Functional MRI in the Investigation of Blast-Related Traumatic Brain Injury

Abstract

This review focuses on the application of functional magnetic resonance imaging (fMRI) to the investigation of blast-related traumatic brain injury (bTBI). Relatively little is known about the exact mechanisms of neurophysiological injury and pathological and functional sequelae of bTBI. Furthermore, in mild bTBI, standard anatomical imaging techniques (MRI and computed tomography) generally fail to show focal lesions and most of the symptoms present as subjective clinical functional deficits. Therefore, an objective test of brain functionality has great potential to aid in patient diagnosis and provide a sensitive measurement to monitor disease progression and treatment. The goal of this review is to highlight the relevant body of blast-related TBI literature and present suggestions and considerations in the development of fMRI studies for the investigation of bTBI. The review begins with a summary of recent bTBI publications followed by discussions of various elements of blast-related injury. Brief reviews of some fMRI techniques that focus on mental processes commonly disrupted by bTBI, including working memory, selective attention, and emotional processing, are presented in addition to a short review of resting state fMRI. Potential strengths and weaknesses of these approaches as regards bTBI are discussed. Finally, this review presents considerations that must be made when designing fMRI studies for bTBI populations, given the heterogeneous nature of bTBI and its high rate of comorbidity with other physical and psychological injuries.

Chronic Histopathological and Behavioral Outcomes of Experimental Traumatic Brain Injury in Adult Male Animals

“…A review by Graner and colleagues summarizing the applications of functional magnetic resonance imaging (MRI) suggested that bTBI survivors may experience symptoms related to stress and emotional disturbance related to underlying brain change (e.g., activation of the amygdala). 273 Clinically, there is a challenge in separating out these problems from more-severe psychological consequences, such as PTSD and major depressive disorder, both of which are common in military personnel. 274,275 In the context of animal models, bTBI led to prolonged psychological dysfunction for months, including enhanced contextual fear conditioning.…”

Neuroimaging of deployment-associated traumatic brain injury (TBI) with a focus on mild TBI (mTBI) since 2009

“…Several prior reviews have been written on TBI and mTBI in the civilian and Veteran fields extending from the peri-2009 period and before [20][21][22][23][24][25][26][27][28][29][30]. It is recommended that these prior sources complement this work.…”

Deficits in Visual System Functional Connectivity after Blast‐Related Mild TBI are Associated with Injury Severity and Executive Dysfunction

“…) – a system that may be affected by blast mTBI (Graner et al. ). The precuneus, per se, has shown both reduction in resting cerebral blood flow (Kim et al.…”

“…Precuneus has been suggested to be a "core node" or "hub" of the default-mode network (Fransson and Marrelec 2008), and it exhibits resting state FC with visual cortex (Margulies et al 2009). Given the proposed role of precuneus in directing attention (Cavanna and Trimble 2006), and its strong interconnections with prefrontal cortex (Cavanna and Trimble 2006), this visual cortex/ precuneus FC is likely part of a system involved in the regulation of visual attention (Lauritzen et al 2009)a system that may be affected by blast mTBI (Graner et al 2013). The precuneus, per se, has shown both reduction in resting cerebral blood flow (Kim et al 2010) and decreased regional volume (Zhou et al 2013) as a function of severity of TBI, conditions that could contribute to current findings of reduced V1/precuneus FC with blast mTBI severity.…”