Four-Point Impedance and Utricular Dysfunction Is Associated with Postoperative Dizziness after Cochlear Implantation

Abstract

Introduction Postimplantation dizziness is common, affecting approximately 50% of patients. Theories for dizziness include utricular inflammation, endolymphatic hydrops, and loss of perilymph. Four-point impedance (4PI) is a novel impedance measurement in cochlear implantation that shows potential to predict hearing loss, inflammation, and fibrotic tissue response. Here, we associate 4PI with dizziness after implantation and explore the link with utricular function. Methods Subjective visual vertical (SVV) as a measure of utricular function was recorded preoperatively as a baseline. 4PI was measured immediately postinsertion. Ongoing follow-up was performed at 1 day, 1 week, and 1 month, postoperatively. At each follow-up, 4PI, SVV, and the patients’ subjective experience of dizziness were assessed. Discussion Thirty-eight adults were recruited. One-day 4PI was significantly higher in patients dizzy within the next week (254 Ω vs 171 Ω, p = 0.015). The optimum threshold on receiver operating characteristic curve was 190 Ω, above which patients had 10 times greater odds of developing dizziness (Fisher exact test, OR = 9.95, p = 0.0092). This suggests that 4PI varies with changes in the intracochlear environment resulting in dizziness, such as inflammation or hydrops. SVV significantly deviated away from the operated ear at 1 day (fixed effect estimate = 2.6°, p ≤ 0.0001) and 1 week (fixed effect estimate 2.7°, p ≤ 0.001). Conclusion One-day 4PI is a potentially useful marker for detecting postoperative dizziness after cochlear implantation. Of the current theories for postoperative dizziness, inflammation might explain the findings seen here, as would changes in hydrostatic pressure. Future research should focus on detecting and exploring these labyrinthine changes in further detail.

Four-Point Impedance: A Potential Biomarker for Residual Hearing After Cochlear Implantation

“…Patient recruitment occurred between May 2021 and July 2022, and written informed consent was obtained for all participants. Some participants in this study were also enrolled in a recently published study investigating 4PI, vestibular function, and dizziness after cochlear implantation (17); however, hearing was not reported in that study, and thus, the data presented here are new.…”