Delayed effects of the microvascular decompression on hemifacial spasm: a retrospective study of 131 consecutive operated cases.

We reviewed 131 consecutive cases operated for hemifacial spasm (HFS) by the same surgeon between January 1983 and April 1999. Microvascular decompression (MVD) was performed via lateral suboccipital approach. Post-operative follow-up ranged from 1.5 to 10 years (average 34 months). The final outcome divided into three categories, excellent (total recovery) in 120 cases (91.6%), partial (> 75% recovery) in 4 cases (3.1%), and unchanged or recurrent in 7 cases (5.3%). Only 2 cases were re-operated, and final outcome of both was excellent. Based on these data, we aimed to determine a period of the final judgement of MVD effect and the causative factors of delayed effects on HFS retrospectively. There were 102 complete recovered cases without hemifacial paralysis; immediate recovery from HFS was observed in 78 cases (76.5%), after 1 month in nine cases, 1-3 months in 5 cases, 3-6 months in 3 cases, 6-10 months in 2 cases, and 10-12 months in 5 cases. Thus, most cases were completely recovered within one year of observation. On the other hand, there was no statistically significant difference between immediate and delayed relief cases in clinical histories or operative observations. Therefore, our results suggest that the final judgement of the MVD effect could be made at least one year after surgery.