Prematurity and prenatal growth restriction differently affects brain connectivity at age 6 years.

Survival of children born prematurely or with very low birth weight has increased dramatically but the long term developmental outcome remains a concern with many children having deficits in their cognitive capacities, in particular involving executive domains. The origins of these disabilities are largely unknown but are likely to involve an overriding central nervous system deficit. In prior studies we and others had shown that both prematurity and IUGR affect newborn brain structures (cite Inder TE 2005, Borradori-Tolsa Ped Res 04 Dubois brain 08). To understand the neurostructural origin of this disabilities, we used DTI to study brain connectivity at the age of 6 years. Structurally segregated and functionally specialized regions of the cerebral cortex are interconnected by a dense network of axonal pathways. We noninvasively map these pathways across cortical hemispheres and construct normalized structural connection matrices derived from diffusion tensor MR tractography. Statistical group comparisons of brain connectivity reveal significant changes in fibers density in children who were born moderately premature but with poor intrauterine growth, in extremely premature (EP) children (less than 28 weeks of gestational age at birth) compared to control subjects, who were born moderately premature but with normal growth. Moderately premature babies with normal growth generally compare to children born fullterm in their neurodevelopmental outcome. These localized changes in connectivity suggest a direct link between cortico-axonal pathways and the central nervous system deficits observed in these children.