Anatomy of the Circle of Willis and Blood Flow in the Brain-Feeding Vasculature in Prematurely Born Infants

Background: Previous studies have shown a disrupted development of cerebral blood vessels at term-equivalent age in prematurely born infants. Objective: To assess the anatomy of the circle of Willis in preterm neonates (gestational age 25–31 weeks) at term-equivalent age and to evaluate the relation between anatomic variations and blood flow through the internal carotid arteries (ICAs) and basilar artery (BA). Methods: In 72 preterm neonates, flow measurements (ml/min) were obtained with 2-D phase-contrast magnetic resonance angiography (MRA) at term-equivalent age. Time-of-flight MRA was used to assess the circle of Willis for a dominant A1 segment of the anterior cerebral artery or a fetal-type posterior cerebral artery. Differences in flow were assessed with ANOVA. Results: In our cohort, 53/72 (74%) neonates showed a variant type of the circle of Willis. The flow in the ICA at the side of a dominant A1 segment (43.3 ml/min) was significantly increased compared to the flow in the contralateral ICA (33.0 ml/min; p = 0.009) and tended to be higher than in the ICA in children with a normal anterior anatomy (38.4 ml/min; p = 0.1). The flow in the BA was highest in neonates with a normal configuration of the posterior part of the circle of Willis (32.6 ml/min) compared to children with a unilateral (25.3 ml/min; p = 0.002) or bilateral fetal-type posterior cerebral artery (18.6 ml/min; p < 0.001). Conclusion: Preterm neonates show a high prevalence of variant types of the circle of Willis at term-equivalent age. A relation could be demonstrated between variations in the circle of Willis and the flow in the ICA and BA.