Quantitative fiber tracking in the corpus callosum and internal capsule reveals microstructural abnormalities in preterm infants at term-equivalent age

Abstract

Background and purpose: Signal-intensity abnormalities in the PLIC and thinning of the CC are often seen in preterm infants and associated with poor outcome. DTI is able to detect subtle abnormalities. We used FT to select bundles of interest (CC and PLIC) to acquire additional information on the WMI.

Materials and methods: One hundred twenty preterm infants born at <31 weeks' gestation with 3T DTI at TEA entered this prospective study. Quantitative information (ie, volume, length, anisotropy, and MD) was obtained from fiber bundles passing through the PLIC and CC. A general linear model was used to assess the effects of factor (sex) and variables (GA, BW, HC, PMA, and WMI) on FT-segmented parameters.

Results: Seventy-two CC and 85 PLIC fiber bundles were assessed. For the CC, increasing WMI and decreasing FA (P = .038), bundle volume (P < .001), and length (P = .001) were observed, whereas MD increased (P = .001). For PLIC, MD increased with increasing WMI (P = .002). Higher anisotropy and larger bundle length were observed in the left PLIC compared with the right (P = .003, P = .018).

Conclusions: We have shown that in the CC bundle, anisotropy was decreased and diffusivity was increased in infants with high WMI scores. A relation of PLIC with WMI was also shown but was less pronounced. Brain maturation is affected more if birth was more premature.

Fig 1.

3D FT superimposed on 2D ADC maps. A, Whole-brain FT results, in a preterm infant at TEA. View from the front left. B, Definition of PLIC ROIs. View from the top (on the axial plane). ROIs superimposed on an FA-weighted color map. C, Definition of CC ROIs. View from the left (on the sagittal plane). ROIs superimposed on an FA-weighted color map. D, PLIC fiber bundle. View from the right (on the sagittal plane). ROIs superimposed on an FA-weighted color map. E, CC fiber bundle. View from the front left (on the sagittal plane). ROIs superimposed on an ADC map. CST indicates the corticospinal tract; CR, the corona radiata; FX, the fornix; CG, the cingulum.

Fig 2.

Bundle volume, Cl, length, average MD, axial diffusivity, and radial diffusivity are shown as a function of the WM score. Red triangles indicate the CC; blue squares, the left PLIC; and green circles, the right PLIC. The symbols are only for clarity and are shifted with respect to each other, to avoid cluttering of the information. The trend lines are only displayed in the graphs if the correlation was significant. For the CC, 72 bundles were evaluated and displayed in this graph, for the PLIC, 85 bundles.

Fig 3.

Average values for bundle volume, Cl, bundle length, and average MD for the groups with CC scores 1 (normal CC), 2 (mild thinning of the CC), and 3 (severe thinning of the CC). Red triangles indicate the CC; blue squares, the PLIC L; and green open circles, the PLIC R. In total, 72 CC fiber bundles were evaluated, with n = 19 in group 1, n = 40 in group 2, and n = 11 in group 3 for the CC. Displayed is the mean, and the error bar displays the standard average of the mean. Asterisk denotes a significant difference (P < .05).