Botulinum toxin: new treatment for temporomandibular disorders

Background: Temporomandibular disorders (TMDs) affect the face and jaws, and cause chronic pain and dysfunction in many people. As in other conditions involving the musculoskeletal system, controlling the myogenous component is an integral part of treatment. In this study, we evaluated subjective and objective responses to treatment with botulinum toxin A (BTX-A) in a group of 46 patients with TMDs. Methods: 46 subjects with TMD were enrolled in this uncontrolled study and treated with BTX-A 150U. Both masseter muscles were injected with 50 U each and both temporalis muscles with 25 U each under electromyographic guidance. Subjects were assessed at two-week intervals for eight weeks. Outcome measures included subjective assessment of pain by visual analogue scale (VAS), measurement of mean maximum voluntary contraction (MVC), interincisal oral opening, tenderness to palpation, and a functional index based on multiple VAS. Medians of the data were taken for each outcome measure at each time point and subjected to Duncan's multiple range test. Results: There were significant (P<0.05) differences in all median outcome measures between the pre-treatment assessment and the four follow-up assessments except for MVC. Although MVC was significantly reduced midway through the study, it had returned to pretreatment values by the final two assessments. All other outcome measures remained significantly different from the pretreatment findings. Paired correlation of variables including age, sex, diagnosis, depression index, and time of onset showed no significant differences. Conclusions: BTX-A injections produced significant improvements in pain, function, mouth opening, and tenderness to palpation. MVC initially diminished then returned to the initial values. Although the study was uncontrolled, the results strongly suggest that BTX-A reduces severity of symptoms and improves functional abilities for patients with TMD and that these extend beyond its muscle-relaxing effects. (C) 2000 The British Association of Oral and Maxillofacial Surgeons.