Dystonia is a hyperkinetic movement disorder, characterized by involuntary and sustained contractions of opposing muscles causing twisting movements and abnormal postures. It is often a disabling disorder that has a significant impact on physical and psychosocial wellbeing. The medical therapeutic armamentarium used in practice is quite extensive, but for many of these interventions formal proof of efficacy is lacking. Exceptions are the use of botulinum toxin in patients with cervical dystonia, some forms of cranial dystonia (in particular, blepharospasm) and writer's cramp; deep brain stimulation of the pallidum in generalized and segmental dystonia; and high-dose trihexyphenidyl in young patients with segmental and generalized dystonia. In order to move this field forward, we not only need better trials that examine the effect of current treatment interventions, but also a further understanding of the pathophysiology of dystonia as a first step to design and test new therapies that are targeted at the underlying biologic and neurophysiologic mechanisms. http://tan.sagepub.com dystonia are given intramuscularly, often under electromyography (EMG) guidance, and need to be repeated every 3-6 months. Contraindications for the use of BoNT include history of neuromuscular disease, e.g. myasthenia gravis, LambertEaton syndrome or motor neuron disease, and a history of hypersensitivity to BoNT, albumin or saline. BoNT injections are also contraindicated in combination with aminoglycoside, penicillamine, quinine and calcium-channel blockers as the effect of these drugs may be potentiated. As teratogenicity of BoNT is still unknown, it is advised not to use BoNT during pregnancy and lactation.
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Cervical dystoniaBoNT injections are the first-line therapy for cervical dystonia (CD). Meta-analysis of several double-blind, placebo-controlled trials have demonstrated a beneficial effect of the BoNT type A (BoNT-A) versus placebo on multiple domains, such as dystonia severity, pain and the patient's and physician's subjective judgement. Adverse events are usually transient and mild. The most relevant side effects, of increasing frequency with higher doses and therefore dose-limiting, are neck weakness, dysphagia, dry mouth/sore throat and voice changes/hoarseness. Others are doseindependent and include pain at the site of injection, malaise, upper respiratory infection and headache [Costa et al. 2005b].BoNT also has proven long-term safety and efficacy. Several large case series have shown treatment efficacy up to 10 years, without longterm adverse effects [Blackie and Lees, 1990;Haussermann et al. 2004]. The occurrence of a secondary nonresponse, likely due to antibodies to BoNT or other components, was rare (1-2%) [Kessler et al. 1999;Haussermann et al. 2004;Brin et al. 2008]. Also primary nonresponse is seen, but reports documenting its occurrence are sparse [Truong et al. 2005]. A comparison of efficacy and safety between two preparations of BoNT-A, (onabotulinumtoxinA [Botox ® ] and rimabotulinumtoxin...