Abstract
Parkinson's disease (PD) is a multisystem disorder, considered the most common neurodegenerative disease worldwide. Previously, PD was considered a movement disorder in which intellectual abilities have been not affected, but over the past years, there has been an increasing awareness that the clinical spectrum of PD is much broader, also encompassing many non-motor domains. Indeed, recently non-motor symptoms (NMSs) have attracted the attention of researchers because of their negative outcome on PD patients. Moreover, NMS abnormalities are sometimes present before diagnosis and almost inevitably emerge with disease progression. These NMSs include neuropsychiatric abnormalities, sleep disorders, sensory and autonomic dysfunction as well as cognitive dysfunction and dementia among others. NMSs play a tremendously important role and might be useful in the management and sometimes even the diagnosis of PD.