeners showed confusion between Tone 2 and Tone 3 in recognition, the additional acoustic information from the contralateral HA alleviated confusion between these two tones in quiet. Moreover, significant improvement was demonstrated in the CI + HA condition over the CI alone condition in noise. The bimodal benefit for individual subjects could be predicted by the low-frequency hearing threshold of the non-implanted ear and the duration of bimodal use. The findings support the clinical practice to fit a contralateral HA in the non-implanted ear for the potential benefit in Mandarin tone recognition in CI children. The limitations call for further studies on auditory plasticity on an individual basis to gain insights on the contributing factors to the bimodal benefit or its absence.

Spatial Speech-in-Noise Performance in Bimodal and Single-Sided Deaf Cochlear Implant Users

This study compared spatial speech-in-noise performance in two cochlear implant (CI) patient groups: bimodal listeners, who use a hearing aid contralaterally to support their impaired acoustic hearing, and listeners with contralateral normal hearing, i.e., who were single-sided deaf before implantation. Using a laboratory setting that controls for head movements and that simulates spatial acoustic scenes, speech reception thresholds were measured for frontal speech-in-stationary noise from the front, the left, or the right side. Spatial release from masking (SRM) was then extracted from speech reception thresholds for monaural and binaural listening. SRM was found to be significantly lower in bimodal CI than in CI single-sided deaf listeners. Within each listener group, the SRM extracted from monaural listening did not differ from the SRM extracted from binaural listening. In contrast, a normal-hearing control group showed a significant improvement in SRM when using two ears in comparison to one. Neither CI group showed a binaural summation effect; that is, their performance was not improved by using two devices instead of the best monaural device in each spatial scenario. The results confirm a "listening with the better ear" strategy in the two CI patient groups, where patients benefited from using two ears/devices instead of one by selectively attending to the better one. Which one is the better ear, however, depends on the spatial scenario and on the individual configuration of hearing loss.

Comparison of bimodal benefit for the use of DSL v5.0 and NAL-NL2 in cochlear implant listeners

Objective: For a group of bimodal subjects with moderate to severe hearing loss contralateral to the cochlear implant (CI), the bimodal benefit of the hearing aid (HA) gain prescriptions DSL v5.0, NAL-NL2 and the recipients' own gain setting were assessed.Design: Speech perception in quiet and in noise as well as self-reported ratings of benefit were determined for all three gain-settings. Speech tests were performed in the bimodal, the HA alone and the CI alone condition. The bimodal benefit was assessed for each prescription as the difference score of the bimodal condition and the better ear.Study Sample: Twenty adults with post-lingual hearing loss.Results: Speech perception with DSL v5.0 was significantly higher compared to NAL-NL2 and the own prescription in both quiet and noise. The median bimodal benefit was highest for DSL v5.0 with an average of 15 percentage points for both words in quiet and sentences in noise.Conclusions: DSL v5.0 and NAL-NL2 are both suitable for HA fitting in bimodal users. For subjects with moderate to severe hearing loss and HA experience contralateral to the implanted side, DSL v5.0 may provide better speech perception and bimodal benefit.

[Maximum monosyllabic score as a predictor for cochlear implant outcome]

OBJECTIVE

This study investigated the speech perception of cochlear implant (CI) recipients with measurable preoperative ipsilateral speech perception. These data should support improved individual counselling of CI candidates.

MATERIALS AND METHODS

Pre- and postoperative speech audiometric parameters were analyzed, including maximum score for phonemically balanced words (PB_max) and monosyllabic score at a normal conversational level of 65 dB_SPL, with hearing aids one hand and CI on the other. Data of 284 experienced adult CI wearers were grouped and evaluated in terms of preoperative PB_max.

RESULTS

The preoperative PB_max was exceeded by the postoperative monosyllabic score in 96% of cases. The overall median postoperative score was 72.5%. The groups with preoperative PB_max > 0% showed significantly better speech perception scores with CI than the group with PB_max = 0 %. Median improvement compared to the preoperative monosyllabic score with hearing aids was 65 percentage points, independent of preoperative PB_max.

CONCLUSION

The preoperatively measured PB_max may be used as a predictor for the minimum speech perception obtained with CI. This is of high clinical relevance for CI candidates with a PB_max above zero.

Maximum preimplantation monosyllabic score as predictor of cochlear implant outcome

Objective

This study investigated the speech perception of cochlear implant (CI) recipients with measurable preoperative ipsilateral speech perception. These data should support improved individual counselling of CI candidates.

Materials and methods

Pre- and postoperative speech audiometric parameters were analyzed, including maximum score for phonemically balanced words (PB_max) and monosyllabic score at a normal conversational level of 65 dB_SPL, with hearing aids one hand and CI on the other. Data of 284 experienced adult CI wearers were grouped and evaluated in terms of preoperative PB_max.

Results

The preoperative PB_max was exceeded by the postoperative monosyllabic score in 96% of cases. The overall median postoperative score was 72.5%. The groups with preoperative PB_max > 0% showed significantly better speech perception scores with CI than the group with PB_max = 0%. Median improvement compared to the preoperative monosyllabic score with hearing aids was 65 percentage points, independent of preoperative PB_max.

Conclusion

The preoperatively measured PB_max may be used as a predictor for the minimum speech perception obtained with CI. This is of high clinical relevance for CI candidates with a PB_max above zero.

[Postoperative legal disputes involving patients with cochlear implants]

BACKGROUND

After the implantation of one or two cochlear implants additional problems often arise concerning the question which further costs have to be covered by statutory insurances or other insurance providers, e.g. within the framework of integration aid.

OBJECTIVE

This article provides an overview of judgments rendered by the German social courts. It was investigated whether and in which cases it is advisable for a patient to go to court, and how long the proceedings may take.

MATERIAL AND METHODS

A search was made for judgments in the two biggest commercial legal databases and in the database of the German social courts, using combinations of the search parameters "Cochlear", "Cochlea", "Implant", and "Implantat". The reviewed judgments were issued between 2002 and 2017.

RESULTS

A total of 13 judgments were found. The results varied according to the specifics of the individual case and 54% of the patients won their cases. The court procedures took between 2 months (starting from the filing of a complaint, date of application in this case unknown), and 6 years and 11 months.

CONCLUSION

This study showed that it is uncertain whether costs that are not caused directly by the surgery or the postoperative treatment will be remunerated. As each case is in principle unique, the results vary. Nevertheless, taking legal action is recommended after thorough consideration in cases where statutory insurances or other providers refuse to meet expenses incurred.