Microstructural alterations in association tracts and language abilities in schoolchildren born very preterm and with poor fetal growth

Abstract

Background: Prematurity and perinatal risk factors may influence white matter microstructure. In turn, these maturational changes may influence language development in this high-risk population of children.

Objective: To evaluate differences in the microstructure of association tracts between preterm and term children and between preterm children with appropriate growth and those with fetal growth restriction and to study whether the diffusion tensor metrics of these tracts correlate with language abilities in schoolchildren with no severe neurological impairment.

Materials and methods: This study prospectively followed 56 very preterm children (mean gestational age: 28.7 weeks) and 21 age- and gender-matched term children who underwent diffusion tensor imaging at a mean age of 9 years. We used automated probabilistic tractography and measured fractional anisotropy in seven bilateral association tracts known to belong to the white matter language network. Both groups participated in language assessment using five standardised tests at the same age.

Results: Preterm children had lower fractional anisotropy in the right superior longitudinal fasciculus 1 compared to term children (P < 0.05). Preterm children with fetal growth restriction had lower fractional anisotropy in the left inferior longitudinal fasciculus compared to preterm children with appropriate fetal growth (P < 0.05). Fractional anisotropy in three dorsal tracts and in two dorsal and one ventral tract had a positive correlation with language assessments among preterm children and preterm children with fetal growth restriction, respectively (P < 0.05).

Conclusion: There were some microstructural differences in language-related tracts between preterm and term children and between preterm children with appropriate and those with restricted fetal growth. Children with better language abilities had a higher fractional anisotropy in distinct white matter tracts.

Keywords: Children; Diffusion tensor imaging; Language outcome; Magnetic resonance imaging; Preterm; Reading ability; White matter tracts.

Fig. 1

T1-weighted images with an overlay of the language-related tracts coded by colours in a 9.1-year-old healthy control girl who had normal findings on conventional magnetic resonance imaging. a A left sagittal image of the superior longitudinal fasciculus 2 is displayed in turquoise/pink, the superior longitudinal fasciculus 3 in green, the inferior fronto-occipital fasciculus in blue/light blue and the inferior longitudinal fasciculus in dark yellow. b An axial image with the left and right arcuate fasciculi displayed in red. c A left sagittal image with the superior longitudinal fasciculus 1 displayed in green. d An axial image with the left and right uncinate fasciculi displayed in blue

Fig. 2

Graphs (a−g) show the correlation between language testing scores on the x-axis and mean fractional anisotropy values in specific tracts on the y-axis, which were significant in the univariate linear regression analyses for very low gestational age children. Results remained significant after controlling for gestational age, gender, perinatal brain injury and maternal education level. Each black square represents data from a single subject

Fig. 3

Graphs (a−c) show the correlation between language testing scores on the x-axis and mean fractional anisotropy values in specific tracts on the y-axis, which were significant in the univariate linear regression analyses for very low gestational age children with fetal growth restriction. Results remained significant after controlling for gestational age, gender and maternal education level. Each black square represents data from a single subject