Milestones in movement disorders clinical trials: advances and landmark studies

Over the past 25 years clinical trials testing in movement disorders has evolved in order to more effectively and efficiently analyze the safety and efficacy of new interventions. Studies today regularly incorporate methods to decrease placebo and bias effects and to ensure more rigorous statistical analyses. Newer, standardized, and validated rating scales such as the Unified Parkinson's Disease Rating Scale and the Unified Huntington's Disease Rating Scale are routinely employed in an effort to produce results that are comparable across different sites and studies. Several landmark studies in movement disorder research highlight these and other prominent procedural advances. The Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism trial pioneered the use of functional clinical end points, utilized a 2 × 2 factorial design to more efficiently analyze multiple interventions, and employed a washout design to assist in sorting putative neuroprotective from symptomatic effects. PRECEPT included neuroimaging as an outcome measure and highlighted the importance of futility studies in more efficiently directing resources. TEMPO and ADAGIO introduced the use of delayed-start (or 2-period) trials to try to identify disease-modifying interventions. NET-PD used futility studies to streamline the evaluation of potentially valuable treatments, followed by a large, long-term simple study design to assess the clinical significance of a new intervention. There have also been advances in clinical trials testing new surgical interventions, with the introduction of blinded outcome assessments and sham-surgery control groups. Collectively, methodological advances in clinical trials have permitted the safety and efficacy of new interventions to be tested more efficiently and economically and with a higher level of certainty that the potential benefits and adverse effects of interventions recommended for general use are well understood.