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Comparisons of white matter (WM) fractional anisotropy (FA) values between mild traumatic brain injury (mTBI) patients and controls have revealed inconsistencies in the directions of the resulting FA changes. To address these discrepancies, we examined hemispheric FA symmetry levels across WM tracts in 150 mTBI patients relative to 96 military controls. Automated fiber quantification was used to extract 18 WM tracts with 100 FA values, which were used to compute correlation strengths between the nine bilateral tract pairs. The Fisher z-transformed Pearson's r values were entered into an analysis of covariance examining the effects of group (mTBI and controls) and age on symmetry levels within each tract pair. The mTBI group displayed lower symmetry levels in the corticospinal tract and the inferior longitudinal fasciculus. Interactions between age and group were detected in the inferior fronto-occipital (IFOF), uncinate (UF), and superior longitudinal fasciculi (SLF). A similar pattern emerged in the IFOF and the UF, revealing age-related symmetry decreases in the mTBI patients despite stable levels of symmetry across ages in controls. In contrast, although the control group's symmetry levels actually increased with age in the SLF, no age-related symmetry changes were detected across the mTBI participants. Here, we proposed WM symmetry measures as a potential means of circumventing directional inconsistencies of trauma-related FA changes, as well as capturing more within-tract and within-subject variances of diffusion tensor imaging (DTI) metrics. Further, we demonstrated the method's utility in detecting mTBI-specific effects and their associated interactions with age. [ABSTRACT FROM AUTHOR]

There are no studies to date,describing changes in the diffusion tensor imaging (DTI) metrics of the white matter (WM) regions of the entire cervical and thoracic spinal cord (SC) remote from the lesion in pediatric spinal cord injury (SCI) subjects. The purpose of this study was to determine whether DTI at sites cephalad and caudal to a lesion provides measures of cord abnormalities in children with chronic SCI. A retrospective study included 10 typically developing subjects (TD) and 10 subjects with chronic SCI who underwent SC imaging in 2014–2017. Axial diffusion tensor images using an inner field of view DTI sequence were acquired to cover the entire cervical and thoracic SC. Regions of interest were drawn on the SC WM: right and left lateral (motor), ventral (motor), and dorsal (sensory) tracts. To detect differences in DTI metrics between TD and SCI of the cord, a one way analysis of variance with pooled t test was performed. A stepwise regression analysis was performed to assess the correlation between DTI metrics and clinical scores. In motor and sensory tracts, fractional anisotropy (FA) and axial diffusivity (AD) were significantly decreased in the proximal segments of the caudal cord. In motor tracts cephalad to the lesion, FA was significantly decreased whereas AD was significantly increased in the proximal segment; however, AD was decreased in the distal and middle segments. International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) total score was significantly correlated with FA and AD of the motor and sensory tracts cephalad to the lesion. This study demonstrates that FA and AD have the potential to be sensitive biomarkers of the full extent of cord injury and might be useful in detecting remote injuries to the SC and in guiding new treatments. [ABSTRACT FROM AUTHOR]