The interplay between White Matter Hyperintensities and regional β‐Amyloid on Defaults Mode Network

Abstract

AbstractBackgroundCerebral small vessel ischemic disease (SVID) has been suggested to contribute to the pathogenesis of Alzheimer’s disease (AD). Yet, the mechanistic role of SVID in potentially contributing to AD pathology is unclear. The main objective of this study was to test the hypothesis that axonal SVID influences amyloid β (Aβ) levels within connected default mode network (DMN) tracts and cortical regions in cognitively unimpaired older adults.MethodRegional Standard Uptake Value ratios (SUVr) from Aβ‐PET, and white matter hyperintensity (WMH) volumes from 3D MRI FLAIR images were analyzed across a sample of 72 clinically‐unimpaired (Mini‐Mental State Examination (MMSE) ≥ 26), aged participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI3). The association of WMH volumes in major fiber tracts projecting from cortical DMN regions and Aβ‐PET SUVr in the connected cortical DMN regions were analyzed using linear regression models adjusted for age, sex, ApoE and total brain volumes.ResultThe regression analyses demonstrate that increased WMH volumes in the superior longitudinal fasciculus (SLF) was associated with increased regional SUVr in the inferior parietal lobule (IPL) (p = 0.011).ConclusionThe findings suggest that the relation between Aβ parietal cortex is partially driven by SVID in downstream axonal pathways in pAD. The biological relationships and interplay between Aβ and white matter microstructure alterations that precede overt WMH development across the continuum of AD progression warrants further study.