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Identifying cochlear implant channels with poor electrode-neuron interfaces: electrically evoked auditory brain stem
Julie Arenberg Bierer1, Kathleen F Faulkner, Kelly L Tremblay
1Department of Speech and Hearing Sciences, University of Washington, Seattle, Washington 98105, USA. jbierer@u.washington.edu
Cochlear implant (CI) channel assessment can be improved by correlating behavioral thresholds with electrically evoked auditory brainstem responses (EABRs). High CI thresholds and steep EABR growth functions indicate impaired channels, guiding patient-specific mapping for better hearing outcomes.
Area of Science:
- Audiology
- Neuroscience
- Biomedical Engineering
Background:
- Cochlear implant (CI) channel functionality is crucial for effective auditory perception.
- Previous research indicated that high-threshold CI channels, assessed via tripolar stimulation, exhibit broad psychophysical tuning curves.
- Assessing these channels using psychophysical methods is time-consuming and impractical for clinical settings, especially for pediatric patients.
Purpose of the Study:
- To compare behavioral measures and electrically evoked auditory brainstem responses (EABRs) using a spatially focused electrode configuration in cochlear implant users.
- To investigate if a physiological approach, specifically EABRs, can provide a similar assessment of CI channel functionality as time-intensive behavioral methods.
- To test the hypothesis that higher EABR thresholds correlate with steeper EABR amplitude growth functions, indicating a degraded electrode-neuron interface.
Main Methods:
- Data collected from six cochlear implant (Advanced Bionics HiRes 90k) users.
- Single-channel thresholds and most comfortable listening levels were measured using a partial tripolar configuration (varying electrical field size).
- EABRs were recorded for high and low behavioral threshold channels using monopolar (σ=0) and focused partial tripolar (σ≥0.50) configurations.
Main Results:
- EABR thresholds strongly correlated with behavioral thresholds across monopolar and partial tripolar configurations.
- Wave V amplitude growth functions showed shallower growth for partial tripolar compared to monopolar in low-threshold channels.
- Conversely, high-threshold channels exhibited steeper amplitude growth functions with the partial tripolar configuration.
Conclusions:
- Behavioral thresholds and EABRs measured with restricted stimuli can identify potentially impaired cochlear implant channels.
- High thresholds coupled with steep growth functions suggest suboptimal cochlear activation and degraded auditory perception.
- This method offers a clinically viable tool for rapid identification of impaired channels, enabling patient-specific mapping for improved speech and music perception.
