Delayed resolution of residual hemifacial spasm after microvascular decompression operations

OBJECTIVE: After microvascular decompression to treat hemifacial spasm (HFS), resolution of the HFS is often gradual. We carefully investigated the course of the gradual resolution of HFS and examined the differences between patients with and without postoperative HFS. METHODS: One hundred seventy-five patients with HFS were monitored, for observation of 1) whether postoperative HFS occurred, 2) when it occurred, and 3) when it disappeared after microvascular decompression. For two groups of patients, with (Group I) and without (Group II) postoperative HFS, we investigated age, sex, spasm side, preoperative facial nerve block (botulinum toxin treatment), decompression material, preoperative HFS period, offender (compressing vessel), temporary and permanent postoperative complications, and electromyographic findings. RESULTS: In Group I (88 patients), postoperative HFS began within 4 days after surgery, a period that we have termed the silent period of postoperative HFS; the median value for the time to resolution was 28 days. The other 87 patients exhibited no postoperative HFS (Group II). There was a significantly higher incidence of postoperative facial weakness in Group II (Group II, 41.3%; Group I, 25.5%; P=0.02 by logistic regression analysis). In Group I, there was no statistically significant relationship between the investigated parameters and the silent period or the postoperative HFS period, as determined by Cox proportional-hazards regression analysis, except for the number of preoperative facial nerve blocks. Electromyographic investigation of F waves revealed facial paresis during the silent period in a patient. CONCLUSION: Approximately 50% of patients with HFS exhibited residual spasm postoperatively. An immediate postoperative silent period of 4 days without spasm was characteristic. One-quarter, one-half, and 90% of the residual spasm resolved by 1 week, 1 month, and 8 months after surgery, respectively.