Abstract WP400: Magnetic Resonance-Derived Oxygen Extraction Fraction in White Matter Hyperintensities Compared to Normal Appearing White Matter

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Introduction: White matter hyperintensities (WMH), a common neuroradiological feature seen with aging, increases the risk of stroke, dementia, disability and mortality. The underlying pathophysiology leading to WMH is incompletely understood. Here, we examined the role of regional cerebral blood flow (CBF) and oxygen extraction fraction (OEF) in WMH.Methods: Subjects with WMH (n=9) and age-matched controls (n=9) were imaged in a 3T MRI Scanner. OEF was obtained using an asymmetric spin echo sequence while CBF was obtained with pseudo-continuous arterial spin labeling. WMH were graded according to Fazekas et al. For tissue-type quantification, CBF and OEF images were segmented to classify whole brain (WB), gray matter (GM), white matter (WM), white matter hyperintensities (WMH), and normal appearing white matter (NAWM).Results: CBF and OEF in WB, GM and WM did not differ between cohorts. However, differences emerged when comparing the WMH and NAWM segmented tissues. Specifically, CBF in WMH was less than half that seen in NAWM in the WMH group, and similarly lower than normal WM in controls. Moreover, OEF in WMH was higher compared to NAWM and WM in controls, but this did not reach statistical significance (Table).Conclusions: CBF and OEF did not differ between subjects with or without WMH. However, within the WMH group, regions of WMH had significantly lower but not absent CBF and trends towards higher OEF compared to NAWM and normal WM in controls. These data suggest that regions of WMH do not represent irreversibly infarcted tissue, but rather, may be viable tissue under chronic metabolic stress. Increased OEF in WMH may be a marker of salvageable brain tissue; However, additional work is needed to confirm these results.

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