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.