Clinical benefit of botulinum toxin for treatment of persistent TMD‐related myofascial pain: A randomized, placebo‐controlled, cross‐over trial

Abstract Background Injections of botulinum toxin type A (BoNT‐A) have been proposed as an additional treatment modality for patients suffering chronic temporomandibular disorder (TMD)‐related myofascial pain (MFP). BoNT‐A impairs muscle function, along with its analgesic effect, and a minimal effective dose should be used. The objective of this randomized placebo‐controlled crossover study was to evaluate the clinical benefit of a moderate dose (50 U) of BoNT‐A. Methods Sixty‐six subjects were randomized into two groups, one which received BoNT‐A first and a second which received a saline solution (SS) first. Follow‐ups were performed 2, 11, and 16 weeks after the injections. Diagnostic criteria for temporomandibular disorders (DC/TMD) diagnostic algorithms were used to evaluate characteristic pain intensity (CPI) and pain‐related disability based on the Graded Chronic Pain Scale (GCPS). Electromyographic and bite force were also evaluated. Results The within‐group analysis showed a significant improvement in pain intensity and pain‐related disability after BoNT‐A ( p < 0.001, p = 0.005, p = 0.011) and SS ( p = 0.003, p = 0.005, p = 0.046) injections up to week 16. The between‐group analysis of pain‐related variables revealed no differences between groups at any time. Nonetheless, BoNT‐A, but not SS, caused a significant decline in muscle performance. The number needed to treat (NNT) regarding a clinically significant pain reduction (≥30%) was 6.3, 57.0, and 19.0 at 2, 11, and 16‐week follow‐ups favoring BoNT‐A. Conclusions Injections of 50 U of BoNT‐A might improve MFP symptoms, but the specific effect of the drug on pain compared to the placebo is not obvious.