Correlation between fractional anisotropy and motor outcomes in one-year-old infants with periventricular brain injury

Abstract

Purpose: To determine whether motor outcomes of an exercise intervention beginning at 2 months corrected age (CA) in children with periventricular brain injury (PBI) are correlated with fractional anisotropy (FA) measures derived from diffusion tensor imaging (DTI) at 12 months CA.

Materials and methods: DTI was performed in eight infants with PBI who were randomly assigned to kicking and treadmill stepping exercise or a no-training condition. Development was assessed using the Alberta Infant Motor Scale (AIMS) and the Gross Motor Function Classification System (GMFCS). FA values were derived from regions of interest (ROIs) in the middle third of the posterior limb of the internal capsule (PLIC) and the posterior thalamic radiation (PTR).

Results: Significant correlations were observed between motor development and FA measures. For PLIC, the correlation coefficients were 0.82 between FA and AIMS, and -0.92 between FA and GMFCS, while for PTR the corresponding correlation coefficients were 0.73 and -0.80, respectively.

Conclusion: Results of this study suggest that quantitative evaluation of white matter tracts using DTI at 12 months CA may be useful for assessment of brain plasticity in children.

Keywords: DTI; fractional anisotropy (FA); infants; periventricular brain injury; treadmill exercise.

Figure 1

Representative images from two children showing varying degree of brain injuries. The top row was taken from a subject who had a high symmetry of FA and normal development, while the bottom row corresponded to another subject who had cerebral palsy and a greater asymmetry of FA. Three images are shown from each subject: axial T1-weighted FSPGR image (left), axial FA image in gray scale (middle) and color coded FA image (right), all matched to the same location at the level of the internal capsule. The ROIs used in the FA analysis are schematically indicated in the middle images with PLIC ROI denoted in orange and the PTR ROI in green. The color-coded FA images on the right show the fiber orientations (red: right-left; green: anterior-posterior; blue: superior-inferior direction), which were used to aid ROI selection.

Figure 2

Correlation between AIMS score and average FA at the PLIC (left) and average FA at the PTR (right).

Figure 3

Correlation between GMFCS score and average FA at the PLIC (left) and average FA at the PTR (right).

Figure 4

An FSPGR T1-weighted anatomical image (left), gray-scale FA image (middle) and color-coded FA image ( right ) from a subject with hemiplegic cerebral palsy. This subject had a high FA asymmetry of 0.153 in the PLIC and 0.271 in the PTR. Note the remarkable disruption of corticospinal tracts at the level of the internal capsule on the right side of the brain.