Changes of metabolic connectivity in dementia with Lewy bodies with visual hallucinations: a 18F-FDG PET/MR study

BACKGROUND: Recurrent complex visual hallucinations (VH) are common in dementia with Lewy bodies (DLB). Previous investigations suggest that VH are associated with connectivity changes within and between large scale networks involved in visual processing and attention.AIM: To examine more directly whether VH in DLB reflects direct changes in neuronal activity between cortical regions assessing metabolic connectivity with 18F-FDG-PET/MRI and graph theory.METHODS: Twenty-six patients with probable DLB (13VH and 13 no-VH; mean age: 72.9±6.87 years versus 70.2±7.96 years) were enrolled. T1-weighted 3T-MRI images and FDG-PET data were co-acquired using an integrated PET/MR scanner. MRI images defined cortical parcels of the Shaefer-Yeo atlas for multiple functional networks. We computed in each parcel the regional standardized-uptake-values (SUVr) corrected for partial volume and normalized to the cerebellar cortex. We then computed using graph analysis strength degree, clustering coefficient, characteristic path length, and hubs.RESULTS: The mean 18F-FDG-PET SUVr values of parcels belonging to the visual and dorsal attention networks were significantly lower in the VH group (p=0.01). Metabolism in the right temporoparietal cortex correlated with VH severity (R=-0.58; p<0.01). VH patients showed weaker metabolic connectivity in the parietal, temporal, and occipital cortex of the default, dorsal attention, and visual networks, but more robust connectivity in the right insula and orbitofrontal cortex. A lower global efficiency characterized the VH group, except for ventral attention and limbic networks.CONCLUSIONS: VH in DLB correlate with lower glucose metabolism ad weaker metabolic connectivity in the parietal-occipital cortex, but stronger connectivity in the limbic system.