Deep Brain Stimulation for Dystonia

Dystonia refers to movement disorders characterized by sustained muscle contractions that produce abnormal postures, twisting movements, and other abnormal involuntary movements. A spectrum of etiologies underlies the various dystonia syndromes, ranging from genetic conditions to brain injury. First-line therapy for dystonia consists of pharmacologic agents of several classes and, particularly for focal dystonia, chemodenervation therapy with botulinum toxin. Many patients with dystonia realize an inadequate response to those treatments, and for such patients whose symptoms are sufficiently troublesome, surgical treatment can be used to reduce symptoms and improve function. Previously, the ablative procedures of thalamotomy and pallidotomy were used, in which a permanent destructive lesion was made in the motor territory of the thalamus or the globus pallidus. More recently, the device-based therapy of deep brain stimulation (DBS) has emerged as the preferred surgical treatment for dystonia and other movement disorders for most patients who require operative intervention. DBS uses a surgically implanted brain lead connected to an implanted neurostimulator to deliver chronic, high- frequency electrical stimulation to one of several deep nuclei. 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 safe manner. Use of DBS to treat dystonia is a rapidly evolving area, and preliminary evidence suggests that primary dystonia linked to genetic mutation, other primary dystonias, and tardive dystonic syndromes respond most dramatically to treatment with DBS, whereas secondary dystonia tends to be less responsive.