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.

Keywords: blast injuries; functional magnetic resonance imaging; military injury; review; traumatic brain injury.

Figure 1

Working memory tasks typically show activation in the bilateral and superior frontal cortex as well as in parts of the superior bilateral parietal cortex. The highlighted regions showed significantly different activation between an individual performing a 1-Back task versus a 2-Back task.

Figure 2

The default mode network (DMN) includes regions in the medial pre-frontal cortex, precuneus, and bilateral parietal cortex. Highlighted regions in the images were all correlated with the same component from an independent component analysis of an individual’s resting state fMRI data. The color scale reflects correlation z-scores, with a lower threshold of z = 3.