Impact of cognitive dysfunction on drooling in Parkinson's disease.

Background: Parkinson's disease (PD) is commonly characterized by its motor symptoms such as resting tremor, rigidity, bradykinesia and postural instability; however, some of the most debilitating symptoms of this disease are non-motor ones such as dementia and sialorrhea (drooling). Drooling is caused by impaired swallowing and it can have a significant impact on the quality of life. However, it is still unclear whether cognitive dysfunction could exacerbate drooling.