Comment: why do nondopaminergic features in Parkinson disease matter?

Parkinson disease (PD) is a progressive multisystem disorder affecting both dopaminergic and nondopaminergic neurons. Whereas dopaminergic (mainly motor) symptoms are well-defined, the nondopaminergic symptoms (mainly nonmotor, such as depression, cognitive decline, anxiety, apathy, fatigue, sleep disorders, sensory symptoms, postural control deficits, orthostatic hypotension, and urogenital and gastrointestinal symptoms) are frequently missed or neglected during routine clinical visits; consequently, they are underinvestigated and undertreated. The neglect of nondopaminergic symptoms is surprising because i) they occur in almost all patients with PD throughout the course of the disease,(1) and can even precede the occurrence of the classic motor symptoms; ii) they affect almost all aspects of daily life; and iii) have a greater effect on health-related quality of life than dopaminergic symptoms.(2) During the last decade, several initiatives have addressed this deficit with specific assessment procedures for application in clinical practice and research.(1.)