425 Pain Representation in Fibromyalgia Patients and Healthy Controls Using Eventrelated Fmri

Objectives: The aim of this work was to determine the effect of small doses (5U) of botulinum toxin A (BTA) injected directly into the painful trigger points of the muscles. Methods: 42 patients suffering from myofascial pain in the neck-shoulder region were studied. The patients received either botulinum toxin A or physiological saline injections on 3 occasions 6 weeks apart. The total dose varied from 15 to 35 U of botulinum toxin A [27±4U (mean±SD)]. The follow-up measurements were carried out at 6 weeks after each treatment. Results: Neck pain values decreased from 5.1±1.9 to 3.1±1.8 after saline injections and from 4.8±1.5 to 2.9±1.6 after botulinum toxin A. The pressure pain threshold values increased from 5.4±1.7 to 5.8±1.2 and from 5.3±2.0 to 5.5±1.9 after injections with saline and botulinum toxin A, respectively. No statistically significant changes in the neck pain and pressure pain threshold values occurred between the botulinum toxin A and saline groups. After the first injections, the subjective result of treatment was significantly (P = 0.005) in favor of botulinum toxin A, and after the second injections, the subjective result was better for saline, but the difference was not statistically significant (P = 0.008). There was no significant difference in the prevalence of side effects between saline and botulinum toxin A. Conclusions: Our study shows that there was no difference between the effect of small doses of botulinum toxin A and those of physiological saline in the treatment of myofascial pain syndrome.