Amplitude Growth Functions of Auditory Nerve Responses to Electric Pulse Stimulation With Varied Interphase Gaps in Cochlear Implant Users With Ipsilateral Residual Hearing.
Marina Imsiecke, Andreas Büchner, Thomas Lenarz and 1 others
PMID 34181493WHAT IT FOUND
Changing the gap between electrical pulses altered auditory nerve responses.
Some changes related to hearing loss duration, but they did not predict speech perception.
Key findings
01In EAS users, the change in level 50% differed significantly between Electrode 1 and Electrodes 3 and 4 after Bonferroni correction.
02When EAS and CI users were combined, the change in level 50% between the 2.1 and 10 microsecond interphase gaps was significantly related to duration of hearing loss.
03No change in eCAP characteristics due to interphase gap significantly correlated with speech reception performance in EAS or CI users.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The EAS and CI groups were not fully matched: mean age differed by 3 years and mean duration of hearing loss differed by 14 years. Only about 70% of measured amplitude growth functions produced a reliable fit, so many electrode-level comparisons were missing. Signal blanking could underestimate eCAP amplitude, making absolute amplitudes unreliable. Some subjects reached their loudest acceptable level before saturation, preventing reliable curve fitting. EAS users often scored near ceiling on the HSM sentence test, limiting detection of speech-performance relationships. Participants had different causes and progression of hearing loss, adding variability.
Declared interests
Authors declared no potential conflicts of interest. Funding came from the Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy and a DFG project, and from MED-EL Medical Electronics.
The easy way to misread this
Do not conclude that eCAP amplitude-growth measures can be used to estimate neural health for clinical decisions or to predict speech perception. The study did not test patient outcomes from programming changes, and no eCAP change significantly correlated with speech reception performance.