Abstract

CASTRO, M. et al. Botulinum toxin type A in the management of Myofascial pain syndrome. Rev. Soc. Esp. Dolor [online]. 2006, vol.13, n.2, pp.96-102. ISSN 1134-8046.

Introduction: Myofascial pain syndrome (MPS) is a condition characterised by painful areas of skeletal muscle and by the clinical and electromyographic evidences of contraction of muscle’s band associated with trigger points. Trigger points are locally tender muscle areas when active and refer pain through specific patterns to other areas of the body. The physiopathology is unknown and a possible explication could be to muscle lesion caused by microtrauma, overuse, excessive strain o prolonged spasm.Botulinum toxin is produced by the microorganism Clostridium botulinum in anaerobic conditions and is one of the strongest known substances. Material and methods: It is an observational prospective study. The aim of the study was to evaluate the clinical efficacy and safety of the muscular injection of the botulinum toxin in reducing pain in the MPS in 20 patients. All patients had a diagnostic injection of the lumbar musculature or the piriformis muscle of 8 ml of 0.2% ropi-vacaine and 6 mg of sodium betamethasone phosphate and 6 mg of acetate betamethasone in each muscle. We used anatomical references to localise each muscle and we injected 1 ml of hydrosoluble contrast to confirm by radioscopy guidance the correct localization of the needle in the muscle to treat. The administration of the botulinum toxin was carried out using the same method used for the diagnostic infiltrations. We decided to use one dose of 250 U of Dysport^® in each muscle and we exceeded 1000 U in none patient. The assessment of the treatment efficacy was based on the pain reduction according to the visual analog scale (VAS) on the first day of the injection (VAS 1), at day 15 (VAS 15), day 30 (VAS 30) and day 90 (VAS 90) after insertion of the botulinum toxin and the test of Lattinen was evaluated before the treatment (TLT 1) and at the completion of the study (TLT 2). All patients were asked regarding side effects and the grade of satisfaction at the end of the study was defined as excellent, good, regular or bad. Results: In all patients, the diagnostic injection was considerate positive with the posterior administration of the botulinum toxin. There was at least a reduction of 50% of the pain in the EVA in the 20 cases at day 15 and 30. At day 90, the reduction of the pain at 50% was maintained in 13 patients and less than 50% in the rest of the patients. The initial median EVA was 7.7 ± 1.2 standard desvia-tion and the TLT median initial of 12± 2.3. The evolution of the EVA median in the following controls was EVA 15 = 3,34 ± 2,5; EVA 30 = 3,54 ± 2,37 y EVA 90 = 4,94 ± 2,83. The median TLT at day 90 was de 7,43 ± 3,49. Only one patient referred mild muscle weakness of the lower limbs during 48 hours following the injection that improved spontaneously. The satisfaction was excellent in 10 patients (50%), good in 7 (35%) and average in 3 (15%). None of the patient qualified the experience as bad. Conclusion: The muscular injection of botulinum toxin type A in the treatment of MSP is effective and safe.

Keywords : Myofascial pain syndrome; Botulinum toxin.

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