[Threshold dynamics of the auditory nerve electrically evoked compound action potential in implanted children]

To study the dynamics of thresholds of the electrically evoked compound action potential of the auditory nerve (ECAP) during neural responce telemetry (NRT) intraoperatively, at the time of activation of the cochlear implantation system (CI) and after 3 and 6 months.

The study included 50 children aged 1 year to 4 years with bilateral sensorineural deafness, operated on by Nucleus CI512 Profile + CP900 CI systems («Cochlear», Australia). In all patients, the electrode array was fully inserted. The dynamics and thresholds of ECAP were recorded and assessed in dynamics: when performing NRT intraoperatively, when the CI system was activated, and after 3 and 6 months. To assess the thresholds, the 1st, 6th, 11th, 16th and 22nd electrodes of the multichannel electrode array were selected.

The average threshold values and the NRT threshold profile determined intraoperatively and during measurements at different times after the activation of the CI system were significantly different (p<0.001), while the average postoperative results were characterized by relative stability. It was shown that the thresholds determined on the electrodes located in the middle of the electrode lattice are more stable than the thresholds determined on the apical and basal electrodes. In most patients, the NRT threshold values determined at the time of the activation of the CI system and after 3 and 6 months were significantly lower than the thresholds determined intraoperatively. The data obtained allow us to conclude that NRT is a stable and accurate technique that allows you to objectify the process of setting up an individual card for the stimulation of the speech processor at the rehabilitation stage after cochlear implantation.