Cochlear implantees: Analysis of behavioral and objective measures for a clinical population of various age groups

Variation of electrical impedance over 5 years post-implantation and relationship with the maximum comfort level (MCL) in adults with cochlear implants

INTRODUCTION

The maximum comfort level (MCL), threshold level (THR) and electrical impedance change in the postoperative period of the cochlear implant for months until they stabilize. The objective of this article is to establish the variation during 5 post-surgical years of impedance, and its relationship with MCL in unilaterally implanted adults.

METHODS

Retrospective study over 5 years, with 78 adult patients implanted with MED-EL in a tertiary hospital from the year 2000 to 2015. The variation in impedance, MCL and the relationship between them were analyzed in basal (9-12), medial (5-8) and apical electrodes (1-4), performing an inferential ANOVA analysis of repeated measures with comparisons between consecutive times, corrected with Bonferroni criteria.

RESULTS

33 men (42.3%) and 45 women (57.7%), with a mean age of 52.7±14.6 years. "Stability" was considered the time of follow-up without statistically significant differences between one visit and the next. Changes in impedance in medial electrodes ceased to be statistically significant at 3 months, and in apicals at 6 months, with mean values of 5.84 and 6.43kΩ. MCL stabilized at 2 years in basal and apical electrodes, and at 3 years in medial, with mean values of 24.9, 22.7, and 25.6qu. There was a correlation between MCL and impedance in medium electrodes up to 3 months and in apical ones up to one year.

CONCLUSIONS

Electrical impedance drops significantly in medial and apical electrodes up to 3 and 6 months. MCL increases significantly up to two years. Impedance is related to MCL up to 6 months.

Toward neural health measurements for cochlear implantation: The relationship among electrode positioning, the electrically evoked action potential, impedances and behavioral stimulation levels

Introduction

Estimating differences in neural health across different sites within the individual cochlea potentially enables clinical applications for subjects with a cochlear implant. The electrically evoked compound action potential (ECAP) is a measure of neural excitability that possibly provides an indication of a neural condition. There are many factors, however, that affect this measure and increase the uncertainty of its interpretation. To better characterize the ECAP response, its relationship with electrode positioning, impedances, and behavioral stimulation levels was explored.

Methods

A total of 14 adult subjects implanted with an Advanced Bionics cochlear electrode array were prospectively followed up from surgery to 6 months postoperative. Insertion depth, distance to the modiolus, and distance to the medial wall were assessed for each electrode by postoperative CT analysis. ECAPs were measured intraoperatively and at three visits postoperatively on all 16 electrodes using the NRI feature of clinical programming software and characterized using multiple parameters. Impedances and behavioral stimulation levels were measured at every fitting session.

Results

Patterns in ECAPs and impedances were consistent over time, but high variability existed among subjects and between different positions in the cochlea. Electrodes located closer to the apex of the cochlea and closer to the modiolus generally showed higher neural excitation and higher impedances. Maximum loudness comfort levels were correlated strongly with the level of current needed to elicit a response of 100 μV ECAP.

Conclusion

Multiple factors contribute to the ECAP response in subjects with a cochlear implant. Further research might address whether the ECAP parameters used in this study will benefit clinical electrode fitting or the assessment of auditory neuron integrity.

ARTFit—A Quick and Reliable Tool for Performing Initial Fittings in Users of MED-EL Cochlear Implants

This study assessed the safety and performance of ARTFit, a new tool embedded in MAESTRO, the cochlear implant (CI) system software by MED-EL GmbH (Innsbruck, Austria). ARTFit automatically measures thresholds of the electrically evoked compound action potential (ECAP) to produce initial ‘maps’ (ECAPMAPs), i.e., configuration settings of the audio processor that the audiologist switches to live mode and adjusts for comfortable loudness (LiveECAPMAPs). Twenty-three adult and ten pediatric users of MED-EL CIs participated. The LiveECAPMAPs were compared to behavioral maps (LiveBurstMAPs) and to the participants’ everyday clinical maps (ClinMAPs). Four evaluation measures were considered: average deviations of the maximum comfortable loudness (MCL) levels of the LiveECAPMAPs and the LiveBurstMAPs from the MCLs of the ClinMAPs; correlations between the MCLs of the LiveECAPMAPs (MCL_ecap) and the LiveBurstMAPs (MCL_burst) with the MCLs of the ClinMAPs (MCL_clin); fitting durations; and speech reception thresholds (SRTs). All evaluation measures were analyzed separately in the adult and pediatric subgroups. For all evaluation measures, the deviations of the LiveECAPMAPs from the ClinMAPs were not larger than those of the LiveBurstMAPs from the ClinMAPs. The Pearson correlation between the MCL_ecap and the MCL_clin across all channels was r² = 0.732 (p < 0.001) in the adult and r² = 0.616 (p < 0.001) in the pediatric subgroups. The mean fitting duration in minutes for the LiveECAPMAPs was significantly shorter than for that of the LiveBurstMAPs in both subgroups: adults took 5.70 (range 1.90–11.98) vs. 9.27 (6.83–14.72) min; children took 3.03 (1.97–4.22) vs. 7.35 (3.95–12.77). SRTs measured with the LiveECAPMAPs were non-inferior to those measured with the ClinMAPs and not statistically different to the SRTs measured with the LiveBurstMAPs. ARTFit is a safe, quick, and reliable tool for audiologists to produce ECAP-based initial fitting maps in adults and young children who are not able to provide subjective feedback.

Intraoperative recordings of electromyogenic responses from the human stapedius muscle

Following surgical implantation of a cochlear implant, the external processor must be programmed individually, which is typically achieved by behavioral measurements, with the user indicating the perceived loudness between the threshold and the maximum comfort levels (MCLs). However, the stapedius reflex measurement could be used instead, as the basis for programming the fitting maps. The electrically evoked stapedius reflex threshold is known to have a high correlation with the MCLs and thus is used as an objective tool to determine the MCL, especially in children and non-cooperative patients. Previous studies demonstrated that the electromyogenic (EMG) activity of the stapedius muscle could be measured to determine stapedius reflex responses. The objective of this study was to demonstrate that intraoperative EMG recordings from the stapedius muscle could be performed with an EMG recording electrode designed for chronical implantation. Ten adult subjects with single sided deafness (SSD) participated in this study. The study was split up into a pre-, intra- and postoperative phase. In the preoperative phase the subjects were screened for the presence of the acoustic stapedius reflex by using a standard tympanometer in the ear to be implanted, while the contralateral ear was stimulated acoustically. During the intraoperative phase an EMG recording electrode was placed in the stapedius muscle and EMG responses were recorded during acoustical and electrical stimulation. The surgical procedure consisted of two interconnected procedures: A classical surgical approach for cochlear implantation with two additional surgical steps, and the temporary placement of an EMG recording electrode in the stapedius muscle made through an opening in the pyramidal eminence, allowing EMG recordings. The postoperative phase was used to evaluate the preservation of the stapedius reflex postoperatively at 1- and 6-months with contralateral acoustic and ipsilateral electrical stimulation. The EMG recording electrode could successfully be placed in the stapedius muscle in all subjects and was able to reliably record EMG signals from the stapedius muscle elicited by acoustic and electrical stimulation. Overall, EMG recordings were obtained intraoperatively in all subjects tested (8 out of 8 subjects). Contralateral acoustic stapedius reflexes were obtained in 6 out of 8 subjects and ipsilateral electrical stapedius reflex in 7 out of 8 subjects. In the postoperative phase, the preservation of the postoperative reflex was observed in 6 out of 10 subjects 1-month after surgery and in 8 out of 10 subjects 6-months after surgery. The study showed that intraoperative EMG recordings from the stapedius muscle can be performed with an EMG recording electrode designed for chronical implantation. The minimally invasive procedure is promising; in particular with regard to the future perspective of measurements in the long-term with an integrated closed-loop self-fitting system.

Clinical implications of intraoperative eABRs to the Evo®-CI electrode array recipients

INTRODUCTION

Electrically evoked auditory brainstem responses provide reliable clinical information to assist professionals in the auditory rehabilitation of cochlear implant users.

OBJECTIVE

This study aimed to investigate intraoperative evoked auditory brainstem response recordings in Evo®-cochlear implant electrode array recipients and its correlation with their behavioral levels and auditory performance.

METHODS

This is a retrospectivey study. Intraoperative evoked auditory brainstem responses were recorded in adult Evo®-cochlear implant electrode array recipients. Wave V latencies, amplitudes and interpeak III-V intervals were recorded in three different electrode locations and compared to the sentence recognition scores obtained from subjects after six months of device use. Evoked auditory brainstem responses thresholds were also recorded and compared to the behaviorally determined levels of the subjects in the sound processor activation.

RESULTS

Evoked auditory brainstem responses thresholds were significantly correlated with both, behavioral T- and C-levels and they were recorded at audible electrical stimulation levels in all subjects. There was a significant correlation between interpeak III-V interval recorded in the apical electrode and sentence recognition scores of the subjects.

CONCLUSIONS

Intraoperative evoked auditory brainstem responses can be used to establish audible levels for fitting the sound processor in Evo®-cochlear implant recipients and it could help professionals to plan further actions aiming to improve their auditory performance.

Prediction of Behavioral T/C Levels in Cochlear Implant Patients Based Upon Analysis of Electrode Impedances

BACKGROUND

Fitting cochlear implants in babies and noncooperative patients is cumbersome and time consuming. Therefore, objective parameters have been sought in order to predict the subjective threshold (T) and maximum comfort (C) levels. Measurements of the electrically evoked compound action potentials (ECAPs) have been widely used for this purpose, yet the correlation between these objective measures and the subjective T/C levels is weak to moderate.

PURPOSE

This article aims (1) to evaluate correlations between the subjective parameters of the fitting maps such as thresholds (T level) and maximum comfort levels (C level), the impedance of the electrode contacts, and the ECAP thresholds, and (2) to compare the value of the electrode impedances and the ECAP measures for prediction of the T/C levels.

RESEARCH DESIGN

Case review study in a quaternary otologic referral center.

STUDY SAMPLE

Ninety-eight consecutive CI patients were enrolled. The average age of the patients was 49 years. All patients were users of the Nucleus 24RECA (Freedom, Contour Advance-of-Stylet electrode) cochlear implant.

DATA COLLECTION AND ANALYSIS

Data on impedance of the electrode contacts and the behavioral T/C levels at the first fitting session (2-5 weeks after surgery) and at the 5th fitting session (4-6 months after surgery) have been retrospectively collected in 98 consecutive CI patients. Additionally, the intraoperative impedance values and the ECAP thresholds (tNRT) have been recorded.

RESULTS

Impedances of electrode contacts show significant strong negative correlations with the stabilized T/C levels at 4 to 6 months after implantation and are an important predictor for the behavioral T/C levels. They can explain R ² = 28 to 41% of the variability of the behavioral T/C levels. In multiple regression analysis electrode contact impedances can explain twice as much of the variability of the stabilized T/C levels than the tNRT values. The electrode impedances together with the tNRT values are able to explain R ² = 37 to 40% of the global variability of the T/C levels while the tNRT thresholds solely are able to explain only R ² = 5 to 14% of the T/C levels variability.

CONCLUSION

Impedances of electrode contacts correlate strongly with the stabilized behavioral T/C levels and may be used as an objective measure for fitting of cochlear implants.

Variability of fitting parameters across cochlear implant centres

OBJECTIVE

As a follow-up to the studies by Vaerenberg et al. (Sci World J 501738:1-12, 2014) and Browning et al. (Cochlear Implant Int 21(3):1-13, 2020), who used questionnaires, we determined whether there are between-centre variations in the fitting of cochlear implants by analysing the methodology, fitting parameters and hearing results of patients from four centres with real data. The purpose of this study is to highlight the lack of streamlined mapping guides and outcome measures with respect to cochlear implant (CI) fittings.

METHODS

A retrospective study with ninety-seven post-lingual adults with a nucleus cochlear implant placed between 2003 and 2013 was included to ensure at least 5 years of follow-up. The studied data were as follows: the methodology, including the fitter's professional background, the method of activation, the sequence of fitting sessions, the objectives measures and hearing outcomes; and the fitting parameters, including the speech processors, programming strategy, stimulation mode, T and C levels, T-SPL and C-SPL, maxima, pulse width, loudness growth and hearing results.

RESULTS

This investigation highlights some common practices across professionals and CI centres: the activation of a CI is behavioural; impedances are systematically measured at each fitting; and some parameters are rarely modified. However, there are also differences, either between centres, such as the sequences of fitting sessions (p < 0.05) or their approach to spectral bands (p < 0.05), or even within centres, such as the policy regarding T and C levels at high frequencies compared to those at low and mid-frequencies.

CONCLUSION

There are important variations between and within centres that reflect a lack of CI-related policies and outcome measures in the fitting of CI.

CLINICAL TRIALS REGISTRY

NCT03700268.

Evaluation of the quality of life in adults with cochlear implants: As good as the healthy adults?

PURPOSE

The aim of this study was to compare the quality of life (QoL) of adult CI users with the QoL of adults in the healthy and normal-hearing population.

MATERIALS AND METHODS

31 patients with CIs were included in the CI group, and 31 normal-hearing subjects were included in the control group. The QoL was evaluated using the World Health Organization Quality of Life-BREF (WHOQOL-BREF) for all subjects.

RESULTS

A comparison of the QoL of the CI group to that of the control group found that the QoL of healthy adults was better than that of the CI users. The results obtained for the subdomains of physical health, psychological health, and social relations showed statistically significant differences between the two groups (p < 0.05). There were no statistically significant differences between the groups in the subdomains of environment and general health (p > 0.05).

CONCLUSIONS

The effect of a hearing disability on daily life continues after the CI. As expected, adults with CIs still face challenges in their daily lives due to the hearing impairment.

Postoperative objective detecting techniques for cochlear implant children with inner ear malformation

OBJECTIVES

This study aims to investigate the changing characteristics and rules of electrically-evoked auditory brainstem response (EABR), electrically-evoked stapedius reflex threshold (ESRT) and neural response telemetry (NRT) after cochlear implant in children with inner ear malformation, and guide postoperative equipment debug.

METHODS

A total of 88 children with either normal cochlea (control group) or inner ear malformation (test group) received Australian 24 multi-channel cochlear implants. The EABR, ESRT and NRT thresholds at different time points within one year postoperatively and behavioral responses (T-level and C-level) after one year were detected. Furthermore, the changing characteristics and rules of these thresholds were analyzed.

RESULTS

The EABR, ESRT and NRT thresholds were all significantly higher at all time points in the test group than in the control group, but the general changing trends were similar. Particularly, these thresholds worsened at low frequencies and improved at high frequencies. Furthermore, EABR, ESRT and NRT thresholds gradually increased during the one year postoperative period. In addition, an extremely significant correlation was found between EABR and T-level and between ESRT and C-level, but a less significant correlation was found between NRT threshold and T-level in both groups.

CONCLUSIONS

The postoperative changes in characteristics and rules of EABR, ESRT and NRT thresholds among cochlear implant children with inner ear malformation were all the same as those with normal cochlea. Thus, these thresholds can be used to guide the postoperative equipment debug for cochlear implants into patients with inner ear malformation.

[Objective measures for setting the processors of cochlear implant systems : Use of discrimination functions and consideration of electrode profiles]

BACKGROUND

When setting the electrical stimulation level of cochlear implants during individual adjustment of the speech processor, especially in children, objective measures such as intracochlearly measured electrically evoked compound action potentials (eCAP) and intraoperative observation of electrically elicited stapedial reflexes (eSR) are indispensable. The benefit of these objective measures is based on the correlation between the derived response thresholds and psychometric data.

MATERIALS AND METHODS

The amplitude growth functions of eCAPs were measured intraoperatively for all electrodes in 30 ears of adult patients. The stimulus-dependent incidence of observable eSRs was recorded for all electrodes in 16 ears of adult patients. For evaluation of the data, new algorithms were applied which allowed the determination of thresholds without intervention of the investigator. Essential features were the conversion of observations into binary variables, and the consideration of logistic discrimination functions and their exceedance of a numeric threshold criterion.

RESULTS

Regarding the eCAP data, closer and significant correlations are observed between objective thresholds and psychometric measures in comparison to conventional procedures. Profiles are more efficient than pooled data. Significant correlations are also observed for eSR thresholds, albeit to a lesser extent and without an evident difference between profiles and pooled data.

CONCLUSION

Considering the by no means consistent international literature, the results illustrate the need for a consistent definition of response thresholds and the consideration of electrode profiles.