Cochlear implant-evoked cortical activation in children with cochlear nerve deficiency

OBJECTIVE: To report the results of cochlear implant-elicited cortical auditory evoked potentials (eCAEP) in children with cochlear nerve deficiency (CND). STUDY DESIGN: Case control series. SETTING: Tertiary academic referral center. PATIENTS: Seven children with CND that have a cochlear implant in their affected ear. Four children without CND served as controls. INTERVENTION(S): eCAEPs were elicited by activation of individual cochlear implant electrodes. MAIN OUTCOME MEASURE(S): Onset responses (P1-N1-P2 complex). RESULTS: Three of 7 CND children demonstrated eCAEP responses across a broad range of electrodes despite having limited or no open set speech perception abilities using their implants. Two of these children had eCAEPs that were characterized by substantial variability in latency, amplitude, and number of electrodes with identifiable responses. The remaining 4 ears with CND and poor speech perception had multiphasic responses that are inconsistent with eCAEPs. Non-CND ears with excellent speech perception abilities demonstrated robust responses on all electrodes stimulated. CONCLUSION: Abent eCAEP responses were indicative of poor open-set speech perception skills in all cases. However, eCAEP onset responses were measurable in some children with imaging evidence of CND, indicating probable cochlear nerve hypoplasia rather than aplasia. That some children with CND and poor speech perception had robust eCAEPs in some instances makes this particular measure of limited use for predicting good speech perception outcomes after cochlear implantation in these children. The origin of multiphasic responses remains to be determined but may be of somatosensory origin in some instances.