Assessment of Neuropsychological Function in Veterans With Blast-Related Mild Traumatic Brain Injury and Subconcussive Blast Exposure.

Ashley N Clausen,Heather C Bouchard,Va Mid-Atlantic Mirecc Workgroup ,Rajendra A Morey,Kathleen A Welsh-Bohmer

doi:10.3389/fpsyg.2021.686330

Abstract

Objective: The majority of combat-related head injuries are associated with blast exposure. While Veterans with mild traumatic brain injury (mTBI) report cognitive complaints and exhibit poorer neuropsychological performance, there is little evidence examining the effects of subconcussive blast exposure, which does not meet clinical symptom criteria for mTBI during the acute period following exposure. We compared chronic effects of combat-related blast mTBI and combat-related subconcussive blast exposure on neuropsychological performance in Veterans.Methods: Post-9/11 Veterans with combat-related subconcussive blast exposure (n = 33), combat-related blast mTBI (n = 26), and controls (n = 33) without combat-related blast exposure, completed neuropsychological assessments of intellectual and executive functioning, processing speed, and working memory via NIH toolbox, assessment of clinical psychopathology, a retrospective account of blast exposures and non-blast-related head injuries, and self-reported current medication. Huber Robust Regressions were employed to compare neuropsychological performance across groups.Results: Veterans with combat-related blast mTBI and subconcussive blast exposure displayed significantly slower processing speed compared with controls. After adjusting for post-traumatic stress disorder and depressive symptoms, those with combat-related mTBI exhibited slower processing speed than controls.Conclusion: Veterans in the combat-related blast mTBI group exhibited slower processing speed relative to controls even when controlling for PTSD and depression. Cognition did not significantly differ between subconcussive and control groups or subconcussive and combat-related blast mTBI groups. Results suggest neurocognitive assessment may not be sensitive enough to detect long-term effects of subconcussive blast exposure, or that psychiatric symptoms may better account for cognitive sequelae following combat-related subconcussive blast exposure or combat-related blast mTBI.

Highlights

For post-9/11 military service members, the majority of combatrelated mild traumatic brain injuries are associated with blast exposure (Galarneau et al, 2008; Greer et al, 2016)
Neuroimaging research exploring primary blast exposure indicates evidence that both concussive and subconcussive blast exposure are associated with alterations in brain function within the default mode and dorsal attention networks (Robinson et al, 2015, 2017), functional connectivity within the default mode network (Robinson et al, 2015), and white matter damage associated with lower fractional anisotropy and higher radial diffusivity (Taber et al, 2015; Trotter et al, 2015), which may explain cognitive deficits associated with blast exposure
Veterans in the mild traumatic brain injuries (mTBI) (ψ = 3.6, p < 0.001) and subconcussive (ψ = 2.3, p = 0.044) groups exhibited significantly more blast exposure compared to Veterans in the control group

Summary

Introduction

For post-9/11 military service members, the majority of combatrelated mild traumatic brain injuries (mTBI) are associated with blast exposure (Galarneau et al, 2008; Greer et al, 2016). Studies have identified acute deficits from military-related mTBI (frequently resulting from blast exposure) associated with processing speed, verbal and visual memory, executive function, and reaction time (Luethcke et al, 2011; Kontos et al, 2013; Karr et al, 2014; Norris et al, 2014; Spira et al, 2014; Pagulayan et al, 2018). Neuroimaging research exploring primary blast exposure indicates evidence that both concussive (mTBI) and subconcussive blast exposure are associated with alterations in brain function within the default mode and dorsal attention networks (Robinson et al, 2015, 2017), functional connectivity within the default mode network (Robinson et al, 2015), and white matter damage associated with lower fractional anisotropy and higher radial diffusivity (Taber et al, 2015; Trotter et al, 2015), which may explain cognitive deficits associated with blast exposure

Methods

Results

Discussion

Conclusion