Non-Motor Symptoms: The Hidden Face of Parkinson's Disease.

Non-motor symptoms (NMSs) of Parkinson's disease (PD) were recognized by James Parkinson himself about 200 years ago and are now considered to be an integral part of PD, significantly contributing to the deterioration of patients' quality of life. Although awareness of NMSs is growing, and several scientific societies now have dedicated non-motor study groups, the NMS burden is still the hidden face of PD and in most cases, clinicians' views are focused on the motor symptoms alone. The literature was reviewed using several databases and scientific journals; this review provides a comprehensive description of the most common NMSs in PD, their clinical phenotype, social impact, diagnosis, and therapeutic management. Early recognition of these features may lead to more prompt and effective treatment and may help to better understand patients' needs.