The effectiveness of botulinum toxin for chronic tension-type headache prophylaxis: A systematic review and meta-analysis.

[BACKGROUND] A systematic and meta-analysis was conducted to examine the evidence of the effects of botulinum toxin A on chronic tension-type headache.

[METHODS] Cochrane, Embase, Ovid, ProQuest, PubMed, Scopus, Web-of-Science databases, and ClinicallTrials.gov registry were systematically searched for studies examining the effects of botulinum toxin A on tension-type headaches. The records were screened by two independent reviewers using pre-determined eligibility criteria. DerSimonian Liard random-effects meta-analyses were performed using the 'meta' package (5.2-0) in R (4.2.0). Risk of bias and quality of evidence were assessed using the Cochrane Collaboration's Tool RoB 2 and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Clinical significance was determined using pre-defined minimal clinically important differences.

[RESULTS] Eleven controlled trials were included (390 botulinum toxin A, 297 controls). Botulinum toxin A was associated with significant improvements in standardized headache intensity (-0.502 standard deviations [-0.945, -0.058]), headache frequency (-2.830 days/month [-4.082, -1.578]), daily headache duration (-0.965 [-1.860, -0.069]) and the frequency of acute pain medication use (-2.200 days/month [-3.485, -0.915]) vs controls. Botulinum toxin A-associated improvements exceeded minimal clinically important differences for headache intensity, frequency, and acute pain medication use. A 79% (28%, 150%) greater response rate was observed for botulinum toxin A vs controls in improving chronic tension-type headache. Treatment of eight chronic tension-type headache patients was sufficient to elicit a therapeutic response in one patient.

[CONCLUSIONS] Corroborating the current mechanistic evidence, our meta-analysis supports the utility of botulinum toxin A for managing chronic tension-type headaches. However, due to limitations in the quality of evidence, adequately-powered high-quality controlled trials examining the effects of Botulinum toxin A on chronic tension-type headache are warranted.

[REGISTRATION] Protocol preregistered in PROSPERO International Prospective Register of Systematic Reviews (CRD42020178616).