Neuroleptic-induced parkinsonism and Parkinson's disease: differential diagnosis and treatment.

Although Parkinson's disease can occur in individuals with psychosis, a patient on antipsychotic medication who develops parkinsonian signs may more readily be diagnosed as and treated for neuroleptic-induced parkinsonism. There are several clinically significant criteria that may aid in proper diagnosis, including clinical course, time and age of onset, nature of tremor, unilaterality of signs, and response to anticholinergic medication. Appropriate diagnosis is essential, as treatment approaches differ for the two disorders. Four case studies are presented to highlight the diagnostic criteria and therapeutic ramifications.