White matter integrity and cognition in chronic traumatic brain injury: a diffusion tensor imaging study

Abstract

Traumatic brain injury (TBI) is a serious public health problem. Even injuries classified as mild, the most common, can result in persistent neurobehavioural impairment. Diffuse axonal injury is a common finding after TBI, and is presumed to contribute to outcomes, but may not always be apparent using standard neuroimaging. Diffusion tensor imaging (DTI) is a more recent method of assessing axonal integrity in vivo. The primary objective of the current investigation was to characterize white matter integrity utilizing DTI across the spectrum of chronic TBI of all severities. A secondary objective was to examine the relationship between white matter integrity and cognition. Twenty mild, 17 moderate to severe TBI and 18 controls underwent DTI and neuropsychological testing. Fractional anisotropy, axial diffusivity and radial diffusivity were calculated from the DTI data. Fractional anisotropy was the primary measure of white matter integrity. Region of interest analysis included anterior and posterior corona radiata, cortico-spinal tracts, cingulum fibre bundles, external capsule, forceps minor and major, genu, body and splenium of the corpus callosum, inferior fronto-occipital fasciculus, superior longitudinal fasciculus and sagittal stratum. Cognitive domain scores were calculated from executive, attention and memory testing. Decreased fractional anisotropy was found in all 13 regions of interest for the moderate to severe TBI group, but only in the cortico-spinal tract, sagittal stratum and superior longitudinal fasciculus for the mild TBI group. White Matter Load (a measure of the total number of regions with reduced FA) was negatively correlated with all cognitive domains. Analysis of radial and axial diffusivity values suggested that all severities of TBI can result in a degree of axonal damage, while irreversible myelin damage was only apparent for moderate to severe TBI. The present data emphasize that white matter changes exist on a spectrum, including mild TBI. An index of global white matter neuropathology (White Matter Load) was related to cognitive function, such that greater white matter pathology predicted greater cognitive deficits. Mechanistically, mild TBI white matter changes may be primarily due to axonal damage as opposed to myelin damage. The more severe injuries impact both. DTI provides an objective means for determining the relationship of cognitive deficits to TBI, even in cases where the injury was sustained years prior to the evaluation.

Differential Adaptation of Descending Motor Tracts in Musicians

“…In agreement with previous studies (Toosy et al 2003;Kraus et al 2007;Imfeld et al 2009), we found a right-greaterthan-left asymmetry of FA values in corticospinal motor tracts across all subgroups (see Fig. 2 and Tables 2 and 3).…”

White Matter Changes and Confrontation Naming in Retired Aging National Football League Athletes

“…This suggests that different factors drive the variance in confrontation naming in the two groups. Although we cannot assume causality, white matter damage is well described in brain injuries, 13,39 and we have previously shown that retired symptomatic NFL athletes with cognitive impairment, depression, or both have compromised white matter integrity compared with either controls or asymptomatic retired NFL players. 30 In our voxelwise analysis, significant clusters within the athlete group were localized around the corpus callosum and its extending projections.…”

“…10 Speech is also supported in part by the left pre-supplementary motor area (pre-SMA). 12,13 These cortical regions in addition to others function as nodes in a network connected by white matter pathways to facilitate naming. Several of these white matter pathways have been defined.…”

Neuropsychological Sequelae of PTSD and TBI Following War Deployment among OEF/OIF Veterans

“…However, studies of civilians have demonstrated the utility of DTI for examining white matter abnormalities in TBI (e.g., Kraus, Susmaras, Caughlin, Walker, Sweeney, & Little, 2007). In that vein, the limited research on TBI in OEF/OIF Veterans that has been conducted to date has primarily relied upon DTI and high resolution MRI.…”