Value of abnormal muscle response intraoperative monitoring guiding microvascular decompression surgery for hemifacial spasm

Objective To explore the value of the intraoperative waveform and amplitude changes of abnormal muscle response(AMR) on guiding microvascular decompression(MVD)for hemifacial spasm.

Methods From January 2018 to December 2019, in Department of Neurosurgery, Zhongshan Hospital, Fudan University, 165 cases of patients on whom intraoperative AMR monitoring were performed during MVD were analyzed retrospectively.

Results During decompression, there were 144 cases(97.3%) with intraoprative waveform or amplitude changes of AMR. The disappearance rate of AMR in patients with waveform or amplitude changes was significantly higher than that without waveform or amplitude changes(P=0.011, P=0.001). AMR disappeared in 146 cases, postoperative remission in 135 cases (92.5%). While AMR did not disappear in 19 cases, postoperative remission in 11 cases (57.9%). There was significant difference in postoperation relief between the AMR disappearance group and the AMR existence group(P=9×10^-6).

Conclusion The waveform and amplitude changes during the decompression suggest that the area is close to the responsible vessels, the AMR is more likely to disappear after the decompression indicating a better prognosis.