Identifying Slim Modiolar Electrode Tip Fold-Over With Intracochlear Electrocochleography

Tuesday, October 3, 2023

4:45 PM - 4:51 PM East Coast USA Time

Location: 104BC

Presenting Author(s)

Jordan J. Varghese, MD

Resident Physician-Scientist Trainee
Washington University/BJH/SLCH Consortium
Saint Louis, MO, United States

Co-Author(s)

AW

Amit Walia, MD

Resident Physician / T32 Postdoctoral Scholar
Washington University in St. Louis
St. Louis, MO, United States
Matthew A. Shew, MD

Assistant Professor
Washington University in St. Louis
St. Louis, MO, United States
ND

Nedim Durakovic, MD

Assistant Professor
Washington University/B-JH/SLCH Consortium
Saint Louis, MO, United States
Cameron C. Wick, MD

Associate Professor
Washington University
Saint Louis, MO, United States
JH

Jacques A. Herzog, MD

Professor
Washington University in St. Louis, USA

Senior Author(s)

Craig A. Buchman, MD

Lindburg Professor and Chair, Dept of Otolaryngology-Head & Neck Surgery
Washington University School of Medicine
Saint Louis, MO, United States

Disclosure(s):

Jordan J. Varghese, MD: No relevant relationships to disclose.

Introduction: Cochlear implants (CI) with slim modiolar electrode arrays were designed to minimize insertion trauma and provide more specific tonotopic selectivity; however, tip fold-over remains a common complication. Intracochlear electrocochleography (ECochG), an acoustically evoked electric potential generated from the cochlea and recorded off the CI electrode array, could identify tip fold-over in real-time.

Methods: 57 patients, including both adults and children, prospectively underwent ECochG monitored cochlear implantation with a slim modiolar electrode from July 2022 to January 2023 at a tertiary academic center. ECochG was recorded from the electrode array both during and after insertion with tone-burst acoustic stimuli presented via a sound delivery tube at ~100 dB nHL. Multifrequency insertion monitoring at 250 Hz and 500 Hz was recorded from the most apical electrode. Post-insertion electrode sweeps were recorded from various electrodes across the array at several frequencies from 250 Hz to 4 KHz. Intraoperative plain radiographs confirmed post-insertion electrode position.

Results: There were 10 tip fold-over events. Tip fold-over insertions showed lower than anticipated rise in amplitude for 250 Hz, and lack of early characteristic frequency peak for 500 Hz. Tip fold-over electrode sweeps did not have the typical tonotopic progression expected as frequency was increased. Atypical ECochG patterns could be seen with well inserted electrode arrays (38.5%); however, there was no tip fold-over events identified when ECochG patterns were robust and tonotopic (26.3%). Subthreshold ECochG responses did not provide ample response for pattern recognition and were seen with minimal baseline hearing candidates (22.8%).

Conclusions: Initial findings suggest that intracochlear ECochG during CI insertion can identify properly positioned slim modiolar electrodes independent of imaging when the ECochG responses show a robust and tonotopic pattern. When the ECochG pattern is atypical, concern should be raised for possible tip fold-over and intraoperative imaging is needed to confirm electrode position.