Vascular lesions and brain atrophy in Alzheimer's, vascular and mixed dementia: an optimized 3T MRI protocol reveals distinctive radiological profiles

Background: Vascular lesions may be a common finding also in Alzheimer's dementia, but their role on cognitive status is uncertain. Objective: to investigate their distribution in patients with Alzheimer's, vascular or mixed dementia and detect any distinctive neuroradiological profiles Methods: Seventy-six subjects received a diagnosis of Alzheimer’s (AD=32), vascular (VD=26) and mixed (MD=18) dementia. Three independent raters assessed the brain images acquired with an optimized 3T MRI protocol (including (including 3D FLAIR, T1, SWI and 2D coronal T2 sequences) using semiquantitative scales for vascular lesions (periventricular lesions (PVL), deep white matter lesions (DWML), deep grey matter lesions (DGML), enlarged perivascular spaces (PVS) and microbleeds (MB)) and brain atrophy (medial temporal atrophy (MTA), posterior atrophy (PA), global cortical atrophy-frontal (GCA-F) and Evans’ index). Results: Raters reached a good-to-excellent agreement for all scales (ICC ranging 0.78-0.96). A greater number of PVL (p<0.001), DWML (p<0.001), DGML (p=0.010) and PVS (p=0.001) was observed in VD compared to AD, while MD showed a significant greater number of PVL (p=0.001), DWML (p=0.002), DGML (p=0.018) and deep and juxtacortical MB (p=0.006 and p<0.001, respectively). Comparing VD and MD, VD showed a higher number of PVS in basal ganglia and centrum semiovale (p=0.040), while MD showed more deep and juxtacortical MB (p=0.042 and p=0.022, respectively). No significant difference was observed in scores of cortical atrophy scales and Evans’ index among the three groups. Conclusion: The proposed MRI protocol represents a useful advancement in the diagnostic assessment of patients with cognitive impairment, by more accurately detecting vascular lesions, mainly microbleeds, without significant increase in time and resources expenditure. Our findings confirm that white and grey matter lesions predominate in vascular and mixed dementia, whereas deep and juxtacortical microbleeds predominate in mixed dementia, suggesting that cerebral amyloid angiopathy could be the main underlying pathology.