Minimization of cochlear implant artifact in cortical auditory evoked potentials in children

ObjectivesIn congenitally deaf children fit with a cochlear implant, little is known about the maturation of the auditory cortex. Cortical auditory evoked potentials are a useful methodology to study the auditory cortical system of children with cochlear implants. Nevertheless, these recordings are contaminated by a cochlear implant artifact. The objective of this study was to use independent component analysis to minimize the artifact of the cochlear implant to study cortical auditory evoked potentials.Study designProspective study.MethodA total of 5 children ranging in age from 21 to 49 months who were fitted with a cochlear implant for at least 6 months were included in this study. The stimuli were pure tones (750 Hz, 200 ms duration, 70 dB SPL) presented with an irregular interstimulus interval (1000–2000 ms) via loud speakers. The cortical auditory evoked potentials were recorded from 17 Ag–AgCl electrodes referenced to the nose. The peak latency and amplitude of each deflection culminating at the fronto-central and temporal sites were analyzed.Main outcome measuresThe P100–N250 peak latencies and amplitudes of the cortical auditory evoked potentials recorded from children fitted with cochlear implants. Scalp map potentials distributions were done for each child for the N250 wave.ResultsThe use of independent component analysis permitted to minimize the cochlear implant artifact for the five children. Cortical auditory evoked potentials were recorded at fronto-central and temporal sites. Scalp map potentials distributions for the N2 wave showed activation of temporal generators contralateral at the CI for the five children.ConclusionThis preliminary electrophysiological study confirms the value and the limits of independent component analysis. It could allow longitudinal studies in cochlear implant users to examine the maturation of auditory cortex. It could also be used to identify objective cortical electrophysiological measures to help the fitting of CIs in children.