Botulinum toxin type A therapy for hemifacial spasm

Abstract

BACKGROUND Hemifacial spasm is characterised by unilateral involuntary contractions of muscles innervated by the facial nerve. The usual cause is a vessel touching the facial nerve near its origin from the brain stem. Although it is a benign condition it can cause significant cosmetic and functional disability. It is a chronic disease and spontaneous recovery is very rare. The two treatments routinely available are microvascular decompression and Botulinum Toxin type A (BtA) muscular injections. OBJECTIVES To determine whether botulinum toxin (BtA) is an effective and safe treatment for hemifacial spasm. SEARCH STRATEGY We searched the Cochrane Movement Disorders Group trials register, the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2004), MEDLINE (1977 to December 2003), EMBASE (1977 to December 2003), and reference lists of articles. We also contacted drug manufacturers and researchers in the field. SELECTION CRITERIA Randomised studies comparing BtA with placebo in people with hemifacial spasm. DATA COLLECTION AND ANALYSIS Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information. Adverse effects information was collected from the trials. MAIN RESULTS We found 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 - formulation Botox(r) (low dose: one-half of the intermediate dose; intermediate dose; and high dose: twice the intermediate dose), and one of placebo. In this trial BtA was superior to placebo. AUTHORS' CONCLUSIONS The findings of this single eligible 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. Despite the paucity of good quality controlled data, all the studies available suggest that BtA is effective and safe for treating hemifacial spasm. Future trials should explore technical factors such as the optimum treatment intervals, different injection techniques, doses, Bt types and formulations. Other issues include service delivery, quality of life, long-term efficacy, safety, and immunogenicity. BtA should be compared with surgical microvascular decompression.