The positioner effects electrode interaction in pediatric cochlear implants

Abstract

Problem: Address the effect of an implant electrode’s cochlear position on the degree of electrode interaction in pediatric patients with Clarion HiFocus arrays using objective measurements well-suited for very young implant recipients. Methods: PATIENTS: A volunteer sample of 16 patients (range 2.2 to 12.8; mean age, 6.3 years) implanted with the HiFocus electrode were tested; 9 patients with the positioner and 7 without. MAIN OUTCOME MEASURES: Electrically evoked whole nerve action potentials (EAPs) were measured using the CII’s neural response imaging. An electrode interaction function was measured by varying the masker electrode position while maintaining probe and recording electrode positions. Interaction functions were obtained at 3 probe locations (electrodes 5, 9, and 13) and 3 supra-threshold intensities. Results: While EAP thresholds did not vary along the electrode array, growth function slope increased from basal to apical location ( P < 0.01). No difference in growth function slope or EAP threshold was associated with the positioner. Interaction among apical electrodes was greater than among basal electrodes ( P < 0.01). No difference in electrode interaction could be attributed to the positioner alone ( P > 0.01). Conclusion: Both electrode interaction and growth function slope were greater toward the cochlear apex than at the cochlear base. We attribute this difference to a combination of systematic variations in electrode/neural element distances and surviving cochlear ganglion cells. Behavioral testing will determine the implication of different degrees of electrode interaction on electrical hearing. Significance: No systematic study of EAPs in children has been reported. These findings will help us understand the relationship between the auditory nerve response to electrical stimuli and the perception of hearing. Support: None reported.