Differences in glucose metabolism between dementia with Lewy bodies and dementia associated with Parkinson's disease

Objectives: Post-mortem studies of patients with Parkinson's disease with dementia (PDD) and patients with Lewy body dementia (DLB) have shown both cortical Lewy bodies and Alzheimer-type pathology; however, the associated metabolic changes are not well characterized in this population. We performed 3D positron emission tomography (PET) with 18F-2-fluoro-2-desoxyglucose (18F-FDG) to determine the impact of PDD and DLB upon the regional metabolic rate of glucose (CMRglc).

Methods: 18F-FDG was performed in 13 patients with PDD, 15 patients with Parkinson's disease and no dementia (PD), 16 patients with DLB and in 13 healthy control subjects. All groups were matched for age and disease severity. Statistical analyses of between-group metabolic changes were performed.

Results: In comparison to DLB patients, PDD patients exhibited a reduction of occipital CMRglc. PDD patients as compared to controls were characterized by bilateral symmetric hypometabolism in the frontal association, occipital and temporo-parietal cortices, expanding into the posterior cingulum. The group comparison between PDD and PD showed significant symmetric hypometabolic areas within the frontal association, temporo-parietal, and posterior cingulate cortex in PDD. The DLB group, compared to controls, also showed a bilateral symmetric hypometabolism within in the temporo-parietal association and posterior cingulate cortices.

Conclusions: PDD is characterized by a pattern of widespread cortical metabolic changes which resembles AD. Reduced CMRglc within the occipital association cortex occurs in both groups of parkinsonian patients (PD, PDD) and differentiates PDD from DLB