Systematic review of compound action potentials as predictors for cochlear implant performance

Cochlear health in a cohort of cochlear implant users carrying the p.Pro51Ser variant in the COCH gene (DFNA9): A cross-sectional study evaluating the changes in the electrically evoked compound action potential (eCAP)

The present study focuses on DFNA9, an autosomal dominant disorder caused by pathogenic variants in the COCH gene. These mutations induce the formation of aggregates that are toxic to the fibrocytes in the extracellular matrix, ultimately leading to degeneration of spiral ganglion neurons (SGNs), which are crucial for transmitting auditory signals from the cochlea to the brain. An important tool for evaluating the function of the SGNs, which are the target cells of a cochlear implant (CI), is the electrically evoked compound action potential (eCAP). Therefore, the main objective is to evaluate the eCAP to describe the function of the SGNs and study cochlear health in CI patients with DFNA9. For this reason, we included 15 carriers of the p.Pro51Ser variant in the COCH gene who received a MED-EL CI (DFNA9 group) and 15 matched control CI subjects without DFNA9 to compare the impedances and subsequently the threshold, amplitude and slope of the eCAP amplitude growth function (AGF). These parameters were evaluated from intraoperative autoART recordings (MED-EL) during CI surgery. Matching of the two groups was based on sex, age at implantation, duration of deafness, and type of implant. The first results, regarding the difference in impedance between DFNA9 and non-DFNA9 patients, show a significant interaction between time and group in the middle and basal electrodes, indicating that electrode impedances were similar in the early phase after implantation between the two groups, but increased significantly more for the DFNA9 group up to one year after implantation. Secondly, the results show that the success rate (present or absent) to record eCAP responses is lower in the DNFA9 group: eCAPs were detectable in 75.5 % of the intraoperative measurements (145/192) in comparison to 96.9 % (186/192) in the group without DFNA9. ECAP absence in the DFNA9 group was observed across the whole electrode array, but more pronounced in the basal region (channels 11 and 12). Additionally, comparing the parameters of the AGF, the maximum eCAP amplitude was consistently smaller and the AGF slope consistently shallower for the DFNA9 group compared to the control group throughout the entirety of the electrode array. Finally, the eCAP thresholds in patients with DFNA9 were higher compared to those in the control patients for all cochlear locations. To our knowledge, this is the first study to investigate the eCAP measurements in patients with DFNA9. As proven in the literature, eCAP measures correlate well with the health and survival of SGC. This means that the results of our study predominantly suggest that DFNA9 leads to an even stronger reduction in excitability and neuronal health than seen in other causes of deafness.

ECAP correlation with speech recognition performance - new predictory function in rehabilitation of cochlear implant recipients?

<b>Introduction:</b> Despite well-established qualification criteria and pre-operation tests, there is still uncertainty about post-implantation performance in CI patients. One of the most interesting factors that affect the outcome is the survivability and function of cochlear nerve endings. ECAP (Evoked Compound Action Potential) is one of the tools that might be useful in the prediction of rehabilitation outcomes. Speech audiometry is one of the most commonly used and established performance tests. The study hypothesis is that there might be a correlation between ECAP values and speech audiometry results obtained over time.<b>Aim:</b> The aim was to check if changes within postop ECAP values correspond tochanges in speech intelligibility.<b>Materials and methods:</b> The study was designed as a retrospective observational one. Data was evaluated on a selected group of patients, with no blinding or control group. The study group consisted of 25 adult cochlear implant recipients, all with Cochlear devices, implanted at the Department of Otolaryngology of the Medical University of Bialystok, Poland, between 2016 and 2020. Data included ECAP measurements and speech audiometry results obtained during the first year of rehabilitation. The statistical analysis of the significance of data change over time and its correlation was performed.<b>Results:</b> Change of data over time was significant (P<0.05) for almost all data groups but it did not translates to the correlation of speech and ECAP.<b>Conclusions:</b> There is no statistically confirmed evidence suggesting that obtaining speech intelligibility is connected with change in ECAP values, which requires further research.

Leveraging eCAP thresholds in a logistic model to predict speech outcomes after implantation in anomalous cochlea

BACKGROUND

Pediatric cochlear implant (CI) recipients with cochlear malformations face challenges due to variable speech recognition outcomes.

AIMS/OBJECTIVES

This study assesses the predictive value of intraoperative electrically evoked compound action potential (eCAP) thresholds, residual hearing, age at implantation, Intelligent Quotient (IQ), and malformation type for speech recognition outcomes.

MATERIAL AND METHODS

A prospective cohort of 52 children (aged 1-4 years) with cochlear malformations who underwent CI between 2016 and 2024 was analyzed. Intraoperative eCAP thresholds were recorded, and disyllable word recognition scores (WRS) were evaluated 24 months postoperatively.

RESULTS

Patients included incomplete partition (IP-II, 46.2%), cochlear hypoplasia (30.8%), IP-I (13.5%), and common cavity (9.6%). IP-II cases had higher mean eCAP thresholds (18.85 µV) compared to cochlear hypoplasia and common cavity cases. Higher eCAP thresholds correlated with better WRS outcomes (p < 0.001). Logistic regression revealed eCAP thresholds, residual hearing, age, IQ, and malformation type as significant predictors, with an AUC of 0.92.

CONCLUSIONS AND SIGNIFICANCE

Intraoperative eCAP thresholds and residual hearing strongly predict auditory outcomes in children with cochlear malformations. Tailored CI strategies based on individual profiles can optimize speech recognition outcomes.

Barriers to Early Progress in Adult Cochlear Implant Outcomes

OBJECTIVES

Adult cochlear implant (CI) recipients obtain varying levels of speech perception from their device. Adult CI users adapt quickly to their CI if they have no peripheral "bottom-up" or neurocognitive "top-down" limiting factors. Our objective here was to understand the influence of limiting factors on the progression of sentence understanding in quiet and in noise, initially and over time. We hypothesized that the presence of limiting factors, detected using a short test battery, would predictably influence sentence recognition with practical consequences. We aimed to validate the test battery by comparing the presence of limiting factors and the success criteria of >90% sentence understanding in quiet 1 month after activation.

DESIGN

The study was a single-clinic, cross-sectional, retrospective design incorporating 32 adult unilateral Nucleus CI users aged 27 to 90 years (mean = 70, SD = 13.5). Postoperative outcome was assessed through sentence recognition scores in quiet and in varying signal to noise ratios at 1 day, 1 to 2 months, and up to 2 years. Our clinic's standard test battery comprises physiological and neurocognitive measures. Physiological measures included electrically evoked compound action potentials for recovery function, spread of excitation, and polarity effect. To evaluate general cognitive function, inhibition, and phonological awareness, the Montreal Cognitive Assessment screening test, the Stroop Color-Word Test, and tests 3 and 4 of the French Assessment of Reading Skills in Adults over 16 years of age, respectively were performed. Physiological scores were considered abnormal, and therefore limiting, when total neural recovery periods and polarity effects, for both apical and basal electrode positions, were >1.65 SDs from the population mean. A spread of excitation of >6 electrode units was also considered limiting. For the neurocognitive tests, scores poorer than 1.65 SDs from published normal population means were considered limiting.

RESULTS

At 1 month, 13 out of 32 CI users scored ≥90% sentence recognition in quiet with no significant dependence on age. Subjects with no limiting peripheral or neurocognitive factors were 8.5 times more likely to achieve ≥90% score in quiet at 1 month after CI switch-on ( p = 0.010). In our sample, we detected 4 out of 32 cases with peripheral limiting factors that related to neural health or poor electrode-neural interface at both apical and basal positions. In contrast, neurocognitive limiting factors were identified in 14 out of 32 subjects. Early sentence recognition scores were predictive of long-term sentence recognition thresholds in noise such that limiting factors appeared to be of continuous influence.

CONCLUSIONS

Both peripheral and neurocognitive processing factors affect early sentence recognition after CI activation. Peripheral limiting factors may have been detected less often than neurocognitive limiting factors because they were defined using sample-based criteria versus normal population-based criteria. Early performance was generally predictive of long-term performance. Understanding the measurable covariables that limit CI performance may inform follow-up and improve counseling. A score of ≥90% for sentence recognition in quiet at 1 month may be used to define successful progress; whereas, lower scores indicate the need for diagnostic testing and ongoing rehabilitation. Our findings suggest that sentence test scores as early as 1 day after activation can provide vital information for the new CI user and indicate the need for rehabilitation follow-up.

Prognostic Value of Electrophysiological and MRI Findings for Pediatric Cochlear Implant Outcomes: A Systematic Review

PURPOSE

Magnetic resonance imaging (MRI), electric compound action potential (eCAP), and electric auditory brainstem response (eABR) are among the routine assessments performed before and/or after cochlear implantation. The objective of this review was to systematically summarize and critically appraise existing evidence of the prognostic value of eCAP, eABR, and MRI for predicting post-cochlear implant (CI) speech perception outcomes in children, with a particular focus on the lesion site.

METHOD

The present systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement. Three electronic databases (ProQuest, PubMed, and Scopus) were searched with no restrictions on language, publication status, or year of publication. Studies on children identified with sensorineural hearing loss, auditory neuropathy spectrum disorder, cochlear nerve deficiency, or cochleovestibular nerve abnormalities reporting the relevance of eCAP, eABR, and/or MRI results to CI speech perception outcomes were included. The literature search yielded 1,887 publications. Methodological quality and strength of evidence were assessed by the Crowe Critical Appraisal Tool and the Grading of Recommendations Assessment, Development, and Evaluation tool, respectively.

RESULTS

Of the 25 included studies, the relevance of eCAP, eABR, and/or MRI findings to post-CI speech perception outcomes was reported in 10, 11, and 11 studies, respectively. The studies were strongly in support of the prognostic value of eABR and MRI for CI outcomes. However, the relevance of eCAP findings to speech perception outcomes was uncertain.

CONCLUSION

Despite the promising findings, caution is warranted in interpreting them due to the observational and retrospective design of the included studies, as well as the heterogeneity of the population and the limited control of confounding factors within these studies.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.26169859.

Self-Assessment of Cochlear Health by New Cochlear Implant Recipients: Daily Impedance, Electrically Evoked Compound Action Potential and Electrocochleography Measurements Over the First Three Postoperative Months

HYPOTHESES

In newly implanted cochlear implant (CI) users, electrically evoked compound action (eCAPs) and electrocochleography (ECochGs) will remain stable over time. Electrode impedances will increase immediately postimplantation due to the initial inflammatory response, before decreasing after CI switch-on and stabilizing thereafter.

BACKGROUND

The study of cochlear health (CH) has several applications, including explaining variation in CI outcomes, informing CI programming strategies, and evaluating the safety and efficacy of novel biological treatments for hearing loss. Very early postoperative CH patterns have not previously been intensively explored through longitudinal daily testing. Thanks to technological advances, electrode impedances, eCAPs, and ECochGs can be independently performed by CI users at home to monitor CH over time.

METHODS

A group of newly implanted CI users performed daily impedances, eCAPs, and ECochGs for 3 months at home, starting from the first day postsurgery (N = 7) using the Active Insertion Monitoring system by Advanced Bionics.

RESULTS

Measurement validity of 93.5, 93.0, and 81.6% for impedances, eCAPs, and ECochGs, respectively, revealed high participant compliance. Impedances increased postsurgery before dropping and stabilizing after switch-on. eCAPs showed good stability, though statistical analyses revealed a very small but significant increase in thresholds over time. Most ECochG thresholds did not reach the liberal signal-to-noise criterion of 2:1, with low threshold stability over time.

CONCLUSION

Newly implanted CI recipients can confidently and successfully perform CH recordings at home, highlighting the valuable role of patients in longitudinal data collection. Electrode impedances and eCAPs are promising objective measurements for evaluating CH in newly implanted CI users.

Intraoperative Compound Action Potentials as a Predictor of Postoperative Cortical Auditory Evoked Potentials in Cochlear Implant Users

INTRODUCTION

Electrically evoked cortical auditory evoked potentials (ECAEPs) are central brain responses to auditory stimuli that correlate with postoperative cochlear implant (CI) hearing outcomes. They differ from electrically evoked compound action potentials (ECAPs) which are peripheral responses that can be elicited intraoperatively and may also predict CI hearing outcomes. It is not known to what degree ECAP and ECAEP responses are associated with each other. Such a correlation, if present, may allow for an earlier and more accurate prediction of postoperative hearing outcomes.

METHODS

This retrospective study involved 42 adult CI users. Threshold levels and amplitude growth function slopes of intraoperative ECAPs were compared to the latencies and peak-to-peak amplitudes of postoperative ECAEP responses at three different cochlear electrode array sites (apical, medial, and basal).

RESULTS

A weak positive relationship was found between intraoperative ECAP thresholds and ECAEP N1-P2 peak-to-peak amplitude (r = 0.301, p = 0.005). Time between ECAP and ECAEP measurements was weakly correlated with P1-N1 peak-to-peak amplitude (r = 0.321, p = 0.002) and ECAEP N1-P2 peak-to-peak amplitude (r = 0.340, p = 0.001). ECAP amplitude growth function slopes varied by electrode location (χ2 = 26.701, df = 2, p = 0. 000002).

CONCLUSION

These results suggest that intraoperative ECAP responses do not robustly predict postoperative ECAEP responses, providing caution against the use of ECAPs as a predictive tool for CI hearing outcomes.

INTRODUCTION

Electrically evoked cortical auditory evoked potentials (ECAEPs) are central brain responses to auditory stimuli that correlate with postoperative cochlear implant (CI) hearing outcomes. They differ from electrically evoked compound action potentials (ECAPs) which are peripheral responses that can be elicited intraoperatively and may also predict CI hearing outcomes. It is not known to what degree ECAP and ECAEP responses are associated with each other. Such a correlation, if present, may allow for an earlier and more accurate prediction of postoperative hearing outcomes.

METHODS

This retrospective study involved 42 adult CI users. Threshold levels and amplitude growth function slopes of intraoperative ECAPs were compared to the latencies and peak-to-peak amplitudes of postoperative ECAEP responses at three different cochlear electrode array sites (apical, medial, and basal).

RESULTS

A weak positive relationship was found between intraoperative ECAP thresholds and ECAEP N1-P2 peak-to-peak amplitude (r = 0.301, p = 0.005). Time between ECAP and ECAEP measurements was weakly correlated with P1-N1 peak-to-peak amplitude (r = 0.321, p = 0.002) and ECAEP N1-P2 peak-to-peak amplitude (r = 0.340, p = 0.001). ECAP amplitude growth function slopes varied by electrode location (χ2 = 26.701, df = 2, p = 0. 000002).

CONCLUSION

These results suggest that intraoperative ECAP responses do not robustly predict postoperative ECAEP responses, providing caution against the use of ECAPs as a predictive tool for CI hearing outcomes.

ART and AutoART ECAP measurements and cochlear nerve anatomy as predictors in adult cochlear implant recipients

PURPOSE

The purpose of this retrospective study is to compare the results of electrically evoked compound action potential (ECAP) measurements using automatic auditory response telemetry (AutoART) with those obtained by ART in adults. The study also aimed to evaluate the predictive value of intraoperative ART and AutoART ECAPs for speech intelligibility (SI) and hearing success (HS), and to determine if cochlear nerve (CN) cross-sectional area (CSA) obtained preoperatively by magnetic resonance imaging (MRI) scans could predict ART and AutoART ECAPs and SI and HS outcome.

METHODS

The study analyzed and correlated ART and AutoART ECAP thresholds at electrodes E2, E6, and E10, as well as averaged ECAP thresholds over electrodes E1-E12, using data from 32 implants. Correlations were also examined for ART and AutoART ECAP slopes. In addition, averaged ART and AutoART ECAP thresholds and slopes over all 12 electrodes for each participant were correlated with CN CSA measured from MRI sequences. SI of the monosyllabic Freiburg Speech Test at 65 dB sound pressure level was examined along with averaged ART and AutoART thresholds and slopes over all 12 electrodes. A parallel analysis was performed for HS, derived from the difference between baseline and 6-month SI. Finally, correlations between CN CSA and SI, as well as CN CSA and HS were examined.

RESULTS

The results of the study showed a significant positive correlation between ART and AutoART ECAP thresholds and as well as slopes for E2, E6, E10 and averaged thresholds and slopes of E1-E12. However, no significant correlation was observed between ART and AutoART averaged ECAP thresholds and slopes and either SI and HS or CN CSA. Furthermore, no significant correlation was found between CN CSA and SI and HS.

CONCLUSION

While AutoART is a reliable and safe program for measuring ECAPs in adults, the study found no preoperative prognostic information on intraoperative ECAP results using parameters extracted from current MRI sequences or pre-/intraoperative information on subsequent hearing outcome using ECAP and CN CSA.

Correlation between neural response telemetry measurements and fitting levels

INTRODUCTION

The neural response telemetry (NRT) is a standard procedure in cochlear implantation mostly used to determine the functionality of implanted device and to check auditory nerve responds to the stimulus. Correlation between NRT measurements and subjective threshold (T) and maximum comfort (C) levels has been reported but results are inconsistent, and it is still not clear which of the NRT measurements could be the most useful in predicting fitting levels.

PURPOSE

In our study we aimed to investigate which NRT measurement corresponds better to fitting levels. Impedance (IMP), Evoked Action Potential (ECAP) threshold and amplitude growth function (AGF) slope values were included in the study. Also, we tried to identify cochlear area at which the connection between NRT measurements and fitting levels would be the most pronounced.

MATERIALS AND METHODS

Thirty-one children implanted with Cochlear device were included in this retrospective study. IMP, ECAP thresholds and AGF were obtained intra-operatively and 12 months after surgery at electrodes 5, 11 and 19 as representative for each part of cochlea. Subjective T and C levels were obtained 12 months after the surgery during cochlear fitting.

RESULTS

ECAP thresholds obtained 12 months after surgery showed statistically significant correlation to both T and C levels at all 3 selected electrodes. IMP correlated with C levels while AGF showed tendency to correlate with T levels. However, these correlations were not statistically significant for all electrodes.

CONCLUSION

ECAP threshold measurements correlated to T and C values better than AGF slope and IMP. Measurements obtained twelve months after surgery seems to be more predictive of T and C values compared to intra-operative measurements. The best correlation between ECAP threshold and T and C values was found at electrode 11 suggesting NRT measurements at mid-portion cochlear region to be the most useful in predicting fitting levels.

The Relationship Between Cochlear Implant Speech Perception Outcomes and Electrophysiological Measures of the Electrically Evoked Compound Action Potential

OBJECTIVE

This study assessed the relationship between electrophysiological measures of the electrically evoked compound action potential (eCAP) and speech perception scores measured in quiet and in noise in postlingually deafened adult cochlear implant (CI) users. It tested the hypothesis that how well the auditory nerve (AN) responds to electrical stimulation is important for speech perception with a CI in challenging listening conditions.

DESIGN

Study participants included 24 postlingually deafened adult CI users. All participants used Cochlear Nucleus CIs in their test ears. In each participant, eCAPs were measured at multiple electrode locations in response to single-pulse, paired-pulse, and pulse-train stimuli. Independent variables included six metrics calculated from the eCAP recordings: the electrode-neuron interface (ENI) index, the neural adaptation (NA) ratio, NA speed, the adaptation recovery (AR) ratio, AR speed, and the amplitude modulation (AM) ratio. The ENI index quantified the effectiveness of the CI electrodes in stimulating the targeted AN fibers. The NA ratio indicated the amount of NA at the AN caused by a train of constant-amplitude pulses. NA speed was defined as the speed/rate of NA. The AR ratio estimated the amount of recovery from NA at a fixed time point after the cessation of pulse-train stimulation. AR speed referred to the speed of recovery from NA caused by previous pulse-train stimulation. The AM ratio provided a measure of AN sensitivity to AM cues. Participants' speech perception scores were measured using Consonant-Nucleus-Consonant (CNC) word lists and AzBio sentences presented in quiet, as well as in noise at signal-to-noise ratios (SNRs) of +10 and +5 dB. Predictive models were created for each speech measure to identify eCAP metrics with meaningful predictive power.

RESULTS

The ENI index and AR speed individually explained at least 10% of the variance in most of the speech perception scores measured in this study, while the NA ratio, NA speed, the AR ratio, and the AM ratio did not. The ENI index was identified as the only eCAP metric that had unique predictive power for each of the speech test results. The amount of variance in speech perception scores (both CNC words and AzBio sentences) explained by the eCAP metrics increased with increased difficulty under the listening condition. Over half of the variance in speech perception scores measured in +5 dB SNR noise (both CNC words and AzBio sentences) was explained by a model with only three eCAP metrics: the ENI index, NA speed, and AR speed.

CONCLUSIONS

Of the six electrophysiological measures assessed in this study, the ENI index is the most informative predictor for speech perception performance in CI users. In agreement with the tested hypothesis, the response characteristics of the AN to electrical stimulation are more important for speech perception with a CI in noise than they are in quiet.

Indicators for cochlear implantation in children with auditory neuropathy spectrum disorder: A systematic review

PURPOSE

ANSD refers to a group of auditory diseases demonstrating intact outer hair cells and desynchronized neural firings of the auditory nerve. A cochlear implant is a promising intervention strategy for severe to profound sensorineural hearing loss (SNHL). However, due to its variable outcomes in children with ANSD, a consensus has yet to be reached on its performance. This study aimed to review the literature to determine the efficacy of cochlear implants in children with ANSD and to determine prognostic indicators. The study identifies the pre-operative and post-operative predictors of success for CI in children with ANSD.

METHOD

The review was carried out using PRISMA guidelines. This resulted in 9630 topic-related articles. Among these, 17 articles met the inclusion and exclusion criteria that were included for the study. The quality and potential risks associated with each article were evaluated using the quality impact assessment protocol (QUIPS) tool.

RESULTS

A review of 17 articles was conducted to highlight these predictors. Most selected studies included case reports, case series, cohorts, and comparisons between children with ANSD and SNHL. Assessment of study quality reported an overall low risk of bias. The overall result showed cochlear implant would be an effective option for children with ANSD. However, there are specific prognostic indicators about which clinician needs to be aware before recommending CI for children with ANSD. Our review study identified a set of pre-operative and post-operative indicators that predicted speech and auditory performance and gave some insight into the lesion site in ANSD individuals.

CONCLUSION

This review concludes CI is an effective option for children with ANSD. However, before recommending CI, a detailed assessment is required from different perspectives, which could serve as predictors of postoperative outcomes. This review highlights the need to include more precise tools, such as genetic testing to describe the lesion site to choose the most appropriate management strategy for children with ANSD. Knowledge about the prognostic indicators and the effective assessment protocols would help clinicians for the better candidacy selection.

Robot-Assisted and Manual Cochlear Implantation: An Intra-Individual Study of Speech Recognition

Cochlear implantation (CI) allows rehabilitation for patients with severe to profound hearing impairment. Although the use of a robotic assistant provides technical assistance to the surgeon, the assessment of the impact of its use on auditory outcomes remains uncertain. We aim to compare the hearing results of patients who underwent bilateral cochlear implantation; one side was performed with manual insertion and the other side with robot-assisted insertion. The electrode array intrascalar positioning and the surgery duration were also studied. This retrospective intra-individual study involved 10 patients who underwent bilateral cochlear implantation. The study included two infants and eight adults. The unique composition of this cohort enabled us to utilize each patient as their own control. Regarding speech disyllabic recognition, pure tone average, ECAP, ratio of array translocation, basilar membrane rupture, and percentage of translocated electrodes, there was no difference between manual and robot-assisted CI groups. This study is the first to compare intra-individual hearing performance after cochlear implantation, either manually or robot-assisted. The number of patients and the time delay between manual and robotic implantation may have led to a lack of power, but there was no apparent difference in hearing performance between manual and robotic implantation.

Factors influencing the relationship between cochlear health measures and speech recognition in cochlear implant users

Background

One factor which influences the speech intelligibility of cochlear implant (CI) users is the number and the extent of the functionality of spiral ganglion neurons (SGNs), referred to as "cochlear health." To explain the interindividual variability in speech perception of CI users, a clinically applicable estimate of cochlear health could be insightful. The change in the slope of the electrically evoked compound action potentials (eCAP), amplitude growth function (AGF) as a response to increased interphase gap (IPG) (IPGE_slope) has been introduced as a potential measure of cochlear health. Although this measure has been widely used in research, its relationship to other parameters requires further investigation.

Methods

This study investigated the relationship between IPGE_slope, demographics and speech intelligibility by (1) considering the relative importance of each frequency band to speech perception, and (2) investigating the effect of the stimulus polarity of the stimulating pulse. The eCAPs were measured in three different conditions: (1) Forward masking with anodic-leading (FMA) pulse, (2) Forward masking with cathodic-leading (FMC) pulse, and (3) with alternating polarity (AP). This allowed the investigation of the effect of polarity on the diagnosis of cochlear health. For an accurate investigation of the correlation between IPGE_slope and speech intelligibility, a weighting function was applied to the measured IPGE_slopes on each electrode in the array to consider the relative importance of each frequency band for speech perception. A weighted Pearson correlation analysis was also applied to compensate for the effect of missing data by giving higher weights to the ears with more successful IPGE_slope measurements.

Results

A significant correlation was observed between IPGE_slope and speech perception in both quiet and noise for between-subject data especially when the relative importance of frequency bands was considered. A strong and significant correlation was also observed between IPGE_slope and age when stimulation was performed with cathodic-leading pulses but not for the anodic-leading pulse condition.

Conclusion

Based on the outcome of this study it can be concluded that IPGE_slope has potential as a relevant clinical measure indicative of cochlear health and its relationship to speech intelligibility. The polarity of the stimulating pulse could influence the diagnostic potential of IPGE_slope.

Speech Perception Performance in Cochlear Implant Recipients Correlates to the Number and Synchrony of Excited Auditory Nerve Fibers Derived From Electrically Evoked Compound Action Potentials

OBJECTIVES

Many studies have assessed the performance of individuals with cochlear implants (CIs) with electrically evoked compound action potentials (eCAPs). These eCAP-based studies have focused on the amplitude information of the response, without considering the temporal firing properties of the excited auditory nerve fibers (ANFs), such as neural latency and synchrony. These temporal features have been associated with neural health in animal studies and, consequently, could be of importance to clinical CI outcomes. With a deconvolution method, combined with a unitary response, the eCAP can be mathematically unraveled into the compound discharge latency distribution (CDLD). The CDLD reflects both the number and the temporal firing properties of excited ANFs. The present study aimed to determine to what extent the CDLD derived from intraoperatively recorded eCAPs is related to speech perception in individuals with CIs.

DESIGN

This retrospective study acquired data on monosyllabic word recognition scores and intraoperative eCAP amplitude growth functions from 124 adult patients with postlingual deafness that received the Advanced Bionics HiRes 90K device. The CDLD was determined for each recorded eCAP waveform by deconvolution. Each of the two Gaussian components of the CDLD was described by three parameters: the amplitude, the firing latency (the average latency of each component of the CDLD), and the variance of the CDLD components (an indication of the synchronicity of excited ANFs). Apart from these six CDLD parameters, the area under the CDLD curve (AUCD) and the slope of the AUCD growth function were determined as well. The AUCD was indicative of the total number of excited ANFs over time. The slope of the AUCD growth function indicated the increases in the number of excited ANFs with stimulus level. Associations between speech perception and each of these eight CDLD-related parameters were investigated with linear mixed modeling.

RESULTS

In individuals with CIs, larger amplitudes of the two CDLD components, greater AUCD, and steeper slopes of the AUCD growth function were all significantly associated with better speech perception. In addition, a smaller latency variance in the early CDLD component, but not in the late, was significantly associated with better speech recognition scores. Speech recognition was not significantly dependent on CDLD latencies. The AUCD and the slope of the AUCD growth function provided a similar explanation of the variance in speech perception (R 2 ) as the eCAP amplitude, the slope of the amplitude growth function, the amplitude, and variance of the first CDLD component.

CONCLUSION

The results demonstrate that both the number and the neural synchrony of excited ANFs, as revealed by CDLDs, are indicative of postimplantation speech perception in individuals with a CI. Because the CDLD-based parameters yielded a higher significance than the eCAP amplitude or the AGF slope, the authors conclude that CDLDs can serve as a clinical predictor of the survival of ANFs and that they have predictive value for postoperative speech perception performance. Thus, it would be worthwhile to incorporate the CDLD into eCAP measures in future clinical applications.

Cochlear Health and Cochlear-implant Function

The cochlear implant (CI) is widely considered to be one of the most innovative and successful neuroprosthetic treatments developed to date. Although outcomes vary, CIs are able to effectively improve hearing in nearly all recipients and can substantially improve speech understanding and quality of life for patients with significant hearing loss. A wealth of research has focused on underlying factors that contribute to success with a CI, and recent evidence suggests that the overall health of the cochlea could potentially play a larger role than previously recognized. This article defines and reviews attributes of cochlear health and describes procedures to evaluate cochlear health in humans and animal models in order to examine the effects of cochlear health on performance with a CI. Lastly, we describe how future biologic approaches can be used to preserve and/or enhance cochlear health in order to maximize performance for individual CI recipients.

The Acoustic Change Complex Compared to Hearing Performance in Unilaterally and Bilaterally Deaf Cochlear Implant Users

OBJECTIVES

Clinical measures evaluating hearing performance in cochlear implant (CI) users depend on attention and linguistic skills, which limits the evaluation of auditory perception in some patients. The acoustic change complex (ACC), a cortical auditory evoked potential to a sound change, might yield useful objective measures to assess hearing performance and could provide insight in cortical auditory processing. The aim of this study is to examine the ACC in response to frequency changes as an objective measure for hearing performance in CI users.

DESIGN

Thirteen bilaterally deaf and six single-sided deaf subjects were included, all having used a unilateral CI for at least 1 year. Speech perception was tested with a consonant-vowel-consonant test (+10 dB signal-to-noise ratio) and a digits-in-noise test. Frequency discrimination thresholds were measured at two reference frequencies, using a 3-interval, 2-alternative forced-choice, adaptive staircase procedure. The two reference frequencies were selected using each participant's frequency allocation table and were centered in the frequency band of an electrode that included 500 or 2000 Hz, corresponding to the apical electrode or the middle electrode, respectively. The ACC was evoked with pure tones of the same two reference frequencies with varying frequency increases: within the frequency band of the middle or the apical electrode (+0.25 electrode step), and steps to the center frequency of the first (+1), second (+2), and third (+3) adjacent electrodes.

RESULTS

Reproducible ACCs were recorded in 17 out of 19 subjects. Most successful recordings were obtained with the largest frequency change (+3 electrode step). Larger frequency changes resulted in shorter N1 latencies and larger N1-P2 amplitudes. In both unilaterally and bilaterally deaf subjects, the N1 latency and N1-P2 amplitude of the CI ears correlated to speech perception as well as frequency discrimination, that is, short latencies and large amplitudes were indicative of better speech perception and better frequency discrimination. No significant differences in ACC latencies or amplitudes were found between the CI ears of the unilaterally and bilaterally deaf subjects, but the CI ears of the unilaterally deaf subjects showed substantially longer latencies and smaller amplitudes than their contralateral normal-hearing ears.

CONCLUSIONS

The ACC latency and amplitude evoked by tone frequency changes correlate well to frequency discrimination and speech perception capabilities of CI users. For patients unable to reliably perform behavioral tasks, the ACC could be of added value in assessing hearing performance.

Functional Outcomes of Cochlear Implantation in Children with Bilateral Cochlear Nerve Aplasia

Background and Objectives: Many otologists face a dilemma in the decision-making process of surgical management of patients with cochlear nerve (CN) aplasia. The goal of this study is to provide fresh evidence on cochlear implantation (CI) results in patients with CN aplasia. Materials and Methods: We scrutinized functional outcomes in 37 ears of 21 children with bilateral CN aplasia who underwent unilateral or bilateral CI based on cross-sectional and longitudinal assessments. Results: The Categories of Auditory Performance (CAP) scores gradually improved throughout the 3-year follow-up; however, variable outcomes existed between individuals. Specifically, 90% of recipients with a 1-year postoperative CAP score ≤1 could not achieve a CAP score over 1 even at 3-year postoperative evaluation, while the recipients with a 1-year postoperative CAP score >1 had improved auditory performance, and 72.7% of them were able to achieve a CAP score of 4 or higher. Meanwhile, intraoperative electrically evoked compound action potential was not correlated with postoperative CAP score. Conclusions: Our results further refine previous studies on the clinical feasibility of CI as the first treatment modality to elicit favorable auditory performance in children with CN aplasia. However, special attention should be paid to pediatric patients with an early postoperative CAP score ≤1 for identification of unsuccessful cochlear implants and switching to auditory brainstem implants.

Clinical significance of the neural response telemetric thresholds in Mandarin-speaking cochlear implant patients

BACKGROUND

It is unclear whether neural response telemetric (NRT) thresholds are related to lexical tonal language performance after cochlear implants (CIs). We explored the factors associated with changes in NRT thresholds and postoperative performance of CI patients.

METHODS

Patients receiving nucleus 24 CIs in our hospital from November 2010 were enrolled. We analyzed medical records and NRT thresholds. Mandarin speech and tone identification were measured in CI patients for at least 1 year postoperatively.

RESULTS

Seventy-two patients with an average age of 16.1 years received CIs. The postoperative NRT threshold was lower than the intraoperative threshold. The NRT threshold was higher in the early- than the late-activation group (mapping within 21 vs >21 days postoperatively, respectively). Lower intraoperative NRT thresholds and curved electrodes were significantly associated with lower postoperative NRT thresholds. In multiple linear regression analysis, only postoperative NRT thresholds significantly affected speech and tone perception, including word recognition scores, tone perception, and comprehension of easy and difficult sentences (all p < 0.05). Other clinical parameters, including age, gender, implant type, and activation timing, were not significantly associated with clinical tone or speech outcomes.

CONCLUSION

Curved electrode arrays were associated with lower postoperative NRT thresholds. A lower postoperative NRT threshold might predict better performance of Mandarin-speaking CI patients. Future studies should evaluate factors that affect both postoperative NRT thresholds and lexical tonal language performance.

Electrophysiological Estimates of the Electrode-Neuron Interface Differ Between Younger and Older Listeners With Cochlear Implants

OBJECTIVES

The primary objective of this study was to quantify differences in evoked potential correlates of spiral ganglion neuron (SGN) density between younger and older individuals with cochlear implants (CIs) using the electrically evoked compound action potential (ECAP). In human temporal bone studies and in animal models, SGN density is the lowest in older subjects and in those who experienced long durations of deafness during life. SGN density also varies as a function of age at implantation and hearing loss etiology. Taken together, it is likely that younger listeners who were deafened and implanted during childhood have denser populations of SGNs than older individuals who were deafened and implanted later in life. In animals, ECAP amplitudes, amplitude growth function (AGF) slopes, and their sensitivity to stimulus interphase gap (IPG) are predictive of SGN density. The authors hypothesized that younger listeners who were deafened and implanted as children would demonstrate larger ECAP amplitudes, steeper AGF slopes, and greater IPG sensitivity than older, adult-deafened and implanted listeners.

DESIGN

Data were obtained from 22 implanted ears (18 individuals). Thirteen ears (9 individuals) were deafened and implanted as children (child-implanted group), and nine ears (9 individuals) were deafened and implanted as adults (adult-implanted group). The groups differed significantly on a number of demographic variables that are implicitly related to SGN density: (1) chronological age; (2) age at implantation; and (3) duration of preimplantation hearing loss. ECAP amplitudes, AGF linear slopes, and thresholds were assessed on a subset of electrodes in each ear in response to two IPGs (7 and 30 µsec). Speech recognition was assessed using a medial vowel identification task.

RESULTS

Compared with the adult-implanted listeners, individuals in the child-implanted group demonstrated larger changes in ECAP amplitude when the IPG of the stimulus was increased from 7 to 30 µsec (i.e., greater IPG sensitivity). On average, child-implanted participants also had larger ECAP amplitudes and steeper AGF linear slopes than the adult-implanted participants, irrespective of IPG. IPG sensitivity for AGF linear slope and ECAP threshold did not differ between age groups. Vowel recognition performance was not correlated with any of the ECAP measures assessed in this study.

CONCLUSIONS

The results of this study support the theory that young CI listeners who were deafened and implanted during childhood may have denser neural populations than older listeners who were deafened and implanted as adults. Potential between-group differences in SGN integrity emphasize a need to investigate optimized CI programming parameters for younger and older listeners.

Amplitude Growth Functions of Auditory Nerve Responses to Electric Pulse Stimulation With Varied Interphase Gaps in Cochlear Implant Users With Ipsilateral Residual Hearing

Amplitude growth functions (AGFs) of electrically evoked compound action potentials (eCAPs) with varying interphase gaps (IPGs) were measured in cochlear implant users with ipsilateral residual hearing (electric-acoustic stimulation [EAS]). It was hypothesized that IPG effects on AGFs provide an objective measure to estimate neural health. This hypothesis was tested in EAS users, as residual low-frequency hearing might imply survival of hair cells and hence better neural health in apical compared to basal cochlear regions. A total of 16 MED-EL EAS subjects participated, as well as a control group of 16 deaf cochlear implant users. The IPG effect on the AGF characteristics of slope, threshold, dynamic range, and stimulus level at 50% maximum eCAP amplitude (level_50%) was investigated. AGF threshold and level_50% were significantly affected by the IPG in both EAS and control group. The magnitude of AGF characteristics correlated with electrode impedance and electrode-modiolus distance (EMD) in both groups. In contrast, the change of the AGF characteristics with increasing IPG was independent of these electrode-specific measures. The IPG effect on the AGF level_50% in both groups, as well as on the threshold in EAS users, correlated with the duration of hearing loss, which is a predictor of neural health. In EAS users, a significantly different IPG effect on level_50% was found between apical and medial electrodes. This outcome is consistent with our hypothesis that the influence of IPG effects on AGF characteristics provides a sensitive measurement and may indicate better neural health in the apex compared to the medial cochlear region in EAS users.

The Effect of Aging on the Electrically Evoked Compound Action Potential

OBJECTIVES

To examine the effect of aging on electrically evoked compound action potential (eCAP) growth functions and their relationship with speech recognition in noise in cochlear implant (CI) users.

BACKGROUND

Aging typically leads to difficulty understanding speech in background noise. Previous research has explored cognitive and central auditory mechanisms contributing to these age-related changes. However, it is likely that the peripheral auditory system may also play a role. One challenge is separating the effects of aging on cochlear structures from the effects of aging on the auditory nerve in humans. CI users provide a unique way to address this issue, as intracochlear electrical stimulation bypasses surviving hair cells and activates the auditory nerve directly. Studies in animal models suggest that age-related loss of spiral ganglion cells could lead to shallower eCAP growth functions and/or increased eCAP thresholds and potentially negatively impact speech recognition.

METHODS

Ten younger and 10 older postlingually deafened, adult CI recipients participated in this study. eCAP amplitude-intensity functions were recorded from a mid-array electrode and fit using linear functions. Speech recognition in noise was assessed using the Quick Speech-in-Noise (QuickSIN) test.

RESULTS

Older CI users had significantly shallower eCAP growth functions and higher eCAP thresholds than younger CI users. eCAP growth functions were not correlated with speech recognition in noise.

CONCLUSION

Results of this study suggest that older adults may have poorer neural survival, resulting in higher eCAP thresholds and shallower eCAP growth functions. These findings expand our understanding of mechanisms underlying age-related changes in the peripheral auditory system.

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

OBJECTIVES/HYPOTHESIS

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

STUDY DESIGN

Retrospective chart review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E940-E945, 2021.

Measuring implanted patient response to tone pips

BACKGROUND

An electrical potential not previously reported-electrical cochlear response (ECR)-observed only in implanted patients is described. Its amplitude and growth slope are a measurement of the stimulation achieved by a tone pip on the auditory nerve. The stimulation and recording system constructed for this purpose, the features of this potential obtained in a group of 43 children, and its possible clinical use are described. The ECR is obtained by averaging the EEG epochs acquired each time the cochlear implant (CI) processes a tone pip of known frequency and intensity when the patient is sleeping and using the CI in everyday mode. The ECR is sensitive to tone pip intensity level, microphone sensitivity, sound processor gain, dynamic range of electrical current, and responsiveness to electrical current of the auditory nerve portion involved with the electrode under test. It allows individual evaluation of intracochlear electrodes by choosing, one at the time, the central frequency of the electrode as the test tone pip frequency, so the ECR measurement due to a variable intensity tone pip allows to establish the suitability of the dynamic range of the electrode current.

RESULTS

There is a difference in ECR measurements when patients are grouped based on their auditory behavior. The ECR slope and amplitude for the Sensitive group is 0.2 μV/dBHL and 10 μV at 50 dBHL compared with 0.04 μV/dBHL and 3 μV at 50dBHL for the Inconsistent group. The clinical cases show that adjusting the dynamic range of current based on the ECR improved the patient's auditory behavior.

CONCLUSIONS

ECR can be recorded regardless of the artifact due to the electromyographic activity of the patient and the functioning of the CI. Its amplitude and growth slope versus the intensity of the stimulus differs between electrodes. The relationship between minimum ECR detection intensity level and auditory threshold suggests the possibility of estimating patient auditory thresholds this way. ECR does not depend on the subject's age, cooperation, or health status. It can be obtained at any time after implant surgery and the test procedure is the same regardless of device manufacturer.

Slope of electrically evoked compound action potential amplitude growth function is site-dependent

OBJECTIVES

In human cochlear implant (CI) recipients, the slope of the electrically evoked compound action potential (ECAP) amplitude growth function (AGF) is not very well investigated, in comparison to the threshold derived from the AGF. This is despite the fact that it was shown in animal experiments that the slope correlates with the number of excitable neurons. The rationale of this study was to establish baseline data of the AGF slope for possible clinical applications, while investigating stability over time and dependence on cochlear site.

DESIGN

ECAP AGFs of 16 ears implanted with MED-EL CIs were recorded on all electrode contacts during the normal clinical routine at 4 different points in time.

RESULTS

Due to patient availability, not all 16 ears could be measured at all 4 points in time. A dependence of the slope on the electrode position was visible and statistically significant: At the three electrode contacts at the apical end of the array, the slope is greater compared to the medial and basal region of the cochlea.

CONCLUSION

The three most apical electrode contacts show greater slopes of ECAP AGF recordings. Our data of the cohort slopes show mild effects between the 4 different points in time.

How electrically evoked compound action potentials in chronically implanted guinea pigs relate to auditory nerve health and electrode impedance

This study examined how multiple measures based on the electrically evoked compound action potential (ECAP) amplitude-growth functions (AGFs) were related to estimates of neural [spiral ganglion neuron (SGN) density and cell size] and electrode impedance measures in 34 specific pathogen free pigmented guinea pigs that were chronically implanted (4.9-15.4 months) with a cochlear implant electrode array. Two interphase gaps (IPGs) were used for the biphasic pulses and the effect of the IPG on each ECAP measure was measured ("IPG effect"). When using a stimulus with a constant IPG, SGN density was related to the across-subject variance in ECAP AGF linear slope, peak amplitude, and N1 latency. The SGN density values also help to explain a significant proportion of variance in the IPG effect for AGF linear slope and peak amplitude measures. Regression modeling revealed that SGN density was the primary dependent variable contributing to across-subject variance for ECAP measures; SGN cell size did not significantly improve the fitting of the model. Results showed that simple impedance measures were weakly related to most ECAP measures but did not typically improve the fit of the regression model.

Estimating Real-World Performance of Percutaneously Coupled Bone-Conduction Device Users With Severe-to-Profound Unilateral Hearing Loss

Purpose The bone-conduction device attached to a percutaneous screw (BCD) is an important treatment option for individuals with severe-to-profound unilateral hearing loss (UHL). Clinicians may use subjective questionnaires and speech-in-noise measures to evaluate BCD use in this patient population; however, the translation of these metrics to real-world aided performance is unclear. The purpose of this study was twofold: first, to measure speech-in-noise performance in BCD users with severe-to-profound UHL in a simulated real-world environment, relative to individuals with normal hearing bilaterally; second, to determine if BCD users' subjective reports of aided performance relate to simulated real-world performance. Method A between-subjects design with two groups was conducted with 14 adults with severe-to-profound UHL (BCD group) and 10 age-matched participants with normal hearing bilaterally (control group). Speech-in-noise tests were administered in an eight-speaker R-Space simulating a real-world environment. To further explore speech-in-noise evaluation methods for this population, testing was also completed in a clinically common two-speaker array. The effects of various microphone settings on performance were explored for BCD users. Subjective performance was measured with the Abbreviated Profile of Hearing Aid Benefit (APHAB; Cox & Alexander, 1995) and the Speech, Spatial and Qualities of Hearing Scale (Gatehouse & Noble, 2004). Statistical analyses to explore relationships between variables included repeated-measures analysis of variance, regression analyses, independent-samples t tests, nonparametric Mann-Whitney tests, and correlations. Results In the simulated real-world environment, BCD group participants struggled with speech-in-noise understanding compared to control group participants. BCD benefit was observed for all microphone settings when speech stimuli were presented to the side with the BCD. When adaptive directional or fixed directional microphone settings were used, a relationship was noted between simulated real-world speech-in-noise performance for speech stimuli presented to the side with the BCD and subjective reports on the Background Noise subscale of the APHAB. Conclusions The Background Noise subscale of the APHAB may help estimate real-world speech-in-noise performance for BCD users with severe-to-profound UHL for signals of interest presented to the implanted side, specifically when adaptive or fixed directional microphone settings are used. This subscale may provide an efficient and accessible alternative to assessing real-world speech-in-noise performance in lieu of less clinically available measurement tools, such as an R-Space.

Effects of Electrode Location on Estimates of Neural Health in Humans with Cochlear Implants

There are a number of psychophysical and electrophysiological measures that are correlated with SGN density in animal models, and these same measures can be performed in humans with cochlear implants (CIs). Thus, these measures are potentially applicable in humans for estimating the condition of the neural population (so called "neural health" or "cochlear health") at individual sites along the electrode array and possibly adjusting the stimulation strategy in the CI sound processor accordingly. Some measures used to estimate neural health in animals have included the electrically evoked compound potential (ECAP), psychophysical detection thresholds, and multipulse integration (MPI). With regard to ECAP measures, it has been shown that the change in the ECAP response as a function of increasing the stimulus interphase gap ("IPG Effect") also reflects neural density in implanted animals. These animal studies have typically been conducted using preparations in which the electrode was in a fixed position with respect to the neural population, whereas in human cochlear implant users, the position of individual electrodes varies widely within an electrode array and also across subjects. The current study evaluated the effects of electrode location in the implanted cochlea (specifically medial-lateral location) on various electrophysiological and psychophysical measures in eleven human subjects. The results demonstrated that some measures of interest, specifically ECAP thresholds, psychophysical detection thresholds, and ECAP amplitude-growth function (AGF) linear slope, were significantly related to the distances between the electrode and mid-modiolar axis (MMA). These same measures were less strongly related or not significantly related to the electrode to medial wall (MW) distance. In contrast, neither the IPG Effect for the ECAP AGF slope or threshold, nor the MPI slopes were significantly related to MMA or MW distance from the electrodes. These results suggest that "within-channel" estimates of neural health such as the IPG Effect and MPI slope might be more suitable for estimating nerve condition in humans for clinical application since they appear to be relatively independent of electrode position.

Datalogging Statistics and Speech Recognition During the First Year of Use in Adult Cochlear Implant Recipients

OBJECTIVE

To examine device datalogging characteristics and postoperative speech recognition performance in adult cochlear implant (CI) recipients.

STUDY DESIGN

Retrospective study examining datalogging characteristics throughout the first year of device use and postoperative speech recognition outcomes measured at 1 year.

PATIENTS

One hundred seventy-seven adults who received a Cochlear CI.

MAIN OUTCOME MEASURES

Average values for environmental scene classification (hours of device use per day, and percent of hours per day in quiet, noise, and speech) as reported by Cochlear datalogging over the first year of device use. Speech recognition was assessed at 1 year postactivation.

RESULTS

During the first year of devices use, CI listeners >80 years of age used their device significantly less (average = 10.97 h/d) than the youngest adult listeners (18-30 yrs), who used their device an average of 13.29 hours/d. There was no consistent effect of age on the number of hours a CI user listened to speech in noise each day. Correlational and regression analyses suggest that the number of average hours of device use is the primary factor that accounts for variance observed in postoperative consonant-nucleus-consonant word scores.

CONCLUSION

Results suggest that the average number of hours listening to speech in noise is not related to postoperative performance, but the average number of hours of device use per day is correlated with postoperative performance. Further research is needed to determine if these findings are merely correlational or causal in nature.

Cochlear Implant Performance in Adult Patients with Absent Intraoperative Electrically Evoked Compound Action Potentials

OBJECTIVE

To describe cochlear implant performance outcomes in adult patients in whom no intraoperative electrically evoked compound action potential (ECAP) responses were able to be obtained despite intracochlear electrode placement.

STUDY DESIGN

Retrospective case review.

SETTING

Academic tertiary center.

SUBJECTS AND METHODS

Patients 18 years of age and older undergoing cochlear implantation between May 2010 and September 2018 with absent ECAP measurements intraoperatively with intracochlear electrode positioning were identified. Patient performance on sentence recognition testing using the Hearing in Noise Test (HINT) and AzBio at 6 to 12 months postoperatively was compared to preimplantation scores. Additional collected data included patient demographics, etiology of hearing loss, and preoperative pure-tone average (PTA) and word recognition scores (WRSs).

RESULTS

Intraoperative ECAP measurements were unable to be obtained in 15 cochlear implants performed on 14 patients out of 383 cochlear implant cases. Of the patients with absent ECAP measures, the mean ± SD age was 61.7 ± 15.7 years. Causes of hearing loss included congenital hearing loss, meningitis, autoimmune inner ear disease, otosclerosis, presbycusis, and Ménière's disease. The average preoperative PTA was 103.5 ± 17.0 dB. Twelve implanted ears had a WRS of 0% and 9 had a HINT score of 0% prior to surgery. The mean HINT score at 6 to 12 months postimplantation was 57.8% ± 37.8% and had improved by 42.6% ± 35.6% compared to the mean preimplantation HINT score (95% confidence interval, 22.0%-63.1%, P = .001, paired Student t test).

CONCLUSION

There is a wide range of cochlear implant performance in patients with absent intraoperative ECAP measures ranging from sound awareness to HINT scores of 100%.

Audiologists' preferences in programming cochlear implants: A preliminary report

Background: There is little data available addressing how clinical audiologists handle cochlear implant (CI) programming between device manufacturers and make decisions on related services, particularly in the United States. Objectives: This study sought to understand the techniques and settings professionals use with their patients, how they approach bimodal fitting, which tests they use to evaluate patient and device performance, and their overall preferences of (re)habilitative options. Methods: A questionnaire was developed and distributed to CI audiologists throughout the United States electronically. Results: All respondents reported either always or almost always using Cochlear's default signal processing strategy in contrast to the 64% reported for Med-El and 40% for Advanced Bionics. A trend of less use of electrically evoked stapedial reflex threshold (eSRT) than electrically evoked compound action potentials (eCAP) for objective measures was revealed. Higher likelihood of performing speech recognition tests in quiet than in noise was revealed. Preferences for bimodal fitting trend toward using a partner company's hearing aid, although preferences were comparable in adopting four types of hearing aid formulas surveyed in the questionnaire. Conclusions: These data confirm high variability among audiologists' CI programming practices, and documenting these differences is an important step to understanding how to best treat patients.

Cochlear Implantation with the CI512 and CI532 Precurved Electrode Arrays: One-Year Speech Recognition and Intraoperative Thresholds of Electrically Evoked Compound Action Potentials

INTRODUCTION

Precurved cochlear implant (CI) electrode arrays were developed in an attempt to improve the auditory outcome of cochlear implantation, which varies greatly. The recent CI532 (Cochlear Corp., Sydney, Australia) may offer further advantages as its electrode array is thinner than previous precurved CI electrode arrays. The aims here were to investigate 1-year postoperative speech recognition, intraoperative electrically evoked compound action potentials (ECAPs), and their possible relation in patients implanted with a CI532 or its predecessor CI512.

METHODS

A retrospective analysis of data from 63 patients subjected to cochlear implantation at the Karolinska University Hospital, Sweden, was performed. Speech recognition of the implanted ear was evaluated using phonemically balanced monosyllabic Swedish words at 65 dB SPL. ECAPs were evaluated using the intraoperative ECAP threshold across ≥8 electrodes generated by the automated neural response telemetry of the CI.

RESULTS

The median aided speech recognition score (SRS) 1 year after implantation was 52% (quartile 1 = 40%, quartile 3 = 60%, n = 63) and did not differ statistically significantly between patients with CI512 (n = 38) and CI532 (n = 25). The mean ECAP threshold was 188 CL (current level; SD = 15 CL, n = 54) intraoperatively and did not differ statistically significantly between patients with CI512 (n = 32) and CI532 (n = 22), but the threshold for each electrode varied more between patients with a CI512 (p < 0.0001). A higher mean ECAP threshold was associated with a worse SRS (Spearman's ρ = -0.46, p = 0.0004, n = 54). The association remained among those with a CI512 (Spearman's ρ = -0.62, p = 0.0001, n = 32) when stratified by CI electrode array.

CONCLUSION

No statistically significant difference in speech recognition 1 year after cochlear implantation or in mean threshold of ECAP intraoperatively was found between patients with a CI512 and the more recent, slim CI532, but the ECAP thresholds varied more between those with a CI512. A statistically significant association between SRS and mean ECAP threshold was found, but stratified analysis suggests that the association may be true only for patients with a CI512.

Residual Cochlear Function in Adults and Children Receiving Cochlear Implants: Correlations With Speech Perception Outcomes

OBJECTIVES

Variability in speech perception outcomes with cochlear implants remains largely unexplained. Recently, electrocochleography, or measurements of cochlear potentials in response to sound, has been used to assess residual cochlear function at the time of implantation. Our objective was to characterize the potentials recorded preimplantation in subjects of all ages, and evaluate the relationship between the responses, including a subjective estimate of neural activity, and speech perception outcomes.

DESIGN

Electrocochleography was recorded in a prospective cohort of 284 candidates for cochlear implant at University of North Carolina (10 months to 88 years of ages). Measurement of residual cochlear function called the "total response" (TR), which is the sum of magnitudes of spectral components in response to tones of different stimulus frequencies, was obtained for each subject. The TR was then related to results on age-appropriate monosyllabic word score tests presented in quiet. In addition to the TR, the electrocochleography results were also assessed for neural activity in the forms of the compound action potential and auditory nerve neurophonic.

RESULTS

The TR magnitude ranged from a barely detectable response of about 0.02 µV to more than 100 µV. In adults (18 to 79 years old), the TR accounted for 46% of variability in speech perception outcome by linear regression (r = 0.46; p < 0.001). In children between 6 and 17 years old, the variability accounted for was 36% (p < 0.001). In younger children, the TR accounted for less of the variability, 15% (p = 0.012). Subjects over 80 years old tended to perform worse for a given TR than younger adults at the 6-month testing interval. The subjectively assessed neural activity did not increase the information compared with the TR alone, which is primarily composed of the cochlear microphonic produced by hair cells.

CONCLUSIONS

The status of the auditory periphery, particularly of hair cells rather than neural activity, accounts for a large fraction of variability in speech perception outcomes in adults and older children. In younger children, the relationship is weaker, and the elderly differ from other adults. This simple measurement can be applied with high throughput so that peripheral status can be assessed to help manage patient expectations, create individually-tailored treatment plans, and identify subjects performing below expectations based on residual cochlear function.

Assessing the Relationship Between the Electrically Evoked Compound Action Potential and Speech Recognition Abilities in Bilateral Cochlear Implant Recipients

OBJECTIVES

The primary objective of the present study was to examine the relationship between suprathreshold electrically evoked compound action potential (ECAP) measures and speech recognition abilities in bilateral cochlear implant listeners. We tested the hypothesis that the magnitude of ear differences in ECAP measures within a subject (right-left) could predict the difference in speech recognition performance abilities between that subject's ears (right-left).

DESIGN

To better control for across-subject variables that contribute to speech understanding, the present study used a within-subject design. Subjects were 10 bilaterally implanted adult cochlear implant recipients. We measured ECAP amplitudes and slopes of the amplitude growth function in both ears for each subject. We examined how each of these measures changed when increasing the interphase gap of the biphasic pulses. Previous animal studies have shown correlations between these ECAP measures and auditory nerve survival. Speech recognition measures included speech reception thresholds for sentences in background noise, as well as phoneme discrimination in quiet and in noise.

RESULTS

Results showed that the between-ear difference (right-left) of one specific ECAP measure (increase in amplitude growth function slope as the interphase gap increased from 7 to 30 µs) was significantly related to the between-ear difference (right-left) in speech recognition. Frequency-specific response patterns for ECAP data and consonant transmission cues support the hypothesis that this particular ECAP measure may represent localized functional acuity.

CONCLUSIONS

The results add to a growing body of literature suggesting that when using a well-controlled research design, there is evidence that underlying neural function is related to postoperative performance with a cochlear implant.

Assessing Cognitive Abilities in High-Performing Cochlear Implant Users

Despite being considered one of the most successful neural prostheses, cochlear implants (CIs) provide recipients with a wide range of speech perception performance. While some CI users can understand speech in the absence of visual cues, other recipients exhibit more limited speech perception. Cognitive skills have been documented as a contributor to complex auditory processing, such as language understanding; however, there are no normative data for existing standardized clinical tests assessing cognitive abilities in CI users. Here, we assess the impact of modality of presentation (i.e., auditory-visual versus visual) for the administration of working memory tests in high-performing CI users in addition to measuring processing speed, cognitive efficiency and intelligence quotient (IQ). Second, we relate performance on these cognitive measures to clinical CI speech perception outcomes.

Methods: Twenty one post-lingually deafened, high-performing, adult CI users [age range: 52–88 years; 3 unilateral CI, 13 bimodal (i.e., CI with contralateral hearing aid), 5 bilateral CI] with clinical speech perception scores (i.e., AzBio sentences in quiet for the first-ear CI) of ≥60% were recruited. A cognitive test battery assessing auditory-visual working memory (AVWM), visual working memory (VWM), processing speed, cognitive efficiency and IQ was administered, in addition to clinical measures of speech perception in quiet (i.e., AzBio sentences in quiet). AzBio sentences were assessed in two conditions: first-ear CI only, and best-aided everyday wearing condition. Subjects also provided self-reported measures of performance and benefit from their CI using standardized materials, including the Glasgow Benefit Inventory (GBI) and the Nijmegen Cochlear Implant questionnaire (NCIQ).

Results: High-performing CI users demonstrated greater VWM than AVWM recall. VWM was positively related to AzBio scores when measured in the first-ear CI only. AVWM, processing speed, cognitive efficiency, and IQ did not relate to either measure of speech perception (i.e., first-ear CI or best-aided conditions). Subjects’ self-reported benefit as measured by the GBI predicted best-aided CI speech perception performance.

Conclusion: In high-performing CI recipients, visual presentation of working memory tests may improve our assessment of cognitive function.

In Vivo Electrocochleography in Hybrid Cochlear Implant Users Implicates TMPRSS3 in Spiral Ganglion Function

Cochlear implantation, a surgical method to bypass cochlear hair cells and directly stimulate the spiral ganglion, is the standard treatment for severe-to-profound hearing loss. Changes in cochlear implant electrode array design and surgical approach now allow for preservation of acoustic hearing in the implanted ear. Electrocochleography (ECochG) was performed in eight hearing preservation subjects to assess hair cell and neural function and elucidate underlying genetic hearing loss. Three subjects had pathogenic variants in TMPRSS3 and five had pathogenic variants in genes known to affect the cochlear sensory partition. The mechanism by which variants in TMPRSS3 cause genetic hearing loss is unknown. We used a 500-Hz tone burst to record ECochG responses from an intracochlear electrode. Responses consist of a cochlear microphonic (hair cell) and an auditory nerve neurophonic. Cochlear microphonics did not differ between groups. Auditory nerve neurophonics were smaller, on average, in subjects with TMPRSS3 deafness. Results of this proof-of-concept study provide evidence that pathogenic variants in TMPRSS3 may impact function of the spiral ganglion. While ECochG as a clinical and research tool has been around for decades, this study illustrates a new application of ECochG in the study of genetic hearing and deafness in vivo.

Sequential pediatric bilateral cochlear implantation: The effect of time interval between implants

OBJECTIVE

To examine speech intelligibility in children subjected to sequential bilateral cochlear implants (CI) surgery and to assess the influence of the inter-stage interval duration.

INTRODUCTION

Binaural hearing recovery can have additional benefits, especially in speech and language development in patients with congenital profound sensorineural hearing loss; so recently there has been an increase in the number of children receiving bilateral CI.

METHODS

Twenty-seven children who underwent sequential bilateral cochlear implant (SBCI) with a short (1-3 yrs), medium (4-6 yrs) and long (7-12 yrs) range interval between both implantations, respectively, were evaluated. All patients underwent periodic speech perception test in quiet and noise after second implant activation in three conditions: with the first or second implant alone and with both implants. Results were examined according to the inter-stage interval.

RESULTS

Speech intelligibility in noise was significantly better under bilateral conditions than either ear alone, in all three groups. Small improvements were seen in quiet, especially in the third group (6-12 yrs).

CONCLUSION

Benefits of second implant in the early-implanted children and after a short inter-implant delay are more evident. However our study support that, even after a long period of deafness and despite a prolonged inter-stage interval, sequential bilateral cochlear implantation should be considered.

LEVEL OF EVIDENCE

Level 4.

Intracochlear Recordings of Acoustically and Electrically Evoked Potentials in Nucleus Hybrid L24 Cochlear Implant Users and Their Relationship to Speech Perception

The Hybrid cochlear implant (CI) has been developed for individuals with high frequency hearing loss who retain good low frequency hearing. Outcomes have been encouraging but individual variability is high; the health of the cochlea and the auditory nerve may be important factors driving outcomes. Electrically evoked compound action potentials (ECAPs) reflect the response of the auditory nerve to electrical stimulation while electrocochleography (ECochG) reflects the response of the cochlear hair cells and auditory nerve to acoustic stimulation. In this study both ECAPs and ECochG responses were recorded from Nucleus Hybrid L24 CI users. Correlations between these two measures of peripheral auditory function and speech perception are reported. This retrospective study includes data from 25 L24 CI users. ECAPs and ECochG responses were recorded from an intracochlear electrode using stimuli presented at or near maximum acceptable loudness levels. Speech perception was assessed using Consonant-Nucleus-Consonant (CNC) word lists presented in quiet and AzBio sentences presented at a +5 dB signal-to-noise ratio in both the combined acoustic and electric (A+E) and electric (E) alone listening modes. Acoustic gain was calculated by subtracting these two scores. Correlations between these physiologic and speech perception measures were then computed. ECAP amplitudes recorded from the most apical electrode were significantly correlated with CNC scores measured in the E alone (r = 0.56) and A+E conditions (r = 0.64), but not with performance on the AzBio test. ECochG responses recorded using the most apical electrode in the intracochlear array but evoked using a 500 Hz tone burst were not correlated with either the scores on the CNC or AzBio tests. However, ECochG amplitude was correlated with a composite metric relating the additional benefit of acoustic gain in noise relative to quiet conditions (r = 0.67). Both measures can be recorded from Hybrid L24 CI users and both ECAP and ECochG measures may result in more complete characterization of speech perception outcomes than either measure alone.

Suprathreshold compound action potential amplitude as a measure of auditory function in cochlear implant users

Electrically evoked compound action potential (eCAP) amplitudes elicited at suprathreshold levels were assessed as a measure of the effectiveness of cochlear implant (CI) stimulation. Twenty-one individuals participated; one was excluded due to facial stimulation during eCAP testing. For each participant, eCAPs were elicited with stimulation from seven electrodes near the upper limit of the individual's electrical dynamic range. A reduced-channel CI program was created using those same seven electrodes, and participants performed a vowel discrimination task. Consistent with previous reports, eCAP amplitudes varied across tested electrodes; the profiles were unique to each individual. In 6 subjects (30%), eCAP amplitude variability was partially explained by the impedance of the recording electrode. The remaining amplitude variability within subjects, and the variability observed across subjects could not be explained by recording electrode impedance. This implies that other underlying factors, such as variations in neural status across the array, are responsible. Across-site mean eCAP amplitude was significantly correlated with vowel discrimination scores (r2 = 0.56). A single eCAP amplitude measured from the middle of the array was also significantly correlated with vowel discrimination, but the correlation was weaker (r2 = 0.37), though not statistically different from the across-site mean. Normalizing each eCAP amplitude by its associated recording electrode impedance did not improve the correlation with vowel discrimination (r2 = 0.52). Further work is needed to assess whether combining eCAP amplitude with other measures of the electrode-neural interface and/or with more central measures of auditory function provides a more complete picture of auditory function in CI recipients.