Abstract 367: Physiologic steal in white matter structures of non‐flow limited cerebral hemispheres as evidenced by observations of acetazolamide challenge arterial spin labeling MR

Background Acetazolamide administration can allow for comparisons between cerebral blood flow (CBF) at baseline and after acetazolamide challenge to evaluate the cerebral vasculature. While effects of augmentation have been studied in vaso‐occlusive hemispheres, little has been reported on physiologic, non‐flow limited hemispheres. Methods Patients who underwent acetazolamide challenge MRI from 2014‐2021 and a cerebral angiogram within one year were included. Patients with bilateral disease or non‐diagnostic imaging artifacts were excluded. MRIs were obtained after 1 g of acetazolamide administered 5 and 10 minutes prior to acquisition. Augmentation and steal maps were generated by comparing pre and post acetazolamide CBF images. Regression analysis, Pearson correlation coefficient, two sample t‐Test, Spearman and Mann Whitney U analyses were utilized for statistical evaluation. Results 38 Patients with unilateral cerebral vaso‐occlusive disease underwent the acetazolamide challenge. Steal and T2 hyperintensities were assessed in non‐flow limited hemispheres (NFLH) and flow limited hemispheres (FLH). A moderate correlation was demonstrated between NFLH steal and NFLH T2 hyperintensities (rs=0.48, p=0.0020). A weak correlation without statistical significance was demonstrated between ipsilateral T2 and contralateral T2 hyperintensities (rs= .27, p=.10). No correlation was found between steal severity or T2 hyperintensity and occlusion locations of stenosis. Conclusion Vascular steal phenomenon was demonstrated in the distal cerebral vasculature of cerebral white matter even in the absence of upstream flow limiting stenosis, suggesting an inherit vulnerability of these structures to hemodynamic fluctuations and possible contributing etiology to leukoaraiosis.