A patient receiving a cochlear implant has little predictive knowledge of how well he or she will ultimately perform in speech perception. Both pre- and intra-operative factors likely contribute to the wide variance in outcomes, but a key gap is identifying the specific causes of the variance. A more complete understanding of which factors affect outcomes would be useful to optimize rehabilitative strategies and improve electrode fitting, and to identify subjects who are underperforming and could benefit from additional ameliorative efforts. We have shown that assessing cochlear functional health with electrocochleography (ECochG) just prior to implantation can account for roughly half the variance in speech performance outcomes. However, surgical factors such as cochlear trauma during insertion, insertion depth and scalar location can also affect outcomes.
The first aim of this project will combine ECochG metrics for prior cochlear functional health and functional trauma caused during the surgery with CT imaging of electrode location in order to better explain the variance in speech perception outcomes. Because these surgical factors are independent from the residual physiology, we hypothesize that the variance in speech perception outcomes accounted for will increase by the addition of each type of information. During implantation, the surgeon has no knowledge of trauma caused or electrode location, other than approximate depth of insertion. We have previously used ECochG to detect acute cochlear trauma in animal models. Potentially, ECochG could be used to monitor trauma and determine electrode location relative to residual surviving hair cell and neural elements in humans. Specifically, an electrode placed outside the cochlea during insertion could be a sensitive monitor of ongoing trauma, while recordings from the advancing electrode could determine its location relative to responding elements.
The second aim of this project is to characterize intraoperative changes in acoustic responses - with the goal of characterizing trauma ? as the ground work for an intraoperative monitor capable of providing accurate feedback to the surgeon is obtained. The hypotheses are that reductions in response with an extracochlear electrode during insertion are likely indicative of surgical trauma, whereas increases and reductions in response when using intracochlear recordings from the implant array itself are indicative of both trauma and electrode location.
The first aim i s intended to improve understanding of the causes of variance in outcomes to provide optimal, patient-specific rehabilitative strategies.
The second aim i s intended to reduce cochlear trauma and improve electrode placement during surgery. Along with the superb environment at UNC Chapel Hill, exceptional mentoring by Dr. Fitzpatrick and Dr. Manis, dedicated industry support, and a comprehensive training plan, this fellowship will provide a critical foundation to build my future career as an independently funded physician- scientist in the field of otolaryngology.
An outstanding problem for the cochlear implant community is accounting for the very high variance in speech perception outcomes. Identifying the patient and surgical factors which affect speech perception after implantation will ideally improve patient counseling and guide auditory rehabilitation. This project will combine electrophysiology and advanced imaging techniques in order to assess cochlear health before, during, and after implantation in order to predict speech performance outcomes and minimize surgical trauma.
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| Scott, William C; Giardina, Christopher K; Pappa, Andrew K et al. (2016) The Compound Action Potential in Subjects Receiving a Cochlear Implant. Otol Neurotol 37:1654-1661 |
