Cognitive impairment and dementia in parkinson’s disease

Cognitive decline is common in Par-kinson’s disease (PD) and is a leading cause of reduced quality of life. Cognitive difficulty seen early in the course of PD takes the form of mild cognitive impairment (MCI-PD), and Parkinson’s disease dementia (PDD) is nearly uni-versal in the late stages of the disease. Although most people with MCI-PD will progress to PDD, the two entities have significant differences in terms of under-lying pathophysiology as well as cognitive profiles and management strate-gies. The most important contributor to MCI-PD is frontostriatal dopamine depletion, whereas the major cause of PDD is Lewy body pathology spread-ing to the neocortex plus, in many cases, comorbid Alzheimer’s pathology. Management strategies for both MCI-PD and PDD are limited. The best approach for MCI-PD is a combination of cognitive rehabilitation and appropriate titration of dopaminergic therapy, and the medications used in treatment of Alzheimer’s disease appear to have a modest benefit for patients with PDD.