gms | German Medical Science

The fitting of the C.I. is usually made considering only the minimum and maximum thresholds of nerve excitation and not the capacity of the nerve to discriminate a narrow bandwidth. Recently, new research highlighted the possibility to evaluate the spread of neural excitation and conversely the neural selectivity in Nucleus C.I. patients trough Neural Response Telemetry software. The evaluation of the spread of excitation (SOE) curves can provide information about the quality of the nerve firing and could support the clinicians in optimizing the fitting parameters. This study investigates the different patterns of SOE responses recorded from two groups of C.I. subjects: congenital deaf people for the first group and acquired deaf people for the second. For each group the Cohen methodology is used to investigate the SOE for some electrodes even during surgery. According to this methodology, a probe and a masker stimulus are sent to the nerve and then nerve fibers firing is recorded through NRT software, by means of a subtraction method to delete the artifacts. For each electrode, the SOE curve is built varying the masker electrode. The width of the SOE curves for the two groups of patients are compared in order to evaluate the effect of the early auditory deprivation on the nerve fiber firing.