Dystonia is a symptom that involves involuntary muscle contractions that are frequently sustained, but can be phasic. These contractions or spasms frequently result in abnormal posturing or repetitive movements in various parts of the body. Dystonia is often accompanied by tremor.

Dystonia has multiple causes but may be categorised by age at onset or by the underlying aetiology as either primary (idiopathic), which may be sporadic or familial, or secondary, the latter oftenresulting from a neurodegenerative disorder.¹ The most commonly inherited form of primary dystonia results from a defect in the DYT-1 gene.² The specific syndromes of myoclonus-dystonia and dopa-responsive dystonia are classified under the term ‘dystonia plus syndromes’.

Dystonia can also be categorised anatomically according to the part(s) of the body affected by dystonia:

• focal dystonia – involves a single part of the body, for example spasmodic torticollis (cervical dystonia) or blepharospasm or writer’s cramp;
• segmental – involves two or more contiguous regions of the body, for example cervical dystonia or writer’s cramp;
• multifocal – involves two or more non-contiguous regions of the body, for example blepharospasm or dystonia in one foot; and
• generalised – involves both legs and at least one other part of the body.

Levodopa may produce considerable amelioration of symptoms in doparesponsivedystonia. Similarly, alcohol, used judiciously, can be very effective in suppressing myoclonus-dystonia. In general, however, dystonia responds poorly to oral medication, although high doses of anticholinergics or benzodiazepines may have beneficial effects in some cases. Botulinum toxin is the treatment of choice for focal dystonia and is widely used for managing patients with blepharospasm, vocal dystonia and spasmodic torticollis, as well as other focal or segmental dystonias.^3,4 However, in some cases tolerance to treatment, mediated through antibodies to botulinum toxin type A or B, may eventually develop.^3,4

n the past, cervical denervation procedures were utilised to manage patients with severe medically refractory spasmodic torticollis, but the long-term benefits appear to be modest.^5,6 Before the advent ofdeep brain stimulation (DBS), thalamotomy had been deployed with some success. However, bilateral thalamotomies were associated with a significant adverse event profile, in particular speech disturbances.⁷ Subsequently, demonstrable efficacy of pallidotomy and globus pallidus internus (GPi) stimulation for dyskinesia, including dystonia, was shown in patients with advanced Parkinson’s disease. GPi stimulation was then introduced for the management of severe, medically refractory dystonia, and is now widely deployed.^8–23

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