Abstract

Introduction: People with profound sensorineural hearing loss benefit from cochlear implantation. Nevertheless there are discrepancies as far as signal processing and hearing results are concerned. The large variety of patients in terms of age, cause and duration of deafness is one explanation. Neural response telemetry (tNRT) gives information about the function of the hearing nerve and the device. Previous studies couldn`t exactly show evident correlations between NRTs and cause or length of hearing-loss. Aim of the present study was the re-evaluation of tNRTs in a 12 months follow-up as a function of duration and reason of deafness. Patients and methods: 168 patients (82 female, 86 male) implanted at the department between 2008 and 2013 with an implant of Cochlear® were included into the study. 71 patients received a CI512 and 52 patients a CI24RE device, while 45 patients were supplied with the slim straight electrode array CI422. tNRTs were measured at each of the 22 electrodes intraoperatively, after 6 and after 12 months. Results: tNRT-values showed a reduction of tNRT-values over parts of the monitored period. Patients with Menière`s disease showed slightly higher values but the differences regarding the cause of deafness weren`t significant. Implant recipients with a mean time of hearing loss or a mean time of hearing aid supply showed a tendency of lower tNRTs. However the results weren’t significant. Conclusion: Within the first six months after CI implantation tNRTs decreased significantly. Patients with Menière's disease showed decent higher tNRTs. Patients with a period of deafness longer than two years presented lower tNRT thresholds. Participants with a mean time hearing aid supply prior CI surgery also provided a trend towards lower tNRTs. The impact of tNRTs on residual hearing in dependence of different shaped electrode arrays as well as the effect on speech perception should be focused in upcoming studies.

Keywords: Cochlea implant; NRT; ECAP; Hearing loss; Electrode; Deafness; Hearing aid