Systematic review: can botulinum toxin be recommended as treatment for pain in myofascial syndrome?

Myofascial pain syndrome (MPS) may have an intrinsic muscle spasm component. Aim: Since botulinum toxin has been successfully used to reduce hypertonicity in several neurological disorders, we analyzed the efficacy of botulinum toxin A or B in reducing pain in MPS. Methods: We performed a systematic review through an electronic search in MEDLINE, EMBASE, and Cochrane Library Plus. All clinical trials of botulinum toxin and regional pain were selected. In addition, the abstracts of the ACR and EULAR meetings in the previous 3 years were searched manually. The studies identified were reviewed and analyzed by 2 independent reviewers. Results: Eight studies met the inclusion criteria. The methodological quality was generally low. Botulinum toxin was compared to saline solution (6 studies), to steroids (2 studies), and to lidocaine and dry needle (1 study arm). The population studied included persons with neck pain (n = 3), low back pain (n = 2), piriformis syndrome (n = 2), several trigger points (n = 1), and healthy volunteers in whom pain was provoked (n = 1). Botulinum toxin showed a certain advantage over saline solution and steroids in pain control. A meta-analysis of the 3 studies with efficacy measures that could be combined showed a weighted mean difference in pain on a 0-10 visual analogue scale of -2.72 (95% CI: -3.86; -1.58). However, botulinum toxin showed no advantage over lidocaine (p > 0.016). Conclusions: Currently, there is insufficient evidence to confirm the real efficacy of botulinum toxin A and B in the treatment of MPS. Given the high cost of botulinum toxin, long-term high quality studies are required.