Longitudinal study of cognitive and cerebral metabolic changes in Parkinson's disease.

OBJECTIVE To investigate the cortical metabolic alterations that precedes longitudinal cognitive decline in Parkinson's disease (PD). METHODS We analyzed the data of 46 PD patients who did not have dementia at baseline and completed 3-year follow-up. Based on the results of general cognitive, memory and visuospatial tests, patients were classified into cognitively normal PD (PD-CogNL), PD with mild cognitive impairment (PD-MCI), and PD dementia (PDD). The regional cerebral glucose metabolism at rest was measured using 18F-fluorodeoxyglucose positron emission tomography. Voxel-wise effect size analyses were performed to delineate abnormal metabolic patterns associated with changes in cognitive status in PD. RESULTS At baseline, 29 patients had PD-CogNL, and 17 patients had PD-MCI. At follow-up, 28 patients had PD-CogNL, 12 patients had PD-MCI, and 6 patients developed PDD. Seventeen of 29 PD-CogNL patients remained to be PD-CogNL, and 9 PD-CogNL patients converted to PD-MCI. Eleven PD-MCI patients reverted to normal cognition during follow-up. 3 PD-CogNL and 3 PD-MCI patients developed PDD. Cognitively stable PD-CogNL group had frontal predominant hypometabolism. PDD converters showed parieto-occipital hypometabolism at baseline regardless of whether a patient's initial cognitive status is PD-CogNL or PD-MCI. CONCLUSIONS Parieto-occipital hypometabolism is a good predictor of early dementia conversion in PD.