Form Of Traumatic Brain Injury Research Articles

Assessment of vision in concussion.

To review emerging vision-based assessments in the evaluation of concussion. Involvement of the visual pathways is common following concussion, the mildest form of traumatic brain injury. The visual system contains widely distributed networks that are prone to neurophysiologic changes after a concussion, resulting in visual symptoms and ocular motor dysfunction. Vision-based testing is increasingly used to improve detection and assess head injury. Several rapid automatized naming (RAN) tasks, such as the King-Devick test and the Mobile Universal Lexicon Evaluation System, show capacity to identify athletes with concussion. Video-oculography (VOG) has gained widespread use in eye-tracking and gaze-tracking studies of head trauma from which objective data have shown increased saccadic latencies, saccadic dysmetria, errors in predictive target tracking, and changes in vergence in concussed individuals. RAN tasks demonstrate promise as rapid screening tools for concussion. Further investigation will involve assessment of the role for age, characterization of learning effects over repeated measurements, and identification of optimal thresholds for clinically significant performance decrements. Various RAN tasks are likely to be functionally distinct, engaging different neural networks according to the demands of each task. Measures of saccades, smooth pursuit eye-movements, the vestibulo-ocular reflex and, more recently, disparity vergence are candidate vision-based markers for concussion. Work to adopt these assessments to the sideline or clinical environments is ongoing.

Association of Concussion With the Risk of Suicide

Concussion is the most common form of traumatic brain injury (TBI). While most patients fully recover within 1 week of injury, a subset of patients might be at a higher risk of suicide. To assess the risk of suicide after concussion. We performed a systematic search of Medline (PubMed), Embase, PsycINFO, and Published International Literature on Traumatic Stress (PILOTS) from 1963 to May 1, 2017. We also searched Google Scholar and conference proceedings and contacted experts in the field to seek additional studies. Studies that quantified the risk of suicide, suicide attempt, or suicidal ideation after a concussion and/or mild TBI were included. Studies that included children and adults, including military and nonmilitary personnel, were included. Two authors independently reviewed all titles and abstracts to determine study eligibility. Study characteristics were extracted independently by 2 trained investigators. Study quality was assessed using the Newcastle-Ottawa Scale. Study data were pooled using random-effects meta-analysis. The primary exposure was concussion and/or mild TBI, and the primary outcome was suicide. Secondary outcomes were suicide attempt and suicidal ideation. Data were extracted from 10 cohort studies (n = 713 706 individuals diagnosed and 6 236 010 individuals not diagnosed with concussion and/or mild TBI), 5 cross-sectional studies (n = 4420 individuals diagnosed and 11 275 individuals not diagnosed with concussion and/or mild TBI), and 2 case-control studies (n = 446 individuals diagnosed and 8267 individuals not diagnosed with concussion and/or mild TBI). Experiencing concussion and/or mild TBI was associated with a 2-fold higher risk of suicide (relative risk, 2.03 [95% CI, 1.47-2.80]; I2 = 96%; P < .001). In 2 studies that provided estimates with a median follow-up of approximately 4 years, 1664 of 333 118 individuals (0.50%) and 750 of 126 114 individuals (0.59%) diagnosed with concussion and/or mild TBI died by suicide. Concussion was also associated with a higher risk of suicide attempt and suicide ideation. The heightened risk of suicide outcomes after concussion was evident in studies with and without military personnel. Experiencing concussion and/or mild TBI was associated with a higher risk of suicide. Future studies are needed to identify and develop strategies to decrease this risk.

No change in plasma tau and serum neurofilament light concentrations in adolescent athletes following sport-related concussion.

Sport-related concussion (SRC), a mild form of traumatic brain injury (TBI), is a common injury in contact sports. Health care professionals rely on subjective criteria (e.g., symptoms), as there is no objective marker for identification of athletes with SRC. Blood-based biomarkers have shown promise as diagnostic and prognostic tools following TBI and SRC. In the present study, we examined plasma tau and serum NF-L, two biomarkers for neuronal/axonal injury, concentrations at preseason and following SRC in contact sport athletes (n = 11) using ultrasensitive single molecule array (Simoa) assays. Preseason baseline samples were collected, and post-concussion samples were obtained at 6- and 14-days following injury. We found no difference between baseline, 6-day and 14-day post-concussion concentrations of tau (p = 0.14) or NF-L (p = 0.53). Further, no difference was found between preseason baseline and all post-SRC samples for tau (p = 0.22) or NF-L (p = 0.98). The total number of symptoms reported on the Standardized Assessment of Concussion– 3rd Edition (SCAT3) and associated symptom severity scores increased from preseason to 6-days post-SRC but returned to baseline values at 14-days (p = 0.02 and p = 0.003, respectively). These results suggest that the severity of neuronal injury in this cohort of contact sport athletes with clinical uncomplicated SRC was too low to be detected by tau and NF-L measurements in blood samples obtained at 6- and 14-days post-injury.

Concussion management in combat sports: consensus statement from the Association of Ringside Physicians

Various organisations and experts have published numerous statements and recommendations regarding different aspects of sports-related concussion including definition, presentation, treatment, management and return to play guidelines.1–7To date, there have been...

The intracranial number of foreign bodies as a predictor of mortality after penetrating brain injury

IntroductionPenetrating brain injury (PBI) is the most lethal form of traumatic brain injury, which is a leading cause of mortality. PBI has a mortality rate of 23%–93% and 87%–100% with poor neurological status. Despite the use of various prognostic factors there is still a need for a specific prognostic factor for early prediction of mortality in PBI to reduce mortality and provide good outcomes with cost-effective surgical treatments. The aim of this study was to investigate the predictive value of the number of intracranial foreign bodies (FBs) on mortality in PBI in the Emergency Department. MethodsThe study included 95 patients admitted with PBI caused by barrel bomb explosion. The intracranial number of FB was examined by brain computed tomography. Logistic regression was used to assess the association of the intracranial number of FB on mortality. Correlation analyses were performed to investigate the association of Glasgow Coma Scale (GCS) with intracranial number of FB. ResultsThe optimal cut-off value of the intracranial number of FB calculated for mortality was 2, which was effective for predicting mortality (p < .001). In patients with >2 intracranial FB, the mortality rate was statistically significantly 51-fold higher than those with ≤2 (p < .001). A statistically significant negative correlation was determined between GCS and number FB (r = −0.697; p < .001). ConclusionWhen the intracranial number of FB was >2, mortality significantly increased in patients with PBI. The intracranial number of FBs may be considered as a novel prognostic factor for the prediction of mortality in PBI.

Acute concussion: making the diagnosis and state of the art management.

Concussion is an increasingly common injury in children. We aim to review the basic epidemiology and management of acute concussion and highlight recent studies that have contributed to our understanding of care for this injury. While concussion is considered a 'mild' form of traumatic brain injury, recent evidence suggests that as many as 30% of children are still symptomatic 1 month after injury. Although there is increasing interest in finding objective measures of injury and recovery, emerging imaging and serum biomarkers are not ready for routine clinical use. Identification of children at risk for prolonged symptoms is vital. Prolonged rest after injury may worsen outcomes. Concussion is a common injury in children. Objective measures of injury and recovery are needed, as are targeted therapies to mitigate the risk of prolonged recovery after injury.

A raised serum lactate level is an independent predictor of in-hospital mortality in patients with isolated cerebral gunshot wounds.

Cerebral gunshot wounds (CGSWs) represent a highly lethal form of traumatic brain injury, and triaging these patients is difficult. The prognostic significance of the serum lactate level in the setting of CGSWs is largely unknown. To examine the relationship between elevated serum lactate levels and mortality in patients with isolated CGSWs. A retrospective review of the regional trauma registry was undertaken at the Pietermaritzburg Metropolitan Trauma Service, South Africa, over a 5-year period from 1 January 2010 to 31 December 2014. All patients with an isolated CGSW were included. A total of 102 patients with isolated CGSWs were identified. Of these, 92.2% (94/102) were male. The mean age (standard deviation) was 29 (8) years, and the in-hospital mortality rate was 21.6% (22/102). The mean serum lactate level was significantly higher among non-survivors than among survivors (6.1 mmol/L v. 1.3 mmol/L; p&lt;0.001). Lactate levels among non-survivors were &lt;2 mmol/L in 4.5%, 2 - 3.99 mmol/L in 9.1%, 4 - 5.99 mmol/L in 36.4% and ≥6 mmol/L in 50.0%. The odds ratio for mortality with a lactate level of 4 - 5.99mmol/L was 67 (95% confidence interval (CI) 1.7 - 2 674.2), while for a lactate level of ≥6 mmol/L it was 1 787 (95% CI 9.0 - 354116.1). The serum lactate level accurately predicted mortality even after adjustment for other variables. Based on a receiver operating curve analysis, an optimal cut-off of 3.3 mmol/L for serum lactate as a predictor for mortality was identified (area under the curve = 0.957). CGSWs are associated with significant mortality, and a raised serum lactate level appears to be an independent predictor of in-hospital mortality. It is a potentially useful adjunct in the resuscitation room for identifying patients with a very poor prognosis.

Acute hemiplegia secondary to diffuse axonal injury after traumatic brain injury

The diffuse axonal injury (DAI) is one of the main forms of traumatic brain injury, characterized by involvement of the axonal fibres of the white matter of the brain.The mechanism of such injury is the sum of forces of acceleration, deceleration and rotation, mainly in brain structures close to the middle line, including the dorsolateral superior region of the pons and midbrain, splenium of the corpus callosum, parasagittal white matter, and occasionally the internal capsule. Because of the importance of the structures commonly involved and its high incidence, close to 50 % of cases of severe brain trauma, the DAI is a major cause of cognitive impairment as well as the persistent vegetative state related to trauma. However, the occurrence of motor deficit outside of this area is uncommon in literature, and it is obviously dependant on the anatomical region involved6. The objective of this paper is to present a case of hemiplegia secondary to DAI.

A brief introduction to the thematic series of neurorestoration in neurotrauma

A brief introduction to the thematic series of neurorestoration in neurotrauma Shiqing Feng Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, People’s Republic of ChinaNeurotrauma is generally regarded as a public health problem that remains a leading cause of disabilities and death worldwide, and the costs to communities in terms of suffering and economics are enormous. Neurotrauma may be in the form of traumaticbrain injury (TBI) or traumatic spinal cord injury (TSCI), or others, all of which are a heterogeneous group of pathologic disorders. The common causes of neurotrauma are road traffic accidents, falls and violence. Even current neurorestorative strategies, including cell therapy, neuromodulation and neurorestorative surgery, can restore patients with neurotrauma to some degree of neurological functions;1–6 there exists an urgent demand to find more effective methods for neurotrauma to better restore damaged or lost neurological functions and/or structures. The objective of this thematic series is to report the latest advances in neurotrauma to motivate clinicians and scientists to know more and find more effectively neurorestorative methods for neurotrauma. A brief summary of three papers in the thematic series is given in the following sections.

Assessing Trends in the Epidemiology of Concussions Among High School Athletes

Objectives:Approximately 300,000 youth athletes suffer a mild form of traumatic brain injury (TBI) known as a concussion annually while participating in organized athletics. Using data from the most recent 10-year period available, this study aimed to track national trends in high school sports-related concussion incidences over time, identify whether a particular sport predisposes athletes to a higher incidence of concussions, and evaluate the association between concussion occurrences and the enactment of TBI legislation that began in 2009.Methods:Injury data for academic years 2005-2006 through 2014-2015 was collected from annual reports generated by the High School Reporting Information Online sports injury surveillance system, which prospectively captures injury data directly from athletic trainers at participating U.S. high schools. Relative proportions of total estimated concussions to total estimated injuries were compared using an injury proportion ratio (IPR) and corresponding 95% confidence intervals (CI). Concussion rate was defined as the number of concussions per 10,000 athlete-exposures (AEs, one athlete participating in one practice or competition), and rates were compared using a rate ratio (RR) and 95% CI.Results:The overall number of concussions increased 2.2-fold (p<0.0001) between 2005-2006 and 2014-2015, and significant increases were also found in the overall concussion rate (RR=2.30, 95% CI [2.04-2.59]; p<0.0001) and the overall proportion of concussions (IPR=2.68, 95% CI [2.66-2.70]; p<0.0001). Players injured during the 2014-2015 school year were more likely to have sustained a concussion if they played girls soccer than if they played girls volleyball (IPR=1.32, 95% [1.30-1.35]; p<0.0001), girls basketball (IPR=1.35, 95% CI [1.33-1.37]; p<0.0001), or boys football (IPR=1.40, 95% CI [1.39-1.41]; p<0.0001) (Table 1).Conclusion:The overall rate and proportion of concussions increased significantly post-TBI law enactment, suggesting an association between the passage of TBI laws and concussion incidences. To our knowledge, this is the first study to report that concussions now account for a higher proportion of injuries in girls soccer than boys football. Currently, no state TBI laws address the sport- or gender-specific differences identified by this study. Future studies should focus on examining specific risk factors, developing targeted measures to reduce the number of preventable concussions, and developing diagnostic and treatment algorithms to protect young athletes and improve outcomes. Table 1.Comparison of concussion rates and proportions for individual sports during the 2005-2006 and 2014-2015 academic years. aData obtained from High School Reporting Information Online. *p < 0.01.Concussions/10,000 AESaConcussions (as % of total injuries)aSport2005-20062014-2015RR [95% CI]2005-20062014-2015IPR [95% CI]Booys Football4.569.412.06 [1.74-2.44]*10.5%24.7%2.36 [2.34-2.38]*Booys Soccer2.323.031.30 [0.84-2.00]9.6%18.9%1.98 [1.95-2.01]*Girls Soccer3.589.102.52 [1.83-3.49]*15.2%34.5%2.27 [2.24-2.30]*Girls Volleyball0.512.885.68 [2.42-13.29]*3.1%26.1%8.48 [8.14-8.884]*Boys Basketwell0.660.951.51 [0.76-2.99]*3.5%8.8%2.51 [2.41-2.62]*Girls Basketwell2.394.231.79 [1.22-2.62]*11.9%25.6%2.15 [2.11-2.20]*Boys Wrestling1.224.003.33 [1.99-5.57]*4.9%18.8%3.85 [3.73-3.97]*Boys Baseball0.251.356.13 [2.11-17.79]2.1%14.3%6.83 [6.46-7.22]*Girls Softball0.471.834.09 [1.65-10.12]*4.2%18.3%4.38 [4.20-4.57]*

Abstracts from The 35th Annual National Neurotrauma Symposium July 7-12, 2017 Snowbird, Utah.

Abstracts from The 35th Annual National Neurotrauma Symposium July 7-12, 2017 Snowbird, Utah.

Mild Traumatic Brain Injury Leads to Decreased Inhibition and a Differential Response of Calretinin Positive Interneurons in the Injured Cortex.

It is clear that even mild forms of traumatic brain injury (TBI) can have lasting cognitive effects; however, the specific cellular changes responsible for the functional deficits remain poorly understood. Previous studies suggest that not all neurons respond in the same way and that changes to neuronal architecture may be subtype specific. The current study aimed to characterize the response of interneurons to TBI. To model TBI in vitro, the neurites of primary cortical neurons were transected at 15 days in vitro. In response, calretinin+ interneurons underwent significant neurite remodeling around the injury site. By examining the response of pyramidal neurons, GAD67-GFP+ interneurons, and calretinin+ interneurons to the injury, we found that this response was specific to the calretinin+ cells. To determine whether calretinin+ interneurons respond in this way to a clinically relevant in vivo model of mild diffuse and focal injury, we subjected mice to the lateral fluid percussion injury model. We found that calretinin+ interneuron density was unaltered by this mild injury, but consistent with our in vitro data, these neurons underwent morphological alterations in their dendrites. These alterations evolved over a 28-day period, and calretinin+ interneurons in the injured mice had a reduction in mean dendrite length and reduced number of secondary dendrites than those in the sham-injured controls by 7 days post-injury. Further, these structural alterations were accompanied by a reduction in the frequency of miniature inhibitory post-synaptic currents in layer V pyramidal neurons. These data suggest that even a mild TBI can lead to an overall change in the excitatory/inhibitory balance of the cortex that may play an important role in the longer-term behavioral pathology associated with mild TBI.

Serotonin axons in the neocortex of the adult female mouse regrow after traumatic brain injury.

It is widely held that injured neurons in the central nervous system do not undergo axonal regrowth. However, there is mounting evidence that serotonin axons are a notable exception. Serotonin axons undergo long-distance regrowth in the neocortex after amphetamine lesion, and, following a penetrating stab injury, they can regrow from cut ends to traverse the stab rift. Traumatic brain injury (TBI) is clinically prevalent and can lead to pathologies, such as depression, that are related to serotonergic dysfunction. Thus, whether serotonin axons can regrow after TBI is an important question. We used two models for TBI-a persistent open skull condition and controlled cortical impact-to evoke injury in adult female mouse neocortex, and assessed serotonin axon density 1 week, 1 month, and 3 months after injury by serotonin transporter immunohistochemistry. We found that after both forms of TBI, serotonin axon density is decreased posterior but not anterior to the injury site when measured in layer 1 at 1 week post surgery, and that serotonin axons are capable of regrowing into the distal zone to increase density by 1 month post surgery. This pattern is consistent with the anterior-to-posterior course of serotonin axons in the neocortex. TBI in these models is associated with significant reactive astrogliosis both anterior and posterior to the impact, but the degree of reactive astrogliosis is not correlated with serotonin axon density when measured 1 week after TBI. Microglial density remains constant following both types of injuries, but microglial condensation was detected 1 week after controlled cortical impact.

Nonpharmacological Treatment of Postconcussion Syndrome

A concussion is a mild form of traumatic brain injury that results in symptoms of headache, dizziness, fatigue, and concentration or memory difficulty. Postconcussion syndrome is defined as the persistence of these symptoms beyond 3 months. These initial symptoms can be debilitating and can lead to further physiological or psychological impairments such as depression, slowed processing speed, and gait imbalances. Although pharmacological interventions with antidepressants and stimulants may be useful, some patients may not accept or adequately respond to these interventions. A nonpharmacological approach to treating postconcussion syndrome uses a holistic approach to treat both the mind and body. Nonprescription therapies include vestibular rehabilitation for dizziness, vertigo, and balance/gait difficulties, as well as cognitive-behavioral therapy for both somatic and neuropsychiatric symptoms. The timing and ratio of rest versus rehabilitation through activity is case specific and a matter of ongoing clinical judgment given the uniqueness of each injury and the variety of postconcussive presentations. [ Psychiatr Ann . 2017;47(2):88–91.]

A multi-body dynamics study on a weight-drop test of rat brain injury

Traumatic brain injury (TBI), induced by impact of an object with the head, is a major health problem worldwide. Rats are a well-established animal analogue for study of TBI and the weight-drop impact-acceleration (WDIA) method is a well-established model in rats for creating diffuse TBI, the most common form of TBI seen in humans. However, little is known of the biomechanics of the WDIA method and, to address this, we have developed a four-degrees-of-freedom multi-body mass-spring-damper model for the WDIA test in rats. An analytical expression of the maximum skull acceleration, one of the important head injury predictor, was derived and it shows that the maximum skull acceleration is proportional to the impact velocity but independent of the impactor mass. Furthermore, a dimensional analysis disclosed that the maximum force on the brain and maximum relative displacement between brain and skull are also linearly proportional to impact velocity. Additionally, the effects of the impactor mass were examined through a parametric study from the developed multi-body dynamics model. It was found that increasing impactor mass increased these two brain injury predictors.

A model of recurrent concussion that leads to long-term motor deficits, CTE-like tauopathy and exacerbation of an ALS phenotype.

Concussion injury is the most common form of traumatic brain injury (TBI). How recurrent concussions alter long-term outcomes is poorly understood, especially as related to the development of neurodegenerative disease. We evaluated the functional and pathological consequences of repeated TBI over time in wild type (WT) rats as well as rats harboring the human SOD1 mutation ("SOD1"), a model of familial amyotrophic lateral sclerosis (ALS). A total of 42 rats, 26 WT and 16 SOD1, were examined over a study period of 25 weeks (or endpoint). At postnatal day 60, 20 WT and 7 SOD1 rats were exposed to mild, bilateral TBI once per week for either 2 weeks (2×TBI) or 5 weeks (5×TBI) using a controlled cortical impact device. Six WT and nine SOD1 rats underwent sham injury with anesthesia alone. Twenty WT rats were euthanized at 12 weeks after first injury and six WT rats were euthanized at 25 weeks after first injury. SOD1 rats were euthanized when they reached ALS disease endpoint. Weekly body weights and behavioral assessments were performed. Tauopathy in brain tissue was analyzed using immunohistochemistry. 2XTBI injured rats initially demonstrated recovery of motor function but failed to recover to baseline within the 12-week study period. Relative to both 2XTBI and sham controls, 5XTBI rats demonstrated significant deficits that persisted over the 12-week period. SOD1 5XTBI rats reached a peak body weight earlier than sham SOD1 rats, indicating earlier onset of the ALS phenotype. Histologic examination of brain tissue revealed that, in contrast with sham controls, SOD1 and WT TBI rats demonstrated cortical and corpus collosum thinning and tauopathy, which increased over time. Unlike previous models of repeat brain injury, which demonstrate only transient deficits in motor function, our concussion model of repeat, mild, bilateral TBI induced long-lasting deficits in motor function, decreased cortical thickness, shrinkage of the corpus callosum, increased brain tauopathy, and earlier onset of ALS symptoms in SOD1 rats. This model may allow for a greater understanding of the complex relationship between TBI and neurodegenerative diseases and provides a potential method for testing novel therapeutic strategies.

Civilian cerebral gunshot wounds: a South African experience.

Cerebral gunshot wounds represent one of the most lethal forms of traumatic brain injury, but there is a paucity of literature on the topic, especially from the developing world. We reviewed our experience and describe the spectrum and outcome of civilian cerebral gunshot wounds in a major metropolitan trauma centre in South Africa. This was a retrospective study of all patients with isolated cerebral gunshot wounds managed by the Pietermaritzburg Metropolitan Trauma Service over a 5-year period from 2010 to 2014. One hundred and two patients were included, 92% (94/102) were male and the mean age was 29 years. Fifty-four per cent (55/102) of all patients were from urban areas. The mean time from injury to arrival was 6 h (standard deviation: 5) for urban patients and 15 h (standard deviation: 5.2) for rural patients (P < 0.001). Ninety-four per cent (94/102) of all injuries were related to interpersonal violence and involved low velocity firearms. Twenty per cent of all patients (20/102) had a Glasgow Coma Scale 3-8, 20% (20/102) 9-12 and 61% (61/102) 12-15. All 102 patients underwent computed tomography scans. Thirty per cent (31/102) required neurosurgical interventions. The overall mortality rate was 22% (22/102). There was a significant difference in mortality between urban and rural patients (9% versus 36%, P < 0.001). Cerebral gunshot wounds are associated with significant mortality and protracted delay to definitive care is common in our setting. Those who survive the delayed transfer to definitive care generally do well and have reasonably good clinical outcomes.

Stratifying Heterogeneous Dimension of Neurodegenerative Diseases: Intervention for Stipulating Epigenetic Factors to Combat Oxidative Stress in Human Brain

Neurodegenerative diseases affect the neurons of the human brain and decline the neural activities causing neurocognitive dysfunctions and brain and behavioral disorders. An intensive immunotherapy is used to alter the course of multiple sclerosis, a common form of neurodegeneration, by controlling oxidative stress, recovering mitochondrial injury, and rehabilitating channelopathy dysfunctions. However, little is known about how the epigenetic factors can regulate atrophy genesis at hippocampal region, which prevents neurodegeneration. Further, traumatic brain injury leads to neurodegeneration. However, the onset of the later is not yet successfully monitored. Simultaneously, discrimination between neurodegeneration due to ageing and traumatic brain injury has not been addressed in the existing literature. Therefore, we present different forms of traumatic brain injury that trigger neurotoxicity, leading to the classification of onset stage of neurodegenerative pathways. We discuss how the immune system orchestrates changes in neurogenesis in presence of physiological stimuli. In our view, the epigenetic mode of treatment successfully intervenes all forms of neurodegenerative disease in both ageing and traumatic condition. Here, we establish a cross talk between epigenetic factors and neural immunology to balance oxidative stress at hippocampal regions.

Traumatic brain injury in pedestrian–vehicle collisions: Convexity and suitability of some functionals used as injury metrics

Background and objectiveAbrupt accelerations or decelerations can cause large strain in brain tissues and, consequently, different forms of Traumatic Brain Injury (TBI). In order to predict the effect of the accelerations on the soft tissues of the brain, many different injury metrics have been proposed (typically, an injury metric is a real valued functional of the accelerations). The objective of this article is to make a formal and empirical comparison, in order to identify general criteria for reasonable injury metrics, and propose a general guideline to avoid ill-proposed injury metrics. MethodsA medium-sized sample of vehicle–pedestrian collisions, from Post Mortem Human Subject (PMHS) tests, is analyzed. A statistical study has been conducted in order to determine the discriminant power of the usual metrics. We use Principal Component Analysis to reduce dimensionality and to check consistency among the different metrics. In addition, this article compares the mathematical properties of some of these functionals, trying to identify the desirable properties that any of those functionals needs to fulfill in order to be useful for optimization. ResultsWe have found a pair-wise consistency of all the currently used metrics (any two injury metrics are always positively related). In addition, we observed that two independent principal factors explain about 72.5% of the observed variance among all collision tests. This is remarkable because it indicates that despite high number of different injury metrics, a reduced number of variables can explain the results of all these metrics. With regard to the formal properties, we found that essentially all injury mechanisms can be accounted by means of scalable, differentiable and convex functionals (we propose to call minimization suitable injury metric any metric having these three formal properties). In addition three useful functionals, usable as injury metrics, are identified on the basis of the empirical comparisons. ConclusionsThe commonly used metrics are highly consistent, but also highly redundant. Formal minimal conditions of a reasonable injury metric has been identified. Future proposals of injury metrics can benefit from the results of this study.

Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature.

Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.