Traditionally, a Parkinsonian syndrome is diagnosed clinically when two of the following are present:

These signs are present in Parkinsonism associated with a loss of dopaminergic nerve terminals (presynaptic Parkinsonian syndrome), such as that encountered in Parkinson's disease, multiple system atrophy, and progressive supranuclear palsy. However these signs also present in forms of Parkinsonism that do not involve nigrostriatal degeneration, such as those secondary to vascular, toxic, and inflammatory processes, involving the striatum or that are drug induced. The fact that tremor occurs in other conditions, such as essential tremor, can also lead to difficulties in diagnosis, especially in early phases of the disease.[1]