LAUSR

Background: Children with sickle cell anemia (SCA) invoke compensatory mechanisms to meet cerebral oxygen demand in the setting of low oxygen carrying capacity. Whereas cerebral blood flow (CBF) is largely regulated by cerebral arterioles as one compensatory mechanism, we sought to determine if the cross-sectional area of the large in-flow arteries was also increased. Methods: Children and young adults with SCA underwent 3 Tesla magnetic resonance angiography (MRA) and imaging (MRI) with pseudocontinuous arterial spin labeling (pCASL) and asymmetric spin echo sequence to measure CBF and oxygen extraction fraction (OEF) respectively. Using the double oblique method, we measured artery diameters and calculated the area (A) of the vessel as A=πr 2 . The total inflow area (A T-inflow ) was the summation of the areas of distal portions of both internal carotid arteries and basilar artery. CBF, OEF, arterial oxygen content [(CaO 2 ) = 1.36*Hemoglobin*%saturation on pulse oximetry] and A T-inflow were compared between groups with nonparametric statistics. Spearman’s correlation determined relationship of A T-inflow with other variables. Results: Data was available for 29 subjects with SCA (median age 15 years (range 9-26), 45% male) and 17 age-matched controls (15y (range 9-18), 47% male) underwent scanning. Children with SCA had larger A T-inflow (36 [29, 40] mm 2 ) compared to age-matched controls (29 [26, 31] mm 2 , p=0.01). CBF and OEF were higher (p=0.001, p=0.002), and CaO 2 was lower (p<0.001) in SCA compared to controls. A T-inflow positively correlated with CBF (p=0.002) and OEF (p<0.001), and negatively correlated with CaO 2 (p=0.02; Figure ). Conclusion: Increased cross sectional area of large cerebral arteries may provide an additional compensatory mechanism in SCA to augment CBF and aid in meeting cerebral oxygen demand. Further work is needed to determine if MRA measurements provide a non-invasive precursor to increased cerebral metabolic stress and stroke risk.