Effectiveness of botulinum toxin type A for the treatment of chronic masticatory myofascial pain: A case series.

[BACKGROUND] The aim of this study is to evaluate the effectiveness of botulinum toxin type A (BTX-A) for the treatment of chronic masticatory myofascial pain (MMP) over 12 months and to test a standardized protocol.

[METHODS] This is a prospective case series of consecutive adult patients with chronic MMP treated with injection of BTX-A into the bilateral temporalis and masseter muscles. The authors used the same anatomic landmarks and dosage and followed each patient for 12 months. The primary outcome variables were reduction in pain measured with visual analog scale (VAS) and Physician Global Assessment (PGA). Secondary outcome variables were change in maximum pain-free opening, change in palpatory pain points in the face and oral cavity, and change in results from a questionnaire measuring disability, dysfunction, and psychosocial effects of the disease.

[RESULTS] The authors included 15 women and 4 men (mean [standard deviation] age, 32.7 [6.9] years) in the study. Pain decreased significantly as measured with the VAS (P < .0001) and PGA (P < .0001). Maximum pain-free opening increased significantly (P = .010), but maximum voluntary opening did not change significantly (P = .837). The number of palpatory pain points (P < .0001) and the symptom questionnaire score decreased over time (P < .0001).

[CONCLUSIONS] The results of this case series suggest that injecting BTX-A into the bilateral temporalis and masseter muscles may be a safe and effective treatment for chronic MMP.

[PRACTICAL IMPLICATIONS] Controlled clinical trials are needed to confirm whether administration of BTX-A is effective in treating facial pain.