Ischaemia of the preterm brain.

Much has been learned about the diagnosis and prognosis of periventricalar leucomalacia during the past 10 years. The understanding of its causation, however, has not advanced much. Still, the candidate for the principal role is focal ischaemia in the particularly vulnerable regions of the brain. It has been difficult to provide direct supportive evidence for this hypothesis. It has not been possible to define a threshold for (global) cerebral blood flow (CBF) under which brain damage or electrical dysfunction occurs. Three hypothetical explanations for the lack of clear relation between global CBF and electrical brain activity of the preterm infant must be examined more closely: (1) the very low levels of CBF are adequate, (2) global CBF does not reflect the perfusion of the white matter, or (3) acute white-matter ischaemia does not result in cerebro-electrical dysfunction. In view of the practical importance, more research is indicated.