2-P-F-16. Multimodality monitoring during microvascular decompression for hemifacial spasm

Abstract

Objective The present study investigated whether free-running electromyography (frEMG) monitoring correlated with abnormal muscle responses (AMRs), or facial motor evoked potentials (FMEP) in 26 hemifacial spasm patients who underwent microvascular decompression (MVD). Methods frEMGs were recorded after injection of 20 ml of saline onto the root exit zone of the facial nerve. Using a software tool, data were rectified and measured for frEMG activity from the orbicularis oculi or mentalis (ME) muscle as an integral value 10 s after injection. frEMG activity was measured before and after MVD. With regard to AMRs, patients were divided into two groups based on disappearance or persistence of AMRs after MVD. Ratios of final to baseline FMEP amplitudes were used for analysis. Results Thirteen patients with decreased frEMG activity after surgery had significantly smaller FMEP amplitude ratios in the ME muscles compared with 13 patients without decreased activity (65% vs. 94%, p Conclusions/significance Decreases in frEMG activity elicited by a saline injection after MVD night reflect normalization of facial nerve excitability.