Effect on Pain Following One Session of Botulinum Toxin Type A in Patients With Jaw Myalgia: A Randomised Double-Blind Controlled Multicentre Pilot Study.

[BACKGROUND] Botulinum toxin Type A (BTX-A) is increasingly used in the management of myofascial pain; however, the evidence to support this treatment modality is still inconclusive.

[OBJECTIVE] To evaluate the change in days with functional jaw pain after one session of BTX-A or placebo injections into the masseter and temporalis muscles in subjects with jaw myalgia. The hypothesis was that BTX-A is effective in reducing the number of days with functional jaw pain.

[METHODS] This was a randomised, double-blind, parallel group study in subjects with jaw myalgia. After randomisation, BTX-A or placebo injections were made in the masseter and temporalis muscles. The number of days with jaw pain on function was evaluated after 2 months. Adverse events were registered.

[RESULTS] Twenty-three subjects were randomly assigned to BTX-A and 22 to placebo. Between baseline and the 2-month follow-up, the number of days with jaw pain at function changed from a median (interquartile range) of 14 (4) to 10.5 (6) days in the BTX-A group and from 14.0 (1.5) to 14 (5) in the saline group (p < 0.585). Adverse events were mild and transient and similar in the two groups.

[CONCLUSION] A single treatment of BTX-A injections in the masseter and temporalis muscles was not effective in treating jaw myalgia. However, an adequately powered study might provide sufficient support for efficacy.