Whole brain and corpus callosum diffusion tensor metrics: How do they correlate with visual and verbal memory performance in chronic traumatic brain injury

This research investigates the chronic effect of moderate to severe traumatic brain injury on brain white matter integrity, as reflected by diffusion tensor imaging metrics, and the assessment of their correlation to neuropsychological response. Thirteen male participants with traumatic brain injury (8.4 years average post-injury time) were compared to a matched group of neurologically healthy controls. None of the traumatic brain injury subjects had received post-acute neurocognitive and/or neuropsychological rehabilitation. Between-group comparison of fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity was performed for the whole brain and corpus callosum. An extensive battery of visual and verbal memory tasks was employed for the comparative assessment of neurocognitive performance. Between-group and within-group performance differences were correlated with fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity of corpus callosum. Significant changes in global fractional anisotropy, mean diffusivity, and radial diffusivity were associated with traumatic brain injury. Visual memory capacity was reduced in traumatic brain injury, and this deficit was correlated to white matter integrity loss at the corpus callosum. Participants with traumatic brain injury underperformed controls in verbal memory as well, but no correlation with corpus callosum diffusion tensor imaging properties was established. Between-group performance difference was correlated with corpus callosum diffusion metrics in several tasks. Significant correlations were found between corpus callosum diffusion tensor imaging metrics and neuropsychological response within the traumatic brain injury group. Changes in whole brain and corpus callosum diffusion tensor metrics inflicted by moderate to severe traumatic brain injury are still evident several years post-injury and relate to neurocognitive impairment, while loss of white matter integrity seems to correlate with episodic and working memory impairment.