Non-motor symptoms of Parkinson's disease from pathophysiology to early diagnosis

Parkinson's disease is the second most common neurodegenerative disease after Alzheimer's disease. The pathophysiology of Parkinson's disease is complex and imperfectly known. Primum movens is abnormal intra-neuronal accumulation of the protein alpha-synuclein, leading to metabolic disturbances and neurodegeneration. This abnormal accumulation of alpha-synuclein is also found in dementia with Lewy bodies and multiple system atrophy, which together with Parkinson's disease form the group of alpha-synucleinopathies. Well known by its motor signs (bradykinesia, rest tremor, cogwheel rigidity and gait disturbance), Parkinson's disease is above all a systemic disease composed of a myriad of non-motor symptoms (constipation, sense of smell disorders, rapid eye movement sleep behaviour disorders, genitourinary disorders...). These non-motor symptoms caused by accumulation and migration of alpha-synuclein deposits from the gut and the olfactory bulb to the central nervous system may precede motor signs by ten years and therefore be of interest for early diagnosis. Furthermore, non-motor symptoms have a poorer impact on quality of life than motor signs themselves. Therefore, understanding, recognition and management of non-motor symptoms are crucial in management of parkinsonian patient. In this paper, we offer an update on the main non-motor symptoms of Parkinson's disease, from their pathophysiology to their screening, ending with their management. (C) 2020 Societe nationale francaise de medecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.