Intraoperative facial electromyography and brainstem auditory evoked potential findings in microvascular decompression for hemifacial spasm: correlation with postoperative delayed facial palsy

Abstract

Background: Delayed facial palsy (DFP) after microvascular decompression (MVD) in patients with hemifacial spasm (HFS) is not uncommon, but the cause remains unknown.

Objectives: To assess whether intraoperative electromyography (EMG) and brainstem auditory evoked potential (BAEP) can predict DFP after MVD.

Methods: Between September 2009 and February 2011 we examined 86 patients, 9 of whom (10.4%) developed DFP after MVD on the same side. All patients underwent MVD and were followed-up for a median period of 13 months (range 6-22). We retrospectively examined intraoperative facial EMG and BAEP findings using our MVD patients' registry. We excluded secondary HFS and immediate postoperative facial palsy after MVD in this study. We assessed the prevalence and clinical characteristics of DFP and compared EMG and BAEP findings between DFP and non-DFP groups.

Results: All patients recovered completely, with a mean time to recovery of 37.8 days (range 22-57). There were no significant differences between DFP and non-DFP patients in terms of the amplitude and latency of intraoperative EMG and BAEP.

Conclusion: The usefulness of intraoperative facial EMG and BAEP is limited and cannot predict DFP after MVD for HFS. We speculate that DFP after MVD is not associated with permanent nerve damage according to the EMG findings.