Clinical trials: past, current, and future for atypical Parkinsonian syndromes.

There are currently no effective Food and Drug Administration-approved treatments for atypical parkinsonian disorders such as progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies, or multiple system atrophy. Previous treatment trials for these disorders were focused on symptomatic support and did not affect disease progression. Recent breakthroughs in neuropathology and pathophysiology have allowed a new understanding of these disorders and investigation into potentially disease modifying therapies. Randomized, placebo-controlled clinical trials of these disorders will be reviewed here. Suggestions for future therapeutic targets and clinical trial design (with a focus on progressive supranuclear palsy) will also be provided.