Abstract
Cochlear implantation has successfully restored the perception of hearing for nearly 200 thousand profoundly deaf adults and children. More recently, implant candidature has expanded to include those with considerable natural hearing which, when preserved, provides an improved hearing experience in noisy environments. But more than half of these patients lose this natural hearing soon after implantation. To reduce this burden, biosensing technologies are emerging that provide feedback on the quality of surgery. Here we report clinical findings on a new intra-operative measurement of electrical impedance (4-point impedance) which, when elevated, is associated with high rates of post-operative hearing loss and vestibular dysfunction. In vivo and in vitro data presented suggest that elevated 4-point impedance is likely due to the presence of blood within the cochlea rather than its geometry. Four-point impedance is a new marker for the detection of cochlear injury causing bleeding, that may be incorporated into intraoperative monitoring protocols during CI surgery.
Highlights
Cochlear implantation has successfully restored the perception of hearing for nearly 200 thousand profoundly deaf adults and children
We and others have begun to monitor cochlear function during cochlear implantation[7,8,9,10], using the CI’s own electrodes to monitor the electrophysiological response of the ear to acoustic stimulation. This technique, known as electrocochleography, has provided valuable information to guide surgeons during the operation; if the electrophysiological response is preserved during surgery, residual hearing is better after implantation[7,8,9,10]
Realtime intraoperative monitoring of hearing was undertaken during implantation, where electrocochleography (ECochG) was recorded directly from the tip electrode on the implant array, in response to a high intensity acoustic tone burst (500 Hz)
Summary
Cochlear implantation has successfully restored the perception of hearing for nearly 200 thousand profoundly deaf adults and children. We and others have begun to monitor cochlear function during cochlear implantation[7,8,9,10], using the CI’s own electrodes to monitor the electrophysiological response of the ear to acoustic stimulation. This technique, known as electrocochleography, has provided valuable information to guide surgeons during the operation; if the electrophysiological response is preserved during surgery, residual hearing is better after implantation[7,8,9,10]. When the trauma causes bleeding (Fig. 1D,E), the volume of perilymph available to conduct current is effectively reduced by the presence of blood cells and the current will pass around the cells, not through them (Fig. 1F)
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