Traumatic brain injury: age at injury influences dementia risk after TBI

Rehabilitation of Older Asian Traumatic Brain Injury Inpatients: A Retrospective Study Comparing Functional Independence between Age Groups

Across traumatic brain injury (TBI) severities, a geriatric TBI tsunami has emerged. Mixed outcomes are reported for elderly TBI with positive functional improvements with acute inpatient rehabilitation. We studied the effect of age at TBI on discharge functional outcomes, levels of independence and length of stay. A retrospective analysis of Asian TBI patients during inpatient rehabilitation over a 4-year period was conducted. Independent variables included admission GCS, post-traumatic amnesia (PTA) duration and injury subtypes. Primary outcomes were discharge Functional Independence Measure (Td-FIM) and FIM gain. In total, 203 datasets were analysed; 60.1% (122) were aged ≥65 years (older), while 39.9% (81) were <65 years (younger). At discharge, older TBI had a significantly lower Td-FIM by 15 points compared to younger (older 90/126 vs. younger 105/126, p < 0.001). Median FIM gains (younger 27 vs. older 23, p = 0.83) and rehabilitation LOS (older 29.5 days vs. younger 27.5 days, p = 0.79) were similar for both age groups. Older TBIs had significantly lower independence (Td-FIM category ≥ 91) levels (49.4% older vs. 63.9% younger, p = 0.04), higher institutionalisation rates (23.5% older vs. 10.7% younger, p = 0.014) and need for carers (81.5% older vs. 66.4% younger, p = 0.019) on discharge. Although 77% of older TBI patients returned home, a significantly higher proportion needed care. This study supports the functional benefits of TBI rehabilitation in increasing independence regardless of age without incurring longer inpatient rehabilitation days.

Lissencephaly-1 mutations enhance traumatic brain injury outcomes in Drosophila

Traumatic brain injury (TBI) outcomes vary greatly among individuals, but most of the variation remains unexplained. Using a Drosophila melanogaster TBI model and 178 genetically diverse lines from the Drosophila Genetic Reference Panel (DGRP), we investigated the role that genetic variation plays in determining TBI outcomes. Following injury at 20-27 days old, DGRP lines varied considerably in mortality within 24 h ("early mortality"). Additionally, the disparity in early mortality resulting from injury at 20-27 vs 0-7 days old differed among DGRP lines. These data support a polygenic basis for differences in TBI outcomes, where some gene variants elicit their effects by acting on aging-related processes. Our genome-wide association study of DGRP lines identified associations between single nucleotide polymorphisms in Lissencephaly-1 (Lis-1) and Patronin and early mortality following injury at 20-27 days old. Lis-1 regulates dynein, a microtubule motor required for retrograde transport of many cargoes, and Patronin protects microtubule minus ends against depolymerization. While Patronin mutants did not affect early mortality, Lis-1 compound heterozygotes (Lis-1x/Lis-1y) had increased early mortality following injury at 20-27 or 0-7 days old compared with Lis-1 heterozygotes (Lis-1x/+), and flies that survived 24 h after injury had increased neurodegeneration but an unaltered lifespan, indicating that Lis-1 affects TBI outcomes independently of effects on aging. These data suggest that Lis-1 activity is required in the brain to ameliorate TBI outcomes through effects on axonal transport, microtubule stability, and other microtubule proteins, such as tau, implicated in chronic traumatic encephalopathy, a TBI-associated neurodegenerative disease in humans.

Tau pathology, metal dyshomeostasis and repetitive mild traumatic brain injury: an unexplored link paving the way for neurodegeneration

Repetitive mild traumatic brain injury (r-mTBI), commonly experienced by athletes and military personnel, causes changes in multiple intracellular pathways, one of which involves the tau protein. Tau phosphorylation plays a role in several neurodegenerative conditions including chronic traumatic encephalopathy (CTE), a progressive neurodegenerative disorder linked to repeated head trauma. There is now mounting evidence suggesting that tau phosphorylation may be regulated by metal ions (such as iron, zinc and copper), which themselves are implicated in ageing and neurodegenerative disorders such as Alzheimer's disease (AD). Recent work has also shown that a single TBI can result in age-dependent and region-specific modulation of metal ions. As such, this review explores the link between TBI, CTE, ageing and neurodegeneration with a specific focus on the involvement of (and interaction between) tau pathology and metal dyshomeostasis. The authors highlight that metal dyshomeostasis has yet to be investigated in the context of repeat head trauma or CTE. Given the evidence that metal dyshomeostasis contributes to the onset and/or progression of neurodegeneration, and that CTE itself is a neurodegenerative condition, this brings to light an uncharted link that should be explored. The development of adequate models of r-mTBI and/or CTE will be crucial in deepening our understanding of the pathological mechanisms that drive the clinical manifestations in these conditions and also in the development of effective therapeutics targeted towards slowing progressive neurodegenerative disorders.

Self-Reported Complaints as Prognostic Markers for Outcome After Mild Traumatic Brain Injury in Elderly: A Machine Learning Approach

Self-reported complaints are common after mild traumatic brain injury (mTBI). Particularly in the elderly with mTBI, the pre-injury status might play a relevant role in the recovery process. In most mTBI studies, however, pre-injury complaints are neither analyzed nor are the elderly included. Here, we aimed to identify which individual pre- and post-injury complaints are potential prognostic markers for incomplete recovery (IR) in elderly patients who sustained an mTBI. Since patients report many complaints across several domains that are strongly related, we used an interpretable machine learning (ML) approach to robustly deal with correlated predictors and boost classification performance. Pre- and post-injury levels of 20 individual complaints, as self-reported in the acute phase, were analyzed. We used data from two independent studies separately: UPFRONT study was used for training and validation and ReCONNECT study for independent testing. Functional outcome was assessed with the Glasgow Outcome Scale Extended (GOSE). We dichotomized functional outcome into complete recovery (CR; GOSE = 8) and IR (GOSE ≤ 7). In total 148 elderly with mTBI (median age: 67 years, interquartile range [IQR]: 9 years; UPFRONT: N = 115; ReCONNECT: N = 33) were included in this study. IR was observed in 74 (50%) patients. The classification model (IR vs. CR) achieved a good performance (the area under the receiver operating characteristic curve [ROC-AUC] = 0.80; 95% CI: 0.74-0.86) based on a subset of only 8 out of 40 pre- and post-injury complaints. We identified increased neck pain (p = 0.001) from pre- to post-injury as the strongest predictor of IR, followed by increased irritability (p = 0.011) and increased forgetfulness (p = 0.035) from pre- to post-injury. Our findings indicate that a subset of pre- and post-injury physical, emotional, and cognitive complaints has predictive value for determining long-term functional outcomes in elderly patients with mTBI. Particularly, post-injury neck pain, irritability, and forgetfulness scores were associated with IR and should be assessed early. The application of an ML approach holds promise for application in self-reported questionnaires to predict outcomes after mTBI.

An oligomeric semiconducting nanozyme with ultrafast electron transfers alleviates acute brain injury

Artificial enzymes have attracted wide interest in disease diagnosis and biotechnology due to high stability, easy synthesis, and cost effectiveness. Unfortunately, their catalytic rate is limited to surface electron transfer, affecting the catalytic and biological activity. Here, we report an oligomeric nanozyme (O-NZ) with ultrafast electron transfer, achieving ultrahigh catalytic activity. O-NZ shows electron transfer of 1.8 nanoseconds in internal cores and 1.2 picoseconds between core and ligand molecule, leading to ultrahigh superoxidase dismutase–like and glutathione peroxidase–like activity (comparable with natural enzyme, Michaelis constant = 0.87 millimolars). Excitingly, O-NZ can improve the 1-month survival rate of mice with acute brain trauma from 50 to 90% and promote the recovery of long-term neurocognition. Biochemical experiments show that O-NZ can decrease harmful peroxide and superoxide via in vivo catalytic chain reaction and reduce acute neuroinflammation via nuclear factor erythroid-2 related factor 2–mediated up-regulation of heme oxygenase-1 expression.

The Impact of Age and Severity on Dementia After Traumatic Brain Injury: A Comparison Study

BACKGROUND

Growing evidence associates traumatic brain injury (TBI) with increased risk of dementia, but few studies have evaluated associations in patients younger than 55 yr using non-TBI orthopedic trauma (NTOT) patients as controls to investigate the influence of age and TBI severity, and to identify predictors of dementia after trauma.

OBJECTIVE

To investigate the relationship between TBI and dementia in an institutional group.

METHODS

Retrospective cohort study (2000-2018) of TBI patients aged 45 to 100 yr vs NTOT controls. Primary outcome was dementia after TBI (followed ≤10 yr). Cox proportional hazards models were used to assess risk of dementia; logistic regression models assessed predictors of dementia.

RESULTS

Among 24 846 patients, TBI patients developed dementia (7.5% vs 4.6%) at a younger age (78.6 vs 82.7 yr) and demonstrated higher 10-yr mortality than controls (27% vs 14%; P < .001). Mild TBI patients had higher incidence of dementia (9%) than moderate/severe TBI (5.4%), with lower 10-yr mortality (20% vs 31%; P < .001). Risk of dementia was significant in all mild TBI age groups, even 45 to 54 yr (hazard ratio 4.1, 95% CI 2.7-7.8). A total of 10-yr cumulative incidence was higher in mild TBI (14.4%) than moderate/severe TBI (11.3%) and controls (6.8%) (P < .001). Predictors of dementia include TBI, sex, age, hypertension, hyperlipidemia, stroke, depression, anxiety, and Injury Severity Score.

CONCLUSION

Mild and moderate/severe TBI patients experienced higher incidence of dementia, even in the youngest group (45-54 yr old), than NTOT controls. All TBI patients, especially middle-aged adults with minor injury who are more likely to be overlooked, should be monitored for dementia.

Severe traumatic brain injury (TBI) - a seven-year comparative study in a Department of Forensic Medicine

Deaths caused by traumatic brain injury (TBI) increase in incidence every year worldwidely, mainly in developing countries. Thus, World Health Organization (WHO) estimates that in 2020, TBI will become the third main cause of death. In our study, we evaluated the deaths caused by TBI recorded within the Institute of Forensic Medicine of Craiova, Romania, between 2011 and 2017. Therefore, according to age, the cases were divided into two groups: people aged 0-18 years old (including 18 years old) and people aged over 18 years old (a total of 1005 cases, of which 971 were adults and 34 included in the age group 0-18 years old). In both groups, most patients were males from the rural area. In adults, falling was the main legal entity of the cases, followed by car accidents (which were the most common in children). In both groups, in car accidents, most of them were pedestrians and car occupants. Various aggressions (human, animal, self-injury) were found in 94 (9.68%) of the adult cases and in four (11.76%) cases of children. Another parameter under study was the blood alcohol concentration, being observed that most of the subjects with positive blood alcohol content died from car accidents. By evaluating the Glasgow Coma Scale (GCS) score as a prognostic factor, most of the subjects presented third and fourth degree coma at admission; still, 5.14% of the adult patients who deceased had GCS score 15 at admission, death occurring probably by developing some intracranial hematomas in time. Regarding the morphology of the lesions, most patients presented various forms of cranial fractures, 185 (19.05%) adults in association with extradural hemorrhages∕hematomas, but also there were four cases with extradural hematomas without any cranial fractures. In children, there was highlighted a single case of extradural hemorrhage under the fracture line. Seventy-eight percent of the adults and 44.12% of children presented subdural hematomas associated with other meningo-cerebral lesions. Also, 83.63% of the adults and 97% of children presented brain contusions. In both groups, brain laceration was observed in approximately 50% of the cases.

Blast-Related Traumatic Brain Injury: Current Concepts and Research Considerations

Traumatic brain injury (TBI) is a well-known consequence of participation in activities such as military combat or collision sports. But the wide variability in eliciting circumstances and injury severities makes the study of TBI as a uniform disease state impossible. Military Service members are under additional, unique threats such as exposure to explosive blast and its unique effects on the body. This review is aimed toward TBI researchers, as it covers important concepts and considerations for studying blast-induced head trauma. These include the comparability of blast-induced head trauma to other mechanisms of TBI, whether blast overpressure induces measureable biomarkers, and whether a biodosimeter can link blast exposure to health outcomes, using acute radiation exposure as a corollary. This examination is contextualized by the understanding of concussive events and their psychological effects throughout the past century's wars, as well as the variables that predict sustaining a TBI and those that precipitate or exacerbate psychological conditions. Disclaimer: The views expressed in this article are solely the views of the authors and not those of the Department of Defense Blast Injury Research Coordinating Office, US Army Medical Research and Development Command, US Army Futures Command, US Army, or the Department of Defense.

Changing Demographic Profiles of Patients With Traumatic Brain Injury: An Aging Concern

Background: Trauma continues to be a common cause of mortality in Singapore. By understanding the epidemiology of Traumatic Brain Injury (TBI), healthcare professionals can be better equipped to tackle the increasing socioeconomic burden of disease, adopting better strategies in healthcare planning. Methodology: A retrospective review of 367 patients admitted with TBI to a tertiary medical institution from January to December 2014 was performed, studying demographic profiles, injury details and outcomes of these patients. Data was retrieved from the National Trauma Registry and the institution's database. Results: Two hundred thirty-four of the 367 patients included in this study fell into two age groups--19 to 40 years and ≥65 years. 58% of the TBI population were aged >60. Predominant mechanism of injuries in these groups were road traffic accidents and unwitnessed falls respectively. 39% of the Elderly group were on antiplatelet/anticoagulant agents (p < 0.001). While aggressive surgical intervention was more common in younger patients (p < 0.001), the elderly group had significantly longer lengths of hospital stay (p < 0.001). Though Glasgow Outcome Scale (GOS) scores at discharge were not significantly different between the two groups, elderly patients showed greater percentages of post-injury improvement subsequently. Conclusion: The demographics of TBI patients appears to have shifted toward an older population as compared to a decade ago, with an increased incidence of falls, highlighting a huge healthcare concern. We hope that this study will drive further nationwide studies in future, looking at the incidence and prevalence of TBI, and with the focus on tackling preventable causes of TBI.

Trehalose elevates brain zinc levels following controlled cortical impact in a mouse model of traumatic brain injury

Zinc (Zn) deficiency is a clinical consequence of brain injury that can result in neuropathological outcomes that are exacerbated with age. Here, we present laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging data showing modulation of brain Zn levels by the disaccharide trehalose in aged mice following a controlled cortical impact model of traumatic brain injury. In this proof-of-concept study, trehalose induced an increase in brain zinc levels, providing important preliminary data for larger studies using this simple carbohydrate as a modulator of this essential micronutrient in traumatic brain injury. Our results may have further implications for the treatment of a variety of neurodegenerative diseases and other disorders of the nervous system.

Impact of age on acute post-TBI neuropathology in mice expressing humanized tau: a Chronic Effects of Neurotrauma Consortium Study

OBJECTIVES

We hypothesized that polypathology is more severe in older than younger mice during the acute phase following repetitive mild traumatic brain injury (r-mTBI).

METHODS

Young and aged male and female mice transgenic for human tau (hTau) were exposed to r-mTBI or a sham procedure. Twenty-four hours post-last injury, mouse brain tissue was immunostained for alterations in astrogliosis, microgliosis, tau pathology, and axonal injury.

RESULTS

Quantitative analysis revealed a greater percent distribution of glial fibrillary acid protein and Iba-1 reactivity in the brains of all mice exposed to r-mTBI compared to sham controls. With respect to axonal injury, the number of amyloid precursor protein-positive profiles was increased in young vs aged mice post r-mTBI. An increase in tau immunoreactivity was found in young and aged injured male hTau mice.

CONCLUSIONS

We report the first evidence in our model that r-mTBI precipitates a complex sequelae of events in aged vs young hTau mice at an acute time point, typified by an increase in phosphorylated tau and astroglisosis, and a diminished microgliosis response and axonal injury in aged mice. These findings suggest differential age-dependent effects in TBI pathobiology.

Contribution of Fibrinogen to Inflammation and Neuronal Density in Human Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability, particularly among the young. Despite this, no disease-specific treatments exist. Recently, blood-brain barrier disruption and parenchymal fibrinogen deposition have been reported in acute traumatic brain injury and in long-term survival; however, their contribution to the neuropathology of TBI remains unknown. The presence of fibrinogen-a well-documented activator of microglia/macrophages-may be associated with neuroinflammation, and neuronal/axonal injury. To test this hypothesis, cases of human TBI with survival times ranging from 12 h to 13 years (survival <2 months, n = 15; survival >1 year, n = 6) were compared with uninjured controls (n = 15). Tissue was selected from the frontal lobe, temporal lobe, corpus callosum, cingulate gyrus, and brainstem, and the extent of plasma protein (fibrinogen and immunoglobulin G [IgG]) deposition, microglial/macrophage activation (CD68 and ionized calcium-binding adapter molecule 1 [Iba-1] immunoreactivity), neuronal density, and axonal transport impairment (β-amyloid precursor protein [βAPP] immunoreactivity) were assessed. Quantitative analysis revealed a significant increase in parenchymal fibrinogen and IgG deposition following acute TBI compared with long-term survival and control. Fibrinogen, but not IgG, was associated with microglial/macrophage activation and a significant reduction in neuronal density. Perivascular fibrinogen deposition also was associated with microglial/macrophage clustering and accrual of βAPP in axonal spheroids, albeit rarely. These findings mandate the future exploration of causal relationships between fibrinogen deposition, microglia/macrophage activation, and potential neuronal loss in acute TBI.

Age at injury is associated with the long-term cognitive outcome of traumatic brain injuries

INTRODUCTION

The association between age at injury (AAI) and long-term cognitive outcome of traumatic brain injuries (TBI) is debatable.

METHODS

Eligible participants with a history of TBI from Alzheimer's Disease Neuroimaging Initiative were divided into a childhood TBI (cTBI) group (the AAI ≤ 21 years old) and an adult TBI (aTBI) group (the AAI > 21 years old).

RESULTS

The cTBI group has a higher Everyday Cognition total score than the aTBI group. All perceived cognitive functions are worse for the cTBI group than for the aTBI group except memory. By contrast, the cTBI group has higher assessment scores on either the Boston Naming Test or Rey Auditory Verbal Learning Test than the aTBI group.

DISCUSSION

The AAI is associated with the long-term cognitive outcomes in older adults with a history of TBI.

Neuroimaging of deployment-associated traumatic brain injury (TBI) with a focus on mild TBI (mTBI) since 2009

OBJECTIVES

A substantial body of recent research has aimed to better understand the clinical sequelae of military trauma through the application of advanced brain imaging procedures in Veteran populations. The primary objective of this review was to highlight a portion of these recent studies to demonstrate how imaging tools can be used to understand military-associated brain injury.

METHODS

We focus here on the phenomenon of mild traumatic brain injury (mTBI) given its high prevalence in the Veteran population and current recognition of the need to better understand the clinical implications of this trauma. This is intended to provide readers with an initial exposure to the field of neuroimaging of mTBI with a brief introduction to the concept of traumatic brain injury, followed by a summary of the major imaging techniques that have been applied to the study of mTBI.

RESULTS

Taken together, the collection of studies reviewed demonstrates a clear role for neuroimaging towards understanding the various neural consequences of mTBI as well as the clinical complications of such brain changes.

CONCLUSIONS

This information must be considered in the larger context of research into mTBI, including the potentially unique nature of blast exposure and the long-term consequences of mTBI.

Pharmacological targeting of the PDGF-CC signaling pathway for blood-brain barrier restoration in neurological disorders

Neurological disorders account for a majority of non-malignant disability in humans and are often associated with dysfunction of the blood-brain barrier (BBB). Recent evidence shows that despite apparent variation in the origin of neural damage, the central nervous system has a common injury response mechanism involving platelet-derived growth factor (PDGF)-CC activation in the neurovascular unit and subsequent dysfunction of BBB integrity. Inhibition of PDGF-CC signaling with imatinib in mice has been shown to prevent BBB dysfunction and have neuroprotective effects in acute damage conditions, including traumatic brain injury, seizures or stroke, as well as in neurodegenerative diseases that develop over time, including multiple sclerosis and amyotrophic lateral sclerosis. Stroke and traumatic injuries are major risk factors for age-associated neurodegenerative disorders and we speculate that restoring BBB properties through PDGF-CC inhibition might provide a common therapeutic opportunity for treatment of both acute and progressive neuropathology in humans. In this review we will summarize what is known about the role of PDGF-CC in neurovascular signaling events and the variety of seemingly different neuropathologies it is involved in. We will also discuss the pharmacological means of therapeutic interventions for anti-PDGF-CC therapy and ongoing clinical trials. In summary: inhibition of PDGF-CC signaling can be protective for immediate injury and decrease the long-term neurodegenerative consequences.

Traumatic brain injury as a risk factor for Alzheimer's disease: current knowledge and future directions

There is growing concern about the late effects of traumatic brain injury (TBI). This scoping review summarizes clinical research from the past 10 years that evaluates the relationship between TBI and Alzheimer's disease. This review identified five studies that found increased risk for dementia after TBI, two studies that found no increased risk and four studies that found a relationship only under certain conditions or in specified subsamples. Methodological differences across studies preclude direct comparison of results, and discrepant findings elucidate the complex course of post-TBI neurodegeneration. We discuss the factors that influence the strength and direction of the relationship between TBI and Alzheimer's disease, and the implications of this body of research for patient care and future research.

The Impact of Traumatic Brain Injury on the Aging Brain

Traumatic brain injury (TBI) has come to the forefront of both the scientific and popular culture. Specifically, sports-related concussions or mild TBI (mTBI) has become the center of scientific scrutiny with a large amount of research focusing on the long-term sequela of this type of injury. As the populace continues to age, the impact of TBI on the aging brain will become clearer. Currently, reports have come to light that link TBI to neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, as well as certain psychiatric diseases. Whether these associations are causations, however, is yet to be determined. Other long-term sequelae, such as chronic traumatic encephalopathy (CTE), appear to be associated with repetitive injuries. Going forward, as we gain better understanding of the pathophysiological process involved in TBI and subclinical head traumas, and individual traits that influence susceptibility to neurocognitive diseases, a clearer, more comprehensive understanding of the connection between brain injury and resultant disease processes in the aging brain will become evident.

Understanding the pathology and treatment of traumatic brain injury and posttraumatic stress disorder: a therapeutic role for hyperbaric oxygen therapy

Traumatic brain injury (TBI) is an intracranial injury caused by external trauma leading to different degrees of brain damage. TBI can cause a wide array of symptoms and range in severity from concussion to coma and death. The link between TBI and posttraumatic stress disorder (PTSD) has received increasing attention due to the high incidence of these conditions in soldiers returning from recent conflicts. TBI has been associated with an increased risk of PTSD. Additionally, TBI and PTSD often demonstrate overlapping symptoms. In this article, we discuss the different forms of TBI and their links to PTSD. We also discuss current therapies for TBI and PTSD, in particular detailing the therapeutic potential of hyperbaric oxygen therapy in the management of these conditions.

Neuroepidemiology of traumatic brain injury

Traumatic brain injury (TBI) is a significant public-health concern. TBI is defined as an acute brain injury resulting from mechanical energy to the head from external physical forces. Some of the leading causes of TBI include falls, assaults, motor vehicle or traffic accidents, and sport-related concussion. Two of the most common identified risk factors are sex (males are nearly three times more likely to suffer a TBI than females); and a bimodal age pattern (persons 65 years and older, and children under 14 years old). It is estimated that approximately 1.5-2 million Americans suffer from TBI annually. TBIs account for around 1.4 million emergency room visits, 275 000 hospital admissions, and 52 000 deaths in the USA each year. TBI contributes to approximately 30% of all deaths in the USA annually. In Australia, it is estimated that approximately 338 700 individuals (1.9% of the population) suffer from a disability related to TBI. Of these, 160 200 were severely or profoundly affected by acquired brain injury, requiring daily support. In the UK, TBI accounted for 3.4% of all emergency department attendances annually. An overall rate of 453 per 100 000 was found for all TBI severities, of which 40 per 100 000 (10.9%) were moderate to severe. TBI often results in residual symptoms that affect an individual's cognition, movement, sensation, and/or emotional functioning. Recovery and rehabilitation from TBI may require considerable resources and may take years. Some individuals never fully recover, and some require lifetime ongoing care and support. TBI has an enormous social and financial cost, with estimates of the annual financial burden associated with TBI ranging between 9 and 10 billion US dollars.

France establishes guidelines for treating neurobehavioral disorders following traumatic brain injury

This paper comments on the report by a committee of La Société Française de Médecine Physique et de Réadaptation (SOFMER) in response to the Haute Autorité de santé in France concerning the classification and clinical management of disorders of comportment following moderate to severe traumatic brain injury (TBI). In view of the large number of patients and families affected by these disorders, there is a strong rationale for these guidelines to ensure that clinical assessment and treatment is evidence-based. The report is viewed from the perspective of current research on disorders of comportment and in relation to recent reviews and meta-analyses on this topic. Comments on the classification draw on pathophysiology and brain imaging in addition to the clinical literature. The SOFMER report and recent projects in North America are compared for trends in the development of recommended assessment scales and standard, evidence-based treatment protocols for pharmacologic and non-pharmacologic interventions. Collaborative, multinational investigations of TBI are also noted, which are advancing progress toward guidelines for clinical management.

Repetitive head trauma, chronic traumatic encephalopathy and tau: Challenges in translating from mice to men

Chronic traumatic encephalopathy (CTE) is a neurological and psychiatric condition marked by preferential perivascular foci of neurofibrillary and glial tangles (composed of hyperphosphorylated-tau proteins) in the depths of the sulci. Recent retrospective case series published over the last decade on athletes and military personnel have added considerably to our clinical and histopathological knowledge of CTE. This has marked a vital turning point in the traumatic brain injury (TBI) field, raising public awareness of the potential long-term effects of mild and moderate repetitive TBI, which has been recognized as one of the major risk factors associated with CTE. Although these human studies have been informative, their retrospective design carries certain inherent limitations that should be cautiously interpreted. In particular, the current overriding issue in the CTE literature remains confusing in regard to appropriate definitions of terminology, variability in individual pathologies and the potential case selection bias in autopsy based studies. There are currently no epidemiological or prospective studies on CTE. Controlled preclinical studies in animals therefore provide an alternative means for specifically interrogating aspects of CTE pathogenesis. In this article, we review the current literature and discuss difficulties and challenges of developing in-vivo TBI experimental paradigms to explore the link between repetitive head trauma and tau-dependent changes. We provide our current opinion list of recommended features to consider for successfully modeling CTE in animals to better understand the pathobiology and develop therapeutics and diagnostics, and critical factors, which might influence outcome. We finally discuss the possible directions of future experimental research in the repetitive TBI/CTE field.