BACKGROUND: Conventional treatment for reducing pain is not always successful in patients with chronic orofacial myalgia.

OBJECTIVE: The objective of this study was to investigate the pain-reducing efficacy of two botulinum toxin A injections in patients with chronic orofacial myalgia who had already received conservative treatment.

METHODS: The patients included were 18 years or older and diagnosed with myalgia according to the Diagnostic Criteria for Temporomandibular Disorders. Their pain had persisted for more than six months in spite of previous conservative treatment. The design was a randomised, double-blind, placebo-controlled, multicenter, parallel group study. Participants received two injections of botulinum toxin A or saline at an interval of three months. Follow-up visits were conducted at one, three, four, six and nine months after the first injection.

RESULTS: Seventy-two patients were enrolled and sixty-nine completed the study. Between baseline and all follow-up visits, there was a significant decrease in VAS pain intensity for both groups, but the difference between groups was not significant.

CONCLUSION: The use of botulinum toxin A in managing chronic orofacial myalgia did not offer any additional pain relief compared with saline at any of the follow-up occasions.