Longitudinal free‐water changes in dementia with Lewy bodies

Abstract

AbstractBackgroundDiffusion‐weighted MRI (dMRI) examines tissue microstructure integrity and white matter pathways in vivo. Prior dementia with Lewy bodies (DLB) studies focused on white matter or voxel‐based techniques. Less is known about longitudinal white and grey matter microstructural changes in DLB. We aimed to characterize longitudinal diffusion microstructural changes in individuals with DLB.MethoddMRI scans were collected on individuals with DLB from the Mayo Clinic Longitudinal Imaging Biomarkers of DLB Program. Demographics, clinical evaluations and MRI were collected at baseline, and 12‐ or 24‐months. Free water (FW) and FW‐corrected fractional anisotropy (FAT) were analyzed in grey and white matter using 122 bilateral template regions and tracts of interest from the Mayo Clinic Adult Lifespan Template. Primary outcomes were differences in FW and FAT between baseline and 12‐ or 24‐months.ResultWe identified 23 individuals with DLB or mild cognitive impairment with Lewy bodies (MCI‐LB) from baseline to 12‐months [mean age 69.3 years (SD 9.5); 95.8% male], and 16 individuals from baseline to 24‐months [mean age 67.5 years (SD 9.3); 100% male]. Participants at both time‐points showed worsening in Montreal Cognitive Assessment and Movement Disorders Society Unified Parkinson’s Disease Rating Scale motor scores (p<0.05). We found significant differences in FW, but not FAT, from baseline to 12‐months. Significant increases in FW at both time‐points compared to baseline were observed in the insula, putamen, parahippocampal, and rolandic operculum regions (pfdr<0.05). We found additional more widespread microstructural changes from baseline to 24‐months, with increased FW in the amygdala, entorhinal, mid and posterior cingulum, inferior frontal, hippocampal, pallidum, precuneus and retrosplenial regions (pfdr<0.05). We found decreased FAT from baseline to 24‐months in the cerebellar and superior occipital regions (pfdr<0.01).ConclusionLonger follow‐up at 24‐months identified broader networks of free water changes in individuals with DLB. Results support dMRI as a promising, non‐invasive tool to track disease progression in DLB. More investigation is needed to evaluate the relationship of microstructural changes with clinical progression in DLB.