EEG-based diagnostics of the auditory system using cochlear implant electrodes as sensors

Abstract

The cochlear implant is one of the most successful medical prostheses, allowing deaf and severely hearing-impaired persons to hear again by electrically stimulating the auditory nerve. A trained audiologist adjusts the stimulation settings for good speech understanding, known as “fitting” the implant. This process is based on subjective feedback from the user, making it time-consuming and challenging, especially in paediatric or communication-impaired populations. Furthermore, fittings only happen during infrequent sessions at a clinic, and therefore cannot take into account variable factors that affect the user’s hearing, such as physiological changes and different listening environments. Objective audiometry, in which brain responses evoked by auditory stimulation are collected and analysed, removes the need for active patient participation. However, recording of brain responses still requires expensive equipment that is cumbersome to use. An elegant solution is to record the neural signals using the implant itself. We demonstrate for the first time the recording of continuous electroencephalographic (EEG) signals from the implanted intracochlear electrode array in human subjects, using auditory evoked potentials originating from different brain regions. Furthermore, we show that the response morphologies and amplitudes depend crucially on the recording electrode configuration. The integration of an EEG system into cochlear implants paves the way towards chronic neuro-monitoring of hearing-impaired patients in their everyday environment, and neuro-steered hearing prostheses, which can autonomously adjust their output based on neural feedback.

Cortical Auditory Evoked Potentials Recorded Directly Through the Cochlear Implant in Cochlear Implant Recipients: a Feasibility Study

“…Recently, a research approach for recording EEG through the implanted electrodes was proposed by Somers et al 2021. They used 3 adults who were implanted with a very rare experimental percutaneous CI (Cochlear Nucleus, Ltd).…”

“…Recently, a report on the recording of EEG signals in response to intracochlear electrical stimulation and through a percutaneous connector attached to an external recording system, in 3 adult CI users, was reported (Somers et al 2021). In this invasive technique, instead of radiofrequency (RF) wireless connection, all implanted electrode leads are terminated to an implanted socket, which connects to an external EP recording system via a plug through the skull.…”

Toward Personalized Diagnosis and Therapy for Hearing Loss: Insights From Cochlear Implants

“…A follow-up multicenter randomized controlled trial has been planned to further validate this approach (82). CIs have also been used to record continuous electroencephalographic signals (83). Integration of an electroencephalographic system into CIs could allow for chronic neuromonitoring and pave the way toward dual-functional monitoring and therapeutic hearing devices that could continually adapt based on physiological feedback.…”

Classification of electrically-evoked compound action potentials in the parkinsonian subthalamic nucleus region

“…Such ECAP features have shown utility for assessing the degree of membrane polarization and thus target engagement with peripheral nerve [7], spinal cord [8–10], cochlear [11–14], retinal [15,16], and deep brain [2,17] stimulation. ECAP features have also been integrated as feedback signals to adjust therapies dynamically, including cochlear implants to streamline behavioral fitting procedures [18] and spinal cord stimulation to account for changes in the distance between the stimulating electrode(s) and the spinal cord during activities of daily living [9].…”