Advances in Sport Concussion Assessment: From Behavioral to Brain Imaging Measures

Effect of education and language on baseline concussion screening tests in professional baseball players

OBJECTIVE

The purpose of the present study was to investigate the possible effects of sociocultural influences, specifically pertaining to language and education, on baseline neuropsychological concussion testing as obtained via immediate postconcussion assessment and cognitive testing (ImPACT) of players from a professional baseball team.

DESIGN

A retrospective chart review.

SETTING

Baseline testing of a professional baseball organization.

PARTICIPANTS

Four hundred five professional baseball players.

INDEPENDENT VARIABLES

Age, languages spoken, hometown country location (United States/Canada vs overseas), and years of education.

MAIN OUTCOME MEASURES

The 5 ImPACT composite scores (verbal memory, visual memory, visual motor speed, reaction time, impulse control) and ImPACT total symptom score from the initial baseline testing.

RESULTS

The result of t tests revealed significant differences (P < 0.05) when comparing native English to native Spanish speakers in many scores. Even when corrected for education, the significant differences (P < 0.05) remained in some scores.

CONCLUSIONS

Sociocultural differences may result in differences in computer-based neuropsychological testing scores.

Time course of clinical and electrophysiological recovery after sport-related concussion

BACKGROUND AND PURPOSE

Recent neuroimaging studies suggest that abnormalities in brain function after concussion exist beyond the point of observed clinical recovery. This study investigated the relationship between an index of brain dysfunction (traumatic brain injury [TBI] Index), concussion severity, and outcome.

METHODS

EEG was collected from forehead locations in 65 male athletes with concussion within 24 hours of concussion, with follow-up at 8 and 45 days postinjury. Neurocognitive and symptom assessments were also performed and used to classify subjects in mild or moderate concussion categories. Time to return to play was recorded.

RESULTS

The TBI Index was higher in the moderate than mild concussion group at injury, day 8, and day 45. The moderate group had increased symptoms and decreased cognitive performance only at the time of injury. At the time of injury, only the TBI Index was significantly associated with the length of time to return to play.

CONCLUSIONS

Recovery of brain function after sport-related concussion may extend well beyond the time course of clinical recovery and be related to clinical severity. An index of brain dysfunction may be an objective indicator of injury, recovery, and readiness to return to play. The relatively small sample indicates the need for further study on the time course of physiological recovery.

Toward objective markers of concussion in sport: a review of white matter and neurometabolic changes in the brain after sports-related concussion

Abstract Sports-related concussion is an issue that has piqued the public's attention of late as concerns surrounding potential long-term sequelae as well as new methods of characterizing the effects of this form of injury continue to develop. For the most part, diagnosis of concussion is based on subjective clinical measures and thus is prone to under-reporting. In the current environment, where conventional imaging modalities, such as computed tomography and magnetic resonance imaging, are unable to elucidate the degree of white matter damage and neurometabolic change, a discussion of two advanced imaging techniques-diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS)-is undertaken with a view to highlighting their potential utility. Our aim is to outline a variety of the approaches to concussion research that have been employed, with special attention given to the clinical considerations and acute complications attributed to concussive injury. DTI and MRS have been at the forefront of research as a result of their noninvasiveness and ease of acquisition, and hence it is thought that the use of these neuroimaging modalities has the potential to aid clinical decision making and management, including guiding return-to-play protocols.

Acute clinical recovery from sport-related concussion

Concussion is a highly prevalent injury in contact and collision sports that has historically been poorly understood. An influx of sport-concussion research in recent years has led to a dramatic improvement in our understanding of the injury's defining characteristics and natural history of recovery. In this review, we discuss the current state of knowledge regarding the characteristic features of concussion and typical acute course of recovery, with an emphasis on the aspects of functioning most commonly assessed by clinicians and researchers (e.g., symptoms, cognitive deficits, postural stability). While prototypical clinical recovery is becoming better understood, questions remain regarding what factors (e.g., injury severity, demographic variables, history of prior concussions, psychological factors) may explain individual variability in recovery. Although research concerning individual differences in response to concussion is relatively new, and in many cases limited methodologically, we discuss the evidence about several potential moderators of concussion recovery and point out areas for future research. Finally, we describe how increased knowledge about the negative effects of and recovery following concussion has been translated into clinical guidelines for managing concussed athletes.

Episodic memory in former professional football players with a history of concussion: an event-related functional neuroimaging study

Previous research has demonstrated that sport-related concussions can have short-term effects on cognitive processes, but the long-term consequences are less understood and warrant more research. This study was the first to use event-related functional magnetic resonance imaging (fMRI) to examine long-term differences in neural activity during memory tasks in former athletes who have sustained multiple sport-related concussions. In an event-related fMRI study, former football players reporting multiple sport-related concussions (i.e., three or more) were compared with players who reported fewer than three concussions during a memory paradigm examining item memory (i.e., memory for the particular elements of an event) and relational memory (i.e., memory for the relationships between elements). Behaviorally, we observed that concussion history did not significantly affect behavioral performance, because persons in the low and high concussion groups had equivalent performance on both memory tasks, and in addition, that concussion history was not associated with any behavioral memory measures. Despite demonstrating equivalent behavioral performance, the two groups of former players demonstrated different neural recruitment patterns during relational memory retrieval, suggesting that multiple concussions may be associated with functional inefficiencies in the relational memory network. In addition, the number of previous concussions significantly correlated with functional activity in a number of brain regions, including the medial temporal lobe and inferior parietal lobe. Our results provide important insights in understanding the long-term functional consequences of sustaining multiple sports-related concussions.

Transcranial magnetic stimulation-electroencephalography responses in recovered and symptomatic mild traumatic brain injury

Mild traumatic brain injury (mTBI) may cause diffuse damage to the brain, especially to the frontal areas, that may lead to persistent symptoms. We studied participants with past mTBI by means of navigated transcranial magnetic stimulation (nTMS) combined with electroencephalography (EEG). Eleven symptomatic and 8 recovered participants with a history of single mTBI and 9 healthy controls participated. Average time from injury to testing was 5 years. The participants did not have abnormalities or signs of injury on brain magnetic resonance imaging, and they did not use any centrally acting medication. Left primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) were stimulated with nTMS and evoked potentials measured from the corresponding areas of both hemispheres. Delayed ipsilateral P30 and contralateral N45 peak latencies to left DLPFC nTMS were found in the symptomatic group, along with higher DLPFC N100 amplitudes compared with the control or recovered group. The recovered group had shorter P200 latencies in left DLPFC nTMS compared with the other groups. Both mTBI groups had higher motor thresholds compared with the control group. In left M1 nTMS, the mTBI groups showed less P30 amplitude increase, and the symptomatic group showed longer P60 interhemispheric latency difference with higher stimulation intensities. The results suggest altered brain reactivity and connectivity in mTBI. Some of the observed differences may be related to compensatory mechanisms of recovery. nTMS-EEG is a potentially useful tool for studying the effects of mTBI.

Involvement of extracellular signal regulated kinases in traumatic brain injury-induced depression in rodents

Traumatic brain injury (TBI) is the most common cause of death and acquired disability among children and young adults in the developed countries. In clinical studies, the incidence of depression is high after TBI, and the mechanisms behind TBI-induced depression remain unclear. In the present study, we subjected rats to a moderate fluid percussion into the closed cranial cavity to induce TBI. After 3 days of recovery, injured rats were given a forced swim test (FST) and novelty-suppressed feeding tests. We found that TBI rats exhibited increased duration of immobility and longer latency to begin chewing food in a new environment compared with sham-operated rats. Western blot analysis showed that TBI led to a decrease in the phosphorylated levels of extracellular signal regulated kinases (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK). Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), significantly reduced the duration of immobility when administered once per day for 14 days. Consistent with behavioral tests, fluoxetine treatment reversed TBI-induced decrease in p-ERK1/2 and p-p38 MAPK levels. Pre-treatment with a selective tryptophan hydroxylase inhibitor para-chlorophenylalanine (PCPA) blocked the antidepressant effect of fluoxetine. PCPA also prevented the effect of fluoxetine on ERK1/2 phosphorylation without affecting p38 MAPK phosphorylation. Pre-treatment with ERK inhibitor SL327 but not p38 MAPK inhibitor SB203580 prevented the antidepressant effect of fluoxetine. These results suggest that ERK1/2 plays a critical role in TBI-induced depression.

Depressive symptoms and concussions in aging retired NFL players

We examined the relationship between a remote history of concussions with current symptoms of depression in retired professional athletes. Thirty retired National Football League (NFL) athletes with a history of concussion and 29 age- and IQ-matched controls without a history of concussion were recruited. We found a significant correlation between the number of lifetime concussions and depressive symptom severity using the Beck Depression Inventory II. Upon investigating a three-factor model of depressive symptoms (affective, cognitive, and somatic; Buckley et al., 2001) from the BDI-II, the cognitive factor was the only factor that was significantly related to concussions. In general, NFL players endorsed more symptoms of depression on all three Buckley factors compared with matched controls. Findings suggest that the number of self-reported concussions may be related to later depressive symptomology (particularly cognitive symptoms of depression).

Neuroimaging of cognitive dysfunction and depression in aging retired National Football League players: a cross-sectional study

OBJECTIVES To assess cognitive impairment and depression in aging former professional football (National Football League [NFL]) players and to identify neuroimaging correlates of these dysfunctions. DESIGN We compared former NFL players with cognitive impairment and depression, cognitively normal retired players who were not depressed, and matched healthy control subjects. SETTING Research center in the North Texas region of the United States. PATIENTS Cross-sectional sample of former NFL players with and without a history of concussion recruited from the North Texas region and age-, education-, and IQ-matched controls. Thirty-four retired NFL players (mean age, 61.8 years) underwent neurological and neuropsychological assessment. A subset of 26 players also underwent detailed neuroimaging; imaging data in this subset were compared with imaging data acquired in 26 healthy matched controls. MAIN OUTCOME MEASURES Neuropsychological measures, clinical diagnoses of depression, neuroimaging mea-sures of white matter pathology, and a measure of cerebral blood flow. RESULTS Of the 34 former NFL players, 20 were cognitively normal. Four were diagnosed as having a fixed cognitive deficit; 8, mild cognitive impairment; 2, dementia; and 8, depression. Of the subgroup in whom neuroimaging data were acquired, cognitively impaired participants showed the greatest deficits on tests of naming, word finding, and visual/verbal episodic memory. We found significant differences in white matter abnormalities in cognitively impaired and depressed retired players compared with their respective controls. Regional blood flow differences in the cognitively impaired group (left temporal pole, inferior parietal lobule, and superior temporal gyrus) corresponded to regions associated with impaired neurocognitive performance (problems with memory, naming, and word finding). CONCLUSIONS Cognitive deficits and depression appear to be more common in aging former NFL players compared with healthy controls. These deficits are correlated with white matter abnormalities and changes in regional cerebral blood flow.

Avaliação comportamental do processamento auditivo em indivíduos pós - traumatismo cranioencefálico: estudo piloto

OBJETIVO: verificar o desempenho de indivíduos pós-traumatismo cranioencefálico em testes comportamentais para avaliação do processamento auditivo. MÉTODO: participaram da pesquisa 10 indivíduos audiologicamente normais com histórico de trauma craniano. Foram submetidos a: audiometria tonal liminar, logoaudiometria, medidas de imitância acústica (timpanometria e pesquisa dos reflexos acústicos) e avaliação comportamental do processamento auditivo (Testes de Localização Sonora, Memória Sequencial Verbal, Memória Sequencial Não Verbal, Padrão de Duração, Dicótico Consoante-Vogal, Dicótico de Dissílabos Alternados, Identificação de Sentenças Sintéticas com mensagem competitiva, Identificação de Intervalo Aleatório, Índice Percentual de Reconhecimento de Fala com gravação, Fala com Ruído Branco). RESULTADOS: o teste de Padrão de Duração indicou o teste com o maior número de alteração (60%). O teste com a média mais satisfatória foi o Índice Percentual de Reconhecimento de Fala com gravação (93%) e a média menos satisfatória relacionou-se ao teste Dicótico Consoante-Vogal, com 40,56%. As inversões (70%) representaram a tendência de erros no Dicótico de Dissílabos Alternados mais frequente. O processo gnósico do tipo decodificação foi o mais predominante (100%), seguido da organização (90%), não verbal (60%), codificação-perda gradual de memória (20%). Não houve alteração no processo gnósico de codificação-integração. CONCLUSÃO: os indivíduos pós-traumatismo cranioencefálico apresentam transtorno do processamento auditivo de diferentes graus, envolvendo os processos gnósicos de decodificação e organização.

Neuropathology of mild traumatic brain injury: relationship to neuroimaging findings

Neuroimaging identified abnormalities associated with traumatic brain injury (TBI) are but gross indicators that reflect underlying trauma-induced neuropathology at the cellular level. This review examines how cellular pathology relates to neuroimaging findings with the objective of more closely relating how neuroimaging findings reveal underlying neuropathology. Throughout this review an attempt will be made to relate what is directly known from post-mortem microscopic and gross anatomical studies of TBI of all severity levels to the types of lesions and abnormalities observed in contemporary neuroimaging of TBI, with an emphasis on mild traumatic brain injury (mTBI). However, it is impossible to discuss the neuropathology of mTBI without discussing what occurs with more severe injury and viewing pathological changes on some continuum from the mildest to the most severe. Historical milestones in understanding the neuropathology of mTBI are reviewed along with implications for future directions in the examination of neuroimaging and neuropathological correlates of TBI.

The young brain and concussion: imaging as a biomarker for diagnosis and prognosis

Concussion (mild traumatic brain injury (mTBI)) is a significant pediatric public health concern. Despite increased awareness, a comprehensive understanding of the acute and chronic effects of concussion on central nervous system structure and function remains incomplete. Here we review the definition, epidemiology, and sequelae of concussion within the developing brain, during childhood and adolescence, with current data derived from studies of pathophysiology and neuroimaging. These findings may contribute to a better understanding of the neurological consequences of traumatic brain injuries, which in turn, may lead to the development of brain biomarkers to improve identification, management and prognosis of pediatric patients suffering from concussion.

Neuropsychological and neurophysiological assessment of sport concussion in children, adolescents and adults

OBJECTIVE

To determine whether age differences exist with respect to neuropsychological and electrophysiological functioning following a sport concussion.

DESIGN

Cross-sectional study.

PARTICIPANTS

Ninety-six athletes (9-12 years, n = 32; 13-16 years, n = 34; adults, n = 30), half of whom had a sport concussion.

INTERVENTION

Cognitive functioning was assessed using standardized neuropsychological tests and event-related potentials elicited by a visual 3-stimulus oddball paradigm. The PCSS was used to assess symptoms experienced at the time of injury.

MAIN OUTCOME MEASUREMENTS

Neuropsychological assessment with an adaptation of the battery used by the National Hockey League. Latencies and amplitudes of the P3a and P3b were analysed in terms of group (concussed vs. control) and age.

RESULTS

All concussed athletes had significantly lower amplitude for the P3b component compared to their non-injured teammates (p > 0.05). Adolescents also showed persistent deficits in working memory (p > 0.05).

CONCLUSIONS

These data suggest persistent neurophysiological deficits that are present at least 6 months following a concussion. Moreover, adolescents are more sensitive to the consequences of concussions than are children or adults.

Multimodal Analysis: New Approaches to the Concussion Conundrum

Sports-related concussions are complex injuries with biomechanical and biochemical etiology that present with central and autonomic nervous system dysfunction. Current methods for assessing concussions and basing return-to-play decisions rely on symptom resolution, rating scales, and neuropsychological testing, all of which are indirect measures of injury severity and detect functional capabilities but do not directly measure injury location or severity. In addition, these downstream measures are susceptible to false negatives because compensatory mechanism, such as unmasking and redundancies in brain circuitry can return functional capabilities before injury resolution. The multifactorial nature of concussion necessitates rapid, inexpensive, and easily applied multimodal analysis methods that can offer greater sensitivity and specificity. This article discusses how new approaches utilizing electrophysiology (e.g., QEEG, ERP, ECG, HRV), quantified balance measures, and biochemistry are necessary to advance the science of concussion assessment, treatment, recovery projections, and return-to-play decisions. These additional assessment tools offer a more direct window into the severity and location of the injury, real-time measures of brain function, and the ability to measure the multiple body systems negatively affected by concussion.

Pediatric sports-related concussion produces cerebral blood flow alterations

OBJECTIVES

The pathophysiology of sports-related concussion (SRC) is incompletely understood. Human adult and experimental animal investigations have revealed structural axonal injuries, decreases in the neuronal metabolite N-acetyl aspartate, and reduced cerebral blood flow (CBF) after SRC and minor traumatic brain injury. The authors of this investigation explore these possibilities after pediatric SRC.

PATIENTS AND METHODS

Twelve children, ages 11 to 15 years, who experienced SRC were evaluated by ImPACT neurocognitive testing, T1 and susceptibility weighted MRI, diffusion tensor imaging, proton magnetic resonance spectroscopy, and phase contrast angiography at <72 hours, 14 days, and 30 days or greater after concussion. A similar number of age- and gender-matched controls were evaluated at a single time point.

RESULTS

ImPACT results confirmed statistically significant differences in initial total symptom score and reaction time between the SRC and control groups, resolving by 14 days for total symptom score and 30 days for reaction time. No evidence of structural injury was found on qualitative review of MRI. No decreases in neuronal metabolite N-acetyl aspartate or elevation of lactic acid were detected by proton magnetic resonance spectroscopy. Statistically significant alterations in CBF were documented in the SRC group, with reduction in CBF predominating (38 vs 48 mL/100 g per minute; P = .027). Improvement toward control values occurred in only 27% of the participants at 14 days and 64% at >30 days after SRC.

CONCLUSIONS

Pediatric SRC is primarily a physiologic injury, affecting CBF significantly without evidence of measurable structural, metabolic neuronal or axonal injury. Further study of CBF mechanisms is needed to explain patterns of recovery.

Changes in cortical plasticity after mild traumatic brain injury

PURPOSE

Even after a mild traumatic brain injury (TBI) symptoms may be long lasting and never resolve completely. The neurophysiologic substrate for such lasting deficits remains unclear. There is a lack of objective measures of early brain abnormalities following mild TBI, which could shed light on the genesis of these lasting impairments.

METHODS

Here we report findings in a previously healthy man tested 2 and 6 weeks after a well-documented concussion. Findings were compared with 12 control subjects. All subjects underwent brain magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI). Testing included neuropsychological evaluation and physiological assessment with TMS and EEG, excitatory/inhibitory balance and brain plasticity.

RESULTS

While the MRI, DTI and neuropsychological evaluations showed no abnormalities, neurophysiologic tests revealed subclinical abnormalities in our patient: (1) Significantly higher intracortical facilitation than the control group at both time points; (2) Intracortical inhibition presumably mediated by GABAB receptors was absent at week 2, but returned to normal value at week 6; (3) Abnormal mechanisms of plasticity at week 2, that normalize at week 6.

CONCLUSIONS

These findings demonstrate a transient alteration of brain cortical physiology following concussion independent of anatomical findings and neuropsychological function. This case study suggests that TMS measures may serve as sensitive biomarkers of physiologic brain abnormalities after concussion.

Metabolic changes in concussed American football players during the acute and chronic post-injury phases

Background

Despite negative neuroimaging findings many athletes display neurophysiological alterations and post-concussion symptoms that may be attributable to neurometabolic alterations.

Methods

The present study investigated the effects of sports concussion on brain metabolism using ¹H-MR Spectroscopy by comparing a group of 10 non-concussed athletes with a group of 10 concussed athletes of the same age (mean: 22.5 years) and education (mean: 16 years) within both the acute and chronic post-injury phases. All athletes were scanned 1-6 days post-concussion and again 6-months later in a 3T Siemens MRI.

Results

Concussed athletes demonstrated neurometabolic impairment in prefrontal and motor (M1) cortices in the acute phase where NAA:Cr levels remained depressed relative to controls. There was some recovery observed in the chronic phase where Glu:Cr levels returned to those of control athletes; however, there was a pathological increase of m-I:Cr levels in M1 that was only present in the chronic phase.

Conclusions

These results confirm cortical neurometabolic changes in the acute post-concussion phase as well as recovery and continued metabolic abnormalities in the chronic phase. The results indicate that complex pathophysiological processes differ depending on the post-injury phase and the neurometabolite in question.

Cerebrovascular pathophysiology following mild traumatic brain injury

Mild traumatic brain injury (mTBI) or sport-induced concussion has recently become a prominent concern not only in the athletic setting (i.e. sports venue) but also in the general population. The majority of research to date has aimed at understanding the neurological and neuropsychological outcomes of injury as well as return-to-play guidelines. Remaining relatively unexamined has been the pathophysiological aspect of mTBI. Recent technological advances including transcranial Doppler ultrasound and near infrared spectroscopy have allowed researchers to examine the systemic effects of mTBI from rest to exercise, and during both asymptomatic and symptomatic conditions. In this review, we focus on the current research available from both human and experimental (animal) studies surrounding the pathophysiology of mTBI. First, the quest for a unified definition of mTBI, its historical development and implications for future research is discussed. Finally, the impact of mTBI on the control and regulation of cerebral blood flow, cerebrovascular reactivity, cerebral oxygenation and neuroautonomic cardiovascular regulation, all of which may be compromised with mTBI, is discussed.

Boxing-related head injuries

Fatalities in boxing are most often due to traumatic brain injury that occurs in the ring. In the past 30 years, significant improvements in ringside and medical equipment, safety, and regulations have resulted in a dramatic reduction in the fatality rate. Nonetheless, the rate of boxing-related head injuries, particularly concussions, remains unknown, due in large part to its variability in clinical presentation. Furthermore, the significance of repeat concussions sustained when boxing is just now being understood. In this article, we identify the clinical manifestations, pathophysiology, and management of boxing-related head injuries, and discuss preventive strategies to reduce head injuries sustained by boxers.

Brain functions after sports-related concussion: insights from event-related potentials and functional MRI

The high incidence of concussions in contact sports and their impact on brain functions are a major cause for concern. To improve our understanding of brain functioning after sports-related concussion, advanced functional assessment techniques, namely event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), have been recently used in research studies. Contrary to neuropsychological tests that measure verbal and/or motor responses, ERPs and fMRI assess the neural activities associated with cognitive/behavioral demands, and thus provide access to better comprehension of brain functioning. In fact, ERPs have excellent temporal resolution, and fMRI identifies the involved structures during a task. This article describes ERP and fMRI techniques and reviews the results obtained with these tools in sports-related concussion. Although these techniques are not yet readily available, they offer a unique clinical approach, particularly for complex cases (ie, athletes with multiple concussions, chronic symptoms) and objective measures that provide valuable information to guide management and return-to-play decision making.

Return-to-play in sport: a decision-based model

OBJECTIVE

Return-to-play (RTP) decisions are fundamental to the practice of sports medicine but vary greatly for the same medical condition and circumstance. Although there are published articles that identify individual components that go into these decisions, there exists neither quantitative criteria nor a model for the sequence or weighting of these components within the medical decision-making process. Our objective was to develop a decision-based model for clinical use by sports medicine practitioners.

DATA SOURCES

English literature related to RTP decision making.

MAIN RESULTS

We developed a 3-step decision-based RTP model for an injury or illness that is specific to the individual practitioner making the RTP decision: health status, participation risk, and decision modification. In Step 1, the Health Status of the athlete is assessed through the evaluation of Medical Factors related to how much healing has occurred. In Step 2, the clinician evaluates the Participation Risk associated with participation, which is informed by not only the current health status but also by the Sport Risk Modifiers (eg, ability to protect the injury with padding, athlete position). Different individuals are expected to have different thresholds for "acceptable level of risk," and these thresholds will change based on context. In Step 3, Decision Modifiers are considered and the decision to RTP or not is made.

CONCLUSIONS

Our model helps clarify the processes that clinicians use consciously and subconsciously when making RTP decisions. Providing such a structure should decrease controversy, assist physicians, and identify important gaps in practice areas where research evidence is lacking.

Fluid-percussion-induced traumatic brain injury model in rats

Traumatic brain injury (TBI) is a major cause of mortality and morbidity. Various attempts have been made to replicate clinical TBI using animal models. The fluid-percussion model (FP) is one of the oldest and most commonly used models of experimentally induced TBI. Both central (CFP) and lateral (LFP) variations of the model have been used. Developed initially for use in larger species, the standard FP device was adapted more than 20 years ago to induce consistent degrees of brain injury in rodents. Recently, we developed a microprocessor-controlled, pneumatically driven instrument, micro-FP (MFP), to address operational concerns associated with the use of the standard FP device in rodents. We have characterized the MFP model with regard to injury severity according to behavioral and histological outcomes. In this protocol, we review the FP models and detail surgical procedures for LFP. The surgery involves tracheal intubation, craniotomy and fixation of Luer fittings, and induction of injury. The surgical procedure can be performed within 45-50 min.

Sport-related concussion in adolescents

Sport-related concussion is a common problem encountered by pediatricians and other primary care physicians. Assessment of concussion is based on clinical evaluation. The Zurich consensus statement provides a basic framework to guide concussion management decisions and recommends an individualized approach and the exercising of clinical judgment in return-to-play decisions. This article reviews practice aspects of concussion for the adolescent athletes who present in the primary care office or clinic setting.