Clinical, laboratory, and in particular neuropathological studies, indicate that parkinsonism is the presenting feature of a range of disorders. Although most are likely to have classic Parkinson’s disease (PD), a substantial number have disorders that include multiple system atrophy (MSA; about 10–15%), progressive supranuclear palsy (PSP), and relatively rare disorders such as dementia with Lewy bodies (DLB) and corticobasal degeneration (CBD). The natural history of these disorders varies widely. Laboratory tests have been used to help differentiate these disorders, but some are not readily accessible, most have been based on patients with established disease, and their sensitivity and specificity, especially in the early stages, are unknown. Clinical pointers therefore, …