Clinical milestones in Parkinson's disease: Past, present, and future

Clinical disease milestones (literally a stone functioning as a milepost in ancient Rome; in medical sciences, a significant event or stage in disease progression) are clinically relevant endpoints expressing a major disease-related event [1]. Within the world of Parkinson's disease (PD), disease milestones are clinical indicators of disease stage and prognosis, essential to evaluate disease progression [2,3]. Over the last few decades, the focus of these endpoints has expanded from motor manifestations to include non-motor endpoints and functionality, congruent with our appreciation of the breadth of the disease and its impact on patients.