Nigral dysfunction in drug-induced parkinsonism: an 18F-dopa PET study

We studied 13 patients with severe drug-induced parkinsonism (DIP) using L-6-[18F]fluorodopa positron emission tomography (18F-dopa PET) to investigate the integrity of their dopaminergic nigrostriatal projections. Twelve of these patients were subsequently followed clinically for a median of 23.5 months (range, 6 to 49). Nine patients had normal putamen 18F-dopa uptake. In eight of these nine patients where follow-up was available, a normal 18F-dopa PET study was predictive of subsequent improvement of parkinsonism. Four of 13 DIP patients (31%) had significantly reduced putamen 18F-dopa uptake, within the Parkinson's disease range, and in three of these four (75%), this reduction was associated with continued, or worsening, parkinsonism. There were no clinical features at the time of PET that distinguished those who recovered and those who did not. We conclude that a normal 18F-dopa PET study correlates well with improvement from DIP, but an abnormal study does not necessarily indicate a poor prognosis.