The differential diagnosis of Parkinson's disease.

The diagnosis of Parkinson's disease continues to be challenging with misdiagnosis rates as high as 20-30% in early stages. Such diagnostic inaccuracy is largely due to failure to recognize atypical parkinsonian disorders including multiple system atrophy (MSA), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and dementia with Lewy bodies (DLB). These disorders are characterized by distinctive sets of atypical features that have been incorporated into recent consensus diagnostic criteria. Early diagnosis of atypical parkinsonian disorders is important not only because of prognostic implications, but also because of variable therapeutic targets such as autonomic failure, apraxia or dementia.