O3-6-21. Time-dependent changes in intraoperative monitoring findings during microvascular decompression for hemifacial spasm

Abstract

We analyzed time-dependent changes in the intraoperative monitoring of abnormal muscle responses (AMRs) and facial motor evoked potentials (FMEPs) elicited by transcranial electrical stimulation during microvascular decompression (MVD) in 26 patients with hemifacial spasm. In the orbicularis oculi muscle, the AMRs disappeared in 11 patients before MVD, in six after MVD, and in three during dural closure. The AMRs persisted in six patients. FMEP amplitudes decreased to less than 50% in two patients before MVD, in four after MVD, and in six during dural closure. FMEP amplitudes did not decrease in 14 patients ( p p