The metabolic anatomy of Parkinson's disease: Complementary [18F]fluorodeoxyglucose and [18F]fluorodopa positron emission tomographic studies

Abstract

We studied the metabolic anatomy of typical Parkinson's disease (PD) using [¹⁸F]fluorodeoxyglucose (FDG) and [¹⁸F]fluorodopa (FDOPA) and positron emission tomography (PET). Fourteen PD patients (mean age 49 years) had FDG/PET scans, of which 11 were scanned with both FDOPA and FDG. After the injection of FDOPA, brain uptake and arterial plasma radioactivity were monitored for 2 h. Striatal FDOPA uptake was analyzed with regard to a two-compartment model, and target-to-background ratios (TBRs) and TBR-versus-time slopes were also calculated. Regional patterns of metabolic covariation were extracted from FDG/PET data using the Scaled Subprofile Model (SSM). SSM pattern weights, FDOPA uptake constants (K_i), TBRs, and TBR slopes were correlated with clinical measures for bradykinesia, rigidity, tremor, gait disturbance, left-right asymmetry, dementia, and overall disease severity. In PD patients, rate constants for FDOPA uptake correlated with individual measures of bradykinesia (p = 0.001) and gait disability (p < 0.05). SSM analysis revealed a distinct pattern of regional metabolic asymmetries, which correlated with motor asymmetries (p < 0.001) and left-right differences in K_i (p < 0.01). Our data suggest that in PD patients, FDG/PET and FDOPA/PET may provide unique and complementary information about underlying disease processes.