Microstructural white matter alterations in dementia with lewy bodies and Alzheimer's disease: a diffusion tensor imaging and neurite orientation dispersion and density imaging study.

Background: Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) are common types of dementia, however, diagnosis is challenging. An innovative MR method called neurite orientation dispersion and density imaging (NODDI) is used to assess different microstructural alterations between the conditions. Objective: To assess microstructural white matter (WM) changes in DLB and AD using NODDI. Methods: Diffusion images were acquired from 26 DLB patients, 36 AD patients, and 37 normal controls (NCs). The diffusion tensor imaging (DTI) was used to generate fractional anisotropy (FA), mean diffusivity (MD), and NODDI was used to generate neurite density index (NDI), orientation dispersion index (ODI), and volume fraction of isotropic water molecules (Viso), these parameters were compared among groups applying Tract-based spatial statistics (TBSS). We also analyzed the correlations between altered parameters and cognitive scores and investigated the diagnostic efficacy of different parameters using k-nearest neighbor (KNN). Results: Compared with NC, FA, ODI, and NDI significantly decreased, while MD and Viso significantly increased in both DLB and AD. Compared with DLB, ODI and NDI significantly decreased in AD. The diffusion parameters of multiple fibers were strongly correlated with cognition. NDI exhibited a relatively larger AUC value in differentiating between groups. Conclusion: Widespread disruption of white matter microstructure is evident in both DLB and AD, with differences in these alterations between the two conditions. NDI holds promise as a neuroimaging biomarker for distinguishing DLB from AD.