Application of multibranch abnormal muscle response monitoring during microvascular decompression for hemifacial spasm

Abstract

Objective Abnormal muscle response (AMR) is widely used as an indicator of the degree and effect of surgery during microvascular decompression (MVD) for hemifacial spasm (HFS). However, the positive rate of AMR during operation is quite different because of individual differences and single recording of muscle, which can not predict surgical outcomes. We present an improved method to record from multiple muscles innervated by multiple branches of the facial nerve to enlarge the AMR positive rate. Methods A total of 96 HFS patients in our hospital from January 2017 to June 2019, underwent MVD with intraoperative AMR monitoring. Ipsilateral frontalis, orbicularis oculi, orbicularis oris and mentalis were simultaneously monitored for AMR in stimulating the affected zygomatic branch of facial nerve in all cases. The effect of MVD for facial nerve was analyzed based on the disappearance of intraoperative AMR and the postoperative result. Results The AMR positive rate of frontalis was 43.75% (42/96), of orbicularis oculi was 38.54% (37/96), of orbicularis oris was 64.58% (62/96) and of mentalis was 78.13% (75/96). Total AMR positive rate was further improved to 97.92% (94/96) when the 4 muscles were monitored simultaneously. The AMR positive rates between multiple muscles monitoring group and any single muscle monitoring groups were significantly different (P = 0.000, for all). The AMR positive rates of orbicularis oris and mentalis were higher than that of frontalis (P = 0.000, 0.006) and orbicularis oculi (P = 0.000, 0.000). The postoperative results were statistically different between AMR complete disappearance group and AMR persistence group (Fisher exact probability: P = 0.043). Conclusions The method of multibranch facial muscles monitoring can effectively increase the AMR positive rate. AMR disappearance after the operation can evaluate the effect of facial nerve decompression and judge the prognosis.

DOI:10.3969/j.issn.1672⁃6731.2020.11.010