Differential diagnosis of Parkinson's disease

Most patients present with clinical clues to guide the neurologist's diagnostic assessment. In many cases, however, the exact diagnosis cannot be made without an autopsy to provide pathology. Only about 80% of parkinsonism cases are correctly diagnosed with idiopathic PD during life. A definite neurodiagnostic test for PD is not yet available. Therefore, the clinical examination, supplemented by tests to rule out other causes, forms the basis of diagnosis. This article discusses differential diagnosis, concentrating on distinguishing clinical characteristics and useful diagnostic tests.