Apomorphine test in de novo Parkinson's disease.

We administered apomorphine, a powerful dopaminergic agonist, subcutaneously to 25 untreated patients with parkinsonian features and evaluated motor response with the aim of discriminating idiopathic Parkinson's disease (IPD) from multiple system atrophy and progressive supranuclear palsy. The response to apomorphine was strongly predictive of responsiveness to subsequent levodopa follow-up and of the final diagnosis, made on the basis of both clinical and instrumental evaluation. Our data confirm that the apomorphine test is helpful in the differential diagnosis of IPD.