The relationship between cortical auditory evoked potentials (CAEPs) and speech perception in children with Nurotron(®) cochlear implants during four years of follow-up

Clinical experience with the Nurotron™ cochlear implant in a Spanish-speaking postlingual population: Clinical safety and audiological results

OBJECTIVE

to assess clinical safety and postoperative audiological outcomes in postlingual deafness Spanish speaking patients, who underwent surgery with Nurotron™ cochlear implant.

MATERIAL AND METHODS

Retrospective descriptive case series study. We performed follow-up of complications and audiological measurements before and after cochlear implantation. Patients with bilateral severe to profound sensorineural hearing loss or patients with unilateral deafness with/without tinnitus were included. Repeated-measures within-subjects for assess pure tone thresholds and speech performance (bilingual test) with a detailed monitoring to establish security or adverse effects were performed. Analysis of variance tests, repetitive measures, were used for statistical analysis.

RESULTS

31 patients were included, 17 (54.8%) men and 14 (45.2%) women. Mean age at the time of surgery was 49.82 ± 18.8 years. The mean follow-up of the group was 31.56 ± 9.57 months (minimum = 19.6 months and maximum = 52.50 months). As major complication one patient (3.23%) had a hard failure that required removal and re-implantation. 25.8% of the patients presented minor complications, the most frequent being vertigo/unsteadiness in 22.6%. The mean of language discrimination (free field at 65 dB SPL) was 62.19% ± 16.66; being 69.82% ± 7.35 in the group of severe to profound bilateral sensorineural hearing loss. A statistically significant reduction was observed in patients with tinnitus, assessed using the visual analogue scale, preoperative = 7.2 ± 1,6 vs postoperative (18months postoperative) = 1.7 ± 1.3 (p < .001).

CONCLUSIONS

The Nurotron™ cochlear implant shows satisfactory audiological results, in accordance with what has been reported in the literature. Minor complications were similar to previous studies, but the percentage of hard failure should continue to be observed, which was higher than other reports with comparable follow-up.

Electrically evoked auditory cortical responses elicited from individually fitted stimulation parameters in cochlear implant users

OBJECTIVE

To investigate electrically evoked auditory cortical responses (eACR) elicited from the stimulation of intracochlear electrodes based on individually fitted stimulation parameters in cochlear implant (CI) users.

DESIGN

An eACR setup based on individual fitting parameters is proposed. A 50-ms alternating biphasic pulse train was used to stimulate apical, medial, and basal electrodes and to evoke auditory cortical potentials (N1-P2 complex).

STUDY SAMPLE

The eACR setup proposed was validated with 14 adult CI users.

RESULTS

Individual and grand-average eACR waveforms were obtained. The eACR amplitudes were lower in the basal than in the apical and medial regions. Earlier N1 latencies were found in CI users with lower maximum comfortable loudness levels and shorter phase duration in response to apical stimulation, while medial and basal stimulation resulted in earlier N1 latencies and larger N1-P2 amplitudes in users with longer CI experience.

CONCLUSIONS

eACR could be elicited by direct intracochlear stimulation using individual fitting parameters with a success rate of 71%. The highest cortical peak-to-peak amplitudes were obtained in response to apical stimulation. Unlike the P2, the N1 component appeared to be a consistent cortical potential to determine eACR and gain knowledge of the auditory processing beyond the cochlea in CI users. HighlightseACR can be elicited through direct stimulation of intracochlear electrodes.Stimulation of apical and medial regions yielded the highest N1-P2 amplitudes.CI users with lower maximum comfortable loudness levels had shorter N1 latencies during apical stimulation.The present dataset of mainly well-performing CI users suggests better cortical processing, that is, higher amplitudes and shorter latencies of N1.The N1 potential appears a more consistent and reliable potential than the P2 to determine eACR responses in CI users.

A Review of Speech Perception of Mandarin-Speaking Children With Cochlear Implantation

Objective: This paper reviewed the literature on the development of and factors affecting speech perception of Mandarin-speaking children with cochlear implantation (CI). We also summarized speech outcome measures in standard Mandarin for evaluating auditory and speech perception of children with CI.

Method: A comprehensive search of Google Scholar and PubMed was conducted from March to June 2021. Search terms used were speech perception/lexical tone recognition/auditory perception AND cochlear implant AND Mandarin/Chinese.

Conclusion: Unilateral CI recipients demonstrated continuous improvements in auditory and speech perception for several years post-activation. Younger age at implantation and longer duration of CI use contribute to better speech perception. Having undergone a hearing aid trial before implantation and having caregivers whose educational level is higher may lead to better performance. While the findings that support the use of CI to improve speech perception continue to grow, much research is needed to validate the use of unilateral and bilateral implantation. Evidence to date, however, revealed bimodal benefits over CI-only conditions in lexical tone recognition and sentence perception in noise. Due to scarcity of research, conclusions on the benefits of bilateral CIs compared to unilateral CI or bimodal CI use cannot be drawn. Therefore, future research on bimodal and bilateral CIs is needed to guide evidence-based clinical practice.

Central Auditory Nervous System Stimulation through the Cochlear Implant Use and Its Behavioral Impacts: A Longitudinal Study of Case Series

The purpose of this study was to investigate, over a period of five years, the cortical maturation of the central auditory pathways and its impacts on the auditory and oral language development of children with effective use and without effective use of a Cochlear Implant (CI). A case series study was conducted with seven children who were CI users and seven children with normal hearing, with age- and gender-matched to CI users. The assessment was performed by long-latency auditory evoked potentials and auditory and oral language behavioral protocols. The results pronounced P1 latency decrease in all CI users in the first nine months. Over five years, five children with effective CI use presented decrease or stabilization of P1 latency and a gradual development of auditory and oral language skills, although, for most of the children, the electrophysiological and behavior results remained poor than their hearing peers' results. Two children who stopped the effective use of CI after the first year of activation had worsened auditory and oral language behavioral skills and presented increased P1 latency. A negative correlation was observed between behavioral measures and the P1 latency, the P1 component being considered an important clinical resource capable of measuring the cortical maturation and the behavioral evolution.

Objective electroencephalography-based assessment for auditory rehabilitation of pediatric cochlear implant users

The cochlear implant (CI) has an effective habilitation modality for hearing-impaired children by promoting sound perception, vocalization, and language ability. However, the major challenge that remained was the lack of assessment standards for pediatric CI users, especially prelingually deaf children, to evaluate hearing rehabilitation effectiveness. In the present study, we conducted an oddball paradigm with stimuli varying in pure-tone, syllable, and tonal sounds. After implantation, we utilized cortical auditory evoked potential (CAEP) and mismatch negativity (MMN) to obtain time-domain analysis; meanwhile, the source localization was investigated to obtain spatial accuracy of the plasticity in the auditory cortex. P1 started to emerge at the third month after implantation, but its peak level was not significant until the sixth month. The temporal lobe was activated between the third and sixth months after implantation. The MMN waveform was basically normal approximately after 12 months. These results suggest that the auditory system goes through a critical period of rapid development between three and six months and enters a maturation period after 12 months. This work indicates that CAEPs are more suitable for assessing the early auditory system reconstruction, while MMN performs better in evaluating the advanced auditory function. Furthermore, source localization has proven to be an efficient tool in exploring auditory cortex plasticity, especially for pediatric CI users.

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.

Relationship between aided cortical auditory evoked responses and aided behavioral thresholds

OBJECTIVES

The present study aimed to determine the relationship between aided cortical auditory evoked potentials and aided behavioral thresholds. Secondary aims of the study were to investigate the relationship between age and Cortical Auditory Evoked Potentials latencies, and to analyze the relationship between the /m/, /g/ and /t/ stimuli.

METHOD

Therefore, 20 subjects (4-8 years old) who diagnosed with moderate to severe hearing loss were included in the study. Behavioral pure-tone audiometry was performed using supra-aural earphones. After verification of the settings of hearing aid settings, aided behavioral thresholds were determined in the free field. Aided CAEPs were recorded using the HEARLab system in a sound-treated room. The /m/, /g/, and /t/ speech stimuli were applied with durations of 30, 20, and 30 ms respectively.

RESULTS

A strong correlation was found between aided cortical auditory evoked responses at the level of 55 dB SPL and aided behavioral thresholds in the free field(r=0.86). We showed that the CAEP latencies were not correlated with the age (/m/ stimulus [r=-0.051; p=0.830], /g/ stimulus [r=-0.053; p=0.825], and /t/ stimulus [r=0.121; p=0,610]). The mean latency of the /m/ stimulus at 55 dB SPL intensity was longer than those of the /g/ and /t/ stimuli.

CONCLUSION

The results of the present study demonstrated that the use of the cortical auditory evoked potentials is clinically useful for measuring the hearing aid benefit. The CAEP can predict the aided behavioral thresholds in children with moderate hearing loss.

Outcomes of Cochlear Implantation in Auditory Neuropathy Spectrum Disorder and the Role of Cortical Auditory Evoked Potentials in Benefit Evaluation

Objective

To compare the outcomes of cochlear implantation (CI) in children with auditory neuropathy spectrum disorder (ANSD) and age-matched controls with profound sensorineural hearing loss, using categories of auditory performance (CAP), speech intelligibility rate (SIR), meaningful auditory integration scale (MAIS), and meaningful use of speech scale (MUSS), and to determine the role of Cortical Auditory Evoked Potentials (CAEP) in benefit evaluation after CI.

Methods

Ten patients (8 males and two females) with ANSD who underwent CI were included in the study. Auditory and speech scores were compared between baseline and after 12 months of habilitation in children with ANSD. Post CI speech scores in children with ANSD were compared with the control group (age-matched children with profound sensorineural hearing loss) at 12 months of habilitation. P1 latency of CAEP has a good correlation with auditory and speech scores in children with ANSD in the study group.

Results

Significant benefits were seen in children with ANSD who underwent CI compared to the baseline CAP and SIR scores and one year after habilitation. There is no statistically significant difference in outcomes between the two groups with CI (ANSD and profound sensorineural hearing loss) (p-value: CAP=1.00, SIR=0.84, MAIS=0.33, MUSS=0.08). Speech perception in noise test (SPIN) scores in children with ANSD were 63% and 80% with 0 dB signal noise ratio (SNR) and +10dB SNR, respectively. P1 wave of CAEP has a good correlation with the subjective outcomes.

Conclusion

CI in children with ANSD has showed benefits comparable to children with profound sensorineural hearing loss. CAEP is a useful tool in objectively assessing cortical maturity in children with ANSD following CI.

Characterization of Volume-Based Changes in Cortical Auditory Evoked Potentials and Prepulse Inhibition

The auditory evoked startle reflex is a conserved response resulting in neurological and motor activity. The presence of a mild prepulse immediately before the main pulse inhibits startle responses, though the mechanism for this remains unknown. In this study, the electroencephalography (EEG) data recorded from 15 subjects was analyzed to study the N1 and P2 components of cortical auditory evoked potentials (CAEPs) evoked by 70, 80, 90, 100, and 110 dB stimuli both in the presence and absence of 70 dB prepulses. Results without a prepulse showed an evolution of N1 amplitudes, increasing with stimulus intensity and showing largely significant differences. Results from prepulse trials only showed noteworthy changes in peak-to-peak amplitude in the 100 dB condition. Prepulse and non-prepulse conditions were then compared using peak amplitudes and theta power. Prepulse conditions significantly decreased the amplitude for both components in the 110 dB condition, i.e., pre-pulse inhibition, but significantly increased the N1 amplitude in the 70 dB condition, i.e., pre-pulse facilitation. Similarly theta band power significantly increased in the 70 dB prepulse condition and significantly decreased in the 110 dB prepulse condition. These results expand the basis of knowledge regarding how CAEPs change and elaborate on their neural function and representation.