Intraoperative monitoring of lateral spread response in micro-vascular decompression of primary hemifacial spasm: a report of 28 cases and literature review

Objective To explore the value of intraoperative monitoring of lateral spread response (LSR) in microvascular decompression of primary hemifacial spasm.Methods Twenty-eighty patients with primary hemifacial spasm,admitted to our hospital from January 2010 to May 2011,were chosen in our study; they were performed microvascular decompression and U.S EpochXP neurophysiologcal monitoring equipment was used to continuously stimulate the zygomatic branch of facial nerve; the electromyographic response of the orbicularis muscle and mentalis muscle were recorded; the characteristics of abnormal muscle response (AMR) changes of the mentalis muscle were observed.Follow up was performed on these patients.Results The cure rate was 89.29％,the efficient was 100％,and no recurrence was noted 24 months after follow-up.The abnormal muscle responses of the mentalis muscle disappeared after microvascular decompression of 22 patients; with 12 months of follow up,21 patients were completely free from hemifacial spasm and 1 partly cured.The changes of AMR amplitude and the clinical results at 24 months after follow-up were significantly correlated (kr=0.627,P=0.023).Conclusions The continuous monitoring of lateral spread response is real-time objective for determining the decompression effect and prognosis.The AMR amplitude not bring completely disappeared can also prognosis good results. Key words: Hemifacial spasm;  Intraoperative monitoring;  Lateral spread response; Abnormal muscle response;  Microvascular decompression