Structural asymmetries in neonatal brain white matter: a diffusion tensor imaging study / 中华放射学杂志

ABSTRACT

Objective:To explore the asymmetry of neonatal brain white matter using fractional anisotropy (FA) parameter generated from diffusion tensor imaging (DTI).Methods:From January 2011 to June 2013, 88 neonates with normal cranial MRI performance, aged 1-14 (7.7±0.3) days and gestational age 31-42 (37.5±0.3) weeks, were retrospectively collected from the First Affiliated Hospital of Xi′an Jiaotong University. According to the gestational age at birth, the neonates were divided into preterm group (37 cases) and term group (51 cases). DTI was processed to generate FA parametric maps. Tract-based spatial statistics (TBSS) was used to analyze the asymmetry in neonatal white matter. Regions of interest were placed in bilaterally symmetrical white matter tracts. The white matter tracts included the bilateral anterior thalamic radiation, corticospinal tract-posterior limb of the inner capsule (CST-IC), corticospinal tract-corona radiata, cingulum hippocampus part (CGH), inferior frontal occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), superior longitudinal fasciculus (SLF), uncinate fasciculus, superior longitudinal fasciculus temporal part (SLF-temp). The FA value was measured and asymmetry index (AI) was calculated. The independent-sample t test or Mann-Whitney U test was used to compare the AI of each tract between the preterm and term groups. Partial correlation was used to analyze the effects of neonatal gestational age and birth anthropometric measures on the asymmetry of neonate at birth. Results:The results of TBSS showed that the left lateralized areas of brain white matter in the neonatal period were mainly located in the corticospinal tract, external capsule and genu of corpus callosum. The right lateralized areas of brain white matter in the neonatal period were mainly located in the optic radiation and splenium of corpus callosum. In both the preterm and term groups, the tracts related to motor (CST-IC) and language function (ILF, SLF, SLF-temp) were left asymmetry. The CGH of the preterm and the term neonates were right asymmetry, and AI was -0.086±0.114 and -0.140±0.108 respectively, with a statistically significant difference ( t=2.27, P=0.026), while the differences of AI in the remaining tracts were not statistically significant ( P>0.05). Only gestational age was correlated with the AI of ILF ( r=0.234, P=0.033), SLF ( r=0.259, P=0.018), SLF-temp ( r=0.252, P=0.022), CST-IC ( r=0.235, P=0.033). No significant correlation was found between birthweight, head circumference, body length and AI. Conclusions:The asymmetries of brain white matter already exist in neonates aged less than two weeks. The tracts associated with motor and language function are predominantly left asymmetry.