Neuroimaging of traumatic brain injury in military personnel: An overview

Longitudinal analysis highlights structural changes in grey- and white-matter within military personnel exposed to blast

OBJECTIVE

The purpose of this study was to determine whether gray matter volume and diffusion-based metrics in associated white matter changed in breachers who had neuroimaging performed at two timepoints. A secondary purpose was to compare these changes in a group who had a one-year interval between their imaging timepoints to a group that had a two-year interval between imaging.

METHODS

Between timepoints, clusters with significantly different gray matter volume were used as seeds for reconstruction of associated structural networks using diffusion metrics.

RESULTS

Of 92 eligible participants, 62 had imaging at two timepoints, 36 with a one-year interval between scans and 26 with a two-year interval between scans. A significant effect of time was documented in the midcingulate cortex, but there was no effect of timepoint (1 versus 2 years). The associated white matter in this cluster had three regions with differences in fractional anisotropy compared to baseline, while there was no effect of timepoint (1 versus 2 years).

CONCLUSIONS

This study provides preliminary evidence that military personnel involved in repetitive exposure to sub-concussive blast overpressures may experience changes to both gray matter and white matter structures.

Military-related mild traumatic brain injury: clinical characteristics, advanced neuroimaging, and molecular mechanisms

Mild traumatic brain injury (mTBI) is a significant health burden among military service members. Although mTBI was once considered relatively benign compared to more severe TBIs, a growing body of evidence has demonstrated the devastating neurological consequences of mTBI, including chronic post-concussion symptoms and deficits in cognition, memory, sleep, vision, and hearing. The discovery of reliable biomarkers for mTBI has been challenging due to under-reporting and heterogeneity of military-related mTBI, unpredictability of pathological changes, and delay of post-injury clinical evaluations. Moreover, compared to more severe TBI, mTBI is especially difficult to diagnose due to the lack of overt clinical neuroimaging findings. Yet, advanced neuroimaging techniques using magnetic resonance imaging (MRI) hold promise in detecting microstructural aberrations following mTBI. Using different pulse sequences, MRI enables the evaluation of different tissue characteristics without risks associated with ionizing radiation inherent to other imaging modalities, such as X-ray-based studies or computerized tomography (CT). Accordingly, considering the high morbidity of mTBI in military populations, debilitating post-injury symptoms, and lack of robust neuroimaging biomarkers, this review (1) summarizes the nature and mechanisms of mTBI in military settings, (2) describes clinical characteristics of military-related mTBI and associated comorbidities, such as post-traumatic stress disorder (PTSD), (3) highlights advanced neuroimaging techniques used to study mTBI and the molecular mechanisms that can be inferred, and (4) discusses emerging frontiers in advanced neuroimaging for mTBI. We encourage multi-modal approaches combining neuropsychiatric, blood-based, and genetic data as well as the discovery and employment of new imaging techniques with big data analytics that enable accurate detection of post-injury pathologic aberrations related to tissue microstructure, glymphatic function, and neurodegeneration. Ultimately, this review provides a foundational overview of military-related mTBI and advanced neuroimaging techniques that merit further study for mTBI diagnosis, prognosis, and treatment monitoring.

Co-administration of Nanowired Oxiracetam and Neprilysin with Monoclonal Antibodies to Amyloid Beta Peptide and p-Tau Thwarted Exacerbation of Brain Pathology in Concussive Head Injury at Hot Environment

Environmental temperature adversely affects the outcome of concussive head injury (CHI)-induced brain pathology. Studies from our laboratory showed that animals reared at either cold environment or at hot environment exacerbate brain pathology following CHI. Our previous experiments showed that nanowired delivery of oxiracetam significantly attenuated CHI-induced brain pathology and associated neurovascular changes. Military personnel are the most susceptible to CHI caused by explosion, blasts, missile or blunt head trauma leading to lifetime functional and cognitive impairments affecting the quality of life. Severe CHI leads to instant death and/or lifetime paralysis. Military personnel engaged in combat operations are often subjected to extreme high or low environmental temperature zones across the globe. Thus, further exploration of novel therapeutic agents at cold or hot ambient temperatures following CHI are the need of the hour. CHI is also a major risk factor for developing Alzheimer's disease by enhancing amyloid beta peptide deposits in the brain. In this review, effect of hot environment on CHI-induced brain pathology is discussed. In addition, whether nanodelivery of oxiracetam together with neprilysin and monoclonal antibodies (mAb) to amyloid beta peptide and p-tau could lead to superior neuroprotection in CHI is explored. Our results show that co-administration of oxiracetam with neprilysin and mAb to AβP and p-tau significantly induced superior neuroprotection following CHI in hot environment, not reported earlier.

Neuroprotective Effects of Nanowired Delivery of Cerebrolysin with Mesenchymal Stem Cells and Monoclonal Antibodies to Neuronal Nitric Oxide Synthase in Brain Pathology Following Alzheimer's Disease Exacerbated by Concussive Head Injury

Concussive head injury (CHI) is one of the major risk factors in developing Alzheimer's disease (AD) in military personnel at later stages of life. Breakdown of the blood-brain barrier (BBB) in CHI leads to extravasation of plasma amyloid beta protein (ΑβP) into the brain fluid compartments precipitating AD brain pathology. Oxidative stress in CHI or AD is likely to enhance production of nitric oxide indicating a role of its synthesizing enzyme neuronal nitric oxide synthase (NOS) in brain pathology. Thus, exploration of the novel roles of nanomedicine in AD or CHI reducing NOS upregulation for neuroprotection are emerging. Recent research shows that stem cells and neurotrophic factors play key roles in CHI-induced aggravation of AD brain pathologies. Previous studies in our laboratory demonstrated that CHI exacerbates AD brain pathology in model experiments. Accordingly, it is quite likely that nanodelivery of NOS antibodies together with cerebrolysin and mesenchymal stem cells (MSCs) will induce superior neuroprotection in AD associated with CHI. In this review, co-administration of TiO2 nanowired cerebrolysin - a balanced composition of several neurotrophic factors and active peptide fragments, together with MSCs and monoclonal antibodies (mAb) to neuronal NOS is investigated for superior neuroprotection following exacerbation of brain pathology in AD exacerbated by CHI based on our own investigations. Our observations show that nanowired delivery of cerebrolysin, MSCs and neuronal NOS in combination induces superior neuroprotective in brain pathology in AD exacerbated by CHI, not reported earlier.

Military traumatic brain injury: a challenge straddling neurology and psychiatry

Military psychiatry, a new subcategory of psychiatry, has become an invaluable, intangible effect of the war. In this review, we begin by examining related military research, summarizing the related epidemiological data, neuropathology, and the research achievements of diagnosis and treatment technology, and discussing its comorbidity and sequelae. To date, advances in neuroimaging and molecular biology have greatly boosted the studies on military traumatic brain injury (TBI). In particular, in terms of pathophysiological mechanisms, several preclinical studies have identified abnormal protein accumulation, blood-brain barrier damage, and brain metabolism abnormalities involved in the development of TBI. As an important concept in the field of psychiatry, TBI is based on organic injury, which is largely different from many other mental disorders. Therefore, military TBI is both neuropathic and psychopathic, and is an emerging challenge at the intersection of neurology and psychiatry.

Development of a Semiautomated Search Tool to Identify Grading From Pathology Reports for Tumors of the CNS and Prostate Cancers

PURPOSE

This study demonstrates the functionality of semiautomated algorithms to classify cancer-specific grading from electronic pathology reports generated from military treatment facilities. Two Perl-based algorithms are validated to classify WHO grade for tumors of the CNS and Gleason grades for prostate cancer.

METHODS

Case-finding cohorts were developed using diagnostic codes and matched by unique identifiers to obtain pathology records generated in the Military Health System for active duty service members from 2013 to 2018. Perl-based algorithms were applied to classify document-based pathology reports to identify malignant CNS tumors and prostate cancer, followed by a hand-review process to determine accuracy of the algorithm classifications. Inter-rater reliability, sensitivity, specificity, positive predictive values (PPVs), and negative predictive values were computed following abstractor adjudication.

RESULTS

The high PPV for the Perl-based algorithms to classify CNS tumors (PPV > 98%) and prostate cancer (PPV > 99%) supports this approach to classify malignancies for cancer surveillance operations, mediated by a hand-reviewed semiautomated process to increase sensitivity by capturing ungraded cancers. Early detection was pronounced where 33.6% and 50.7% of malignant records retained a CNS WHO grade of II or a Gleason score of 6, respectively. Sensitivity metrics met criteria (> 75%) for brain (79.9%, 95% CI, 73.0 to 85.7) and prostate (96.7%, 95% CI, 94.9 to 98.0) cancers.

CONCLUSION

Semiautomated, document-based text classification using Perl coding successfully leveraged identification of WHO and Gleason grades to classify pathology records for CNS tumors and prostate cancer. The process is recommended for data quality initiatives to support cancer reporting functions, epidemiology, and research.

Methamphetamine exacerbates pathophysiology of traumatic brain injury at high altitude. Neuroprotective effects of nanodelivery of a potent antioxidant compound H-290/51

Military personnel are often exposed to high altitude (HA, ca. 4500-5000m) for combat operations associated with neurological dysfunctions. HA is a severe stressful situation and people frequently use methamphetamine (METH) or other psychostimulants to cope stress. Since military personnel are prone to different kinds of traumatic brain injury (TBI), in this review we discuss possible effects of METH on concussive head injury (CHI) at HA based on our own observations. METH exposure at HA exacerbates pathophysiology of CHI as compared to normobaric laboratory environment comparable to sea level. Increased blood-brain barrier (BBB) breakdown, edema formation and reductions in the cerebral blood flow (CBF) following CHI were exacerbated by METH intoxication at HA. Damage to cerebral microvasculature and expression of beta catenin was also exacerbated following CHI in METH treated group at HA. TiO2-nanowired delivery of H-290/51 (150mg/kg, i.p.), a potent chain-breaking antioxidant significantly enhanced CBF and reduced BBB breakdown, edema formation, beta catenin expression and brain pathology in METH exposed rats after CHI at HA. These observations are the first to point out that METH exposure in CHI exacerbated brain pathology at HA and this appears to be related with greater production of oxidative stress induced brain pathology, not reported earlier.

A Role for the Amygdala in Impairments of Affective Behaviors Following Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) results in chronic affective disorders such as depression, anxiety, and fear that persist up to years following injury and significantly impair the quality of life for patients. Although a great deal of research has contributed to defining symptoms of mild TBI, there are no adequate drug therapies for brain-injured individuals. Preclinical studies have modeled these deficits in affective behaviors post-injury to understand the underlying mechanisms with a view to developing appropriate treatment strategies. These studies have also unveiled sex differences that contribute to the varying phenotypes associated with each behavior. Although clinical and preclinical studies have viewed these behavioral deficits as separate entities with unique neurobiological mechanisms, mechanistic similarities suggest that a novel approach is needed to advance research on drug therapy. This review will discuss the circuitry involved in the expression of deficits in affective behaviors following mild TBI in humans and animals and provide evidence that the manifestation of impairment in these behaviors stems from an amygdala-dependent emotional processing deficit. It will highlight mechanistic similarities between these different types of affective behaviors that can potentially advance mild TBI drug therapy by investigating treatments for the deficits in affective behaviors as one entity, requiring the same treatment.

Activation of brain regions using task-state FMRI in patients with mild traumatic brain injury: a meta-analysis

Activation likelihood estimation meta-analysis was performed to examine the activation characteristics of cognition-related brain regions in patients with mild traumatic brain injury (mTBI). The databases PubMed, Ovid, Cochrane Library, Google Scholar, CNKI, WFSD, and VIP were systematically searched. The software Ginger-ALE 3.0.2 was used for coordinate unification and meta-analysis. Seven studies with a total of 314 subjects were included. Meta-analysis results indicated that compared with healthy subjects, mTBI patients had enhanced activation in the left anterior angular gyrus, left occipital joint visual, left midbrain, right temporal angular gyrus, right cerebellar tonsil, left frontal insula, and right inferior frontal gyrus. mTBI patients had attenuated activation in the right dorsolateral prefrontal lobe, left cerebellar anterior lobe, left dorsolateral prefrontal lobe, right middle frontal gyrus, right posterior cingulate gyrus, left joint visual, left supramarginal gyrus, left middle frontal gyrus, right precuneus, left dorsolateral prefrontal cortex, right frontal eye field, right lower parietal gyrus, corpus callosum, right frontal pole region, and left prefrontal lobe. Further joint analysis revealed that the dorsolateral prefrontal lobe of the right middle frontal gyrus was a region of attenuated co-activation. The dorsolateral prefrontal lobe of the right middle frontal gyrus showing attenuated activation was the main brain region distinguishing mTBI patients from healthy subjects. Cognitive deficits could be associated with attenuated activation in the dorsolateral prefrontal lobe of the right middle frontal gyrus, which could be due to a decline in the recruitment ability of the neural network involved in controlling attention.