Longitudinal study of the ecap measured in children with cochlear implants

Comparison of Intraoperative Neural Response Telemetry Results and Postoperative Neural Response Telemetry Results in Case of Children with Congenital Bilateral Severe to Profound Sensorineural Hearing Loss Undergoing Single Sided Cochlear Implantation

Aim and Objectives

This study is designed to compare the Intra Operative Neural Response Telemetry (NRT) results with Post-Operative NRT results of the cochlear implanted children, to assess the importance of Intra Operative NRT thresholds in device activation and/or switch on of the audio processor and to evaluate the importance of Intra and post operative AutoNRT results in predicting behavioural thresholds during mapping of prelingual Cochlear Implanted children.

Materials and methods

A total of thirty (30) children (16 boys, 14 girls) with congenital Bilateral (B/L) severe to profound Sensorineural hearing loss (SNHL) were included in this study. Children between the age range of 12 to 60 months were participated in this study. All the participants were implanted with Nucleus 24 cochlear implant system. In each patient, the intra operative NRT-thresholds were measured for all 22 active electrodes. Then Intra Operative NRT thresholds were correlated with Post-Operative NRT thresholds at the time of switch on and the behavioural map after six months of switch on of the device (Audio Processor).

Results

There is a significant enhancement observed in thresholds of postoperative NRT responses which were raised or absent during intraoperative session. There is a gain in NRT thresholds marked after 6 months of postoperative follow up in comparison with first measurement at the time of Switch On of the device but the change not that significant. During postoperative mapping, there was a significant positive correlation noticed between neural response telemetry level measurements and behavioural threshold level.

Conclusion

Absent or elevated NRT responses during intraoperative testing for some electrodes especially basal electrodes does not mean that electrode is out of order or outside the cochlea, because an improvement in NRT thresholds usually occurs postoperatively. In case of children with congenital B/L severe to profound SNHL, the NRT values have a very useful role in predicting the behavioural thresholds. Combination of NRT values with behavioural thresholds and observations of Auditory Verbal Therapist can help in providing best suitable Map to the recipient.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03284-x.

Utility of intraoperative neural response telemetry in pediatric cochlear implants

OBJECTIVE

The objective of this study is to evaluate the relationship between intraoperative neural response telemetry (NRT) and postoperative Threshold (T) and Comfort (C) levels and their correlation over time after cochlear implantation (CI).

METHODS

A retrospective chart review was conducted of patients less than 18 years of age who had CI with a Cochlear™ device and NRT at an academic center from 2010 to 2019. Data collected included demographics, extrapolated NRT threshold (tNRT) and slope of amplitude for electrodes 1, 6/7, 11/12, 16, and 22, and postoperative T and C levels at initial activation and 1 month, 3 months, and 1 year post-activation. Associations between T and C levels and slope of amplitude or tNRT were assessed using Spearman's rank correlation.

RESULTS

39 patients (65 CIs) were included. Intraoperative tNRT correlated strongly with T and C levels at 1 month, 3 months, and 1 year post-activation on nearly all electrodes. Electrodes 6/7 and 11/12 at 3 months and electrodes 6/7 at 1 year did not correlate with T and C levels. There was no significant relationship between the slope of amplitude for nearly all electrodes and the T or C levels post-activation.

CONCLUSION

NRT is invaluable in children, with significant correlation found between tNRT and T and C levels over time on nearly all electrodes. There are changes in T and C levels in electrodes 6/7 and 11/12 over time, and close surveillance is beneficial to tailor programming as needed.

Auditory Evoked Potentials in Communication Disorders: An Overview of Past, Present, and Future

This article provides a brief overview of auditory evoked potentials (AEPs) and their application in the areas of research and clinics within the field of communication disorders. The article begins with providing a historical perspective within the context of the key scientific developments that led to the emergence of numerous types of AEPs. Furthermore, the article discusses the different AEP techniques in the light of their feasibility in clinics. As AEPs, because of their versatility, find their use across disciplines, this article also discusses some of the research questions that are currently being addressed using AEP techniques in the field of communication disorders and beyond. At the end, this article summarizes the shortcomings of the existing AEP techniques and provides a general perspective toward the future directions. The article is aimed at a broad readership including (but not limited to) students, clinicians, and researchers. Overall, this article may act as a brief primer for the new AEP users, and as an overview of the progress in the field of AEPs along with future directions, for those who already use AEPs on a routine basis.

Optimized SNR-based ECAP threshold determination is comparable to the judgement of human evaluators

In cochlear implant (CI) users, measurements of electrically evoked compound action potentials (ECAPs) prove the functionality of the neuron-electrode interface. Objective measures, e.g., the ECAP threshold, may serve as a basis for the clinical adjustment of the device for the optimal benefit of the CI user. As for many neural responses, the threshold determination often is based on the subjective assessment of the clinical specialist, whose decision-making process could be aided by autonomous computational algorithms. To that end, we extended the signal-to-noise ratio (SNR) approach for ECAP threshold determination to be applicable for FineGrain (FG) ECAP responses. The new approach takes advantage of two features: the FG stimulation paradigm with its enhanced resolution of recordings, and SNR-based ECAP threshold determination, which allows defining thresholds independently of morphology and with comparably low computational power. Pearson's correlation coefficient r between the ECAP threshold determined by five experienced evaluators and the threshold determined with the FG-SNR algorithm was in the range of r = 0.78-0.93. Between evaluators, r was in a comparable range of 0.84-0.93. A subset of the parameters of the algorithm was varied to identify the parameters with the highest potential to improve the FG-SNR formalism in the future. The two steps with the strongest influence on the agreement between the threshold estimate of the evaluators and the algorithm were the removal of undesired frequency components (denoising of the response traces) and the exact determination of the two time windows (signal and noise and noise only)."The parameters were linked to the properties of an ECAP response, indicating how to adjust the algorithm for the automatic detection of other neurophysiological responses.

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.

A Ten-Year Review of Audiological Performance in Children with Inner Ear Abnormalities after Cochlear Implantation in Singapore

OBJECTIVES

To evaluate children with inner ear malformations following cochlear implantation (CI) in a tertiary pediatric hospital in Singapore to identify factors influencing outcomes after CI.

METHODS

This is a retrospective cohort study of children aged 0 to 18 years, who had CI between 2000 and 2013. Demographic information, data on risk factors, type of inner ear malformation (IEM), age at implantation, speech pre- and postimplantation, and duration of follow-up were collected from clinical records. Operative details and audiological outcomes were also analyzed.

RESULTS

A total of 70 children underwent 83 CI surgeries. The mean age of the patients was 4.05 ± 3.17 years (range 1-18 years). Twenty patients (28.57%) had abnormal CT scan findings. CSF gusher occurred in 15 out of 26 CI (57.69%) in the group with IEM. Nine out of twenty patients (45.00%) had poor IT-MAIS scores prior to implantation. The average preoperative IT-MAIS score for children with anomalous inner ear anatomy was 14.1. The older CI patients, 3/20 (15.00%), mean age 8.33 years (range 7-10 years), were mostly referred for persistently unclear speech following hearing aids. Eleven patients (55.00%) had good speech and aided hearing threshold within speech limits after CI and were eligible for reintegration into mainstream schools. Five patients (25.00%) had improvement in speech but continued to receive education in special schools. Four patients (20.00%) had poor progress after surgery.

CONCLUSION

The presence of absent cochlear nerve, electrode folding, and underlying neurological disorders seemed to be associated with poorer outcomes.

Relationship between Electrically Evoked Compound Action Potential Thresholds and Auditory, Language, and Speech Progress after Cochlear Implant Surgery

INTRODUCTION

Electrically evoked compound action potential (ECAP) is an objective auditory response that can be used in the programing of cochlear implants. The aims of this study were to monitor ECAP thresholds and auditory, language and speech progress for 6 months after cochlear implant surgery and to evaluate any relationship between them.

MATERIALS AND METHODS

Ten children with a mean age of 4.2 (±0.6) years and bilateral congenital and profound sensorineural hearing loss underwent cochlear implant surgery and post-operation auditory and speech training. The auditory, language, and speech abilities (Newsha level) and ECAP thresholds (for apical, medial and basal region of cochlea) were evaluated 1, 3 and 6 months after surgery.

RESULTS

ECAP threshold showed no significant improvement in any of the evaluated areas in the 6 months after surgery (P>0.05); however, the Newsha level improved for all patients (P=0.00).

CONCLUSION

There was no relationship between ECAP thresholds and auditory, language, and speech abilities (Newsha level) in the first 6 months after surgery. ECAP thresholds may be a poor indicator of improvement in auditory, language, and speech abilities, and depend on many factors.

Use of remote control in the intraoperative telemetry of cochlear implant: multicentric study

Introduction

The conventional evaluation of neural telemetry and impedance requires the use of the computer coupled to an interface, with software that provides visualization of the stimulus and response. Recently, a remote control (CR220^®) was launched in the market, that allows the performance of intraoperative tests with minimal instrumentation.

Objective

To evaluate the agreement of the impedance values and neural telemetry thresholds, and the time of performance in the conventional procedure and by the remote control.

Methods

Multicentric prospective cross-sectional study. Intraoperative evaluations of cochlear implants compatible with the use of CR220^® were included. The tests were carried out in the 22 electrodes to compare the time of performance in the two situations. The agreement of the neural telemetry threshold values obtained from five electrodes was analyzed, and the agreement of impedance was evaluated by the number of electrodes with altered values in each procedure.

Results

There were no significant difference between the impedance values. There was a moderate to strong correlation between the electrically-evoked compound action potential thresholds. The mean time to perform the procedures using the CR220 was significantly lower than that with the conventional procedure.

Conclusion

The use of the CR220 provided successful records for impedance telemetry and automatic neural response telemetry.

Use of Neural Response Telemetry for Pediatric Cochlear Implants: Current Practice

OBJECTIVES

Evaluate usage trends of neural response telemetry (NRT) in cochlear implant centers across the nation and assess reported benefits of intraoperative NRT for pediatric cochlear implant recipients.

STUDY DESIGN

Survey.

STUDY PARTICIPANTS

All US cochlear implant centers (n = 110).

METHODS

A 15-question multiple-choice survey was distributed electronically to all centers. The survey captured demographic information of all centers, practice patterns surrounding the use of NRT, and the extent to which intraoperative NRT is of benefit.

RESULTS

Thirty-two invited participants (29%) completed the survey. A majority of participants reported practicing in an academic center (66%), followed by a hospital setting (19%) and private practice (16%). Seventy-two percent of survey participants reported using NRT for pediatric cochlear implant recipients. Sixty-three percent felt it improved the ability to program at initial activation, and 50% of participants felt that NRT improves satisfaction at initial activation.

CONCLUSION

This study suggests that a majority of surgeons use intraoperative NRT for pediatric cochlear implantation as an additional measure to ensure appropriate electrode placement and improve device activation. Larger studies are needed to better establish the relationship between intraoperative NRT and postoperative outcomes and justify the additional costs associated with intraoperative NRT.

Cochlear Implant Outcomes in Cochlea Nerve Aplasia and Hypoplasia

OBJECTIVE

To assess cochlear implant (CI) outcomes, and factors affecting outcomes, for children with aplasia/ hypoplasia of the cochlea nerve. We also developed a new grading system for the nerves of the internal auditory meatus (IAM) and cochlea nerve classification.

STUDY DESIGN

Retrospective patient review.

SETTING

Tertiary referral hospital and cochlear implant program.

PATIENTS

Children 0 to 16 years inclusive with a CI who had absent/hypoplastic cochlea nerve on magnetic resonance imaging (MRI).

INTERVENTION

Cochlear implant.

MAIN OUTCOME MEASURES

MRI, trans-tympanic electrical auditory brainstem response, intraoperative electrical auditory brainstem response, Neural Response Telemetry, Categories of Auditory Perception score, Main mode of communication.

RESULTS

Fifty CI recipients (26 males and 24 females) were identified, 21 had bilateral CIs, 27 had developmental delay. MRI showed cochlea nerve aplasia in 64 ears, hypoplasia in 25 ears, and a normal nerve in 11 ears. Main mode of communication was analyzed for 41 children: 21 (51%) used verbal language (15 speech alone, 5 speech plus some sign, 1 bilingual in speech and sign), and 20 (49%) used sign language (10 sign alone, 9 sign plus some speech, 1 tactile sign). Seventy-three percent of children used some verbal language. Cochlea nerve aplasia/ hypoplasia and developmental delay were both significant factors affecting main mode of communication. Categories of Auditory Performance scores were available for 59 CI ears; 47% with CN Aplasia (IAM nerve grades 0-III) and 89% with CN hypoplasia (IAM nerve grade IV) achieved Categories of Auditory Performance scores of 5 to 7 (some verbal understanding) (p = 0.003).

CONCLUSION

Our results are encouraging and useful when counselling families regarding the likelihood of language outcomes and auditory understanding.

Analysis of electrically evoked compound action potential of the auditory nerve in children with bilateral cochlear implants

Introduction

The cochlear implant device has the capacity to measure the electrically evoked compound action potential of the auditory nerve. The neural response telemetry is used in order to measure the electrically evoked compound action potential of the auditory nerve.

Objective

To analyze the electrically evoked compound action potential, through the neural response telemetry, in children with bilateral cochlear implants.

Methods

This is an analytical, prospective, longitudinal, historical cohort study. Six children, aged 1–4 years, with bilateral cochlear implant were assessed at five different intervals during their first year of cochlear implant use.

Results

There were significant differences in follow-up time (p = 0.0082) and electrode position (p = 0.0019) in the T-NRT measure. There was a significant difference in the interaction between time of follow-up and electrode position (p = 0.0143) when measuring the N1-P1 wave amplitude between the three electrodes at each time of follow-up.

Conclusion

The electrically evoked compound action potential measurement using neural response telemetry in children with bilateral cochlear implants during the first year of follow-up was effective in demonstrating the synchronized bilateral development of the peripheral auditory pathways in the studied population.

Electrically evoked compound action potential (ECAP) in cochlear implant children: Changes in auditory nerve response in first year of cochlear implant use

AIM

Recording of the electrically evoked compound action potential (ECAP) of the auditory nerve in cochlear implant (CI) patients represents an option to assess changes in auditory nerve responses and the interaction between the electrode bundle and the neural tissue over time. The aim of the present work is to assess ECAP changes during the first year of cochlear implant for the purpose of predicting thresholds and adjustment of the patients' programs over time.

METHOD

Data were collected from 25 children using Cochlear Nucleus 24 implants. ECAP thresholds were examined at the time of surgery, at initial stimulation, and 3, 6 and 12 months post-stimulation. Five electrodes located at basal, middle, and apical positions in the cochlea were tested at each time interval and ECAP thresholds were analyzed and compared.

RESULTS

There was a significant decrease in ECAP thresholds between the intraoperative measure and fitting time at all electrode sites. Mean ECAP thresholds measured at 3, 6 and 12 months post-stimulation remained similar to initial stimulation levels. Although there was no significant difference in ECAP thresholds recorded at fitting time and 12 months follow up session, there was significant increase in behavioral T and C levels from initial stimulation to the 12 months' time point.

CONCLUSION

Most electrodes undergo non-significant change in ECAP thresholds over time, and therefore thresholds obtained on the day of initial stimulation can be used to estimate the patients' map levels at any time. On the other hand, intraoperative thresholds demonstrated significant change relative to postoperative recording times, limiting the ability to use intraoperatively recorded ECAP thresholds to predict postoperative measurements.

Intraoperative Neural Response Telemetry and Neural Recovery Function: a Comparative Study between Adults and Children

Introduction Neural response telemetry (NRT) is a method of capturing the action potential of the distal portion of the auditory nerve in cochlear implant (CI) users, using the CI itself to elicit and record the answers. In addition, it can also measure the recovery function of the auditory nerve (REC), that is, the refractory properties of the nerve. It is not clear in the literature whether the responses from adults are the same as those from children.

Objective To compare the results of NRT and REC between adults and children undergoing CI surgery.

Methods Cross-sectional, descriptive, and retrospective study of the results of NRT and REC for patients undergoing IC at our service. The NRT is assessed by the level of amplitude (microvolts) and REC as a function of three parameters: A (saturation level, in microvolts), t0 (absolute refractory period, in seconds), and tau (curve of the model function), measured in three electrodes (apical, medial, and basal).

Results Fifty-two patients were evaluated with intraoperative NRT (26 adults and 26 children), and 24 with REC (12 adults and 12 children). No statistically significant difference was found between intraoperative responses of adults and children for NRT or for REC's three parameters, except for parameter A of the basal electrode.

Conclusion The results of intraoperative NRT and REC were not different between adults and children, except for parameter A of the basal electrode.

Differences between electrically evoked compound action potential (ECAP) and behavioral measures in children with cochlear implants operated in the school age vs. operated in the first years of life

OBJECTIVE

The aim of this study was to identify the differences in the NRT measures, behavioral measures, and their relationship between the group of congenitally deaf children operated in the first years of life and the group of children operated in the school age.

METHODS

The study included 40 congenitally deaf children with cochlear implants divided into two groups. Group 1 was composed of 20 children (mean age at operation 2.3 years, range 1.4-4.6 years) and Group 2 was composed of 20 children (mean age at operation 11.3 years, range 7.0-17.1 years). The ECAP was recorded using the Nucleus 24 neural response telemetry (NRT) system. In each child, the responses were evoked by the apical, middle and basal electrodes. The analyzed parameters were: the ECAP threshold (T-NRT), N1P2 amplitude, N1 latency, slope of the amplitude growth function, response morphology, threshold (T-) level, maximum comfort (C-) level, dynamic range (DR), T-NRT as a percentage of the map DR, the correlation between the T-NRT and the T- and C-levels. The recordings of parameters were performed two years after implantations.

RESULTS

The T-NRT, DR, T-NRT as a percentage of the map DR and the correlation between T-NRT and C-levels were significantly different between both groups of children. There were no statistically significant differences between the groups with respect to the amplitude, latency, slope and morphology recorded using the same electrodes. However, intragroup differences regarding NRT measures and behavioral measures with respect to the position of stimulating electrode were more prominent in Group 2 than in the Group 1.

CONCLUSIONS

Results of this study have also found a great variability of NRT and MAP measures within and across patients in both groups of children, but it was still more pronounced in the group of school children. NRT profile across electrodes follows MAP profiles better in the Group 1 then in the Group 2. Overall findings of NRT and MAP measures are not consistent and unambiguous as we expected, but still suggest potential differences between results in children operated in first years of life, and those operated in school age.