Diffusion Tensor Imaging of Mild to Moderate Blast-Related Traumatic Brain Injury and Its Sequelae

Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, Texas 77030, USA.
Journal of neurotrauma (Impact Factor: 3.71). 04/2010; 27(4):683-94. DOI: 10.1089/neu.2009.1073
Source: PubMed


To evaluate the effects of mild to moderate blast-related traumatic brain injury (TBI) on the microstructure of brain white matter (WM) and neurobehavioral outcomes, we studied 37 veterans and service members (mean age 31.5 years, SD = 7.2; post-injury interval 871.5 days; SD = 343.1), whose report of acute neurological status was consistent with sustaining mild to moderate TBI due to blast while serving in Iraq or Afghanistan. Fifteen veterans without a history of TBI or exposure to blast (mean age 31.4 years, SD = 5.4) served as a comparison group, including seven subjects with extracranial injury (post-injury interval 919.5 days, SD = 455.1), and eight who were uninjured. Magnetic resonance imaging disclosed focal lesions in five TBI participants. Post-concussion symptoms (Neurobehavioral Symptom Inventory), post-traumatic stress disorder (PTSD) symptoms (PTSD Checklist-Civilian), and global distress and depression (Brief Symptom Inventory) were worse in the TBI participants than the comparison group, but no group differences were found in perceived physical or mental functioning (SF-12). Verbal memory (Selective Reminding) was less efficient in the TBI group, but there were no group differences in nonverbal memory (Selective Reminding) or decision making (Iowa Gambling Task). Verbal memory in the TBI group was unrelated to PTSD severity. Diffusion tensor imaging (DTI) using tractography, standard single-slice region-of-interest measurement, and voxel-based analysis disclosed no group differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC). However, FA of the left and right posterior internal capsule and left corticospinal tract was positively correlated with total words consistently recalled, whereas ADC for the left and right uncinate fasciculi and left posterior internal capsule was negatively correlated with this measure of verbal memory. Correlations of DTI variables with symptom measures were non-significant and inconsistent. Our data do not show WM injury in mild to moderate blast-related TBI in veterans despite their residual symptoms and difficulty in verbal memory. Limitations of the study and implications for future research are also discussed.

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    • "Nonetheless , some studies have failed to find abnormalities in specific white matter tracts , particularly in the blast - related mTBI literature ( Bazarian et al . , 2013 ; Ilvesmaki et al . , 2014 ; Levin et al . , 2010 ; Watts et al . , 2014 ) . These diverse outcomes likely reflect heterogeneity in the distribution of mTBI pathology across individuals , associated with variable direction and location of injury forces . For instance , using methods optimized for assessment of individual mTBI patients , Lipton et al . ( 2012 ) showed that the pattern o"
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    ABSTRACT: Recent advances in neuroimaging methodologies sensitive to axonal injury have made it possible to assess in vivo the extent of traumatic brain injury (TBI) -related disruption in neural structures and their connections. The objective of this paper is to review studies examining connectivity in TBI with an emphasis on structural and functional MRI methods that have proven to be valuable in uncovering neural abnormalities associated with this condition. We review studies that have examined white matter integrity in TBI of varying etiology and levels of severity, and consider how findings at different times post-injury may inform underlying mechanisms of post-injury progression and recovery. Moreover, in light of recent advances in neuroimaging methods to study the functional connectivity among brain regions that form integrated networks, we review TBI studies that use resting-state functional connectivity MRI methodology to examine neural networks disrupted by putative axonal injury. The findings suggest that TBI is associated with altered structural and functional connectivity, characterized by decreased integrity of white matter pathways and imbalance and inefficiency of functional networks. These structural and functional alterations are often associated with neurocognitive dysfunction and poor functional outcomes. TBI has a negative impact on distributed brain networks that lead to behavioral disturbance.
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    • "However, others have not detected group differences between Service Members and Veterans with and without a reported history of TBI using voxel-based analyses (Davenport et al. 2012; Jorge et al. 2012) or tractography (Levin et al. 2010). Levin et al.'s initial study comparing 37 OIF/OEF Veterans and Service Members with chronic phase mild to moderate blast-related TBI and 15 Veterans without a history of TBI or exposure to blast revealed no differences on DTI-based measures of diffusion (FA and apparent diffusion coefficient or ADC), though DTI measures were related to cognitive performance in some domains (Levin et al. 2010). Jorge et al. used DTI to examine white matter integrity in a relatively larger group (N=72) of Iraq and Afghanistan Veterans with a history of mTBI as compared to a comparison group of deployed Veterans without a history of TBI (N=21) (Jorge et al. 2012). "
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    • "We found that in blast-exposed OEF/OIF veterans, physical PCS severity was associated with the number of white matter abnormalities even after accounting for PTSD symptom severity. These findings support and extend those of two previous studies investigating the association between white matter integrity and chronic PCS following blast exposure [Levin et al., 2010; Yeh et al., 2014]. While these studies did not take into account the contribution of mental health symptoms, our results demonstrate that the link between white matter abnormalities and physical PCS is independent of PTSD symptom severity. "
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