A comparative trial of botulinum toxin type A and methylprednisolone for the treatment of myofascial pain syndrome and pain from chronic muscle spasm

Myofascial pain syndrome (MPS) is a common illness, characterised by acute or chronic focal pain, muscle stiffness and fatigue. The pathophysiology of MPS remains unclear. Previous preliminary studies have demonstrated therap eutic efficacy of the muscle relaxant botulinum toxin type A (BTX-A) in the treatment of MPS. A single-centre, randomised trial compared the effects o f BTX-A with the steroid methylprednisolone (both administered intramuscula rly with 0.5% bupivacaine), in 40 patients' suffering from chronic myofasci al pain in the piriformis, iliopsoas or scalenus anterior muscles. Thirty d ays after receiving an injection of either BTX-A or steroid followed by pos t-injection physiotherapy, pain severity had decreased significantly from b aseline in both treatment groups, with no significant difference between th e two treatment groups. However, the baseline pain score was significantly higher in the BTX-A treatment group compared with the steroid group (7.9 vs . 7.3), and the reduction in pain score between baseline and 30 days post-i njection was greater in the BTX-A group compared with the steroid group (-3 .9 vs. -3.5; P = 0.06). At 60 days post-injection, the pain severity score for the BTX-A-treated patients was statistically significantly lower than t he pain score for the steroid-treated population (2.3 vs. 4.9). Furthermore , the reduction in pain score in the BTX-A group at 60 days post-injection was greater than at 30 days (-5.5 vs. -3.9), whereas the effect of the ster oid had begun to wane. These results indicate the superior efficacy of BTX- A over conventional steroid treatment in patients suffering from MPS, when combined with appropriate physiotherapy. (C) 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reser ved.