Association of Blast Exposure in Military Breaching with Intestinal Permeability Blood Biomarkers Associated with Leaky Gut.

Injuries and subclinical effects from exposure to blasts are of significant concern in military operational settings, including tactical training, and are associated with self-reported concussion-like symptomology and physiological changes such as increased intestinal permeability (IP), which was investigated in this study. Time-series gene expression and IP biomarker data were generated from "breachers" exposed to controlled, low-level explosive blast during training. Samples from 30 male participants at pre-, post-, and follow-up blast exposure the next day were assayed via RNA-seq and ELISA. A battery of symptom data was also collected at each of these time points that acutely showed elevated symptom reporting related to headache, concentration, dizziness, and taking longer to think, dissipating ~16 h following blast exposure. Evidence for bacterial translocation into circulation following blast exposure was detected by significant stepwise increase in microbial diversity (measured via alpha-diversity p = 0.049). Alterations in levels of IP protein biomarkers (i.e., Zonulin, LBP, Claudin-3, I-FABP) assessed in a subset of these participants (n = 23) further evidenced blast exposure associates with IP. The observed symptom profile was consistent with mild traumatic brain injury and was further associated with changes in bacterial translocation and intestinal permeability, suggesting that IP may be linked to a decrease in cognitive functioning. These preliminary findings show for the first time within real-world military operational settings that exposures to blast can contribute to IP.

Field assessment of acute auditory responses to environmental exposures in close quarters tactics training.

OBJECTIVE: The purpose of this study was to evaluate auditory performance of military instructors as part of a training course involving noise and blast exposure. Boothless audiometry was used to estimate the test-retest reliability of the auditory measures under realistic field conditions and to determine risk of acute auditory injury during standard training practices. DESIGN AND STUDY SAMPLE: Thirteen U.S. Marine instructors participated in study activities. An audiologic testing suite embedded in a noise-attenuating headset was used to test various tone detection tasks on subjects after exposure. Acoustic exposures were captured with sound level meters. RESULTS: Boothless audiometry provide highly repeatable results for various tests of auditory performance in the field environment. In this test population, changes in auditory performance pre- and post-noise exposure were minimal for most measures. The notable exception was binaural (NoSπ) tone detection, which showed significant degradations both as a function of pre- and post-noise exposure on the same day and as a result of cumulative noise exposure over the period of the study. CONCLUSIONS: Study outcomes are consistent with prior laboratory and epidemiological work and suggest a link between the binaural processes required for NoSπ detection and the hearing-related issues reported by blast-exposed service members.

Methodology of the INVestigating traIning assoCiated blasT pAthology (INVICTA) study.

BACKGROUND: Subconcussive blast exposure during military training has been the subject of both anecdotal concerns and reports in the medical literature, but prior studies have often been small and have used inconsistent methods. METHODS: This paper presents the methodology employed in INVestigating traIning assoCiated blasT pAthology (INVICTA) to assess a wide range of aspects of brain function, including immediate and delayed recall, gait and balance, audiologic and oculomotor function, cerebral blood flow, brain electrical activity and neuroimaging and blood biomarkers. RESULTS: A number of the methods employed in INVICTA are relatively easy to reproducibly utilize, and can be completed efficiently, while other measures require greater technical expertise, take longer to complete, or may have logistical challenges. CONCLUSIONS: This presentation of methods used to assess the impact of blast exposure on the brain is intended to facilitate greater uniformity of data collection in this setting, which would enable comparison between different types of blast exposure and environmental circumstances, as well as to facilitate meta-analyses and syntheses across studies.

Interleukin-6 is associated with acute concussion in military combat personnel.

BACKGROUND: Concussion is the most common type of TBI, yet reliable objective measures related to these injuries and associated recovery processes remain elusive, especially in military personnel. The purpose of this study was to characterize the relationship between cytokines and recovery from acute brain injury in active duty service members. Inflammatory cytokines (IL-6, IL-10, and TNFα) were measured acutely in blood samples within 8 h following a medically diagnosed concussion and then 24 h later. METHODS: Participants (n = 94) were categorized into two groups: 1) military personnel who sustained provider-diagnosed concussion, without other major medical diagnosis (n = 45) and 2) healthy control participants in the same deployment environment who did not sustain concussion or other illness or injuries (n = 49). IL-6, IL-10, and TNFα concentrations were measured using an ultrasensitive single-molecule enzyme-linked immunosorbent assay. Differences in cytokine levels between concussed and healthy groups were evaluated at two time points (time point 1 ≤ 8 h after injury; time point 2 = 24 h following time point 1). RESULTS: At time point 1, IL-6 median (IQR) concentrations were 2.62 (3.62) in the concussed group, which was greater compared to IL-6 in the healthy control group (1.03 (0.90); U = 420.00, z = - 5.12, p < 0.001). Compared to healthy controls, the concussed group did not differ at time point 1 in IL-10 or TNFα concentrations (p's > 0.05). At time point 2, no differences were detected between concussed and healthy controls for IL-6, IL-10, or TNFα (p's > 0.05). The median difference between time points 1 and 2 were compared between the concussed and healthy control groups for IL-6, IL-10, and TNFα. Change in IL-6 across time was greater for the concussed group than healthy control (- 1.54 (3.12); U = 315.00, z = - 5.96, p < 0.001), with no differences between groups in the change of IL-10 or TNFα (p's > 0.05). CONCLUSION: Reported here is a significant elevation of IL-6 levels in concussed military personnel less than 8 h following injury. Future studies may examine acute and chronic neurological symptomology associated with inflammatory cytokine levels, distinguish individuals at high risk for developing neurological complications, and identify underlying biological pathways to mitigate inflammation and improve outcomes.

Blast exposure results in tau and neurofilament light chain changes in peripheral blood.

OBJECTIVES: To evaluate how blast exposure impacts peripheral biomarkers.in military personnel enrolled in 10-day blast training. METHODS: On day 7, 21 military personnel experienced peak overpressure <2 pounds per square inch (psi); while 29 military personnel experienced peak overpressure ≥5 psi. Blood samples were collected each day to measure changes in amyloid beta (Aß), neurofilament light chain (NFL), and tau concentrations. RESULTS: Within 24 hours following exposure ≥5 psi, the ≥5 psi group had lower Aß42 (p = .004) and NFL (p < .001) compared to the <2 psi group and lower Aß42 (9.35%) and NFL (22.01%) compared to baseline. Twenty-four hours after ≥5 psi exposure, the ≥5 psi group had lower tau (p < .001) and NFL (p < .001) compared to the <2 psi group and baseline. Seventy-two hours after exposure ≥5 psi, tau increased in the ≥5 psi group compared to the <2 psi group (p = .02) and baseline. The tau:Aß42 ratio 24 hours after blast (p = .012), and the Aß40:Aß42 ratio 48 hours after blast (p = .04) differed in the ≥5 psi group compared to the <2 psi group. CONCLUSIONS: These findings provide an initial report of acute alterations in biomarker concentrations following blast exposure.

Moderate blast exposure results in increased IL-6 and TNFα in peripheral blood.

A unique cohort of military personnel exposed to isolated blast was studied to explore acute peripheral cytokine levels, with the aim of identifying blast-specific biomarkers. Several cytokines, including interleukin (IL) 6, IL-10 and tumor necrosis factor alpha (TNFα) have been linked to pre-clinical blast exposure, but remained unstudied in clinical blast exposure. To address this gap, blood samples from 62 military personnel were obtained at baseline, and daily, during a 10-day blast-related training program; changes in the peripheral concentrations of IL-6, IL-10 and TNFα were evaluated using an ultrasensitive assay. Two groups of trainees were matched on age, duration of military service, and previous history of blast exposure(s), resulting in moderate blast cases and no/low blast controls. Blast exposures were measured using helmet sensors that determined the average peak pressure in pounds per square inch (psi). Moderate blast cases had significantly elevated concentrations of IL-6 (F1,60=18.81, p<0.01) and TNFα (F1,60=12.03, p<0.01) compared to no/low blast controls; levels rebounded to baseline levels the day after blast. On the day of the moderate blast exposure, the extent of the overpressure (psi) in those exposed correlated with IL-6 (r=0.46, p<0.05) concentrations. These findings indicate that moderate primary blast exposure results in changes, specifically acute and transient increases in peripheral inflammatory markers which may have implications for neuronal health.

Rhythmic alternating patterns of brain activity distinguish rapid eye movement sleep from other states of consciousness.

Rapid eye movement (REM) sleep constitutes a distinct "third state" of consciousness, during which levels of brain activity are commensurate with wakefulness, but conscious awareness is radically transformed. To characterize the temporal and spatial features of this paradoxical state, we examined functional interactions between brain regions using fMRI resting-state connectivity methods. Supporting the view that the functional integrity of the default mode network (DMN) reflects "level of consciousness," we observed functional uncoupling of the DMN during deep sleep and recoupling during REM sleep (similar to wakefulness). However, unlike either deep sleep or wakefulness, REM was characterized by a more widespread, temporally dynamic interaction between two major brain systems: unimodal sensorimotor areas and the higher-order association cortices (including the DMN), which normally regulate their activity. During REM, these two systems become anticorrelated and fluctuate rhythmically, in reciprocally alternating multisecond epochs with a frequency ranging from 0.1 to 0.01 Hz. This unique spatiotemporal pattern suggests a model for REM sleep that may be consistent with its role in dream formation and memory consolidation.

Relation of repeated low-level blast exposure with symptomology similar to concussion.

OBJECTIVE: To investigate anecdotal reports suggesting that repeated exposure to low-level explosive blast has myriad health impacts, including an array of neurological effects. PARTICIPANTS: A total of 184 anonymous survey respondents from military and nonmilitary law enforcement populations (135 exposed to occupational blast and 49 controls). DESIGN: Survey of self-reported history of occupational exposure to repeated low-level blast (breaching blast) and symptomology similar to concussion. RESULTS: Findings suggest that number and severity of symptoms increase with history of chronic blast exposure (F = 18.26, P < .001) and that symptoms can interfere with daily activity (t = 2.60, P = .010). CONCLUSION: Given the prevalence of repeated exposure to blast among some military and civilian law enforcement occupations, the results of this survey study support a role for blast surveillance programs as well as continued research on health impacts of low-level repeated blast exposure.

Comparative Performance of Three Eye-Tracking Devices in Detection of Mild Traumatic Brain Injury in Acute Versus Chronic Subject Populations.

INTRODUCTION: Presently, traumatic brain injury (TBI) triage in field settings relies on symptom-based screening tools such as the updated Military Acute Concussion Evaluation. Objective eye-tracking may provide an alternative means of neurotrauma screening due to sensitivity to neurotrauma brain-health changes. Previously, the US Army Medical Research and Development Command Non-Invasive NeuroAssessment Devices (NINAD) Integrated Product Team identified 3 commercially available eye-tracking devices (SyncThink EYE-SYNC, Oculogica EyeBOX, NeuroKinetics IPAS) as meeting criteria toward being operationally effective in the detection of TBI in service members. We compared these devices to assess their relative performance in the classification of mild traumatic brain injury (mTBI) subjects versus normal healthy controls. MATERIALS AND METHODS: Participants 18 to 45 years of age were assigned to Acute mTBI, Chronic mTBI, or Control group per study criteria. Each completed a TBI assessment protocol with all 3 devices counterbalanced across participants. Acute mTBI participants were tested within 72 hours following injury whereas time since last injury for the Chronic mTBI group ranged from months to years. Discriminant analysis was undertaken to determine device classification performance in separating TBI subjects from controls. Area Under the Curves (AUCs) were calculated and used to compare the accuracy of device performance. Device-related factors including data quality, the need to repeat tests, and technical issues experienced were aggregated for reporting. RESULTS: A total of 63 participants were recruited as Acute mTBI subjects, 34 as Chronic mTBI subjects, and 119 participants without history of TBI as controls. To maximize outcomes, poorer quality data were excluded from analysis using specific criteria where possible. Final analysis utilized 49 (43 male/6 female, mean [x̅] age = 24.3 years, SD [s] = 5.1) Acute mTBI subjects, and 34 (33 male/1 female, x̅ age = 38.8 years, s = 3.9) Chronic mTBI subjects were age- and gender-matched as closely as possible with Control subjects. AUCs obtained with 80% of total dataset ranged from 0.690 to 0.950 for the Acute Group and from 0.753 to 0.811 for the Chronic mTBI group. Validation with the remaining 20% of dataset produced AUCs ranging from 0.600 to 0.750 for Acute mTBI group and 0.490 to 0.571 for the Chronic mTBI group. CONCLUSIONS: Potential eye-tracking detection of mTBI, per training model outcomes, ranged from acceptable to excellent for the Acute mTBI group; however, it was less consistent for the Chronic mTBI group. The self-imposed targeted performance (AUC of 0.850) appears achievable, but further device improvements and research are necessary. Discriminant analysis models differed for the Acute versus Chronic mTBI groups, suggesting performance differences in eye-tracking. Although eye-tracking demonstrated sensitivity in the Chronic group, a more rigorous and/or longitudinal study design is required to evaluate this observation. mTBI injuries were not controlled for this study, potentially reducing eye-tracking assessment sensitivity. Overall, these findings indicate that while eye-tracking remains a viable means of mTBI screening, device-specific variability in data quality, length of testing, and ease of use must be addressed to achieve NINAD objectives and DoD implementation.

Study protocol: Identifying transcriptional regulatory alterations of chronic effects of blast and disturbed sleep in United States Veterans.

Injury related to blast exposure dramatically rose during post-911 era military conflicts in Iraq and Afghanistan. Mild traumatic brain injury (mTBI) is among the most common injuries following blast, an exposure that may not result in a definitive physiologic marker (e.g., loss of consciousness). Recent research suggests that exposure to low level blasts and, more specifically repetitive blast exposure (RBE), which may be subconcussive in nature, may also impact long term physiologic and psychological outcomes, though findings have been mixed. For military personnel, blast-related injuries often occur in chaotic settings (e.g., combat), which create challenges in the immediate assessment of related-injuries, as well as acute and post-acute sequelae. As such, alternate means of identifying blast-related injuries are needed. Results from previous work suggest that epigenetic markers, such as DNA methylation, may provide a potential stable biomarker of cumulative blast exposure that can persist over time. However, more research regarding blast exposure and associations with short- and long-term sequelae is needed. Here we present the protocol for an observational study that will be completed in two phases: Phase 1 will address blast exposure among Active Duty Personnel and Phase 2 will focus on long term sequelae and biological signatures among Veterans who served in the recent conflicts and were exposed to repeated blast events as part of their military occupation. Phase 2 will be the focus of this paper. We hypothesize that Veterans will exhibit similar differentially methylated regions (DMRs) associated with changes in sleep and other psychological and physical metrics, as observed with Active Duty Personnel. Additional analyses will be conducted to compare DMRs between Phase 1 and 2 cohorts, as well as self-reported psychological and physical symptoms. This comparison between Service Members and Veterans will allow for exploration regarding the natural history of blast exposure in a quasi-longitudinal manner. Findings from this study are expected to provide additional evidence for repetitive blast-related physiologic changes associated with long-term neurobehavioral symptoms. It is expected that findings will provide foundational data for the development of effective interventions following RBE that could lead to improved long-term physical and psychological health.

Acute Hearing Deficits associated with Weapons Exposure in Section 734 Blast Overpressure Study (BOS).

INTRODUCTION: This prospective, multi-site, observational study describes ongoing efforts in support of the Fiscal Year 2018 National Defense Authorization Act (NDAA) Section 734 Blast Overpressure Study (BOS) to identify the acute effects impulse and blast exposure have on hearing abilities of the Warfighter in various military training environments. MATERIALS AND METHODS: Hearing thresholds, a binaural tone detection task, and auditory symptoms were collected before and immediately following weapons exposure across nine military training environments from January 2020 to October 2022. An additional 25 non-exposed control participants also completed the behavioral test battery. A boothless audiometer was used to measure hearing ability in the field. Sound level meters were attached on-body to record the exposure environment throughout training. RESULTS: Mean threshold change for the blast-exposed group was worse than the control group. Of the 188 blast-exposed participants, 23 experienced a temporary threshold shift (TTS) acutely after exposure. A decrease in binaural tone detection performance and increased symptom severity was found when comparing blast-exposed participants with a TTS versus those without a significant change in hearing. A complex but consistent relationship between measured exposure level (LAeq8hr) and the magnitude of the resulting TTS is suggested in the available data. CONCLUSIONS: Recent discussions on Section 734 studies examining the effects of repetitive blast exposure have indicated that hearing-related issues were a critical problem that needed additional research. Study outcomes provide highly repeatable results across various weapons systems with hazardous blast exposure. This standardized set of hearing assessment tools for evaluating acute effects of noise under field conditions has been critically important in improving our understanding of TTS in prospective human subject research.

Fiscal Year 2018 National Defense Authorization Act, Section 734, Weapon Systems Line of Inquiry: Overview and Blast Overpressure Tool-A Module for Human Body Blast Wave Exposure for Safer Weapons Training.

INTRODUCTION: Experiences by service members in recent conflicts and training environments illuminate concerns about the possible effects of blast overpressure (BOP) exposure on brain health. Section 734 of the National Defense Authorization Act for Fiscal Year (FY) 2018 (Public Law 115-91) requires that the Secretary of Defense conducts a longitudinal medical study on blast pressure exposure of members of the Armed Forces during combat and training, and the Assistant Secretary of Defense for Health Affairs was assigned responsibility for fulfilling requirements. The study's goal is to improve DoD's understanding of the impact of BOP exposure from weapon systems on service members' brain health and inform policy for risk mitigation, unit readiness, and health care decisions. This article focuses on the activities of the Weapon Systems Line of Inquiry (LOI) and the development of a prototype BOP Tool. MATERIALS AND METHODS: The DoD established the Section 734 Workgroup, which developed a program structure with five LOIs. The Weapon Systems LOI coordinated, collated, and analyzed information on BOP resulting from heavy weapons and blast events to inform strategies, and accounted for emerging research on health effects and performance. Ongoing research was leveraged to develop a BOP Tool as a standalone module and for integration into the Range Managers Toolkit. RESULTS: The effort identified opportunities for the DoD to improve the clarity of communications about BOP exposure, risk, and safety; establish methods to leverage emerging research; and develop a prototype BOP Tool to predict exposure loads when firing heavy weapons in training. CONCLUSIONS: It is recommended that the DoD revises requirements and policy to improve and standardize safety guidance throughout research, development, testing, and evaluation; acquisition; and training. The validated BOP Tool allows users to generate a scenario to predict BOP exposure and allows service members to modify them during planning for safer training.

Decoupling of the brain's default mode network during deep sleep.

The recent discovery of a circuit of brain regions that is highly active in the absence of overt behavior has led to a quest for revealing the possible function of this so-called default-mode network (DMN). A very recent study, finding similarities in awake humans and anesthetized primates, has suggested that DMN activity might not simply reflect ongoing conscious mentation but rather a more general form of network dynamics typical of complex systems. Here, by performing functional MRI in humans, it is shown that a natural, sleep-induced reduction of consciousness is reflected in altered correlation between DMN network components, most notably a reduced involvement of frontal cortex. This suggests that DMN may play an important role in the sustenance of conscious awareness.

Elevations in Tumor Necrosis Factor Alpha and Interleukin 6 From Neuronal-Derived Extracellular Vesicles in Repeated Low-Level Blast Exposed Personnel.

Objective: The purpose of this pilot study was to determine if military service members with histories of hundreds to thousands of low-level blast exposures (i. e., experienced breachers) had different levels of serum and neuronal-derived extracellular vesicle (EV) concentrations of interleukin (IL)-6, IL-10, and tumor necrosis factor alpha (TNFα), compared to matched controls, and if these biomarkers related to neurobehavioral symptoms. Methods: Participants were experienced breachers (n = 20) and matched controls without blast exposures (n = 14). Neuronal-derived EVs were isolated from serum and identified with mouse anti-human CD171. Serum and neuronal-derived EVs were analyzed for IL-6, IL-10, and TNFα using an ultra-sensitive assay. Results: Serum TNFα concentrations were decreased in breachers when compared to control concentrations (p < 0.01). There were no differences in serum concentrations of IL-6, IL-10, or the IL-6/IL-10 ratio between breachers and controls (p's > 0.01). In neuronal-derived EVs, TNFα and IL-6 levels were increased in breachers compared to controls (p's < 0.01), and IL-10 levels were decreased in the breacher group compared to controls (p < 0.01). In breachers the IL-6/IL-10 ratio in neuronal-derived EVs was higher compared to controls, which correlated with higher total Rivermead Post-concussion Questionnaire (RPQ) scores (p's < 0.05). Conclusions: These findings suggest that exposure of personnel to high numbers of low-level blast over a career may result in enduring central inflammation that is associated with chronic neurological symptoms. The data also suggest that peripheral markers of inflammation are not necessarily adequate surrogates for central neuroinflammation.

A Pilot Study of Whole-Blood Transcriptomic Analysis to Identify Genes Associated with Repetitive Low-Level Blast Exposure in Career Breachers.

Repetitive low-level blast exposure is one of the major occupational health concerns among US military service members and law enforcement. This study seeks to identify gene expression using microRNA and RNA sequencing in whole-blood samples from experienced breachers and unexposed controls. We performed experimental RNA sequencing using Illumina's HiSeq 2500 Sequencing System, and microRNA analysis using NanoString Technology nCounter miRNA expression panel in whole-blood total RNA samples from 15 experienced breachers and 14 age-, sex-, and race-matched unexposed controls. We identified 10 significantly dysregulated genes between experienced breachers and unexposed controls, with FDR corrected <0.05: One upregulated gene, LINC00996 (long intergenic non-protein coding RNA 996); and nine downregulated genes, IGLV3-16 (immunoglobulin lambda variable 3-16), CD200 (CD200 molecule), LILRB5 (leukocyte immunoglobulin-like receptor B5), ZNF667-AS1 (ZNF667 antisense RNA 1), LMOD1 (leiomodin 1), CNTNAP2 (contactin-associated protein 2), EVPL (envoplakin), DPF3 (double PHD fingers 3), and IGHV4-34 (immunoglobulin heavy variable 4-34). The dysregulated gene expressions reported here have been associated with chronic inflammation and immune response, suggesting that these pathways may relate to the risk of lasting neurological symptoms following high exposures to blast over a career.

Comparison of Combat Gauze and TraumaStat in two severe groin injury models.

BACKGROUND: Fabric-like hemostatic dressings offer promise for hemorrhage control in noncompressible areas, especially given their similarity in form to standard gauze currently in use. Recently, two such products, Combat Gauze (CBG) and TraumaStat (TMS), were introduced. Their performance is evaluated in two vascular injury models. MATERIALS AND METHODS: The dressings were evaluated in anesthetized Yorkshire pigs, hemorrhaged by full transection of the femoral vasculature with 2 min free bleeding period (CBG = 6, TMS = 6) or by 4 mm femoral arterial puncture with 45 s free bleeding period (CBG = 8, TMS = 8). After injury, dressings were applied, followed by 5 min of manual compression and then 500 mL resuscitation fluid infused over 30 min. Vital signs, blood pressure, and blood loss were recorded throughout the 3-h experiment. Bleeding control was the primary outcome. RESULTS: All animals had similar pretreatment mean arterial pressure (MAP) (∼ 36.5 mmHg); pretreatment blood loss following injury was similar for both dressing groups in the two models [24% ± 8% estimated blood volume (EBV) 2 min after transection and 17% ± 4% EBV 45 s after puncture. Incidence of post-treatment bleeding, primarily occurring after release of manual compression or restoration of blood pressure, was more frequent in the puncture model (17% with both CBG and TMS) than the transection model (57% with CBG versus 75% with TMS). Post-treatment blood loss not controlled by the dressing was 19% ± 22% and 31% ± 17% EBV, for CBG and TMS, respectively. Survival rate was 100% for both dressings in the transection model, and was 88% for CBG and 50% for TMS in the puncture model. CONCLUSIONS: These findings indicated that CBG and TMS were similarly effective in improving hemostasis. These two fabric-like dressings showed easy application and removal, leaving a clean wound for surgical repair.

Automated Neuropsychological Assessment Metrics: repeated assessment with two military samples.

INTRODUCTION: U.S. military troops deploying to war zones are currently administered the Automated Neuropsychological Assessment Metrics (ANAM4) Traumatic Brain Injury (TBI) Battery to establish individual neurocognitive performance baselines. In part, the utility of the ANAM4 TBI Battery baseline measurement depends on test-retest reliability of this instrument. The purpose of this report was to evaluate performance following multiple administrations of the ANAM4 TBI Battery: does performance in a repeated measures paradigm constitute a stable, interpretable indication of baseline neurocognitive ability? METHODS: The data presented here are from the ANAM4 TBI Battery administered four times to a group of U.S. Marines in Study 1 and eight times to a group of New Zealand Defence Force personnel in Study 2. RESULTS: The results show practice effect in five of six performance subtests in both Study 1 and Study 2. DISCUSSION: Results are consistent with expectations that multiple test sessions are required to reach stable performance on some computerized tasks. These results have implications for taking ANAM4 TBI Battery practice effects into account in test administration and in data interpretation.

Development of a Blast Exposure Estimator from a Department of Defense-Wide Survey Study on Military Service Members.

Long-term, repeated exposure to low-intensity blast overpressure is a potential causal factor of lasting outcomes reminiscent of post-concussion syndrome. Wearable blast sensor engineers are exploring elements of blast that are associated with outcomes. Currently, however, there are no devices that can truly record all blasts experienced by an individual. Military service members (n = 984) were surveyed about their lifelong exposure and behavioral health. Using heavy-arms-associated target outcomes, we calculated a generalized blast exposure value (GBEV) for each participant. A threshold of 200,000 GBEV units was established at which a participant was likely to report more intense symptomology. If repetitive, low-intensity blast exposure has even a subtle effect over time, operational readiness could be negatively impacted. A threshold of exposure can inform decisions about how to reduce detrimental exposure. The GBEV can be used to track ongoing exposure and potentially identify those who may be at risk for developing blast-related outcomes.

Bisulfite Amplicon Sequencing Can Detect Glia and Neuron Cell-Free DNA in Blood Plasma.

Sampling the live brain is difficult and dangerous, and withdrawing cerebrospinal fluid is uncomfortable and frightening to the subject, so new sources of real-time analysis are constantly sought. Cell-free DNA (cfDNA) derived from glia and neurons offers the potential for wide-ranging neurological disease diagnosis and monitoring. However, new laboratory and bioinformatic strategies are needed. DNA methylation patterns on individual cfDNA fragments can be used to ascribe their cell-of-origin. Here we describe bisulfite sequencing assays and bioinformatic processing methods to identify cfDNA derived from glia and neurons. In proof-of-concept experiments, we describe the presence of both glia- and neuron-cfDNA in the blood plasma of human subjects following mild trauma. This detection of glia- and neuron-cfDNA represents a significant step forward in the translation of liquid biopsies for neurological diseases.