Utilizing Electrocochleography as a Microphone for Fully Implantable Cochlear Implants

Abstract

current cochlear implants (cis) are semi-implantable devices with an externally worn sound processor that hosts the microphone and sound processor. A fully implantable device, however, would ultimately be desirable as it would be of great benefit to recipients. While some prototypes have been designed and used in a few select cases, one main stumbling block is the sound input. Specifically, subdermal implantable microphone technology has been poised with physiologic issues such as sound distortion and signal attenuation under the skin. Here we propose an alternative method that utilizes a physiologic response composed of an electrical field generated by the sensory cells of the inner ear to serve as a sound source microphone for fully implantable hearing technology such as cis. Electrophysiological results obtained from 14 participants (adult and pediatric) document the feasibility of capturing speech properties within the electrocochleography (ecochG) response. Degradation of formant properties of the stimuli /da/ and /ba/ are evaluated across various degrees of hearing loss. preliminary results suggest proof-of-concept of using the ecochG response as a microphone is feasible to capture vital properties of speech. However, further signal processing refinement is needed in addition to utilization of an intracochlear recording location to likely improve signal fidelity.To date, it is estimated that as many as 466 million individuals worldwide have hearing loss as defined as an average hearing level of ≥35 dB HL by pure-tone audiometry 1 . Treatment options for hearing loss typically depend on the severity of the hearing loss. Cochlear implants (CI) have long been a treatment option for individuals with severe-to-profound hearing loss; however, with advancements in technology, candidacy criteria have expanded to include individuals with greater amounts of residual hearing. With this trend, the focus has shifted toward developing techniques and technology to allow for the preservation of residual hearing, as this has been shown to be important in obtaining optimal outcomes through the use of electric-acoustic stimulation. That is, in patients who receive CIs but maintain some useable residual hearing, the implanted ear can be stimulated using the ipsilateral combination of electric (CI) and acoustic (hearing aid) 2,3 .In attempts to achieve preservation of residual hearing, implementation of electrocochleography (ECochG) at the time of CI surgery has recently been described. ECochG is a tool that allows electrophysiological assessment of the peripheral auditory system (i.e., the cochlea and auditory nerve) by using acoustic stimulation. Specifically, ECochG has been used as a monitoring tool during CI surgery in an effort to provide real-time feedback of inner ear physiology that allows for modifying surgical technique in an attempt to avoid trauma caused by the electrode insertion, hence preserving residual hearing 4-6 . The use of ECochG is not new, but its use in CI surgery is novel. Specifically, new technology ...

Characterizing Electrophysiological Response Properties of the Peripheral Auditory System Evoked by Phonemes in Normal and Hearing Impaired Ears

“…It should be noted that given that the ECochG response is comprised of both cochlear and auditory nerve responses, simply calculating a differential curve does not result in complete isolation of hair cell response [see Forgues et al (2014) for in-depth review]. Riggs et al (2020) described this approach in a preliminary study and here we have expanded upon this approach with the addition of more participants. The SSIM is a mathematical model designed to compare two images (e.g., spectrograms) and determine their overall similarity based on three domains: luminance (intensity), contrast, and structure (contour) (Wang and Bovik 2002; Wang et al 2004).…”

Implantable neural electrodes: from preparation optimization to application

“…6(b)). 201 Recently, it was reported that the insertion of the Utah electrode array into the human occipital cortex can evoke visual perception (Fig. 6(c)).…”

“…198 (b) The most successful of the sensory implants is the cochlear implant, which has restored the hearing of the deaf. 201 (c) Stimulation of electrode arrays in the occipital cortex can evoke visual perception. 202 (d) DBS can effectively treat dyskinesia by stimulating nerve tissue at high frequency.…”

The remaining obstacles for a totally implantable cochlear implant

“…Apart from requiring functionally intact middle and external ears, the insertion of an additional component within the confined intracochlear space remains problematic. In order to overcome this limitation, Riggs et al [40 ▪ ] proposed to measure cochlear microphonic responses produced by the outer hair cells using the already existing cochlear implant-electrocochleography (CI-ECochG) technology. This ‘biological microphone’ would not require any additional sensors, since a portion of the electrode array itself could be used to obtain ECochG responses.…”