Mechanical Effects of Cochlear Implants on Residual Hearing Loss: A Finite Element Analysis

The effects of cochlear implants on residual hearing loss is investigated through a finite element model of human auditory periphery consisting of the cochlea and middle ear. The simulation results show that a round window stiffness is the dominant factor in residual hearing loss. The increased round window stiffness to five times caused over 4 dB residual hearing loss at low frequencies below 500 Hz. Without considering round window ossification, inserting a cochlear implant can show at most 4 dB difference of residual hearing loss in magnitude from the no-implant case although the cochlear implant's geometry and position has been varied. If the stiffness of the round window is the same, the simulation results suggest to use a thin-straight-cochlear implant inserted into the lateral side in order to preserve residual hearing at frequencies below 700 Hz. In addition, when the distance between the basilar membrane and a cochlear implant is closer, the residual hearing loss becomes severe at high frequencies above 1 kHz. The results would be helpful for choice of a cochlear implant depending on a patient's condition.