Utility of Preoperative Electrophysiological Testing of the Facial Nerve in Patients with Vestibular Schwannoma

Objective: The aim of this study was to analyze the utility of various preoperative electrophysiological tests in predicting CNVII function after vestibular schwannoma (VS) surgery. Study Design: Retrospective analysis. Material and Methods: This study included 176 patients with VS who had preoperative CNVII electroneurography and electrically evoked blink reflex testing. We defined the following variables: axonal degeneration of CNVII (AD-CNVII), trigeminal nerve damage (D-CNV), disturbances in the short-latency pathway of the blink reflex (D-BR), and any changes in electrophysiological test results (A-EMG). Results: AD-CNVII, D-CNV, D-BR, and A-EMG were noted in 24, 10, 64, and 71% of the patients, respectively. Negative D-CNV correlated with good CNVII function in early (p = 0.005) and long-term follow-up (p = 0.003) but was not an independent prognostic factor for postoperative facial function. D-CNV appeared to be closely related to tumor size. D-BR was related to tumor size and had no predictive value. AD-CNVII (amplitude reduction of 50% or more compared with the healthy side) was an independent factor associated with increased risk of facial weakness (p = 0.015 and p = 0.031 for early and late outcomes, respectively). Conclusions: Preoperative electrophysiological testing in patients with VS has prognostic value. Significant axonal damage of CNVII in the preoperative period is an independent factor that increases the risk of facial weakness after surgery.