Environmental Causation of Parkinson's Disease

There are three main considerations in the cause of Parkinson's disease (PD)—genetic, environmental, and environmental trigger in genetically predisposed individuals. Literature on the subject is voluminous, but the scientific impact of different studies varies widely. Parkinson syndrome (PS) is diagnosed when two of the three—bradykinesia, rigidity, and resting tremor—are detected. Parkinson's disease, which accounts for a majority of cases,1-5is diagnosed when Lewy body (LB) pathology is noted.6Because the clinical diagnosis of PD may be incorrect in a large proportion,5,7studies based on only clinical assessment include several diverse variants of PS rather than single disease entity. It is reasonable to assume that the cause for all different variants of PS is not the same. For a critical analysis of the literature, the following well-known facts must be taken into consideration: (1) PD is ubiquitous; (2) the mean onset age is approximately 62 years, the frequency