The efficacy of botulinum toxin A treatment for tension-type or cervicogenic headache: a systematic review and meta-analysis of randomized, placebo-controlled trials.

Objectives: The pathogeneses of chronic tension-type headache (CTTH) and cervicogenic headache (CEH) are not well established. Peripheral activation or sensitization of myofascial nociceptors is suggested as a potential mechanism and injections of botulinum toxin (BONTA) have thus been used in the treatment for both headache conditions. BONTA inhibits the release of acetylcholine at the neuromuscular junction and inhibits contraction of skeletal muscles. If the pain is precipitated by increased tone in cervical muscles, local injections of BONTA could represent a prophylactic measure. However, the treatment is still controversial, and a thorough assessment of the current evidence is required. This review aims to assess the evidence of BONTA injection as a prophylactic treatment for CTTH and CEH by reviewing and examining the quality of placebo-controlled, randomized trials.
Methods: Data sources: we searched in the following databases: PubMed (including Medline), Embase, Cochrane Central register of Controlled Trials, Cinahl, Amed, SCOPUS and Google Scholar including other repository sources. Both MeSH and free keywords were used in conducting the systematic search in the databases. The search covered publications from the root of the databases to November 2020.
Study Eligibility Criteria: The review included RCTs, comparing single treatment of BONTA with placebo on patients with CTTH or CEH above 18 years of age, by measuring pain severity/relief or headache frequency.
Data Extraction: The following data were extracted: year of publication, country, setting, trial design, number of participants, injection procedure, BONTA dosages, and clinical outcome measures.
Study Appraisal: To assess validity and quality, and risk of bias, the Oxford Pain Validity Scale, Modified Jadad Scale, last version of Cochrane Collaboration's tool for assessing risk of bias (RoB 2), and the CONSORT 2010 Checklist were used. The trials were assessed, and quality scored independently by two of the reviewers. A quantitative synthesis and meta-analyses of headache frequency and intensity were performed.
Results: We extracted 16 trials, 12 on prophylactic BONTA treatment for CTTH and four on CEH. Of these 12 trials (8 on CTTH and 4 on CEH) were included in the quantitative synthesis. A majority of the trials found no significant difference on the primary outcome measure when BONTA treatment was compared with placebo. Three "positive" trials, reporting significant difference in favor of BONTA treatment, but two of these were hampered by low validity and quality scores and high risk of bias.
Conclusions: There is no clear clinical evidence supporting prophylactic treatment with BONTA for CTTH or CEH.
(© 2021 Sissel Breivold Roland et al., published by De Gruyter, Berlin/Boston.)