Brain growth in Down syndrome subjects 15 to 22 weeks of gestational age and birth to 60 months.

We have found similarities of skull shape, brain growth and brain maturation in 17 DS and 10 non-DS (control) fetuses, ages 15-22 weeks of gestational age (Group A), and differences in 101 DS and 80 non-DS cases, from birth to 60 months (Group B). Postnatally, the gross neuropathological differences between DS and control brains are more distinct after 3-5 months of age. The anterior posterior diameter fronto-occipital length of the brain hemispheres is shortened and that is secondary to reduction of frontal lobe growth. Also flattening of occipital poles, narrowing of the superior temporal gyruses and generalized retardation of brain growth were common findings. Standard morphometric methods indicate changes from birth [Wisniewski et al. 1984, 1986, 1990]. The cerebral cortex of the DS cases had a 20-50% reduction of neurons since birth, mainly in the granular layers [Wisniewski et al. 1984, 1986, 1990]. Changes in brain weight with age were greater in the non-DS than in the DS cases, and greater in males than in females. CHD and GI malformations were associated with less brain weight in both DS and non-DS cases. We suggest that the prenatal retardation of neurogenesis begins after 22 weeks' gestational age. The postnatal retardation of brain growth is secondary to pre- and postnatal abnormalities in synaptogenesis.