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Monosymptomatic resting tremor and Parkinson's disease: A multitracer positron emission tomographic study



We sought to elucidate the relationship between monosymptomatic resting tremor (mRT) and Parkinson's disease (PD). We studied eight mRT patients (mean Hoehn and Yahr [H&Y], 1.1 ± 0.4), eight patients with PD (mean H&Y, 1.5 ± 0.8), who showed all three classic parkinsonian symptoms, and seven age-matched healthy subjects. Subjects underwent cerebral magnetic resonance imaging (MRI) and multitracer positron emission tomography (PET) with 6-[18F]fluoro-L-dopa (F-dopa), [18F]fluorodeoxyglucose (FDG), and [11C]raclopride (RACLO). PD and mRT patients did not show significant differences in F-dopa-, RACLO-, or FDG-PET scans. In F-dopa- and RACLO-PET, significant differences between the pooled patient data and control subjects were found for the following regions: anterior and posterior putamen ipsilateral and contralateral to the more affected body side, and ipsilateral and contralateral putaminal gradients of the Ki values. Furthermore, we found a difference for the normalized glucose values of the whole cerebellum between the control group (0.94 ± 0.06) and PD patients (1.01 ± 0.04; P < 0.05) but not for the mRT group (0.97 ± 0.03). Our findings indicate that monosymptomatic resting tremor represents a phenotype of Parkinson's disease, with a nearly identical striatal dopaminergic deficit and postsynaptic D2-receptor upregulation in both patient groups. We suggest that the cerebellar metabolic hyperactivity in PD is closer related to akinesia and rigidity rather than to tremor. © 2002 Movement Disorder Society