Neuroimaging, Behavioral, and Psychological Sequelae of Repetitive Combined Blast/Impact Mild Traumatic Brain Injury in Iraq and Afghanistan War Veterans

Abstract

Whether persisting cognitive complaints and postconcussive symptoms (PCS) reported by Iraq and Afghanistan war veterans with blast- and/or combined blast/impact-related mild traumatic brain injuries (mTBIs) are associated with enduring structural and/or functional brain abnormalities versus comorbid depression or posttraumatic stress disorder (PTSD) remains unclear. We sought to characterize relationships among these variables in a convenience sample of Iraq and Afghanistan-deployed veterans with (n=34) and without (n=18) a history of one or more combined blast/impact-related mTBIs. Participants underwent magnetic resonance imaging of fractional anisotropy (FA) and macromolecular proton fraction (MPF) to assess brain white matter (WM) integrity; [(18)F]-fluorodeoxyglucose positron emission tomography imaging of cerebral glucose metabolism (CMRglu); structured clinical assessments of blast exposure, psychiatric diagnoses, and PTSD symptoms; neurologic evaluations; and self-report scales of PCS, combat exposure, depression, sleep quality, and alcohol use. Veterans with versus without blast/impact-mTBIs exhibited reduced FA in the corpus callosum; reduced MPF values in subgyral, longitudinal, and cortical/subcortical WM tracts and gray matter (GM)/WM border regions (with a possible threshold effect beginning at 20 blast-mTBIs); reduced CMRglu in parietal, somatosensory, and visual cortices; and higher scores on measures of PCS, PTSD, combat exposure, depression, sleep disturbance, and alcohol use. Neuroimaging metrics did not differ between participants with versus without PTSD. Iraq and Afghanistan veterans with one or more blast-related mTBIs exhibit abnormalities of brain WM structural integrity and macromolecular organization and CMRglu that are not related to comorbid PTSD. These findings are congruent with recent neuropathological evidence of chronic brain injury in this cohort of veterans.

Chronic effects of exposure to high-intensity blasts: Results on tests of central auditory processing

“…It would be beneficial if future studies are designed in a way that enables researchers to reveal the full set of relationships among TBI, PTSD, central auditory processing, sensory processing in general, and cognitive processes such as memory, attention, and executive function. In addition to further testing in these areas, future studies would benefit from attempts to combine these metrics with structural and functional imaging, as such studies have already shown the potential to help dissociate factors such as PTSD from mTBI [23].…”

Quantitative Assessment of Normal Fetal Brain Myelination Using Fast Macromolecular Proton Fraction Mapping

“…The final sample included 41 fetuses with a mean GA Ϯ SD of 26.8 Ϯ 5.9 weeks (range, 18 -38 weeks). To verify the compatibility of MPF measurements using our protocol with previous studies, 4,5,11,12 we also recruited 3 healthy adults (31-and 51-year-old men and a 50-year-old woman). To study the effect of a possible noise bias on MPF measurements, we obtained an additional series of brain scans with variable SNRs from 1 healthy volunteer (a 47-year-old man).…”

“…The MPF is a biophysical parameter describing the amount of macromolecular protons in tissues involved in cross-relaxation with free water showed promising clinical results in adult brain studies 11,12 and has been histologically validated as an accurate quantitative tool for measuring demyelination. 10 The single-point technique 4 also allowed designing an ultrafast MPF mapping protocol for nonbrain applications.…”

The role of biomarkers and MEG-based imaging markers in the diagnosis of post-traumatic stress disorder and blast-induced mild traumatic brain injury

“…Conventional CT and MRI are primarily sensitive to blood from nearby torn capillaries, rather than axonal damage itself, hence they underestimate the presence of DAI, especially in mTBI. New approaches using diffusion tensor imaging (DTI), positron emission topography (PET), and macromelecular proton fraction (MPF) have showed promising capability in detecting injuries and/or abnormalities that are not visible in CT and MRI (e.g., Petrie et al, 2014;MacDonald et al, 2011;Davenport et al, 2012;Shenton et al, 2012).…”