Imaging findings of the injured in the massive Beirut blast.

PURPOSE: (1) Describe imaging utilization and findings within two weeks of the 2020 Beirut blast according to the mechanism of injury, (2) determine the appropriate imaging modality per organ/system, and (3) describe changes in the workflow of a radiology department to deal with massive crises. MATERIALS AND METHODS: Two hundred sixty patients presented to the largest emergency department in Beirut and underwent imaging within 2 weeks of the blast. In this retrospective study, patients were divided into early (1) and late (2) imaging groups. Patients' demographic, outcome, type and time of imaging studies, body parts imaged, and mechanism and types of injuries were documented. RESULTS: Two hundred five patients in group 1 underwent 502 and 55 patients in group 2 underwent 145 imaging studies. Tertiary blast injuries from direct impact and falling objects were the most common type of injuries followed by secondary (shrapnel) injuries. Both types of injuries affected mostly the head and neck and upper extremities. Plain radiographs were adequate for the extremities and CT for the head and neck. A regularly updated and practiced emergency plan is essential to mobilize staff and equipment and efficiently deliver radiology services during crises. CONCLUSION: Because the powerful Beirut blast occurred at the port located in the periphery of the city, most injuries seen on imaging were of the upper extremities and head and neck caused by the severe blast wind or penetrating shrapnel and resulted from people using their arms to protect their heads and bodies from direct impact and falling objects.

Blast Lung Injury in Children: Injury Patterns and Associated Organ Injuries.

BACKGROUND: Bombings are the most common cause of civilian deaths in wars, and unfortunately, a large proportion of civilian victims are children. OBJECTIVE: This study aimed to evaluate the frequency of blast lung injury (BLI), to evaluate lung injury patterns on tomographic images, and to document the relationship between blast lung and mortality in children exposed to the blast effect. METHODS: Thirty-six children (25.3% of pediatric patients brought to our hospital with blast injury) with BLI were included in the study. The pediatric trauma score evaluations made in the emergency department in the first admission were recorded. Lung injury findings in the computed tomography images of the patients were examined, and injuries detected in other systems were recorded. RESULTS: The most common lung injury pattern was contusion (right: 69.4%, left: 80.6%). The incidence of brain damage (52.4%) and intra-abdominal injury (76.2%) in children with low pediatric trauma score value was statistically significantly higher ( P = 0.049, P = 0.017, respectively). There was no statistically significant correlation between the presence of lung injury, injury patterns, and mortality. The incidence of brain damage in deceased patients (61.5%) was statistically significantly higher than the incidence of brain damage in surviving patients (26.1%) ( P = 0.036). Low pediatric trauma score was observed in 11 (84.6%) of the deceased children and in 10 (43.5%) of the survivors ( P = 0.016). The mean age of children with hemothorax in the right lung was statistically significantly lower than those without ( P = 0.014). CONCLUSION: Our findings revealed that pediatric BLI is common after a blast, that it is associated with other system injuries, and that a multimodal radiological approach is required in child victims.

Early Brain Amyloid Accumulation at PET in Military Instructors Exposed to Subconcussive Blast Injuries.

Background Traumatic brain injury (TBI) is the leading cause of disability in young adults. Recurrent TBI is associated with a range of neurologic sequelae, but the contributing factors behind the development of such chronic encephalopathy are poorly understood. Purpose To quantify early amyloid ß deposition in the brain of otherwise healthy adult men exposed to repeated subconcussive blast injury using amyloid PET. Materials and Methods In this prospective study from January 2020 to December 2021, military instructors who were routinely exposed to repeated blast events were evaluated at two different points: baseline (before blast exposure from breacher or grenade) and approximately 5 months after baseline (after blast exposure). Age-matched healthy control participants not exposed to blasts and without a history of brain injury were evaluated at similar two points. Neurocognitive evaluation was performed with standard neuropsychologic testing in both groups. Analysis of PET data consisted of standardized uptake value measurements in six relevant brain regions and a whole-brain voxel-based statistical approach. Results Participants were men (nine control participants [median age, 33 years; IQR, 32-36 years] and nine blast-exposed participants [median age, 33 years; IQR, 30-34 years]; P = .82). In the blast-exposed participants, four brain regions showed significantly increased amyloid deposition after blast exposure: inferomedial frontal lobe (P = .004), precuneus (P = .02), anterior cingulum (P = .002), and superior parietal lobule (P = .003). No amyloid deposition was observed in the control participants. Discriminant analysis on the basis of regional changes of amyloid accumulation correctly classified the nine healthy control participants as healthy control participants (100%), and seven of the nine blast-exposed participants (78%) were correctly classified as blast exposed. Based on the voxel-based analysis, whole-brain parametric maps of early abnormal early amyloid uptake were obtained. Conclusion Early brain amyloid accumulation was identified and quantified at PET in otherwise healthy adult men exposed to repetitive subconcussive traumatic events. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Haller in this issue.

Secondary blast injury: radiological characteristics of shrapnel injuries in children.

PURPOSE: The aim of this study is to examine the radiological images of child victims suffering from secondary blast injuries, to reveal organ-based injury patterns and their interrelationships, and to record mortality rates that may develop due to injured systems. METHODS: A total of 65 patients with secondary blast injury due to bomb explosion were included in the study. Injury findings due to shrapnel in radiologic images of the patients were examined. Injured systems and types of injuries were recorded. RESULTS: The most common injuries were intra-abdominal injuries (63%) and fractures (58.5%). Lung injury was observed in 4 (9.8%) of 41 patients with intra-abdominal injury, while 37 (90.2%) did not, and this was statistically significant (p = 0.003). The most common intra-abdominal organ injury was a small bowel injury in 23 (35.4%) patients. The coexistence of small bowel injury and large bowel injury was present in 8 patients (34.8%), and it was statistically significant (p = 0.019). A total of 14 (21.5%) of the patients died. There was no significant relationship between mortality and gender (p = 319). Brain damage was present in 10 (71.4%) of the 14 (21.5%) patients who died, which was statistically significant (p < 0.001). CONCLUSION: Our results showed that the most common injuries were intra-abdominal injuries, damage to different organs could occur at the same time, and deaths were especially associated with brain injuries. For this reason, it should not be forgotten that CT scans will have an important place in the triage of the patient, especially in victims with shrapnel at the abdominal and cranial levels in radiography examinations.

Injuries in Underbody Blast Fatalities: Identification of Five Distinct Mechanisms of Head Injury.

Previous research has shown that injuries to the head and neck were prevalent in 73% of all mounted fatalities of underbody blast. The mechanisms that cause such injuries to the central nervous system (CNS) are not yet known. The aim of this study was to identify the head and spinal injuries in fatalities due to underbody blast (UBB) and then develop hypotheses on the causative mechanisms. All U.K. military fatalities from UBB with an associated head injury that occurred during 2007-2013 in the Iraq and Afghanistan conflicts were identified retrospectively. Computed tomography post-mortems (CTPMs) were interrogated for injuries to the head, neck, and spine. All injuries were documented and classified using a radiology classification. Pearson's chi-square and Fisher's exact tests were used to show a relationship between variables and form a hypothesis for injury mechanisms. There were 50 fatalities from UBB with an associated head injury. Of these, 46 had complete CTPMs available for analysis. Chi-square and Fisher's exact tests showed a relationship between lateral ventricle blood and injuries to the abdomen and thorax. Five partially overlapping injury constellations were identified: 1.multiple-level spinal injury with skull fracture and brainstem injury, 2.peri-mesencephalic hemorrhage, 3.spinal and brainstem injury, 4.parenchymal contusions with injury to C0-C1, and 5.an "eggshell" pattern of fractures from direct impact. These injury constellations can now be used to propose injury mechanisms to develop mitigation strategies or clinical treatments.

Incidental blast injuries to the hands of hunters in suburban Africa.

Background: Civilian blast injuries are common during celebrations and festivities. In the intervening times, civilian nonterrorist blast events are rare. The aim of this report is to highlight the increasing occurrence of blast injuries to the dominant right hand of hunters and the ensuing crippling consequences. Methodology: A review of incidental blast injuries to the hand among hunters was conducted. The case files, clinical photographs, and radiographs of consecutive cases of blast injuries presenting to our unit over 3½ years were studied. Result: Six patients had incidental blast injuries to the hand within the period. All the patients were males and hunters by profession. The age range was 30-49 years. The dominant right hand was involved in all the six cases with high-energy soft tissue and bony injuries. Five patients had staged soft tissue coverage while the sixth patient, after initial resuscitation, discharged against medical advice due to economic constraints. Multiple joint stiffness and significant disability occurred in all the affected hands. None of the patients represented for secondary procedures. Conclusion: Incidental blast injuries to the hands of local hunters are lifestyle threatening. The dominant right hand is invariably involved with attendant crippling socioeconomic consequences. Meticulous clinical care and methodical operative intervention are primal to hand salvage.

Résumé Contexte: Les blessures civiles dues à des explosions sont fréquentes lors des célébrations et des festivités. Dans l'intervalle, les explosions civiles non terroristes sont rares. sont rares. L'objectif de ce rapport est de mettre en évidence la fréquence croissante des blessures par explosion de la main droite dominante des chasseurs et les conséquences invalidantes qui en découlent. conséquences invalidantes. Méthodologie: Une revue des blessures accidentelles par explosion à la main chez les chasseurs a été menée. Les dossiers, les photographies cliniques Les dossiers, les photographies cliniques et les radiographies des cas consécutifs de blessures par explosion qui se sont présentés à notre unité pendant 3½ ans ont été étudiés. Résultat: Six patients ont eu blessures accidentelles par explosion à la main au cours de cette période. Tous les patients étaient des hommes et des chasseurs de profession. La tranche d'âge était de 30 à 49 ans. La main droite dominante était impliquée dans les six cas avec des lésions osseuses et des tissus mous à haute énergie. Pour cinq patients, la couverture des tissus mous s'est faite par étapes. tandis que le sixième patient, après une réanimation initiale, a quitté l'hôpital contre avis médical en raison de contraintes économiques. Raideur articulaire multiple et un handicap significatif sont apparus dans toutes les mains affectées. Aucun des patients ne s'est représenté pour des procédures secondaires. Conclusion: Les blessures accidentelles dues à l'explosion de Les blessures accidentelles aux mains des chasseurs locaux menacent leur mode de vie. La main droite dominante est invariablement touchée avec des conséquences socio-économiques invalidantes. conséquences socio-économiques. Des soins cliniques méticuleux et une intervention chirurgicale méthodique sont essentiels pour sauver la main. Mots-clés: Poudre noire, blessure par explosion, mains de chasseurs, accidentelle, banlieue.

Imaging in paediatric blast injuries: musculoskeletal injuries in the Syrian Civil War.

AIM: To examine the radiological images of children with musculoskeletal injuries and accompanying organ injuries caused by explosions to determine the differences and frequency of injury types and to emphasise the importance of radiology in war injuries. MATERIALS AND METHODS: Seventy-four children with injuries caused by bomb explosions were included in the study. The paediatric trauma scores evaluated in the emergency department on the first admission were recorded. All radiographs and computed tomography (CT) images were evaluated for musculoskeletal injuries and accompanying organ injuries. RESULTS: The highest incidence of fracture in the primary blast injury (PBI) group was skull fracture in 15 (62.5%) patients (p=0.01) and fractures in the other groups were most common in the lower extremities. Amputation was observed in nine (31%) patients in the PBI group (p=0.003); however, there were no patients with amputations in the secondary blast injury (SBI) group (p=0.002). The frequency of pneumothorax (79.3%) and pulmonary contusion (59.4%) was high in the PBI group (p<0.001 and p=0.004, respectively). Skull fractures were observed in 15 (88.2%) of 17 patients with brain injury (p<0.001), and skull fractures were the most common fracture site accompanying pulmonary trauma. The average paediatric trauma score of individuals exposed to shrapnel was found to be high (p<0.001). CONCLUSION: Because paediatric musculoskeletal injuries vary with the type of blast injury and severe trauma can occur in children due to blast effects, radiologists who triage mass injuries should understand the effects of blast injury patterns and the spectrum of injury.

Thoracoabdominal injuries after a bomb explosion: blast injuries and their clinical effects.

PURPOSE: To report the types and effects of injuries to the thoracoabdominal region caused by blast and emphasize the importance of the early detection of primary blast injuries. METHODS: Of the 98 patients injured as a result of a bomb explosion, 31 with thoracoabdominal injuries were included in the study. The demographic and laboratory data, operations performed, and radiological findings were obtained from the electronic records of the patients. The injuries caused by the explosion were divided into four categories as primary, secondary, tertiary, and quaternary. The patients with a new injury severity score (NISS) of ≥ 16 were considered to have critical injuries. RESULTS: While mortality developed in 16 (51.6%) of 31 patients included in the study, 15 (48.4%) were discharged after treatment. The mean ages of the patients in the mortality and survivor groups were 29.6 ± 4.5 and 31.1 ± 10.7 years, respectively (p > 0.005). When the two groups were examined, the rate of hypovolemic shock and NISS score were significantly higher in the mortality group (p = 0.001 and p < 0.001, respectively) and the pH of the patients in the mortality group was more acidic (7.18 ± 0.13 vs. 7.34 ± 0.13, p = 0.002). One patient in the survivor group required surgery after the explosion due to missed primary blast injuries. CONCLUSIONS: To make the best use of resources in terrorist attacks and mass casualties that place a huge burden on health systems, it is important to evaluate patients with the highest index of suspicion for concealed blast injuries in terms of hospitalization and observation. In addition, health systems need to develop a cost-effective strategy considering the possibility of delayed-onset blast injuries.

A rare case of iliopsoas abscess caused by a retained shrapnel from a blast injury.

Iliopsoas abscesses (IPA) are uncommon, with an associated mortality rate of up to 20%. We describe the case of a 55-year-old man war veteran who presented with an unusual cause of IPA secondary to retained foreign body (FB). His initial trauma 30 years before was a result of a blast injury with shrapnel penetration suffered after inadvertently driving over a landmine as an ambulance driver in a conflict region. A CT scan was performed, revealing a 13 mmx8 mm radio-opaque FB within the right psoas at the level of the fifth lumbar vertebra with a surrounding collection. Subsequent open surgical exploration removed two gravel fragments. Given the knowledge of a traumatic blast injury with retained FB and repeated episodes of sepsis, surgical exploration is warranted. To our knowledge, this is the first case of recurrent IPA secondary to a retained FB from a historical trauma.

Correlation of Histomorphometric Changes with Diffusion Tensor Imaging for Evaluation of Blast-Induced Auditory Neurodegeneration in Chinchilla.

In the present study, we have evaluated the blast-induced auditory neurodegeneration in chinchilla by correlating the histomorphometric changes with diffusion tensor imaging. The chinchillas were exposed to single unilateral blast-overpressure (BOP) at ∼172dB peak sound pressure level (SPL) and the pathological changes were compared at 1 week and 1 month after BOP. The functional integrity of the auditory system was assessed by auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE). The axonal integrity was assessed using diffusion tensor imaging at regions of interests (ROIs) of the central auditory neuraxis (CAN) including the cochlear nucleus (CN), inferior colliculus (IC), and auditory cortex (AC). Post-BOP, cyto-architecture metrics such as viable cells, degenerating neurons, and apoptotic cells were quantified at the CAN ROIs using light microscopic studies using cresyl fast violet, hematoxylin and eosin, and modified Crossmon's trichrome stains. We observed mean ABR threshold shifts of 30- and 10-dB SPL at 1 week and 1 month after BOP, respectively. A similar pattern was observed in DPAOE amplitudes shift. In the CAN ROIs, diffusion tensor imaging studies showed a decreased axial diffusivity in CN 1 month after BOP and a decreased mean diffusivity and radial diffusivity at 1 week after BOP. However, morphometric measures such as decreased viable cells and increased degenerating neurons and apoptotic cells were observed at CN, IC, and AC. Specifically, increased degenerating neurons and reduced viable cells were high on the ipsilateral side when compared with the contralateral side. These results indicate that a single blast significantly damages structural and functional integrity at all levels of CAN ROIs.

Point-of-care ultrasound for treatment and triage in austere military environments.

BACKGROUND: Assessment and triage in an austere environment represent a major challenge in casualty care. Modern conflicts involve a significant proportion of multiple wounds, either superficial or penetrating, which complicate clinical evaluation. Furthermore, there is often poor accessibility to computed tomography scans and a limited number of surgical teams. Therefore, ultrasound (US) represents a potentially valuable tool for distinguishing superficial fragments or shrapnels from penetrating trauma requiring immediate damage-control surgery. METHODS: This retrospective observational multicenter study assessed casualties treated for 8 months by five medical teams deployed in Africa and Middle East. Two experts, who were experienced in military emergency medicine but did not take part in the missions, carried out an independent analysis for each case, evaluating the contribution of US to the following five items: triage categorization, diagnosis, clinical severity, prehospital therapeutic choices, and priority to operation room. Consensus was obtained using the Delphi method with three rounds. RESULTS: Of 325 casualties, 189 underwent US examination. The mean injury severity scale score was 25.6, and 76% were wounded by an improvised explosive device. Ultrasound was useful for confirming (23%) or excluding (63%) the suspected diagnosis made in the clinical assessment. It also helped obtain a diagnosis that had not been considered for 3% of casualties and was responsible for a major change in procedure or therapy in 4%. Ultrasound altered the surgical priority in 43% of cases. For 30% of cases, US permitted surgery to be temporarily delayed to prioritize another more urgent casualty. CONCLUSION: Ultrasound is a valuable tool for the management of mass casualties by improving treatment and triage, especially when surgical resources are limited. In some situations, US can also correct a diagnosis or improve prehospital therapeutic choices. Field medical teams should be trained to integrate US into their prehospital protocols. LEVEL OF EVIDENCE: Case series (no criterion standard), level V.

Imaging findings in patients after the bomb explosion in Somalia on December 28, 2019.

INTRODUCTION: This study aimed to present the radiological findings of injuries in victims as a result of a suicide bombing in Mogadishu, Somalia. METHODS: Of the 82 injured cases admitted to the emergency department within the first six hours after the explosion, those who were radiologically evaluated were included in this retrospective and descriptive study. To analyze and identify the distribution of primary, secondary, and tertiary injuries, they were classified according to the body areas as head-neck, thorax, abdominopelvic, extremity, and vertebra. RESULTS: The mean age (mean ± SD) of 63 patients included in the study was 28.6 ± 10.2 years. Twenty-four (38.1%) of the injured patients were female and 39 (61.9%) were male. Secondary blast injury was the most common type of injury in the study group with a rate of 39/63 (62%). The total number of bomb fragments was 235, of which 113 (47.8%) were seen in the head and neck region, followed by 86 (36.5%) in the extremities. There were 10 patients (15.9%) with lung injury and 13 (20.6%) with tympanic membrane perforation due to the primary blast mechanism. CONCLUSION: Radiological imaging plays an important role in identifying specific findings and patterns of explosive injuries. Therefore, we consider that patients with stable hemodynamics should be radiologically examined for a fast and accurate diagnosis or treatment.

Oesophageal rupture from a pneumatic blast injury: an unusual mechanism of blunt oesophageal trauma.

Oesophageal perforation is a serious condition associated with significant morbidity and mortality. Clinical suspicion of oesophageal injury in patients sustaining neck or torso trauma is essential as early diagnosis and management are associated with better outcomes. Oesophageal perforation resulting from blunt trauma is uncommon, and traumatic oesophageal perforation following blast injury is exceedingly rare. We present two cases of patients developing oesophageal perforation from this rare mechanism, review basic principles of management, and key learning points.

Identifying degenerative effects of repetitive head trauma with neuroimaging: a clinically-oriented review.

BACKGROUND AND SCOPE OF REVIEW: Varying severities and frequencies of head trauma may result in dynamic acute and chronic pathophysiologic responses in the brain. Heightened attention to long-term effects of head trauma, particularly repetitive head trauma, has sparked recent efforts to identify neuroimaging biomarkers of underlying disease processes. Imaging modalities like structural magnetic resonance imaging (MRI) and positron emission tomography (PET) are the most clinically applicable given their use in neurodegenerative disease diagnosis and differentiation. In recent years, researchers have targeted repetitive head trauma cohorts in hopes of identifying in vivo biomarkers for underlying biologic changes that might ultimately improve diagnosis of chronic traumatic encephalopathy (CTE) in living persons. These populations most often include collision sport athletes (e.g., American football, boxing) and military veterans with repetitive low-level blast exposure. We provide a clinically-oriented review of neuroimaging data from repetitive head trauma cohorts based on structural MRI, FDG-PET, Aß-PET, and tau-PET. We supplement the review with two patient reports of neuropathology-confirmed, clinically impaired adults with prior repetitive head trauma who underwent structural MRI, FDG-PET, Aß-PET, and tau-PET in addition to comprehensive clinical examinations before death. REVIEW CONCLUSIONS: Group-level comparisons to controls without known head trauma have revealed inconsistent regional volume differences, with possible propensity for medial temporal, limbic, and subcortical (thalamus, corpus callosum) structures. Greater frequency and severity (i.e., length) of cavum septum pellucidum (CSP) is observed in repetitive head trauma cohorts compared to unexposed controls. It remains unclear whether CSP predicts a particular neurodegenerative process, but CSP presence should increase suspicion that clinical impairment is at least partly attributable to the individual's head trauma exposure (regardless of underlying disease). PET imaging similarly has not revealed a prototypical metabolic or molecular pattern associated with repetitive head trauma or predictive of CTE based on the most widely studied radiotracers. Given the range of clinical syndromes and neurodegenerative pathologies observed in a subset of adults with prior repetitive head trauma, structural MRI and PET imaging may still be useful for differential diagnosis (e.g., assessing suspected Alzheimer's disease).

Bomb blast: imaging findings, treatment and clinical course of extremity traumas.

BACKGROUND: To describe the severity and types of blast-related extremity injuries and the presence of accompanying vascular injuries (VI) and amputation, and to identify the associated factors affecting the treatment management and clinical course. METHODS: The study included 101 patients with extremity injuries caused by a bomb explosion. The radiographs and computed tomography angiographies of the patients were evaluated in terms of injury patterns, presence of penetrating fragments and fractures, and localization (upper or lower extremity) and type (open or closed) of injury. The Gustilo-Anderson classification was used for open fractures. According to their severity, open fractures classified as types 1 and 2 were included in Group 1 and those classified as type 3A, 3B and 3C in Group 2. RESULTS: As a result of blast exposure, 101 (57.7%) patients had extremity injuries, of which 76 (75.2%) presented with at least one fracture. Of the total of 103 fractures, nine (8.8%) were closed and 94 (91.2%) were open. Thirty-eight (40.4%) of the open fractures were located in the upper extremities, and 56 (59.6%) in the lower extremities and pelvis. Open fractures were most frequently localized in the femur (n = 20; 21.2%), followed by the tibia (n = 18; 19.1%). The majority of patients with open fractures were in Group 1 (71.4%). The duration of hospital stay was longer in Group 2 (12.1 ± 5.8 vs. 6.3 ± 6.7 days, p <  0.0001, respectively). Mortality among patients in Group 2 (45.0%) was significantly higher than in Group 1 (8.0%) (p <  0.0001). Similarly, the injury severity score (ISS) was higher in Group 2 (median 20 vs. 9, p <  0.0001). VI was present in 13 (12.9%) of all patients, and amputation in seven (7.9%). CONCLUSION: The presence of severe open fractures, VI, and high ISS score can be considered as important factors that increase morbidity and mortality. In extremity traumas, through the secondary blast mechanism, contaminated-fragmented tissue injuries occur. Therefore, we believe that it will be beneficial to apply damage control surgery in places with low socioeconomic level and poor hygienic conditions.

Original experimental rat model of blast-induced mild traumatic brain injury: a pilot study.

OBJECTIVE: Diagnosing blast-induced mild traumatic brain injury (mTBI) is difficult due to minimal imaging findings. This study aimed to establish a rat model of behavioral abnormality caused by blast-induced mTBI and detect new findings for therapeutic intervention. METHODS: We used a bench-top blast wave generator with the blast wave exiting through a 20-mm I.D. nozzle aimed at the focused target. The blast wave was directed at the head of male Wistar rats under general anesthesia positioned prone 2.5 cm below the nozzle. Peak shock wave pressure was 646.2 ± 70.3 kPa. RESULTS: After blast injury, mTBI rats did not show the findings of brain hemorrhage or contusion macroscopically and on hematoxylin-eosin-stained frozen sections but did show anorexia and weight loss in the early post-injury phase. Behavioral experiments revealed short-term memory impairment at 2 weeks and depression-like behavior at 2 and 6 weeks. Diffusion-weighted ex vivo MRI showed high-intensity areas in layers of the bilateral hippocampus. Immunohistochemical analysis revealed accumulation of reactive microglia and GFAP-positive astrocytes in the same region and loss of NeuN-positive neurons in the hippocampal pyramidal cell layer. CONCLUSIONS: This model can reflect the pathophysiology of blast-induced mTBI and could potentially be used to develop therapeutic interventions in the future.

Neuropsychological, Neurocognitive, Vestibular, and Neuroimaging Correlates of Exposure to Repetitive Low-Level Blast Waves: Evidence From Four Nonoverlapping Samples of Canadian Breachers.

INTRODUCTION: We assessed the utility of a battery of neuropsychological, neurocognitive, physiological (balance, ataxia, postural tremor), and neuroimaging measures for studying the effects of blast waves in breachers-a population repeatedly exposed to low-level blast during military training and operations. MATERIALS AND METHODS: Data were collected from four nonoverlapping samples, in the course of similarly structured 4-day breacher training exercises in successive years involving a combination of indoor and outdoor blast events. In all cases, self-report and neuropsychological measures were administered once at baseline (i.e., 1 day before the start of training). In years 1-2, neurocognitive and physiological measures were administered daily before and after training. In years 3-4, neurocognitive data were collected once at baseline. In Year 4, we introduced 3 modifications to our design. First, in addition to breachers, we also collected data from sex-and age-matched military controls at the same time points. Second, we assessed balance, ataxia, and postural tremor immediately following blast exposure "in the field," enabling us to quantify its acute effects. Third, structural magnetic resonance imaging (MRI) scans were acquired before and after the 4-day training exercise to explore differences between breachers and controls at baseline, as well as possible training-related changes using voxel-based morphometry. These design modifications were made to enable us to test additional hypotheses in the context of the same training exercise. RESULTS: At baseline, scores on the "Rivermead Post Concussion Symptoms Questionnaire," "RAND SF-36" (physical functioning, role limitation due to physical health, social functioning, energy/fatigue, general health), and "Short Musculoskeletal Function Questionnaire" distinguished breachers from controls. Also at baseline, the MRI data revealed that there was greater regional gray matter volume in controls compared to breachers in the right superior frontal gyrus. Balance, ataxia, and postural tremor did not exhibit sensitivity to the acute effects of blast in the field, nor did neurocognitive measures to its cumulative or daily effects. CONCLUSION: Our exploratory results suggest that self-report neuropsychological measures and structural MRI hold promise as sensitive measures for quantifying the long-term, cumulative effects of blast exposure in breachers. We discuss the limitations of our study and the need for prospective longitudinal data for drawing causal inferences regarding the impact of blast exposure on breachers' health and performance.

Functional and Structural Neuroimaging Correlates of Repetitive Low-Level Blast Exposure in Career Breachers.

Combat military and civilian law enforcement personnel may be exposed to repetitive low-intensity blast events during training and operations. Persons who use explosives to gain entry (i.e., breach) into buildings are known as "breachers" or dynamic entry personnel. Breachers operate under the guidance of established safety protocols, but despite these precautions, breachers who are exposed to low-level blast throughout their careers frequently report performance deficits and symptoms to healthcare providers. Although little is known about the etiology linking blast exposure to clinical symptoms in humans, animal studies demonstrate network-level changes in brain function, alterations in brain morphology, vascular and inflammatory changes, hearing loss, and even alterations in gene expression after repeated blast exposure. To explore whether similar effects occur in humans, we collected a comprehensive data battery from 20 experienced breachers exposed to blast throughout their careers and 14 military and law enforcement controls. This battery included neuropsychological assessments, blood biomarkers, and magnetic resonance imaging measures, including cortical thickness, diffusion tensor imaging of white matter, functional connectivity, and perfusion. To better understand the relationship between repetitive low-level blast exposure and behavioral and imaging differences in humans, we analyzed the data using similarity-driven multi-view linear reconstruction (SiMLR). SiMLR is specifically designed for multiple modality statistical integration using dimensionality-reduction techniques for studies with high-dimensional, yet sparse, data (i.e., low number of subjects and many data per subject). We identify significant group effects in these data spanning brain structure, function, and blood biomarkers.

Chronic elevation of plasma vascular endothelial growth factor-A (VEGF-A) is associated with a history of blast exposure.

Mounting evidence points to the significance of neurovascular-related dysfunction in veterans with blast-related mTBI, which is also associated with reduced [18F]-fluorodeoxyglucose (FDG) uptake. The goal of this study was to determine whether plasma VEGF-A is altered in veterans with blast-related mTBI and address whether VEGF-A levels correlate with FDG uptake in the cerebellum, a brain region that is vulnerable to blast-related injury 72 veterans with blast-related mTBI (mTBI) and 24 deployed control (DC) veterans with no lifetime history of TBI were studied. Plasma VEGF-A was significantly elevated in mTBIs compared to DCs. Plasma VEGF-A levels in mTBIs were significantly negatively correlated with FDG uptake in cerebellum. In addition, performance on a Stroop color/word interference task was inversely correlated with plasma VEGF-A levels in blast mTBI veterans. Finally, we observed aberrant perivascular VEGF-A immunoreactivity in postmortem cerebellar tissue and not cortical or hippocampal tissues from blast mTBI veterans. These findings add to the limited number of plasma proteins that are chronically elevated in veterans with a history of blast exposure associated with mTBI. It is likely the elevated VEGF-A levels are from peripheral sources. Nonetheless, increasing plasma VEGF-A concentrations correlated with chronically decreased cerebellar glucose metabolism and poorer performance on tasks involving cognitive inhibition and set shifting. These results strengthen an emerging view that cognitive complaints and functional brain deficits caused by blast exposure are associated with chronic blood-brain barrier injury and prolonged recovery in affected regions.

Diffusion Tensor Imaging Detects Acute and Subacute Changes in Corpus Callosum in Blast-Induced Traumatic Brain Injury.

There is a critical need for understanding the progression of neuropathology in blast-induced traumatic brain injury using valid animal models to develop diagnostic approaches. In the present study, we used diffusion imaging and magnetic resonance (MR) morphometry to characterize axonal injury in white matter structures of the rat brain following a blast applied via blast tube to one side of the brain. Diffusion tensor imaging was performed on acute and subacute phases of pathology from which fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were calculated for corpus callosum (CC), cingulum bundle, and fimbria. Ventricular volume and CC thickness were measured. Blast-injured rats showed temporally varying bilateral changes in diffusion metrics indicating persistent axonal pathology. Diffusion changes in the CC suggested vasogenic edema secondary to axonal injury in the acute phase. Axonal pathology persisted in the subacute phase marked by cytotoxic edema and demyelination which was confirmed by ultrastructural analysis. The evolution of pathology followed a different pattern in the cingulum bundle: axonal injury and demyelination in the acute phase followed by cytotoxic edema in the subacute phase. Spatially, structures close to midline were most affected. Changes in the genu were greater than in the body and splenium; the caudal cingulum bundle was more affected than the rostral cingulum. Thinning of CC and ventriculomegaly were greater only in the acute phase. Our results reveal the persistent nature of blast-induced axonal pathology and suggest that diffusion imaging may have potential for detecting the temporal evolution of blast injury.