Cellular reactions to subependymal plate haemorrhage in the human neonate

The most important cause of death in human premature babies at the present time is intraventricular haemorrhage consequent to haemorrhage in the subependymal plate. Lesser degrees of plate haemorrhage can also have serious effects. It was possible to observe the reaction to such haemorrhages in twenty-seven cases whose range of gestational age extended from 23 to 36 weeks and survival from 4 to 59 days. The haemorrhage occurs in the first week of life, usually in the first few days. The earliest reaction at 4 days was the presence of mononuclear phagocytes around the haemorrhage, these evolved to iron pigment macrophages which were present in eighteen of the twenty-two cases in which some reaction was detected. Subependymal astrocytic proliferation was seen at 11 days, related to ependymal disruption, but an astrocytic reaction around the haemorrhage and related to it was not seen until 14 days. Within the subependymal plate this reaction was scanty in fibril production and the cells were thought to be derived from differentiating astrocytes in the plate. In one case a more marked reaction was detected to hypoxic damage in the adjacent thalamus. The source of the phagocytes in these sites and the reasons for the rather slow astrocytic reaction are discussed.