Total and posterior cerebral blood flow is associated with white matter hyperintensity volume and Alzheimer’s‐like patterns of brain atrophy in older adults

Abstract

AbstractBackgroundSmall vessel cerebrovascular disease, often visualized as white matter hyperintensities (WMH) on T2‐weighted MRI scans, contributes to risk, progression, and, possibly, pathogenesis of Alzheimer’s disease (AD). When considered in the context of previous neuroimaging biomarker work in AD, WMH appear to colocalize with other markers of disease risk and progression, including metabolic changes, atrophy, and tau pathology, in areas perfused by the posterior circulation. In the current study, we used a novel MR‐based method, termed phase contrast, to quantitate total cerebral blood flow in anterior and posterior circulations and test its relationship with WMH volume and an AD‐like pattern of brain atrophy in older, community‐dwelling adults.MethodTwo hundred forty‐five older adult participants (77±5.6 mean±SD age, 66% women, 42% Latinx, 30% Black, and 28% White individuals) in the Washington Heights Inwood Columbia Aging Project (WHICAP) received T1‐weighted, T2‐weighted (FLAIR), and phase contrast MR imaging. 2D phase contrast imaging can be used to quantify absolute blood flow rates with cross‐sectional velocity‐encoding of major vasculature leading into the brain. Blood flow rates in the anterior circulation (carotid arteries) and posterior circulation (vertebral arteries) were derived with Medis QFlow 4.0. WMH volume and cortical thickness in AD‐signature regions were derived with in‐house software and FreeSurfer v6.0, respectively. Separate general linear models tested the association of total, anterior, and posterior blood flow rates with WMH volumes and AD‐signature cortical thickness.ResultLower total cerebral blood flow was associated with increased total WMH volume (β = ‐0.14, p<0.05, 95%CI [‐1.37E‐2, ‐7.32E‐4]), an effect that was stronger for posterior flow (β_posterior = ‐0.17, 95%CI [‐3.7E‐2, 2.5E3], β_anterior = ‐0.11, 95%CI [‐1.9E‐2, 5.4E3]). Lower posterior blood flow specifically was associated with lower AD‐signature cortical thickness, but only in older participants (age interaction term: β = ‐3.14, p<0.01, 95%CI [‐2.0E‐4, ‐3.5E‐5]).ConclusionLower total cerebral blood flow, particularly in the posterior circulation, is associated with increased WMH volume and decreased cortical thickness, two neuroimaging markers that are implicated in risk and progression of AD. Future work that examines whether or how diminished total cerebral blood flow accounts for the colocalization of AD biomarkers across modalities will provide insight into the vascular contributions to AD.