Cochlear implantation outcomes in adults: A scoping review

Cochlear Implantation in Neurofibromatosis Type 2: Experience From the UK Neurofibromatosis Type 2 Service

OBJECTIVE

To review the outcomes of cochlear implants (CI) in patients with neurofibromatosis type 2 (NF2) in a large cohort, and identify factors associated with poor hearing benefit.

STUDY DESIGN

Fifteen-year retrospective national observational case series.

SETTING

United Kingdom regional NF2 multidisciplinary teams.

PATIENTS

Consecutive patients with NF2 receiving a CI.

INTERVENTIONS

CI for hearing rehabilitation.

MAIN OUTCOME MEASURES

1) Audiometric performance at 9 to 12 months after implantation using City University of New York (CUNY) sentence recognition score, and Bamford- Kowal-Bench (BKB) word recognition score in quiet (BKBq), and in noise (BKBn). 2) CI use at most recent review.

RESULTS

Sixty four consecutive patients, median age 43 years, were included. Nine to 12 months mean audiometric scores were: CUNY 60.9%, BKBq 45.8%, BKBn 41.6%. There was no difference in audiometric outcomes between VS treatment modalities. At most recent review (median 3.6 years from implantation), 84.9% with device in situ/available data were full or part-time users. Between 9 and 12 months and most recent review there was an interval reduction in mean audiometric scores: CUNY -12.9%, BKBq -3.3%, BKBn -4.9%. Larger tumor size and shorter duration of profound hearing loss were the only variables associated with poorer audiometric scores. Tumor growth at the time of surgery was the only variable associated with CI non-use. Individual patient response was highly variable.

CONCLUSIONS

CI can provide significant and sustained auditory benefits to patients with NF2 independent of tumor treatment modality, with the majority of those implanted becoming at least part-time users. Larger datasets are required to reliably assess the role of independent variables.

Effects of Bilateral Cochlear Implantation on Binaural Listening Tasks for Younger and Older Adults

PURPOSE

This study investigated the objective and subjective benefit of a second cochlear implant (CI) on binaural listening tasks of speech understanding in noise and localization in younger and older adults. We aimed to determine if the aging population can utilize binaural cues and obtain comparable benefits from bilateral CI (BIL_CI) when compared to the younger population.

METHODS

Twenty-nine adults with severe to profound bilateral sensorineural hearing loss were included. Participants were evaluated in two conditions, better CI (BE_CI) alone and BIL_CI using AzBio and Bamford-Kowal-Bench (BKB) sentence in noise tests. Localization tasks were completed in the BIL_CI condition using a broadband stimulus, low-frequency stimuli, and high-frequency stimuli. A subjective questionnaire was administered to assess satisfaction with CI.

RESULTS

Older age was significantly associated with poorer performance on AzBio +5 dB signal-to-noise ratio (SNR) and BKB-speech in noise (SIN); however, improvements from BE_CI to BIL_CI were observed across all ages. In the AzBio +5 condition, nearly half of all participants achieved a significant improvement from BE_CI to BIL_CI with the majority of those occurring in patients younger than 65 years of age. Conversely, the majority of participants who achieved a significant improvement in BKB-SIN were adults >65 years of age. Years of BIL_CI experience and time between implants were not associated with performance. For localization, mean absolute error increased with age for low and high narrowband noise, but not for the broadband noise. Response gain was negatively correlated with age for all localization stimuli. Neither BIL_CI listening experience nor time between implants significantly impacted localization ability. Subjectively, participants report reduction in disability with the addition of the second CI. There is no observed relationship between age or speech recognition score and satisfaction with BIL_CI.

CONCLUSION

Overall performance on binaural listening tasks was poorer in older adults than in younger adults. However, older adults were able to achieve significant benefit from the addition of a second CI, and performance on binaural tasks was not correlated with overall device satisfaction. The significance of the improvement was task and stimulus dependent but suggested a critical limit may exist for optimal performance on SIN tasks for CI users. Specifically, older adults require at least a +8 dB SNR to understand 50% of speech postoperatively; therefore, solely utilizing a fixed +5 dB SNR preoperatively to qualify CI candidates is not recommended as this test condition may introduce limitations in demonstrating CI benefit.

A Modelling Study on the Comparison of Predicted Auditory Nerve Firing Rates for the Personalized Indication of Cochlear Implantation

The decision of whether to perform cochlear implantation is crucial because implantation cannot be reversed without harm. The aim of the study was to compare model-predicted time–place representations of auditory nerve (AN) firing rates for normal hearing and impaired hearing with a view towards personalized indication of cochlear implantation. AN firing rates of 1024 virtual subjects with a wide variety of different types and degrees of hearing impairment were predicted. A normal hearing reference was compared to four hearing prosthesis options, which were unaided hearing, sole acoustic amplification, sole electrical stimulation, and a combination of the latter two. The comparisons and the fitting of the prostheses were based on a ‘loss of action potentials’ (LAP) score. Single-parameter threshold analysis suggested that cochlear implantation is indicated when more than approximately two-thirds of the inner hair cells (IHCs) are damaged. Second, cochlear implantation is also indicated when more than an average of approximately 12 synapses per IHC are damaged due to cochlear synaptopathy (CS). Cochlear gain loss (CGL) appeared to shift these thresholds only slightly. Finally, a support vector machine predicted the indication of a cochlear implantation from hearing loss parameters with a 10-fold cross-validated accuracy of 99.2%.

Poor Performer: A Distinct Entity in Cochlear Implant Users?

INTRODUCTION

Several factors are known to influence speech perception in cochlear implant (CI) users. To date, the underlying mechanisms have not yet been fully clarified. Although many CI users achieve a high level of speech perception, a small percentage of patients does not or only slightly benefit from the CI (poor performer, PP). In a previous study, PP showed significantly poorer results on nonauditory-based cognitive and linguistic tests than CI users with a very high level of speech understanding (star performer, SP). We now investigate if PP also differs from the CI user with an average performance (average performer, AP) in cognitive and linguistic performance.

METHODS

Seventeen adult postlingually deafened CI users with speech perception scores in quiet of 55 (9.32) % (AP) on the German Freiburg monosyllabic speech test at 65 dB underwent neurocognitive (attention, working memory, short- and long-term memory, verbal fluency, inhibition) and linguistic testing (word retrieval, lexical decision, phonological input lexicon). The results were compared to the performance of 15 PP (speech perception score of 15 [11.80] %) and 19 SP (speech perception score of 80 [4.85] %). For statistical analysis, U-Test and discrimination analysis have been done.

RESULTS

Significant differences between PP and AP were observed on linguistic tests, in Rapid Automatized Naming (RAN: p = 0.0026), lexical decision (LexDec: p = 0.026), phonological input lexicon (LEMO: p = 0.0085), and understanding of incomplete words (TRT: p = 0.0024). AP also had significantly better neurocognitive results than PP in the domains of attention (M3: p = 0.009) and working memory (OSPAN: p = 0.041; RST: p = 0.015) but not in delayed recall (delayed recall: p = 0.22), verbal fluency (verbal fluency: p = 0.084), and inhibition (Flanker: p = 0.35). In contrast, no differences were found hereby between AP and SP. Based on the TRT and the RAN, AP and PP could be separated in 100%.

DISCUSSION

The results indicate that PP constitute a distinct entity of CI users that differs even in nonauditory abilities from CI users with an average speech perception, especially with regard to rapid word retrieval either due to reduced phonological abilities or limited storage. Further studies should investigate if improved word retrieval by increased phonological and semantic training results in better speech perception in these CI users.

Cochlear Implantation Improves Both Speech Perception and Patient-Reported Outcomes: A Prospective Follow-Up Study of Treatment Benefits among Adult Cochlear Implant Recipients

Cochlear implantation is considered the best treatment option for patients with severe-to-profound sensorineural hearing loss for whom conventional hearing aids are insufficient. We used a repeated measures longitudinal approach to evaluate speech recognition and patient-reported outcomes after cochlear implantation in an unbiased cohort of Danish adult patients in a prospective cohort study. We assessed 39 recipients before and two times after implantation using a battery of tests that included Dantale I, the Danish Hearing in Noise Test, the Nijmegen Cochlear Implant Questionnaire, and the Speech, Spatial, and Qualities of Hearing Scale. The study group improved significantly on all outcome measures following implantation. On average, Dantale I scores improved by 29 percentage points and Hearing in Noise Test scores improved by 22 percentage points. Most notably, the average Dantale score improved from 26 to 70% in the CI in quiet condition and from 12 to 42% in the cochlear implantation in noise condition when tested monaurally. Dantale demonstrated a significant positive correlation with Nijmegen Cochlear Implant Questionnaire and Speech, Spatial, and Qualities of Hearing Scale scores, while Hearing in Noise Test had no significant correlation with the patient-reported outcome measures. Patients improved significantly at 4 months and marginally improved further at 14 months, indicating that they were approaching a plateau. Our study’s use of audiometric and patient-reported outcome measures provides evidence of the treatment benefits of cochlear implantation in adults, which may help physicians advise patients on treatment decisions and align treatment benefit expectations, as well as serve as a foundation for the development of new cochlear implantation selection criteria.

AudioGene: refining the natural history of KCNQ4, GSDME, WFS1, and COCH-associated hearing loss

Autosomal dominant non-syndromic hearing loss (ADNSHL) displays gene-specific progression of hearing loss, which is amenable to sequential audioprofiling. We sought to refine the natural history of ADNSHL by examining audiometric data in 5-year increments. 2175 audiograms were included from four genetic causes of ADNSHL-KCNQ4 (DFNA2), GSDME (DFNA5), WFS1 (DFNA6/14/38), and COCH (DFNA9). Annual threshold deterioration (ATD) was calculated for each gene: for the speech-frequency pure tone average, the ATD, respectively, was 0.72 dB/year, 0.94 dB/year, 0.53 dB/year, and 1.41 dB/year, with the largest drops occurring from ages 45-50 (0.89 dB/year; KCNQ4), 5-10 (1.42 dB/year; GSDME), 40-45 (0.83 dB/year; WFS1), and 50-55 (2.09 dB/year; COCH). 5-year interval analysis of audiograms reveals the gene specific natural history of KCNQ4, GSDME, WFS1 and COCH-related progressive hearing loss. Identifying ages at which hearing loss is most rapid informs clinical care and patient expectations. Natural history data are also essential to define outcomes of clinical trials that test novel therapies designed to correct or ameliorate these genetic forms of hearing loss.

Central auditory deficits associated with genetic forms of peripheral deafness

Since the 1990s, the study of inherited hearing disorders, mostly those detected at birth, in the prelingual period or in young adults, has led to the identification of their causal genes. The genes responsible for more than 140 isolated (non-syndromic) and about 400 syndromic forms of deafness have already been discovered. Studies of mouse models of these monogenic forms of deafness have provided considerable insight into the molecular mechanisms of hearing, particularly those involved in the development and/or physiology of the auditory sensory organ, the cochlea. In parallel, studies of these models have also made it possible to decipher the pathophysiological mechanisms underlying hearing impairment. This has led a number of laboratories to investigate the potential of gene therapy for curing these forms of deafness. Proof-of-concept has now been obtained for the treatment of several forms of deafness in mouse models, paving the way for clinical trials of cochlear gene therapy in patients in the near future. Nevertheless, peripheral deafness may also be associated with central auditory dysfunctions and may extend well beyond the auditory system itself, as a consequence of alterations to the encoded sensory inputs or involvement of the causal deafness genes in the development and/or functioning of central auditory circuits. Investigating the diversity, causes and underlying mechanisms of these central dysfunctions, the ways in which they could impede the expected benefits of hearing restoration by peripheral gene therapy, and determining how these problems could be remedied is becoming a research field in its own right. Here, we provide an overview of the current knowledge about the central deficits associated with genetic forms of deafness.

Cochlear implant aesthetics and its impact on stigma, social interaction and quality of life: a mixed-methods study protocol

INTRODUCTION

Awareness of the benefits of cochlear implants is low, and barriers such as fear of surgery and ongoing rehabilitation have been noted. Perceived stigma associated with hearing loss also plays a key role, with many adults not wanting to appear old or be identified as a person with a disability. In effect, a cochlear implant makes deafness visible. New technologies have led to a smaller external profile for some types of cochlear implants, but qualitative assessments of benefit have not been explored. This study will examine cochlear implant aesthetics and cosmetics, and its impact on perceived stigma, social interactions, communication and quality of life. A particular focus will be the examination of totally implantable device concepts. A secondary aim is to understand what research techniques are best suited and most appealing for cochlear implant recipients, to assist in future study design and data collection methods.

METHODS AND ANALYSIS

This study utilises a mixed-methods design. Three datasets will be collected from each participant with an expected sample size of 10-15 participants to allow for data saturation of themes elicited. Each participant will complete a demographic questionnaire, a quickfire survey (a short concise questionnaire on a topic of research familiarity and preference) and a semi-structured interview. Questionnaire and quickfire survey data will be analysed using descriptive statistics. Interviews will be transcribed and analysed thematically. All participants will be adults with more than 1 year of experience using cochlear implants.

ETHICS AND DISSEMINATION

This study has been granted ethical approval from Macquarie University (HREC: 520211056232432) and meets the requirements set out in the National Statement on Ethical Conduct in Human Research. Study findings will be disseminated widely through international peer-reviewed journal articles, public and academic presentations, plain language summaries for participants and an executive summary for the project funder. This work was supported by Cochlear Limited (Cochlear Ltd). The funder will have no role in conducting or reporting on the study.

Cognition and Cognitive Reserve in Cochlear Implant Recipients

At present, dementia is a hot topic. Hearing loss is considered to be a modifiable risk factor for cognitive decline. The underlying mechanism remains unclear and might be mediated by socioeconomic and psychosocial factors. Cochlear implantation has been shown not only to restore auditory abilities, but also to decrease mental distress and to improve cognitive functions in people with severe hearing impairment. However, the promising results need to be confirmed. In a prospective single-center study, we tested the neurocognitive abilities of a large group of 71 subjects with bilateral severe hearing impairment with a mean age of 66.03 (SD = 9.15) preoperatively and 6, 12, and 24 months after cochlear implantation using a comprehensive non-auditory computer-based test battery, and we also assessed the cognitive reserve (CR) [Cognitive Reserve Index (CRI)], health-related quality of life (QoL) (Nijmegen Cochlear Implant Questionnaire), and depression (Geriatric Depression Scale-15). Cognitive functions significantly increased after 6 months in attention (p = 0.00004), working memory (operation span task; p = 0.002), and inhibition (p = 0.0002); and after 12 months in recall (p = 0.003) and verbal fluency (p = 0.0048), and remained stable up to 24 months (p ≥ 0.06). The CR positively correlated with cognitive functions pre- and post-operatively (both p < 0.005), but postoperative improvement in cognition was better in subjects with poor CR (p = 0.003). Depression had only a slight influence on one subtest. No correlation was found among cognitive skills, quality of life, and speech perception (each p ≥ 0.05). Cochlear implantation creates an enriched environment stimulating the plasticity of the brain with a global positive impact on neurocognitive functions, especially in subjects with poor preoperative cognitive performance and low cognitive reserve.

Listening-Based Communication Ability in Adults With Hearing Loss: A Scoping Review of Existing Measures

Introduction

Hearing loss in adults has a pervasive impact on health and well-being. Its effects on everyday listening and communication can directly influence participation across multiple spheres of life. These impacts, however, remain poorly assessed within clinical settings. Whilst various tests and questionnaires that measure listening and communication abilities are available, there is a lack of consensus about which measures assess the factors that are most relevant to optimising auditory rehabilitation. This study aimed to map current measures used in published studies to evaluate listening skills needed for oral communication in adults with hearing loss.

Methods

A scoping review was conducted using systematic searches in Medline, EMBASE, Web of Science and Google Scholar to retrieve peer-reviewed articles that used one or more linguistic-based measure necessary to oral communication in adults with hearing loss. The range of measures identified and their frequency where charted in relation to auditory hierarchies, linguistic domains, health status domains, and associated neuropsychological and cognitive domains.

Results

9121 articles were identified and 2579 articles that reported on 6714 discrete measures were included for further analysis. The predominant linguistic-based measure reported was word or sentence identification in quiet (65.9%). In contrast, discourse-based measures were used in 2.7% of the articles included. Of the included studies, 36.6% used a self-reported instrument purporting to measures of listening for communication. Consistent with previous studies, a large number of self-reported measures were identified (n = 139), but 60.4% of these measures were used in only one study and 80.7% were cited five times or fewer.

Discussion

Current measures used in published studies to assess listening abilities relevant to oral communication target a narrow set of domains. Concepts of communicative interaction have limited representation in current measurement. The lack of measurement consensus and heterogeneity amongst the assessments limit comparisons across studies. Furthermore, extracted measures rarely consider the broader linguistic, cognitive and interactive elements of communication. Consequently, existing measures may have limited clinical application if assessing the listening-related skills required for communication in daily life, as experienced by adults with hearing loss.

Speech Recognition and Listening Effort in Cochlear Implant Recipients and Normal-Hearing Listeners

The outcome of cochlear implantation is typically assessed by speech recognition tests in quiet and in noise. Many cochlear implant recipients reveal satisfactory speech recognition especially in quiet situations. However, since cochlear implants provide only limited spectro-temporal cues the effort associated with understanding speech might be increased. In this respect, measures of listening effort could give important extra information regarding the outcome of cochlear implantation. In order to shed light on this topic and to gain knowledge for clinical applications we compared speech recognition and listening effort in cochlear implants (CI) recipients and age-matched normal-hearing listeners while considering potential influential factors, such as cognitive abilities. Importantly, we estimated speech recognition functions for both listener groups and compared listening effort at similar performance level. Therefore, a subjective listening effort test (adaptive scaling, “ACALES”) as well as an objective test (dual-task paradigm) were applied and compared. Regarding speech recognition CI users needed about 4 dB better signal-to-noise ratio to reach the same performance level of 50% as NH listeners and even 5 dB better SNR to reach 80% speech recognition revealing shallower psychometric functions in the CI listeners. However, when targeting a fixed speech intelligibility of 50 and 80%, respectively, CI users and normal hearing listeners did not differ significantly in terms of listening effort. This applied for both the subjective and the objective estimation. Outcome for subjective and objective listening effort was not correlated with each other nor with age or cognitive abilities of the listeners. This study did not give evidence that CI users and NH listeners differ in terms of listening effort – at least when the same performance level is considered. In contrast, both listener groups showed large inter-individual differences in effort determined with the subjective scaling and the objective dual-task. Potential clinical implications of how to assess listening effort as an outcome measure for hearing rehabilitation are discussed.

Towards the translation of electroconductive organic materials for regeneration of neural tissues

Carbon-based conductive and electroactive materials (e.g., derivatives of graphene, fullerenes, polypyrrole, polythiophene, polyaniline) have been studied since the 1970s for use in a broad range of applications. These materials have electrical properties comparable to those of commonly used metals, while providing other benefits such as flexibility in processing and modification with biologics (e.g., cells, biomolecules), to yield electroactive materials with biomimetic mechanical and chemical properties. In this review, we focus on the uses of these electroconductive materials in the context of the central and peripheral nervous system, specifically recent studies in the peripheral nerve, spinal cord, brain, eye, and ear. We also highlight in vivo studies and clinical trials, as well as a snapshot of emerging classes of electroconductive materials (e.g., biodegradable materials). We believe such specialized electrically conductive biomaterials will clinically impact the field of tissue regeneration in the foreseeable future. STATEMENT OF SIGNIFICANCE: This review addresses the use of conductive and electroactive materials for neural tissue regeneration, which is of significant interest to a broad readership, and of particular relevance to the growing community of scientists, engineers and clinicians in academia and industry who develop novel medical devices for tissue engineering and regenerative medicine. The review covers the materials that may be employed (primarily focusing on derivatives of fullerenes, graphene and conjugated polymers) and techniques used to analyze materials composed thereof, followed by sections on the application of these materials to nervous tissues (i.e., peripheral nerve, spinal cord, brain, optical, and auditory tissues) throughout the body.

Effect of Frequency Response Manipulations on Musical Sound Quality for Cochlear Implant Users

Cochlear implant (CI) users commonly report degraded musical sound quality. To improve CI-mediated music perception and enjoyment, we must understand factors that affect sound quality. In the present study, we utilize frequency response manipulation (FRM), a process that adjusts the energies of frequency bands within an audio signal, to determine its impact on CI-user sound quality assessments of musical stimuli. Thirty-three adult CI users completed an online study and listened to FRM-altered clips derived from the top songs in Billboard magazine. Participants assessed sound quality using the MUltiple Stimulus with Hidden Reference and Anchor for CI users (CI-MUSHRA) rating scale. FRM affected sound quality ratings (SQR). Specifically, increasing the gain for low and mid-range frequencies led to higher quality ratings than reducing them. In contrast, manipulating the gain for high frequencies (those above 2 kHz) had no impact. Participants with musical training were more sensitive to FRM than non-musically trained participants and demonstrated preference for gain increases over reductions. These findings suggest that, even among CI users, past musical training provides listeners with subtleties in musical appraisal, even though their hearing is now mediated electrically and bears little resemblance to their musical experience prior to implantation. Increased gain below 2 kHz may lead to higher sound quality than for equivalent reductions, perhaps because it offers greater access to lyrics in songs or because it provides more salient beat sensations.

Speech token detection and discrimination in individual infants using functional near-infrared spectroscopy

Speech detection and discrimination ability are important measures of hearing ability that may inform crucial audiological intervention decisions for individuals with a hearing impairment. However, behavioral assessment of speech discrimination can be difficult and inaccurate in infants, prompting the need for an objective measure of speech detection and discrimination ability. In this study, the authors used functional near-infrared spectroscopy (fNIRS) as the objective measure. Twenty-three infants, 2 to 10 months of age participated, all of whom had passed newborn hearing screening or diagnostic audiology testing. They were presented with speech tokens at a comfortable listening level in a natural sleep state using a habituation/dishabituation paradigm. The authors hypothesized that fNIRS responses to speech token detection as well as speech token contrast discrimination could be measured in individual infants. The authors found significant fNIRS responses to speech detection in 87% of tested infants (false positive rate 0%), as well as to speech discrimination in 35% of tested infants (false positive rate 9%). The results show initial promise for the use of fNIRS as an objective clinical tool for measuring infant speech detection and discrimination ability; the authors highlight the further optimizations of test procedures and analysis techniques that would be required to improve accuracy and reliability to levels needed for clinical decision-making.

Development of a novel screening tool for predicting Cochlear implant candidacy

OBJECTIVES

Cochlear implantation (CI) is a well-established treatment for sensorineural hearing loss. Due in part to a lack of referral guidelines, CI technology remains underutilized, and many patients who could benefit from CI may not be referred for evaluation. This study aimed to develop a model for predicting CI candidacy using routine audiometric measures, with the goal of providing guidance to clinicians regarding when to refer a patient for CI evaluation.

METHODS

Unaided three-frequency pure tone average (PTA), unaided speech discrimination score (SDS), and best-aided sentence recognition testing with AZBio sentence lists were collected from 252 subjects undergoing CIE. Candidacy was defined by meeting traditional (AZBio score ≤ 60%), or Medicare criteria (≤40%). A logistic regression model was developed to predict candidacy. Confusion matrices were plotted to determine the sensitivity and specificity at various probability thresholds.

RESULTS

Logistic regression models were capable of predicting probability of candidacy for traditional criteria (P < .001) and Medicare criteria (P < .001). PTA and SDS were significant predictors (P < .001). Using a probability cutoff of .5, the models yielded a sensitivity rate of 91% and 78% for traditional and Medicare criteria, respectively.

CONCLUSION

Probability of CI candidacy may be determined using a novel screening tool for referral. This tool supports individualized counseling, serves as a proof of concept for candidacy prediction, and could be modified based on an institution's philosophy regarding an acceptable false positive rate of referral.

LEVEL OF EVIDENCE

4.

Bioengineering applications for hearing restoration: emerging biologically inspired and biointegrated designs

Cochlear implantation has become the standard of care for hearing loss not amenable to amplification by bypassing the structures of the cochlea and stimulating the spiral ganglion neurons directly. Since the first single channel electrodes were implanted, significant advancements have been made: multi-channel arrays are now standard, they are softer to avoid damage to the cochlea and pre-curved to better position the electrode array adjacent to the nerve, and surgical and stimulation techniques have helped to conform to the anatomy and physiology of the cochlea. However, even with these advances the experience does not approach that of normal hearing. In order to make significant advances in performance, the next generation of implants will require novel interface technology. Advances in regenerative techniques, optogenetics, piezoelectric materials, and bioengineered living scaffolds hold the promise for the next generation of implantable hearing devices, and hope for the restoration of natural hearing.

Neurofibromatoses

The neurofibromatoses are a group of genetic disorders that cause development of nervous system tumors as well as various other tumor and systemic manifestations. Neurofibromatosis type 1 is the most prevalent of these conditions and has the most variable phenotype and highest risk of malignant tumor formation. Neurofibromatosis type 2 has no associated malignant tumors but does carry significant morbidity, including deafness, facial weakness, and physical disability. Schwannomatosis is the least prevalent of these disorders and is characterized primarily by nonvestibular schwannomas and pain.

Rasch Analysis of the Listening Effort Questionnaire-Cochlear Implant

OBJECTIVES

Listening effort may be defined as the attentional and cognitive resources needed to understand an auditory message, modulated by motivation. Despite the use of hearing devices such as hearing aids or cochlear implants (CIs), the requirement for high listening effort remains a challenge for individuals with hearing loss. The Listening Effort Questionnaire-Cochlear Implant (LEQ-CI) is a hearing-specific patient-reported outcome measure (PROM), which has been designed for use in the CI candidacy and rehabilitation process to assess perceived listening effort in everyday life in adults with severe-profound hearing loss. The LEQ-CI has been developed in line with international consensus-based standards for best practice in PROM construction. The aim of this study was to improve the measurement precision of the LEQ-CI and to assess its psychometric measurement properties.

DESIGN

A field test was undertaken with 330 CI patients from five National Health Service auditory implant centers in the United Kingdom. Participants were adults (≥18 years of age), had a severe-profound hearing loss, and met the UK candidacy criteria for cochlear implantation specified by the National Institute for Health and Care Excellence (NICE). Participants completed and returned an anonymized 29-item (each with a 5- or 7-point response option), draft version of the LEQ-CI (LEQ-CI29) and a demographic questionnaire. Rasch analysis was undertaken using Winsteps software and the partial credit model to assess rating scale function and item fit. Results informed refinements to produce a 21-item version (LEQ-CI21), which underwent a further Rasch analysis.

RESULTS

The sample was predominantly female: 60.3% (n = 191). Median age of participants was 66 (range 21 to 89) years, with 7.3% (n = 24) of respondents being CI candidates and 92.7% (n = 306) being CI recipients. Mean duration of implantation was 3.8 (SD = 4.8) years. Initial Rasch analysis of the LEQ-CI29 revealed poor rating scale functioning. Collapsing the 5- and 7-point rating scales to 3- and 4-point scales and removing eight items produced a 21-item PROM (LEQ-CI21). Rasch analysis of the LEQ-CI21 showed good fit to the Rasch measurement model. No items showed misfit and dimensionality analysis supported the existence of a single Rasch dimension, defined as perceived listening effort in daily life. Person reliability was 0.91 and the person separation index was 3.28, establishing four levels of person ability. The item separation index was 9.69, confirming the item hierarchy. No items showed differential item functioning for gender or age. The item difficulty range was -0.81 to 1.05, the person ability range for nonextreme persons was -3.54 to 2.49, and the mean person ability was -0.31.

CONCLUSIONS

Overall, the LEQ-CI21 was found to meet the Rasch model criteria for interval-level measurement. The LEQ-CI21 is the first PROM to be developed specifically for the measurement of perceived listening effort and one of the first patient-reported outcome measures for use with CI patients to be developed using Rasch analysis. The LEQ-CI21 has the potential to be used as a research tool and in clinical practice to evaluate perceived listening effort in daily life. Further psychometric evaluation of the LEQ-CI21 is planned.

Effectiveness of Computer-Based Auditory Training for Adult Cochlear Implant Users: A Randomized Crossover Study

The aim of this study was to assess whether a computer-based speech-in-noise auditory training (AT) program would lead to short- and long-term changes in trained and untrained measures of listening, cognition, and quality of life. A secondary aim was to assess whether directly training the underlying cognitive abilities required for speech perception in noise, using a computer-based visual training (VT) program without the auditory component, would elicit comparable outcomes as the AT program. A randomized crossover study with repeated measures was conducted with 26 adult cochlear implant users. Participants completed either 6 weeks of speech perception in noise training followed by 6 weeks of masked text recognition training, or vice versa. Outcome measures were administered twice before each training program, as well as twice after the completion of each program. The test battery was designed to evaluate whether training led to improvements in listening abilities, cognitive abilities, or quality of life. Mixed-effects models were conducted to analyze whether changes occurred on the trained tasks and on untrained outcome measures after training. Statistically significant improvements were shown for verbal recognition performance during both training programs, in particular for consonants in words, and during the first 2 weeks of training. This on-task learning, however, did not lead to clear improvements in outcomes measured beyond the training programs. This suggests that experienced cochlear implant users may not show transfer of on-task learning to untrained tasks after computer-based auditory and visual training programs such as the ones used in this study.

Cochlear Implant Research and Development in the Twenty-first Century: A Critical Update

Cochlear implants (CIs) are the world's most successful sensory prosthesis and have been the subject of intense research and development in recent decades. We critically review the progress in CI research, and its success in improving patient outcomes, from the turn of the century to the present day. The review focuses on the processing, stimulation, and audiological methods that have been used to try to improve speech perception by human CI listeners, and on fundamental new insights in the response of the auditory system to electrical stimulation. The introduction of directional microphones and of new noise reduction and pre-processing algorithms has produced robust and sometimes substantial improvements. Novel speech-processing algorithms, the use of current-focusing methods, and individualised (patient-by-patient) deactivation of subsets of electrodes have produced more modest improvements. We argue that incremental advances have and will continue to be made, that collectively these may substantially improve patient outcomes, but that the modest size of each individual advance will require greater attention to experimental design and power. We also briefly discuss the potential and limitations of promising technologies that are currently being developed in animal models, and suggest strategies for researchers to collectively maximise the potential of CIs to improve hearing in a wide range of listening situations.

A MultiCenter Analysis of Factors Associated with Hearing Outcome for 2,735 Adults with Cochlear Implants

While the majority of cochlear implant recipients benefit from the device, it remains difficult to estimate the degree of benefit for a specific patient prior to implantation. Using data from 2,735 cochlear-implant recipients from across three clinics, the largest retrospective study of cochlear-implant outcomes to date, we investigate the association between 21 preoperative factors and speech recognition approximately one year after implantation and explore the consistency of their effects across the three constituent datasets. We provide evidence of 17 statistically significant associations, in either univariate or multivariate analysis, including confirmation of associations for several predictive factors, which have only been examined in prior smaller studies. Despite the large sample size, a multivariate analysis shows that the variance explained by our models remains modest across the datasets (R2=0.12–0.21). Finally, we report a novel statistical interaction indicating that the duration of deafness in the implanted ear has a stronger impact on hearing outcome when considered relative to a candidate’s age. Our multicenter study highlights several real-world complexities that impact the clinical translation of predictive factors for cochlear implantation outcome. We suggest several directions to overcome these challenges and further improve our ability to model patient outcomes with increased accuracy.

Meta-Analysis of Speech Recognition Outcomes in Younger and Older Adults With Cochlear Implants

Purpose Meta-analyses were conducted to compare pre- to postoperative speech recognition improvements and postoperative scores after cochlear implantation in younger (< 60 years) and older (> 60 years) adults. Method Studies were identified with electronic databases and through manual search of the literature. In the primary analyses, effect sizes between pre- and postoperative scores for each age group were calculated using a formula appropriate for repeated-measures designs. Using the effect sizes, two separate meta-analyses using a random-effects restricted maximum likelihood model were conducted for experiments using word and sentence recognition stimuli in quiet. Secondary meta-analyses were conducted to examine average postimplant, percent correct word recognition, sentence recognition, and speech recognition in noise in studies that included both older and younger age groups. Traditional Hedges's g effect sizes were calculated between the two groups. Results For the primary analyses, experiments using word and sentence recognition stimuli yielded significant, large effect sizes for the younger and older adult cochlear implant recipients with no significant differences between the older and younger age groups. However, the secondary meta-analyses of postoperative scores suggested significant differences between age groups for stimuli in quiet and noise. Conclusions Although older and younger adults with implants achieve the same magnitude of pre- to postimplant speech recognition benefit in quiet, the overall postoperative speech recognition outcomes in quiet and noise are superior in younger over older adults. Strategies to mitigate these group differences are critical for ensuring optimal outcomes in elderly individuals who are candidates for cochlear implants.

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.

A State-of-Art Review of Digital Technologies for the Next Generation of Tinnitus Therapeutics

Background: Digital processing has enabled the development of several generations of technology for tinnitus therapy. The first digital generation was comprised of digital Hearing Aids (HAs) and personal digital music players implementing already established sound-based therapies, as well as text based information on the internet. In the second generation Smart-phone applications (apps) alone or in conjunction with HAs resulted in more therapy options for users to select from. The 3rd generation of digital tinnitus technologies began with the emergence of many novel, largely neurophysiologically-inspired, treatment theories that drove development of processing; enabled through HAs, apps, the internet and stand-alone devices. We are now of the cusp of a 4th generation that will incorporate physiological sensors, multiple transducers and AI to personalize therapies. Aim: To review technologies that will enable the next generations of digital therapies for tinnitus. Methods: A "state-of-the-art" review was undertaken to answer the question: what digital technology could be applied to tinnitus therapy in the next 10 years? Google Scholar and PubMed were searched for the 10-year period 2011-2021. The search strategy used the following key words: "tinnitus" and ["HA," "personalized therapy," "AI" (and "methods" or "applications"), "Virtual reality," "Games," "Sensors" and "Transducers"], and "Hearables." Snowballing was used to expand the search from the identified papers. The results of the review were cataloged and organized into themes. Results: This paper identified digital technologies and research on the development of smart therapies for tinnitus. AI methods that could have tinnitus applications are identified and discussed. The potential of personalized treatments and the benefits of being able to gather data in ecologically valid settings are outlined. Conclusions: There is a huge scope for the application of digital technology to tinnitus therapy, but the uncertain mechanisms underpinning tinnitus present a challenge and many posited therapeutic approaches may not be successful. Personalized AI modeling based on biometric measures obtained through various sensor types, and assessments of individual psychology and lifestyles should result in the development of smart therapy platforms for tinnitus.

Hearing Loss and Dementia: A Meta-Analysis of Prospective Cohort Studies

Background: Consensus is lacking with regard to whether hearing loss is an independent risk factor for dementia. We therefore conducted a meta-analysis to clarify the relationship of hearing loss and dementia.

Methods: Prospective cohort studies investigating the association between hearing loss and the incidence of dementia in a community-derived population were included by searching electronic databases that included PubMed, Embase, and Cochrane's Library. A random-effects model was adopted to combine the results.

Results: Fourteen cohorts including 726,900 participants were analyzed. It was shown that hearing loss was independently associated with dementia [adjusted hazard ratio (HR): 1.59, 95% confidence interval (CI): 1.37 to 1.86, p < 0.001; I² = 86%]. Sensitivity analysis sequentially excluding any of the individual studies included showed similar results. Subgroup analysis according to the diagnostic methods for hearing loss, validation strategy for dementia, follow-up duration, and adjustment of apolipoprotein E genotype also showed consistent results (p-values for subgroup differences all > 0.05). Meta-analysis with five studies showed that hearing loss was also connected to higher risk of Alzheimer's disease (adjusted HR: 2.24, 95% CI: 1.32 to 3.79, p = 0.003; I² = 2%).

Conclusions: Hearing loss may increase the risk of dementia in the adult population. Whether effective treatment for hearing loss could reduce the incidence of dementia should be explored in the future.

Outcome of cochlear implantation in the worse ear of post-lingual asymmetric hearing loss: elucidation of prognostic markers

BACKGROUND

Specific correlations between the outcomes of cochlear implantation (CI) and hearing thresholds of the both ears in post-lingual asymmetric hearing loss (AHL) patients were not clear.

AIMS/OBJECTIVES

To identify the variables influencing the outcome of CI in post-lingual AHL patients.

METHOD

We included 18 adult subjects who had CI in the worse ear due to post-lingual AHL with average hearing asymmetry of 36 dB. Speech perception scores were evaluated in the sound field with hearing aid on the better ear before CI, and with the cochlear implant in the worse ear at 3, 6, and 12 months after CI switch-on.

RESULTS

Average increases in phonetically balanced word score, spondee word score, and everyday sentence score at 12 months from CI switch-on compared with those before CI were 38.9%p, 46.2%p, and 52.4%p, respectively. Multiple linear regression analysis showed that speech perception scores were negatively influenced by age at implantation and hearing threshold difference of both ears (HTD-Both) itself, rather than the worse or better ear hearing thresholds.

CONCLUSIONS AND SIGNIFICANCE

Post-lingual AHL subjects with high average hearing asymmetry can benefit from CI in the worse ear, while CI outcomes can be adversely influenced by HTD-Both and age at implantation both in the short- and long-term follow-up.

Prediction models for clinical outcome after cochlear implantation: a systematic review

OBJECTIVES

Cochlear implants (CIs) are implantable hearing devices with a wide variation in clinical outcome between patients. We aim to provide an overview of the literature on prediction models and their performance for clinical outcome after cochlear implantation in bilateral hearing loss or deafness.

STUDY DESIGN AND SETTING

In this systematic review, studies describing the development or external validation of a multivariable model for predicting clinical CI outcome were eligible for selection.

RESULTS

A total of 4,042 references were screened. We included nine development studies and one external validation study. The outcome measure of all development studies was speech perception performance after cochlear implantation. The most commonly used model predictors were duration of hearing loss or deafness (n = 7), different types of preoperative measurements (n = 5), and etiology (n = 3). In three studies, crucial information to enable the model to be used for individual risk prediction was missing. One study performed internal validation,two models were externally validated. One study reported specific discrimination or calibration performance measures.

CONCLUSION

Although many articles describe development studies of prediction models for speech perception performance after cochlear implantation, the value of most of these models for their application in clinical practice remains unclear. Therefore, research should focus on increasing the clinical relevance of existing CI outcome prediction models.

Cochlear Implantation in the Active Duty Military Population: A Survey Assessing Military Readiness and Satisfaction

OBJECTIVE

Evaluate the impact of cochlear implantation (CI) on retention for United States active duty (AD) service members.

STUDY DESIGN

Retrospective observational study.

SETTING

Tertiary military CI centers.

PATIENTS

AD service members who underwent CI and completed a telephonic survey.

MAIN OUTCOME MEASURES

The ability for military personnel to maintain AD status following CI as determined by the nonvolitional hearing-related AD separation rate and whether subjects would recommend CI to other qualified candidates.

RESULTS

Twenty AD service members who underwent CI between 2004 and 2020 completed a telephonic survey. Fifteen (75%) were single-sided deafness (SSD) and five were traditional CI candidates. The mean age was 40.3 years (range 27.5-64.3), 19 (95%) were male, and 12 (80%) were Caucasian. Ten (50%) were officers and 14 (70%) were noncombat support personnel. Idiopathic sudden sensorineural hearing loss was the most common cause of hearing loss (8, 40%) followed by occupational noise exposure (4, 20%). Sixteen (80%) maintained AD status yielding 46.15 person-years of AD service following CI. For SSD, 14 (93%) maintained AD status yielding 40.54 person-years of AD service. The nonvolitional hearing-related patient separation rate for CI recipients with bilateral hearing loss was 35.65 cases per 100 AD person-years and 0 cases per 100 person-years for SSD candidates. Nineteen (95%) stated they would recommend CI to other AD CI candidates.

CONCLUSIONS

The vast majority of AD CI recipients, and particularly those with SSD, are able to remain on AD after surgery and report a high degree of satisfaction with their implant.

Cochlear Implantation

BACKGROUND

Hearing impairment that is too severe to be adequately treated with conventional hearing aids can lead, in children, to severe developmental disturbances of hearing and language, and, in adults, to communicative and social deprivation. Recent advances in medical device technology and in microsurgical techniques have led to an expansion of the indications for cochlear implantation (CI) for adults with progressive hearing loss in older age, and to a restructuring of the process of care for these patients in Germany.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, as well as on the CI guidelines and CI "white book" of the German Society of Otolaryngology and Head and Neck Surgery.

RESULTS

Early and accurate diagnosis is crucial for the successful auditory rehabilitation of high-grade hearing impairment. In children, a key role is played by newborn auditory screening, which is mandatory in Germany and enables the provision of a CI in the first year of life when necessary. 86% of the children receiving a CI achieve linguistic comprehension of fluently spoken sentences. For adults, positive prognostic factors for hearing after the provision of a CI include a highly motivated patient, "postlingual" onset of the hearing impairment (i.e., after the acquisition of language), and a brief duration of deafness. Auditory rehabilitation is associated with significant improvement, not just of hearing and of the comprehension of spoken language, but also of quality of life, particularly in elderly patients. For patients of any age with bilateral hearing loss, CIs should be provided on both sides, if possible. The more common complications of the procedure, with a probability of 2-4% each, are technical implant defects, dizziness, and wound-healing disturbances.

CONCLUSION

Cochlear implantation, performed in specialized centers, is a safe and reliable technique and regularly enables the successful rehabilitation of hearing in both children and adults.

Cochlear Implantation in Meniere's Disease: A Systematic Review and Meta-Analysis

OBJECTIVES/HYPOTHESIS

Meniere's disease (MD) is a debilitating condition characterized by hearing loss, vertigo, and tinnitus. The objective of this study was to systematically investigate outcomes in MD after cochlear implantation (CoI), with and without labyrinthectomy.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A systematic review of articles in Medline and Embase was performed to identify all studies of patients with MD who underwent CoI. This analysis evaluates outcomes of speech recognition, pure tone audiometry, vertigo, tinnitus, and quality of life.

RESULTS

Of 321 studies identified, 37 were included, involving 216 patients. Mean age at implantation was 61.4 years (range 27-85 years) with average length of follow-up at 1.7 years (range 0-9 years). Forty-four (20.4%) patients underwent labyrinthectomy. Meta-analysis demonstrated significant improvements in audiometric outcomes following CoI. There was a statistically significant improvement in Hearing in Noise Test performance, with a mean difference improvement of 44.7 (95% confidence interval [CI] [8.8, 80.6]) at 6 months and 60.1 (95% CI [35.3, 85.0]) at 12 months. The Freiburger Monosyllabic Test (FMT) and Consonant-Nucleus-Consonant (CNC) also improved significantly, with mean difference improvements of 46.2 (95% CI [30.0, 62.4]) for FMT and 19.3 (95% CI [8.1, 30.4]) for CNC. There was a statistically significant decrease in tinnitus, as measured by a mean difference reduction of 48.1 (95% CI [1.0, 95.2]) in the Tinnitus Handicap Index.

CONCLUSIONS

CoI with and without simultaneous labyrinthectomy is a viable treatment option for patients with MD, yielding high rates of tinnitus suppression and vertigo control. Post-CoI MD patients demonstrate similar postoperative speech perception outcomes to non-MD implant recipients. Laryngoscope, 131:1845-1854, 2021.

Predictive models for cochlear implant outcomes: Performance, generalizability, and the impact of cohort size

While cochlear implants have helped hundreds of thousands of individuals, it remains difficult to predict the extent to which an individual's hearing will benefit from implantation. Several publications indicate that machine learning may improve predictive accuracy of cochlear implant outcomes compared to classical statistical methods. However, existing studies are limited in terms of model validation and evaluating factors like sample size on predictive performance. We conduct a thorough examination of machine learning approaches to predict word recognition scores (WRS) measured approximately 12 months after implantation in adults with post-lingual hearing loss. This is the largest retrospective study of cochlear implant outcomes to date, evaluating 2,489 cochlear implant recipients from three clinics. We demonstrate that while machine learning models significantly outperform linear models in prediction of WRS, their overall accuracy remains limited (mean absolute error: 17.9-21.8). The models are robust across clinical cohorts, with predictive error increasing by at most 16% when evaluated on a clinic excluded from the training set. We show that predictive improvement is unlikely to be improved by increasing sample size alone, with doubling of sample size estimated to only increasing performance by 3% on the combined dataset. Finally, we demonstrate how the current models could support clinical decision making, highlighting that subsets of individuals can be identified that have a 94% chance of improving WRS by at least 10% points after implantation, which is likely to be clinically meaningful. We discuss several implications of this analysis, focusing on the need to improve and standardize data collection.

Neural Tissue Degeneration in Rosenthal's Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study

Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Genotype-Phenotype Correlation for Predicting Cochlear Implant Outcome: Current Challenges and Opportunities

The use and utility of cochlear implantation has rapidly increased in recent years as technological advances in the field have expanded both the efficacy and eligible patient population for implantation. This review aims to serve as a general overview of the most common hearing disorders that have favorable auditory outcomes with cochlear implants (CI). Hearing loss in children caused by congenital cytomegalovirus infection, syndromic conditions including Pendred Syndrome, and non-syndromic genetic conditions such as hearing impairment associated with GJB2 mutations have shown to be successfully managed by CI. Furthermore, cochlear implantation provides the auditory rehabilitation for the most common etiology of hearing loss in adults and age-related hearing loss (ARHL) or presbycusis. However, in some cases, cochlear implantation have been associated with some challenges. Regarding implantation in children, studies have shown that sometimes parents seem to have unrealistic expectations regarding the ability of CI to provide auditory rehabilitation and speech improvement. Given the evidence revealing the beneficial effects of early intervention via CI in individuals with hearing disorders especially hearing loss due to genetic etiology, early auditory and genetic screening efforts may yield better clinical outcomes. There is a need to better understand genotype-phenotype correlations and CI outcome, so that effective genetic counseling and successful treatment strategies can be developed at the appropriate time for hearing impaired individuals.