The Importance of the Electrode-Neural Interface in Supporting Long-Term Outcomes in Cochlear Implantation: Expert Opinion.

Background: Since first introduced in the mid-1980s, cochlear implant (CI) technology has significantly evolved to reach the current state of the art. Commencing with straight, lateral wall electrode arrays, advances in the last decade led to the development of slim perimodiolar arrays that lie closer to the electrically targeted spiral ganglion. Over the years, as a consequence of improving hearing benefits, CI indications have been steadily expanded. Today, individuals with moderately severe-to-profound sensorineural hearing loss, many with residual hearing in the low-frequency range, may receive a CI in one or both ears.

Summary: Before implantation, individual recipient characteristics, such as years of auditory deprivation, hearing thresholds, and speech understanding ability with conventional amplification, can have an effect on CI hearing outcomes. Also individuals with normal hearing/mild hearing loss in the low frequencies can also qualify for CI. Surgical procedures such as careful, soft surgery techniques are imperative to reduce cochlear trauma and optimize outcomes and can be supported by surgical guidance tools and drug therapies to help preserve the delicate intracochlear structures and also for patients with single-side deafness. Histopathological investigations provide evidence that support the design concept of slim perimodiolar electrode arrays. Modiolar proximity and scalar tympani location permit energy-efficient, focused electrical stimulation of the targeted neural interface, while minimizing injury to the fine structures of the intracochlear lateral wall and its blood supply.

Key Messages: Modiolar electrode arrays may provide highly consistent scala tympani placement and modiolar proximity which may improve functional hearing outcomes, compared to lateral wall electrode array results. Modiolar proximity can result in narrower spread of excitation, reduced channel interaction, lower electrical stimulation thresholds and may improve speech understanding. Reservation of functional residual low-frequency hearing is possible with both straight and perimodiolar electrode arrays.