[Deep brain stimulation for Parkinson's disease and dystonia]

Deep brain stimulation (DBS) has proved highly effective in the treatment for Parkinson's disease and dystonia. Presently, many types of dopamine agonists, monoamine oxidase B (MAOB) inhibitors, catechol-O-methyltransferase (COMT) inhibitor or other antiparkinsonian drugs are being developed. However, it is still very difficult to medically treat motor complications associated with levodopa therapy. Surgical intervention using DBS was possible to stimulate the subthalamic nucleus as the treatment of Parkinson's disease. Stimulation of the subthalamic nucleus improves the cardinal parkinsonian symptoms and motor complication associated with levodopa treatment. DBS is a reversible treatment and the original status could be observed by turning off the stimulation. This procedure enables the observation of clinical outcomes or brain mechanisms under both the conditions of turned on and turned off stimulations. On the other hand, dystonia is heterogeneous and refractory and hence, it has been difficult to medically treat it. Since there was no effective treatment available for patients with generalized dystonia, these patients became disabled. However, recently, bilateral pallidal DBS has been shown to markedly improve the conditions of patients with generalized dystonia, and it has proven to be a reliable treatment. There are two characteristic clinical effects of pallidal DBS on dystonia. It improves primary hereditary generalized dystonia, particularly DYT 1, more prominently than secondary dystonia and its beneficial effects are observed over a period of time course. The beneficial effects of pallidal DBS in patients with dystonia are not immediate but progress over weeks to months. The brain mechanism underlying the improvement of pallidal DBS in dystonia has been unclear. Many studies on DBS in Parkinson's disease and dystonia have been carried out to elucidate the clinical outcomes and/or the underlying neurophysiological mechanisms. In this review, the clinical outcomes of DBS for Parkinson's disease and dystonia will be focused on.