Objective measurements of auditory nerve recovery function in nucleus CI 24 implantees in relation to subjective preference of stimulation rate.

Objective: Setting the optimal rate of stimulation for individual cochlear implant recipients is critical to the successful functional outcome of cochlear implantation. In the absence of an objective methodology, cochlear implants are currently fitted by means of a time-consuming (and therefore expensive) trial-and-error process of limited accuracy. The aim of this study was to evaluate a possible relationship between the patient's subjectively preferred stimulation rate and an objective measurement of auditory nerve recovery time.

Material And Methods: Eleven recipients of Nucleus CI 24 implants initially fitted with a speech processor using the ACE speech-coding strategy at a rate of 900 Hz were introduced to 2 other stimulation rate options, 1200 and 1800 Hz, at 2 different fitting sessions and asked to choose their preferred rate. Preferences were compared with objective measurements of auditory nerve recovery time obtained using the refractory recovery function of neural response telemetry.

Results: The auditory nerve recovery time for individuals with a subjective preference for a slow stimulation rate was longer than that for individuals who preferred a fast stimulation rate, with significant differences between the 2 groups for 3 tested electrodes (7, 11 and 15): p = 0.024, 0.009 and 0.03, respectively (Mann-Whitney test).

Conclusion: The association observed between the subjective stimulation rate preference and measurements of auditory nerve recovery time indicates that the measured auditory nerve recovery time can be used as a reliable predictor for setting up a basic stimulation rate of a particular individual's map, thus reducing the cost of the technology and significantly increasing its effectiveness.