Freund B, et al. - In this systematic review, researchers assessed the efficacy of botulinum toxin in cases of chronic tension-type headaches (CTTH). They included 22 studies, including 9 non-randomized, uncontrolled studies, 8 randomized, placebo-controlled and double-blinded trials (RCT), 3 RCTs with a cross-over, open label period, one comparative, randomized, single-blinded evaluation, and one retrospective study with prospective evaluation of headache response to cosmetic botulinum toxin. These studies yielded low quality of evidence regarding botulinum toxin in TTH. However, some data suggest it as efficacious. The evidence did not support a lack of efficacy of botulinum toxin in TTH. In the treatment of CTTH, using the paradigm for botulinum toxin in chronic migraine may prove productive.