A Cochrane review included only one small randomised, placebo-controlled trial involving 11 people. It was a crossover trial during which patients underwent four sets of injections, comparing placebo with three different doses of BtA. In this trial BtA was superior to placebo. The findings of this single trial support the results of large, open, case-control studies showing a benefit rate between 76 and 100%. This effect size probably makes it very difficult to perform new large placebo controlled trials for hemifacial spasm.
Comment: The quality of evidence is downgraded by imprecise results (only one RTC).