Predicted versus measured maximum stimulation levels in the nucleus 24 cochlear implant

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Philip M. McCabe - Committee Chair


Cochlear implant programming necessitates accurate setting of programming levels, including maximum stimulation levels (C Levels), of all active electrodes. Generally, these levels can be set adequately utilizing clinical techniques. The measurement of the electrically-evoked compound action potential of the eighth nerve using a technique called Neural Response Telemetry (NRT) has been suggested as a means of estimation when clinical methods are insufficient, such as in the very young child. However, these methods require co-application of clinical and NRT measurements or the addition of correction factors to NRT thresholds in order to estimate C-Levels.Clinical and NRT measurements were obtained from 22 adult Nucleus 24 users to develop reliable predictions for C Levels. Multiple regression analysis was performed for each electrode to determine predictive abilities of various factors including NRT threshold, slope of the NRT growth function, age, length of deafness, length of cochlear implant use and electrode impedance. NRT threshold and slope of the growth function were the only factors with statistically significant relationships with C Levels.Depending on the electrode, R2 ranged from 0.391 to 0.769, with only 1 out of 22 electrodes showing non-significance at the p = 0.002 level when these two factors were utilized. Overall, results indicated that NRT can reliably predict C Levels using the NRT threshold and slope of the NRT growth function as factors. This use of regression is currently the most accurate means of predicting C Levels from NRT when clinical measures are unavailable; however, further research is necessary to investigate its applicability for other patient populations (e.g., pediatric Nucleus 24 cochlear implant patients).


Health Sciences, Audiology

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