Cognitive and Psychiatric Disturbances in Parkinsonian Syndromes.

Parkinsonian syndromes share clinical signs including akinesia/bradykinesia and rigidity, which are consequences of pathology involving dopaminergic substantia nigra neurons. Yet cognitive and psychiatric disturbances are common, even early in the course of disease. Executive dysfunction is often measurable in newly diagnosed Parkinson's disease. Treatment with dopaminergic medications, particularly dopamine agonists, has been associated with hallucinations and impulse control disorder. Older age, presence of APOE-4 gene, and/or other factors result in amyloid plaque deposition that, in turn, accelerates cortical Lewy body plus tau pathology, linking Dementia with Lewy Bodies and Parkinson's disease with early dementia with Alzheimer's disease. Treatments available for cognitive deficits, depression, and psychotic symptoms are discussed.