Effects of Botulinum Toxin Type A on the Psychosocial Features of Myofascial Pain TMD Subjects: A Randomized Controlled Trial.

[AIMS] To determine the effects of botulinum toxin type A (BoNT-A) on the psychosocial features of patients with masticatory myofascial pain (MFP).

[METHODS] A total of 100 female subjects diagnosed with MFP were randomly assigned into five groups (n = 20 each): oral appliance (OA); saline solution (SS); and three groups with different doses of BoNT-A. Chronic pain-related disability and depressive and somatic symptoms were evaluated with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis II instruments at baseline and after 6 months of treatment. Differences in treatment effects within and between groups were compared using chi-square test, and Characteristic Pain Intensity (CPI) was compared using two-way ANOVA. A 5% probability level was considered significant in all tests.

[RESULTS] Most patients presented low pain-related disability (58%), and 6% presented severely limiting, high pain-related disability. Severe depressive and somatic symptoms were found in 61% and 65% of patients, respectively. In the within-group comparison, BoNT-A and OA significantly improved (P < .001) scores of pain-related disability and depressive and somatic symptoms after 6 months. Only the scores for pain-related disability changed significantly over time in the SS group. In the between-group comparison, BoNT-A and OA significantly improved (P < .05) scores of all variables at the final follow-up when compared to the SS group. No significant difference was found between the BoNT-A and OA groups (P > .05) for all assessed variables over time.

[CONCLUSION] BoNT-A was at least as effective as OA in improving pain-related disability and depressive and somatic symptoms in patients with masticatory MFP.