Neuroimaging biomarkers in prodromal DLB

AbstractBackgroundPatients with dementia with Lewy bodies (DLB) are characterized by hypometabolism in the parieto‐occipital cortex and the cingulate island sign on F18‐fluorodeoxyglucose (FDG) PET, lower medial temporal F18‐Flortaucipir uptake on tau PET, and lower volumes of the basal forebrain gray matter nuclei on MRI. Whether this pattern of imaging findings is present as early as the prodromal stage of DLB is unknown. We investigated the pattern of hypometabolism, atrophy, and Flortaucipir uptake in patients with mild cognitive impairment (MCI) who progressed to DLB and compared them to MCI patients who progressed to Alzheimer’s disease dementia (ADdem).MethodPatients with MCI who underwent FDG PET (n=17), Flortaucipir PET (n=9) and MRI (n=28) at baseline and progressed to probable DLB were included. We also included a cognitively unimpaired cohort of controls and MCI patients who progressed to probable ADdem (MCI‐AD) for comparison. Voxel‐base analysis on SPM12 and region‐based analysis were performed to compare the clinical groups.ResultPatients with MCI‐DLB had profound hypometabolism in the parieto‐occipital region extending into the temporal lobes, substantia nigra and thalamus. When compared to MCI‐AD, the hippocampal and posterior cingulate metabolism were relatively preserved in patients with MCI‐DLB, accompanied by greater hypometabolism in the substantia nigra in MCI‐DLB than MCI‐AD. MCI‐DLB patients were also characterized by greater atrophy in the substantia innominata (nucleus basalis of Meynert and the diagonal band) on MRI. F‐18 Flortaucipir uptake in MCI‐DLB was comparable to the control group, but significantly lower than MCI‐AD particularly in the medial temporal lobes.ConclusionImaging biomarkers can identify neurodegenerative changes associated with the prodromal phase of DLB. Prodromal DLB patients are characterized by greater atrophy in basal forebrain nuclei, suggesting that the degeneration of the cholinergic system occur as early as the prodromal stage in DLB. Preservation of medial temporal metabolism, the cingulate island sign, and substantia nigra hypometabolism on FDG PET and lower medial temporal F18‐ Flortaucipir uptake can be used to distinguish prodromal DLB and prodromal ADdem.