Most patients with Parkinson's disease respond to levodopa, which is, in fact, essential in diagnosis. By contrast, the response to levodopa is not as reliable as a diagnostic tool in other parkinsonian syndromes. For example, only a minority of patients with PSP respond to levodopa temporarily. While most patients with multiple system atrophy have an initial response to levodopa, this response is usually not sustained. Up to 87 percent of patients with DLB respond to levodopa temporarily.