Longitudinal White Matter Changes after Traumatic Axonal Injury

Abstract

Diffusion tensor imaging (DTI) has been useful in showing compromise after traumatic axonal injury (TAI) at the chronic stage; however, white matter (WM) compromise from acute stage of TAI to chronic stage is not yet well understood. This study aims to examine changes in WM integrity following TAI by obtaining DTI, on average, 1 d post injury and again approximately seven months post-injury. Sixteen patients with complicated mild to severe brain injuries consistent with TAI were recruited in the intensive care unit of a Level I trauma center. Thirteen of these patients were studied longitudinally over the course of the first seven months post-injury. The first scan occurred, on average, 1 d after injury and the second an average of seven months post-injury. Ten healthy individuals, similar to the cohort of patients, were recruited as controls. Whole brain WM and voxel-based analyses of DTI data were conducted. DTI metrics of interest included: fractional anisotropy (FA), mean diffusivity, axial diffusivity (AD), and radial diffusivity (RD). tract-based spatial statistics were used to examine DTI metrics spatially. Acutely, AD and RD increased and RD positively correlated with injury severity. Longitudinal analysis showed reduction in FA and AD ( p < 0.01), but no change in RD. Possible explanations for the microstructural changes observed over time are discussed.

Examining the relationship between blast‐induced mild traumatic brain injury and posttraumatic stress‐related traits

“…In a study of 12 Iraq/Afghanistan veterans, the blast-exposed group showed hypermetabolism in some frontal cortex but showed hypometabolism in the right superior parietal region and deficits on the paced auditory addition test compared with controls (Mendez et al, 2013). Moreover, other studies are finding that long-term changes to the diffusivity of axons can be seen at 7 months following a TBI, echoing observations of changes in axonal diffusivity (Perez et al, 2014). Behaviorally, changes to emotionrelated brain regions such as the amygdala can result in expression of PTSD-like symptoms.…”

Combined Diffusion Tensor Imaging and Quantitative Susceptibility Mapping Discern Discrete Facets of White Matter Pathology Post-injury in the Rodent Brain

“…In a different TBI study, a proportional increase in AxD and RD without a significant change in FA at the acute stage (within 1-3 days) was followed by a disproportionate increase in AxD and RD in conjunction with a decrease in FA at the chronic stage (after 7 months) in patients (25). Early post-injury changes in RD were suggested to be a biomarker of oedema and demyelination (25). Song et al specifically explored the potential of AxD and RD as biomarkers of axonal damage and myelin degeneration in a mouse model of retinal ischemia (3).…”

“…This was concluded based on previously published histological findings on axonal swelling, damage, and recovery (24). In a different TBI study, a proportional increase in AxD and RD without a significant change in FA at the acute stage (within 1-3 days) was followed by a disproportionate increase in AxD and RD in conjunction with a decrease in FA at the chronic stage (after 7 months) in patients (25). Early post-injury changes in RD were suggested to be a biomarker of oedema and demyelination (25).…”

All Wrapped Up: Environmental Effects on Myelination

“…Cognitive impairment partly derives from a lack of structural and trophic support from OLs to axons, which fail to adequately remyelinate, thereby leading to axonal degeneration and disease progression [77]. In traumatic brain injury (TBI), myelin plasticity and remodeling influence recovery of WM integrity and resynchronization of cortical circuits [78,79]. Further, microstructural WM damage sustained during TBI can have lasting effects on cognition [80], behavior [81], and increase susceptibility to psychiatric [82] and neurodegenerative disorders like Parkinson’s disease [83].…”