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.

The Role of the P1 Latency in Auditory and Speech Performance Evaluation in Cochlear Implanted Children

Auditory deprivation affects normal age-related changes in the central auditory maturation. Cochlear implants (CIs) have already become the best treatment strategy for severe to profound hearing impairment. However, it is still hard to evaluate the speech-language outcomes of the pediatric CI recipients because of hearing-impaired children with limited speech-language abilities. The cortical auditory evoked potential (CAEP) provides a window into the development of the auditory cortical pathways. This preliminary study is aimed at assessing electrophysical characteristics of P1-N1 of electrically CAEP in children with CIs and at exploring whether these changes could be accounted for in auditory and speech outcomes of these patients. CAEP responses were recorded in 48 children with CIs in response to electrical stimulus to determine the presence of the P1-N1 response. Speech perception and speech intelligibility of the implanted children were further evaluated with the categories of auditory performance (CAP) test and speech intelligibility rating (SIR) test, respectively, to explore the relationship between the latency of P1-N1 and auditory and speech performance. This study found that P1 and N1 of the intracochlear CAEP were reliably evoked in children fitted with CIs and that the latency of the P1 as opposed to that of N1 was negative in relation to the wearing time of the cochlear implant. Moreover, the latency of the P1 produced significantly negative scores in both CAP and SIR tests, which indicates that P1 latency may be reflective of the auditory performance and speech intelligibility of pediatric CI recipients. These results suggest that the latency of P1 could be used for the objective assessment of auditory and speech function evaluation in cochlear-implanted children, which would be helpful in clinical decision-making regarding intervention for young hearing-impaired children.

Systematic review of cochlear implantation in adults with asymmetrical hearing loss

BACKGROUND

Rapid advances in cochlear implantation has witnessed an expanding spectrum for candidacy worldwide. This includes a subgroup of adults with asymmetrical hearing loss who have a wide range in their hearing capacity between the two ears. As per guidelines they are not included in mainstream candidacy for CI across the world. Evidence is now emerging to support the benefits of CI in AHL.

METHODS

This review analyzed literature regarding the outcomes of CI in AHL. Primary outcome measure was to assess audiological benefits and secondary outcome measure was to assess hearing related quality of life. 15 relevant articles, published worldwide between 2009 and 2019 were chosen. CASP checklist for systematic reviews was used to ascertain the quality of literature. The strength of recommendations from each study was analyzed and classified as strong, moderate, weak or none based on GRADE guidelines.

RESULTS

Heterogeneity in samples was obvious and samples varied largely between the studies. The levels of evidence ranged from systematic review to expert opinion, but overall they reflected positively on both audiological and QOL benefits.

CONCLUSION

CI provides important auditory and QOL benefits in AHL, but there is no high level evidence as yet to strongly support CI for AHL. A long term multi-centric study is necessary to influence a change in practice for a growing population of AHL.Trial registration: ClinicalTrials.gov identifier: NCT03052920.

Cortical Auditory Evoked Potentials with Simple (Tone Burst) and Complex (Speech) Stimuli in Children with Cochlear Implant

Introduction  The registry of the component P1 of the cortical auditory evoked potential has been widely used to analyze the behavior of auditory pathways in response to cochlear implant stimulation. Objective  To determine the influence of aural rehabilitation in the parameters of latency and amplitude of the P1 cortical auditory evoked potential component elicited by simple auditory stimuli (tone burst) and complex stimuli (speech) in children with cochlear implants. Method  The study included six individuals of both genders aged 5 to 10 years old who have been cochlear implant users for at least 12 months, and who attended auditory rehabilitation with an aural rehabilitation therapy approach. Participants were submitted to research of the cortical auditory evoked potential at the beginning of the study and after 3 months of aural rehabilitation. To elicit the responses, simple stimuli (tone burst) and complex stimuli (speech) were used and presented in free field at 70 dB HL. The results were statistically analyzed, and both evaluations were compared. Results  There was no significant difference between the type of eliciting stimulus of the cortical auditory evoked potential for the latency and the amplitude of P1. There was a statistically significant difference in the P1 latency between the evaluations for both stimuli, with reduction of the latency in the second evaluation after 3 months of auditory rehabilitation. There was no statistically significant difference regarding the amplitude of P1 under the two types of stimuli or in the two evaluations. Conclusion  A decrease in latency of the P1 component elicited by both simple and complex stimuli was observed within a three-month interval in children with cochlear implant undergoing aural rehabilitation.

Cortical Auditory Evoked Potentials to Evaluate Cochlear Implant Candidacy in an Ear With Long-standing Hearing Loss: A Case Report

OBJECTIVES

We describe a novel use of cortical auditory evoked potentials in the preoperative workup to determine ear candidacy for cochlear implantation.

METHODS

A 71-year-old male was evaluated who had a long-deafened right ear, had never worn a hearing aid in that ear, and relied heavily on use of a left-sided hearing aid. Electroencephalographic testing was performed using free field auditory stimulation of each ear independently with pure tones at 1000 and 2000 Hz at approximately 10 dB above pure-tone thresholds for each frequency and for each ear.

RESULTS

Mature cortical potentials were identified through auditory stimulation of the long-deafened ear. The patient underwent successful implantation of that ear. He experienced progressively improving aided pure-tone thresholds and binaural speech recognition benefit (AzBio score of 74%).

CONCLUSIONS

Findings suggest that use of cortical auditory evoked potentials may serve a preoperative role in ear selection prior to cochlear implantation.

USES AND LIMITATIONS OF ELECTROPHYSIOLOGY WITH HEARING AIDS

There is currently a strong interest among both audiologists and hearing researchers to find a physiological measure that can be used as a marker of how amplified sounds are processed by the brain (i.e., hearing aid fitting) or how the brain changes with exposure to amplified sounds (i.e., hearing aid acclimatization). Currently, auditory evoked potentials are used, or proposed to be used, for both of these purposes to some degree. It is clear from the literature that some of these uses are potentially useful clinically while others are quite problematic. The current state of aided cortical auditory evoked potentials will be discussed relative to their application to hearing aid fitting/verification and in understanding hearing aid acclimatization. Future areas of promise as well as current gaps in the literature will also be addressed.

Speech perception and cortical auditory evoked potentials in cochlear implant users with auditory neuropathy spectrum disorders

OBJECTIVE

To characterize the P(1) component of long latency auditory evoked potentials (LLAEPs) in cochlear implant users with auditory neuropathy spectrum disorder (ANSD) and determine firstly whether they correlate with speech perception performance and secondly whether they correlate with other variables related to cochlear implant use.

METHODS

This study was conducted at the Center for Audiological Research at the University of São Paulo. The sample included 14 pediatric (4-11 years of age) cochlear implant users with ANSD, of both sexes, with profound prelingual hearing loss. Patients with hypoplasia or agenesis of the auditory nerve were excluded from the study. LLAEPs produced in response to speech stimuli were recorded using a Smart EP USB Jr. system. The subjects' speech perception was evaluated using tests 5 and 6 of the Glendonald Auditory Screening Procedure (GASP).

RESULTS

The P(1) component was detected in 12/14 (85.7%) children with ANSD. Latency of the P(1) component correlated with duration of sensorial hearing deprivation (*p=0.007, r=0.7278), but not with duration of cochlear implant use. An analysis of groups assigned according to GASP performance (k-means clustering) revealed that aspects of prior central auditory system development reflected in the P(1) component are related to behavioral auditory skills.

CONCLUSIONS

In children with ANSD using cochlear implants, the P(1) component can serve as a marker of central auditory cortical development and a predictor of the implanted child's speech perception performance.