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
