Effects of chronic mild traumatic brain injury on white matter integrity in Iraq and Afghanistan war veterans.
Mild traumatic brain injury (TBI) is a common source of morbidity from the wars in Iraq and Afghanistan. With no overt lesions on structural MRI, diagnosis of chronic mild TBI in military veterans relies on obtaining an accurate history and assessment of behavioral symptoms that are also associated with frequent comorbid disorders, particularly posttraumatic stress disorder (PTSD) and depression. Military veterans from Iraq and Afghanistan with mild TBI (n = 30) with comorbid PTSD and depression and non-TBI participants from primary (n = 42) and confirmatory (n = 28) control groups were assessed with high angular resolution diffusion imaging (HARDI). White matter-specific registration followed by whole-brain voxelwise analysis of crossing fibers provided separate partial volume fractions reflecting the integrity of primary fibers and secondary (crossing) fibers. Loss of white matter integrity in primary fibers (P < 0.05; corrected) was associated with chronic mild TBI in a widely distributed pattern of major fiber bundles and smaller peripheral tracts including the corpus callosum (genu, body, and splenium), forceps minor, forceps major, superior and posterior corona radiata, internal capsule, superior longitudinal fasciculus, and others. Distributed loss of white matter integrity correlated with duration of loss of consciousness and most notably with "feeling dazed or confused," but not diagnosis of PTSD or depressive symptoms. This widespread spatial extent of white matter damage has typically been reported in moderate to severe TBI. The diffuse loss of white matter integrity appears consistent with systemic mechanisms of damage shared by blast- and impact-related mild TBI that involves a cascade of inflammatory and neurochemical events.
Duke-UNC Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina; Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina; Mental Illness Research Education and Clinical Center for Post Deployment Mental Health, Durham VA Medical Center, Durham, North Carolina.
Rajendra A
RA
Morey
Courtney C
CC
Haswell
Elizabeth S
ES
Selgrade
Dino
D
Massoglia
Chunlei
C
Liu
Jonathan
J
Weiner
Christine E
CE
Marx
Ibolja
I
Cernak
Gregory
G
McCarthy
D000293:Adolescent; D000328:Adult; D055826:Afghan Campaign 2001-; D000368:Aged; D001921:Brain / Q000473:pathology*; D001930:Brain Injuries / Q000473:pathology* / Q000523:psychology; D001931:Brain Mapping; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D054542:Iraq War, 2003-2011; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology; D009483:Neuropsychological Tests; D012044:Regression Analysis; D013313:Stress Disorders, Post-Traumatic / Q000523:psychology; D014474:Unconsciousness / Q000150:complications / Q000209:etiology; D014728:Veterans; D055815:Young Adult