Differential Diagnosis of Parkinsonism

Parkinsonism refers to a clinical syndrome characterized by a variable combination of tremor, bradykinesia or akinesia, rigidity, and postural instability. In general, two of these four features must be present to make a diagnosis of parkinsonism. However, the situation is complicated by rare cases of pure akinesia in the absence of tremor and rigidity that have the classic pathology of Parkinson’s disease (PD) (1). Within the rubric of parkinsonism there are a myriad of disorders, some yet unclassified (Table 1). The most common cause of parkinsonism is PD. Pathologically, PD is characterized by nigral cell loss and Lewy bodies in the remaining neurons, and the term ‘‘Lewy body parkinsonism’’ is sometimes used synonymously with PD. Some researchers consider it most appropriate to refer to even the pure clinical picture of PD as ‘‘Parkinson’s syndrome’’ on the premise that PD may not be one disease. Whereas the purists demand the presence of Lewy bodies at autopsy to diagnose PD, these inclusions may not be present in some inherited forms of otherwise classical PD. Currently, one such condition, the ‘‘parkin parkinsonism’’ has been mapped to chromosome 6 (2). This autosomal recessive parkinsonism of juvenile onset differs pathologically from sporadic disease in that no Lewy bodies are found in