The effect of current amplitude and multi-electrode stimulation on eSRT for auditory fitting in cochlear implants...

Area of Science:

• Neuroscience and Biomedical Engineering
• Auditory Electrophysiology
• Cochlear Implant Technology

Background:

• Personalized cochlear implant (CI) programming relies on neurophysiologic measures.
• The electrically evoked Stapedius Reflex Threshold (eSRT) is a key measure for assessing auditory nerve response.
• Understanding factors influencing eSRT is crucial for optimizing CI efficacy.

Purpose of the Study:

• To evaluate the impact of stimulation current amplitude and electrode count on eSRT.
• To assess the correlation between eSRT and the Most Comfortable Loudness level (MCL).
• To identify optimal stimulation parameters for reliable eSRT-based MCL estimation in pseudo-monophasic CI systems.

Main Methods:

• Seventeen adult patients with Oticon Medical CI devices participated.
• Stimulation involved varying current amplitudes (low/high) and electrode group sizes (1, 3, 5) across cochlear regions.
• eSRT detection rates and correlation with MCL were analyzed under different stimulation conditions.

Main Results:

• Multi-electrode stimulation (G3, G5) significantly improved eSRT detection compared to single electrodes (G1).
• Higher stimulation amplitudes generally increased eSRT detection rates.
• A strong correlation (r=0.64-0.87) was consistently observed between eSRT and MCL across conditions.

Conclusions:

• Increasing stimulation amplitude and utilizing multi-electrode configurations enhance eSRT detection in pulse-width modulated CIs.
• Optimal parameters for MCL estimation from eSRT were identified (e.g., high-amplitude contra-lateral G5).
• These findings support the use of eSRT for more accurate and personalized CI programming.