Perimodiolar electrode position: Effects on thresholds, comfort levels, impedance measurements, and neural response telemetry

OBJECTIVE: This multicenter study describes the effects of perimodiolar electrode position on 50 adult patients (31 with an implanted Nucleus 24 Contour perimodiolar hugging electrode array [Cochlear Limited, Lane Cove, NSW, Australia] and 19 with an implanted straight electrode array) with a severe-to-profound sensorineural hearing loss. MATERIALS AND METHODS: In all patients, intraoperative impedance measurements were performed; threshold levels (T-levels), comfort levels (C-levels), and dynamic range were measured 1 and 3 months after surgery; and a real-time 3dimensional computed tomographic reconstruction was obtained to evaluate the insertion depth and perimodiolar placement of the electrode array. RESULTS: Preliminary results showed that intraoperative electrically evoked compound action potentials (ECAPs) measured via neural response telemetry (NRT) correlated better with the behavioral C-levels in patients with a Nucleus Contour cochlear implant. T-levels for the apical electrodes were statistically significantly lower in patients with the perimodiolar electrode array than in patients with the straight electrode. CONCLUSION: The insertion depth of the Nucleus Contour electrode array, which was positioned near the modiolus, was greater than that of the straight electrode array. Electrode impedances uncorrected for differences in electrode surface area were relatively higher in the Contour group than in the straight electrode group. Tlevels for the Contour group were comparatively lower than those in the straight electrode group, although C-levels (except for those in apical channels) were not statistically significantly different between the groups. Preliminary results indicated that intraoperative ECAPs measured via NRT correlated better with the behavioral C-levels for patients with a Contour cochlear implant. From the University Hospital Insular of Gran Canaria (Armacias, D. Perez), the University Hospital "La Fe," Valencia (C. Morera, L. Caballe), the University Clinic of Navarra, (M. Manrique, A. Huarte), and the Otologic Center "Garcia Ibanez," Barcelona (L. Garcialbanez), Spain