Longitudinal Analysis of the Absence of Intraoperative Neural Response Telemetry in Children using Cochlear Implants

Abstract

Introduction Currently the cochlear implant allows access to sounds in individuals with profound hearing loss. The objective methods used to verify the integrity of the cochlear device and the electrophysiologic response of users have noted these improvements. Objective To establish whether the evoked compound action potential of the auditory nerve can appear after electrical stimulation when it is absent intraoperatively. Methods The clinical records of children implanted with the Nucleus Freedom (Cochlear Ltd., Australia) (CI24RE) cochlear implant between January 2009 and January 2010 with at least 6 months of use were evaluated. The neural response telemetry (NRT) thresholds of electrodes 1, 6, 11, 16, and 22 during surgery and after at least 3 months of implant use were analyzed and correlated with etiology, length of auditory deprivation, and chronological age. These data were compared between a group of children exhibiting responses in all of the tested electrodes and a group of children who had at least one absent response. Results The sample was composed of clinical records of 51 children. From these, 21% (11) showed no NRT in at least one of the tested electrodes. After an average of 4.9 months of stimulation, the number of individuals exhibiting absent responses decreased from 21 to 11% (n = 6). Conclusion It is feasible that absent responses present after a period of electrical stimulation. In our sample, 45% (n = 5) of the patients with intraoperative absence exhibited a positive response after an average of 4.9 months of continued electrical stimulation.

Troubleshooting Cochlear Implant Malfunction Using Neural Response Telemetry and Normal Saline

“…There is a dearth of literature where the surgeons have reported and shared their experiences with the intraoperative cochlear implant device failure attributable to hardware or software errors. Moura et al 3 in their case series followed up children with absent intraoperative NRT and concluded that 45% of such children responded positively to continued electrical stimulation after an average of 4.9 months, which they explained by hypothesizing that synaptic activity can be altered by continuous electric stimuli by providing sustained neurotrophic support to the auditory nerve. Thus, the absence of intraoperative NRT in the series was not due to hardware or software malfunction.…”

Electrically evoked compound action potential in children following cochlear implantation and its correlation with cochlear nerve diameter

“…2 Intraoperative NRT, in conjunction with electrode impedance data, can help indicate the integrity of the implanted electrodes and the electrode/auditory nerve interface, confirming that the implant functions correctly intraoperatively. 8 There have been differences of opinion regarding the usefulness of the intraoperative ECAP threshold in setting the map of the speech processor. 9,10 There is significant variation in neural response from patient to patient, and it indicates differences in stimulated neural population due to myelination, the presence of a dendritic population, and axonal integrity in the residual auditory neural population, according to Tanamati et al 11 It was also found that all the intraoperative ECAP thresholds were the highest values recorded.…”