Effect of technological advances on cochlear implant performance in adults

Speech Outcomes of Cochlear Implantation, from 1983 to Present: A Systematic Review

OBJECTIVE

We sought to assess whether the totality of advancements seen in cochlear implant (CI) design and implementation have translated to significant improvements in speech perception scores.

DATABASES REVIEWED

EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials.

METHODS

A systematic review of all English-language studies in peer-reviewed journals from 1946 to August 2022 was performed based on the Cochrane Handbook and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eligible studies were of adult patients who underwent cochlear implantation with Cochlear®, Med-EL, or Advanced Bionics devices with 12 months postoperative sentence recognition testing results. Meta-regression was performed to assess the relationship between speech recognition score and year of implantation. Preimplantation score and unilateral versus bilateral implantation were adjusted for. Subgroup analysis was performed by restricting to studies of <5 years duration and in which outcomes were measured ≤12 months postoperatively to reduce the likelihood of patients with remotely implanted devices having undergone upgrades to more contemporary coding software.

RESULTS

A total of 37 studies met criteria for inclusion, representing CIs implanted between 1983 and 2019. No significant association was identified between median study year and scores on 12-month postoperative sentence recognition testing on any of AzBio in quiet, CNC words, or HINT sentences in quiet. Subgroup analysis showed no difference in outcomes across 15 studies including patients implanted from 2007 to 2019.

CONCLUSION

In the absence of improved CI coding strategies since 2007, speech recognition outcomes in quiet have also not improved significantly since this time.

Psychoacoustic and electroencephalographic responses to changes in amplitude modulation depth and frequency in relation to speech recognition in cochlear implantees

Temporal envelope modulations (TEMs) are one of the most important features that cochlear implant (CI) users rely on to understand speech. Electroencephalographic assessment of TEM encoding could help clinicians to predict speech recognition more objectively, even in patients unable to provide active feedback. The acoustic change complex (ACC) and the auditory steady-state response (ASSR) evoked by low-frequency amplitude-modulated pulse trains can be used to assess TEM encoding with electrical stimulation of individual CI electrodes. In this study, we focused on amplitude modulation detection (AMD) and amplitude modulation frequency discrimination (AMFD) with stimulation of a basal versus an apical electrode. In twelve adult CI users, we (a) assessed behavioral AMFD thresholds and (b) recorded cortical auditory evoked potentials (CAEPs), AMD-ACC, AMFD-ACC, and ASSR in a combined 3-stimulus paradigm. We found that the electrophysiological responses were significantly higher for apical than for basal stimulation. Peak amplitudes of AMFD-ACC were small and (therefore) did not correlate with speech-in-noise recognition. We found significant correlations between speech-in-noise recognition and (a) behavioral AMFD thresholds and (b) AMD-ACC peak amplitudes. AMD and AMFD hold potential to develop a clinically applicable tool for assessing TEM encoding to predict speech recognition in CI users.

Cochlear Implant Outcomes in Patients With Otosclerosis: A Systematic Review

OBJECTIVE

This study aimed to establish hearing outcomes after cochlear implantation in patients with otosclerosis.

MATERIALS AND METHODS

We conducted a systematic review and narrative synthesis. Databases searched were as follows: MEDLINE, PubMed, Embase, Web of Science, Cochrane Collection, and ClinicalTrials.gov . No limits were placed on language or year of publication. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

RESULTS

Searches identified 474 abstracts and 180 full texts, with 68 studies meeting the inclusion criteria and reporting outcomes in a minimum of 481 patients with at least 516 implants. Patient-reported outcome measures (PROMs) were reported in five studies involving 51 patients. Intraoperative adverse events/surgical approach details and preoperative radiological assessment were reported in 46 and 38 studies, respectively. The methodological quality of included studies was modest, predominantly consisting of case reports and noncontrolled case series with small numbers of patients. Most studies were Oxford Centre for Evidence Based Medicine grade IV.

DISCUSSION

Access to good rehabilitation support is essential to achieving the good hearing outcomes and PROMs that can be expected by 12 months after implantation in most cases. There was a significant association between the radiological severity of otosclerosis and an increase in surgical and postoperative complications. Postoperative facial nerve stimulation can occur and may require deactivation of electrodes and subsequent hearing detriment.

CONCLUSIONS

Hearing outcomes are typically good, but patients should be counseled on associated surgical complications that may compromise hearing. Modern diagnostic techniques may help to identify potentially difficult cases to aid operative planning and patient counseling. Further work is needed to characterize PROMs in this population.

Use of Functional Near-Infrared Spectroscopy to Predict and Measure Cochlear Implant Outcomes: A Scoping Review

Outcomes following cochlear implantation vary widely for both adults and children, and behavioral tests are currently relied upon to assess this. However, these behavioral tests rely on subjective judgements that can be unreliable, particularly for infants and young children. The addition of an objective test of outcome following cochlear implantation is therefore desirable. The aim of this scoping review was to comprehensively catalogue the evidence for the potential of functional near infrared spectroscopy (fNIRS) to be used as a tool to objectively predict and measure cochlear implant outcomes. A scoping review of the literature was conducted following the PRISMA extension for scoping review framework. Searches were conducted in the MEDLINE, EMBASE, PubMed, CINAHL, SCOPUS, and Web of Science electronic databases, with a hand search conducted in Google Scholar. Key terms relating to near infrared spectroscopy and cochlear implants were used to identify relevant publications. Eight records met the criteria for inclusion. Seven records reported on adult populations, with five records only including post-lingually deaf individuals and two including both pre- and post-lingually deaf individuals. Studies were either longitudinal or cross-sectional, and all studies compared fNIRS measurements with receptive speech outcomes. This review identified and collated key work in this field. The homogeneity of the populations studied so far identifies key gaps for future research, including the use of fNIRS in infants. By mapping the literature on this important topic, this review contributes knowledge towards the improvement of outcomes following cochlear implantation.

Longitudinal outcomes of cochlear implantation and bimodal hearing in a large group of adults: A multicenter clinical study

OBJECTIVE

To evaluate speech understanding outcomes in a large adult cohort who demonstrated poor hearing performance with well fit hearing aids in the unilateral and bilateral or bimodal listening conditions at preimplant, 3-, 6- and 12-months.

SUBJECTS

Post-linguistically deafened adults (N = 100) with bilateral moderate-to-profound sensorineural hearing loss and limited functional benefit from well fit bilateral hearing aids.

METHOD

A multicenter, prospective, repeated-measures, within-subject controlled study was conducted. All subjects were implanted with a Slim Modiolar cochlear implant and were required to use bimodal stimulation (cochlear implant and hearing aid in contralateral ear) for 6-months postimplant and optionally to 12-months. Evaluations included: speech recognition for monosyllabic consonant-nucleus-consonant (CNC) words in quiet; AzBio sentences in coincident noise (at +5 and +10 dB signal-to-noise ratio (SNR)), in implant ear and bimodal conditions. All speech tests were performed at preimplant and 6-months postimplant for primary endpoint outcomes, and a subset of speech tests at 3- and 12-months.

RESULTS

In the implant ear only, at 3-, 6- and 12-months postimplant, 84%, 93% and 97% of subjects respectively, demonstrated significantly improved monosyllabic word scores in quiet compared to preimplant hearing aid scores (p < 0.05). At 12-months, a mean gain of 51% points, for monosyllabic words and 32% points for sentences in noise was observed (p < 0.001). In the bimodal condition, at 6-months postimplant, 87% of subjects demonstrated significantly improved monosyllabic word scores in quiet compared to preimplant bilateral hearing aid scores (p < 0.05). At 6-months, a mean gain of 40% points, for monosyllabic words was observed (p < 0.001). Speech scores for sentences in noise significantly improved for the bimodal condition at 6- and 12-months (p < 0.001). In addition to speech scores for the implanted ear, bimodal condition scores demonstrated further increments, especially for sentences in noise at 6- and 12-months (p < 0.001).

CONCLUSION

Results support that bimodal hearing is superior to bilateral hearing aids in this cohort of bilateral moderate-to-profound adult hearing aid users. Our study cohort demonstrated significant improvements for speech scores for the cochlear implant (CI) ear only and bimodal conditions compared to the baseline preimplant unilateral and bilateral hearing aid conditions respectively. The greatest gain in performance was in the first three months of device use with incremental improvement through 12 months. These findings indicate that when hearing aids fit to National Acoustics Laboratory (NAL-1) targets do not provide the necessary audibility needed for speech recognition, referral for CI-candidacy evaluation is strongly recommended.

TRIAL REGISTRATION

Clintrial.govNCT03007472. Registered 01/02/2017, https://clinicaltrials.gov/ct2/show/NCT03007472?term=clinical+evaluation+of+the+nucleus+CI532&draw=2&rank=2.

Association of Speech Processor Technology and Speech Recognition Outcomes in Adult Cochlear Implant Users

OBJECTIVE

Determine association of advancements in speech processor technology with improvements in speech recognition outcomes.

STUDY DESIGN

Retrospective cohort.

SETTING

Tertiary referral center.

PATIENTS

Adult unilateral cochlear implant (CI) recipients.

INTERVENTION

Increasing novelty of speech processor defined by year of market availability.

MAIN OUTCOME MEASURES

Consonant-Nucleus-Consonant (CNC) and Hearing in Noise Test (HINT) in quiet.

RESULTS

From 1991 to 2016, 1,111 CNC scores and 1,121 HINT scores were collected from 351 patients who had complete data. Mean post-implantation CNC score was 53.8% and increased with more recent era of implantation (p < 0.001, analysis of variance [ANOVA]). Median HINT score was 87.0% and did not significantly vary with implantation era (p = 0.06, ANOVA). Multivariable generalized linear models were fitted to estimate the effect of speech processor novelty on CNC and HINT scores, each accounting for clustering of scores within patients and characteristics known to influence speech recognition outcomes. Each 5-year increment in speech processor novelty was independently associated with an increase in CNC score by 2.85% (95% confidence limits [CL] 0.26, 5.44%) and was not associated with change in HINT scores (p = 0.30).

CONCLUSION

Newer speech processors are associated with improved CNC scores independent of the year of device implantation and expanding candidacy criteria. The lack of association with HINT scores can be attributed to a ceiling effect, suggesting that HINT in quiet may not be an informative test of speech recognition in the modern CI recipient. The implications of these findings with respect to appropriate interval of speech processor upgrades are discussed.

The efficacy of microphone directionality in improving speech recognition in noise for three commercial cochlear-implant systems

Objectives: To investigate the effect of fixed and adaptive microphone directionality on speech reception threshold (SRT) in noise when compared to omnidirectional mode in unilateral cochlear-implant (CI) use for three different CI systems.Methods: Twenty-four CI recipients with bilateral severe-to-profound hearing loss participated in the study. Eight recipients of each CI system were enrolled, and their SRT in noise was measured when the speech and noise signals were co-located in the front to serve as a baseline. The acute effect of different microphone directionalities on SRT in noise was measured with the noise emanating at 90° in the horizontal plane from the side of the CI sound processor (S0NCI).Results: When compared to the baseline condition, the individual data revealed fairly similar patterns within each CI system. In the S0NCI condition, the average improvement in SRT in noise for fixed and adaptive directionalities over the omnidirectional mode was statistically significant and ranged from 1.2 to 6.0 dB SNR and from 3.7 to 12.7 dB SNR depending on the CI system, respectively.Discussion: Directional microphones significantly improve SRT in noise for all three CI systems. However, relatively large differences were observed in the directional microphone efficacy between CI systems.

Outcomes for a clinically representative cohort of hearing-impaired adults using the Nucleus® CI532 cochlear implant

PURPOSE

Hearing performance data was collected from a large heterogeneous group of subjects implanted with the Cochlear™ Nucleus® CI532 with Slim Modiolar Electrode, for the purposes of postmarket clinical follow-up. Data was analysed for factors which may predict postoperative speech recognition scores.

METHODS

Data was collected retrospectively from five German clinics for 159 subjects from March 2017 to August 2018. Hearing thresholds and recognition scores for monosyllabic words in quiet and sentences in noise were measured preoperatively and at 3 and 6 months postoperatively.

RESULTS

There was a mean gain of 44% points (95% CI 39-49%) at 6 months in monosyllable scores in quiet for implanted ears. Preoperative hearing thresholds in implant ears increased systematically with decreasing age; however, younger subjects had better baseline monosyllable scores with hearing aids compared with older subjects. Baseline performance alone explained 14% of the variation in postoperative scores. Residual hearing was preserved on average to within 22 dB at 250 Hz and 30 dB at 500 Hz of preoperative levels.

CONCLUSIONS

In a large and varied cohort of routinely treated hearing-impaired adults, speech recognition with the CI532 for German monosyllabic words in quiet at 6 months was equivalent to performance reported at one year or more in other published studies. Although younger subjects had poorer preoperative pure-tone thresholds, they had better preoperative word recognition scores compared with older subjects, and also had higher post implant scores. Further research is required to identify if this phenomenon is just applicable to German health system assessment and referral practices.

Development of auditory and language skills in children using cochlear implants with two signal processing strategies

Introduction

The increase in the spectral information offered by the sound processing strategy HiRes 120 has led to great expectations for the pediatric population. Due to a shorter duration of auditory deprivation and higher neural plasticity, children could benefit more substantially from the spectral information of this sound processing strategy.

Objective

To compare auditory and language skills in Brazilian children with cochlear implants using the HiRes and HiRes 120 sound processing strategies.

Methods

Thirty children, aged 1–3 years, with congenital hearing loss, were divided into two groups, according to the signal processing strategy adjusted at the time of the cochlear implant activation. The assessed children were matched according to chronological age and the time of the cochlear implant use. The auditory and language skills were evaluated longitudinally through the Infant-Toddler Meaningful Auditory Integration Scale and Production Infant Scale Evaluation, carried out before surgery, and 3, 6 and 12 months after device implantation. The Mann–Whitney test was applied for the comparison between the two groups with a 5% significance level.

Results

The findings indicated development of hearing and language skills in the first year of cochlear implant use; however, there was no statistically significant difference in the evolution of such skills due to the adjusted processing strategy in the activation of the cochlear implant electrodes.

Conclusion

The development of auditory and language skills in the assessed children was similar during the entire study period, regardless of which signal processing strategy was used.

Functional near-infrared spectroscopy as a tool for assessing speech and spoken language processing in pediatric and adult cochlear implant users

Much of what is known about the course of auditory learning in following cochlear implantation is based on behavioral indicators that users are able to perceive sound. Both prelingually deafened children and postlingually deafened adults who receive cochlear implants display highly variable speech and language processing outcomes, although the basis for this is poorly understood. To date, measuring neural activity within the auditory cortex of implant recipients of all ages has been challenging, primarily because the use of traditional neuroimaging techniques is limited by the implant itself. Functional near-infrared spectroscopy (fNIRS) is an imaging technology that works with implant users of all ages because it is non-invasive, compatible with implant devices, and not subject to electrical artifacts. Thus, fNIRS can provide insight into processing factors that contribute to variations in spoken language outcomes in implant users, both children and adults. There are important considerations to be made when using fNIRS, particularly with children, to maximize the signal-to-noise ratio and to best identify and interpret cortical responses. This review considers these issues, recent data, and future directions for using fNIRS as a tool to understand spoken language processing in children and adults who hear through a cochlear implant.

Indication of direct acoustical cochlea stimulation in comparison to cochlear implants

The new implantable hearing system Codacs™ was designed to close the treatment gap between active middle ear implants and cochlear implants in cases of severe-to-profound mixed hearing loss. The Codacs™ actuator is attached to conventional stapes prosthesis during the implantation and thereby provides acoustical stimulation through a stapedotomy to the cochlea. Cochlear implants (CIs) on the other hand are an established treatment option for profoundly deaf patients including mixed hearing losses that are possible candidates for the Codacs™. In this retrospective study, we compared the clinical outcome of 25 patients with the Codacs™ (≥3 month post-activation) to 54 CI patients (two years post-activation) with comparable pre-operative bone conduction (BC) thresholds that were potential candidates for both categories of devices. The word recognition score (Freiburg monosyllables test) in quiet was significantly (p < 0.05) better in the Codacs™ than in the corresponding CI patients for average pre-operative bone conduction below 60 dB HL and equal in patients with a pre-operative BC PTA between 60 and 70 dB HL. Speech in noise intelligibility (HSM sentences test at +10 dB SNR) was significantly (p < 0.001) better in Codacs™ (80% median) than in CI patients (25% median) in all tested groups. Our results indicate for patients with sufficient cochlear reserve that speech intelligibility in noise with the Codacs™ hearing implant is significantly better than with a CI. Further, results in Codacs™ were better predictable, encouraging the extension of the indication to patients with less cochlear reserve than reported here.

Speech intelligibility in deaf children after long-term cochlear implant use

PURPOSE

This study investigated long-term speech intelligibility outcomes in 63 prelingually deaf children, adolescents, and young adults who received cochlear implants (CIs) before age 7 (M = 2;11 [years;months], range = 0;8-6;3) and used their implants for at least 7 years (M = 12;1, range = 7;0-22;5).

METHOD

Speech intelligibility was assessed using playback methods with naïve, normal-hearing listeners.

RESULTS

Mean intelligibility scores were lower than scores obtained from an age- and nonverbal IQ-matched, normal-hearing control sample, although the majority of CI users scored within the range of the control sample. Our sample allowed us to investigate the contribution of several demographic and cognitive factors to speech intelligibility. CI users who used their implant for longer periods of time exhibited poorer speech intelligibility scores. Crucially, results from a hierarchical regression model suggested that this difference was due to more conservative candidacy criteria in CI users with more years of use. No other demographic variables accounted for significant variance in speech intelligibility scores beyond age of implantation and amount of spoken language experience (assessed by communication mode and family income measures).

CONCLUSION

Many factors that have been found to contribute to individual differences in language outcomes in normal-hearing children also contribute to long-term CI users' ability to produce intelligible speech.

Long term results in late implanted adolescent and adult CI recipients

The aim of the present study is to assess long-term outcomes of CI in prelingual deafened adolescents and adults, describing, where present, differences in performance, self perceived benefit and highlighting specific characteristics. Twenty-three patients were enrolled: 10 adolescents, 13 young adults. Each patient underwent speech perception/language development, psychological evaluation and structured interviews on self perception concerning CI. 70 % adolescents and 100 % adults used their cochlear implant for most of the day; two adolescents were partial users and one was a non-user. Adolescents' average word recognition and comprehension scores improved respectively from 7 to 29.8 % (p = 0.01) and 3 to 26 % (p = 0.1). Adults' average scores improved significantly from 1.5 to 41.9 % (p = 0.01) and from 18.5 to 52.7% (p = 0.001), respectively. None of the subjects showed a linguistic age adequate to the chronological one: average linguistic age was 7.6 years for adolescents and 19.3 for adults. Structured interviews showed improvement in self-esteem. Adults and most adolescents were fully or moderately satisfied with their implant. Cochlear implantation can be considered a valid option for the rehabilitation of highly motivated and well-selected pre-lingual deafened adolescents and adults. Although there is a substantial variability in both groups of patients and language skills are only marginally influenced by CI, there is still a significant improvement in speech perception. CI was described by both groups as having had a positive impact on their lives; nevertheless adolescents were the ones with a tendency to under-use CI, even those with better hearing outcomes.