Evaluation of NRT and behavioral measures for MAPping elderly cochlear implant users

Abstract

We investigated the acceptability of electrophysiologically derived MAPs and the effect of these MAPs on speech perception in elderly adults using Nucleus 24 cochlear implants. Eight implant recipients aged 75 years or older trialed an electrophysiologically derived MAP and a behavioral MAP. The electrophysiologically derived MAP was based on the threshold and maximum comfort level for electrode 10 and evoked compound action potential thresholds measured on six electrodes using neural response telemetry (NRT). Word perception at 55 dB SPL and sentence perception in noise at 70 dB SPL were assessed after six weeks take-home experience and again after an additional two weeks of experience. During the final two weeks of take-home experience participants indicated their preferred MAP for different listening situations. The NRT derived MAP estimated behavioral T levels well, but underestimated behavioral C levels for apical electrodes in some subjects. Speech perception with NRT derived MAPs was comparable to speech perception with behaviorally measured MAPs. MAPs estimated from NRT data provided good speech perception outcomes for elderly implant recipients and were well tolerated.

Differences between electrically evoked compound action potential (ECAP) and behavioral measures in children with cochlear implants operated in the school age vs. operated in the first years of life

“…Several studies have reported higher thresholds and smaller ECAP amplitudes in the basal electrodes than in the apical electrodes [29,36,38,43,60]. The dominant paradigm to explain these findings has been that there is a smaller number of preserved vital neurons in the basal part of the cochlea, which is consistent with postmortem pathohistological studies of the temporal bones [9,17,29,33,38,43,46].…”

“…The dominant paradigm to explain these findings has been that there is a smaller number of preserved vital neurons in the basal part of the cochlea, which is consistent with postmortem pathohistological studies of the temporal bones [9,17,29,33,38,43,46]. An alternative explanation is that the electrode array in the basal part of the cochlea is more distant from SGC or that there is a higher risk for surgical trauma in that part of the cochlea [29,60]. Furthermore, several studies have reported variability in the ECAP thresholds, amplitudes, morphologies, and MAP levels along the array, indicating that the spatial distribution of neuronal populations stimulated by a particular electrode is heterogeneous [24,38].…”

“…Many of them were performed with adult subjects i.e., in groups of postlingually deaf adults with various, mostly acquired, deafness etiologies [34,35,38,44,46,52,60]. Some other studies, in accordance with the design of the studies, included subjects of wide range of ageschildren and adults together [29,31,61].…”

TNRT profiles with the Nucleus Research Platform 8 system

“…Hughes et al, 2000; Mason et al, 2001; Gordon et al, 2002; Kaplan-Neeman et al, 2004) as well as the elderly (e.g. Pedley et al, 2007). …”

Cortical potentials as predictors of outcomes with adult cochlear implant recipients - preliminary findings

“…Results from intraoperative electrophysiological testing such as neural response telemetry (NRT) and electrical auditory brainstem response (EABR) have been reported as possible indicators of post-operative outcomes with children (King et al, 2006) and adults including the elderly (Pedley et al, 2007). Poor morphology (defi ned as the absence of one or more waveforms, poorly formed waves or delayed waves) of the intra-operative EABR could indicate that the recipient will have some diffi culty integrating the signal from their cochlear implant, particularly initially.…”