Cochlear Implant Pediatric Patient THR-Level Determination Based on Electrical Cochlear Response

Introduction A problem to be solved when fitting a cochlear implant (CI), is to determine the electrical current dynamic range (EDR) in the stimulation electrodes. Nowadays the EDR is calculated based on behavioral response at the threshold of audible detection to an electrical stimulus, THR-level. Currently THR-level determination is made by following psychophysical or objective methods, or a combination of both. The psychophysical approach has limitations when using in uncooperative subjects, and the objective approach suffers from methodological restrictions such as test is performed under no real CI use conditions and does not consider the sound processor role. The Electrical Cochlear Response (ECR) is an implanted patient scalp potential which represents the auditory nerve response to an incoming pip tone; whenever stimulation electrical current level due to incoming sound be high enough to evoke an auditory nerve response. Objective. We propose an objective method for THR-level determination based on ECR threshold. Methodology. ECR threshold was obtained from the six most apical electrodes in 18 pediatric implanted patients, as evidence of the auditory nerve response to a minimum intensity pip. Results. ECR threshold amplitude, on average 5.6 ± 1.7 µV, does not depend on sound stimulus intensity, electrode location or CI brand but on local cochlear responsiveness properties next to electrode. Conclusion. Being ECR threshold measurement an objective approach, it is appropriate for young children and can be applied immediately after first CI programming. Reducing with this the period necessary to achieve an optimal electrical stimulation and therefore improving CI patient rehabilitation expectations.