Mild cognitive impairment in drug-naive patients with PD is associated with cerebral hypometabolism.

Objective: To characterize brain metabolic changes associated with mild cognitive impairment (MCI) in drug-naive patients with Parkinson disease (PD) using (18)F-fluorodeoxyglucose (FDG) and PET (FDG-PET).

Methods: This cross-sectional study included newly diagnosed patients with PD with MCI in single or multiple domain (PD-MCI; n =12) and without MCI (PD-nMCI; n =12), and healthy controls (n =12). The groups were matched for age. Moreover, the patient groups were matched for motor disability. All subjects underwent a FDG-PET study. Cerebral regional relative metabolic maps were compared in PD-MCI, PD-nMCI, and controls using regions of interest analysis (ROIs) and voxel-based analysis with statistical parametric mapping.

Results: ROIs and voxel-based analyses revealed significant relative hypometabolism in the prefrontal, superior/inferior parietal, and associative occipital cortices as well as in the striatum in patients with PD-MCI relative to controls (p < 0.05) and to a lesser extent in patients with PD-nMCI. In contrast, patients with PD-nMCI did not show significant metabolic changes as compared to controls.

Conclusion: MCI in patients with PD is associated with cortical hypometabolism since the earliest stage, independent of therapy or motor disability. The early involvement of posterior cortical region, a pattern shared by advanced stages of PD-MCI and PD with dementia, could represent an early marker of dementia. The relevance of this pattern in predicting prodromal dementia has to be evaluated in longitudinal studies.