Summary of findings for the main comparison. Botulinum neurotoxin B compared to placebo for cervical dystonia.
| Botulinum Neurotoxin B compared to placebo for cervical dystonia | ||||||
| Patient or population: adults with cervical dystonia Settings: hospital‐based, movement disorders clinics Intervention: botulinum neurotoxin B Comparison: placebo | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of Participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Placebo | Botulinum Neurotoxin B | |||||
| Overall cervical dystonia improvement as assessed with TWSTRS: change from baseline to week 4 (range, 0 to 85; more is worst) |
‐7 | ‐7 | The mean change from baseline to week 4 in the BtB group was 6.78 TWSTRS units higher (4.54 higher to 9.01 higher) compared to the placebo group | 316 (3 RCTs) | ⊕⊕⊕⊝ MODERATE 1 | |
| Proportion of withdrawals due to adverse events | Study population | RR 0.88 (0.19 to 4.06) | 440 (4 RCTs) | ⊕⊕⊝⊝ LOW 2,3 | ||
| 14 per 1000 | 13 per 1000 (3 to 58) | |||||
| Cervical dystonia associated pain: change from baseline to week 4 as assessed with TWSTRS (range, 0 to 20; more is worst) |
‐7 | ‐7 | The mean change from baseline to week 4 in the BtB group was 2.41 TWSTRS units higher (0.82 higher to 4.01 higher) compared to the placebo group | 207 (2 RCTs) | ⊕⊕⊝⊝ LOW 3,4 | |
| Subjective change as assessed by the patient at week 4 | ‐7 | ‐7 | The mean change at week 4 in the BtB group was 0.86 standard deviations higher (0.61 higher to 1.1 higher) compared to the placebo group | 316 (3 RCTs) | ⊕⊕⊕⊕ HIGH 1 | |
| Proportion of participants with adverse events | Study population | RR 1.09 (0.97 to 1.23) | 186 (2 RCTs) | ⊕⊝⊝⊝ VERY LOW 3,5,6 | ||
| 838 per 1000 | 930 per 1000 (796 to 1000) | |||||
| Adverse events: dry mouth | Study population | RR 7.65 (2.75 to 21.32) | 438 (4 RCTs) | ⊕⊕⊕⊕ HIGH 2 | ||
| 22 per 1000 | 168 per 1000 (60 to 467) | |||||
| Adverse events: dysphagia | Study population | RR 6.78 (2.42 to 19.05) | 438 (4 RCTs) | ⊕⊕⊕⊕ HIGH 2 | ||
| 22 per 1000 | 148 per 1000 (53 to 417) | |||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
1Two of 3 studies enrolled an enriched population; none of the included studies had independent funding; blinding of outcome assessment was unclear in all studies
2Three of 4 studies enrolled an enriched population; none of the studies had a clearly stated independent funding; blinding of outcome assessment was unclear in all studies; two out of 4 had an unclear random sequence generation
3The total number of participants included was less than the number generated by a conventional sample size calculation for a single adequately powered trial
4I‐squared of 58% and small overlap between confidence intervals
5Both studies had an enriched population and non‐independent funding; blinding of outcome assessment was unclear in all studies
6I‐squared of 45% and there is a wide variance of point estimates between studies
7 Data were only available as the difference between the BtB and placebo groups