Intracochlear potential distribution with intracochlear and extracochlear electrical stimulation in humans

Area of Science:

• Neuroscience
• Biomedical Engineering
• Otolaryngology

Background:

• Cochlear implants are crucial for hearing restoration.
• Understanding current flow is vital for optimizing cochlear implant performance.
• The Ineraid multichannel cochlear implant offers direct access for measurements.

Purpose of the Study:

• To investigate intracochlear potential distributions during different stimulation modes.
• To determine the effectiveness of intracochlear versus extracochlear stimulation on auditory nerve activation.
• To correlate potential measurements with electrically evoked auditory brain stem responses.

Main Methods:

• Measurements of intracochlear potential distributions in subjects with Ineraid cochlear implants.
• Utilizing the electrode array for direct accessibility during stimulation.
• Employing different stimulation modes: intracochlear monopolar and extracochlear.

Main Results:

• Intracochlear monopolar stimulation confirmed low-resistance current pathways in the cochlea's basal turn.
• Extracochlear stimulation resulted in small intracochlear potential gradients, indicating minimal current flow along auditory nerve fibers.
• Intracochlear stimulation consistently elicited auditory brain stem responses, unlike weak or absent responses from extracochlear stimulation.

Conclusions:

• Intracochlear stimulation is more effective in activating auditory nerve fibers compared to extracochlear stimulation.
• Low-resistance pathways in the basal turn are significant for intracochlear current flow.
• Findings support the clinical efficacy of intracochlear stimulation for auditory nerve activation in cochlear implant users.