Analysis of Facial Nerve Motor Evoked Potentials for Assessing a Central Mechanism in Hemifacial Spasm

Objective: To investigate whether the excitability of the facial nucleus group is enhanced in patients with hemifacial spasm, thereby further exploring the mechanism of hemifacial spasm.Methods: Microvascular decompression was employed to treat hemifacial spasm in 30 patients, and motor evoked potentials of the affected and healthy sides were monitored.The amplitude and threshold voltage of bilateral facial nerve motor evoked potential were compared using monopulse and multi-pulse stimulations.The inhibitory effect of sevoflurane on facial nerve motor evoked potential was monitored and analyzed statistically.Results: Stable facial motor evoked potential could be elicited by monopulse in 26 patients on the affected side, while only 5 patients on the healthy side, demonstrating a statistically significant difference between the two groups.The average threshold voltage of neuromotor evoked potential on the affected and healthy sides was 140.3 26.8 V and 177.0 23.2 V, respectively, with significant differences between the two groups.There was no statistical difference in the amplitude of facial motor evoked potential between the two groups.Sevoflurane exhibited a significant inhibitory effect on facial nerve motor evoked potential. Conclusion:The excitability of the facial nucleus mass was increased in patients with hemifacial spasm.