Transitioning from bimodal to bilateral cochlear implant listening: speech recognition and localization in four individuals

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

OBJECTIVE

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

DESIGN

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

STUDY SAMPLES

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

RESULTS

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

CONCLUSION

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

CROS or hearing aid? Selecting the ideal solution for unilateral CI patients with limited aidable hearing in the contralateral ear

A hearing aid or a contralateral routing of signal device are options for unilateral cochlear implant listeners with limited hearing in the unimplanted ear; however, it is uncertain which device provides greater benefit beyond unilateral listening alone. Eighteen unilateral cochlear implant listeners participated in this prospective, within-participants, repeated measures study. Participants were tested with the cochlear implant alone, cochlear implant + hearing aid, and cochlear implant + contralateral routing of signal device configurations with a one-month take-home period between each in-person visit. Audiograms, speech perception in noise, and lateralization were evaluated. Subjective feedback was obtained via questionnaires. Marked improvement in speech in noise and non-implanted ear lateralization accuracy were observed with the addition of a contralateral hearing aid. There were no significant differences in speech recognition between listening configurations. However, the chronic device use questionnaires and the final device selection showed a clear preference for the hearing aid in spatial awareness and communication domains. Individuals with limited hearing in their unimplanted ears demonstrate significant improvement with the addition of a contralateral device. Subjective questionnaires somewhat contrast with clinic-based outcome measures, highlighting the delicate decision-making process involved in clinically advising one device or another to maximize communication benefits.

Speech Perception and Sound Localization Skills in Inner Ear Malformations: Children With Incomplete Partition Type-II

OBJECTIVE

The present study aimed to evaluate binaural auditory skills in bimodal and bilateral pediatric cochlear implant (CI) users with incomplete partition type-II (IP-II) and to reveal the effect of IP-II on performance by comparing the results to pediatric CI users with normal cochlear morphology.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary referral center.

METHODS

Forty-one CI users (mean age 8.8 ± 1.9) were grouped as bimodal (BIM-IP) and bilateral (BIL-IP) users with IP-II; bimodal (BIM-N) and bilateral (BIL-N) users with normal cochlear anatomy. Speech perception in noise and sound localization skills were compared under 2 conditions; binaural (bilateral or bimodal) and monaural (first CI alone).

RESULTS

BIM-IP and BIL-IP showed no performance difference in binaural tasks. The BIM-N group showed remarkably poor performance in comparison to the groups of BIL-IP (p = .007), BIM-IP (p < .001), and BIL-N (p = .004) in terms of speech-in-noise skills. In sound localization abilities, similar significant differences were found between the group of BIM-N and the groups of BIL-IP (p = .001), BIM-IP (p < .001), and BIL-N (p = .004). All groups showed statistically significant improvements in binaural condition on both tasks (p < .05).

CONCLUSION

We revealed that bilateral and bimodal pediatric CI users with IP-II benefitted from implantation as much as bilateral users with normal anatomy. Differences in residual hearing between groups may explain the poor performance of bimodal users with normal cochlear morphology. To the best of our knowledge, it is the first study to unveil binaural performance characteristics in children diagnosed with a specific inner ear malformation subgroup.

The Effect of Sound Localization on Auditory-Only and Audiovisual Speech Recognition in a Simulated Multitalker Environment

Information regarding sound-source spatial location provides several speech-perception benefits, including auditory spatial cues for perceptual talker separation and localization cues to face the talker to obtain visual speech information. These benefits have typically been examined separately. A real-time processing algorithm for sound-localization degradation (LocDeg) was used to investigate how spatial-hearing benefits interact in a multitalker environment. Normal-hearing adults performed auditory-only and auditory-visual sentence recognition with target speech and maskers presented from loudspeakers at -90°, -36°, 36°, or 90° azimuths. For auditory-visual conditions, one target and three masking talker videos (always spatially separated) were rendered virtually in rectangular windows at these locations on a head-mounted display. Auditory-only conditions presented blank windows at these locations. Auditory target speech (always spatially aligned with the target video) was presented in co-located speech-shaped noise (experiment 1) or with three co-located or spatially separated auditory interfering talkers corresponding to the masker videos (experiment 2). In the co-located conditions, the LocDeg algorithm did not affect auditory-only performance but reduced target orientation accuracy, reducing auditory-visual benefit. In the multitalker environment, two spatial-hearing benefits were observed: perceptually separating competing speech based on auditory spatial differences and orienting to the target talker to obtain visual speech cues. These two benefits were additive, and both were diminished by the LocDeg algorithm. Although visual cues always improved performance when the target was accurately localized, there was no strong evidence that they provided additional assistance in perceptually separating co-located competing speech. These results highlight the importance of sound localization in everyday communication.

Guidelines for Best Practice in the Audiological Management of Adults Using Bimodal Hearing Configurations

Clinics are treating a growing number of patients with greater amounts of residual hearing. These patients often benefit from a bimodal hearing configuration in which acoustic input from a hearing aid on 1 ear is combined with electrical stimulation from a cochlear implant on the other ear. The current guidelines aim to review the literature and provide best practice recommendations for the evaluation and treatment of individuals with bilateral sensorineural hearing loss who may benefit from bimodal hearing configurations. Specifically, the guidelines review: benefits of bimodal listening, preoperative and postoperative cochlear implant evaluation and programming, bimodal hearing aid fitting, contralateral routing of signal considerations, bimodal treatment for tinnitus, and aural rehabilitation recommendations.

Relationships Between Health-Related Quality of Life and Speech Perception in Bimodal and Bilateral Cochlear Implant Users

Purpose

Previous studies examining the relationship between health-related quality of life (HRQoL) and speech perception ability in cochlear implant (CI) users have yielded variable results, due to a range of factors, such as a variety of different HRQoL questionnaires and CI speech testing materials in addition to CI configuration. In order to decrease inherent variability and better understand the relationship between these measures in CI users, we administered a commonly used clinical CI speech testing battery as well as two popular HRQoL questionnaires in bimodal and bilateral CI users.

Methods

The Glasgow Benefit Inventory (GBI), a modified five-factor version of the GBI (GBI-5F), and the Nijmegen Cochlear Implant Questionnaire (NCIQ) were administered to 25 CI users (17 bimodal and 8 bilateral). Speech perception abilities were measured with the AzBio sentence test in several conditions (e.g., quiet and noise, binaural, and first-ear CI only).

Results

Higher performance scores on the GBI general subscore were related to greater binaural speech perception ability in noise. There were no other relationships between the GBI or NCIQ and speech perception ability under any condition. Scores on many of the GBI-5F factors were substantially skewed and asymmetrical; therefore, correlational analyses could not be applied. Across all participants, binaural speech perception scores were greater than first-ear CI only scores.

Conclusion

The GBI general subscore was related to binaural speech perception, which is considered the everyday listening condition of bimodal and bilateral CI users, in noise; while the more CI-specific NCIQ did not relate to speech perception ability in any listening condition. Future research exploring the relationships between the GBI, GBI-5F, and NCIQ considering bimodal and bilateral CI configurations separately is warranted.

Factors That Influence Second-side Cochlear Implant Speech Recognition Outcomes

OBJECTIVE

Assess relationships between patient, hearing, and cochlear implant (CI)-related factors and second-side CI speech recognition outcomes in adults who are bilaterally implanted.

STUDY DESIGN

Retrospective review of a prospectively maintained CI database.

SETTING

Tertiary academic center.

PATIENTS

One hundred two adults receiving bilateral sequential or simultaneous CIs.

OUTCOME MEASURES

Postimplantation consonant-nucleus-consonant (CNC) word and AzBio sentence scores at ≥12 months.

RESULTS

Of patient, hearing and CI-specific, factors examined only postimplantation speech recognition scores of the first CI were independently associated with speech recognition performance of the second CI on multivariable regression analysis (CNC: ß = 0.471[0.298, 0.644]; AzBio: ß = 0.602[0.417, 0.769]). First-side postoperative CNC scores explained 24.3% of variation in second CI postoperative CNC scores, while change in first CI AzBio scores explained 40.3% of variation in second CI AzBio scores. Based on established 95% confidence intervals, 75.2% (CNC) and 65.9% (AzBio) of patients score equivalent or better with their second CI compared to first CI performance. Age at implantation, duration of hearing loss, receiving simultaneous versus sequential CIs, and preoperative residual hearing (measured by pure-tone average and aided speech recognition scores) were not associated with 12 month speech recognition scores at 12 months.

CONCLUSIONS

The degree of improvement in speech recognition from first CI may predict speech recognition with a second CI. This provides preliminary evidence-based expectations for patients considering a second CI. Counseling should be guarded given the remaining unexplained variability in outcomes. Nonetheless, these data may assist decision making when considering a second CI versus continued use of a hearing aid for an unimplanted ear.

LEVEL OF EVIDENCE

III.

Bilateral Cochlear Implants or Bimodal Hearing for Children with Bilateral Sensorineural Hearing Loss

Purpose of review

This review describes speech perception and language outcomes for children using bimodal hearing (cochlear implant (CI) plus contralateral hearing aid) as compared to children with bilateral CIs and contrasts said findings with the adult literature. There is a lack of clinical evidence driving recommendations for bimodal versus bilateral CI candidacy and as such, clinicians are often unsure about when to recommend a second CI for children with residual acoustic hearing. Thus the goal of this review is to identify scientific information that may influence clinical decision making for pediatric CI candidates with residual acoustic hearing.

Recent findings

Bilateral CIs are considered standard of care for children with bilateral severe-to-profound sensorineural hearing loss. For children with aidable acoustic hearing-even in just the low frequencies-an early period of bimodal stimulation has been associated with significantly better speech perception, vocabulary, and language development. HA audibility, however, is generally poorer than that offered by a CI resulting in interaural asymmetry in speech perception, head shadow, as well as brainstem and cortical activity and development. Thus there is a need to optimize "two-eared" hearing while maximizing a child's potential with respect to hearing, speech, and language while ensuring that we limit asymmetrically driven auditory neuroplasticity. A recent large study of bimodal and bilateral CI users suggested that a period of bimodal stimulation was only beneficial for children with a better-ear pure tone average (PTA) ≤ 73 dB HL. This 73-dB-HL cutoff applied even to children who ultimately received bilateral CIs.

Summary

Though we do not yet have definitive guidelines for determining bimodal versus bilateral CI candidacy, there is increasing evidence that 1) bilateral CIs yield superior outcomes for children with bilateral severe-to-profound hearing loss and, 2) an early period of bimodal stimulation is beneficial for speech perception and language development, but only for children with better-ear PTA ≤ 73 dB HL. For children with residual acoustic hearing, even in just the low-frequency range, rapid sequential bilateral cochlear implantation following a trial period with bimodal stimulation will yield best outcomes for auditory, language, and academic development. Of course, there is also an increasing prevalence of cochlear implantation with acoustic hearing preservation allowing for combined electric and acoustic stimulation even following bilateral implantation.

Are There Real-world Benefits to Bimodal Listening?

OBJECTIVE

To assess the benefits of bimodal listening (i.e., addition of contralateral hearing aid) for cochlear implant (CI) users on real-world tasks involving high-talker variability speech materials, environmental sounds, and self-reported quality of life (quality of hearing) in listeners' own best-aided conditions.

STUDY DESIGN

Cross-sectional study between groups.

SETTING

Outpatient hearing clinic.

PATIENTS

Fifty experienced adult CI users divided into groups based on normal daily listening conditions (i.e., best-aided conditions): unilateral CI (CI), unilateral CI with contralateral HA (bimodal listening; CIHA), or bilateral CI (CICI).

INTERVENTION

Task-specific measures of speech recognition with low (Harvard Standard Sentences) and high (Perceptually Robust English Sentence Test Open-set corpus) talker variability, environmental sound recognition (Familiar Environmental Sounds Test-Identification), and hearing-related quality of life (Nijmegen Cochlear Implant Questionnaire).

MAIN OUTCOME MEASURES

Test group differences among CI, CIHA, and CICI conditions.

RESULTS

No group effect was observed for speech recognition with low or high-talker variability, or hearing-related quality of life. Bimodal listeners demonstrated a benefit in environmental sound recognition compared with unilateral CI listeners, with a trend of greater benefit than the bilateral CI group. There was also a visual trend for benefit on high-talker variability speech recognition.

CONCLUSIONS

Findings provide evidence that bimodal listeners demonstrate stronger environmental sound recognition compared with unilateral CI listeners, and support the idea that there are additional advantages to bimodal listening after implantation other than speech recognition measures, which are at risk of being lost if considering bilateral implantation.

Association of Demographic and Hearing-Related Factors With Cochlear Implant-Related Quality of Life

Importance

Only limited evidence is available describing the contribution of patient-related factors to quality of life in adults with cochlear implants.

Objective

Assess the association between demographic, hearing-related, and cochlear implant-related factors and quality of life by using a new Cochlear Implant Quality of Life (CIQOL) item bank, which was developed to meet rigorous psychometric standards.

Design, Setting, and Participants

Multicenter cross-sectional study of adults 18 to 89 years of age who had at least 1 year of cochlear implant use and who were recruited through a consortium of 20 cochlear implant centers in the United States. Using an online format, questionnaires were sent to the first 500 participants who contacted the research team. Of these participants, 371 (74.2%) completed the questionnaire. Demographic, hearing-related, and cochlear implant-related data were obtained along with responses to each of the 81 items in the CIQOL item bank. Multivariable linear regression was used to examine demographic, hearing-related, and cochlear implant-related factors associated with scores in each of the 6 CIQOL domains (communication, emotional, entertainment, environment, listening effort, and social).

Main Outcomes and Measures

Association among demographic, hearing-related, and cochlear implant-related factors and CIQOL scores for each of 6 domains.

Results

Of the 371 participants who completed the questionnaire, 222 (59.8%) were women, and the mean (SD) age was 59.5 (14.9) years. The CIQOL scores were normally distributed across the 6 domains. Being employed, having higher household income, longer duration of hearing loss prior to cochlear implantation, and having bilateral rather than unilateral cochlear implantation were associated with higher CIQOL scores in 1 or more domains, but the effect size varied widely (β, 0.1-6.9). Better sentence recognition ability (using AzBio to measure speech recognition) was associated with only a small positive effect size for the communication (β, 0.0 [95% CI, 0.0-0.1]), entertainment (β, 0.0 [95% CI, 0.0-0.1]), and environmental (β, 0.0 [95% CI, 0.0-0.0]) domains. Increased age was associated with lower CIQOL in the entertainment domain (β, -0.3 [95% CI, -1.5 to -0.4]). The demographic, hearing-related, and cochlear implant-related factors included in the multivariable regression models accounted for only a small percentage of the variance in CIQOL domain scores (R2, 0.08-0.17).

Conclusions and Relevance

Several factors were found to predict higher or lower CIQOL scores in specific domains, with speech-recognition ability having only a minimal association. Despite evaluating a large number of demographic, hearing-related, and cochlear implant-related factors, the multivariable models accounted for only a small amount of CIQOL variance. This suggests that patient or other characteristics that contribute to cochlear implant-related quality of life remain largely unknown.

Effects of Bimodal and Bilateral Cochlear Implant Use on a Nonauditory Working Memory Task: Reading Span Tests Over 2 Years Following Cochlear Implantation

Purpose A growing body of evidence indicates that treatment of hearing loss by provision of hearing aids leads to improvements in auditory and visual working memory. The purpose of this study was to assess whether similar working memory benefits are observed following provision of cochlear implants (CIs). Method Fifteen adults with postlingually acquired severe bilateral sensorineural hearing loss completed the prospective longitudinal study. Participants were candidates for bilateral cochlear implantation with some aidable hearing in each ear. Implantation surgeries were carried out sequentially, approximately 1 year apart. Working memory was measured with the visual Reading Span Test (Daneman & Carpenter, 1980) at 5 time points: pre-operatively following a 6-month bilateral hearing aid trial, after 6 and 12 months of bimodal (CI plus contralateral hearing aid) listening experience following the 1st CI surgery and activation, and again after 6 and 12 months of bilateral CI listening experience following the 2nd CI surgery and activation. Results Compared to the preoperative baseline, CI listening experience yielded significant improvements in participants' ability to recall test words in the correct serial order after 12 months in the bimodal condition. Individual performance outcomes were variable, but almost all participants showed increases in task performance over the course of the study. Conclusions These results suggest that, similar to appropriate interventions with hearing aids, treatment of hearing loss with CIs can yield working memory benefits. A likely mechanism is the freeing of cognitive resources previously devoted to effortful listening.

Bimodal Hearing or Bilateral Cochlear Implants? Ask the Patient

OBJECTIVE

The objectives of this study were to assess the effectiveness of various measures of speech understanding in distinguishing performance differences between adult bimodal and bilateral cochlear implant (CI) recipients and to provide a preliminary evidence-based tool guiding clinical decisions regarding bilateral CI candidacy.

DESIGN

This study used a multiple-baseline, cross-sectional design investigating speech recognition performance for 85 experienced adult CI recipients (49 bimodal, 36 bilateral). Speech recognition was assessed in a standard clinical test environment with a single loudspeaker using the minimum speech test battery for adult CI recipients as well as with an R-SPACE 8-loudspeaker, sound-simulation system. All participants were tested in three listening conditions for each measure including each ear alone as well as in the bilateral/bimodal condition. In addition, we asked each bimodal listener to provide a yes/no answer to the question, "Do you think you need a second CI?"

RESULTS

This study yielded three primary findings: (1) there were no significant differences between bimodal and bilateral CI performance or binaural summation on clinical measures of speech recognition, (2) an adaptive speech recognition task in the R-SPACE system revealed significant differences in performance and binaural summation between bimodal and bilateral CI users, with bilateral CI users achieving significantly better performance and greater summation, and (3) the patient's answer to the question, "Do you think you need a second CI?" held high sensitivity (100% hit rate) for identifying likely bilateral CI candidates and moderately high specificity (77% correct rejection rate) for correctly identifying listeners best suited with a bimodal hearing configuration.

CONCLUSIONS

Clinics cannot rely on current clinical measures of speech understanding, with a single loudspeaker, to determine bilateral CI candidacy for adult bimodal listeners nor to accurately document bilateral benefit relative to a previous bimodal hearing configuration. Speech recognition in a complex listening environment, such as R-SPACE, is a sensitive and appropriate measure for determining bilateral CI candidacy and also likely for documenting bilateral benefit relative to a previous bimodal configuration. In the absence of an available R-SPACE system, asking the patient whether or not s/he thinks s/he needs a second CI is a highly sensitive measure, which may prove clinically useful.

Test-Retest Reliability of the Speech, Spatial and Qualities of Hearing Scale (SSQ) in Brazilian Portuguese

Introduction  The Speech, Spatial and Qualities of Hearing Scale (SSQ) is a questionnaire designed to assess the auditory experience and quantify hearing disabilities in realistic communication situations, with particular attention to binaural hearing.

Objective  To determine the test-retest reliability of the SSQ in Brazilian Portuguese.

Method  A total of 35 individuals with mean age of 61 years and mean education of 7 years were interviewed. The mean auditory threshold was 44.29 dBNA in the best ear and 58.04 dBNA in the worst ear. The SSQ in Portuguese was applied at two time points, test and retest. An interval of 7 to 20 days between interviews was established. The level of significance adopted was 0.05, or 5%.

Results  The analysis revealed a high Cronbach α coefficient for the three domains and for the general component of the scale, demonstrating good internal consistency between the items. In addition, a significant strong correlation was detected between test and retest of the SSQ on the analysis by domain and for the general component of the scale. A significant moderate-to-strong correlation between test and retest by question was found, except for question 2 of Part I.

Conclusion  The test-retest reliability indicators showed good stability of the Portuguese version of the SSQ, indicating that the scale is suitable for use in the hearing-impaired population in Brazil.

Topographic map refinement and synaptic strengthening of a sound localization circuit require spontaneous peripheral activity

KEY POINTS

Loss of the calcium sensor otoferlin disrupts neurotransmission from inner hair cells. Central auditory nuclei are functionally denervated in otoferlin knockout mice (Otof KOs) via gene ablation confined to the periphery. We employed juvenile and young adult Otof KO mice (postnatal days (P)10-12 and P27-49) as a model for lacking spontaneous activity and deafness, respectively. We studied the impact of peripheral activity on synaptic refinement in the sound localization circuit from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO). MNTB in vivo recordings demonstrated drastically reduced spontaneous spiking and deafness in Otof KOs. Juvenile KOs showed impaired synapse elimination and strengthening, manifested by broader MNTB-LSO inputs, imprecise MNTB-LSO topography and weaker MNTB-LSO fibres. The impairments persisted into young adulthood. Further functional refinement after hearing onset was undetected in young adult wild-types. Collectively, activity deprivation confined to peripheral protein loss impairs functional MNTB-LSO refinement during a critical prehearing period.

ABSTRACT

Circuit refinement is critical for the developing sound localization pathways in the auditory brainstem. In prehearing mice (hearing onset around postnatal day (P)12), spontaneous activity propagates from the periphery to central auditory nuclei. At the glycinergic projection from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO) of neonatal mice, super-numerous MNTB fibres innervate a given LSO neuron. Between P4 and P9, MNTB fibres are functionally eliminated, whereas the remaining fibres are strengthened. Little is known about MNTB-LSO circuit refinement after P20. Moreover, MNTB-LSO refinement upon activity deprivation confined to the periphery is largely unexplored. This leaves a considerable knowledge gap, as deprivation often occurs in patients with congenital deafness, e.g. upon mutations in the otoferlin gene (OTOF). Here, we analysed juvenile (P10-12) and young adult (P27-49) otoferlin knockout (Otof KO) mice with respect to MNTB-LSO refinement. MNTB in vivo recordings revealed drastically reduced spontaneous activity and deafness in knockouts (KOs), confirming deprivation. As RNA sequencing revealed Otof absence in the MNTB and LSO of wild-types, Otof loss in KOs is specific to the periphery. Functional denervation impaired MNTB-LSO synapse elimination and strengthening, which was assessed by glutamate uncaging and electrical stimulation. Impaired elimination led to imprecise MNTB-LSO topography. Impaired strengthening was associated with lower quantal content per MNTB fibre. In young adult KOs, the MNTB-LSO circuit remained unrefined. Further functional refinement after P12 appeared absent in wild-types. Collectively, we provide novel insights into functional MNTB-LSO circuit maturation governed by a cochlea-specific protein. The central malfunctions in Otof KOs may have implications for patients with sensorineuronal hearing loss.

Bilateral Cochlear Implantation Versus Bimodal Hearing in Patients With Functional Residual Hearing: A Within-subjects Comparison of Audiologic Performance and Quality of Life

OBJECTIVE

Evaluate performance and quality of life changes after sequential bilateral cochlear implantation in patients with preoperative residual hearing functioning in a bimodal hearing configuration.

STUDY DESIGN

Retrospective analysis using within-subjects repeated measures design.

SETTING

Tertiary otologic center.

PATIENTS

Twenty-two adult patients with bilateral sensorineural hearing loss who used bimodal hearing before second cochlear implant (CI) meeting the following criteria: 1) preoperative residual hearing (≤80 dB HL at 250 Hz) in the ear to be implanted, 2) implantation with current CI technology (2013-2016), 3) consonant-nucleus-consonant (CNC) speech recognition testing in the bimodal condition preoperatively and bilateral CI condition postoperatively.

INTERVENTION

Cochlear implantation.

MAIN OUTCOME MEASURES

CNC and AzBio sentence scores in quiet and noise (+5 SNR). Subjective measures of communication difficulty and sound quality were also administered.

RESULTS

Twenty-two patients (mean 64 yr, 68% men) were included. At an average follow-up of 11.8 months, CNC scores in the bilateral CI condition (mean 63%, standard deviation [SD] = 22) were significantly better than preoperative bimodal scores with repeated measures analysis (mean 55%, SD = 22) (p = 0.03). AzBio scores in quiet were also higher with bilateral CI (mean 76%, SD = 24) compared with bimodal listening (mean 69%, SD = 29) (p = 0.0007). Global abbreviated profile of hearing aid benefit (APHAB) and overall speech, spatial, and qualities of hearing (SSQ) scores exhibited significant improvement following bilateral implantation (p = 0.006 for both analyses).

CONCLUSIONS

For patients using a bimodal hearing configuration with substantial residual hearing in the non-CI ear, bilateral cochlear implantation yields improved audiologic performance and better subjective quality of life, irrespective of the ability to preserve acoustic hearing during the second sided implantation.

Cochlear Implantation and Social-Emotional Functioning of Children with Hearing Loss

This study examined the contribution of cochlear implants (CIs) to the social-emotional functioning of children who are deaf or hard of hearing (dhh). Sixty-three parents of children who are dhh participated in the study. Thirty children were CI users and 32 used hearing aids (HAs). They completed the Strengths and Difficulties Questionnaire and a background questionnaire. Parents of children with CIs reported lower levels of hyperactivity/inattention and higher levels of pro-social behavior compared to parents of children with HAs. Additionally, older age when hearing loss was detected was related to more pro-social behavior, and age at implantation among CI users was negatively correlated with children's hyperactivity/inattention and conduct problems. These findings add to the existing knowledge about the many benefits of CIs for individuals with hearing loss and emphasize the possible impact of early implantation to children's social-emotional functioning.

Bimodal Cochlear Implant Listeners' Ability to Perceive Minimal Audible Angle Differences

BACKGROUND

Bilateral inputs should ideally improve sound localization and speech understanding in noise. However, for many bimodal listeners [i.e., individuals using a cochlear implant (CI) with a contralateral hearing aid (HA)], such bilateral benefits are at best, inconsistent. The degree to which clinically available HA and CI devices can function together to preserve interaural time and level differences (ITDs and ILDs, respectively) enough to support the localization of sound sources is a question with important ramifications for speech understanding in complex acoustic environments.

PURPOSE

To determine if bimodal listeners are sensitive to changes in spatial location in a minimum audible angle (MAA) task.

RESEARCH DESIGN

Repeated-measures design.

STUDY SAMPLE

Seven adult bimodal CI users (28-62 years). All listeners reported regular use of digital HA technology in the nonimplanted ear.

DATA COLLECTION AND ANALYSIS

Seven bimodal listeners were asked to balance the loudness of prerecorded single syllable utterances. The loudness-balanced stimuli were then presented via direct audio inputs of the two devices with an ITD applied. The task of the listener was to determine the perceived difference in processing delay (the interdevice delay [IDD]) between the CI and HA devices. Finally, virtual free-field MAA performance was measured for different spatial locations both with and without inclusion of the IDD correction, which was added with the intent to perceptually synchronize the devices.

RESULTS

During the loudness-balancing task, all listeners required increased acoustic input to the HA relative to the CI most comfortable level to achieve equal interaural loudness. During the ITD task, three listeners could perceive changes in intracranial position by distinguishing sounds coming from the left or from the right hemifield; when the CI was delayed by 0.73, 0.67, or 1.7 msec, the signal lateralized from one side to the other. When MAA localization performance was assessed, only three of the seven listeners consistently achieved above-chance performance, even when an IDD correction was included. It is not clear whether the listeners who were able to consistently complete the MAA task did so via binaural comparison or by extracting monaural loudness cues. Four listeners could not perform the MAA task, even though they could have used a monaural loudness cue strategy.

CONCLUSIONS

These data suggest that sound localization is extremely difficult for most bimodal listeners. This difficulty does not seem to be caused by large loudness imbalances and IDDs. Sound localization is best when performed via a binaural comparison, where frequency-matched inputs convey ITD and ILD information. Although low-frequency acoustic amplification with a HA when combined with a CI may produce an overlapping region of frequency-matched inputs and thus provide an opportunity for binaural comparisons for some bimodal listeners, our study showed that this may not be beneficial or useful for spatial location discrimination tasks. The inability of our listeners to use monaural-level cues to perform the MAA task highlights the difficulty of using a HA and CI together to glean information on the direction of a sound source.

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.

Sound Localization and Speech Perception in Noise of Pediatric Cochlear Implant Recipients: Bimodal Fitting Versus Bilateral Cochlear Implants

OBJECTIVES

The aim of this study was to compare binaural performance of auditory localization task and speech perception in babble measure between children who use a cochlear implant (CI) in one ear and a hearing aid (HA) in the other (bimodal fitting) and those who use bilateral CIs.

DESIGN

Thirteen children (mean age ± SD = 10 ± 2.9 years) with bilateral CIs and 19 children with bimodal fitting were recruited to participate. Sound localization was assessed using a 13-loudspeaker array in a quiet sound-treated booth. Speakers were placed in an arc from -90° azimuth to +90° azimuth (15° interval) in horizontal plane. To assess the accuracy of sound location identification, we calculated the absolute error in degrees between the target speaker and the response speaker during each trial. The mean absolute error was computed by dividing the sum of absolute errors by the total number of trials. We also calculated the hemifield identification score to reflect the accuracy of right/left discrimination. Speech-in-babble perception was also measured in the sound field using target speech presented from the front speaker. Eight-talker babble was presented in the following four different listening conditions: from the front speaker (0°), from one of the two side speakers (+90° or -90°), from both side speakers (±90°). Speech, spatial, and quality questionnaire was administered.

RESULTS

When the two groups of children were directly compared with each other, there was no significant difference in localization accuracy ability or hemifield identification score under binaural condition. Performance in speech perception test was also similar to each other under most babble conditions. However, when the babble was from the first device side (CI side for children with bimodal stimulation or first CI side for children with bilateral CIs), speech understanding in babble by bilateral CI users was significantly better than that by bimodal listeners. Speech, spatial, and quality scores were comparable with each other between the two groups.

CONCLUSIONS

Overall, the binaural performance was similar to each other between children who are fit with two CIs (CI + CI) and those who use bimodal stimulation (HA + CI) in most conditions. However, the bilateral CI group showed better speech perception than the bimodal CI group when babble was from the first device side (first CI side for bilateral CI users or CI side for bimodal listeners). Therefore, if bimodal performance is significantly below the mean bilateral CI performance on speech perception in babble, these results suggest that a child should be considered to transit from bimodal stimulation to bilateral CIs.

Spatial Release From Masking in Adults With Bilateral Cochlear Implants: Effects of Distracter Azimuth and Microphone Location

PURPOSE

The primary purpose of this study was to derive spatial release from masking (SRM) performance-azimuth functions for bilateral cochlear implant (CI) users to provide a thorough description of SRM as a function of target/distracter spatial configuration. The secondary purpose of this study was to investigate the effect of the microphone location for SRM in a within-subject study design.

METHOD

Speech recognition was measured in 12 adults with bilateral CIs for 11 spatial separations ranging from -90° to +90° in 20° steps using an adaptive block design. Five of the 12 participants were tested with both the behind-the-ear microphones and a T-mic configuration to further investigate the effect of mic location on SRM.

RESULTS

SRM can be significantly affected by the hemifield origin of the distracter stimulus-particularly for listeners with interaural asymmetry in speech understanding. The greatest SRM was observed with a distracter positioned 50° away from the target. There was no effect of mic location on SRM for the current experimental design.

CONCLUSION

Our results demonstrate that the traditional assessment of SRM with a distracter positioned at 90° azimuth may underestimate maximum performance for individuals with bilateral CIs.

Trials of a Contralateral Hearing Aid After Long-Term Unilateral Cochlear Implant Use in Early-Onset Deafness

PURPOSE

The purpose of this study was to evaluate the practicability of binaural hearing by adding a contralateral hearing aid (HA) after long-term cochlear implant (CI) use in prelingually deaf adults.

METHOD

Five individuals with 1 CI volunteered for a 3-week bimodal (CI + HA) trial. HA gain was set low until sound was tolerable, then increased as listeners acclimated. Participants logged their daily listening experiences and were closely monitored by the audiologist. Measures included pre- and posttrial consonant-nucleus-consonant (CNC) word and phoneme scores and self-reports of satisfaction and listening ability in difficult situations.

RESULTS

Acoustic stimulation was initially unpleasant, but approached comfort at target gain within the 3-week period. Benefit was demonstrated in continued voluntary HA use and higher bimodal phoneme scores compared to CI alone (8%-31% increases) for 4 of the participants.

CONCLUSIONS

When a second CI is not a consideration, a contralateral HA should be pursued as the standard of care for prelingually deaf adults despite substantial auditory deprivation in the previously unaided ear, unpleasant sensations at initial HA fit, or lack of dramatic objective test gains. Frequent audiologist contact, repeated HA adjustments, and client journals are valuable in promoting favorable outcomes with bimodal hearing (adaptation, acceptance, and benefit) for this population.

A Within-Subject Comparison of Bimodal Hearing, Bilateral Cochlear Implantation, and Bilateral Cochlear Implantation With Bilateral Hearing Preservation: High-Performing Patients

OBJECTIVE

To compare speech understanding with bimodal hearing and bilateral cochlear implants (CIs).

STUDY DESIGN

Within-subjects, repeated-measures.

METHODS

Speech understanding was assessed in the following conditions: unilateral hearing aid (HA) in the non-implanted ear, unilateral CI, bimodal (CI + HA), and bilateral CI. In addition, three participants had bilateral hearing preservation and were also tested with bilateral CIs and bilateral HAs (BiBi).

SETTING

Tertiary academic CI center.

PATIENTS

Eight adult sequential bilateral recipients who, despite achieving incredibly high performance with the first CI, self-selected for bilateral cochlear implantation.

INTERVENTION(S)

Bilateral cochlear implantation.

MAIN OUTCOME MEASURE(S)

Speech understanding for the adult minimum speech test battery as well as sentences in semidiffuse noise using the R-SPACE system.

RESULTS

Bilateral CIs afforded significant individual improvement in a complex listening environment even for individuals demonstrating near perfect sentence scores with both the first CI alone as well as the bimodal condition. The 3 BiBi participants demonstrated additional significant benefit over the bilateral CI condition-presumably because of the availability of interaural time difference cues.

CONCLUSIONS

These data suggest that, for noisy environments, adding a second implant can significantly improve speech understanding-even for high-performing unilateral CI with bimodal hearing. In diffuse noise conditions, bilateral acoustic hearing can yield even greater benefits beyond that offered by bilateral implantation.

The history of Cochlear™ Nucleus® sound processor upgrades: 30 years and counting

To review developments in sound processors over the past 30 years that have resulted in significant improvements in outcomes for Nucleus^® recipients.

From hearing with a cochlear implant and a contralateral hearing aid (CI/HA) to hearing with two cochlear implants (CI/CI): a within-subject design comparison

OBJECTIVE

To compare within-subject bilateral-binaural and bimodal complementary abilities between bimodal (cochlear implant and hearing aid; CI/HA) and bilateral CI hearing (CI/CI), thereby enabling better-informed counseling of experienced CI/HA users contemplating contralateral implantation.

STUDY DESIGN

Comparative within-subject case review.

SETTING

Outpatient hearing clinic.

PATIENTS

Ten experienced adult CI/HA users with severe-to-profound hearing loss in the HA ear, who converted to CI/CI between 2 and 11 years after initial implantation.

INTERVENTION

Task-specific testing of bilateral-binaural hearing (sound lateralization, binaural summation/redundancy/unmasking, head-shadow effect), bimodal complementary benefit (contribution of low-frequency information), and a self-report Speech, Spatial, and Qualities of Hearing (SSQ) questionnaire, all before and 1 year after contralateral cochlear implantation.

MAIN OUTCOME MEASURES

Test result differences between CI/HA and CI/CI conditions.

RESULTS

CI/CI hearing was better than CI/HA for speech lateralization and for perception of semantically unpredictable sentences in speech noise with speech at 0 degrees and noise at +90 degrees azimuth on the old CI side. CI/HA was better than CI/CI only for differences between perception of natural prosody speech and of speech with flattened fundamental frequency (F0) contour with speech and noise in front (at 0 degrees azimuth). Total scores on the SSQ questionnaire were higher in CI/CI than in CI/HA users.

CONCLUSION

Counseling regarding contralateral implantation for CI/HA users with severe-to-profound hearing loss in the HA ear, though generally positive, should consider individual functional needs, and cover expectations about the expected trade-off between gaining improved understanding and speech lateralization in challenging listening conditions and losing some low-frequency cues still available with CI/HA hearing.

Self-reported spatial hearing abilities across different cochlear implant profiles

PURPOSE

The goal of this study was to determine how self-reported spatial hearing abilities differ across various cochlear implant (CI) profiles and to examine the degree of subjective benefit following cochlear implantation across different groups of CI users.

METHOD

This was a retrospective study of subjective spatial hearing ability of CI recipients. The subjects consisted of 99 unilateral CI users, 49 bilateral CI users, 32 subjects with a CI and contralateral hearing aid (bimodal users), and 37 short-electrode CI users. All subjects completed the Spatial Hearing Questionnaire (Tyler, Perreau, & Ji, 2009), a questionnaire assessing spatial hearing ability, after implantation, and a subset of the subjects completed the questionnaire pre- and postimplantation.

RESULTS

Subjective spatial hearing ability was rated higher for the bilateral and short electrode CI users compared to the unilateral and bimodal users. There was no significant difference in subjective spatial hearing performance between the bilateral and short electrode CI users and the unilateral CI and bimodal users. A separate analysis of pre- and postimplant performance revealed that all CI groups reported significant improvements in spatial hearing ability after implantation.

CONCLUSION

This study suggests that there are substantial differences in perceived spatial hearing ability among unilateral and bimodal CI users compared with bilateral and short electrode CI users.