Neural response telemetry (NRT) permits in situ intracochlear recordings of the electrically evoked compound action potential from the auditory nerves using scala tympani electrodes. The recorded NRT waveforms can generally be categorized under either single positive peak or double positive peak waveforms. This is similar to the observations from Stypulkowski and van den Honert, who suggested that the double peak complex arises from two components that could be axonal and dendritic in origin, respectively. Using a simple mathematical model which linearly combines two separate waveforms similar in shape but differing in amplitude and latencies, it was possible to simulate the various NRT waveform categories. The simulation results support the view that the two waveform components originate from dendritic or axonal processes and implies that the shape of the response waveform may provide information about the degree of neural survival in the stimulated cochlea. This information could be useful for determining optimal speech coding parameters for cochlear implant users on an individual basis. AbstractNeural response telemetry (NRT) permits in situ intracochlear recordings of the electrically evoked compound action potential from the auditory nerves using scala tympani electrodes. The recorded NRT waveforms can generally be categorized under either single positive peak or double positive peak waveforms. This is similar to the observations from Stypulkowski and van den Honert, who suggested that the double peak complex arises from two components that could be axonal and dendritic in origin, respectively. Using a simple mathematical model which linearly combines two separate waveforms similar in shape but differing in amplitude and latencies, it was possible to simulate the various NRT waveform categories. The simulation results support the view that the two waveform components originate from dendritic or axonal processes and implies that the shape of the response waveform may provide information about the degree of neural survival in the stimulated cochlea. This information could be useful for determining optimal speech coding parameters for cochlear implant users on an individual basis.
One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T-and C-levels appeared to be moderate, in the range of 0.5-0.6. AbstractOne hundred and forty-seven adult recipients of the Nucleus ® 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T-and C-levels appeared to be moderate, in the range of 0.5-0.6.
AutoNRT provides comparable accuracy to an average clinician but with the added benefit of significant time savings over manual recordings. This makes it a valuable tool for clinical measurement of ECAP threshold in cochlear implant recipients.
Neural response telemetry (NRT) data from 63 subjects equipped with the Nucleus CI24M Cochlear Implant System generally exhibited little change over up to 4 years. Larger changes, when they occurred, were seen only within the first 15 months postoperatively, and these changes diminished over time. Intraoperative NRT data were generally stable enough to be used for assisting in the initial speech processor fitting sessions. It was not possible to predict changes in the subjective map threshold and comfortable loudness levels (T and C levels, respectively) based on observed changes in the NRT data. The long-term stability of the neural response amplitude and the neural response threshold, however, implies that NRT may be useful as a routine diagnostic tool to detect changes to the neural periphery over time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.