Transient and steady state auditory responses with direct acoustic cochlear stimulation

Area of Science:

• Neuroscience
• Audiology
• Biomedical Engineering

Background:

• Direct acoustic cochlear implants offer a novel approach for severe to profound mixed hearing loss.
• Objective evaluation of the auditory pathway is crucial for these patients.
• Auditory evoked potentials (AEPs) provide a means for objective assessment.

Purpose of the Study:

• To develop a stimulation setup for electroencephalography (EEG) recordings in patients with direct acoustic cochlear implants.
• To demonstrate the feasibility of recording auditory brainstem responses (ABRs) and auditory steady-state responses (ASSRs).
• To analyze the correlation between electrophysiological and behavioral hearing thresholds.

Main Methods:

• Developed a direct stimulation setup for ABR and ASSR recordings.
• Recorded ABRs and 40/80 Hz ASSRs in three implanted subjects.
• Compared responses from direct and acoustic stimulation setups, analyzing amplitude growth and phase delay.

Main Results:

• The direct stimulation setup successfully eliminated artifacts, enabling noninvasive AEP recording.
• ABR and ASSR latencies were comparable to acoustic stimulation.
• Electrophysiological thresholds were objectively determined, with a mean difference of 12 dB for 40 Hz ASSRs compared to behavioral thresholds.

Conclusions:

• Auditory evoked potential measurements using the developed direct stimulation setup are feasible and clinically relevant.
• This method holds promise for intraoperative feedback on actuator coupling.
• Further investigation is warranted to optimize this objective audiological assessment technique.