Motor and non-motor features of Parkinson's disease that predict persistent drug-induced Parkinsonism.

Background: Drug-induced Parkinsonism is common, causes significant morbidity, and can be clinically indistinguishable from idiopathic Parkinson's disease. Additionally, drug-induced Parkinsonism may, in some cases, represent "unmasking" of incipient Parkinson's disease. Clinical features or tests that distinguish degenerative from pharmacologic Parkinsonism are needed.