Effects of Stimulus Polarity and Artifact Reduction Method on the Electrically Evoked Compound Action Potential.
Michelle L Hughes, Jenny L Goehring, Jacquelyn L Baudhuin
PMID 28045836WHAT IT FOUND
Cochlear implant nerve response measurements changed with the artifact-reduction method.
The anodic forward-masking method gave fastest timing and largest response size, while alternating polarity gave higher thresholds. Advanced Bionics ears showed no size, slope or threshold differences.
Key findings
01For Cochlear ears, mean ECAP amplitude at the highest common probe level was 340.6 µV for anodic forward masking, 249.7 µV for cathodic forward masking and 235.1 µV for alternating polarity.
02For Cochlear ears, anodic forward masking produced the shortest latencies and alternating polarity produced the highest thresholds.
03For Advanced Bionics ears, latency differed across methods, but amplitude, slope and threshold did not differ significantly.
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How it was doneWhat they found
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What it does not show
Only 18 CI recipients (23 ears) were tested, and the number analysed varied by device and outcome, so the findings are narrow. Some Cochlear participants overlapped with an earlier study, so the findings are not entirely independent data. Cochlear and Advanced Bionics devices used different pulse durations, interphase gaps, probe rates, array types and software defaults, so results cannot be pooled or compared directly across manufacturers. The study measured ECAP waveform properties, not hearing, speech, language or therapy outcomes. One Cochlear subject was excluded from amplitude and slope analyses because the alternating-polarity growth function had only two data points. The authors state that mechanisms underlying differences between AltPol and FM require further investigation.
Declared interests
No other conflicts of interest were reported.
The easy way to misread this
Do not read the Cochlear waveform differences as evidence that one artifact-reduction method improves patient hearing. The outcomes were ECAP amplitudes, latencies, slopes and thresholds, not clinical hearing or therapy results. Advanced Bionics ears showed no significant amplitude, slope or threshold differences among methods.