Rehabilitation for non-motor symptoms for patients with Parkinson's disease from an α-synuclein perspective: a narrative review.

Parkinson's disease (PD) is a common neurodegenerative disorder affecting aged population around the world. PD is characterized by neuronal Lewy bodies present in the substantia nigra of the midbrain and the loss of dopaminergic neurons with various motor and non-motor symptoms associated with the disease. The protein α-synuclein has been extensively studied for its contribution to PD pathology, as α-synuclein aggregates form the major component of Lewy bodies, a hallmark of PD. In this narrative review, the authors first focus on a brief explanation of α-synuclein aggregation and circumstances under which aggregation can occur, then present a hypothesis for PD pathogenesis in the peripheral nervous system (PNS) and how PD can spread to the central nervous system from the PNS via the transport of α-synuclein aggregates. This article presents arguments both for and against this hypothesis. It also presents various non-pharmacological rehabilitation approaches and management techniques for both motor and non-motor symptoms of PD and the related pathology. This review seeks to examine a possible hypothesis of PD pathogenesis and points to a new research direction focus on rehabilitation therapy for patients with PD. As various non-motor symptoms of PD appear to occur earlier than motor symptoms, more focus on the treatment of non-motor symptoms as well as a better understanding of the biochemical mechanisms behind those non-motor symptoms may lead to better long-term outcomes for patients with PD.