Introduction

1. Botulinum toxin A versus bupivacaine trigger point injections for the treatment of myofascial pain syndrome: A randomised double blind crossover study Corrie L. Graboski, D. Shaun Gray, Robert S. Burnham Pain. 2005 Nov;118(1-2):170-5. Epub 2005 Oct 3

2. Introduction • Myofascial pain syndrome (MPS) is characterized by muscle pain, tenderness, fatigue and stiffness. • The hallmark physical examination finding of MPS is the trigger point.

3. Introduction • The etiology of the trigger point is poorly understood. • Treatment of MPS is diverse and includes steroids,NSAIDs, antidepressants, physiotherapy/exercise and trigger point injections .

4. Introduction • Dry needling of the trigger point, as well as the injection of various substances including local anesthetics and botulinum toxin have been shown to be effective. • BTX A is a potent neurotoxin that blocks the release of acetylcholine at the neuromuscular junction and thereby inhibits muscle contraction.

5. The purpose of our study was to compare the effectiveness of trigger point injections using BTX A versus bupivacaine in combination with a home-based rehabilitation program for the treatment of MPS.

6. Methods Assessment at Baseline Study PopulationRandomization (N=18) Group A: BotulinumGroup B:Bupivacaine toxin A (N=9) (N=9) Followed until pain returned to 75% of pre-injection pain based on weekly self reported average VAS pain score over preceding week Self-Reported questionnaires of satisfaction, cost, function measured every two weeks Washout 2 Weeks

7. Methods Group B:BupivacaineGroupA: Botulinum (N=9) toxin A (N=9) Followed until pain returned to 75% of pre-injection pain based on weekly self reported average VAS pain score over preceding week Self-Reported questionnaires of satisfaction, cost, function measured every two weeks Withdrawn (N=0) Withdrawn (N=1) Completed Trial (N=9) Completed Trial(N=8)

8. Results • Mean age = 51.1 years • Female = 9 Male = 8 • Average preinjection pain intensity = 6.9 • Average number of trigger points injected per subject = 6.1

9. Results • No significant difference between BTX A and 0.5% bupivacaine in the magnitude, duration of pain relief andspeed of pain relief response

10. Results • No difference in indirect and direct costs incurred to the subjects • The amount of medication used was also not different between groups • No difference in the first satisfaction measure or the second satisfaction measure

11. Discussion • No differences between the two agents • These findings are in agreement with some previous studies (Kamanli et al., 2004; Wheeler et al., 1998; Wheeler et al., 2001) but in disagreement with others (Cheshire,1994; Freund and Schwartz, 2000; Lang, 2000; Porta,2000).

12. Discussion • A less likely explanation for the similar results of BTX A and 0.5% bupivacaine is incorrect dosing. • The site of administration of the BTX A injections may be another factor in effectiveness as a treatment for myofascial pain.

13. Discussion • The mean duration of pain relief in our study was only 4 weeks. • When the cost of the injectate is excluded, there was no significant difference in cost of care between the two groups. However, when the cost of the injectate is considered, it was quite a different story.

14. Conclusions • No benefit to injecting BTX A over 0.5% bupivacaine in any outcome measure when combined with a home based exercise program for the treatment of MPS.