title: Responsiveness to botulinum toxin type A in muscles of complex regional pain patients with tonic dystonia.
abstract: Tonic dystonia of the limbs in complex regional pain syndrome (CRPS) is associated with considerable disability. Treatment options are scarce. Botulinum toxin (BoNT) is sometimes used, but the effect is often said to be disappointing. However, this notion stems from case reports and clinicians' opinions but has never been formally studied. We therefore investigated responsiveness to BoNT in CRPS patients with tonic dystonia. We injected the extensor digitorum brevis (EDB) muscle with BoNT-A in 17 patients with CRPS and tonic dystonia to compare the response between affected and unaffected legs. We also investigated the right legs of 17 healthy controls. Responsiveness was defined as a decrease of the amplitude of the compound muscle action potential (CMAP) of >20% from baseline 2 weeks after BoNT-A injection. We controlled for a temperature effect on BoNT efficacy by measuring skin temperature hourly directly above the EDB muscle in the first 2 weeks. CMAP amplitude decreased >20% after injection on the affected side in 16 of 17 CRPS patients, similar to the response in unaffected legs (12/13) or legs of controls (17/17). The degree of CMAP reduction was significantly smaller in patients than in controls (56.0 ± 22.3 vs. 70.6 ± 14.6%; p = 0.031). This may be due to a lower physical activity level and a greater difficulty to localize the EDB muscle properly in affected legs. The decrease in CMAP amplitude was not related to skin temperature. Contrary to the prevailing opinion, BoNT-A has a normal, although perhaps slightly lower efficacy in CRPS patients with dystonia.
authors: Department of Neurology and Clinical Neurophysiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands, j.c.m.schilder@lumc.nl.
authors: Johanna C M
authors: JC
authors: Schilder
authors: J Gert
authors: JG
authors: van Dijk
authors: Dirk
authors: D
authors: Dressler
authors: Johannes H T M
authors: JH
authors: Koelman
authors: Johan
authors: J
authors: Marinus
authors: Jacobus J
authors: JJ
authors: van Hilten
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D004421:Dystonia / Q000150:complications*; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology*; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D012019:Reflex Sympathetic Dystrophy / Q000188:drug therapy* / Q000209:etiology*; D055815:Young Adult
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A