Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
[22] Systematic review	3097 adults with headache	Blepharoptosis 136/1797 (8%) with botulinum toxin A 13/1300 (1%) with placebo	RR 9.5 95% CI 4.7 to 18.9	Large effect size	placebo
[22] Systematic review	2783 adults with headache	Muscle weakness 358/1706 (21%) with botulinum toxin A 25/1077 (2%) with placebo	RR 8.9 95% CI 2.5 to 30.9 Heterogeneity: I2 = 85.8% (P value not reported)	Large effect size	placebo
[22] Systematic review	2033 adults with headache	Neck pain 230/1205 (19%) with botulinum toxin A 30/828 (4%) with placebo	RR 4.7 95% CI 3.2 to 6.9	Moderate effect size	placebo
[22] Systematic review	767 adults with headache	Neck stiffness 56/395 (14%) with botulinum toxin A 16/372 (4%) with placebo	RR 3.2 95% CI 1.9 to 5.6	Moderate effect size	placebo
[22] Systematic review	3110 adults with headache	Paraesthesia 54/1794 (3%) with botulinum toxin A 18/1316 (1%) with placebo	RR 3.3 95% CI 1.3 to 7.9	Moderate effect size	placebo
[22] Systematic review	1088 adults with headache	Skin tightness 30/580 (5%) with botulinum toxin A 7/508 (1%) with placebo	RR 3.6 95% CI 1.6 to 8.3	Moderate effect size	placebo