Advances in clinical trials for movement disorders.

In the past several years, there have been several innovations in the design of clinical trials assessing new therapies for patients with movement disorders. These include attempts to address difficulties in conducting clinical trials in treated patients in the advanced stages of their illness, demonstrating disease-modifying effects or a reduction in the development of cumulative disability, and assessing the effects of interventions in patients in the premanifest state of their disease. In addition, there have been advances in clinical trial methodologies and changes in regulatory guidelines that permit the performance of more efficient studies, with a reduction in the cost and duration of the development period. These will be reviewed in the present article.