Clinical study of early disappearance of abnormal muscle response during microvascular decompression for hemifacial spasm

Abstract

Objective To explore the influencing factors of early disappearance of abnormal muscle response (AMR) during microvascular decompression for hemifacial spasm(HFS) and the clinical outcomes. Methods During the period from January to December of 2014, a total of 372 patients of HFS underwent microvascular decompression (MVD) at Neurosurgery Department of Nanjing Drum Tower Hospital. Characteristic AMR of HFS was observed in 359 patients intraoperatively, among whom 33 patients showed early permanent disappearance of AMR before decompression and the remaining 326 patients did not. Clinical features and outcomes of 359 cases were analyzed retrospectively. Results Offending vessels were identified in all 359 cases. In the 33 patients with early disappearance of AMR, no indentation was observed on their facial nerves, and immediate and delayed (7 days post operation) resolution of symptoms occurred in 32 cases and 1 case, respectively. No complications were reported during the follow-up period in the 33 patients. In the 326 patients without early disappearance of AMR, 39 (12%) cases demonstrated indentation on the facial nerve.In this group, AMR disappeared completely in 305(93.6%) patients after decompression. Although sufficient decompression was achieved, AMR did not disappear in the other 21 (6.4%) patients. Out of the 326 patients, immediate and delayed (2-310 days post operation) symptom resolution occurred in 267 and 57 cases, respectively, and HFS was not relieved in the remaining 2 cases. Hearing loss and delayed facial paralysis were observed in 4 and 9 cases, respectively.The two groups of patients were followed-up for 20-32 months, and no recurrence was observed. The surgical outcomes in patients with early AMR disappearance were significantly better than the other group(P=0.027). The two groups did not differ for postoperative complications. There were no statistically significant differences in gender, age, duration of illness, the side of HFS or the type of offending vessels between the two groups(P>0.05). Conclusions Less stress of offending vessels might be responsible for early disappearance of AMR. Compared with those without early AMR disappearance, the patients whose AMR disappear before decompression seem to have better outcomes. Key words: Hemifacial spasm; Microvascular decompression; Prognosis; Abnormal muscle response; Influencing factors