Microstructural brain development between 30 and 40 weeks corrected age in a longitudinal cohort of extremely preterm...

Diffusion tensor imaging (DTI) is frequently used to assess brain development in preterm infants. This study investigates maturational changes in diffusivity measures in 122 regions of the brain between 30 and 40 weeks postmenstrual age (PMA) using the neonatal atlas of Oishi and colleagues (Oishi et al., 2011). Forty infants without cerebral injury and with normal neurodevelopmental outcome were selected from a cohort of preterm infants (gestational age<28 weeks), scanned longitudinally at 30 and 40 weeks PMA. Fractional anisotropy (FA) changed significantly in 84 brain regions, with the largest increase in the central brain regions; by contrast, the cortical brain regions showed a decrease in FA. Mean, radial and axial diffusivity all showed a clear decrease in the majority of brain regions. This study provides longitudinal reference diffusivity values in a cohort of extremely preterm infants, showing a central to peripheral and posterior to anterior directed gradient, in line with our current understanding of brain maturation, and adding to this knowledge. This study further elucidates brain maturation in preterm infants during the last 10 weeks prior to term equivalent age. The presented values can be used as a reference for assessing brain development in other cohorts, when investigating the effects of brain injury in this vulnerable period, and to evaluate the effect of future neuroprotective strategies.