Consensus statement on concussion in sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008

From Concussion to Chronic Traumatic Encephalopathy: A Review

Sports-related activities account for an estimated 10% of head and spinal cord injuries. In recent years, concussion in particular has garnered more interest in the medical field as well as the media. Reports of athletes suffering from long-term cognitive deficits and Parkinsonian symptoms have sparked concern in a disease process that has often been underestimated or ignored. As more reports surface, the desperate need for a better understanding of the neuropathology has been made clear. In addition to the concern for acute injury, long-term sequelae such as chronic traumatic encephalopathy (CTE) are feared consequences of concussive injuries. Research studies have shown significant overlap in the neuropathology between CTE and chronic neurodegenerative processes such as Alzheimer’s disease (AD). In particular, tau protein deposition has been found to be present in both disease processes and may play an important part in the clinical findings observed. The present review discusses concussion and our current understanding of pathological findings that may underlie the clinical features associated with concussive injuries and resulting chronic traumatic encephalopathy.

The utility of post-concussion neuropsychological data in identifying cognitive change following sports-related MTBI in the absence of baseline data

Neuropsychological tests have become commonplace in the assessment of sports-related concussion. Typically, post-injury test data are compared to pre-injury "baselines." Baseline testing can be expensive and logistically challenging, yet the usefulness of neuropsychological baseline testing has not been tested empirically. This paper examines the extent to which baseline testing is useful for detecting neurocognitive deficits following sports concussion in a college-age population. A total of 223 collegiate athletes from multiple sports who sustained concussions and had both baseline and post-injury testing using Immediate Post-concussion Assessment and Cognitive Testing (ImPACT) were included in the study. Reliable change (RC) in scores was determined by two approaches, the Jacobson and Truax (JT) and the Gulliksen-Lord-Novick (GLN) methods. The 90% confidence interval was used for both. Classification using these methods was compared to standard normative methods that compared post-concussion performance to baseline population means. Agreement between reliable change and normative methods was examined using Cohen's Kappa scores to determine whether post-injury scores alone could identify reliable cognitive decline. Mean time from concussion to post-injury testing was 3.40 days. The percentage of athletes who declined when using the JT method was similar to the percentage that would be expected to decline due to chance alone. Although the GLN and JT methods demonstrated moderate to substantial agreement, the GLN method consistently identified more cognitively compromised athletes than the JT method. Post-injury scores alone identified a significant majority of athletes with a reliable decline on ImPACT. Although preliminary and in need of replication across age groups and instruments, these findings suggest that the majority of collegiate athletes who experience clinically meaningful post-concussion cognitive decline can be identified without baseline data.

Biomechanical correlates of symptomatic and asymptomatic neurophysiological impairment in high school football

Concussion is a growing public health issue in the United States, and chronic traumatic encephalopathy (CTE) is the chief long-term concern linked to repeated concussions. Recently, attention has shifted toward subconcussive blows and the role they may play in the development of CTE. We recruited a cohort of high school football players for two seasons of observation. Acceleration sensors were placed in the helmets, and all contact activity was monitored. Pre-season computer-based neuropsychological tests and functional magnetic resonance imaging (fMRI) tests were also obtained in order to assess cognitive and neurophysiological health. In-season follow-up scans were then obtained both from individuals who had sustained a clinically-diagnosed concussion and those who had not. These changes were then related through stepwise regression to history of blows recorded throughout the football season up to the date of the scan. In addition to those subjects who had sustained a concussion, a substantial portion of our cohort who did not sustain concussions showed significant neurophysiological changes. Stepwise regression indicated significant relationships between the number of blows sustained by a subject and the ensuing neurophysiological change. Our findings reinforce the hypothesis that the effects of repetitive blows to the head are cumulative and that repeated exposure to subconcussive blows is connected to pathologically altered neurophysiology.

Persistent motor system abnormalities in formerly concussed athletes

CONTEXT

The known detrimental effects of sport concussions on motor system function include balance problems, slowed motor execution, and abnormal motor cortex excitability.

OBJECTIVE

To assess whether these concussion-related alterations of motor system function are still evident in collegiate football players who sustained concussions but returned to competition more than 9 months before testing.

DESIGN

Case-control study.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

A group of 21 active, university-level football players who had experienced concussions was compared with 15 university football players who had not sustained concussions.

INTERVENTION(S)

A force platform was used to assess center-of-pressure (COP) displacement and COP oscillation regularity (approximate entropy) as measures of postural stability in the upright position. A rapid alternating-movement task was also used to assess motor execution speed. Transcranial magnetic stimulation over the motor cortex was used to measure long-interval intracortical inhibition and the cortical silent period, presumably reflecting y-aminobutyric acid subtype B receptor-mediated intracortical inhibition.

MAIN OUTCOME MEASURE(S)

COP displacement and oscillation regularity, motor execution speed, long-interval intracortical inhibition, cortical silent period.

RESULTS

Relative to controls, previously concussed athletes showed persistently lower COP oscillation randomness, normal performance on a rapid alternating-movement task, and more M1 intracortical inhibition that was related to the number of previous concussions.

CONCLUSIONS

Sport concussions were associated with pervasive changes in postural control and more M1 intracortical inhibition, providing neurophysiologic and behavioral evidence of lasting, subclinical changes in motor system integrity in concussed athletes.

Increased QT interval variability in 3 recently concussed athletes: an exploratory observation

CONTEXT

The QT interval variability index (QTVI) is a noninvasive measure of beat-to-beat fluctuations of the QT interval as seen from a single electrocardiographic lead. It represents the relationship between the respective variabilities of the QT and R-R intervals. Recently, the QTVI was demonstrated to be an index of vagal cardiac autonomic modulation in resting conditions.

OBJECTIVE

To determine whether QTVI varied in athletes at 48 hours, 1 week, and 2 weeks after a concussive head injury.

DESIGN

Case series.

SETTING

Testing facility.

PATIENTS OR OTHER PARTICIPANTS

Three athletes with recent concussions and 3 uninjured athletes with similar demographic factors.

MAIN OUTCOME MEASURE(S)

Continuous 3-lead electrocardiograms were obtained in a seated, resting position over 2 successive weeks. Separate, unpaired t tests were performed to determine whether group-visit differences were present in the QTVI at 48 hours, 1 week, or 2 weeks.

RESULTS

No demographic differences were present between groups. At 48 hours, the QTVI was greater in the concussion group than in the matched controls. At weeks 1 and 2, the QTVI in the concussion group was lower than at 48 hours and not different from that of the control group.

CONCLUSIONS

Vagal cardiac autonomic modulation, as quantified by the QTVI, appeared to be negatively affected in concussed athletes within 48 hours of injury, resolved within 1 week, and remained at control group levels 2 weeks later. Serial assessments of QTVI may be of clinical utility in identifying suspected cases of acute concussion and may provide helpful information for determining when an athlete can return to play safely.

Computerized neurocognitive testing for the management of sport-related concussions

OBJECTIVES

To describe the prevalence of computerized neurocognitive testing for the assessment of high school athletes who sustain concussions, and to describe associations between using computerized neurocognitive tests, timing of return-to-play, and medical provider managing the athlete.

METHODS

Concussions recorded in the High School Reporting Information Online injury surveillance system during the 2009-2010 academic year were included. Measures of association between use of computerized neurocognitive testing and outcomes were analyzed. A questionnaire was sent to athletic trainers (ATs) querying the use of computerized neurocognitive testing. χ(2) analyses were conducted for categorical variables. Logistic regression analyses were used to adjust for potential confounders. Statistical significance was set at P < .05.

RESULTS

High School Reporting Information Online recorded 1056 concussions. Athletes who underwent computerized neurocognitive testing were less likely to be returned to play within 10 days of injury (38.5% vs 55.7%, P < .001) and more likely to be returned to play by a physician (60.9% vs 45.6%, P < .001). We had a response rate of 97.3% for the survey. Of respondents, 39.9% used computerized neurocognitive testing; 93.0% of those used ImPACT. Tests were most often interpreted by ATs (78.9%) and/or physicians (78.8%), as opposed to neuropsychologists (16.9%).

CONCLUSIONS

Approximately 40% of US high schools that employ an AT use computerized neurocognitive tests when managing sport-related concussions. Tests are most often interpreted by ATs and physicians, as opposed to neuropsychologists. Computerized neurocognitive tests are significantly associated with the timing of return-to-play.

National athletic trainers' association position statement: preventing sudden death in sports

OBJECTIVE

To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.

BACKGROUND

Cardiac conditions, head injuries, neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.

Pediatric sports-related concussion

This article aims to examine pediatric concussion literature with respect to epidemiology, etiology, return to play, and recurrent concussions, and to provide recommendations for future research. We conducted a review of pediatric concussion literature regarding incidence, etiology, return to play, and recurrent concussive injury by using MEDLINE, CINAHL, Sport-Discus, and PsychInfo databases from 1995-2010. A review of reference lists in the aforementioned articles was also performed. We discovered that the research on sports-related concussion specific to children and adolescents is rather limited. Results of existing studies of concussion incidence in this population indicate that concussion is relatively rare compared with most musculoskeletal injuries; however, the potential consequences of mismanagement and of subsequent injury warrant significant attention regarding injury recognition and recovery, and the challenge of determining readiness to return to play. Evidence exists that children and adolescents take longer to recover than adults after a concussion, which underscores the need for a more conservative approach to management and return to physical and cognitive activities. Concussion in the young athlete is of specific concern because of the continuing cognitive maturation, therefore, the recovery may be more difficult to track when using the standard assessment tools currently available. Until future studies can better delineate the mechanisms of, response to, and recovery from concussion in the young athlete, it is prudent to act in a conservative manner when dealing with pediatric athletes with concussion.

One-year test-retest reliability of the online version of ImPACT in high school athletes

BACKGROUND

The ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive testing battery is a popular assessment tool used for concussion management. The stability of the baseline neurocognitive assessment is important for accurate comparisons between postconcussion and baseline neurocognitive performance. Psychometric properties of the recently released online version of ImPACT have yet to be established; therefore, research evaluating the reliability of this measure is warranted.

PURPOSE

The authors investigated the 1-year test-retest reliability of the ImPACT online version in a sample of high school athletes.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 369 varsity high school athletes completed 2 mandatory preseason baseline cognitive assessments approximately 1 year apart as required by their respective athletics program. No diagnosed concussion occurred between assessments.

RESULTS

Intraclass correlation coefficients (ICCs) for ImPACT online indicated that motor processing speed (.85) was the most stable composite score, followed by reaction time (.76), visual memory (.70), and verbal memory (.62). Unbiased estimates of reliability were consistent with ICCs: motor processing speed (.85), reaction time (.76), visual memory (.71), and verbal memory (.62).

CONCLUSION

The online ImPACT baseline is a stable measure of neurocognitive performance across a 1-year time period for high school athletes. These reliability data for online ImPACT are higher than the 2-year ICCs previously reported from the desktop version.

CLINICAL RELEVANCE

It is recommended that the ImPACT baseline assessment (both desktop and online) continue to be updated every 2 years. The online version of ImPACT appears to be a stable measure of neurocognitive performance over a 1-year period, and systematic evaluation of its stability over a 2-year period is warranted.

Balance performance with a cognitive task: a continuation of the dual-task testing paradigm

CONTEXT

To ensure that concussed athletes return to play safely, we need better methods of measuring concussion severity and monitoring concussion resolution.

OBJECTIVE

To develop a dual-task model that assesses postural stability and cognitive processing in concussed athletes.

DESIGN

Repeated measures study.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty healthy, college-aged students (10 men, 10 women; age  =  20 ± 1.86 years, height  =  173 ± 4.10 cm, mass  =  71.83 + 35.77 kg).

INTERVENTION(S)

Participants were tested individually in 2 sessions separated by 2 days. In one session, a balance task and a cognitive task were performed separately. In the other session, the balance and cognitive tasks were performed concurrently. The balance task consisted of 6 conditions of the Sensory Organization Test performed on the NeuroCom Smart Balance Master. The cognitive task consisted of an auditory switch task (3 trials per condition, 60 seconds per trial).

MAIN OUTCOME MEASURE(S)

For the balance test, scores for each Sensory Organization Test condition; the visual, vestibular, somatosensory, and visual-conflict subscores; and the composite balance score were calculated. For the cognitive task, response time and accuracy were measured.

RESULTS

Balance improved during 2 dual-task conditions: fixed support and fixed visual reference (t18  =  -2.34, P < .05) and fixed support and sway visual reference (t18  =  -2.72, P  =  .014). Participants' response times were longer (F1,18  =  67.77, P < .001, η2  =  0.79) and choice errors were more numerous under dual-task conditions than under single-task conditions (F1,18  =  5.58, P  =  .03, η2  =  0.24). However, differences were observed only during category-switch trials.

CONCLUSIONS

Balance was either maintained or improved under dual-task conditions. Thus, postural control took priority over cognitive processing when the tasks were performed concurrently. Furthermore, dual-task conditions can isolate specific mental processes that may be useful for evaluating concussed individuals.

Shannon and Renyi entropies to classify effects of Mild Traumatic Brain Injury on postural sway

Background

Mild Traumatic Brain Injury (mTBI) has been identified as a major public and military health concern both in the United States and worldwide. Characterizing the effects of mTBI on postural sway could be an important tool for assessing recovery from the injury.

Methodology/Principal Findings

We assess postural sway by motion of the center of pressure (COP). Methods for data reduction include calculation of area of COP and fractal analysis of COP motion time courses. We found that fractal scaling appears applicable to sway power above about 0.5 Hz, thus fractal characterization is only quantifying the secondary effects (a small fraction of total power) in the sway time series, and is not effective in quantifying long-term effects of mTBI on postural sway. We also found that the area of COP sensitively depends on the length of data series over which the COP is obtained. These weaknesses motivated us to use instead Shannon and Renyi entropies to assess postural instability following mTBI. These entropy measures have a number of appealing properties, including capacity for determination of the optimal length of the time series for analysis and a new interpretation of the area of COP.

Conclusions

Entropy analysis can readily detect postural instability in athletes at least 10 days post-concussion so that it appears promising as a sensitive measure of effects of mTBI on postural sway.

Availability

The programs for analyses may be obtained from the authors.

Differences in change scores and the predictive validity of three commonly used measures following concussion in the middle school and high school aged population

BACKGROUND

A battery of tests is commonly used to measure disability with and recovery from concussion. A number of different concussion-oriented assessment tests exist and each is considered useful. To the authors' knowledge, no study has compared the scores of these tests during recovery in the middle school and high school aged population to see how each change over time.

PURPOSE

The purposes of this study were to analyze clinical data of concussed middle school and high school aged athletes to determine the concurrent and predictive validity for post-concussion syndrome (PCS) of the Post-Concussion Symptom Scale (PCSS), Balance Error Scoring System (BESS), and the five subscales of the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT).

METHODS

The study was a retrospective chart review performed on middle school and high school aged individuals with a diagnosis of concussion from the years 2008-2010 within the Akron Children's Hospital Sports Medicine system. To be eligible for inclusion in the dataset, each subject required a baseline measurement for each of the three tests (and all five subscales of the ImPACT) and a post-test measure. The mean age of the population was 15.38 years (SD = 1.7) and ranged from 11 to 19 years. Pearson product correlation tests (correlation matrix) were used to analyze the concurrent validity of the test items during recovery following a concussion. Receiver operating characteristics (ROC) curves were used to determine the predictive validity of initial scores for developing PCS.

RESULTS

The correlation matrix captured five statistically significant findings; however, these suggested only weak to mild correlations. Five test items yielded an area under the curve (AUC) greater than 0.50 but only one was statistically significant. After qualitative evaluation, only one of the three tests (including the five subscales of the ImPACT) was useful in predicting post-concussion syndrome.

CONCLUSION

This study suggests that there is poor concurrent validity among three commonly used concussion tests and there is no baseline score that predicts whether post-concussion syndrome will occur.

LEVEL OF EVIDENCE

2b.

Head impact exposure in collegiate football players

In American football, impacts to the helmet and the resulting head accelerations are the primary cause of concussion injury and potentially chronic brain injury. The purpose of this study was to quantify exposures to impacts to the head (frequency, location and magnitude) for individual collegiate football players and to investigate differences in head impact exposure by player position. A total of 314 players were enrolled at three institutions and 286,636 head impacts were recorded over three seasons. The 95th percentile peak linear and rotational acceleration and HITsp (a composite severity measure) were 62.7g, 4378rad/s(2) and 32.6, respectively. These exposure measures as well as the frequency of impacts varied significantly by player position and by helmet impact location. Running backs (RB) and quarter backs (QB) received the greatest magnitude head impacts, while defensive line (DL), offensive line (OL) and line backers (LB) received the most frequent head impacts (more than twice as many than any other position). Impacts to the top of the helmet had the lowest peak rotational acceleration (2387rad/s(2)), but the greatest peak linear acceleration (72.4g), and were the least frequent of all locations (13.7%) among all positions. OL and QB had the highest (49.2%) and the lowest (23.7%) frequency, respectively, of front impacts. QB received the greatest magnitude (70.8g and 5428rad/s(2)) and the most frequent (44% and 38.9%) impacts to the back of the helmet. This study quantified head impact exposure in collegiate football, providing data that is critical to advancing the understanding of the biomechanics of concussive injuries and sub-concussive head impacts.

Magnitude of head impact exposures in individual collegiate football players

The purpose of this study was to quantify the severity of head impacts sustained by individual collegiate football players and to investigate differences between impacts sustained during practice and game sessions, as well as by player position and impact location. Head impacts (N = 184,358) were analyzed for 254 collegiate players at three collegiate institutions. In practice, the 50th and 95th percentile values for individual players were 20.0 g and 49.5 g for peak linear acceleration, 1187 rad/s2 and 3147 rad/s2 for peak rotational acceleration, and 13.4 and 29.9 for HITsp, respectively. Only the 95th percentile HITsp increased significantly in games compared with practices (8.4%, p = .0002). Player position and impact location were the largest factors associated with differences in head impacts. Running backs consistently sustained the greatest impact magnitudes. Peak linear accelerations were greatest for impacts to the top of the helmet, whereas rotational accelerations were greatest for impacts to the front and back. The findings of this study provide essential data for future investigations that aim to establish the correlations between head impact exposure, acute brain injury, and long-term cognitive deficits.

Altered bidirectional plasticity and reduced implicit motor learning in concussed athletes

Persistent motor/cognitive alterations and increased prevalence of Alzheimer's disease are known consequences of recurrent sports concussions, the most prevalent cause of mild traumatic brain injury (TBI) among youth. Animal models of TBI demonstrated that impaired learning was related to persistent synaptic plasticity suppression in the form of long-term potentiation (LTP) and depression (LTD). In humans, single and repeated concussive injuries lead to lifelong and cumulative enhancements of gamma-aminobutyric acid (GABA)-mediated inhibition, which is known to suppress LTP/LTD plasticity. To test the hypothesis that increased GABAergic inhibition after repeated concussions suppresses LTP/LTD and contributes to learning impairments, we used a paired associative stimulation (PAS) protocol to induce LTP/LTD-like effects in primary motor cortex (M1) jointly with an implicit motor learning task (serial reaction time task, SRTT). Our results indicate that repeated concussions induced persistent elevations of GABA(B)-mediated intracortical inhibition in M1, which was associated with suppressed PAS-induced LTP/LTD-like synaptic plasticity. This synaptic plasticity suppression was related to reduced implicit motor learning on the SRTT task relative to normal LTP/LTD-like synaptic plasticity in unconcussed teammates. These findings identify GABA neurotransmission alterations after repeated concussions and suggest that impaired learning after multiple concussions could at least partly be related to compromised GABA-dependent LTP/LTD synaptic plasticity.

Medical therapies for concussion

Clinicians who manage sport-related concussions have excellent guidelines by which most injuries can be managed. Because sport-related concussions typically resolve within a short time frame, most can be managed with physical and cognitive rest alone. However, clinicians who specialize in the assessment and management of this diagnosis encounter patients with prolonged recovery courses, persistent symptoms, and significant deficits in cognitive functioning. These patients require more involved therapy, which may include additional education, academic accommodations, physical therapy, cognitive rehabilitation, and medication. This article reviews the main medical therapies for the management of concussive brain injury.

The pediatric athlete: younger athletes with sport-related concussion

Although much of the lay media attention surrounding sport-related concussion (SRC) focuses on professional athletes, SRC is a common injury in pediatric sports. The anatomy, biomechanics, and response to injury of the developing pediatric brain differ from those of the adult. Similarly, the neurocognitive abilities of the child are developing more rapidly than in an adult. The effects of concussive brain injury on the life of a child are different from those of an adult. This article focuses on the aspects of SRC that are specific to the younger athletes.

High school concussions in the 2008-2009 academic year: mechanism, symptoms, and management

BACKGROUND

An estimated 136 000 concussions occur per academic year in high schools alone. The effects of repetitive concussions and the potential for catastrophic injury have made concussion an injury of significant concern for young athletes.

PURPOSE

The objective of this study was to describe the mechanism of injury, symptoms, and management of sport-related concussions using the High School Reporting Information Online (HS RIO) surveillance system.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

All concussions recorded by HS RIO during the 2008-2009 academic year were included. Analyses were performed using SPSS software. Chi-square analysis was performed for all categorical variables. Statistical significance was considered for P < .05.

RESULTS

A total of 544 concussions were recorded. The most common mechanism (76.2%) was contact with another player, usually a head-to-head collision (52.7%). Headache was experienced in 93.4%; 4.6% lost consciousness. Most (83.4%) had resolution of their symptoms within 1 week. Symptoms lasted longer than 1 month in 1.5%. Computerized neuropsychological testing was used in 25.7% of concussions. When neuropsychological testing was used, athletes were less likely to return to play within 1 week than those for whom it was not used (13.6% vs 32.9%; P < .01). Athletes who had neuropsychological testing appeared less likely to return to play on the same day (0.8% vs 4.2%; P = .056). A greater proportion of injured, nonfootball athletes had computerized neuropsychological testing than injured football players (23% vs 32%; P = .02)

CONCLUSION

When computerized neuropsychological testing is used, high school athletes are less likely to be returned to play within 1 week of their injury. Concussed football players are less likely to have computerized neuropsychological testing than those participating in other sports. Loss of consciousness is relatively uncommon among high school athletes who sustain a sport-related concussion. The most common mechanism is contact with another player. Some athletes (1.5%) report symptoms lasting longer than 1 month.

Pediatric concussions in United States emergency departments in the years 2002 to 2006

OBJECTIVES

To estimate the incidence and demographics of concussions in children coming to emergency departments (EDs) in the United States and describe the rates of neuroimaging and follow-up instructions in these patients.

STUDY DESIGN

This is a cross-sectional study of children 0 to 19 years old diagnosed with concussion from the National Hospital Ambulatory Medical Care Survey. National Hospital Ambulatory Medical Care Survey collects data on approximately 25,000 visits annually to 600 randomly selected hospital emergency and outpatient departments. We examined visits to United States emergency departments between 2002 and 2006. Simple descriptive statistics were used.

RESULTS

Of the 50,835 pediatric visits in the 5-year sample, 230 observations, representing 144,000 visits annually, were for concussions. Sixty-nine percent of concussion visits were by males. Thirty percent were sports-related. Sixty-nine percent of patients diagnosed with a concussion had head imaging. Twenty-eight percent of patients were discharged without specific instructions to follow-up with an outpatient provider for further treatment.

CONCLUSIONS

Approximately 144,000 pediatric patients present to emergency departments each year with a concussion. Most of these patients undergo computed tomography of the head, and nearly one-third are discharged without specific instructions to follow-up with an outpatient provider for further treatment.