Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	421 adults with cervical dystonia 6 RCTs in this analysis	Proportion of people with any adverse effect (neck weakness, dysphagia, voice changes/hoarseness, dry mouth/sore throat) 131/226 (58%) with botulinum A toxin 89/195 (46%) with placebo	OR 2.10 95% CI 1.32 to 3.25 P = 0.002 NNH 6 95% CI 4 to 15	Small effect size	placebo
Systematic review	605 adults with cervical dystonia 10 RCTs in this analysis	Proportion of people with neck weakness 62/339 (18%) with botulinum A toxin 9/266 (3%) with placebo	OR 4.86 95% CI 2.55 to 9.25 P <0.00001 NNH 8 95% CI 7 to 10	Moderate effect size	placebo
Systematic review	210 adults with cervical dystonia 2 RCTs in this analysis	Proportion of people with voice changes/hoarseness 15/120 (13%) with botulinum A toxin 4/90 (4%) with placebo	OR 2.62 95% CI 0.98 to 7.01 P = 0.05		Not significant
Systematic review	401 adults with cervical dystonia 6 RCTs in this analysis	Proportion of people with dry mouth/sore throat 42/216 (19%) with botulinum A toxin 15/185 (8%) with placebo	OR 2.54 95% CI 1.42 to 4.55 P = 0.002 NNH 10 95% CI 7 to 21	Moderate effect size	placebo
RCT 3-armed trial	233 adults with cervical dystonia	Proportion of people with dysphagia 8/78 (10%) with incobotulinumtoxinA (120 U) 13/81 (16%) with incobotulinumtoxinA (240 U) 2/74 (3%) with placebo	Significance not assessed
RCT 3-armed trial	233 adults with cervical dystonia	Proportion of people with neck pain 4/78 (5%) with incobotulinumtoxinA (120 U) 10/81 (12%) with incobotulinumtoxinA (240 U) 1/74 (1%) with placebo	Significance not assessed
RCT 3-armed trial	233 adults with cervical dystonia	Proportion of people with muscle weakness 5/78 (6%) with incobotulinumtoxinA (120 U) 8/81 (10%) with incobotulinumtoxinA (240 U) 1/74 (1%) with placebo	Significance not assessed
RCT	170 adults with cervical dystonia and who previously responded to onabotulinumtoxinA injections;	Proportion of people with treatment-related dysphagia 7% with known responders to onabotulinumtoxinA 0% with placebo Absolute numbers not reported	P = 0.03	Effect size not calculated	placebo
RCT	170 adults with cervical dystonia and who previously responded to onabotulinumtoxinA injections;	Proportion of people with treatment-related neck pain 1% with known responders to onabotulinumtoxinA 4% with placebo Absolute numbers not reported	Reported as not significant		Not significant