Neuropsychologic function in same-sex twins discordant for perinatal brain damage.

We studied childhood neuropsychologic function in two pairs of low birth weight, same-sex twins reared together but with different patterns of concordance and discordance for intraventricular hemorrhage (IVH) and hydrocephalus (HYD). Same-sex twins have discordant levels of cognitive skills when one twin but not the other develops IVH alone or IVH and HYD at birth. The results bear on several issues: the effects of prematurity, the effects of IVH, the combined effects of IVH and HYD, and the potential applications of the present methodology of pairwise-matched twin comparisons for understanding how different forms of perinatal brain damage affect childhood cognitive functions important for learning.