Brain MRI diffusion abnormalities associated with arteriolosclerosis pathology

Abstract

AbstractBackgroundBrain arteriolosclerosis is one of the main pathologies of cerebral small vessel disease. It involves the thickening of the vessel wall and stenosis of arterioles causing lower cognitive and motor function, and higher odds of dementia. This work intends to explore the independent association of brain arteriolosclerosis with diffusion abnormalities in the white matter (WM) of community‐based older adults.MethodParticipants comprised community‐dwelling older adults (N = 175) from four studies of aging (Rush Memory and Aging Project, Religious Orders Study, Minority Aging Research Study, and Clinical Core of the Rush Alzheimer’s Disease Research Center) (Fig.1A). Whole brain 3D T1w MPRAGE, T2w FLAIR, and diffusion‐weighted MRI (2×2×2mm3, b = 1,000s/mm2 for 40 diffusion gradient directions, and 6 b = 0s/mm2 volumes) data were acquired in‐vivo using 3T MRI scanners. The fractional anisotropy (FA) and trace maps were transformed to the space of the IIT Human Brain Atlas v.5.0 and projected onto the WM skeleton of the IIT atlas. Following a participant’s death, the extracted brain underwent a detailed evaluation by a neuropathologist. Assessed neuropathologies included arteriolosclerosis, Alzheimer’s pathology, LATE‐NC, gross and microscopic infarcts, atherosclerosis, and cerebral amyloid angiopathy (Fig.1B).Linear regression was used in voxels of the WM skeleton to test the association of FA or trace with the severity of arteriolosclerosis controlling for all other neuropathologies, white matter hyperintensities (WMH), demographic variables (age at scan, sex, years of education), antemortem interval to imaging, and scanner. The statistical analyses were carried out using FSL’s PALM tool with 5,000 permutations and threshold‐free cluster enhancement. The significance level was set at p<0.05, after family‐wise error rate (FWER) correction for multiple testing.ResultArteriolosclerosis score was associated with lower FA (Fig.2) and higher trace (Fig.3) of the diffusion tensor throughout the brain in multiple WM regions, even in areas typically free of WMH. Other neuropathologies or the effects of WMH on diffusion characteristics had no impact on these relationships.ConclusionThe current study showed that, regardless of the impact of other neuropathologies or visible WMH, brain arteriolosclerosis in older persons is associated with diffusion abnormalities that extend throughout the WM.