Psychosis in Parkinson's disease: identification, prevention and treatment.

Psychosis in Parkinson's disease (PD) is a frequent condition affecting >20 % of all PD patients. It is characterized by vivid dreams, nightmares, illusions, delusions and mostly visual hallucinations. Typically psychosis occurs in the late stage of PD, affecting up to 70 % of the patients following a disease duration of 20 years or more, and can severely interfere with the care of the patients, especially if the patients develop delusions. Psychosis is the principal cause of admission to a nursing home for PD patients. Hence, preemptive identification of risk factors, and avoidance and elimination of triggers are most important measures against psychosis in PD patients. Secondarily, pharmaceutical measures are being undertaken successively, including simplification of medication regimes, discontinuation of non-essential CNS-active drugs, ordered reduction of antiparkinsonian drugs, addition of cholesterinase inhibitors in cognitively impaired patients, and finally addition of antipsychotic medication with limited parkinsonian side effects. As psychosis in PD is a frequent and important problem, we set out to write a state-of-the-art guideline for its identification and treatment.