Cochlear Implantation Improves Spatial Release From Masking and Restores Localization Abilities in Single-sided Deaf Patients

Recent advances in Otology: Current landscape and future direction

Hearing is an essential sensation, and its deterioration leads to a significant decrease in the quality of life. Thus, great efforts have been made by otologists to preserve and recover hearing. Our knowledge regarding the field of otology has progressed with advances in technology, and otologists have sought to develop novel approaches in the field of otologic surgery to achieve higher hearing recovery or preservation rates. This requires knowledge regarding the anatomy of the temporal bone and the physiology of hearing. Basic research in the field of otology has progressed with advances in molecular biology and genetics. This review summarizes the current views and recent advances in the field of otology and otologic surgery, especially from the viewpoint of young Japanese clinician-scientists, and presents the perspectives and future directions for several topics in the field of otology. This review will aid next-generation researchers in understanding the recent advances and future challenges in the field of otology.

Active TriCROS: A Simultaneous Stimulation With a (Bi)CROS System and a Hearing Aid in the Worst Ear for Severely Asymmetrical Hearing Loss

OBJECTIVE

Severely asymmetrical hearing loss (SAHL) is characterized by a moderately severe or severe hearing loss in one side and normal or mildly impaired controlateral hearing in the other. The Active tri-CROS combines the Contralateral Routing-of-Signal System (CROS, or BiCROS if the best ear is stimulated) and the stimulation of the worst ear by an in-the-canal hearing aid. This study aims to evaluate the benefit of the Active tri-CROS for SAHL patients.

STUDY DESIGN

This retrospective study was conducted from September 2019 to December 2020.

SETTING

Ambulatory, tertiary care.

PATIENTS

Patients were retrospectively included if they had received the Active tri-CROS system after having used a CROS or BiCROS system for SAHL for at least 3 years.

MAIN OUTCOME MEASURES

Audiometric gain, signal-to-noise ratio, spatial localization, and the Abbreviated Profile of Hearing Aid Benefit and Tinnitus Handicap Inventory questionnaires were performed before equipment and after a month with the system.

RESULTS

Twenty patients (mean, 62 yr old) with a mean of 74.3 ± 8.7 dB HL on the worst ear were included. The mean tonal hearing gain on the worst ear was 20 ± 6 dB. Signal-to-noise ratio significantly rose from 1.43 ± 3.9 to 0.16 ± 3.4 dB ( p = 0.0001). Spatial localization was not significantly improved. The mean Tinnitus Handicap Inventory test score of the eight patients suffering from tinnitus rose from 45.5 ± 18.5 to 31 ± 25.2 ( p = 0.016).

CONCLUSIONS

The Active tri-CROS system is a promising new therapeutically solution for SAHL.

Prospective study of sound localisation in patients with single sided deafness and asymmetric hearing loss treated with cochlear implant

BACKGROUND AND OBJECTIVE

Sound localization plays a crucial role in our daily lives, enabling us to recognize voices, respond to alarming situations, avoid dangers, and navigate towards specific signals. However, this ability is compromised in patients with Single-Sided Deafness (SSD) and Asymmetric Hearing Loss (AHL), negatively impacting their daily functioning. The main objective of the study was to quantify the degree of sound source localization in patients with single-sided deafness or asymmetric hearing loss using a Cochlear Implant (CI) and to compare between the two subgroups.

MATERIALS AND METHODS

This was a prospective, longitudinal, observational, single-center study involving adult patients diagnosed with profound unilateral or asymmetric sensorineural hearing loss who underwent cochlear implantation. Sound localization was assessed in a chamber equipped with seven speakers evenly distributed from -90º to 90º. Stimuli were presented at 1000 Hz and intensities of 65 dB, 70 dB, and 75 dB. Each stimulus was presented only once per speaker, totaling 21 presentations. The number of correct responses at different intensities was recorded, and angular error in degrees was calculated to determine the mean angular distance between the patient-indicated speaker and the speaker presenting the stimulus. Both assessments were conducted preoperatively without a cochlear implant and two years post-implantation.

RESULTS

The total sample comprised 20 patients, with 9 assigned to the SSD group and 11 to the AHL group. The Preoperative Pure Tone Average (PTA) in free field was 31.7 dB in the SSD group and 41.8 dB in the AHL group. There was a statistically significant improvement in sound localization ability and angular error with the use of the cochlear implant at all intensities in both SSD and AHL subgroups.

CONCLUSIONS

Cochlear implantation in patients with SSD and AHL enhances sound localization, reducing mean angular error and increasing the number of correct sound localization responses.

Masked Speech Perception with Bone Conduction Device, Contralateral Routing of Signals Hearing Aid, and Cochlear Implant Use in Adults with Single-Sided Deafness: A Prospective Hearing Device Comparison using a Unified Testing Framework

INTRODUCTION

For the treatment of single-sided deafness (SSD), common treatment choices include a contralateral routing of signals (CROS) hearing aid, a bone conduction device (BCD), and a cochlear implant (CI). The primary aim of this study was to compare speech understanding in noise and binaural benefits in adults with postlingual SSD between preoperative unaided baseline, preoperative CROS and BCD trial devices, and CI, following recommendations from a consensus protocol. In addition, we investigated the effect of masker type on speech understanding.

METHODS

This was a prospective study with twelve participants. Binaural effects of head shadow, squelch, summation, and spatial release from masking were assessed by measuring speech reception thresholds (SRTs) in five different spatial target-masker configurations using two different maskers: two-talker babble (TTB), and speech-shaped noise (SSN). Preoperatively, participants were assessed unaided and with CROS and BCD trial devices. After cochlear implantation, participants were assessed at 1, 3, and 6 months post-activation.

RESULTS

For TTB, significant improvements in SRT with a CI relative to preoperatively unaided were found in all spatial configurations. With CI at 6 months, median benefits were 7.8 dB in SSSDNAH and 5.1 dB in S0NAH (head shadow), 3.4 dB in S0N0 (summation), and 4.6 dB in S0NSSD and 5.1 dB in SAHNSSD (squelch). CROS yielded a significant head shadow benefit of 2.4 dB in SSSDNAH and a significant deterioration in squelch of 2.5 dB in S0NSSD and SAHNSSD, but no summation effect. With BCD, there was a significant summation benefit of 1.5 dB, but no head shadow nor squelch effect. For SSN, significant improvements in SRT with CI compared to preoperatively unaided were found in three spatial configurations. Median benefits with CI at 6 months were: 8.5 dB in SSSDNAH and 4.6 dB in S0NAH (head shadow), 1.4 dB in S0N0 (summation), but no squelch. CROS showed a significant head shadow benefit of 1.7 dB in SSSDNAH, but no summation effect, and a significant deterioration in squelch of 2.9 dB in S0NSSD and 3.2 dB in SAHNSSD. With BCD, no binaural effect was obtained. Longitudinally, we found significant head shadow benefits with a CI in SSSDNAH in both maskers at all postoperative intervals and in S0NAH at 3 and 6 months post-activation.

CONCLUSION

With a CI, a clear benefit for masked speech perception was observed for all binaural effects. Benefits with CROS and BCD were more limited. CROS usage was detrimental to the squelch effect.

Early cochlear implantation supports narrative skills of children with prelingual single-sided deafness

Prelingual single-sided deafness (SSD) not only affects children's hearing skills, but can also lead to speech-language delays and academic underachievement. Early cochlear implantation leads to improved spatial hearing, but the impact on language development is less studied. In our longitudinal study, we assessed the language skills of young children with SSD and a cochlear implant (CI). In particular, we investigated their narrative skills in comparison to two control groups: children with SSD without a CI, and children with bilateral normal hearing. We found that children with SSD and a CI performed in line with their normal-hearing peers with regard to narrative and verbal short-term memory skills. Children with SSD without a CI had worse narrative (group difference = - 0.67, p = 0.02) and verbal short-term memory (group difference = - 0.68, p = 0.03) scores than the implanted group. Verbal short-term memory scores and grammar scores each correlated positively with narrative scores across all groups. Early grammar scores (at 2-3 years of age) could partially predict later narrative scores (at 4-6 years of age). These results show that young children with prelingual SSD can benefit from early cochlear implantation to achieve age-appropriate language skills. They support the provision of a CI to children with prelingual SSD.

Long-Term Binaural Hearing Improvements for Cochlear Implant Users with Asymmetric Hearing Loss

OBJECTIVE

To assess long-term binaural hearing abilities for cochlear implant (CI) users with unilateral hearing loss (UHL) or asymmetric hearing loss (AHL).

METHODS

A prospective, longitudinal, repeated measures study was completed at a tertiary referral center evaluating adults with UHL or AHL undergoing cochlear implantation. Binaural hearing abilities were assessed with masked speech recognition tasks using AzBio sentences in a 10-talker masker. Performance was evaluated as the ability to benefit from spatial release from masking (SRM). SRM was calculated as the difference in scores when the masker was presented toward the CI-ear (SRMci ) or the contralateral ear (SRMcontra ) relative to the co-located condition (0°). Assessments were completed pre-operatively and at annual intervals out to 5 years post-activation.

RESULTS

Twenty UHL and 19 AHL participants were included in the study. Linear Mixed Models showed significant main effects of interval and group for SRMcontra . There was a significant interaction between interval and group, with UHL participants reaching asymptotic performance early and AHL participants demonstrating continued growth in binaural abilities to 5 years post-activation. The improvement in SRM showed a significant positive correlation with contralateral unaided hearing thresholds (p = 0.050) as well as age at implantation (p = 0.031).

CONCLUSIONS

CI recipients with UHL and AHL showed improved SRM with long-term device use. The time course of improvement varied by cohort, with the UHL cohort reaching asymptotic performance early and the AHL cohort continuing to improve beyond 1 year. Differences between cohorts could be driven by differences in age at implantation as well as contralateral unaided hearing thresholds.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:1480-1485, 2023.

Cochlear Implantation Outcomes in Adults With Single-Sided Deafness: A Systematic Review and Meta-analysis

OBJECTIVE

To assess spatial hearing, tinnitus, and quality-of-life outcomes in adults with single-sided deafness (SSD) who underwent cochlear implantation.

DATABASES REVIEWED

PubMed, MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus databases were searched from January 2008 to September 2021 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

METHODS

Studies reporting spatial hearing, tinnitus, and quality-of-life outcomes in adult cochlear implant (CI) recipients (≥18 yr old) with SSD were evaluated. Study characteristics, demographic data, spatial hearing (speech recognition in noise, sound source localization), tinnitus (severity, loudness), and quality-of-life outcomes were collected.

RESULTS

From an initial search of 1,147 articles, 36 studies that evaluated CI use in 796 unique adults with SSD (51.3 ± 12.4 yr of age at time of implantation) were included. The mean duration of deafness was 6.2 ± 9.6 years. There was evidence of improvement for speech recognition in noise using different target-to-masker spatial configurations, with the largest benefit observed for target-to-masker configurations assessing head shadow (mean, 1.87-6.2 dB signal-to-noise ratio). Sound source localization, quantified as root-mean-squared error, improved with CI use (mean difference [MD], -25.3 degrees; 95% confidence interval [95% CI], -35.9 to -14.6 degrees; p < 0.001). Also, CI users reported a significant reduction in tinnitus severity as measured with the Tinnitus Handicap Inventory (MD, -29.97; 95% CI, -43.9 to -16.1; p < 0.001) and an improvement in spatial hearing abilities as measured with the Spatial, Speech, and Qualities of Hearing questionnaire (MD, 2.3; 95% CI, 1.7 to 2.8; p < 0.001).

CONCLUSIONS

Cochlear implantation and CI use consistently offer improvements in speech recognition in noise, sound source localization, tinnitus, and perceived quality of life in adults with SSD.

Cochlear Implantation in Adults With Single-Sided Deafness: A Systematic Review and Meta-analysis

OBJECTIVE

To determine the clinical outcomes of adult patients with single-sided deafness (SSD) undergoing ipsilateral cochlear implantation.

DATA SOURCE

An electronic search of Medline and Embase articles.

REVIEW METHODS

A systematic review was performed with a search strategy developed by a licensed librarian to identify studies of adult patients with SSD who underwent ipsilateral cochlear implantation. Articles were managed in Covidence and evaluated by 2 independent reviewers. Risk of bias was assessed and data were extracted, including patient demographics, etiology of deafness, duration of deafness, and postoperative change in speech recognition, tinnitus, sound localization, and quality of life (QoL). A meta-analysis was performed, and pooled mean differences were calculated for each outcome of interest via random effects models by each outcome, as well as subgroup analyses by the individual clinical score used.

RESULTS

Of 2309 studies identified, 185 full texts were evaluated, and 50 were ultimately included involving 674 patients. Speech perception scores in quiet and noise, tinnitus control, sound localization, and QoL all significantly improved after implantation. Pooled outcomes demonstrated score improvements in speech perception (standardized mean difference [SMD], 2.8 [95% CI, 2.16-3.43]), QoL (SMD, 0.68 [95% CI, 0.45-0.91]), sound localization (SMD, -1.13 [95% CI, -1.68 to -0.57]), and tinnitus score reduction (SMD, -1.32 [95% CI, -1.85 to -0.80]).

CONCLUSIONS

Cochlear implantation in adults with SSD results in significant improvements in speech perception, tinnitus control, sound localization, and QoL.

LEVEL OF EVIDENCE: 2

Sound localisation of low- and high-frequency sounds in cochlear implant users with single-sided deafness

OBJECTIVE

Localisation of low- and high-frequency sounds in single-sided deaf cochlear implant users was investigated using noise stimuli designed to mitigate monaural localisation cues.

DESIGN

Within subject design. Sound source localisation was tested in the horizontal plane using an array of seven loudspeakers along the azimuthal angle span from -90° to +90°. Stimuli were broadband noise and high- and low-frequency noise.

STUDY SAMPLE

Twelve adult subjects with single-sided deafness participated in the study. All had normal hearing in the healthy ear and were supplied with a cochlear implant (CI) in their deaf ear.

RESULTS

With broadband noise, the mean angular localisation error was 39° in aided condition as compared to a median angular error of 83.6° when the speech processor was not worn. For high-frequency noise, the median angular error was 30° and for low-frequency noise, it was 46° in the CI-aided condition.

CONCLUSIONS

Single-sided deaf CI users show the best sound localisation for high-frequency sounds. This supports the view that interaural level differences are dominant for sound localisation in these listeners. Nonetheless, a limited ability to localise low-frequency sounds was observed, which may be based on the supportive perception of interaural time differences.

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.

Long-Term Improvement in Localization for Cochlear Implant Users with Single-Sided Deafness

OBJECTIVES/HYPOTHESIS

To assess whether early, significant improvements in sound source localization observed in cochlear implant (CI) recipients with normal hearing (NH) in the contralateral ear are maintained after 5 years of CI use.

STUDY DESIGN

Prospective, repeated measures study.

METHODS

Participants were recruited from a sample of CI + NH listeners (n = 20) who received their device as part of a prospective clinical trial investigating outcomes of CI use for adult cases of single-sided deafness. Sound source localization was assessed annually after the clinical trial endpoint (1-year post-activation). Listeners were asked to indicate the perceived sound source for a broadband noise burst presented randomly at varied intensity levels from one of 11 speakers along a 180° arc. Performance was quantified as root-mean-squared (RMS) error.

RESULTS

Linear mixed models showed superior post-activation performance was maintained with long-term CI use as compared to preoperative abilities (P < .001). Unexpectedly, a significant improvement (P = .009) in sound source localization was observed over the long-term post-activation period (1-5 years). To better understand these long-term findings, the response patterns for the 11 participants who were evaluated at the 1- and 5-year visits were reviewed. This subgroup demonstrated a significant improvement in RMS error (P = .020) and variable error (P = .031), indicating more consistent responses at the 5-year visit.

CONCLUSION

Adult CI + NH listeners experience significant improvements in sound source localization within the initial weeks of listening experience, with additional improvements observed after long-term device use. The present sample demonstrated significant improvements between the 1-year and 5-year visits, with greater accuracy and consistency noted in their response patterns.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:2453-2458, 2022.

Towards a Consensus on an ICF-Based Classification System for Horizontal Sound-Source Localization

The study aimed to develop a consensus classification system for the reporting of sound localization testing results, especially in the field of cochlear implantation. Against the background of an overview of the wide variations present in localization testing procedures and reporting metrics, a novel classification system was proposed to report localization errors according to the widely accepted International Classification of Functioning, Disability and Health (ICF) framework. The obtained HEARRING_LOC_ICF scale includes the ICF graded scale: 0 (no impairment), 1 (mild impairment), 2 (moderate impairment), 3 (severe impairment), and 4 (complete impairment). Improvement of comparability of localization results across institutes, localization testing setups, and listeners was demonstrated by applying the classification system retrospectively to data obtained from cohorts of normal-hearing and cochlear implant listeners at our institutes. The application of our classification system will help to facilitate multi-center studies, as well as allowing better meta-analyses of data, resulting in improved evidence-based practice in the field.

American Cochlear Implant Alliance Task Force Guidelines for Clinical Assessment and Management of Adult Cochlear Implantation for Single-Sided Deafness

The indications for cochlear implantation have expanded to include individuals with profound sensorineural hearing loss in the impaired ear and normal hearing (NH) in the contralateral ear, known as single-sided deafness (SSD). There are additional considerations for the clinical assessment and management of adult cochlear implant candidates and recipients with SSD as compared to conventional cochlear implant candidates with bilateral moderate to profound sensorineural hearing loss. The present report reviews the current evidence relevant to the assessment and management of adults with SSD. A systematic review was also conducted on published studies that investigated outcomes of cochlear implant use on measures of speech recognition in quiet and noise, sound source localization, tinnitus perception, and quality of life for this patient population. Expert consensus and systematic review of the current literature were combined to provide guidance for the clinical assessment and management of adults with SSD.

Masked Speech Recognition as a Function of Masker Location for Cochlear Implant Users With Single-Sided Deafness

PURPOSE

Cochlear implant (CI) recipients with normal or near normal hearing (NH) in the contralateral ear, referred to as single-sided deafness (SSD), experience significantly better speech recognition in noise with their CI than without it, although reported outcomes vary. One possible explanation for differences in outcomes across studies could be differences in the spatial configurations used to assess performance. This study compared speech recognition for different spatial configurations of the target and masker, with test materials used clinically.

METHOD

Sixteen CI users with SSD completed tasks of masked speech recognition presented in five spatial configurations. The target speech was presented from the front speaker (0° azimuth). The masker was located either 90° or 45° toward the CI-ear or NH-ear or colocated with the target. Materials were the AzBio sentences in a 10-talker masker and the Bamford-Kowal-Bench Speech-in-Noise test (BKB-SIN; four-talker masker). Spatial release from masking (SRM) was computed as the benefit associated with spatial separation relative to the colocated condition.

RESULTS

Performance was significantly better when the masker was separated toward the CI-ear as compared to colocated. No benefit was observed for spatial separations toward the NH-ear. The magnitude of SRM for spatial separations toward the CI-ear was similar for 45° and 90° when tested with the AzBio sentences, but a larger benefit was observed for 90° as compared to 45° for the BKB-SIN.

CONCLUSIONS

Masked speech recognition in CI users with SSD varies as a function of the spatial configuration of the target and masker. Results supported an expansion of the clinical test battery at the study site to assess binaural hearing abilities for CI candidates and recipients with SSD. The revised test battery presents the target from the front speaker and the masker colocated with the target, 90° toward the CI-ear, or 90° toward the NH-ear.

Sound Source Localization by Cochlear Implant Recipients with Normal Hearing in the Contralateral Ear: Effects of Spectral Content and Duration of Listening Experience

INTRODUCTION

Cochlear implant (CI) recipients with normal hearing (NH) in the contralateral ear experience a significant improvement in sound source localization when listening with the CI in combination with their NH-ear (CI + NH) as compared to with the NH-ear alone. The improvement in localization is primarily due to sensitivity to interaural level differences (ILDs). Sensitivity to interaural timing differences (ITDs) may be limited by auditory aging, frequency-to-place mismatches, the signal coding strategy, and duration of CI use. The present report assessed the sensitivity of ILD and ITD cues in CI + NH listeners who were recipients of long electrode arrays that provide minimal frequency-to-place mismatches and were mapped with a coding strategy that presents fine structure cues on apical channels.

METHODS

Sensitivity to ILDs and ITDs for localization was assessed using broadband noise (BBN), as well as high-pass (HP) and low-pass (LP) filtered noise for adult CI + NH listeners. Stimuli were 200-ms noise bursts presented from 11 speakers spaced evenly over an 180° arc. Performance was quantified in root-mean-squared error and response patterns were analyzed to evaluate the consistency, accuracy, and side bias of the responses. Fifteen listeners completed the task at the 2-year post-activation visit; seven listeners repeated the task at a later annual visit.

RESULTS

Performance at the 2-year visit was best with the BBN and HP stimuli and poorer with the LP stimulus. Responses to the BBN and HP stimuli were significantly correlated, consistent with the idea that CI + NH listeners primarily use ILD cues for localization. For the LP stimulus, some listeners responded consistently and accurately and with limited side bias, which may indicate sensitivity to ITD cues. Two of the 7 listeners who repeated the task at a later annual visit experienced a significant improvement in performance with the LP stimulus, which may indicate that sensitivity to ITD cues may improve with long-term CI use.

CONCLUSIONS

CI recipients with a NH-ear primarily use ILD cues for sound source localization, though some may use ITD cues as well. Sensitivity to ITD cues may improve with long-term CI listening experience.

Sound Localization in Single-Sided Deaf Participants Provided With a Cochlear Implant

Spatial hearing is crucial in real life but deteriorates in participants with severe sensorineural hearing loss or single-sided deafness. This ability can potentially be improved with a unilateral cochlear implant (CI). The present study investigated measures of sound localization in participants with single-sided deafness provided with a CI. Sound localization was measured separately at eight loudspeaker positions (4°, 30°, 60°, and 90°) on the CI side and on the normal-hearing side. Low- and high-frequency noise bursts were used in the tests to investigate possible differences in the processing of interaural time and level differences. Data were compared to normal-hearing adults aged between 20 and 83. In addition, the benefit of the CI in speech understanding in noise was compared to the localization ability. Fifteen out of 18 participants were able to localize signals on the CI side and on the normal-hearing side, although performance was highly variable across participants. Three participants always pointed to the normal-hearing side, irrespective of the location of the signal. The comparison with control data showed that participants had particular difficulties localizing sounds at frontal locations and on the CI side. In contrast to most previous results, participants were able to localize low-frequency signals, although they localized high-frequency signals more accurately. Speech understanding in noise was better with the CI compared to testing without CI, but only at a position where the CI also improved sound localization. Our data suggest that a CI can, to a large extent, restore localization in participants with single-sided deafness. Difficulties may remain at frontal locations and on the CI side. However, speech understanding in noise improves when wearing the CI. The treatment with a CI in these participants might provide real-world benefits, such as improved orientation in traffic and speech understanding in difficult listening situations.

Noise Attenuation Effects on Speech Recognition of Cochlear Implant Users Inside Helicopters

BACKGROUND: The speech recognition levels of cochlear implant (CI) users are still incompatible with ICAO hearing requirements for civil aviation pilots testing in the noisy background condition of the helicopter cockpit. In this study, we evaluated noise attenuation effects on speech recognition in the same background condition.METHODS: The study involved the evaluation of 12 Portuguese-speaking CI users with post-lingual deafness and with a pure tone average up to 35 dB HL between 500 and 2000 Hz and up to 50 dB at 3000 Hz on at least one of the ears, and of three normal hearing pilots (controls). We performed speech recognition tests using sentences, numbers, and disyllables for all participants through the VHF radio. The assessment took place inside a helicopter with engine on, using three setups: 1) with headset without the active noise cancellation; 2) activating the noise cancellation system of the headset itself; and 3) connecting the speech processor directly to the helicopter radio system.RESULTS: The headset active noise-cancellation improved only the recognition of sentences. The direct connection system compared to the headset without anti-noise attenuation significantly improved all the recognition tests. The median for numbers was 90%, but the best score for disyllables recognition was 56%.DISCUSSION: The noise attenuation resources proposed in this study improved the CI users speech recognition when exposed to the noisy helicopter cockpit. However, speech recognition of CI users still did not meet the standards of ICAO, which requires at least 80% for understanding disyllables in the speech in noise test.Caldeira JMA, Goffi-Gomez MVS, Imamura R, Bento RF. Noise attenuation effects on speech recognition of cochlear implant users inside helicopters. Aerosp Med Hum Perform. 2021; 92(11):880-885.

Cochlear Implantation for Unilateral Hearing Loss

Pediatric cochlear implantation for unilateral hearing loss is a new application of cochlear implants with Federal Drug Administration approval for this indication in 2019. The criteria for cochlear implant candidacy include evaluation of the etiology of hearing loss, the duration of deafness, child and family motivation, and the child's comorbidities. Studies have demonstrated significant improvements in speech perception in quiet and noise, sound localization, and speech and language development after implantation. Additional research is required to determine the best candidate and device for cochlear implantation.

Comparing the Speech Perception of Cochlear Implant Users with Three Different Finnish Speech Intelligibility Tests in Noise

Background: A large number of different speech-in-noise (SIN) tests are available for testing cochlear implant (CI) recipients, but few studies have compared the different tests in the same patient population to assess how well their results correlate. Methods: A clinically representative group of 80 CI users conducted the Finnish versions of the matrix sentence test, the simplified matrix sentence test, and the digit triplet test. The results were analyzed for correlations between the different tests and for differences among the participants, including age and device modality. Results: Strong and statistically significant correlations were observed between all of the tests. No floor or ceiling effects were observed with any of the tests when using the adaptive test procedure. Age or the length of device use showed no correlation to SIN perception, but bilateral CI users showed slightly better results in comparison to unilateral or bimodal users. Conclusions: Three SIN tests that differ in length and complexity of the test material provided comparable results in a diverse CI user group.

Speech Recognition With Informational and Energetic Maskers in Patients With Single-Sided Deafness After Cochlear Implantation

Purpose The aim of the study was to assess the susceptibility to energetic and informational masking in patients with single-sided deafness (SSD) with one normal-hearing (NH) ear and a cochlear implant (CI) in the contralateral ear, understand the effect on speech recognition when spatially separating noise and speech maskers, and investigate the influence of the CI in situations with energetic and informational masking. Method Speech recognition was measured in the presence of either a modulated speech-shaped noise or one of two competing speech maskers in 11 SSD-CI listeners. The speech maskers were manipulated with respect to fundamental frequency to consider the effect of different voices. Measurements were conducted in the unaided (NH) and aided (NHCI) conditions. Spatial release from masking (SRM) was calculated for each masker type and both listening conditions (NH and NHCI) by subtracting scores of the colocated target and masker condition (S₀N₀) from the spatially separated target and masker conditions (S₀N_≠0). Results Speech recognition was highly variable depending on the type of masker. SRM occurred in the unaided (NH) and aided (NHCI) conditions when the speech masker had the same gender as the target talker. Adding the CI improved speech recognition when this speech masker was ipsilateral to the NH ear. Conclusions The amount of informational masking is substantial in SSD-CI listeners with both colocated and spatially separated target and masker signals. The contribution of SRM to better speech recognition largely depends on the masker and is considerable when no differences in voices between the target and the competing talker occur. There is only a slight improvement in speech recognition by adding the CI.

Assessment of Receptive and Expressive Language Skills Among Young Children With Prelingual Single-Sided Deafness Managed With Early Cochlear Implantation

IMPORTANCE

Pediatric single-sided deafness (SSD) can seriously affect development, causing impaired spatial hearing skills, speech-language delays, and academic underachievement. Early cochlear implantation likely improves hearing-related outcomes, but its association with language development remains unclear.

OBJECTIVE

To investigate whether early cochlear implantation is associated with language outcomes for children with prelingual SSD.

DESIGN, SETTING, AND PARTICIPANTS

The Cochlear Implant for Children and One Deaf Ear study was initiated in 2015 and recruited participants at 4 academic hospitals in Flanders, Belgium, through 2019. This cohort study included 3 groups of children aged 2 to 5 years: children with SSD and a cochlear implant, children with SSD without a cochlear implant, and a control group with normal hearing. Language and hearing skills were assessed 1 to 2 times per year until the age of 10 years. Study completion rates were high (82%). Data analysis was performed from October to December 2020.

EXPOSURE

Unilateral cochlear implant.

MAIN OUTCOMES AND MEASURES

Longitudinal vocabulary, grammar, and receptive language scores. The implanted group was hypothesized to outperform the nonimplanted group on all language tests.

RESULTS

During the recruitment period, 47 children with prelingual SSD without additional disabilities were identified at the participating hospitals. Fifteen of the 34 children with an intact auditory nerve received a cochlear implant (44%, convenience sample). Sixteen of the remaining children were enrolled in the SSD control group (50%). Data from 61 children (mean [SD] age at the time of enrollment, 2.08 [1.34] years; 26 girls [42%]) were included in the analysis: 15 children with SSD and a cochlear implant, 16 children with SSD without a cochlear implant, and 30 children with normal hearing. Children with SSD and a cochlear implant performed in line with their peers with normal hearing with regard to grammar. In contrast, children with SSD without a cochlear implant had worse grammar scores than the group with implants (-0.76; 95% CI, -0.31 to -1.21; P = .004) and the group with normal hearing (-0.53; 95% CI, -0.91 to -0.15; P = .02). The 3 groups had similar vocabulary and receptive language abilities.

CONCLUSIONS AND RELEVANCE

These findings suggest that early cochlear implantation is associated with normal grammar development in young children with prelingual SSD. Although further follow-up will reveal the long-term outcomes of the cochlear implant for other skills, the current results will help clinicians and policy makers identify the best treatment option for these children.

Spatial Release From Masking in Pediatric Cochlear Implant Recipients With Single-Sided Deafness

Purpose Children with single-sided deafness (SSD) experience difficulty understanding speech in multisource listening situations. Case reports and retrospective studies have indicated that a cochlear implant (CI) may improve masked speech recognition in children with SSD. This prospective study was conducted to determine whether providing a CI to children with SSD supports spatial release from masking (SRM), an improvement in speech recognition associated with separating the target and masker sources. Method Twenty children with at least a moderate-to-profound hearing loss in one ear and normal hearing in the contralateral ear underwent cochlear implantation. The average age of implantation was 5.5 years (range: 3.5-12.7). After 12 months of CI use, subjects completed a sentence recognition task in multitalker masker with and without the CI. The target was presented from the front, and the masker was either colocated with the target (0°) or from the side (+90° or -90°). A two-way repeated-measures analysis of variance was completed to investigate SRM with and without the CI. Results Pediatric CI recipients experienced significant SRM when the masker was directed to the normal-hearing ear or to the affected ear. Conclusions The results indicate that cochlear implantation in children with SSD supports binaural skills required for speech recognition in noise. These results are consistent with improved functional communication in multisource environments, like classrooms.

Cochlear Implantation in Adults With Single-sided Deafness: Outcomes and Device Use

OBJECTIVE

To describe our experience with adults undergoing cochlear implantation (CI) for treatment of single-sided deafness (SSD).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Fifty-three adults with SSD.

INTERVENTIONS

Unilateral CI.

MAIN OUTCOME MEASURES

Speech perception testing in quiet and noise, tinnitus suppression, and device usage from datalogs.

RESULTS

The mean age at CI was 53.2 years (SD 11.9). The mean duration of deafness was 4.0 years (SD 7.8). The most common etiology was idiopathic sudden SNHL (50%). Word recognition improved from 8.7% (SD 15) preoperatively to 61.8% (SD 20) at a mean follow-up of 3.3 years (SD 1.8) (p < 0.0001). Adaptive speech recognition testing in the "binaural with CI" condition (speech directed toward the front and noise toward the normal hearing ear) revealed a significant improvement by 2.6-dB SNR compared to the preoperative unaided condition (p = 0.0002) and by 3.6-dB SNR compared to when a device to route sound to the contralateral side was used (p < 0.0001). Tinnitus suppression was reported to be complete in 23 patients (43%) and improved in 20 patients (38%) while the device was on. The addition of the CI did not lead to a decrement in hearing performance in any spatial configuration. Device usage averaged 8.7 (SD 3.7) hours/day.

CONCLUSIONS

Cochlear implantation in adult SSD patients can suppress tinnitus and achieve speech perception outcomes comparable with CI in conventional candidates. Modest improvements in spatial hearing were also observed and primarily attributable to the head shadow effect. Careful patient selection and counseling regarding potential benefits are important to optimize outcomes.

Audiological benefits and performance improvements of Baha® attract implantation in patients with unilateral hearing loss

OBJECTIVES

To evaluate the overall functional and audiological benefits in unilateral hearing loss, as well as performance improvements with Cochlear™ Baha® Attract System with Baha® 5 sound processor.

METHODS

We performed a prospective study. Fourteen consecutive adult patients with unilateral hearing loss who were audiologically eligible for Baha® Attract were included in this study. All patients were followed-up, and a series of tests were performed in the sound field before surgery, one, two, three, and 6 months after surgery.

RESULTS

Patients were categorized based on their hearing impairment type and severity. Ten patients had conductive hearing loss (CHL), or mixed hearing loss (MHL), and four patients had sensorineural hearing loss (SNHL). The hearing threshold in the sound field aided with Baha® Attract was similar to the preoperative bone conduction hearing threshold of the better ear. The results of the speech audiometry improved post-operatively, but they did not match that of the better ear before surgery. The overall score of the hearing-in-noise test was gradually improved from one month to 6 months after surgery. The results of the sound localization test for SNHL patients were not as good as those for CHL or MHL. All the questionnaires demonstrated additional benefits that implied performance improvements.

CONCLUSIONS

The Baha® Attract provides enough auditory benefits and performance improvements for hearing impaired patients, though there are different benefits according to the type of hearing loss. Clinicians need to counsel the unilateral hearing loss patients for Baha® Attract System carefully, according to their type of hearing loss.

Systematic review of outcome domains and instruments used in designs of clinical trials for interventions that seek to restore bilateral and binaural hearing in adults with unilateral severe to profound sensorineural hearing loss ('single-sided deafness')

BACKGROUND

This systematic review aimed to identify, compare and contrast outcome domains and outcome instruments reported in studies investigating interventions that seek to restore bilateral (two-sided) and/or binaural (both ears) hearing in adults with single-sided deafness (SSD). Findings can inform the development of evidence-based guidance to facilitate design decisions for confirmatory trials.

METHODS

Records were identified by searching MEDLINE, EMBASE, PubMed, CINAHL, ClinicalTrials.gov, ISRCTN, CENTRAL, WHO ICTRP and the NIHR UK clinical trials gateway. The search included records published from 1946 to March 2020. Included studies were those as follows: (a) recruiting adults aged 18 years or older diagnosed with SSD of average threshold severity worse than 70 dB HL in the worse-hearing ear and normal (or near-normal) hearing in the better-hearing ear, (b) evaluating interventions to restore bilateral and/or binaural hearing and (c) enrolling those adults in a controlled trial, before-and-after study or cross-over study. Studies that fell just short of the participant eligibility criteria were included in a separate sensitivity analysis.

RESULTS

Ninety-six studies were included (72 full inclusion, 24 sensitivity analysis). For fully included studies, 37 exclusively evaluated interventions to re-establish bilateral hearing and 29 exclusively evaluated interventions to restore binaural hearing. Overall, 520 outcome domains were identified (350 primary and 170 secondary). Speech-related outcome domains were the most common (74% of studies), followed by spatial-related domains (60% of studies). A total of 344 unique outcome instruments were reported. Speech-related outcome domains were measured by 73 different instruments and spatial-related domains by 43 different instruments. There was considerable variability in duration of follow-up, ranging from acute (baseline) testing to 10 years after the intervention. The sensitivity analysis identified no additional outcome domains.

CONCLUSIONS

This review identified large variability in the reporting of outcome domains and instruments in studies evaluating the therapeutic benefits and harms of SSD interventions. Reports frequently omitted information on what domains the study intended to assess, and on what instruments were used to measure which domains.

TRIAL REGISTRATION

The systematic review protocol is registered on PROSPERO (International Prospective Register of Systematic Reviews): Registration Number CRD42018084274 . Registered on 13 March 2018, last revised on 7th of May 2019.

The impact of cochlear implant microphone settings on the binaural hearing of experienced cochlear implant users with single-sided deafness

OBJECTIVE

Cochlear implantation has become a well-accepted treatment option for people with single-sided deafness (SSD) and has become a clinical standard in many countries. A cochlear implant (CI) is the only device which restores binaural hearing. The effect of microphone directionality (MD) settings has been investigated in other CI indication groups, but its impact on speech perception in noise has not been established in CI users with SSD. The focus of this investigation was, therefore, to assess binaural hearing effects using different MD settings in CI users with SSD.

METHODS

Twenty-nine experienced CI users with SSD were recruited to determine speech reception thresholds with varying target and noise sources to define binaural effects (head shadow, squelch, summation, and spatial release from masking), sound localization, and sound quality using the SSQ12 and HISQUI₁₉ questionnaires. Outcome measures included the MD settings "natural", "adaptive", and "omnidirectional".

RESULTS

The 29 participants involved in the study were divided into two groups: 11 SONNET users and 18 OPUS 2/RONDO users. In both groups, a significant head shadow effect of 7.4-9.2 dB was achieved with the CI. The MD setting "adaptive" provided a significant head shadow effect of 9.2 dB, a squelch effect of 0.9 dB, and spatial release from masking of 7.6 dB in the SONNET group. No significant summation effect could be determined in either group with CI. Outcomes with the omnidirectional setting were not significantly different between groups. For both groups, localization improved significantly when the CI was activated and was best when the omnidirectional setting was used. The groups' sound quality scores did not significantly differ.

CONCLUSIONS

Adaptive directional microphone settings improve speech perception and binaural hearing abilities in CI users with SSD. Binaural effect measures are valuable to quantify the benefit of CI use, especially in this indication group.

Development of cortical auditory responses to speech in noise in unilaterally deaf adults following cochlear implantation

Background

For patients with single-sided deafness (SSD), restoration of binaural function via cochlear implant (CI) has been shown to improve speech understanding in noise. The objective of this study was to investigate changes in behavioral performance and cortical auditory responses following cochlear implantation.

Design

Prospective longitudinal study.

Setting

Tertiary referral center.

Methods

Six adults with SSD were tested before and 12 months post-activation of the CI. Six normal hearing (NH) participants served as experimental controls. Speech understanding in noise was evaluated for various spatial conditions. Cortical auditory evoked potentials were recorded with /ba/ stimuli in quiet and in noise. Global field power and responses at Cz were analyzed.

Results

Speech understanding in noise significantly improved with the CI when speech was presented to the CI ear and noise to the normal ear (p<0.05), but remained poorer than that of NH controls (p<0.05). N1 peak amplitude measure in noise significantly increased after CI activation (p<0.05), but remained lower than that of NH controls (p<0.05) at 12 months. After 12 months of CI experience, cortical responses in noise became more comparable between groups.

Conclusion

Binaural restoration in SSD patients via cochlear implantation improved speech performance noise and cortical responses. While behavioral performance and cortical auditory responses improved, SSD-CI outcomes remained poorer than that of NH controls in most cases, suggesting only partial restoration of binaural hearing.

Assessment of Angular Insertion-Depth of Bilateral Cochlear Implants Using Plain X-ray Scans

OBJECTIVE

To evaluate in cochlear implant patients, the feasibility and reliability of angular depth of insertion (aDOI) measurements using plain x-ray scans.

STUDY DESIGN

Retrospective study where three observers independently evaluated and compared intraoperative anterior-posterior and oblique x-ray scans.

SETTING

A tertiary pediatric medical center.

PATIENTS

Included were 50 children (100 ears) who underwent bilateral simultaneous cochlear implantation during 2008 to 2015.

MAIN OUTCOME MEASURES

Inter-rater agreement of aDOI measured in plain x-ray scans; effect of head position on measured aDOI; and symmetry of aDOI between patients' ears in bilateral simultaneous cochlear implantations.

RESULTS

Differences in the average aDOI measurements among the three observers ranged between 2 and 7 degrees. There was high inter-rater agreement (R = 0.99, p < 0.01) among all observers, and strong correlations between each pair of observers (0.92-0.99). Head rotation of 45 degrees (between the two views) resulted in a median difference in aDOI of 14 degrees, with excellent correlation among the observers. The rate of asymmetry was high, with a median difference of 39 degrees and up to 220 degrees between ears.

CONCLUSIONS

Assessment of aDOI using intraoperative plain x-rays is efficient and reliable. The effect of head positioning on measurement is small. Further studies are needed to evaluate the effect of aDOI and insertion symmetry on functional outcomes.

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.

Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study: protocol for an international consensus on outcome measures for single sided deafness interventions using a modified Delphi survey

BACKGROUND

Single-sided deafness (SSD) describes the presence of a unilateral severe to profound sensorineural hearing loss. SSD disrupts spatial hearing and understanding speech in background noise. It has functional, psychological and social consequences. Potential options for rehabilitation include hearing aids and auditory implants. Benefits and harms of these interventions are documented inconsistently in the literature, using a variety of outcomes ranging from tests of speech perception to quality of life questionnaires. It is therefore difficult to compare interventions when rehabilitating SSD. The Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study is an international initiative that aims to develop a minimum set of core outcomes for use in future trials of SSD interventions.

METHODS/DESIGN

The CROSSSD study adopts an international two-round online modified Delphi survey followed by a stakeholder consensus meeting to identify a patient-centred core outcome domain set for SSD based on what is considered critical and important for assessing whether an intervention for SSD has worked.

DISCUSSION

The resulting core outcome domain set will act as a minimum standard for reporting in future clinical trials and could have further applications in guiding the use of outcome measures in clinical practice. Standardisation will facilitate comparison of research findings.

Usefulness of cochlear implantation in children with single sided deafness

OBJECTIVES

Children with single sided deafness (SSD) show a poorer performance at school, which is attributable to reduced speech discrimination in noise, to reduced localization ability, and to a decreased power of concentration due to faster hearing exhaustion. Therefore, it is important to provide children with SSD with adequate hearing amplification to restore binaural hearing. This can only be achieved by provision with a cochlear implant (CI). But these treatment option in children with SSD is still under discussion. The aim of the present study is to evaluate audiological and clinical results in children with SSD following cochlear implantation. A special focus was placed on the duration of deafness before implantation and on the frequency of CI-use in everyday life.

METHODS

Seven children with SSD of different etiologies who were provided with a CI between 3 and 16 years of age were evaluated. Every child underwent multiple audiological tests before and after cochlear implantation. After cochlear implantation speech recognition tests in noise using the HSM (Hochmair, Schulz and Moser 1997) test and localization tests were performed. Furthermore, the frequency of implant use was evaluated.

RESULTS

Speech recognition in noise with CI compared to the unaided condition significantly improved in all children in different settings. Improvement of the localization ability measured by the root mean square error (RMSE) was shown in all children. All children are very satisfied with the decision to have undergone cochlear implantation and are all full-time users.

CONCLUSIONS

Cochlear implantation benefits speech recognition in noise and sound localization ability in children with SSD at different ages. All implanted children are full-time users regardless of age or duration of deafness before implantation.

Sound Localization in Real-Time Vocoded Cochlear-Implant Simulations With Normal-Hearing Listeners

Bilateral cochlear-implant (CI) users and single-sided deaf listeners with a CI are less effective at localizing sounds than normal-hearing (NH) listeners. This performance gap is due to the degradation of binaural and monaural sound localization cues, caused by a combination of device-related and patient-related issues. In this study, we targeted the device-related issues by measuring sound localization performance of 11 NH listeners, listening to free-field stimuli processed by a real-time CI vocoder. The use of a real-time vocoder is a new approach, which enables testing in a free-field environment. For the NH listening condition, all listeners accurately and precisely localized sounds according to a linear stimulus–response relationship with an optimal gain and a minimal bias both in the azimuth and in the elevation directions. In contrast, when listening with bilateral real-time vocoders, listeners tended to orient either to the left or to the right in azimuth and were unable to determine sound source elevation. When listening with an NH ear and a unilateral vocoder, localization was impoverished on the vocoder side but improved toward the NH side. Localization performance was also reflected by systematic variations in reaction times across listening conditions. We conclude that perturbation of interaural temporal cues, reduction of interaural level cues, and removal of spectral pinna cues by the vocoder impairs sound localization. Listeners seem to ignore cues that were made unreliable by the vocoder, leading to acute reweighting of available localization cues. We discuss how current CI processors prevent CI users from localizing sounds in everyday environments.

Effect of Tinnitus and Duration of Deafness on Sound Localization and Speech Recognition in Noise in Patients With Single-Sided Deafness

Patients with single-sided deafness (SSD) often experience poor sound localization, reduced speech understanding in noise, reduced quality of life, and tinnitus. The present study aims to evaluate effects of tinnitus and duration of deafness on sound localization and speech recognition in noise by SSD subjects. Sound localization and speech recognition in noise were measured in 26 SSD and 10 normal-hearing (NH) subjects. Speech was always presented directly in front of the listener. Noise was presented to the deaf ear, in front of the listener, or to the better hearing ear. Tinnitus severity was measured using visual analog scale and Tinnitus Handicap Inventory. Relative to NH subjects, SSD subjects had significant deficits in sound localization and speech recognition in all listening conditions (p < .001). For SSD subjects, speech recognition in noise was correlated with mean hearing thresholds in the better hearing ear (p < .001) but not in the deaf ear. SSD subjects with tinnitus performed poorer in sound localization and speech recognition in noise than those without tinnitus. Shorter duration of deafness was associated with greater tinnitus and sound localization difficulty. Tinnitus visual analog scale and Tinnitus Handicap Inventory were highly correlated; the degree of tinnitus was negatively correlated with sound localization and speech recognition in noise. Those experiencing noticeable tinnitus may benefit more from cochlear implantation than those without; subjective tinnitus reduction may be correlated with improved sound localization and speech recognition in noise. Subjects with longer duration of deafness demonstrated better sound localization, suggesting long-term compensation for loss of binaural cues.

Effects of Cochlear Implantation on Binaural Hearing in Adults With Unilateral Hearing Loss

A FDA clinical trial was carried out to evaluate the potential benefit of cochlear implant (CI) use for adults with unilateral moderate-to-profound sensorineural hearing loss. Subjects were 20 adults with moderate-to-profound unilateral sensorineural hearing loss and normal or near-normal hearing on the other side. A MED-EL standard electrode was implanted in the impaired ear. Outcome measures included: (a) sound localization on the horizontal plane (11 positions, -90° to 90°), (b) word recognition in quiet with the CI alone, and (c) masked sentence recognition with the target at 0° and the masker at -90°, 0°, or 90°. This battery was completed preoperatively and at 1, 3, 6, 9, and 12 months after CI activation. Normative data were also collected for 20 age-matched control subjects with normal or near-normal hearing bilaterally. The CI improved localization accuracy and reduced side bias. Word recognition with the CI alone was similar to performance of traditional CI recipients. The CI improved masked sentence recognition when the masker was presented from the front or from the side of normal or near-normal hearing. The binaural benefits observed with the CI increased between the 1- and 3-month intervals but appeared stable thereafter. In contrast to previous reports on localization and speech perception in patients with unilateral sensorineural hearing loss, CI benefits were consistently observed across individual subjects, and performance was at asymptote by the 3-month test interval. Cochlear implant settings, consistent CI use, and short duration of deafness could play a role in this result.

Unilateral congenital hearing loss in children: Challenges and potentials

The estimated incidence of sensorineural hearing impairment (>40 dB HL) at birth is 1.86 per 1000 newborns in developed countries and 30-40% of these are unilateral. Profound sensorineural unilateral hearing impairment or single sided deafness (SSD) can be treated with a cochlear implant. However, this treatment is costly and invasive and unnecessary in the eyes of many. Very young children with SSD often do not exhibit language and cognitive delays and it is hard to imagine that neurocognitive skills will present difficulties with one good ear. In the current paper we review the most recent evidence on the consequences of unilateral hearing impairment for auditory and neurocognitive factors. While data of both adults and children are discussed, we focus on developmental factors, congenital deafness and a window of opportunity for intervention. We discuss which etiologies qualify for a cochlear implant and present our multi-center prospective study on cochlear implants in infants with one deaf ear. The large, state-of-the art body of research allows for evidence-based decisions regarding management of unilateral hearing loss in children.

Bilateral cochlear implantation is regarded as very beneficial: results from a worldwide survey by online questionnaire

PURPOSE

Bilateral cochlear implant (CI) provision is now widely regarded as the most beneficial hearing intervention for acceptable candidates. This study sought to determine if a number of well-regarded hearing professionals at highly reputable clinics shared similar practices and beliefs regarding bilateral CI provision, use, and rehabilitation in children and adults.

METHODS

An 11-question online questionnaire was created and distributed to all 27 clinics in the HEARRING group. Questions 1-5 asked for facts; questions 6-11 asked for opinions.

RESULTS

20 completed questionnaires were returned. All 20 respondents reported that their clinics perform bilateral cochlear implantation in children; 18 do so in adults. Regarding the fact-based questions, bilateral CI provision is more commonly performed and more likely to be reimbursed in children than in adults. Children are also much more likely to be implanted simultaneously than are adults. Regarding the opinion-based questions, respondents gave broadly similar answers. Communication between the CIs and speech coding strategies specifically developed for bilateral CI users were regarded as the two future technologies that would most enhance the benefit of bilateral CI use.

CONCLUSIONS

Most clinics in the HEARRING group are very familiar with bilateral CI provision and hold similar opinions on its results and benefits. Hopefully the results described herein will lead to a greater acceptance and regular reimbursement of bilateral CI provision, especially in adults.

Improved interaural timing of acoustic nerve stimulation affects sound localization in single-sided deaf cochlear implant users

The main impairment associated with single-sided deafness (SSD) is the loss of binaural hearing. Currently, the most effective treatment to compensate for this deficit is to supply patients suffering from SSD with a cochlear implant (CI) in the deaf ear. With this approach binaural hearing abilities can be restored to a certain extent, which is expressed in an improvement in such patients with regard to sound source localization and speech comprehension in noise after receipt of a CI. However, binaural performance of these listeners does not reach the level of normal-hearing listeners. One of the reasons for this might be that the electrical stimulation via CI and the physiological stimulation via the intact ear are not synchronized: the CI transmits the information to the auditory nerve with different timing than does the intact inner ear. As a result, there is a timing mismatch of the information transfer between the left and the right side, which may account for the limited binaural performance. The effective mismatch in timing depends on the CI system because of different stimulation strategies implemented in devices from different manufacturers. For the particular CI device used in this study (MED-EL Mi1000/Mi1200) electrical stimulation led to faster activation of the auditory nerve than natural for a wide frequency range. In particular, electrical stimulation was about 1 to up to 2 ms ahead of time for frequencies above 1.5 kHz. Hence, it was hypothesized that information transfer between the left and the right ear can be tuned by delaying the CI signal. The goal of the present study was to investigate whether such a delay in the CI signal affects binaural performance of CI users with SSD. For this purpose, sound source localization and speech perception in noise were tested in a sample of 12 CI users with SSD (mean age 51 ± 12 years). The tests were performed for four different delay times of the CI signal applied spontaneously (0.5, 1, 2 and 4 ms) and for the base line condition "no delay" in the CI signal (i.e. everyday use). It was found that delaying the signal had a significant impact on sound source localization. Speech perception in noise was affected, but less pronounced than was sound localization. Regarding sound source localization, a signal delay of 1 ms applied to this particular CI device produced the best performance in our patients. It is concluded that improving the synchronisation between the CI-transferred signal and the naturally transferred signal could increase binaural hearing performance in CI users with SSD.

Dietrich M, Dorman MF. Speech Understanding in Noise for Adults With Cochlear Implants: Effects of Hearing Configuration, Source Location Certainty, and Head Movement

PURPOSE

The primary purpose of this study was to assess speech understanding in quiet and in diffuse noise for adult cochlear implant (CI) recipients utilizing bimodal hearing or bilateral CIs. Our primary hypothesis was that bilateral CI recipients would demonstrate less effect of source azimuth in the bilateral CI condition due to symmetric interaural head shadow.

METHOD

Sentence recognition was assessed for adult bilateral (n = 25) CI users and bimodal listeners (n = 12) in three conditions: (1) source location certainty regarding fixed target azimuth, (2) source location uncertainty regarding roving target azimuth, and (3) Condition 2 repeated, allowing listeners to turn their heads, as needed.

RESULTS

(a) Bilateral CI users exhibited relatively similar performance regardless of source azimuth in the bilateral CI condition; (b) bimodal listeners exhibited higher performance for speech directed to the better hearing ear even in the bimodal condition; (c) the unilateral, better ear condition yielded higher performance for speech presented to the better ear versus speech to the front or to the poorer ear; (d) source location certainty did not affect speech understanding performance; and (e) head turns did not improve performance. The results confirmed our hypothesis that bilateral CI users exhibited less effect of source azimuth than bimodal listeners. That is, they exhibited similar performance for speech recognition irrespective of source azimuth, whereas bimodal listeners exhibited significantly poorer performance with speech originating from the poorer hearing ear (typically the nonimplanted ear).

CONCLUSIONS

Bilateral CI users overcame ear and source location effects observed for the bimodal listeners. Bilateral CI users have access to head shadow on both sides, whereas bimodal listeners generally have interaural asymmetry in both speech understanding and audible bandwidth limiting the head shadow benefit obtained from the poorer ear (generally the nonimplanted ear). In summary, we found that, in conditions with source location uncertainty and increased ecological validity, bilateral CI performance was superior to bimodal listening.

Restoration of spatial hearing in adult cochlear implant users with single-sided deafness

In recent years, cochlear implants (CIs) have been provided in growing numbers to people with not only bilateral deafness but also to people with unilateral hearing loss, at times in order to alleviate tinnitus. This study presents audiological data from 15 adult participants (ages 48 ± 12 years) with single sided deafness. Results are presented from 9/15 adults, who received a CI (SSD-CI) in the deaf ear and were tested in Acoustic or Acoustic + CI hearing modes, and 6/15 adults who are planning to receive a CI, and were tested in the unilateral condition only. Testing included (1) audiometric measures of threshold, (2) speech understanding for CNC words and AzBIO sentences, (3) tinnitus handicap inventory, (4) sound localization with stationary sound sources, and (5) perceived auditory motion. Results showed that when listening to sentences in quiet, performance was excellent in the Acoustic and Acoustic + CI conditions. In noise, performance was similar between Acoustic and Acoustic + CI conditions in 4/6 participants tested, and slightly worse in the Acoustic + CI in 2/6 participants. In some cases, the CI provided reduced tinnitus handicap scores. When testing sound localization ability, the Acoustic + CI condition resulted in improved sound localization RMS error of 29.2° (SD: ±6.7°) compared to 56.6° (SD: ±16.5°) in the Acoustic-only condition. Preliminary results suggest that the perception of motion direction, whereby subjects are required to process and compare directional cues across multiple locations, is impaired when compared with that of normal hearing subjects.

Unilateral Hearing Loss: Understanding Speech Recognition and Localization Variability-Implications for Cochlear Implant Candidacy

OBJECTIVES

At a minimum, unilateral hearing loss (UHL) impairs sound localization ability and understanding speech in noisy environments, particularly if the loss is severe to profound. Accompanying the numerous negative consequences of UHL is considerable unexplained individual variability in the magnitude of its effects. Identification of covariables that affect outcome and contribute to variability in UHLs could augment counseling, treatment options, and rehabilitation. Cochlear implantation as a treatment for UHL is on the rise yet little is known about factors that could impact performance or whether there is a group at risk for poor cochlear implant outcomes when hearing is near-normal in one ear. The overall goal of our research is to investigate the range and source of variability in speech recognition in noise and localization among individuals with severe to profound UHL and thereby help determine factors relevant to decisions regarding cochlear implantation in this population.

DESIGN

The present study evaluated adults with severe to profound UHL and adults with bilateral normal hearing. Measures included adaptive sentence understanding in diffuse restaurant noise, localization, roving-source speech recognition (words from 1 of 15 speakers in a 140° arc), and an adaptive speech-reception threshold psychoacoustic task with varied noise types and noise-source locations. There were three age-sex-matched groups: UHL (severe to profound hearing loss in one ear and normal hearing in the contralateral ear), normal hearing listening bilaterally, and normal hearing listening unilaterally.

RESULTS

Although the normal-hearing-bilateral group scored significantly better and had less performance variability than UHLs on all measures, some UHL participants scored within the range of the normal-hearing-bilateral group on all measures. The normal-hearing participants listening unilaterally had better monosyllabic word understanding than UHLs for words presented on the blocked/deaf side but not the open/hearing side. In contrast, UHLs localized better than the normal-hearing unilateral listeners for stimuli on the open/hearing side but not the blocked/deaf side. This suggests that UHLs had learned strategies for improved localization on the side of the intact ear. The UHL and unilateral normal-hearing participant groups were not significantly different for speech in noise measures. UHL participants with childhood rather than recent hearing loss onset localized significantly better; however, these two groups did not differ for speech recognition in noise. Age at onset in UHL adults appears to affect localization ability differently than understanding speech in noise. Hearing thresholds were significantly correlated with speech recognition for UHL participants but not the other two groups.

CONCLUSIONS

Auditory abilities of UHLs varied widely and could be explained only in part by hearing threshold levels. Age at onset and length of hearing loss influenced performance on some, but not all measures. Results support the need for a revised and diverse set of clinical measures, including sound localization, understanding speech in varied environments, and careful consideration of functional abilities as individuals with severe to profound UHL are being considered potential cochlear implant candidates.