Background: The etiology and natural history of Parkinson's disease (PD) are not well
understood. Some non-motor symptoms such as hyposmia, rapid eye movement sleep
behavior disorder, and constipation may develop during the prodromal stage of PD and
precede PD diagnosis by years. Objectives: We examined the promise and pitfalls of
research on premotor symptoms of PD and developed priorities and strategies to
understand their clinical and etiological implications. Methods: This review was based on a …