[Deep brain stimulation in the treatment of dystonia]

Dystonia refers to movement disorders characterized by sustained muscle contractions that produce abnormal postures and twisting movements. First-line therapy for dystonia includes several classes of pharmacologic agents. Botulinum toxin injections are the treatment of choice for several forms of focal dystonia. Many patients with dystonia do not benefit from these treatments, and for those patients whose symptoms are sufficiently troublesome, surgical treatment can be used to reduce symptoms and to improve function. Formerly the ablative procedures of thalamotomy and pallidotomy were used. More recently, deep brain stimulation (DBS) has emerged not only as the preferred surgical treatment for advanced idiopathic form of Parkinson's disease and severe forms of essential tremor but also for dystonia. For dystonia, stimulation directed at the globus pallidus internus has been the most thoroughly studied to date. Advantages of DBS include its relatively non-destructive nature, its adjustability and reversibility, and its capacity to be used bilaterally in a single surgical session. Use of DBS to treat dystonia is a rapidly evolving area, and preliminary evidence suggests that primary dystonia linked to genetic mutation, especially DYT-1 positive generalized dystonia, and other primary dystonias respond most dramatically to treatment with DBS, whereas secondary dystonia tends to be less responsive.