Psychotic symptoms are common in Parkinson's disease (PD), generally associated with the medications used to treat the motor symptoms. On rare occasion they occur in patients not taking medication for PD. Psychotic symptoms are usually hallucinations, typically visual, less commonly auditory, and rarely in other domains. Hallucinations are generally stereotyped and without emotional content. Initially patients usually have insight so that the hallucinations are benign in terms of their immediate impact but have poor prognostic implications, with increased risk of dementia, worsened psychotic symptoms and mortality. Delusions occur in about 5-10% of drug treated patients and are considerably more disruptive, being paranoid in nature, often of spousal infidelity or abandonment by family. Treatment of Parkinson's disease psychosis (PDP) focuses on reducing the psychiatric symptom load while balancing the competing problem of mobility. Contributors to the psychotic symptoms should be searched for, such as systemic illness and other psycho-active medications. If none are identified or can be eliminated then the PD medications should be reduced to the lowest levels that allow tolerable motor function. Once this level has been reached there are two schools of thought on treatment, using either acetylcholinesterase inhibitors or atypical anti-psychotics. Only clozapine has level I evidence to support its use. Quetiapine is the only other anti-psychotic free of motor side effects, but it has failed double blind placebo controlled trials to demonstrate efficacy.
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