Electrocochleography Latency: Correlation With Electrode Position During Cochlear Implantation.
Raphael R Andonie, Wilhelm Wimmer, Reto A Wildhaber and 3 others
PMID 40001274WHAT IT FOUND
Cochlear microphonic latency reliably tracks electrode depth during implantation, rising as the array moves toward the apex.
However, it does not correlate with a patient's residual hearing. This makes latency a useful positional marker, but not a direct indicator of preserved hearing sensitivity.
Key findings
01Cochlear microphonic latency significantly increases with linear insertion depth for stimulation frequencies of 0.5, 0.75, and 1 kHz, both during and after insertion.
02There was no significant correlation between cochlear microphonic latency and residual hearing, regardless of whether latency elevation or increase was measured.
03Latency at 0.25 kHz did not correlate with insertion depth, likely because the signal generators for this low frequency are located beyond the apical reach of the electrodes.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample size was small (30 ears), which limits the generalizability of the null findings regarding residual hearing. Most patients had limited residual hearing (mean pure-tone average of 81 dBHL), meaning the study may not have had enough sensitivity to detect a correlation in patients with better preserved hearing. Manual insertion of the electrode array introduced variability in insertion times, which distorted the precise timing of latency measurements during the insertion phase compared to the post-insertion phase. The 0.25 kHz data was unusable for depth tracking because the electrodes did not reach the apical regions responsible for generating those signals.
Declared interests
The study used equipment and software from Cochlear Ltd. (CI622 implant, Nucleus 6 processor, Research Platform software). The text does not explicitly state whether Cochlear Ltd. funded the study or if the authors have financial conflicts, but the reliance on proprietary hardware and software is noted.
The easy way to misread this
Do not interpret cochlear microphonic latency as a measure of residual hearing. While latency reliably indicates electrode depth, this study found no correlation between latency and hearing thresholds, meaning a long or short latency does not tell you how much natural hearing the patient has preserved.
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