Concurrent decrease of brain white matter tracts' thicknesses and fractional anisotropy after antenatal hypoxia-ischemia detected with tract-based spatial statistics analysis.

PURPOSE: To examine the extent of gray and white matter (WM) injury following global antenatal hypoxia-ischemia (H-I) and resulting in muscle hypertonia in newborns in a rabbit cerebral palsy model.
MATERIALS AND METHODS: Rabbit dams (n = 15) underwent uterine ischemia procedure resulting in a global fetal H-I at embryonic day 22 (embryonic 22 days gestation). Newborn's brains underwent high resolution diffusion tensor imaging on a 14 Tesla magnet ex vivo. Fractional anisotropy (FA) in brains of hypertonic (n = 9), nonhypertonic (n = 6), and sham control (n = 5) kits were compared voxel-wise using Tract-Based Spatial Statistics (TBSS) approach. Herein, we used a novel method to assess local WM tracts' thicknesses in TBSS analysis and compare between the groups.
RESULTS: Significant (corrected P < 0.05) reduction of WM FA was found in corpus callosum splenium (91.2%), periventricular WM (83.5%), fimbria hippocampi (78.8%), cingulum (81.4%), anterior commissure (95%), internal capsule (83.2%), and optic tract (82.9%) in the hypertonic group. Significant (corrected P < 0.05) reduction in WM tracts' thicknesses was found in corpus callosum (73.3%), periventricular WM (82.5%), cingulum (73.4%), bilaterally in the hypertonic group.
CONCLUSION: WM injury in newborn hypertonic kits 10 days after global fetal H-I is widespread and involves not only motor but also limbic and commissural fibers in multiple regions. WM injury in newborn hypertonic kits is manifested by changes in microstructural properties and decreased FA, as well as reduction of WM volumes, relative to nonhypertonic kits. J. Magn. Reson. Imaging 2017;45:700-709. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:829-838.