PET imaging of the pre-synaptic dopamine uptake sites in rapid-onset dystonia-parkinsonism (RDP)

BACKGROUND: Rapid-onset dystonia-parkinsonism (RDP) is a genetic movement disorder characterized by abrupt onset over hours to days of bradykinesia, postural instability, dysphagia, dysarthria, and severe dystonic spasms with decreased levels of the dopamine metabolite, homovanillic acid (HVA), in cerebrospinal fluid (CSF). METHODS: We imaged the dopamine re-uptake system with [O-methyl-¹¹C]β-CFT ([¹¹C]β-CFT) in three severely affected individuals with RDP and four patients with idiopathic Parkinson's disease (IPD). Results were compared with those of age-matched normal volunteers. RESULTS: Positron emission tomography images from those patients with IPD demonstrated a dramatic reduction in the volume of distribution of [¹¹C]β-CFT whereas patients with RDP showed slightly elevated values. CONCLUSIONS: The data suggest that patients with RDP do not have a decrease in the number of dopamine re-uptake sites. Our findings suggest that, unlike the situation in IPD, low CSF HVA concentrations seen in RDP patients are not the result of degeneration of striatal dopamine terminals or loss of dopamine re-uptake sites.