Clinical and [123I]FP-CIT SPET imaging follow-up in patients with drug-induced parkinsonism

We recently found that patients with drug-induced parkinsonism (DIP) may have normal (group I) or abnormal (group II) putamen [123I]FP-CIT DAT (dopamine transporter) binding. In this study we reassessed clinical features and DAT binding in 19 of the original 32 patients (10 of group I and 9 of group II) after a 19–39-month follow-up period and tested the effects of chronic levodopa treatment in both cohorts of patients. In group I patients, [123I]FP-CIT SPET (single photon emission tomography) was still normal in all patients at follow-up; DAT binding and UPDRS (Unified Parkinson’s Disease Rating Scale) motor score values did not differ from baseline. In group II patients, [123I]FP-CIT SPET was still abnormal at follow-up; putamen DAT binding was significantly reduced and UPDRS III score higher compared to baseline. Levodopa treatment improved motor symptoms in three out of ten patients of group I and in eight out of nine patients of group II. No adverse psychiatric effects were observed in any of the patients. This study shows that DAT binding imaging may help to identify subjects with DIP secondary to a loss of dopamine nerve terminals in the context of a progressive degenerative parkinsonism. Patients with DIP may benefit from levodopa therapy, particularly when dopamine nerve terminal defects are present, and this should be considered in the therapeutic management of these patients.