Background
Traditional strategies for myofascial pain relief provide transient, incomplete, variable, or unpredictable outcomes. Botulinum toxin is itself an analgesic but can also cause sustained muscular relaxation, thereby possibly affording even greater relief than traditional therapies.
Methods
The study goal was to determine whether direct injection of botulinum toxin type A (BoNT-A) into trigger points was efficacious for cervicothoracic myofascial pain, and if so, to determine the presence or absence of a dose-response relation. One hundred thirty-two patients with cervical or shoulder myofascial pain or both and active trigger points were enrolled in a 12-week, randomized, double-blind, placebo-controlled trial. After a 2-week washout period for all medications, patients were injected with either saline or 10, 25, or 50 U BoNT-A into up to five active trigger points. The maximum doses in each experimental group were 0, 50, 125, and 250 U per patient, respectively. Patients subsequently received myofascial release physical therapy and amitriptyline, ibuprofen, and propoxyphene-acetaminophen napsylate. Follow-up visits occurred at 1, 2, 4, 6, 8, and 12 weeks. Outcome measures included visual analog pain scores, pain threshold as measured by pressure algometry, and rescue dose use of propoxyphene-acetaminophen napsylate.
Results
No significant differences occurred between placebo and BoNT-A groups with respect to visual analog pain scores, pressure algometry, and rescue medication.
Conclusions
Injection of BoNT-A directly into trigger points did not improve cervicothoracic myofascial pain. The role of direct injection of trigger points with BoNT-A is discussed in comparison to other injection methodologies in the potential genesis of pain relief.
