Psychotic symptoms in Parkinson's disease: pathophysiology and management

Parkinson's disease (PD) is a chronic neurodegenerative disease, in which mainly dopaminergic neurons in the substantia nigra in the brain degenerate, leading to a depletion of dopamine (DA) in the striatum. The most important motor disturbances of the disease are bradykinesia (slowing down of movement), hypokinesia (poverty of movement), rigidity (muscle stiffness), tremor and postural instability. Besides these well-known motor symptoms, non-motor symptoms may develop, such as depression, cognitive impairment and psychosis. Psychotic symptoms constitute a relatively common but nevertheless serious complication, with visual hallucinations and paranoid delusions often being most prominent. These symptoms are important contributors to patient and caregiver distress and are often important risk factors for nursing home placement. Exogenous (related to therapeutic interventions) factors are of major importance but endogenous (related to the disease process itself) factors might also contribute to the development of psychotic symptoms in PD. Therapeutic strategies comprise reduction of antiparkinsonian treatment, cholinesterase inhibitors and atypical antipsychotics. As psychotic symptoms in PD are often influenced by both endogenous and exogenous factors, a combination of strategies may be chosen.