Mechanisms of brain damage in twins.

The brains of 18 twins dying in the perinatal period showed a variety of lesions. Eleven had subependymal cell plate hemorrhage which had ruptured into the lateral ventricles in five. Five had periventricular damage. Three had anoxic neuronal damage. One acardiac monster had bilateral cerebral infarction. One pair had unequal sized brains, probably due to unequal intrauterine nutrition. Twins have a high perinatal mortality and morbidity; as well, intrauterine events may alter brain growth and development in each twin unequally, so they are an imperfect model to study the effect of genes and environment on intelligence.