Auditory processing following sequential bilateral cochlear implantation: A pediatric case study using event-related potentials

Background: Past studies using event-related potentials (ERPs) elicited to single syllable stimuli in unilateral and bilateral cochlear implant users have suggested reorganization of the auditory cortex within the first 6-8 mo postimplantation (Sharma et al, 2002a, 2002b, 2006; Bauer et al, 2006). Better behavioral performance with bilateral implants is expected when bilateral cochlear implantation is performed simultaneously or when a second implant is provided after a short interval of auditory deprivation at a younger age (Murphy and O'Donoghue, 2007; Wolfe et al, 2007; Steffens et al, 2008). Purpose: The purpose of this case study was to examine changes in various levels of auditory processing using single syllable and word-level stimuli in a child who received bilateral cochlear implants sequentially. Research Design: Brain responses were recorded at pre-activation and 2, 4, and 6 mo postactivation of a second cochlear implant using passive paradigms involving two types of auditory perception (speech and word level). Auditory stimuli were presented at 75 dB SPL(A) through a speaker above the participant's head with the cochlear implant(s) at typical user settings. Cortical responses were recorded from 128 electrodes. Study Sample: The participant was a 6-yr-old female with the diagnosis of bilateral profound sensor-ineural hearing loss. She received her first cochlear implant in her right ear (2 yr, 4 mo of age), underwent revision surgery (3 yr, 6 mo of age), and later received a bilateral cochlear implant (6 yr, 8 mo of age). Data Collection and Analysis: For the purposes of the case study, the waveforms were visually examined for morphology and amplitude or latency differences between conditions. The ERPs of the cochlear implant user were compared to those from a group of five children with normal hearing. Conclusions: The results suggest that sequential bilateral cochlear implantation contributes to improved auditory processing beyond the benefits of the single implant even in users with an extended period of deafness in the later-implanted ear.