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Performing Intracochlear Electrocochleography During Cochlear Implantation
Published on: March 8, 2022
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Improving Real-Time Feedback During Cochlear Implantation: The Auditory Nerve Neurophonic/Cochlear Microphonic Ratio
Christofer Bester1,2, Stephen John O'Leary3,4, Frédéric Venail5
1Ear Science Institute Australia, Perth, Australia.
Ear and Hearing
|January 10, 2025
Summary
Monitoring the auditory nerve neurophonic (ANN)/cochlear microphonic (CM) ratio during cochlear implantation helps predict hearing loss. An increasing ANN/CM ratio indicates preserved hearing, while a decreasing ratio suggests significant hearing loss.
Area of Science:
- Otoacoustic emissions
- Auditory neurophysiology
- Cochlear implant technology
Background:
- Cochlear implantation requires monitoring cochlear function to prevent hearing loss.
- Cochlear microphonic (CM) monitoring can indicate hearing trauma, but is prone to false positives.
- Auditory nerve neurophonic (ANN) monitoring may offer a more reliable indicator of cochlear function during implantation.
Purpose of the Study:
- To test the hypothesis that the ANN/CM ratio increases during cochlear microphonic drops not associated with postoperative hearing loss.
- To evaluate the utility of the ANN/CM ratio in differentiating true cochlear trauma from artifactual CM changes.
- To assess the predictive value of the ANN/CM ratio for hearing preservation after cochlear implantation.
Main Methods:
- Analyzed electrocochleography data from 28 adult cochlear implant recipients with pre-existing CM drops.
- Measured cochlear microphonic (CM) and auditory nerve neurophonic (ANN) responses during and immediately after electrode insertion.
- Calculated the ANN/CM ratio and correlated changes with postoperative pure-tone audiometry results at 4-6 weeks.
Main Results:
- An increasing ANN/CM ratio during a CM drop was observed in 19 participants, while 9 showed a decrease.
- Participants with a decreasing ANN/CM ratio experienced significantly worse median hearing loss (29.0 dB) compared to those with an increasing ratio (13.3 dB).
- The ANN/CM ratio demonstrated better predictive accuracy for hearing preservation than ANN amplitude alone.
Conclusions:
- The ANN/CM ratio effectively distinguishes between cochlear microphonic drops that result in hearing loss and those that do not.
- This ratio is readily measurable and responds quickly during intraoperative monitoring.
- The ANN/CM ratio shows promise for enhancing current and future intraoperative monitoring strategies in cochlear implantation.
