Study Of Electro-Physiologic And Behavioral Parameters In Cochlear Implant Children

Cochlear implantation was introduced as a potential treatment option for profound, bilateral sensorineural hearing loss. Cochlear implants transform acoustic sounds into electrical signals that directly stimulate remaining auditory nerve fibers, thereby partially restoring hearing sensation to profoundly deaf patients.Many research suggest that that electrophysiologic potentials may be used to assist with programming the cochlear implant speech processor for very young children or individuals with cognitive or developmental delays. If these measures are to be used to assist with cochlear implant programming, it is important to determine whether, and to what extent, both physiologic and behavioral measures change over time, and whether changes are consistent across the two measures. Based on such data, we could better predict what time interval is best for making electrophysiologic measures to assist in device programming.Objective The primary goal of this study was to examine changes over time that may occur in electrode impedance, NRT threshold, and behavioral T-level and C-level over time in cochlear implant children. Secondary goals were to examine whether behavioral measures (T- and C-levels) and NRT thresholds exhibit the same trends over time and to determine the correlations between them. The third goal was to estimate thepossible clinical application of NRT threshold.Method Nine children implanted with the Nucleus CI24M cochlear implant participated in this study. NRT threshold and electrode impedance measures were collected intraoperatively, at initial stimulation, and at several subsequent visits up to 20 mo postinitial stimulation. Behavioral T-and C-levels were measured at initial stimulation and at the same time intervals as described above. NRT3. 0 and R126 1.3 softwares were used respectively.Results There was a significant increase in electrode impedance from the intra-operative test to initial stimulation , and a slight decrease in impedance from initial stimulation to the following visit, then remained stable by approximately 5-6 months after initial stimulation. NRT threshold exhibited significant decreases from the intra-operative test to initial stimulation and stabilized after initial stimulation. Behavioral T-levels remained relatively stable after initial stimulation, but the individual vatiations were significant. Behavioral C-levels exhibited an increasing trend up to 10-12 months after initial stimulation. Low negative correlations were found between NRT threshold and electrode impedance (r= — 0.332), and high positive correlations were found between NRT thresholds and MAP T- (r=0.863) and C-levels (r=0.786). Longitudinal trends in NRT thresholds mirrored T-level more closely than C-level.Conclusion The electrode impedance was stabilized by 5-6 months after initial stimulation and NRT threshold remained stable after initial stimulation. Group data revealed no significant change in behavioral T-levels, but variability across subjects was obvious. C-levels showed an increasing trend and was stabilized afer 10-12 mo. NRT technology provides a new objective method for estimating T-levels and C-levels for children who are unable to cooperate with audiologists during mapping after operation but it is difficult to estimate T-levels and C-levels accurately by...