Monitoring Cochlear Health With Intracochlear Electrocochleography During Cochlear Implantation: Findings From an...

Area of Science:

• Otoacoustic emissions and electrophysiology
• Neurosurgery and audiology
• Medical device monitoring

Background:

• Electrocochleography (ECochG) is an emerging tool for monitoring cochlear function during cochlear implant (CI) surgery.
• Intraoperative ECochG can be recorded from electrodes on the implant array.
• ECochG amplitude changes during electrode insertion may reflect cochlear status.

Purpose of the Study:

• To determine if a drop in ECochG amplitude (compromise) during CI electrode insertion correlates with poorer postoperative acoustic hearing.
• To investigate the influence of preoperative hearing levels on the ability to record ECochG signals.
• To test hypotheses linking CM amplitude compromise to hearing deterioration at different postoperative intervals and preoperative hearing levels to CM recording feasibility.

Main Methods:

• Prospective, multi-site, observational study with 77 adult CI candidates.
• ECochG recorded during and after electrode array implantation.
• Preoperative and postoperative pure-tone audiometry at 4-6 weeks (FUV1) and 3 months (FUV2).

Main Results:

• CM compromise during insertion was associated with significantly poorer hearing preservation at FUV1 (median hearing loss 26.9 dB vs. 12.6 dB, p < 0.014).
• A measurable CM (>1 µV) during implantation depended on preoperative low-frequency hearing thresholds (≤80 dB HL).
• High-frequency preoperative thresholds also correlated with the presence of a measurable CM.

Conclusions:

• Intraoperative CM amplitude drops during CI electrode insertion are linked to worse postoperative hearing preservation.
• Preoperative low-frequency hearing levels below 80 dB HL are important for obtaining reliable intraoperative CM signals.
• ECochG is a practical tool for monitoring cochlear function during CI surgery, with implications for surgical technique and patient outcomes.