Electrophysiological Correlates of Behavioral Comfort Levels in Cochlear Implantees: A Prospective Study

Cochlear Implant Activation in the Immediate Postoperative Period in the Operating Room

Introduction  Cochlear implant (CI) activation usually takes place at ∼ 30 days postoperative (PO). In our service, CI surgery is performed with local anesthesia and sedation, so activation is possible with the patient's cooperation, immediately after the CI surgery, still in the operating room (OR). Objective  The objective of the present study was to provide the patient with hearing experience with the CI and to assess auditory perception immediately after surgery while still in the OR, as well as to compare impedance telemetry (IT), neural response telemetry (NRT), and comfort (C) level at two moments: in the OR and at the definitive activation, ∼ 30 days PO. Methods  Nine adult patients (12 ears) with acquired (postlingual) deafness were included. Auditory perception was evaluated through the Ling Six Sound Check, musical instruments, and clapping, presented in two different programming maps, elaborated using t-NRT, and comparing IT, NRT, and C level between the two moments. Results  We observed that while still in the OR, the patient can already present auditory detection and recognition responses. The values of IT, NRT threshold (t-NRT), and C on both dates differed, with statistical significance. Conclusion  We concluded that it is possible to provide the patient with an auditory experience with the CI immediately after surgery, and that the auditory experience and the values of electrode IT, NRT, and C vary significantly between the two moments.

Prediction of behavioral MCL using electrophysiological responses in children using MED-EL implant

The present study aimed to correlate the various electrophysiological tests of ECAP, EABR and ESRT with programming parameters. If there is a correlation between them, fitting formulae to be derived to predict programming parameters. Further this fitting formula was validated on a clinical population. 22 children between age range of 5-12 years using MED-EL implant participated study. Electrophysiological tests of Electrically evoked compound Action Potential (ECAP), Electrical Evoked Stapedial Reflex Threshold (ESRT) and Electrically Evoked Auditory Brain Stem Responses (EABR) were measured on electrodes no 1,4, 8, and 11. Based on Pearson correlation analysis, there was a moderate correlation observed between each of electrophysiological tests with MCL level. Fitting formulae of ECAP with either ESRT or EABR were found to be accurately predict the MCL level. These fitting formulae were clinically validated on 6 children using Sonata implant with OPUS 2 processor. Two new programs with MCL were predicted using combination of ECAP with EABR and ECAP with ESRT as parameters in the fitting formulae. These programs were given to the participants to use for two weeks. Predicted MCLs were found to slightly higher (about 2qu to 5qu) than original MCL level. Reliability analysis indicated that the formulae predicted MCL with good accuracy. Speech perception and sound field thresholds were measured in the participants' Everyday program and two predicted programs. When ECAP & EABR were the parameters, the predicted program had improved audibility as reflected in sound field thresholds as compared to those obtained with other two programs. Based on Freidman test, the results indicated that significantly lower thresholds were found for both ECAP & EABR, or ECAP & ESRT based programs when compared to Everyday program. However, speech perception scores were not significantly different among the program as per Freidman test. Thus, both the fitting models were clinically validated. The findings imply that it is not always advisable to run all three electrophysiological testing to predict the MCL levels in clinical population. It would save lot of time to run just two tests to predict the MCL in difficult to test population.

Speech-in-noise performance in objectively determined cochlear implant maps, including the effect of cognitive state

OBJECTIVE

Cochlear Implant (CI) programming based on subjective psychophysical fine-tuning of loudness scaling involves active participation and cognitive skills and thus may not be appropriate for difficult-to-condition populations. The electrically evoked stapedial reflex threshold (eSRT) is an objective measure that is suggested to provide clinical benefit to CI programming. This study aimed to compare speech reception outcomes between subjective and eSRT objectively determined CI maps for adult MED-EL recipients. The effect of cognitive skills on these skills was further assessed.

METHODS

Twenty-seven post lingually hearing-impaired MED-EL CI recipients were recruited, 6 with mild cognitive impairment (MCI- 4 male, 79 years ± 5), 21 with normal cognitive function (5 male, 63 years ± 12). Two MAPs were generated: a subjective MAP and an objective MAP in which eSRTs determined maximum comfortable levels (M-Levels). Participants were randomly divided into two groups. Group A trialled the objective MAP for two weeks before returning for outcome assessment. During the following two weeks, Group A trialled the subjective MAP before returning for outcome assessment. Group B trialled MAPs in reverse. Outcome measures included the Hearing Implant Sound Quality Index (HISQUI), Consonant-Nucleus-Consonant (CNC) word test, and Bamford-Kowal-Bench Speech-in-Noise (BKB-SIN) test.

RESULTS

eSRT based MAPS were obtained in 23 of the participants. A strong relationship was demonstrated between global charge between eSRT-based and psychophysical-based M-Levels (r = 0.89, p < .001). The Montreal Cognitive Assessment for the Hearing Impaired (MoCA-HI) testing identified 6 CI recipients with MCI (MoCA-HI total score ≤23). The MCI group was older (63, 79 years), but were not otherwise different in sex, duration of hearing loss or duration of CI use. For all patients, no significant differences were found for sound quality or speech in quiet scores between eSRT-based and psychophysical-based MAPs. However, psychophysically determined MAPs showed significantly better speech-in-noise reception (6.74 vs 8.20-dB SNR, p = .34). MoCA-HI scores showed a significant, moderate negative correlation with BKB SIN for both MAP approaches (Kendall's Tau B, p = .015 and p = .008), with no effect on the difference between MAP approaches.

CONCLUSION

Results indicate eSRT-based methods provide poorer outcomes than psychophysical-based method. While speech-in-noise reception is correlated with MoCA-HI score, this affected both behaviourally and objectively determined MAPs. The results suggest fair confidence in the eSRT-based method as a guide for setting M-Level for difficult-to-condition CI populations in simple listening conditions.

The optimal probe tone frequency for eSRT measurements at individual electrodes in children with cochlear implants

BACKGROUND

Higher probe tone frequencies have been shown to increase the elicitation rates in electrically evoked stapedius reflex threshold (eSRT) measurements.

OBJECTIVES

To determine the optimal probe tone frequency for contralateral eSRT measurements at individual electrodes in children with unilateral cochlear implants and to assess the relationship between eSRTs for this frequency and most comfortable levels (M-levels).

MATERIALS AND METHODS

Contralateral eSRT measurements with three probe tone frequencies (226, 678, and 1000 Hz) at individual electrodes were performed on 26 paediatric Advanced Bionics cochlear implant recipients.

RESULTS

The elicitation rates of eSRTs for 226, 678, and 1000 Hz probe tones were 73.08% (57/78), 88.46% (69/78), and 88.46% (69/78), respectively. The average eSRT for the 1000 Hz probe tone was significantly lower than those for 226 and 678 Hz probe tones (p<.001 and p=.009, respectively). ESRTs for the 1000 Hz probe tone and M-levels were significantly correlated at all tested electrodes (all p<.001).

CONCLUSIONS AND SIGNIFICANCE

The optimal probe tone frequency for contralateral eSRT measurement at individual electrodes in children with unilateral cochlear implants is 1000 Hz. ESRTs for the 1000 Hz probe tone are significantly correlated with M-levels and can be used to guide the M-levels setting in these children.

Acoustic component programming in children with cochlear implants using electrocochleography

OBJECTIVE

Objective measurements improve reliability and effectiveness of hearing assessment and cochlear implant (CI) programming in young children. In CI recipients with acoustic hearing in the implanted ear, electrocochleography (ECochG) can be conducted using intracochlear electrodes. The cochlear microphonic (CM) portion of ECochG has been shown to correlate with pure-tone audiometric thresholds in adult and paediatric CI recipients. Our goal was to determine if ECochG thresholds can be used to appropriately fit the acoustic component to the implanted ear in children.

DESIGN

Prospective.

STUDY SAMPLE

Eight children (aged 3.5-15.5 years, 10 ears) implanted with Advanced Bionics HiFocus Mid-Scala electrode array were recruited. CI ear acoustic thresholds were measured behaviourally and via ECochG. Two acoustic component enabled CI programs were created using the two sets of thresholds. Age and language appropriate speech outcomes and subjective feedback were obtained.

RESULTS

Speech scores were equivalent with the behavioural and ECochG thresholds programs. Subjectively, the ECochG thresholds program was preferred by 7/8 subjects. One subject preferred to use an electric only program.

CONCLUSION

Our data suggest that ECochG thresholds can be used to supplement the behavioural clinical methods and aid the reliable fitting of the acoustic component in paediatric CI recipients.

Do the minimum and maximum comfortable stimulation levels influence the cortical potential latencies or the speech recognition in adult cochlear implant users?

INTRODUCTION

Cochlear implants (CI) programming is based on both the measurement of the minimum levels required to stimulate the auditory nerve and the maximum levels to generate loud, yet comfortable loudness. Seeking for guidance in the adequacy of this programming, the cortical auditory evoked potentials (CAEP) have been gaining space as an important tool in the evaluation of CI users, providing information on the central auditory system.

OBJECTIVE

To evaluate the influence of mishandling of electrical stimulation levels on speech processor programming on hearing thresholds, speech recognition and cortical auditory evoked potential in adult CI users.

MATERIAL AND METHODS

This is a prospective cross-sectional study, with a sample of adult unilateral CI users of both sexes, aged at least 18 years, post-lingual deafness, with minimum experience of 12 months of device use. Selected subjects should have average free field hearing thresholds with cochlear implant equal to or better than 34 dBHL and monosyllable recognition different from 0%. Individuals who could not collaborate with the procedures or who had no CAEP recordings were excluded. Participants were routinely programmed, and the map was named MO (optimized original map). Then three experimentally wrong maps were made: optimized original map with 10 current units below the maximum comfort level (C), named MC- (map minus C); optimized original map with minus 10 current units at minimum threshold level (T), named MT- (map minus T) and optimized original map with 10 current units above minimum level (T), named MT + (map plus T). In all programs, participants underwent free-field auditory thresholds from 250Hz to 6000Hz, recorded sentences and monosyllabic recognition tests presented at 65dB SPL in quiet and in noise, and free field CAEP evaluation. All tests were performed in an acoustically treated booth, in a randomized order of map presentation. Data were compared by Wilcoxon test.

RESULTS

Thirty individuals were selected and signed an informed consent form. The MC- map provided worsening of all free field thresholds, quiet and noise speech recognition, and P1 wave latency delay with significant difference from the results with the MO map. The MT- map worsened the hearing thresholds and statistically significantly reduced the P2 wave latency; MT+ map improved free field thresholds except 6000Hz, worsening speech recognition, without statistical significance.

CONCLUSIONS

The results suggest that maximum levels below the optimal thresholds lead to worse cochlear implant performance in both hearing thresholds and speech recognition tests in quiet and noise, increasing CAEP component P1 latency. On the other hand, the manipulation of minimum threshold levels showed alteration in audibility without significant impact on speech recognition.

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/dB_HL and 10 μV at 50 dB_HL compared with 0.04 μV/dB_HL and 3 μV at 50dB_HL 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.

Effect of Cochlear Implant Electrode Array Design on Electrophysiological and Psychophysical Measures: Lateral Wall versus Perimodiolar Types

BACKGROUND AND OBJECTIVES

The present study aims to investigate whether the cochlear implant electrode array design affects the electrophysiological and psychophysical measures.

SUBJECTS AND METHODS

Eighty five ears were used as data in this retrospective study. They were divided into two groups by the electrode array design: lateral wall type (LW) and perimodiolar type (PM). The electrode site was divided into three regions (basal, medial, apical). The evoked compound action potential (ECAP) threshold, T level, C level, dynamic range (DR), and aided air conduction threshold were measured.

RESULTS

The ECAP threshold was lower for the PM than for the LW, and decreased as the electrode site was closer to the apical region. The T level was lower for the PM than for the LW, and was lower on the apical region than on the other regions. The C level on the basal region was lower for the PM than for the LW whereas the C level was lower on the apical region than on the other regions. The DRs on the apical region was greater for the PM than for the LW whereas the DR was narrower on the apical region than on the other regions. The aided air conduction threshold was not different for the electrode design and frequency.

CONCLUSIONS

The current study would support the advantages of the PM over the LW in that the PM had the lower current level and greater DR, which could result in more localized neural stimulation and reduced power consumption.

Cochlear Implant in Prelingually Deaf Children: Our Experience

Retrospective study of the prelingual cochlear implantation programme under government scheme done at medical college hospital in central India. Forty-two prelingually deaf children screened and sent for cochlear implantation at our centre From March 2015 to Feb 2018 were reviewed with respect to their age, sex, preimplantation hearing aid use, surgical technique for cochlear implantation, type of FDA (USA) approved cochlear implant, post operative speech therapy and its outcome with respect to categories of auditory perception and speech intelligibility scoring were compared for children younger than 4 years and older than 4 years. For outcome measurement non parametric statistical method was used for any significance between the two groups. There was a wide range of children implanted ranging from 2 to 7 years. Both varia and mastoidectomy and posterior tympanotomy method of cochlear implantations were done with good rate complete insertion and electrode activation. There was no significant difference between the two group with regard to CAP and SIR outcomes after 1 year. In order to get better outcomes with respect to the speech language development, there is need to strengthen the early identification and cochlear implantation before 4 years of age in government approved schemes.