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Botulinum toxin A for the treatment of cervical dystonia
Introduction: Dystonia is more common than many other neurological diseases, such as Huntington's disease, Amyotrophic Lateral Sclerosis and Myasthenia gravis. Its prevalence is 3.4–29.5 per 100 000 for generalized and focal dystonia. Cervical dystonia (CD) is the most current form of adult-onset focal dystonia. The aetiology of CD is unknown, but genetic and environmental factors are implicated. Dystonia can cause significant disability, and the usual therapeutic approach is mainly symptomatic. Botulinum toxin (BTX) is nowadays regarded as first-line treatment for CD and has dramatically improved the quality of life of CD patients.
Methods: We performed a retrospective study of 207 patients with CD who were treated in our BTX-outpatient clinic with BTX type A (Dysport® and Botox®) between 1994 and 2006. Data of mean BTX dose, site and number of BTX injections per each treated muscle, mean response rate, mean latency of response and mean total duration of response were derived from our database (Microsoft Office Access 2003). The response rate was based on a 0–3 scale (0=no effect; 3=marked improvement). SPSS v 14.0 (SPSS, Chicago, IL) was used for statistical analysis.
Results: 163 patients were treated with Dysport® and 44 with Botox®. The mean dose for Dysport was 389 MU, for Botox 145 MU. The mean latency of response was nearly the same for Dysport® (7.6 days) and Botox® (7.7 days), and also the mean total duration of response for both products showed no significant difference (Dysport® 11 weeks, Botox® 10 weeks). The mean response rate was 2.5 for Dysport® and 2.2 for Botox®, which demonstrates a pronounced effect. Side-effects included mild dysphagia and neck weakness. The risk of immunoresistance due to blocking antibodies was relatively small.
Discussion: This study confirms the efficacy and safety of BTX A treatment in CD and shows that a mean dose of less than 500MU Dysport® or 200MU Botox® has a satisfactory effect in the response rate and in the total duration of response.