Real Time Monitoring During Cochlear Implantation: Increasing the Accuracy of Predicting Residual Hearing Outcomes.

OBJECTIVES: Real-time electrocochleography (rt-ECochG) is a method to detect intracochlear potential changes during cochlear implantation (CI). Steep amplitude drops of the cochlear microphonic (CM) signal (so called "ECochG events") have been correlated with worse residual hearing outcomes. However, the sensitivity and specificity of monitoring CM amplitude on its own are too low to use it as a biomarker. The aim of this article was to establish if additional signal components would help to better predict postoperative hearing outcomes.

DESIGN AND SETTING: Single-center, prospective cohort study at a tertiary referral hospital.

PARTICIPANTS AND INTERVENTIONS: Between 2017 and 2020, we included 73 adult patients receiving a lateral wall cochlear implant electrode. During electrode insertion, rt-ECochG measurements were performed.

MAIN OUTCOMES: We calculated a multiple regression analysis for patients with one ECochG event. The dependant variable was the relative acoustic hearing result 4 weeks after surgery. Independent variables were CM latency, a ratio of the auditory nerve neurophonic to the CM (the ANN/CM index) as well as CM signal recovery.

RESULTS: The change of the ANN/CM index linearly correlated with acoustic hearing outcomes 4 weeks after surgery. Adding this factor led to a statistically significant increase in the variance accounted for by the regression model.

CONCLUSIONS: When monitoring the implantation process with rt-ECochG, prediction of postoperative hearing thresholds is improved by addition of the ANN/CM index to a model that includes CM amplitude fluctuation.