Evidence of disrupted functional connectivity in the brain after combat-related blast injury

Article (PDF Available)inNeuroImage 54 Suppl 1(1):S21-9 · January 2011with153 Reads
DOI: 10.1016/j.neuroimage.2010.09.007 · Source: PubMed
Non-impact blast-related mild traumatic brain injury (mTBI) appears to be present in soldiers returning from deployments to Afghanistan and Iraq. Although mTBI typically results in cognitive deficits that last less than a month, there is evidence that disrupted coordination of brain activity can persist for at least several months following injury (Thatcher et al., 1989, 2001). In the present study we examined whether neural communication may be affected in soldiers months after blast-related mTBI, and whether coordination of neural function is associated with underlying white matter integrity. The investigation included an application of a new time-frequency based method for measuring electroencephalogram (EEG) phase synchronization (Aviyente et al., 2010) as well as fractional anisotropy measures of axonal tracts derived from diffusion tensor imaging (DTI). Nine soldiers who incurred a blast-related mTBI during deployments to Afghanistan or Iraq were compared with eight demographically similar control subjects. Despite an absence of cognitive deficits, the blast-related mTBI group exhibited diminished EEG phase synchrony of lateral frontal sites with contralateral frontal brain regions suggesting diminished interhemispheric coordination of brain activity as a result of blast injury. For blast injured (i.e., blast-related mTBI) soldiers we found that EEG phase synchrony was associated with the structural integrity of white matter tracts of the frontal lobe (left anterior thalamic radiations and the forceps minor including the anterior corpus callosum). Analyses revealed that diminished EEG phase synchrony was not the consequence of combat-stress symptoms (e.g., post-traumatic stress and depression) and commonly prescribed medications. Results provide evidence for poor coordination of frontal neural function after blast injury that may be the consequence of damaged anterior white matter tracts.

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Available from: Edward Bernat
    • "In subacute civilian mTBI (i.e., 3 to 5 months post-injury), FC within the Default Mode Network (DMN) was decreased, while connectivity between the DMN and regions with which it might normally be anticorrelated (e.g., task-related network which includes the lateral prefrontal cortex) was increased (Mayer et al., 2011; Sours et al., 2013). Disruption of electrophysiological signal within the lateral frontal lobes and the WM networks subserving them in veterans from the Iraqi and Afghanistan wars with mTBI (Sponheim et al., 2011) suggests FC of the DMN may also be disrupted in this population. "
    [Show abstract] [Hide abstract] ABSTRACT: Objectives: Blast explosions are the most frequent mechanism of traumatic brain injury (TBI) in recent wars, but little is known about their long-term effects. Methods: Functional connectivity (FC) was measured in 17 veterans an average of 5.46 years after their most serious blast related TBI, and in 15 demographically similar veterans without TBI or blast exposure. Subcortical FC was measured in bilateral caudate, putamen, and globus pallidus. The default mode and fronto-parietal networks were also investigated. Results: In subcortical regions, between-groups t tests revealed altered FC from the right putamen and right globus pallidus. However, following analysis of covariance (ANCOVA) with age, depression (Center for Epidemiologic Studies Depression Scale), and posttraumatic stress disorder symptom (PTSD Checklist – Civilian version) measures, significant findings remained only for the right globus pallidus with anticorrelation in bilateral temporal occipital fusiform cortex, occipital fusiform gyrus, lingual gyrus, and cerebellum, as well as the right occipital pole. No group differences were found for the default mode network. Although reduced FC was found in the fronto-parietal network in the TBI group, between-group differences were nonsignificant after the ANCOVA. Conclusions: FC of the globus pallidus is altered years after exposure to blast related TBI. Future studies are necessary to explore the trajectory of changes in FC in subcortical regions after blast TBI, the effects of isolated versus repetitive blast-related TBI, and the relation to long-term outcomes in veterans. ( JINS , 2016, 22 , 1–12)
    Full-text · Article · Apr 2016
    • " which connect lobes within each hemisphere , were also found to be damaged in six studies (Davenport et al., 2012; Matthews et al., 2012; Morey et al., 2013; Petrie et al., 2014; Taber et al., 2015; Yeh et al., 2014). The CC plays a significant role in interhemispheric communication , whereas the SLF is responsible for intrahemispheric connection. Sponheim et al. (2011) reported a correlation between white matter integrity in frontal brain regions as measured by FA and electroencephalogram (EEG) phase synchrony, suggesting that coordination in frontal areas is reduced after blast exposure. In one study, however, the findings showed greater white matter damage in the middle cerebellar peduncles and righ"
    [Show abstract] [Hide abstract] ABSTRACT: Mild traumatic brain injury (mTBI) has been labeled the “signature injury” of the wars in Iraq and Afghanistan, and approximately half of mTBIs that occur in combat are due to explosive blasts. The rapid change in pressure that results from an explosion may make blast injury distinct from mTBI due to other causes. Persistent symptoms following blast mTBI may be related to white matter damage that has recently been identified using innovative neuroimaging techniques, such as diffusion tensor imaging (DTI). By comparing the DTI findings in blast mTBI to studies of the effects of white matter structure on functional performance, hypotheses can be developed about the implications of the injury for engagement in occupation. Incorporation of neuroscience evidence about the effects of blast mTBI may provide objective evidence of underlying damage that correlates with deficits in occupational engagement of military service members and veterans who are affected by these injuries.
    Full-text · Article · Dec 2015
    • "Additionally, Bogdanova and Verfaellie (2012) report that an estimated 15% to 23% of OEF and OIF personnel have experienced a TBI and that mild traumatic brain injury (mTBI) is the most common type of traumatic brain injury among OEF/ OIF military personnel (Fischer, 2014). Most of the reports of the effects of primary blast exposure on the human brain detail damage related to direct head impact (MacDonald et al. 2011; Sponheim et al. 2011). Thus, the effects of mTBI caused by blast injury and their subsequent effects on language and cognition (i.e., cognitive-communication disorders) have received increased clinical and research interest. "
    [Show abstract] [Hide abstract] ABSTRACT: Conflicts in Iraq and Afghanistan have resulted in numerous U.S. military combat casualties caused by improvised explosive devices (IEDs). Blast injuries involving IEDs and other explosive devices can result in injuries to the head, face, neck and chest, all parts of the body housing important structures necessary for communication. Mild traumatic brain injury is the signature wound of the Iraq and Afghanistan wars. Blast-induced injuries can produce a variety of communication disorders and can negatively impact language, cognition, speech and voice as well as the auditory system. By reviewing the current literature, we explain how explosive devices can result in communication and related disorders (i.e., cognitive-linguistic, voice, swallowing). We also note that presently, speech-language pathologists are seldom involved in the initial part of recovery and diagnosis of blast-wave survivors and only involved when rehabilitation services are required. Because post-traumatic stress disorder and mild traumatic brain injury have similar symptoms, misdiagnosis can occur, and incorrect treatments applied. Thus, we contend that speech-language pathologists are trained professionals who should be involved in the diagnosis and treatment of blast-wave survivors, not only when rehabilitation services are needed, but also during the initial stages post-injury. Continued research should involve case studies as well as short-term and long-term studies of blast-wave survivors and their impairments in communication, as current research mostly focuses on mild traumatic brain injury.
    Full-text · Article · Aug 2015 · Journal of Occupational Science
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