Macroscale White Matter Alterations Due to Traumatic Cerebral Microhemorrhages Are Revealed by Diffusion Tensor Imaging

Abstract

With the advent of susceptibility-weighted imaging (SWI), the ability to identify cerebral microbleeds (CMBs) associated with mild traumatic brain injury (mTBI) has become increasingly commonplace. Nevertheless, the clinical significance of post-traumatic CMBs remains controversial partly because it is unclear whether mTBI-related CMBs entail brain circuitry disruptions which, although structurally subtle, are functionally significant. This study combines magnetic resonance and diffusion tensor imaging (MRI and DTI) to map white matter (WM) circuitry differences across 6 months in 26 healthy control volunteers and in 26 older mTBI victims with acute CMBs of traumatic etiology. Six months post-mTBI, significant changes (p < 0.001) in the mean fractional anisotropy of perilesional WM bundles were identified in 21 volunteers, and an average of 47% (σ = 21%) of TBI-related CMBs were associated with such changes. These results suggest that CMBs can be associated with lasting changes in perilesional WM properties, even relatively far from CMB locations. Future strategies for mTBI care will likely rely on the ability to assess how subtle circuitry changes impact neural/cognitive function. Thus, assessing CMB effects upon the structural connectome can play a useful role when studying CMB sequelae and their potential impact upon the clinical outcome of individuals with concussion.

Acute cognitive deficits after traumatic brain injury predict Alzheimer’s disease-like degradation of the human default mode network

“…The occurrence of CMBs in geriatric mTBI patients is relevant to the spatial profile and severity of post-traumatic WM alterations [16, 46, 32]. Previously, we showed that the trajectories and integrities of WM fasciculi passing through the vicinity (penumbrae) of post-traumatic CMBs can be altered in ways which persist for at least six months post-injury [47, 48]. Furthermore, other studies have found that CMB count is associated with network alterations in patients with early AD as well [49].…”

Multimodal Imaging of Cerebral Microhemorrhages and White Matter Degradation in Geriatric Patients with Mild Traumatic Brain Injury

“…All data processing steps are based upon protocols used in past studies conducted in our laboratory [2][3][4][5][6][7].…”

Post-Traumatic Cerebral Microhemorrhages and their Effects Upon White Matter Connectivity in the Aging Human Brain

“…After parcellation, the most representative WM streamline in each cluster was identified using a streamline prototyping approach, as described elsewhere [4,5,7]. Briefly, this method can be applied to each WM cluster to facilitate the identification of a unique WM streamline whose trajectory and other properties are representative of the group of streamlines in the cluster.…”

“…Formally, for each WM streamline prototype, the null hypothesis was formulated as the statement that there is no statistically significant correlation between (A) the longitudinal difference in FA measured at vertices along the prototype streamline and (B) the topological (along-tract) distance between the closest CMB and each vertex along the streamline prototype. The topological distance was selected over the Euclidean distance because the diffusion of neurotoxins away from the CMB site is thought to be constrained by WM axon trajectories [7]. This suggests that the topological (along-tract) distance is a measure which reflects the parameters of the biophysics problem more realistically.…”