White matter injury in the preterm neonate: the role of perfusion

The preterm infant is at special risk of white matter injury. It was hypothesized long ago that ischemia is the principal etiology. The commonly used experimental animals for perinatal brain injury research may differ importantly from humans as regards the white matter. Therefore, evidence from human neonates that the white matter is selectively exposed to ischemia is relevant. Blood flow to the white matter appears to be particularly low in the premature human infant, with only 17% of flow to the gray matter. Furthermore, the blood flow to the white matter appears to be selectively reduced when blood pressure is low. There are important methodological limitations to all the studies reviewed; whereas the hypothesis has not had strong support, it has not been refuted. It appears wise to consider ischemia to the white matter a real threat in sick preterm infants.