Pathophysiology of Non-Motor Signs in Parkinson’s Disease: Some Recent Updating with Brief Presentation

Parkinson’s disease (PD) is a progressive neurodegenerative disorder affecting 1% of the population above sixty years. It is caused by an interaction between genetic and environmental risk factors. Loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) is pathologically characterizing the disease and responsible for the cardinal motor symptoms, most notably, bradykinesia, rest tremors, rigidity, and loss of postural reflexes. Non-motor signs such as olfactory deficits, cognitive impairment, sleep behavior disorders, and gastrointestinal disturbances are reflecting disturbances in the non-dopaminergic system. They precede dopaminergic neuronal degenerations by 5–10 years and are considered the main contributors to patients’ disability, particularly after the successful implementation of levodopa (L-dopa) treatment of motor symptoms. The present general review aimed to briefly update non-motor signs and their underlying pathophysiology in PD.