Objectives: Studies on the use of botulinum toxin A (BoNT-A) in TMD-related myalgia suggest that some patients benefit from the injections. The aim of this study was to assess which patient group, regarding pain sites and self-reported comorbid pains, benefits most from the injections.
Materials and methods: 66 patients were enrolled in a randomized, double-blind, cross-over study. In the first period, patients in group 1 (n=33) were injected with 50 U of BoNT-A, and patients in group 2 (n=33) with saline solution. The cross-over was at 16 weeks. A final cohort of 54 patients with full follow-up data was included in the statistical analyses. Patients were pooled and divided into three groups depending on the extent of the pain areas based on their pain drawings (PD): regional (RP), local (LP) widespread (WP) pain groups. Treatment response assessment was performed using Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) tools.
Results: In the short term (2 weeks), a clear reduction in pain areas was observed in the LP (84.2%) and RP groups (80.9%), but not in the WP group (64.3%). In the long term (16 weeks), the reduction in pain areas was most evident in the RP group (71.4%), with significant pain reduction in the shoulder and back areas (p<0.05). The reduction of pain intensity and pain-related disability was least evident in the WP group.
Conclusion: BoNT-A injections might be considered for treatment in patients with localized and regional pain, however other treatment modalities should be considered in patients with widespread pain. Pain drawing could be a useful screening tool for treatment planning.
Keywords: botulinum toxin type A; chronic pain; masticatory muscle disorder; myofascial pain; pain drawing; temporomandibular disorders.
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