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Objectives-Botulinum toxin injections have become a first line therapeutic approach in cervical dystonia. Nevertheless, published dosing schedules, responder rates, and frequency of adverse events vary widely. The present prospective multicentre placebo controlled double blind dose ranging study was performed in a homogenous group of previously untreated patients with rotational torticollis to obtain objective data on doseresponse relations. Methods-Seventy five patients were randomly assigned to receive treatment with placebo or total doses of 250, 500, and 1000 Dysport® units divided between one splenius capitis (0, 175, 350, 700 units) and the contralateral sternocleidomastoid (0, 75, 150, 300 units) muscle. Assessments were obtained at baseline and weeks 2, 4, and 8 after treatment and comprised a modified Tsui scale, a four point pain scale, a checklist of adverse events, global assessment of improvement, and a global rating taking into account eYcacy and adverse events. At week 8 the need for retreatment was assessed and then the code was unblinded. For those still responding, there was an open follow up until retreatment to assess the duration of eVect. Results-seventy nine per cent reported subjective improvement at one or more follow up visits. Decreases in the modified Tsui score were significant at week 4 for the 500 and 1000 unit groups versus placebo (p<0.05). Additionally positive dose-response relations were found for the degree of subjective improvement, duration of improvement, improvement on clinical global rating, and need for reinjection at eight weeks. A significant dose relation was also established for the number of adverse events overall and for the incidence of neck muscle weakness and voice changes. Conclusion-Magnitude and duration of improvement was greatest after injections of 1000 units Dysport®; however, at the cost of significantly more adverse events. Therefore a lower starting dose of 500 units Dysport® is recommended in patients with cervical dystonia, with upward titration at subsequent injection sessions if clinically necessary. (J Neurol Neurosurg Psychiatry 1998;64:13-17) Keywords: botulinum toxin A; cervical dystonia; dose range Cervical dystonia is a common form of focal dystonia with an estimated prevalence of at least 8/100 000.1 Medical treatment of the condition has generally been unsatisfactory. Over the past 10 years local injection of botulinum toxin into various neck muscles has become the first line therapeutic approach and published data from controlled and uncontrolled clinical studies now cover many thousands of treatment sessions in hundreds of patients.2-18 Responder rates vary widely between 20% and 75% based on variable assessment methods and variable doses used and most of the clinical information comes from open label trials.11-18 There continues to be considerable uncertainty about optimal doses of botulinum toxin type A for the treatment of cervical dystonia. The issue is further complicated by the fact that the assays used to determine the ...

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