Parkinson disease-associated cognitive impairment

Parkinson disease (PD) is the second most common neurodegenerative disorder, affects >1% of the population ≥65 years of age and the prevalence is set to double by 2030. In addition to the defining motor symptoms of PD, multiple non-motor symptoms occur and, among them, cognitive impairment is common , important and can potentially occur at any disease stage. Cognitive decline is usually slow and insidious but rapid in some cases. Recently, the focus has been on the early cognitive changes, where executive and visuospatial impairment are typical and can be accompanied by memory impairment, which increasesing the risk for early progression to dementia. Other risk factors for early progression to dementia include visual hallucinations, older age and biomarker changes such as cortical atrophy and Alzheimer-type changes on functional imaging and in cerebrospinal fluid and slowing and frequency variation on EEG. The mechanisms underlying cognitive decline in PD are still unclear. Cortical involvement of Lewy body and Alzheimer-type pathologies are key features, but multiple mechanisms are likely involved. Cholinesterase inhibition is the only high-level evidence-based treatment available, but other pharmacological and non-pharmacological strategies are being tested. Challenges include identification of disease-modifying therapies as well as finding biomarkers to better predict cognitive decline and identify patients at high risk for early and rapid cognitive impairment.