Alterations in Microstructure and Local Fiber Orientation of White Matter Are Associated with Outcome after Mild Traumatic Brain Injury

Abstract

Mild traumatic brain injury (mTBI) can result in long-lasting consequences. We investigated white matter (WM) alterations at 6-12 months following mTBI using diffusion tensor imaging and assessed if the alterations associate with outcome.Eighty-five patients with mTBI underwent diffusion-weighted MRI on average eight months post-injury and patients' outcome was assessed at the time of imaging using extended Glasgow outcome scale.Additionally, thirty age-matched patients with extracranial orthopedic injuries were used as control subjects. Voxel-wise analysis of the data was performed using tract-based spatial statistics approach and differences in microstructural metrics between groups were investigated. Furthermore, the susceptibility of the abnormalities to specific fiber orientations was investigated by analyzing the first eigenvector of the diffusion tensor in the voxels with significant differences.We found significantly lower fractional anisotropy and higher mean and radial diffusivity in patients with mTBI compared to control subjects while no significant differences were observed in axial diffusivity between the groups. The differences were present bilaterally in several WM regions and correlated with outcome. Moreover, multiple clusters were found in the principal fiber orientations of the significant voxels in anisotropy, and similar orientation patterns were found for the diffusivity metrics. These directional clusters correlated with patients' functional outcome.Our study showed that mTBI is associated with WM changes at the chronic stage and these alterations occur in several WM regions. In addition, several significant clusters of WM alterations in specific fiber orientations were found and these clusters were associated with outcome.

Refined Analysis of Chronic White Matter Changes after Traumatic Brain Injury and Repeated Sports-Related Concussions: Of Use in Targeted Rehabilitative Approaches?

“…Decreased AD and RD post injury may be related to such shrinkage, leading to less surface area along axons for parallel diffusion [16,51]. These data suggest that the time course of physiological recovery extends longer than initially thought in rSRC athletes [17]. In addition, previous inconsistent results matching cognitive outcome and DTI may depend on the different DTI analysis methods used [22][23][24]43,51,52].…”

“…The use of advanced MRI techniques, such as diffusion tensor imaging (DTI), can, in higher detail, reveal the presence of white matter injury that may cause injury-induced symptoms following TBI and SRC [8,[15][16][17]. DTI can both qualitatively and quantitatively demonstrate pathology not detected by other modalities and is, therefore, an important tool not only in the research setting but in the clinical setting as well [18].…”

A comparison of diffusion tensor imaging tractography and constrained spherical deconvolution with automatic segmentation in traumatic brain injury

“…Correlations were not found between GCS, GOSE, and PTA and the tractography results. There are mixed reports of tractography statistics correlating ( Kraus et al, 2007 , Kumar et al, 2009 , Lipton et al, 2009 , Mohammadian et al, 2020 , Mohammadian et al, 2017 , Niogi et al, 2008 ) or not correlating ( Churchill et al, 2017 , Studerus-Germann et al, 2018 , Wäljas et al, 2015 , Wäljas et al, 2014 ) with clinical variables. Although by far not a unique feature of our study, the lack of correlation might be considered to cast doubt on the clinical validity of the results.…”

Myelin Content in Mild Traumatic Brain Injury Patients with Post-Concussion Syndrome: Quantitative Assessment with a Multidynamic Multiecho Sequence

“…Traditionally, considerable attention has been devoted to the pathological alterations in neuronal cells within the GM in prior studies on brain injury [ 22 ]. However, recent studies have underscored that the loss of WM integrity is also implicated in the long-term prognosis of TBI patients [ 23 24 ]. In the analysis of WM integrity in mTBI, myelin is an attractive target because it mainly consists of bundles of myelin-ensheathed axons [ 22 ].…”