Bomb blast, mild traumatic brain injury and psychiatric morbidity: a review

Effects of Repetitive Mild Traumatic Brain Injury on Corticotropin-Releasing Factor Modulation of Lateral Habenula Excitability and Motivated Behavior

Mild traumatic brain injury (mTBI) is a significant health burden due to mTBI-related chronic debilitating cognitive and psychiatric morbidities. Recent evidence from our laboratory suggests a possible dysregulation within reward/motivational circuit function at the level of a subcortical structure, the lateral habenula (LHb), where we demonstrated a causal role for hyperactive LHb in mTBI-induced motivational deficits in self-care grooming behavior in young adult male mice when exposed to mTBI during late adolescence (at ∼8 weeks old). In this study, we extended this observation by further characterizing neurobehavioral effects of this repetitive closed head injury model of mTBI in both young adult male and female mice on LHb excitability, corticotropin releasing factor (CRF) modulation of LHb activity, and behavioral responses of motivation to self-care behavior and approach versus avoidance behavior in the presence of a social- or threat-related stimulus. We show that mTBI increases LHb spontaneous tonic activity in female mice similar to what we previously observed in male mice, as well as promoting LHb neuronal hyperexcitability and hyperpolarization-induced LHb bursting in both male and female mice. Interestingly, mTBI only increases LHb intrinsic excitability in male mice coincident with higher levels of the hyperpolarization-activated cation currents (HCN/Ih) and reduces levels of the M-type potassium currents while potentiating M-currents without altering intrinsic excitability in LHb neurons of female mice. Because persistent dysregulation of brain CRF systems is suggested to contribute to chronic psychiatric morbidities and that LHb neurons are highly responsive to CRF, we tested whether the LHb CRF subsystem becomes engaged following mTBI. We found that in vitro inhibition of CRF receptor type 1 (CRFR1) within the LHb reverses mTBI-induced enhancement of LHb tonic activity and hyperexcitability in both sexes, suggesting that an augmented intra-LHb CRF-CRFR1-mediated signaling contributes to the overall LHb hyperactivity following mTBI. Behaviorally, mTBI diminishes motivation for self-care grooming in female mice as in male mice. mTBI also alters defensive behaviors in the looming shadow task by shifting the innate defensive behaviors toward more passive action locking rather than escape behaviors in response to an aerial threat in both male and female mice, as well as prolonging the latency to escape responses in female mice. While this model of mTBI reduces social preference in male mice, it induces higher social novelty seeking during the novel social encounters in both male and female mice. Overall, our study provides further translational validity for the use of this pre-clinical model of mTBI for investigation of mTBI-related reward circuit dysfunction and mood/motivation-related behavioral deficits in both sexes while uncovering a few sexually dimorphic neurobehavioral effects of this model that may differentially affect young males and females when exposed to this type of mTBI during late adolescence.

Effects of Repetitive Mild Traumatic Brain Injury on Corticotropin-Releasing Factor Modulation of Lateral Habenula Excitability and Motivated Behavior

Mild traumatic brain injury (mTBI) is a significant health burden due to mTBI-related chronic debilitating cognitive and psychiatric morbidities. Recent evidence from our laboratory suggests a possible dysregulation within reward/motivational circuit function at the level of a subcortical structure, the lateral habenula (LHb), where we demonstrated a causal role for hyperactive LHb in mTBI-induced motivational deficits in self-care grooming behavior in young adult male mice when exposed to mTBI injury during late adolescence (at ~8 weeks old). Here we extended this observation by further characterizing neurobehavioral effects of this repetitive closed head injury model of mTBI in both young adult male and female mice on LHb excitability, corticotropin releasing factor (CRF) modulation of LHb activity, and behavioral responses of motivation to self-care behavior, and approach versus avoidance behavior in the presence of a social- or threat-related stimulus. We show that mTBI increases LHb spontaneous tonic activity in female mice similar to what we previously observed in male mice as well as promoting LHb neuronal hyperexcitability and hyperpolarization-induced LHb bursting in both male and female mice. Interestingly, mTBI only increases LHb intrinsic excitability in male mice coincident with higher levels of the hyperpolarization-activated cation currents (HCN/Ih) and reduces levels of the M-type potassium currents while potentiating M-currents without altering intrinsic excitability in LHb neurons of female mice. Since persistent dysregulation of brain CRF systems is suggested to contribute to chronic psychiatric morbidities and that LHb neurons are highly responsive to CRF, we then tested whether LHb CRF subsystem becomes engaged following mTBI. We found that in vitro inhibition of CRF receptor type 1 (CRFR1) within the LHb normalizes mTBI-induced enhancement of LHb tonic activity and hyperexcitability in both sexes, suggesting that an augmented intra-LHb CRF-CRFR1-mediated signaling contributes to the overall LHb hyperactivity following mTBI. Behaviorally, mTBI diminishes motivation for self-care grooming in female mice as in male mice. mTBI also alters defensive behaviors in the looming shadow task by shifting the innate defensive behaviors towards more passive action-locking rather than escape behaviors in response to an aerial threat in both male and female mice as well as prolonging the latency to escape responses in female mice. While, this model of mTBI reduces social preference in male mice, it induces higher social novelty seeking during the novel social encounters in both male and female mice. Overall, our study provides further translational validity for the use of this preclinical model of mTBI for investigation of mTBI-related reward circuit dysfunction and mood/motivation-related behavioral deficits in both sexes while uncovering a few sexually dimorphic neurobehavioral effects of this model that may differentially affect young males and females when exposed to this type of mTBI injury during late adolescence.

Twenty Years of Blast-Induced Neurotrauma: Current State of Knowledge

Blast-induced neurotrauma (BINT) is an important injury paradigm of neurotrauma research. This short communication summarizes the current knowledge of BINT. We divide the BINT research into several broad categories-blast wave generation in laboratory, biomechanics, pathology, behavioral outcomes, repetitive blast in animal models, and clinical and neuroimaging investigations in humans. Publications from 2000 to 2023 in each subdomain were considered. The analysis of the literature has brought out salient aspects. Primary blast waves can be simulated reasonably in a laboratory using carefully designed shock tubes. Various biomechanics-based theories of BINT have been proposed; each of these theories may contribute to BINT by generating a unique biomechanical signature. The injury thresholds for BINT are in the nascent stages. Thresholds for rodents are reasonably established, but such thresholds (guided by primary blast data) are unavailable in humans. Single blast exposure animal studies suggest dose-dependent neuronal pathologies predominantly initiated by blood-brain barrier permeability and oxidative stress. The pathologies were typically reversible, with dose-dependent recovery times. Behavioral changes in animals include anxiety, auditory and recognition memory deficits, and fear conditioning. The repetitive blast exposure manifests similar pathologies in animals, however, at lower blast overpressures. White matter irregularities and cortical volume and thickness alterations have been observed in neuroimaging investigations of military personnel exposed to blast. Behavioral changes in human cohorts include sleep disorders, poor motor skills, cognitive dysfunction, depression, and anxiety. Overall, this article provides a concise synopsis of current understanding, consensus, controversies, and potential future directions.

Repetitive, but Not Single, Mild Blast TBI Causes Persistent Neurological Impairments and Selective Cortical Neuronal Loss in Rats

Exposure to repeated mild blast traumatic brain injury (mbTBI) is common in combat soldiers and the training of Special Forces. Evidence suggests that repeated exposure to a mild or subthreshold blast can cause serious and long-lasting impairments, but the mechanisms causing these symptoms are unclear. In this study, we characterise the effects of single and tightly coupled repeated mbTBI in Sprague-Dawley rats exposed to shockwaves generated using a shock tube. The primary outcomes are functional neurologic function (unconsciousness, neuroscore, weight loss, and RotaRod performance) and neuronal density in brain regions associated with sensorimotor function. Exposure to a single shockwave does not result in functional impairments or histologic injury, which is consistent with a mild or subthreshold injury. In contrast, exposure to three tightly coupled shockwaves results in unconsciousness, along with persistent neurologic impairments. Significant neuronal loss following repeated blast was observed in the motor cortex, somatosensory cortex, auditory cortex, and amygdala. Neuronal loss was not accompanied by changes in astrocyte reactivity. Our study identifies specific brain regions particularly sensitive to repeated mbTBI. The reasons for this sensitivity may include exposure to less attenuated shockwaves or proximity to tissue density transitions, and this merits further investigation. Our novel model will be useful in elucidating the mechanisms of sensitisation to injury, the temporal window of sensitivity and the evaluation of new treatments.

High risk and low prevalence diseases: Blast injuries

INTRODUCTION

Blast injury is a unique condition that carries a high rate of morbidity and mortality, often with mixed penetrating and blunt injuries.

OBJECTIVE

This review highlights the pearls and pitfalls of blast injuries, including presentation, diagnosis, and management in the emergency department (ED) based on current evidence.

DISCUSSION

Explosions may impact multiple organ systems through several mechanisms. Patients with suspected blast injury and multisystem trauma require a systematic evaluation and resuscitation, as well as investigation for injuries specific to blast injuries. Blast injuries most commonly affect air-filled organs but can also result in severe cardiac and brain injury. Understanding blast injury patterns and presentations is essential to avoid misdiagnosis and balance treatment of competing interests of patients with polytrauma. Management of blast victims can also be further complicated by burns, crush injury, resource limitation, and wound infection. Given the significant morbidity and mortality associated with blast injury, identification of various injury patterns and appropriate management are essential.

CONCLUSIONS

An understanding of blast injuries can assist emergency clinicians in diagnosing and managing this potentially deadly disease.

Deployment-related concussion and long-term health-related quality of life among US military personnel

PURPOSE

To examine the relationship between deployment-related concussion and long-term health-related quality of life (HRQoL) among injured US military personnel.

METHODS

The study sample included 810 service members with deployment-related injuries between 2008 and 2012 who responded to a web-based longitudinal health survey. Participants were categorized into three injury groups: concussion with loss of consciousness (LOC; n = 247), concussion without LOC (n = 317), or no concussion (n = 246). HRQoL was measured using the 36-Item Short Form Health Survey physical and mental component summary (PCS and MCS) scores. Current post-traumatic stress disorder (PTSD) and depression symptoms were examined. Multivariable linear regression models assessed the effects of concussion on PCS and MCS scores, while controlling for covariates.

RESULTS

A lower PCS score was observed in participants with concussion with LOC (B =  - 2.65, p = 0.003) compared with those with no history of concussion. Symptoms of PTSD (PCS: B =  - 4.84, p < 0.001; MCS: B =  - 10.53, p < 0.001) and depression (PCS: B =  - 2.85, p < 0.001; MCS: B =  - 10.24, p < 0.001) were the strongest statistically significant predictors of lower HRQoL.

CONCLUSION

Concussion with LOC was significantly associated with lower HRQoL in the physical domain. These findings affirm that concussion management should integrate physical and psychological care to improve long-term HRQoL and warrant a more detailed examination of causal and mediating mechanisms. Future research should continue to incorporate patient-reported outcomes and long-term follow-up of military service members to further define the lifelong impact of deployment-related concussion.

The effectiveness of high-tone therapy in the complex rehabilitation of servicemen with post-traumatic stress disorder complicated by traumatic brain injury

INTRODUCTION

As a result of local military conflicts that have become more frequent over the past decades, the number of military personnel subjected to combat stress has sharply increased. More than 50% of them suffer from combat posttraumatic stress disorder. The most common comorbidity in this category of patients is a traumatic brain injury. Due to the undesirability of the long-term use of pharmacological agents, for rehabilitation, preference should be given to physiotherapeutic procedures.

OBJECTS AND METHODS

We examined 50 patients with post-traumatic stress disorder in combination with a closed craniocerebral injury. Group 1-25 patients received standard complex treatment at the sanatoriumresort rehabilitation stage (diet therapy, climatotherapy, balneotherapy, exercise therapy, psychotherapy). Group 2-25 patients, in addition to the standard complex treatment, received a course of high-tone therapy.

RESULTS

Complex rehabilitation of patients with the use of high-tone therapy contributes to a significant decrease in astheno-neurotic (p < 0.05) and asthenic depressive (p < 0.01) syndromes and has a psycho-relaxing effect on anxiety syndrome (p < 0.01). There was also a decrease in the severity of pyramidal symptoms and regression of the vestibulo-atactic syndrome (p < 0.05). The course application of hightone therapy was accompanied by a significant restoration of the elastotonic properties of the vascular wall and an improvement in cerebral perfusion (p < 0.05). Positive dynamics of electrophysiological indicators were noted: a decrease in the intensity of slow rhythms against the background of an increase in the frequency and intensity of the alpha rhythm in both hemispheres (p < 0.05), which indicates the harmonization of the bioelectrical activity of the brain.

Contributions of Hearing Loss and Traumatic Brain Injury to Blast-Induced Cortical Parvalbumin Neuron Loss and Auditory Processing Deficits

Auditory processing disorder is the most common problem affecting veterans after blast exposure, but the distinct impacts of blast-related traumatic brain injury and blast-related hearing loss are unknown. Independently, both hearing loss and blast exposure affect the entire auditory processing pathway at the molecular and physiological levels. Here, we identified distinct changes to the primary auditory cortex (AI) and temporal processing in mice following blast exposure both with and without protected hearing. Our results show that blast-exposure alone activated microglia in AI, but hearing loss was required for reductions in the density of parvalbumin-expressing interneurons. Although blast exposure impaired the temporal following response, these impairments were more severe with concurrent unilateral hearing loss, further resulting in impairments in behavioral gap detection. Taken together, these results indicate that protecting hearing during blast exposure can prevent most impairments to auditory processing but does not fully protect temporal processing.

Nanowired Delivery of Cerebrolysin with Mesenchymal Stem Cells Attenuates Heat Stress-Induced Exacerbation of Neuropathology Following Brain Blast Injury

Blast brain injury (bBI) following explosive detonations in warfare is one of the prominent causes of multidimensional insults to the central nervous and other vital organs injury. Several military personnel suffered from bBI during the Middle East conflict at hot environment. The bBI largely occurs due to pressure waves, generation of heat together with release of shrapnel and gun powders explosion with penetrating and/or impact head trauma causing multiple brain damage. As a result, bBI-induced secondary injury causes breakdown of the blood-brain barrier (BBB) and edema formation that further results in neuronal, glial and axonal injuries. Previously, we reported endocrine imbalance and influence of diabetes on bBI-induced brain pathology that was significantly attenuated by nanowired delivery of cerebrolysin in model experiments. Cerebrolysin is a balanced composition of several neurotrophic factors, and active peptide fragment is capable of neuroprotection in several neurological insults. Exposure to heat stress alone causes BBB damage, edema formation and brain pathology. Thus, it is quite likely that hot environment further exacerbates the consequences of bBI. Thus, novel therapeutic strategies using nanodelivery of stem cell and cerebrolysin may further enhance superior neuroprotection in bBI at hot environment. Our observations are the first to show that combined nanowired delivery of mesenchymal stem cells (MSCs) and cerebrolysin significantly attenuated exacerbation of bBI in hot environment and induced superior neuroprotection, not reported earlier. The possible mechanisms of neuroprotection with MSCs and cerebrolysin in bBI are discussed in the light of current literature.

Nanowired Delivery of Cerebrolysin Together with Antibodies to Amyloid Beta Peptide, Phosphorylated Tau, and Tumor Necrosis Factor Alpha Induces Superior Neuroprotection in Alzheimer's Disease Brain Pathology Exacerbated by Sleep Deprivation

Sleep deprivation induces amyloid beta peptide and phosphorylated tau deposits in the brain and cerebrospinal fluid together with altered serotonin metabolism. Thus, it is likely that sleep deprivation is one of the predisposing factors in precipitating Alzheimer's disease (AD) brain pathology. Our previous studies indicate significant brain pathology following sleep deprivation or AD. Keeping these views in consideration in this review, nanodelivery of monoclonal antibodies to amyloid beta peptide (AβP), phosphorylated tau (p-tau), and tumor necrosis factor alpha (TNF-α) in sleep deprivation-induced AD is discussed based on our own investigations. Our results suggest that nanowired delivery of monoclonal antibodies to AβP with p-tau and TNF-α induces superior neuroprotection in AD caused by sleep deprivation, not reported earlier.

Acute stress disorder in patients with accidental traumatic fractures: What can we do

AIM

To evaluate the potential influencing factors of acute stress disorder (ASD) in patients with accidental traumatic fractures to provide evidence for clinical nursing care.

DESIGN

A retrospective study.

METHODS

Patients with traumatic fractures treated in our hospital from 1 January 2020 to 30 November 2021 were included. The characteristics of ASD and no ASD patients were assessed.

RESULTS

A total of 468 patients with traumatic fractures were included, the incidence of ASD was 28.20%. Logistic regression analysis showed that age ≤50 years (OR2.918, 95% CI1.994 ~ 3.421), female (OR2.074, 95% CI1.489 ~ 3.375), AIS-ISS at admission ≥20 (OR3.981, 95% CI2.188 ~ 5.091), VAS at admission≥7 (OR2.804, 95% CI2.027 ~ 3.467), introverted personality (OR1.722, 95%CI1.314 ~ 2.432) and CD-RISC at admission≤60 (OR3.026, 95% CI2.338 ~ 4.769) were the risk factors of ASD in patients with traumatic fractures (all p < .05).

CONCLUSIONS

The development of ASD in patients with traumatic fractures is affected by multiple factors. Medical workers should take early and timely management and nursing measures for related risk factors to reduce the occurrence of ASD.

Limbic Responses Following Shock Wave Exposure in Male and Female Mice

Blast traumatic brain injury (bTBI) presents a serious threat to military personnel and often results in psychiatric conditions related to limbic system dysfunction. In this study, the functional outcomes for anxiety- and depressive-like behaviors and neuronal activation were evaluated in male and female mice after exposure to an Advanced Blast Simulator (ABS) shock wave. Mice were placed in a ventrally exposed orientation inside of the ABS test section and received primary and tertiary shock wave insults of approximately 15 psi peak pressure. Evans blue staining indicated cases of blood-brain barrier breach in the superficial cerebral cortex four, but not 24 h after blast, but the severity was variable. Behavioral testing with the elevated plus maze (EPM) or elevated zero maze (EZM), sucrose preference test (SPT), and tail suspension test (TST) or forced swim test (FST) were conducted 8 days–3.5 weeks after shock wave exposure. There was a sex difference, but no injury effect, for distance travelled in the EZM where female mice travelled significantly farther than males. The SPT and FST did not indicate group differences; however, injured mice were less immobile than sham mice during the TST; possibly indicating more agitated behavior. In a separate cohort of animals, the expression of the immediate early gene, c-Fos, was detected 4 h after undergoing bTBI or sham procedures. No differences in c-Fos expression were found in the cerebral cortex, but female mice in general displayed enhanced c-Fos activation in the paraventricular nucleus of the thalamus (PVT) compared to male mice. In the amygdala, more c-Fos-positive cells were observed in injured animals compared to sham mice. The observed sex differences in the PVT and c-Fos activation in the amygdala may correlate with the reported hyperactivity of females post-injury. This study demonstrates, albeit with mild effects, behavioral and neuronal activation correlates in female rodents after blast injury that could be relevant to the incidence of increased post-traumatic stress disorder in women.

Long-Term Effects of Low-Intensity Blast Non-Inertial Brain Injury on Anxiety-Like Behaviors in Mice: Home-Cage Monitoring Assessments

Mild traumatic brain injury induced by low-intensity blast (LIB) exposure poses concerns in military personnel. Using an open-field, non-inertial blast model and assessments by conventional behavioral tests, our previous studies revealed early-phase anxiety-like behaviors in LIB-exposed mice. However, the impact of LIB upon long-term anxiety-like behaviors requires clarification. This study applied a highly sensitive automated home-cage monitoring (HCM) system, which minimized human intervention and environmental changes, to assess anxiety-like responses in mice 3 months after LIB exposure. Initial assessment of 72-h spontaneous activities in a natural cage condition over multiple light and dark phases showed altered sheltering behaviors. LIB-exposed mice exhibited a subtle, but significantly decreased, duration of short shelter visits as compared to sham controls. Other measured responses between LIB-exposed mice and sham controls were insignificant. When behavioral assessments were performed in a challenged condition using an aversive spotlight, LIB-exposed mice demonstrated a significantly higher frequency of movements of shorter distance and duration per movement. Taken together, these findings demonstrated the presence of chronic anxiety-like behaviors assessed by the HCM system under both natural and challenged conditions in mice occurring post-LIB exposure. This model thus provides a platform to test for screening and interventions on anxiety disorders occurring after LIB non-inertial brain injury.

Health Profiles of Military Women and the Impact of Combat-Related Injury

PURPOSE

The role of women in the United States military is expanding. Women are now authorized to serve in all military occupations, including special operations and frontline combat units, which places them at increased risk of combat exposure and injury. Little is known regarding the impact of these injuries on the health of military women.

METHODS

We conducted a retrospective matched cohort study of women service members who were injured during combat operations in Iraq and Afghanistan. Injured women were individually matched to non-injured controls at a 1:4 ratio. Medical diagnostic codes were abstracted from outpatient encounters in electronic health records, and hierarchical clustering was conducted to identify clusters of diagnostic codes, termed "health profiles." Conditional logistic regression was used to determine whether combat-related injury predicted membership in the profiles.

RESULTS

The study sample included 590 injured women and 2360 non-injured controls. Cluster analysis identified six post-deployment health profiles: low morbidity, anxiety/headache, joint disorders, mixed musculoskeletal, pregnancy-related, and multimorbidity. Combat-related injury predicted membership in the anxiety/headache (odds ratio, 1.73; 95% confidence interval, 1.38-2.16) and multimorbidity (odds ratio, 3.43; 95% confidence interval, 2.65-4.43) profiles.

CONCLUSIONS

Combat-related injury is associated with adverse post-deployment health profiles among military women, and women with these profiles may experience increased health care burden. As future conflicts will likely see a greater number of women with combat exposure and injury, health outcomes research among military women is paramount for the purposes of medical planning and resource allocation.

Testing the blast response of foam inserts for helmets

Modern era combat helmets have different iterations and configurations to offer greater protection from blunt impact or ballistic penetration to suit the theatre of operation, although there are currently no standards for blast protection. Moreover, incorporation of blast protection into the same constrained mass-volume envelope is extremely challenging as there is very little space for a material to absorb or dissipate the shockwave. Foam padding is fitted in contemporary combat helmet designs for comfort and standoff purposes. Examples were subjected to blastwaves generated from an air-driven shocktube, along with open cell polyurethane foam specimens of varying pores per inch and thicknesses to. Whilst the range of samples tested did not afford any superior blast mitigation behaviour over the foam already present in helmets, they exhibited comparable performance with a lower mass. There also appears to be positive correlation between increased mass and increased impulse transmitted through the foam. The literature suggests that multiple mechanisms of damage for blast induced mild Traumatic Brain Injury (bTBI) can be caused by the helmet itself, therefore additional protection from a blunt or ballistic impact may increase the risk of damage from a blast insult.

Diabetes exacerbates brain pathology following a focal blast brain injury: New role of a multimodal drug cerebrolysin and nanomedicine

Blast brain injury (bBI) is a combination of several forces of pressure, rotation, penetration of sharp objects and chemical exposure causing laceration, perforation and tissue losses in the brain. The bBI is quite prevalent in military personnel during combat operations. However, no suitable therapeutic strategies are available so far to minimize bBI pathology. Combat stress induces profound cardiovascular and endocrine dysfunction leading to psychosomatic disorders including diabetes mellitus (DM). This is still unclear whether brain pathology in bBI could exacerbate in DM. In present review influence of DM on pathophysiology of bBI is discussed based on our own investigations. In addition, treatment with cerebrolysin (a multimodal drug comprising neurotrophic factors and active peptide fragments) or H-290/51 (a chain-breaking antioxidant) using nanowired delivery of for superior neuroprotection on brain pathology in bBI in DM is explored. Our observations are the first to show that pathophysiology of bBI is exacerbated in DM and TiO₂-nanowired delivery of cerebrolysin induces profound neuroprotection in bBI in DM, not reported earlier. The clinical significance of our findings with regard to military medicine is discussed.

Behavioral Deficits in Animal Models of Blast Traumatic Brain Injury

Blast exposure has been identified to be the most common cause for traumatic brain injury (TBI) in soldiers. Over the years, rodent models to mimic blast exposures and the behavioral outcomes observed in veterans have been developed extensively. However, blast tube design and varying experimental parameters lead to inconsistencies in the behavioral outcomes reported across research laboratories. This review aims to curate the behavioral outcomes reported in rodent models of blast TBI using shockwave tubes or open field detonations between the years 2008–2019 and highlight the important experimental parameters that affect behavioral outcome. Further, we discuss the role of various design parameters of the blast tube that can affect the nature of blast exposure experienced by the rodents. Finally, we assess the most common behavioral tests done to measure cognitive, motor, anxiety, auditory, and fear conditioning deficits in blast TBI (bTBI) and discuss the advantages and disadvantages of these tests.

Multimorbidity and quality of life after blast-related injury among US military personnel: a cluster analysis of retrospective data

Background

Blast injury emerged as a primary source of morbidity among US military personnel during the recent conflicts in Iraq and Afghanistan, and led to an array of adverse health outcomes. Multimorbidity, or the presence of two or more medical conditions in an individual, can complicate treatment strategies. To date, there is minimal research on the impact of multimorbidity on long-term patient-reported outcomes. We aimed to define multimorbidity patterns in a population of blast-injured military personnel, and to examine these patterns in relation to long-term quality of life (QOL).

Methods

A total of 1972 US military personnel who sustained a blast-related injury during military operations in Iraq and Afghanistan were identified from clinical records. Electronic health databases were used to identify medical diagnoses within the first year postinjury, and QOL was measured with a web-based assessment. Hierarchical cluster analysis methods using Ward’s minimum variance were employed to identify clusters with related medical diagnosis categories. Duncan’s multiple range test was used to group clusters into domains by QOL.

Results

Five distinct clusters were identified and grouped into three QOL domains. The lowest QOL domain contained one cluster with a clinical triad reflecting musculoskeletal pain, concussion, and mental health morbidity. The middle QOL domain had two clusters, one with concussion/anxiety predominating and the other with polytrauma. The highest QOL domain had two clusters with little multimorbidity aside from musculoskeletal pain.

Conclusions

The present study described blast-related injury profiles with varying QOL levels that may indicate the need for integrated health services. Implications exist for current multidisciplinary care of wounded active duty and veteran service members, and future research should determine whether multimorbidity denotes distinct post-blast injury syndromes.

Long-Term Effects of Blast Exposure: A Functional Study in Rats Using an Advanced Blast Simulator

Anecdotal observations of blast victims indicate that significant neuropathological and neurobehavioral defects may develop at later stages of life. To pre-clinically model this phenomenon, we have examined neurobehavioral changes in rats up to 1 year after exposure to single and tightly coupled repeated blasts using an advanced blast simulator. Neurobehavioral changes were monitored at acute, sub-acute, and chronic time-points using Morris water maze test of spatial learning and memory, novel object recognition test of short-term memory, open field exploratory activity as a test of anxiety/depression, a rotating pole test for vestibulomotor function, and a rotarod balance test for motor coordination. Single and repeated blasts resulted in significant functional deficits at both acute and chronic time-points. In most functional tests, rats exposed to repeated blasts performed more poorly than rats exposed to single blast. Interestingly, several functional deficits post-blast were most pronounced at 6 months and beyond. Significant neuromotor impairments occurred at early stages after blast exposure and the severity increased with repeated exposures. The novel object recognition testing revealed short-term memory deficits at 6 and 12 months post-blast. The water maze test revealed impairments at acute and chronic stages after blast exposure. The most substantial changes in the blast-exposed rats were observed with the center time and margin time legacies in the open field exploration test at 6, 9, and 12 months post-blast. Notably, these two outcome measures were minimally altered acutely, recovered during sub-acute stages, and were markedly affected during the chronic stages after blast exposures and may implicate development of chronic anxiety and depressive-like behaviors.

MRI-based measures of intracortical myelin are sensitive to a history of TBI and are associated with functional connectivity

Traumatic brain injuries (TBIs) induce persistent behavioral and cognitive deficits via diffuse axonal injury. Axonal injuries are often examined in vivo using diffusion MRI, which identifies damaged and demyelinated regions in deep white matter. However, TBI patients can exhibit impairment in the absence of diffusion-measured abnormalities, suggesting that axonal injury and demyelination may occur outside the deep white matter. Importantly, myelinated axons are also present within the cortex. Cortical myelination cannot be measured using diffusion imaging, but can be mapped in-vivo using the T1-w/T2-w ratio method. Here, we conducted the first work examining effects of TBI on intracortical myelin in living humans by applying myelin mapping to 46 US Military Veterans with a history of TBI. We observed that myelin maps could be created in TBI patients that matched known distributions of cortical myelin. After controlling for age and presence of blast injury, the number of lifetime TBIs was associated with reductions in the T1-w/T2-w ratio across the cortex, most significantly in a highly-myelinated lateral occipital region corresponding with the human MT+ complex. Further, the T1-w/T2-w ratio in this MT+ region predicted resting-state functional connectivity of that region. By contrast, a history of blast TBI did not affect the T1-w/T2-w ratio in either a diffuse or focal pattern. These findings suggest that intracortical myelin, as measured using the T1-w/T2-w ratio, may be a TBI biomarker that is anatomically complementary to diffusion MRI. Thus, myelin mapping could potentially be combined with diffusion imaging to improve MRI-based diagnostic tools for TBI.

Blast injuries in children: a mixed-methods narrative review

BACKGROUND AND SIGNIFICANCE

Blast injuries arising from high explosive weaponry is common in conflict areas. While blast injury characteristics are well recognised in the adults, there is a lack of consensus as to whether these characteristics translate to the paediatric population. Understanding blast injury patterns in this cohort is essential for providing appropriate provision of services and care for this vulnerable cohort.

METHODS

In this mixed-methods review, original papers were screened for data pertaining to paediatric injuries following blasts. Information on demographics, morbidity and mortality, and service requirements were evaluated. The papers were written and published in English from a range of international specialists in the field.

RESULTS

Children affected by blast injuries are predominantly male and their injuries arise from explosive remnants of war, particularly unexploded ordinance. Blasts show increased morbidity and mortality in younger children, while older children have injury patterns similar to adults. Head and burn injuries represent a significant cause of mortality in young children, while lower limb morbidity is reduced compared with adults. Children have a disproportionate requirement for both operative and non-operative service resources, and provisions for this burden are essential.

CONCLUSIONS

Certain characteristics of paediatric injuries arising from blasts are distinct from that of the adult cohort, while the intensive demands on services highlight the importance of understanding the diverse injury patterns in order to optimise future service provisions in caring for this child blast survivor.

Development of a Methodology for Simulating Complex Head Impacts With the Advanced Combat Helmet

Blunt impact assessment of the Advanced Combat Helmet (ACH) is currently based on the linear head response. The current study presents a methodology for testing the ACH under complex loading that generates linear and rotational head motion. Experiments were performed on a guided, free-fall drop tower using an instrumented National Operating Committee for Standards on Athletic Equipment (NOCSAE) head attached to a Hybrid III (HIII) or EuroSID-2 (ES-2) dummy neck and carriage. Rear and lateral impacts occurred at 3.0 m/s with peak linear accelerations (PLA) and peak rotational accelerations (PRA) measured at the NOCSAE head center-of-gravity. Experimental data served as inputs for the Simulated Injury Monitor (SIMon) computational model to estimate brain strain. Rear ACH impacts had 22% and 7% higher PLA and PRA when using the HIII neck versus the ES-2 neck. Lateral ACH impacts had 33% and 35% lower PLA and PRA when using HIII neck versus the ES-2 neck. Computational results showed that total estimated brain strain increased by 25% and 76% under rear and lateral ACH impacts when using the ES-2 neck. This methodology was developed to simulate complex ACH impacts involving the rotational head motion associated with diffuse brain injuries, including concussion, in military environments.

Repeated blast model of mild traumatic brain injury alters oxycodone self-administration and drug seeking

Each year, traumatic brain injuries (TBI) affect millions worldwide. Mild TBIs (mTBI) are the most prevalent and can lead to a range of neurobehavioral problems, including substance abuse. A single blast exposure, inducing mTBI alters the medial prefrontal cortex, an area implicated in addiction, for at least 30 days post injury in rats. Repeated blast exposures result in greater physiological and behavioral dysfunction than single exposure; however, the impact of repeated mTBI on addiction is unknown. In this study, the effect of mTBI on various stages of oxycodone use was examined. Male Sprague Dawley rats were exposed to a blast model of mTBI once per day for 3 days. Rats were trained to self-administer oxycodone during short (2 h) and long (6 h) access sessions. Following abstinence, rats underwent extinction and two cued reinstatement sessions. Sham and rbTBI rats had similar oxycodone intake, extinction responding and cued reinstatement of drug seeking. A second group of rats were trained to self-administer oxycodone with varying reinforcement schedules (fixed ratio (FR)-2 and FR-4). Under an FR-2 schedule, rbTBI-exposed rats earned fewer reinforcers than sham-exposed rats. During 10 extinction sessions, the rbTBI-exposed rats exhibited significantly more seeking for oxycodone than the sham-injured rats. There was a positive correlation between total oxycodone intake and day 1 extinction drug seeking in sham, but not in rbTBI-exposed rats. Together, this suggests that rbTBI-exposed rats are more sensitive to oxycodone-associated cues during reinstatement than sham-exposed rats and that rbTBI may disrupt the relationship between oxycodone intake and seeking.

Otopathologic Changes in the Cochlea following Head Injury without Temporal Bone Fracture

Objective

Hearing loss following temporal bone (TB) fracture may result from direct transection of the middle and inner ear. The pathophysiology of hearing loss due to head injury without TB fracture, however, is not well understood. Few reports describe otopathologic findings. Herein, we investigate the pathologic findings of patients who sustained a head injury without evidence of a TB fracture.

Study Design

Otopathology study.

Setting

Otopathology laboratory.

Subjects

Subjects with a history of head injury without TB fracture.

Methods

The TBs of patients with head injury were evaluated by light microscopy. Inner ear anatomy was evaluated, including counts of spiral ganglion cells (SGCs), hair cells, pillar cells, atrophy of the stria vascularis, and the presence of endolymphatic hydrops. SGC counts were compared with those of historical age-matched controls.

Results

All cases (N = 6 TBs) had evidence of inner ear pathology. Of the 6 cases, 2 (33%) had severe loss of hair cells in all 3 turns of the cochlea, and 4 (67%) cases demonstrated moderate to severe loss at the basal turn of the cochlea. Four cases had scattered atrophy of the stria vascularis, and 3 (50%) had cochlear hydrops. The number of total SGCs was decreased, with an average 53% loss (range, 25%-79%) as compared with controls. The SGC count loss was evenly distributed along Rosenthal’s canal.

Conclusions

Patients with a history of head injury without TB fracture demonstrate inner ear pathology. Further studies are necessary to determine if otopathology findings are directly attributable to trauma.

Blast Exposure Disrupts the Tonotopic Frequency Map in the Primary Auditory Cortex

Blast exposure can cause various auditory disorders including tinnitus, hyperacusis, and other central auditory processing disorders. While this is suggestive of pathologies in the central auditory system, the impact of blast exposure on central auditory processing remains poorly understood. Here we examined the effects of blast shockwaves on acoustic response properties and the tonotopic frequency map in the auditory cortex. We found that multiunits recorded from the auditory cortex exhibited higher acoustic thresholds and broader frequency tuning in blast-exposed animals. Furthermore, the frequency map in the primary auditory cortex was distorted. These changes may contribute to central auditory processing disorders.

High-Fidelity Measures of Whole-Brain Functional Connectivity and White Matter Integrity Mediate Relationships between Traumatic Brain Injury and Post-Traumatic Stress Disorder Symptoms

Traumatic brain injury (TBI) disrupts brain communication and increases risk for post-traumatic stress disorder (PTSD). However, mechanisms by which TBI-related disruption of brain communication confers PTSD risk have not been successfully elucidated in humans. This may be in part because functional MRI (fMRI), the most common technique for measuring functional brain communication, is unreliable for characterizing individual patients. However, this unreliability can be overcome with sufficient within-individual data. Here, we examined whether relationships could be observed among TBI, structural and functional brain connectivity, and PTSD severity by collecting ∼3.5 hours of resting-state fMRI and diffusion tensor imaging (DTI) data in each of 26 United States military veterans. We observed that a TBI history was associated with decreased whole-brain resting-state functional connectivity (RSFC), while the number of lifetime TBIs was associated with reduced whole-brain fractional anisotropy (FA). Both RSFC and FA explained independent variance in PTSD severity, with RSFC mediating the TBI-PTSD relationship. Finally, we showed that large amounts of per-individual data produced highly reliable RSFC measures, and that relationships among TBI, RSFC/FA, and PTSD could not be observed with typical data quantities. These results demonstrate links among TBI, brain connectivity, and PTSD severity, and illustrate the need for precise characterization of individual patients using high-data fMRI scanning.

Sensory coding and cognitive processing of sound in Veterans with blast exposure

Recent anecdotal reports from VA audiology clinics as well as a few published studies have identified a sub-population of Service Members seeking treatment for problems communicating in everyday, noisy listening environments despite having normal to near-normal hearing thresholds. Because of their increased risk of exposure to dangerous levels of prolonged noise and transient explosive blast events, communication problems in these soldiers could be due to either hearing loss (traditional or "hidden") in the auditory sensory periphery or from blast-induced injury to cortical networks associated with attention. We found that out of the 14 blast-exposed Service Members recruited for this study, 12 had hearing thresholds in the normal to near-normal range. A majority of these participants reported having problems specifically related to failures with selective attention. Envelope following responses (EFRs) measuring neural coding fidelity of the auditory brainstem to suprathreshold sounds were similar between blast-exposed and non-blast controls. Blast-exposed subjects performed substantially worse than non-blast controls in an auditory selective attention task in which listeners classified the melodic contour (rising, falling, or "zig-zagging") of one of three simultaneous, competing tone sequences. Salient pitch and spatial differences made for easy segregation of the three concurrent melodies. Poor performance in the blast-exposed subjects was associated with weaker evoked response potentials (ERPs) in frontal EEG channels, as well as a failure of attention to enhance the neural responses evoked by a sequence when it was the target compared to when it was a distractor. These results suggest that communication problems in these listeners cannot be explained by compromised sensory representations in the auditory periphery, but rather point to lingering blast-induced damage to cortical networks implicated in the control of attention. Because all study participants also suffered from post-traumatic disorder (PTSD), follow-up studies are required to tease apart the contributions of PTSD and blast-induced injury on cognitive performance.

Subacute Oxidative Stress and Glial Reactivity in the Amygdala are Associated with Increased Anxiety Following Blast Neurotrauma

Behavioral symptoms, such as anxiety, are widely reported after blast overpressure (BOP) exposure. Amygdalar vulnerability to increasing magnitudes of BOP has not been investigated, and single exposures to blast have been limited to acute (<72 h) assessment. Rats were exposed to a single low, moderate, or high BOP (10, 14, or 24 psi) with an advanced blast simulator to test the susceptibility of the amygdala. Anxiety-like behavior was observed in the low- and moderate-pressure groups when subjected to the light/dark box assessment 7 days after the blast but not in high-pressure group. Immunohistochemistry was performed to measure apoptosis (cleaved caspase-3), neuronal loss (NeuN), reactive astrocytes (glial fibrillary acidic protein), microglia (Iba-1), and oxidative stress (CuZn superoxide dismutase). Slower progression of injury cascades was associated with a significant increase in anxiety, apoptosis, and astrogliosis in the low pressure group compared with others. A significant increase of CuZn superoxide dismutase in the low pressure group could be associated with neuroprotection from cell death caused by oxidative stress because neuronal loss was significant in the moderate- and high- but not the low-pressure group. Overall, this study demonstrated that overpressure as low as 10 psi can induce subacute anxiety, in addition to neuropathologic changes in the amygdala.

Amplitude of Low-Frequency Fluctuations in Multiple-Frequency Bands in Acute Mild Traumatic Brain Injury

Functional disconnectivity during the resting state has been observed in mild traumatic brain injury (mTBI) patients during the acute stage. However, it remains largely unknown whether the abnormalities are related to specific frequency bands of the low-frequency oscillations (LFO). Here, we used the amplitude of low-frequency fluctuations (ALFF) to examine the amplitudes of LFO in different frequency bands (slow-5: 0.01–0.027 Hz; slow-4: 0.027–0.073 Hz; and typical: 0.01–0.08 Hz) in patients with acute mTBI. A total of 24 acute mTBI patients and 24 age-, sex-, and education-matched healthy controls participated in this study. In the typical band, acute mTBI patients showed lower standardized ALFF in the right middle frontal gyrus and higher standardized ALFF in the right lingual/fusiform gyrus and left middle occipital gyrus. Further analyses showed that the difference between groups was concentrated in a narrower (slow-4) frequency band. In the slow-5 band, mTBI patients only exhibited higher standardized ALFF in the occipital areas. No significant correlation between the mini-mental state examination score and the standardized ALFF value was found in any brain region in the three frequency bands. Finally, no significant interaction between frequency bands and groups was found in any brain region. We concluded that the abnormality of spontaneous brain activity in acute mTBI patients existed in the frontal lobe as well as in distributed brain regions associated with integrative, sensory, and emotional roles, and the abnormal spontaneous neuronal activity in different brain regions could be better detected by the slow-4 band. These findings might contribute to a better understanding of local neural psychopathology of acute mTBI. Future studies should take the frequency bands into account when measuring intrinsic brain activity of mTBI patients.

Blast Injuries

BACKGROUND

Blast injuries in the United States and worldwide are not uncommon. Partially due to the increasing frequency of both domestic and international terrorist bombing attacks, it is prudent for all emergency physicians to be knowledgeable about blasts and the spectrum of associated injuries.

OBJECTIVE

Our aim was to describe blast physiology, types of blast injuries associated with each body system, and manifestations and management of each injury.

DISCUSSION

Blast injuries are generally categorized as primary to quaternary injuries. Primary injuries result from the effect of transmitted blast waves on gas-containing structures, secondary injuries result from the impact of airborne debris, tertiary injury results from transposition of the entire body due to blast wind or structural collapse, and quaternary injuries include almost everything else. Different body systems are affected and managed differently. Despite previous dogma, multiple studies now show that tympanic membrane perforation is a poor predictor of other blast injury.

CONCLUSIONS

Blast events can produce a myriad of injuries affecting any and every body system. All emergency physicians should be familiar with the presentation and management of these injuries. This knowledge may also be incorporated into triage and discharge protocols guiding management of mass casualty events.

Advances in imaging explosive blast mild traumatic brain injury

In the past, direct physical evidence of mild traumatic brain injury (mTBI) from explosive blast has been difficult to obtain through conventional imaging modalities such as T1- and T2-weighted magnetic resonance imaging (MRI) and computed tomography (CT). Here, we review current progress in detecting evidence of brain injury from explosive blast using advanced imaging, including diffusion tensor imaging (DTI), functional MRI (fMRI), and the metabolic imaging methods such as positron emission tomography (PET) and magnetic resonance spectroscopic imaging (MRSI), where each targets different aspects of the pathology involved in mTBI. DTI provides a highly sensitive measure to detect primary changes in the microstructure of white matter tracts. fMRI enables the measurement of changes in brain activity in response to different stimuli or tasks. Remarkably, all three of these paradigms have found significant success in conventional mTBI where conventional clinical imaging frequently fails to provide definitive differences. Additionally, although used less frequently for conventional mTBI, PET has the potential to characterize a variety of neurotransmitter systems using target agents and will undoubtedly play a larger role, once the basic mechanisms of injury are better understood and techniques to identify the injury are more common. Finally, our MRSI imaging studies, although acquired at much lower spatial resolution, have demonstrated selectivity to different metabolic and physiologic processes, uncovering some of the most profound differences on an individual by individual basis, suggesting the potential for utility in the management of individual patients.

PTSD and TBI co-morbidity: scope, clinical presentation and treatment options

PRIMARY OBJECTIVE

To summarize the literature on post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI) and their co-morbidity, focusing on diagnosis, clinical symptoms and treatment issues relevant to the clinician.

RESEARCH DESIGN

Review of the literature.

METHODS AND PROCEDURES

Pubmed searches were performed using the terms post-traumatic stress disorder, traumatic brain injury, sleep, cognitive, depression, anxiety, treatment and combinations of these terms. Those articles relevant to the objective were included.

MAIN OUTCOMES AND RESULTS

This study presents pathophysiological, neuroimaging and clinical data on co-morbid PTSD and TBI. It reviews associated conditions, emphasizing the impact of cognitive and sleep problems. It summarizes the emerging literature on treatment effectiveness for co-morbid PTSD and TBI, including psychotherapy, pharmacotherapy and cognitive rehabilitation.

CONCLUSIONS

Both PTSD and TBI commonly occur in the general population, both share some pathophysiological characteristics and both are associated with cognitive impairment and sleep disruption. PTSD and TBI present with a number of overlapping symptoms, which can lead to over-diagnosis or misdiagnosis. Both conditions are associated with co-morbidities important in diagnosis and treatment planning. More research is needed to elucidate what treatments are effective in PTSD and TBI co-morbidity and on factors predictive of treatment success.

Concussive brain injury from explosive blast

OBJECTIVE

Explosive blast mild traumatic brain injury (mTBI) is associated with a variety of symptoms including memory impairment and posttraumatic stress disorder (PTSD). Explosive shock waves can cause hippocampal injury in a large animal model. We recently reported a method for detecting brain injury in soldiers with explosive blast mTBI using magnetic resonance spectroscopic imaging (MRSI). This method is applied in the study of veterans exposed to blast.

METHODS

The hippocampus of 25 veterans with explosive blast mTBI, 20 controls, and 12 subjects with PTSD but without exposure to explosive blast were studied using MRSI at 7 Tesla. Psychiatric and cognitive assessments were administered to characterize the neuropsychiatric deficits and compare with findings from MRSI.

RESULTS

Significant reductions in the ratio of N-acetyl aspartate to choline (NAA/Ch) and N-acetyl aspartate to creatine (NAA/Cr) (P < 0.05) were found in the anterior portions of the hippocampus with explosive blast mTBI in comparison to control subjects and were more pronounced in the right hippocampus, which was 15% smaller in volume (P < 0.05). Decreased NAA/Ch and NAA/Cr were not influenced by comorbidities - PTSD, depression, or anxiety. Subjects with PTSD without blast had lesser injury, which tended to be in the posterior hippocampus. Explosive blast mTBI subjects had a reduction in visual memory compared to PTSD without blast.

INTERPRETATION

The region of the hippocampus injured differentiates explosive blast mTBI from PTSD. MRSI is quite sensitive in detecting and localizing regions of neuronal injury from explosive blast associated with memory impairment.

Blood brain barrier dysfunction and delayed neurological deficits in mild traumatic brain injury induced by blast shock waves

Mild traumatic brain injury (mTBI) resulting from exposure to blast shock waves (BSWs) is one of the most predominant causes of illnesses among veterans who served in the recent Iraq and Afghanistan wars. Such mTBI can also happen to civilians if exposed to shock waves of bomb attacks by terrorists. While cognitive problems, memory dysfunction, depression, anxiety and diffuse white matter injury have been observed at both early and/or delayed time-points, an initial brain pathology resulting from exposure to BSWs appears to be the dysfunction or disruption of the blood-brain barrier (BBB). Studies in animal models suggest that exposure to relatively milder BSWs (123 kPa) initially induces free radical generating enzymes in and around brain capillaries, which enhances oxidative stress resulting in loss of tight junction (TJ) proteins, edema formation, and leakiness of BBB with disruption or loss of its components pericytes and astrocyte end-feet. On the other hand, exposure to more intense BSWs (145-323 kPa) causes acute disruption of the BBB with vascular lesions in the brain. Both of these scenarios lead to apoptosis of endothelial and neural cells and neuroinflammation in and around capillaries, which may progress into chronic traumatic encephalopathy (CTE) and/or a variety of neurological impairments, depending on brain regions that are afflicted with such lesions. This review discusses studies that examined alterations in the brain milieu causing dysfunction or disruption of the BBB and neuroinflammation following exposure to different intensities of BSWs. Furthermore, potential of early intervention strategies capable of easing oxidative stress, repairing the BBB or blocking inflammation for minimizing delayed neurological deficits resulting from exposure to BSWs is conferred.

Lower health related quality of life in U.S. military personnel is associated with service-related disorders and inflammation

Military personnel who have combat exposures are at increased risk for the service-related disorders of post-traumatic stress disorder (PTSD), depression, sleep disturbances and decreased health related quality of life (HRQOL). Those with a traumatic brain injury (TBI) are at even greater risk. Inflammation is associated with these disorders and may underlie the risk for health declines. We evaluated 110 recently deployed, military personnel presenting with sleep disturbances for service-related disorders (TBI, PTSD, and depression) as well as HRQOL. ANOVA models were used to examine differences among military personnel with two or more service-related disorders (high comorbid group), or one or no disorders (low comorbid group). Logistic regression models were used to determine associations among interleukin-6 (IL-6) to HRQOL and service-related disorders. Approximately one-third of the sample had two or more service-related disorders. HRQOL was lower and IL-6 concentrations were higher in military personnel with PTSD or depression, with the most profound differences in those with more service-related disorders, regardless of sleep disorder. Having symptoms of depression and PTSD resulted in a 3.5-fold risk to be in the lower quartile of HRQOL and the highest quartile of IL-6. In a linear regression model, 41% of the relationship between HRQOL and IL-6 concentrations was mediated by PTSD and depression. Military personnel with PTSD and depression are at high risk for lower HRQOL, and higher IL-6 concentrations. Comprehensive treatment is required to address co-occurring service-related disorders in military personnel to promote health and well-being.

Hippocampal vulnerability and subacute response following varied blast magnitudes

Clinical outcomes from blast neurotrauma are associated with higher order cognitive functions such as memory, problem solving skills and attention. Current literature is limited to a single overpressure exposure or repeated exposures at the same level of overpressure and is focused on the acute response (<3 days). In an attempt to expand the understanding of neuropathological and molecular changes of the subacute response (7 days post injury), we used an established rodent model of blast neurotrauma. Three pressure magnitudes (low, moderate and high) were used to evaluate molecular injury thresholds. Immunohistochemical analysis demonstrated increased cleaved caspase-3 levels and loss of neuronal population (NeuN+) within the hippocampus of all pressure groups. On the contrary, selective activation of microglia was observed in the low blast group. In addition, increased astrocytes (GFAP), membrane signal transduction protein (Map2k1) and calcium regulator mechanosensitive protein (Piezo 2) were observed in the moderate blast group. Results from gene expression analysis suggested ongoing neuroprotection, as brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF) and Mn and CuZn superoxide dismutases (SOD) all increased in the low and moderate blast groups. Ongoing neuroprotection was further supported by increased SOD levels observed in the moderate group using immunohistochemistry. The gene expression level of glutamate aspartate transporter (GLAST) was upregulated in the low, but downregulated in the high blast group, while no changes were found in the moderate group. Overall, the data shown here provides evidence of a diverse neuroprotective and glial response to various levels of blast exposure. This mechanistic role of neuroprotection is vital in understanding ongoing cellular stress, both at the gene and protein levels, in order to develop interventional studies for the prognosis of injury.

MRSI of the medial temporal lobe at 7 T in explosive blast mild traumatic brain injury

PURPOSE

Up to 19% of veterans returning from the wars in Iraq and Afghanistan have a history of mild traumatic brain injury with 70% associated with blast exposure. Tragically, 20-50% of this group reports persistent symptoms, including memory loss. Unfortunately, routine clinical imaging is typically normal, making diagnosis and clinical management difficult. The goal of this work was to develop methods to acquire hippocampal MRSI at 7 T and evaluate their sensitivity to detect injury in veterans with mild traumatic brain injury.

METHODS

At 7 T, hippocampal MRSI measurements are limited by: (1) poor B(0) homogeneity; (2) insufficient B(1)(+) strength and homogeneity; and (3) chemical shift dispersion artifacts. To overcofme these limitations we: (1) used third degree B(0) shimming; (2) an inductively decoupled transceiver array with radiofrequency shimming; and (3) a volume localized single slice sequence using radiofrequency shimming-based outer volume suppression.

RESULTS

In 20 controls and 25 veterans with mild traumatic brain injury due to blast exposure with memory impairment, hippocampal N-acetyl aspartate to choline (P < 0.001) and N-acetyl aspartate to creatine (P < 0.001) were decreased in comparison to control subjects.

CONCLUSION

With the appropriate methods robust spectroscopic imaging of the hippocampus can be carried out at 7 T. MRSI at 7 T can detect hippocampal injury in veterans with mild traumatic brain injury.

Repeated primary blast injury causes delayed recovery, but not additive disruption, in an in vitro blood-brain barrier model

Recent studies have demonstrated increased susceptibility to breakdown of the cerebral vasculature associated with repetitive traumatic brain injury. We hypothesized that exposure to two consecutive blast injuries would result in exacerbated damage to an in vitro model of the blood-brain barrier (BBB) compared with exposure to a single blast of the same severity. Contrary to our hypothesis, however, repeated mild or moderate primary blast delivered with a 24 or 72 h interval between injuries did not significantly exacerbate reductions in transendothelial electrical resistance (TEER) across a brain endothelial monolayer compared with sister cultures receiving a single exposure of the same intensity. Permeability of the barrier to a range of different-sized solutes remained unaltered after single and repeated blast, supporting that the effects of repeated blast on BBB integrity were not additive. Single blast exposure significantly reduced immunostaining of ZO-1 and claudin-5 tight junction proteins, but subsequent exposure did not cause additional damage to tight junctions. Although repeated blast did not further reduce TEER, the second exposure delayed TEER recovery in BBB cultures. Similarly, recovery of hydraulic conductivity through the BBB was delayed by a second exposure. Extending the interinjury interval to 72 h, the effects of multiple injuries on the BBB were found to be independent given sufficient recovery time between consecutive exposures. Careful investigation of the effects of repeated blast on the BBB will help identify injury levels and a temporal window of vulnerability associated with BBB dysfunction, ultimately leading to improved strategies for protecting warfighters against repeated blast-induced disruption of the cerebral vasculature.

Blast neurotrauma impairs working memory and disrupts prefrontal myo-inositol levels in rats

Working memory, which is dependent on higher-order executive function in the prefrontal cortex, is often disrupted in patients exposed to blast overpressure. In this study, we evaluated working memory and medial prefrontal neurochemical status in a rat model of blast neurotrauma. Adult male Sprague-Dawley rats were anesthetized with 3% isoflurane and exposed to calibrated blast overpressure (17 psi, 117 kPa) while sham animals received only anesthesia. Early neurochemical effects in the prefrontal cortex included a significant decrease in betaine (trimethylglycine) and an increase in GABA at 24 h, and significant increases in glycerophosphorylcholine, phosphorylethanolamine, as well as glutamate/creatine and lactate/creatine ratios at 48 h. Seven days after blast, only myo-inositol levels were altered showing a 15% increase. Compared to controls, short-term memory in the novel object recognition task was significantly impaired in animals exposed to blast overpressure. Working memory in control animals was negatively correlated with myo-inositol levels (r=-.759, p<0.05), an association that was absent in blast exposed animals. Increased myo-inositol may represent tardive glial scarring in the prefrontal cortex, a notion supported by GFAP changes in this region after blast overexposure as well as clinical reports of increased myo-inositol in disorders of memory.

Altering endoplasmic reticulum stress in a model of blast-induced traumatic brain injury controls cellular fate and ameliorates neuropsychiatric symptoms

Neuronal injury following blast-induced traumatic brain injury (bTBI) increases the risk for neuropsychiatric disorders, yet the pathophysiology remains poorly understood. Blood-brain-barrier (BBB) disruption, endoplasmic reticulum (ER) stress, and apoptosis have all been implicated in bTBI. Microvessel compromise is a primary effect of bTBI and is postulated to cause subcellular secondary effects such as ER stress. What remains unclear is how these secondary effects progress to personality disorders in humans exposed to head trauma. To investigate this we exposed male rats to a clinically relevant bTBI model we have recently developed. The study examined initial BBB disruption using Evan's blue (EB), ER stress mechanisms, apoptosis and impulsive-like behavior measured with elevated plus maze (EPM). Large BBB openings were observed immediately following bTBI, and persisted for at least 6 h. Data showed increased mRNA abundance of stress response genes at 3 h, with subsequent increases in the ER stress markers C/EBP homologous protein (CHOP) and growth arrest and DNA damage-inducible protein 34 (GADD34) at 24 h. Caspase-12 and Caspase-3 were both cleaved at 24 h following bTBI. The ER stress inhibitor, salubrinal (SAL), was administered (1 mg/kg i.p.) to investigate its effects on neuronal injury and impulsive-like behavior associated with bTBI. SAL reduced CHOP protein expression, and diminished Caspase-3 cleavage, suggesting apoptosis attenuation. Interestingly, SAL also ameliorated impulsive-like behavior indicative of head trauma. These results suggest SAL plays a role in apoptosis regulation and the pathology of chronic disease. These observations provide evidence that bTBI involves ER stress and that the unfolded protein response (UPR) is a promising molecular target for the attenuation of neuronal injury.

Correlation of otologic complaints in soldiers with speech disorders after traumatic brain injury

OBJECTIVES/HYPOTHESIS

To determine the prevalence of otologic complaints in subjects with dysphonia and traumatic brain injury (TBI) in a sample population of the US Army.

STUDY DESIGN

Cross-sectional study.

METHODS

A total of 292 subjects were identified with a new diagnosis of voice disorder during a 3.5-year period at three large military medical centers. Of them, 70 subjects were also identified with TBI and had no history of dysphonia before this time period. In those with voice disorders and TBI, documentation of hearing complaints, hearing loss, tinnitus, or vertigo was recorded. Time to visit an otolaryngologist and audiologist were also recorded.

RESULTS

A total of 70 soldiers were identified with a diagnosis of a voice disorder and TBI. Of these soldiers, 83% had at least one otologic complaint and 50% had more than one. Approximately 60%, 39%, and 44% of the subjects reported tinnitus, hearing loss, or vertigo, respectively. A total of 62% of the subjects with otologic complaints, TBI, and dysphonia were seen by an otolaryngologist. Time until an otolaryngologist evaluated these soldiers varied widely, with an average of 17 months and standard deviation of 12.5 months.

CONCLUSIONS

Otologic manifestations are common in soldiers with dysphonia and TBI. Careful consideration of communication impairment from otologic dysfunction in those with speech disorders after TBI is warranted.