Structural, immunocytochemical, and mr imaging properties of periventricular crossroads of growing cortical pathways in preterm infants.

BACKGROUND AND PURPOSE Periventricular white matter (WM) areas are widely recognized as predilection sites for complex cellular damage after ischemia/reperfusion or inflammatory injury of the perinatal cerebrum. We analyzed histochemical and MR imaging properties of fiber architectonics and extracellular matrix (ECM) of periventricular areas to disclose the potential significance of topographically specific WM lesions for the neurodevelopmental outcome. METHODS We combined histochemical methods for demonstration of fibers, axonal guidance molecules, and ECM with T1-weighted MR images on postmortem specimens aged 15 to 36 postovulatory weeks (POW) and T2-weighted MR images on in vivo fetuses aged 14 to 26 POW. RESULTS The fiber architectonics of the fetal cerebrum display tangential axon strata in frontopolar and occipitopolar regions, whereas the central periventricular region contains crossroads of intersecting callosal (transverse), associative (sagittal), and thalamocortical/corticofugal (radial) fiber bundles. In early preterms, crossroads contain hydrophylic ECM with axonal guidance molecules, and they are easily recognized as hypointensities on T1-weighted MR images or hyperintensities on T2-weighted MR images. After the 28 POW, tangential fetal fiber-architectonic stratification transforms into the corona radiata system; however, the growth of cortical pathways continues in crossroad areas, as indicated by the presence of ECM and their distinct MR imaging signal intensities. CONCLUSIONS The correlation of MR imaging with histochemical findings demonstrated the presence of periventricular fiber crossroads rich in ECM and axonal guidance molecules. We propose that, in perinatal WM lesions, periventricular WM crossroads represent a hitherto unrecognized and vulnerable cellular and topographic target in which combined damage of association-commissural and projection fibers may explain the complexity of cognitive, sensory, and motor deficit in survivors of periventricular WM lesions.