An Objective Estimation of Air-Bone-Gap in Cochlear Implant Recipients with Residual Hearing Using Electrocochleography

Abstract

Although, cochlear implants (CI) traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss, a recent trend is to implant individuals with residual low-frequency hearing. Notably, many of these individuals demonstrate an air-bone gap (ABG) in low-frequency, pure-tone thresholds following implantation. An ABG is the difference between audiometric thresholds measured using air conduction (AC) and bone conduction (BC) stimulation. Although, behavioral AC thresholds are straightforward to assess, BC thresholds can be difficult to measure in individuals with severe-to-profound hearing loss because of vibrotactile responses to high-level, low-frequency stimulation and the potential contribution of hearing in the contralateral ear. Because of these technical barriers to measuring behavioral BC thresholds in implanted patients with residual hearing, it would be helpful to have an objective method for determining ABG. This study evaluated an innovative technique for measuring electrocochleographic (ECochG) responses using the cochlear microphonic (CM) response to assess AC and BC thresholds in implanted patients with residual hearing. Results showed high correlations between CM thresholds and behavioral audiograms for AC and BC conditions, thereby demonstrating the feasibility of using ECochG as an objective tool for quantifying ABG in CI recipients.

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

“…Until now, in response to acoustic stimulation in CI users it was required to use an external system for recording CAEP through scalp electrodes (Makhdoum et al 1998;Hoppe et al 2001;Sharma et al 2002;Kelly et al 2005;Cowper-Smith et al 2013;Brown et al 2015). In principle, the method used in the current study for recording CAEP is based on the commonly used wireless communication between the CI receiver and speech processor (back telemetry) for recording eCAP or ECochG in CI (Koka et al 2017a;2017b;Attias et al 2020). While the ECochG in CI is recorded within a short recording time window following acoustic stimulation, the back telemetry technology used in the current study allows for a longer recording time window.…”

“…While the prediction of the electric thresholds level can be based on eCAP or eABR responses, eSRT helps to estimate the electrical comfortable sensation level (Brown et al 1990; Wolfe et al 2017; de Andrade et al 2018; Kosaner et al 2018). ECochG is an objective measure for the estimation of the acoustic residual hearing threshold (Koka et al 2017a; 2017b; Attias et al 2020). eABR estimated thresholds have been reported to be closer to the behavioral thresholds than the eCAP estimated thresholds (Brown et al 2000).…”

Electrocochleography in cochlear implantation: Development, applications, and future directions

“…The results show a significant correlation between CM thresholds and behavioral thresholds in CI patients. 38 , 48 , 52 , 54 , 55 , 56 , 57 CM thresholds thus offer an objective method to assess hearing sensitivity in CI subjects who cannot participate in behavioral audiometry 57 and can even be used to assess air-bone gaps in implanted patients. 55 The new AIM system from Advanced Bionics allows providers to perform a quick estimation of the CM thresholds immediately after CI electrode placement, which may be helpful in understanding mechanisms driving the loss of residual hearing immediately after electrode placement.…”

Relationship Between Intraoperative Electrocochleography Responses and Immediate Postoperative Bone Conduction Thresholds in Cochlear Implantation

“…During intraoperative ECochG measurements, an alternating polarity acoustic stimulus is used to elicit a difference response or cochlear microphonics (DIF/CM) from the stereocilia of the surviving outer hair cells (13). In CI patients with postoperative residual hearing, the DIF/CM response strongly correlates with postoperative behavioral air conduction (AC) thresholds in the implanted ear (2,(14)(15)(16)(17). Therefore, it is logical to assume that intraoperative decrease in DIF/CM signal corresponds with a decrease in outer hair cell function.…”