Emergence of cognitive deficits after mild traumatic brain injury due to hyperthermia

Reduced Concussion Symptom Burden in Early Adolescent Athletes Using a Head-Neck Cooling Device

OBJECTIVE

To determine whether an investigational head-neck cooling device, Pro2cool, can better reduce symptom severity compared with standard postconcussion care in early adolescent athletes after a sports-related concussion.

DESIGN

Prospective, longitudinal, randomized trial design conducted over a 28-day period.

SETTING

Six pediatric medical centers in Ohio and Michigan.

PARTICIPANTS

The study enrolled 167 male and female 12- to 19-year-old athletes who experienced a sports-related concussion within 8 days of study enrollment and registering a Sports Concussion Assessment Tool 5 (SCAT5) composite score >7.

INTERVENTIONS

Pro2cool, an investigational head-neck cooling therapy device, was applied at 2 postinjury time points compared with postconcussion standard of care only.

MAIN OUTCOME MEASURES

Baseline SCAT5 composite symptom severity scores were determined for all subjects. Sports Concussion Assessment Tool 5 scores for concussed athletes receiving cooling treatment were analyzed across 6 independent postenrollment time points compared with subjects who did not receive cooling therapy and only standard care. Adverse reactions and participate demographics were also compared.

RESULTS

Athletes who received Pro2cool cooling therapy (n = 79) experienced a 14.4% greater reduction in SCAT5 symptom severity scores at the initial visit posttreatment, a 25.5% greater reduction at the 72-hour visit posttreatment, and a 3.4% greater reduction at the 10-day visit compared with subjects receiving only standard care (n = 88). Overall, 36 adverse events (increased blood pressure, decreased pulse, and dizziness) were reported, with 13 events associated with the device, of which 3 were classified as moderate in severity.

CONCLUSIONS

This study demonstrates the efficacy and safety of head and neck cooling for the management of concussion symptoms in adolescent athletes of an age group for which little to no prior data are available.

Selective head cooling in the acute phase of concussive injury: a neuroimaging study

Introduction

Neurovascular decoupling is a common consequence after brain injuries like sports-related concussion. Failure to appropriately match cerebral blood flow (CBF) with increases in metabolic demands of the brain can lead to alterations in neurological function and symptom presentation. Therapeutic hypothermia has been used in medicine for neuroprotection and has been shown to improve outcome. This study aimed to examine the real time effect of selective head cooling on healthy controls and concussed athletes via magnetic resonance spectroscopy (MRS) and arterial spin labeling (ASL) measures.

Methods

24 participants (12 controls; 12 concussed) underwent study procedures including the Post-Concussion Symptom Severity (PCSS) Rating Form and an MRI cooling protocol (pre-cooling (T1 MPRAGE, ASL, single volume spectroscopy (SVS)); during cooling (ASL, SVS)).

Results

Results showed general decreases in brain temperature as a function of time for both groups. Repeated measures ANOVA showed a significant main effect of time (F = 7.94, p < 0.001) and group (F = 22.21, p < 0.001) on temperature, but no significant interaction of group and time (F = 1.36, p = 0.237). CBF assessed via ASL was non-significantly lower in concussed individuals at pre-cooling and generalized linear mixed model analyses demonstrated a significant main effect of time for the occipital left ROI (F = 11.29, p = 0.002) and occipital right ROI (F = 13.39, p = 0.001). There was no relationship between any MRI metric and PCSS symptom burden.

Discussion

These findings suggest the feasibility of MRS thermometry to monitor alterations of brain temperature in concussed athletes and that metabolic responses in response to cooling after concussion may differ from controls.

Neurodegenerative Diseases: Implications of Environmental and Climatic Influences on Neurotransmitters and Neuronal Hormones Activities

Neurodegenerative and neuronal-related diseases are major public health concerns. Human vulnerability to neurodegenerative diseases (NDDs) increases with age. Neuronal hormones and neurotransmitters are major determinant factors regulating brain structure and functions. The implications of environmental and climatic changes emerged recently as influence factors on numerous diseases. However, the complex interaction of neurotransmitters and neuronal hormones and their depletion under environmental and climatic influences on NDDs are not well established in the literature. In this review, we aim to explore the connection between the environmental and climatic factors to NDDs and to highlight the available and potential therapeutic interventions that could use to improve the quality of life and reduce susceptibility to NDDs.

Axonal injury following mild traumatic brain injury is exacerbated by repetitive insult and is linked to the delayed attenuation of NeuN expression without concomitant neuronal death in the mouse

Mild traumatic brain injury (mTBI) affects brain structure and function and can lead to persistent abnormalities. Repetitive mTBI exacerbates the acute phase response to injury. Nonetheless, its long‐term implications remain poorly understood, particularly in the context of traumatic axonal injury (TAI), a player in TBI morbidity via axonal disconnection, synaptic loss and retrograde neuronal perturbation. In contrast to the examination of these processes in the acute phase of injury, the chronic‐phase burden of TAI and/or its implications for retrograde neuronal perturbation or death have received little consideration. To critically assess this issue, murine neocortical tissue was investigated at acute (24‐h postinjury, 24hpi) and chronic time points (28‐days postinjury, 28dpi) after singular or repetitive mTBI induced by central fluid percussion injury (cFPI). Neurons were immunofluorescently labeled for NeuroTrace and NeuN (all neurons), p‐c‐Jun (axotomized neurons) and DRAQ5 (cell nuclei), imaged in 3D and quantified in automated manner. Single mTBI produced axotomy in 10% of neurons at 24hpi and the percentage increased after repetitive injury. The fraction of p‐c‐Jun+ neurons decreased at 28dpi but without neuronal loss (NeuroTrace), suggesting their reorganization and/or repair following TAI. In contrast, NeuN+ neurons decreased with repetitive injury at 24hpi while the corresponding fraction of NeuroTrace+ neurons decreased over 28dpi. Attenuated NeuN expression was linked exclusively to non‐axotomized neurons at 24hpi which extended to the axotomized at 28dpi, revealing a delayed response of the axotomized neurons. Collectively, we demonstrate an increased burden of TAI after repetitive mTBI, which is most striking in the acute phase response to the injury. Our finding of widespread axotomy in large fields of intact neurons contradicts the notion that repetitive mTBI elicits progressive neuronal death, rather, emphasizing the importance of axotomy‐mediated change.

Climate change and neurodegenerative diseases

The climate change induced global warming, and in particular the increased frequency and intensity of heat waves, have been linked to health problems. Among them, scientific works have been reporting an increased incidence of neurological diseases, encompassing also neurodegenerative ones, such as Dementia of Alzheimer's type, Parkinson's Disease, and Motor Neuron Diseases. Although the increase in prevalence of neurodegenerative diseases is well documented by literature reports, the link between global warming and the enhanced prevalence of such diseases remains elusive. This is the main theme of our work, which aims to examine the connection between high temperature exposure and neurodegenerative diseases. Firstly, we evaluate the influence of high temperatures exposure on the pathophysiology of these disorders. Secondly, we discuss its effects on the thermoregulation, already compromised in affected patients, and its interference with processes of excitotoxicity, oxidative stress and neuroinflammation, all of them related with neurodegeneration. Finally, we investigate chronic versus acute stressors on body warming, and put forward a possible interpretation of the beneficial or detrimental effects on the brain, which is responsible for the incidence or progression of neurological disorders.

Selective head-neck cooling after concussion shortens return-to-play in ice hockey players

We aimed to investigate whether selective head–neck cooling could shorten recovery after sports-related concussions (SRCs). In a nonrandomized study of 15 Swedish professional ice hockey teams, 29 concussed players received immediate head and neck cooling for ≥30 min (initiated at 12.3 ± 9.2 min post-SRC by a portable cooling system), and 52 SRC controls received standard management. Players receiving head–neck cooling had shorter time to return-to-play than controls (7 vs 12.5 days, p < 0.0001), and 7% in the intervention group versus 25% in the control group were out of play for ≥3 weeks (p = 0.07). Immediate selective head–neck cooling is a promising option in the acute management of SRC that should be addressed in larger cohorts.

An Exploratory Report on Electrographic Changes in the Cerebral Cortex Following Mild Traumatic Brain Injury with Hyperthermia in the Rat

Traumatic brain injury (TBI) has the potential to perturb perception by disrupting electrical propagation within and between the thalamus and cerebral cortex. Moderate and severe TBI may result in posttraumatic epilepsy, a condition characterized by convulsive tonic-clonic seizures. Spike/wave discharges (SWDs) of generalized nonconvulsive seizures, also called absence seizures, may also occur as a consequence of brain trauma. As mild hyperthermia has been reported to exacerbate histopathological and behavioral outcomes, we used an unbiased algorithm to detect periodic increases in power across different frequency bands following single or double closed head injury (CHI) under normothermia and hyperthermia conditions. We demonstrated that mild TBI did not significantly alter the occurrence of events containing increases in power between the delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta1 (12-20 Hz) frequency bands in the Sprague Dawley rat 12 weeks after injury. However, when hyperthermia (39°C) was induced before and after CHI, electrographic events containing a similar waveform and harmonic frequency to SWDs were observed in a subset of animals. Further experiments utilizing chronic recordings will need to be performed to determine if these trends lead to absence seizures.

Transient forebrain ischemia under hyperthermic condition accelerates memory impairment and neuronal death in the gerbil hippocampus by increasing NMDAR1 expression

Altered expression levels of N‑methyl‑D‑aspartate receptor (NMDAR), a ligand‑gated ion channel, have a harmful effect on cellular survival. Hyperthermia is a proven risk factor of transient forebrain ischemia (tFI) and can cause extensive and severe brain damage associated with mortality. The objective of the present study was to investigate whether hyperthermic preconditioning affected NMDAR1 immunoreactivity associated with deterioration of neuronal function in the gerbil hippocampal CA1 region following tFI via histological and western blot analyses. Hyperthermic preconditioning was performed for 1 h before tFI, which was developed by ligating common carotid arteries for 5 min. tFI‑induced cognitive impairment under hyperthermia was worse compared with that under normothermia. Loss (death) of pyramidal neurons in the CA1 region occurred fast and was more severe under hyperthermia compared with that under normothermia. NMDAR1 immunoreactivity was not observed in the somata of pyramidal neurons of sham gerbils with normothermia. However, its immunoreactivity was strong in the somata and processes at 12 h post‑tFI. Thereafter, NMDAR1 immunoreactivity decreased with time after tFI. On the other hand, NMDAR1 immunoreactivity under hyperthermia was significantly increased in the somata and processes at 6 h post‑tFI. The change pattern of NMDAR1 immunoreactivity under hyperthermia was different from that under normothermia. Overall, accelerated tFI‑induced neuronal death under hyperthermia may be closely associated with altered NMDAR1 expression compared with that under normothermia.

Early Life Stress Exacerbates Outcome after Traumatic Brain Injury

The neurocognitive impairments associated with mild traumatic brain injury (TBI) often resolve within 1-2 weeks; however, a subset of people exhibit persistent cognitive dysfunction for weeks to months after injury. The factors that contribute to these persistent deficits are unknown. One potential risk factor for worsened outcome after TBI is a history of stress experienced by a person early in life. Early life stress (ELS) includes maltreatment such as neglect, and interferes with the normal construction of cortical and hippocampal circuits. We hypothesized that a history of ELS contributes to persistent learning and memory dysfunction following a TBI. To explore this interaction, we modeled ELS by separating Sprague Dawley pups from their nursing mothers from post-natal days 2-14 for 3 h daily. At 2 months of age, male rats received sham surgery or mild to moderate parasagittal fluid-percussion brain injury. We found that the combination of ELS with TBI in adulthood impaired hippocampal-dependent learning, as assessed with contextual fear conditioning, the water maze task, and spatial working memory. Cortical atrophy was significantly exacerbated in TBI animals exposed to ELS compared with normal-reared TBI animals. Changes in corticosterone in response to restraint stress were prolonged in TBI animals that received ELS compared with TBI animals that were normally reared or sham animals that received ELS. Our findings indicate that ELS is a risk factor for worsened outcome after TBI, and results in persistent learning and memory deficits, worsened cortical pathology, and an exacerbation of the hormonal stress response.

Cerium Oxide Nanoparticles Improve Outcome after In Vitro and In Vivo Mild Traumatic Brain Injury

Mild traumatic brain injury results in aberrant free radical generation, which is associated with oxidative stress, secondary injury signaling cascades, mitochondrial dysfunction, and poor functional outcome. Pharmacological targeting of free radicals with antioxidants has been examined as an approach to treatment, but has met with limited success in clinical trials. Conventional antioxidants that are currently available scavenge a single free radical before they are destroyed in the process. Here, we report for the first time that a novel regenerative cerium oxide nanoparticle antioxidant reduces neuronal death and calcium dysregulation after in vitro trauma. Further, using an in vivo model of mild lateral fluid percussion brain injury in the rat, we report that cerium oxide nanoparticles also preserve endogenous antioxidant systems, decrease macromolecular free radical damage, and improve cognitive function. Taken together, our results demonstrate that cerium oxide nanoparticles are a novel nanopharmaceutical with potential for mitigating neuropathological effects of mild traumatic brain injury and modifying the course of recovery.

Mild Hyperthermia Aggravates Glucose Metabolic Consequences in Repetitive Concussion

Traumatic brain injury (TBI) is one of the leading causes of mortality and disability around the world. Mild TBI (mTBI) makes up approximately 80% of reported cases and often results in transient psychological abnormalities and cognitive disruption. At-risk populations for mTBI include athletes and other active individuals who may sustain repetitive concussive injury during periods of exercise and exertion when core temperatures are elevated. Previous studies have emphasized the impact that increased brain temperature has on adverse neurological outcomes. A lack of diagnostic tools to assess concussive mTBI limits the ability to effectively identify the post-concussive period during which the brain is uniquely susceptible to damage upon sustaining additional injury. Studies have suggested that a temporal window of increased vulnerability that exists corresponds to a period of injury-induced depression of cerebral glucose metabolism. In the current study, we sought to evaluate the relationship between repetitive concussion, local cerebral glucose metabolism, and brain temperature using the Marmarou weight drop model to generate mTBI. Animals were injured three consecutive times over a period of 7 days while exposed to either normothermic or hyperthermic temperatures for 15 min prior to and 1 h post each injury. A ¹⁴C-2-deoxy-d-glucose (2DG) autoradiography was used to measure local cerebral metabolic rate of glucose (lCMR_Glc) in 10 diverse brain regions across nine bregma levels 8 days after the initial insult. We found that repetitive mTBI significantly decreased glucose utilization bilaterally in several cortical areas, such as the cingulate, visual, motor, and retrosplenial cortices, as well as in subcortical areas, including the caudate putamen and striatum, compared to sham control animals. lCMR_Glc was significant in both normothermic and hyperthermic repetitive mTBI animals relative to the sham group, but to a greater degree when exposed to hyperthermic conditions. Taken together, we report significant injury-induced glucose hypometabolism after repetitive concussion in the brain, and additionally highlight the importance of temperature management in the acute period after brain injury.

Brain diseases in changing climate

Climate change is one of the biggest and most urgent challenges for the 21st century. Rising average temperatures and ocean levels, altered precipitation patterns and increased occurrence of extreme weather events affect not only the global landscape and ecosystem, but also human health. Multiple environmental factors influence the onset and severity of human diseases and changing climate may have a great impact on these factors. Climate shifts disrupt the quantity and quality of water, increase environmental pollution, change the distribution of pathogens and severely impacts food production - all of which are important regarding public health. This paper focuses on brain health and provides an overview of climate change impacts on risk factors specific to brain diseases and disorders. We also discuss emerging hazards in brain health due to mitigation and adaptation strategies in response to climate changes.

Neurobiological effect of selective brain cooling after concussive injury

The search for effective treatment facilitating recovery from concussive injury, as well as reducing risk for recurrent concussion is an ongoing challenge. This study aimed to determine: a) feasibility of selective brain cooling to facilitate clinical symptoms resolution, and b) biological functions of the brain within athletes in acute phase of sports-related concussion. Selective brain cooling for 30 minutes using WElkins sideline cooling system was administered to student-athletes suffering concussive injury (n=12; tested within 5±3 days) and those without history of concussion (n=12). fMRI and ASL sequences were obtained before and immediately after cooling to better understanding the mechanism by which cooling affects neurovascular coupling. Concussed subjects self-reported temporary relief from physical symptoms after cooling. There were no differences in the number or strength of functional connections within Default Mode Network (DMN) between groups prior to cooling. However, we observed a reduction in the strength and number of connections of the DMN with other ROIs in both groups after cooling. Unexpectedly, we observed a significant increase in cerebral blood flow (CBF) assessed by ASL after selective cooling in the concussed subjects compared to the normal controls. We suggest that compromised neurovascular coupling in acute phase of injury may be temporarily restored by cooling to match CBF with surges in the metabolic demands of the brain. Upon further validation, selective brain cooling could be a potential clinical tool in the minimization of symptoms and pathological changes after concussion.

Immediate Removal From Activity After Sport-Related Concussion Is Associated With Shorter Clinical Recovery and Less Severe Symptoms in Collegiate Student-Athletes

BACKGROUND

Timely removal from activity after concussion symptoms remains problematic despite heightened awareness. Previous studies indicated potential adverse effects of continuing to participate in physical activity immediately after sustaining a concussion. Hypothesis/Purpose: The purpose was to determine the effect of timing of removal from play after concussion on clinical outcomes. It was hypothesized that immediate removal from activity after sport-related concussion (SRC) would be associated with less time missed from sport, a shorter symptomatic period, and better outcomes on acute clinical measures.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Data were reported from the National Collegiate Athletic Association and Department of Defense Grand Alliance: Concussion Awareness, Research, and Education (CARE) Consortium. Participants with 506 diagnosed SRCs from 18 sports and 25 institutions and military service academies were analyzed and classified as either immediate removal from activity (I-RFA) or delayed removal from activity (D-RFA). Outcomes of interest included time missed from sport attributed to their SRC, symptom duration, and clinical assessment scores.

RESULTS

There were 322 participants (63.6%) characterized as D-RFA. I-RFA status was associated with significantly less time missed from sport ( R² change = .022-.024, P < .001 to P = .001) and shorter symptom duration ( R² change = .044-.046, P < .001 [all imputations]) while controlling for other SRC recovery modifiers. These athletes missed approximately 3 fewer days from sport participation. I-RFA athletes had significantly less severe acute SRC symptoms and were at lower risk of recovery taking ≥14 days (relative risk = .614, P < .001, small-medium effect size) and ≥21 days (relative risk = .534, P = .010, small effect size).

CONCLUSION

I-RFA is a protective factor associated with less severe acute symptoms and shorter recovery after SRC. Conveying this message to athletes, coaches, and others involved in the care of athletes may promote timely injury reporting.

Hyperthermia and Mild Traumatic Brain Injury: Effects on Inflammation and the Cerebral Vasculature

Mild traumatic brain injury (mTBI) or concussion represents the majority of brain trauma in the United States. The pathophysiology of mTBI is complex and may include both focal and diffuse injury patterns. In addition to altered circuit dysfunction and traumatic axonal injury (TAI), chronic neuroinflammation has also been implicated in the pathophysiology of mTBI. Recently, our laboratory has reported the detrimental effects of mild hyperthermic mTBI in terms of worsening histopathological and behavioral outcomes. To clarify the role of temperature-sensitive neuroinflammatory processes on these consequences, we evaluated the effects of elevated brain temperature (39°C) on altered microglia/macrophage phenotype patterns after mTBI, changes in leukocyte recruitment, and TAI. Sprague-Dawley male rats underwent mild parasagittal fluid-percussion injury under normothermic (37°C) or hyperthermic (39°C) conditions. Cortical and hippocampal regions were analyzed using several cellular and molecular outcome measures. At 24 h, the ratio of iNOS-positive (M1 type phenotype) to arginase-positive (M2 type phenotype) cells after hyperthermic mTBI showed an increase compared with normothermia by flow cytometry. Inflammatory response gene arrays also demonstrated a significant increase in several classes of pro-inflammatory genes with hyperthermia treatment over normothermia. The injury-induced expression of chemokine ligand 2 (Ccl2) and alpha-2-macroglobulin were also increased with hyperthermic mTBI. With western blot analysis, an increase in CD18 and intercellular cell adhesion molecule-1 (ICAM-1) with hyperthermia and a significant increase in Iba1 reactive microglia are reported in the cerebral cortex. Together, these results demonstrate significant differences in the cellular and molecular consequences of raised brain temperature at the time of mTBI. The observed polarization toward a M1-phenotype with mild hyperthermia would be expected to augment chronic inflammatory cascades, sustained functional deficits, and increased vulnerability to secondary insults. Mild elevations in brain temperature may contribute to the more severe and longer lasting consequences of mTBI or concussion reported in some patients.

Therapeutic hypothermia and targeted temperature management for traumatic brain injury: Experimental and clinical experience

Traumatic brain injury (TBI) is a worldwide medical problem, and currently, there are few therapeutic interventions that can protect the brain and improve functional outcomes in patients. Over the last several decades, experimental studies have investigated the pathophysiology of TBI and tested various pharmacological treatment interventions targeting specific mechanisms of secondary damage. Although many preclinical treatment studies have been encouraging, there remains a lack of successful translation to the clinic and no therapeutic treatments have shown benefit in phase 3 multicenter trials. Therapeutic hypothermia and targeted temperature management protocols over the last several decades have demonstrated successful reduction of secondary injury mechanisms and, in some selective cases, improved outcomes in specific TBI patient populations. However, the benefits of therapeutic hypothermia have not been demonstrated in multicenter randomized trials to significantly improve neurological outcomes. Although the exact reasons underlying the inability to translate therapeutic hypothermia into a larger clinical population are unknown, this failure may reflect the suboptimal use of this potentially powerful therapeutic in potentially treatable severe trauma patients. It is known that multiple factors including patient recruitment, clinical treatment variables, and cooling methodologies are all important in yielding beneficial effects. High-quality multicenter randomized controlled trials that incorporate these factors are required to maximize the benefits of this experimental therapy. This article therefore summarizes several factors that are important in enhancing the beneficial effects of therapeutic hypothermia in TBI. The current failures of hypothermic TBI clinical trials in terms of clinical protocol design, patient section, and other considerations are discussed and future directions are emphasized.

Is temperature an important variable in recovery after mild traumatic brain injury?

With nearly 42 million mild traumatic brain injuries (mTBIs) occurring worldwide every year, understanding the factors that may adversely influence recovery after mTBI is important for developing guidelines in mTBI management. Extensive clinical evidence exists documenting the detrimental effects of elevated temperature levels on recovery after moderate to severe TBI. However, whether elevated temperature alters recovery after mTBI or concussion is an active area of investigation. Individuals engaged in exercise and competitive sports regularly experience body and brain temperature increases to hyperthermic levels and these temperature increases are prolonged in hot and humid ambient environments. Thus, there is a strong potential for hyperthermia to alter recovery after mTBI in a subset of individuals at risk for mTBI. Preclinical mTBI studies have found that elevating brain temperature to 39°C before mTBI significantly increases neuronal death within the cortex and hippocampus and also worsens cognitive deficits. This review summarizes the pathology and behavioral problems of mTBI that are exacerbated by hyperthermia and discusses whether hyperthermia is a variable that should be considered after concussion and mTBI. Finally, underlying pathophysiological mechanisms responsible for hyperthermia-induced altered responses to mTBI and potential gender considerations are discussed.

Frontal Traumatic Brain Injury Increases Impulsive Decision Making in Rats: A Potential Role for the Inflammatory Cytokine Interleukin-12

Traumatic brain injury (TBI) is associated with the development of numerous psychiatric diseases. Of particular concern for TBI patients is the impact of chronic impulsivity on daily functioning. Despite the scope of the human problem, little has been done to address impulsivity in animal models of brain injury. In the current study, we examined the effects of either a severe or a milder bilateral frontal controlled cortical impact injury on impulsivity using the Delay Discounting Task (DDT), in which preference for smaller-sooner over larger-later rewards is indicative of greater impulsive choice. Both milder and severe TBI caused a significant, chronic increase in impulsive decision making. Despite these pronounced changes in performance of the DDT, memory function, as assessed by the Morris Water Maze, was not impaired in more mildly injured rats and only transiently impacted in the severe TBI group. Whereas a significant lesion was only evident in severely injured rats, analysis of cytokine levels within the frontal cortex revealed a selective increase in interleukin (IL)-12 that was associated with the magnitude of the change in impulsive choice caused by both milder and severe TBI. These findings suggest that tissue loss alone cannot explain the increased impulsivity observed, and that inflammatory pathways mediated by IL-12 may be a contributing factor. The findings from this study highlight the sensitivity of sophisticated behavioral measures designed to assess neuropsychiatric dysfunction in the detection of TBI-induced cognitive impairments and their utility in identifying potential mechanistic pathways and therapeutic targets.

[Recommendation on temperature management after cardiopulmonary arrest and severe traumatic brain injury in childhood beyond the neonatal period : Statement of the German Society for Neonatology and Pediatric Intensive Care Medicine (GNPI) and the scientific Working Group for Paediatric Anaesthesia (WAKKA) of the German Society of Anaesthesiology and Intensive Care (DGAI)]

The available data on the effectiveness of therapeutic hypothermia in different patient groups are heterogeneous. Although the benefits have been proven for some collectives, recommendations for the use of hypothermia treatment in other groups are based on less robust data and conclusions by analogy. This article gives a review of the current evidence of temperature management in all age groups and based on this state of knowledge, recommends active temperature management with the primary aim of strict normothermia (36-36.5 °C) for 72 hours after cardiopulmonary arrest or severe traumatic brain injury for children beyond the neonatal period.

The far-reaching scope of neuroinflammation after traumatic brain injury

The 'silent epidemic' of traumatic brain injury (TBI) has been placed in the spotlight as a result of clinical investigations and popular press coverage of athletes and veterans with single or repetitive head injuries. Neuroinflammation can cause acute secondary injury after TBI, and has been linked to chronic neurodegenerative diseases; however, anti-inflammatory agents have failed to improve TBI outcomes in clinical trials. In this Review, we therefore propose a new framework of targeted immunomodulation after TBI for future exploration. Our framework incorporates factors such as the time from injury, mechanism of injury, and secondary insults in considering potential treatment options. Structuring our discussion around the dynamics of the immune response to TBI - from initial triggers to chronic neuroinflammation - we consider the ability of soluble and cellular inflammatory mediators to promote repair and regeneration versus secondary injury and neurodegeneration. We summarize both animal model and human studies, with clinical data explicitly defined throughout this Review. Recent advances in neuroimmunology and TBI-responsive neuroinflammation are incorporated, including concepts of inflammasomes, mechanisms of microglial polarization, and glymphatic clearance. Moreover, we highlight findings that could offer novel therapeutic targets for translational and clinical research, assimilate evidence from other brain injury models, and identify outstanding questions in the field.

Traumatic brain injuries

Traumatic brain injuries (TBIs) are clinically grouped by severity: mild, moderate and severe. Mild TBI (the least severe form) is synonymous with concussion and is typically caused by blunt non-penetrating head trauma. The trauma causes stretching and tearing of axons, which leads to diffuse axonal injury - the best-studied pathogenetic mechanism of this disorder. However, mild TBI is defined on clinical grounds and no well-validated imaging or fluid biomarkers to determine the presence of neuronal damage in patients with mild TBI is available. Most patients with mild TBI will recover quickly, but others report persistent symptoms, called post-concussive syndrome, the underlying pathophysiology of which is largely unknown. Repeated concussive and subconcussive head injuries have been linked to the neurodegenerative condition chronic traumatic encephalopathy (CTE), which has been reported post-mortem in contact sports athletes and soldiers exposed to blasts. Insights from severe injuries and CTE plausibly shed light on the underlying cellular and molecular processes involved in mild TBI. MRI techniques and blood tests for axonal proteins to identify and grade axonal injury, in addition to PET for tau pathology, show promise as tools to explore CTE pathophysiology in longitudinal clinical studies, and might be developed into diagnostic tools for CTE. Given that CTE is attributed to repeated head trauma, prevention might be possible through rule changes by sports organizations and legislators.

Effect of Mild Traumatic Brain Injury and Demographic Factors on Psychological Outcome

Background

It is well-known that severe brain injury can make people susceptible to psychological symptoms. However, mild traumatic brain injury (MTBI) is still open for discussion.

Objectives

This study aimed to compare psychological symptoms of MTBI patients with those without MTBI considering demographic auxiliary variables.

Patients and Methods

This prospective cohort study was conducted on 50 MTBI patients and 50 healthy subjects aged 15 - 65 years. Psychological assessment was carried out six months post-injury using a series of self-report measures including the brief symptom inventory (BSI) scale. Other information of the individuals in the two groups was recorded prospectively. Data were analyzed using the chi-square test, t-test, and multiple linear regression tests.

Results

There was a significant difference between the MTBI patients and healthy subjects in all subscales and total score of BSI. Our findings showed that obsession-compulsion and anxiety subscales were significantly more common in the MTBI patients than in the healthy subjects. Also, multivariate regression analysis six months post- injury showed that head trauma and substance abuse can have an effect on psychological symptoms.

Conclusions

Mild traumatic brain injuries despite of the normal CT scan and history of substance abuse are closely related to psychological symptoms. Therefore, it is recommended that patients with brain trauma 6 months post-injury and subjects with a history of substance abuse be evaluated for psychological distress to support better rehabilitation.

Traumatic Brain Injury Upregulates Phosphodiesterase Expression in the Hippocampus

Traumatic brain injury (TBI) results in significant impairments in hippocampal synaptic plasticity. A molecule critically involved in hippocampal synaptic plasticity, 3′,5′-cyclic adenosine monophosphate, is downregulated in the hippocampus after TBI, but the mechanism that underlies this decrease is unknown. To address this question, we determined whether phosphodiesterase (PDE) expression in the hippocampus is altered by TBI. Young adult male Sprague Dawley rats received sham surgery or moderate parasagittal fluid-percussion brain injury. Animals were analyzed by western blotting for changes in PDE expression levels in the hippocampus. We found that PDE1A levels were significantly increased at 30 min, 1 h and 6 h after TBI. PDE4B2 and 4D2 were also significantly increased at 1, 6, and 24 h after TBI. Additionally, phosphorylation of PDE4A was significantly increased at 6 and 24 h after TBI. No significant changes were observed in levels of PDE1B, 1C, 3A, 8A, or 8B between 30 min to 7 days after TBI. To determine the spatial profile of these increases, we used immunohistochemistry and flow cytometry at 24 h after TBI. PDE1A and phospho-PDE4A localized to neuronal cell bodies. PDE4B2 was expressed in neuronal dendrites, microglia and infiltrating CD11b⁺ immune cells. PDE4D was predominantly found in microglia and infiltrating CD11b⁺ immune cells. To determine if inhibition of PDE4 would improve hippocampal synaptic plasticity deficits after TBI, we treated hippocampal slices with rolipram, a pan-PDE4 inhibitor. Rolipram partially rescued the depression in basal synaptic transmission and converted a decaying form of long-term potentiation (LTP) into long-lasting LTP. Overall, these results identify several possible PDE targets for reducing hippocampal synaptic plasticity deficits and improving cognitive function acutely after TBI.

Therapeutic hypothermia and targeted temperature management in traumatic brain injury: Clinical challenges for successful translation

The use of therapeutic hypothermia (TH) and targeted temperature management (TTM) for severe traumatic brain injury (TBI) has been tested in a variety of preclinical and clinical situations. Early preclinical studies showed that mild reductions in brain temperature after moderate to severe TBI improved histopathological outcomes and reduced neurological deficits. Investigative studies have also reported that reductions in post-traumatic temperature attenuated multiple secondary injury mechanisms including excitotoxicity, free radical generation, apoptotic cell death, and inflammation. In addition, while elevations in post-traumatic temperature heightened secondary injury mechanisms, the successful implementation of TTM strategies in injured patients to reduce fever burden appear to be beneficial. While TH has been successfully tested in a number of single institutional clinical TBI studies, larger randomized multicenter trials have failed to demonstrate the benefits of therapeutic hypothermia. The use of TH and TTM for treating TBI continues to evolve and a number of factors including patient selection and the timing of the TH appear to be critical in successful trial design. Based on available data, it is apparent that TH and TTM strategies for treating severely injured patients is an important therapeutic consideration that requires more basic and clinical research. Current research involves the evaluation of alternative cooling strategies including pharmacologically-induced hypothermia and the combination of TH or TTM approaches with more selective neuroprotective or reparative treatments. This manuscript summarizes the preclinical and clinical literature emphasizing the importance of brain temperature in modifying secondary injury mechanisms and in improving traumatic outcomes in severely injured patients. This article is part of a Special Issue entitled SI:Brain injury and recovery.

The effect of selective head-neck cooling on physiological and cognitive functions in healthy volunteers

In general, brain temperatures are elevated during physical sporting activities; therefore, reducing brain temperature shortly after a sports-related concussion (SRC) could be a promising intervention technique. The main objective of this study was to examine the effects of head and neck cooling on physiological and cognitive function in normal healthy volunteers. Twelve healthy volunteers underwent two different sessions of combined head and neck cooling, one session with a cold pack and one session with a room temperature pack. Physiological measurements included: systolic/diastolic blood pressure, pulse oximetry, heart rate, and sublingual and tympanic temperature. Cognitive assessment included: processing speed, executive function, and working memory tasks. Physiological measurements were taken pre-, mid- and post-cooling, while cognitive assessments were done before and after cooling. The order of the sessions was randomized. There was a significant decrease in tympanic temperature across both sessions; however more cooling occurred when the cold pack was in the device. There was no significant decrease in sublingual temperature across either session. The observed heart rates, pulse oximetry, systolic and diastolic blood pressure during the sessions were all within range of a normal healthy adult. Cognitive assessment remained stable across each session for both pre- and post-cooling. We propose that optimizing brain temperature management after brain injury using head and neck cooling technology may represent a sensible, practical, and effective strategy to potentially enhance recovery and perhaps minimize the subsequent short and long term consequences from SRC.