Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	66 adults Data from 1 RCT	Number of adverse effects in each group 31 in 32 people with botulinum A toxin (Dysport, 292 U in first session, 262 U in second session, under EMG guidance) plus placebo tablets 76 in 32 people with trihexyphenidyl plus placebo	P = 0.0001	Effect size not calculated	botulinum A toxin
Systematic review	66 adults Data from 1 RCT	Dry mouth with botulinum A toxin plus placebo with trihexyphenidyl plus placebo Absolute results not reported	OR 7.22 95% CI 2.72 to 19.12	Large effect size	botulinum A toxin
Systematic review	66 adults Data from 1 RCT	Forgetfulness with botulinum A toxin plus placebo with trihexyphenidyl plus placebo Absolute results not reported	OR 3.51 95% CI 1.25 to 9.89	Moderate effect size	botulinum A toxin
Systematic review	66 adults Data from 1 RCT	Fatigue with botulinum A toxin plus placebo with trihexyphenidyl plus placebo Absolute results not reported	OR 9.12 95% CI 1.92 to 43.40 The extremely wide confidence intervals make the clinical relevance of this result questionable	Moderate effect size	botulinum A toxin