Botulinum toxin type A therapy for hemifacial spasm

Background: This is an update of a Cochrane Review, first published in 2005. Hemifacial spasm (HFS) is characterised by unilateral, involuntary contractions of the muscles innervated by the facial nerve. It is a chronic disorder, and spontaneous recovery is very rare. The two treatments routinely available are microvascular decompression and intramuscular injections with botulinum toxin type A (BtA).

Objectives: To compare the efficacy, safety, and tolerability of BtA versus placebo in people with HFS.

Search methods: We searched CENTRAL, MEDLINE, Embase, reference lists of articles, and conference proceedings in July 2020. We ran the electronic database search, with no language restrictions, in July 2020.

Selection criteria: Double-blind, parallel, randomised, placebo-controlled trials (RCTs) of BtA versus placebo in adults with HFS.

Data collection and analysis: Two review authors independently assessed records. We planned to select included studies, extract data using a paper pro forma, and evaluate the risk of bias. We resolved disagreements by consensus, or by consulting a third review author. We planned to perform meta-analyses. The primary efficacy outcome was HFS-specific improvement. The primary safety outcome was the proportion of participants with any adverse event.

Main results: We found no parallel-group randomised controlled trials comparing BtA and placebo in HFS.

Authors' conclusions: We did not find any randomised trials that evaluated the efficacy and safety of botulinum toxin type A in people with hemifacial spasm, so we are unable to draw any conclusions. Observational data show a strong association between BtA treatment and symptom improvement, and a favourable safety profile. While it is unlikely that future placebo-controlled RCTs will evaluate absolute efficacy and safety, they should address relevant questions for both people with HFS (such as long-term effects, quality of life, and other patient-reported outcomes), and clinicians (such as relative effectiveness of different BtA formulations and schemes of treatment) to better guide clinical practice.).