[Abnormal muscle response monitoring as a guide during microvascular decompression for hemifacial spasm]

To investigate the value of abnormal muscle response (AMR) monitoring during microvascular decompression (MVD) for hemifacial spasm (HFS) and compare the outcomes of the patients undergoing AMR or not.

234 HFS patients, aged (45.2 +/- 12.5) (25 - 76), undergoing MVD were randomly divided into 2 groups:199 of them underwent AMR monitoring intra-operatively and 35 not. No muscle relaxant was used. The zygomatic branch of the facial nerve was stimulated electrically and the AMR of the ipsilateral mental muscle was recorded. The relationship between AMR monitoring results and final surgical outcome was analyzed.

Before incision of dura mater, all patients showed characteristic AMR of HFS. AMR disappeared in 165 patients (82.9%) after MVD of the facial nerve root. HFS disappeared shortly after operation in 144 of the 165 patients with disappearance of AMR, and only in 8 of the 34 patients with persistent AMR. Follow-up lasting for more than 1 year showed that HFS disappeared in 157 of the 181 patients of the AMR group, and in 24 of the 35 patients who had not undergone AMR monitoring during operation.

Helping differentiate the responsible vessel, to assess the effect of decompression, and to predict the postoperative course of MVD, AMR monitoring improves the long-term outcome of HFS treated with MVD.