White matter abnormalities are related to microstructural changes in preterm neonates at term-equivalent age: a diffusion tensor imaging and probabilistic tractography study

Abstract

Background and purpose: Preterm infants have a high risk of brain injury and neurodevelopmental impairment, often associated with WMA on conventional MR imaging. DTI can provide insight into white matter microstructure. The aim of this study was to investigate the association between WMA on conventional MR imaging and DTI parameters in specific fibers in preterm neonates at term-equivalent age.

Materials and methods: Seventy preterm neonates (39 boys and 31 girls) were included in the study. WMA were classified as no, mild, moderate, or severe. Probabilistic tractography provided tract volumes, FA, MD, λ(//), and λ(⊥) in the CST, SLF, TRs, and corpus callosum. Data were compared by using MANOVA, and adjustment for multiple comparisons was performed.

Results: Important associations were found between WMA and microstructural changes. Compared with neonates with no WMA (n = 41), those with mild WMA (n = 27) had significantly increased λ(⊥) and MD in the left ATR, the left sensory STR, the bilateral motor STR, and for λ(⊥) also in the right CST; FA decreased significantly in the left sensory STR. Diminished tract volumes and altered diffusion indices were also observed in the 2 neonates with moderate WMA.

Conclusions: Altered DTI indices in specific tracts, with λ(⊥) as most prominent, are associated with mild WMA in preterm neonates at term-equivalent age.

Fig 1.

Tracts are shown on T2-weighted images in neonate with no WMA, scanned at 36 weeks corrected gestational age (A–D) and in neonate with moderate WMA, scanned at 38 weeks (E–H). Axial images (A, E) show the TRs (ATR in yellow, motor STR in yellow-red, sensory STR in blue and PTR in dark green). Axial images (B, F) show the corpus callosum (dark red). Sagittal images (C, G) show the frontoparietal SLF (dark blue) and parietotemporal SLF (pink). Coronal (D, H) images show the CSTs (light green). Images were obtained from a 1.5T magnet (Philips Achieva, Best, The Netherlands).

Fig 2.

The diffusion indices in the left sensory STR are shown by scatter plots with mean (line) in neonates with no WMA, mild WMA and moderate WMA. Statistically significant differences (taking into account the gestational age as a covariate and after controlling for false discovery rate) were found for FA (P < .001), MD (P = .001), and λ^⊥ (P < .001).