Objectives To assess the effects of botulinum toxin for
prevention of migraine in adults.
Design Systematic review and meta-analysis.
Data sources CENTRAL, MEDLINE, Embase and trial
Eligibility criteria We included randomised controlled
trials (RCTs) of botulinum toxin compared with placebo,
active treatment or clinically relevant different dose for
adults with chronic or episodic migraine, with or without
the additional diagnosis of medication overuse headache.
Data extraction and synthesis Cochrane methods were
used to review double-blind RCTs. Twelve week posttreatment
time-point data was analysed.
Results Twenty-eight trials (n=4190) were included. Trial
quality was mixed. Botulinum toxin treatment resulted in
reduced frequency of −2.0 migraine days/month (95% CI
−2.8 to −1.1, n=1384) in chronic migraineurs compared
with placebo. An improvement was seen in migraine
severity, measured on a numerical rating scale 0 to 10
with 10 being maximal pain, of −2.70 cm (95% CI −3.31
to −2.09, n=75) and −4.9 cm (95% CI −6.56 to −3.24,
n=32) for chronic and episodic migraine respectively.
Botulinum toxin had a relative risk of treatment related
adverse events twice that of placebo, but a reduced risk
compared with active comparators (relative risk 0.76, 95%
CI 0.59 to 0.98) and a low withdrawal rate (3%). Although
individual trials reported non-inferiority to oral treatments,
insufficient data were available for meta-analysis of
Conclusions In chronic migraine, botulinum toxin reduces
migraine frequency by 2 days/month and has a favourable
safety profile. Inclusion of medication overuse headache
does not preclude its effectiveness. Evidence to support or
refute efficacy in episodic migraine was not identified.