Abstract
PurposeThe aim of this study was to analyze the utility of various preoperative electrophysiological tests of the facial nerve CNVII in predicting CNVII function after vestibular schwannoma surgery.MethodsThis retrospective study included 176 patients who had preoperative facial nerve 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).ResultsAD-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 muscles 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 to the healthy side) was an independent factor associated with increased risk of facial muscles weakness (p = 0.015 and p = 0.031 for early and late outcomes, respectively).ConclusionsFurther studies are needed to establish which tests and cut-off values are the most useful for predicting post-surgical facial nerve function.
Highlights
Intraoperative electrophysiological monitoring of the facial nerve (CNVII) in vestibular schwannoma surgery (VS) is critical for preserving its function [1]
AD-CNVII, D-CNV, D-BR, and A-EMG were noted in 24%, 10%, 64%, and 71% of the patients, respectively
AD-CNVII was an independent factor associated with increased risk of facial muscles weakness (p = 0.015 and p = 0.031 for early and late outcomes, respectively)
Summary
Intraoperative electrophysiological monitoring of the facial nerve (CNVII) in vestibular schwannoma surgery (VS) is critical for preserving its function [1]. Intraoperative stimulation thresholds obtained during surgery but after tumor removal have predictive value for postoperative CNVII function [2, 3]. Outcome prediction using test results obtained prior to surgery is not yet possible, and the relevance of preoperative neurophysiological evaluation of CNVII function is not clear. Extending the electrophysiological evaluation by using the blink reflex, facial muscle response potentials evoked by transcranial magnetic stimulation, or needle electromyography of the facial muscles could reveal the real extent of facial nerve and brain stem damage at the site of tumor compression
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