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.
Highlights
Cochlear implants traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss
This study extends the (Koka et al, 2016) study to evaluate whether cochlear microphonic (CM) can be used to estimate bone conduction (BC) thresholds in implanted patients with residual hearing
Direct coupling electromagnetic artifacts were observed when stimulus levels were above vibrotactile thresholds, thereby indicating that artifacts exist at high levels
Summary
Cochlear implants traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss. Given the evolution of electrode and signal-processing technology and improved surgical techniques, individuals with low-frequency residual hearing are able to experience benefit from a cochlear implant (Balkany et al, 2006; Fraysse et al, 2006). In order to benefit optimally from EAS technologies, residual hearing in these subjects must be preserved. At least 50% of subjects lose their residual hearing after surgery (James et al, 2005; Balkany et al, 2006; Brown et al, 2010; Lenarz et al, 2013; Roland et al, 2016). The loss of residual hearing is attributed mainly to, direct trauma to the basilar membrane (Roland and Wright, 2006; Li et al, 2007) and not due to any potential
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