BACKGROUND: Myofascial pain syndrome is a regional condition of muscle pain and stiffness and is classically characterized by the presence of trigger points in affected musculature. Botulinum toxin type A (BoNT-A) has been shown to have antinociceptive properties and elicit sustained muscle relaxation, thereby possibly affording even greater relief than traditional strategies. Our goal was to determine whether direct injection of BoNT-A into painful muscle groups is effective for cervical and shoulder girdle myofascial pain.
METHODS: An enriched protocol design was used, wherein 114 patients with cervical and shoulder girdle myofascial pain underwent injection of BoNT-A to determine their response to the drug. Fifty-four responders were then enrolled in a 12-week, randomized, double-blind, placebo-controlled trial. Pain scales and quality of life measures were assessed at baseline and at routine follow-up visits until completion of the study after 26 weeks.
RESULTS: Injection of BoNT-A into painful muscle groups improved average visual numerical pain scores in subjects who received a second dose of BoNT-A compared to placebo (P = 0.019 [0.26, 2.78]). Subjects who received a second dose of BoNT-A had a reduced number of headaches per week (P = 0.04 [0.07, 4.55]). Brief Pain Inventory interference scores for general activity and sleep were improved (P = 0.046 [0.038, 3.700] and 0.02 [0.37, 4.33], respectively) in those who received a second dose of BoNT-A.
CONCLUSION: BoNT-A injected directly into painful muscle groups improves average pain scores and certain aspects of quality of life in patients experiencing severe cervical and shoulder girdle myofascial pain.
From the Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California.
Andrea L. Nicol, MD, MS, is currently affiliated with Department of Anesthesiology, University of Kansas School of Medicine, Kansas City, Kansas.
Accepted for publication January 29, 2014.
Funding: Research support provided by Allergan, Inc., 2525 Dupont Drive, Irvine, CA 92612. The research and statistical analysis described was supported by NIH/National Center for Advancing Translational Science (NCATS) UCLA CTSI Grant Number UL1TR000124.
The authors declare no conflicts of interest.
Reprints will not be available from the authors.
Address correspondence to Andrea L. Nicol, MD, MS, Department of Anesthesiology, University of Kansas Medical Center, 3901 Rainbow Blvd., Mailstop 1034, Kansas City, KS 66160. Address e-mail to firstname.lastname@example.org.