Lack of long-term fMRI differences after multiple sports-related concussions

On the lasting impact of mild traumatic brain injury on working memory: Behavioural and electrophysiological evidence

Despite increasing recognition of the significance of mild traumatic brain injury (mTBI), the long-term cognitive consequences of the injury remain unclear. More sensitive measures that can detect subtle cognitive changes and consideration of individual variability are needed to properly characterise cognitive outcomes following mTBI. Here, we used complex behavioural tasks, individual differences approaches, and electrophysiology to investigate the long-term cognitive effects of a history of mTBI. In Experiment 1, participants with self-reported mTBI history (n=82) showed poorer verbal working memory performance on the operation span task compared to control participants (n=88), but there were no group differences in visual working memory, multitasking, cognitive flexibility, attentional control, visuospatial ability, or information processing speed. Individual differences analyses revealed that time since injury and presence of memory loss predicted visual working memory capacity and visuospatial ability, respectively, in those with mTBI history. In Experiment 2, participants with mTBI history (n=20) again demonstrated poorer verbal working memory on the operation span task compared to control participants (n=38), but no group differences were revealed on a visuospatial complex span task or simpler visual working memory measures. We also explored the electrophysiological indices of visual working memory using EEG during a change detection task. No differences were observed in early sensory event-related potentials (P1, N1) or the later negative slow wave associated with visual working memory capacity. Together, these findings suggest that mTBI history may be associated with a lasting, isolated disruption in the subsystem underlying verbal working memory storage. The results emphasise the importance of sensitive cognitive measures and accounting for individual variability in injury characteristics when assessing mTBI outcomes.

Not All Stroop-Type Tasks Are Alike: Assessing the Impact of Stimulus Material, Task Design, and Cognitive Demand via Meta-analyses Across Neuroimaging Studies

The Stroop effect is one of the most often studied examples of cognitive conflict processing. Over time, many variants of the classic Stroop task were used, including versions with different stimulus material, control conditions, presentation design, and combinations with additional cognitive demands. The neural and behavioral impact of this experimental variety, however, has never been systematically assessed. We used activation likelihood meta-analysis to summarize neuroimaging findings with Stroop-type tasks and to investigate whether involvement of the multiple-demand network (anterior insula, lateral frontal cortex, intraparietal sulcus, superior/inferior parietal lobules, midcingulate cortex, and pre-supplementary motor area) can be attributed to resolving some higher-order conflict that all of the tasks have in common, or if aspects that vary between task versions lead to specialization within this network. Across 133 neuroimaging experiments, incongruence processing in the color-word Stroop variant consistently recruited regions of the multiple-demand network, with modulation of spatial convergence by task variants. In addition, the neural patterns related to solving Stroop-like interference differed between versions of the task that use different stimulus material, with the only overlap between color-word, emotional picture-word, and other types of stimulus material in the posterior medial frontal cortex and right anterior insula. Follow-up analyses on behavior reported in these studies (in total 164 effect sizes) revealed only little impact of task variations on the mean effect size of reaction time. These results suggest qualitative processing differences among the family of Stroop variants, despite similar task difficulty levels, and should carefully be considered when planning or interpreting Stroop-type neuroimaging experiments.

The impact of mild traumatic brain injury on reading comprehension and eye movements: preliminary results

INTRODUCTION

Individuals who sustain a mild traumatic brain injury (mTBI) can suffer from executive function, working memory, and attention deficits, which can impact functional task performance, including reading comprehension. Individuals with mTBI commonly report reading difficulties, but such difficulties have been historically difficult to capture using behavioral measures. The current study examined reading performance in those with and without mTBI using eye-tracking measures, which may be more sensitive to reading impairment in mTBI.

METHOD/RESULTS

In Experiment 1, 26 participants with a history of mTBI and 26 healthy control participants completed working memory (WM) and reading comprehension tasks. We found no differences in behavioral measures but found that spontaneous eye-blinking frequency was lower during the reading task in the mTBI group. In Experiment 2, we explored the impact of auditory distraction (e.g., multi-talker babble) on reading and memory performance. Twenty-three new participants with a history of mTBI and 26 healthy control participants completed a short-term memory (STM) task, a WM task, and a reading comprehension task under two distraction conditions. As in Experiment 1, we found no differences on behavioral measures, but observed significant differences on spontaneous eye-blinking frequency between those with and without mTBI. Group differences in distraction effects were also observed and performance on the WM task predicted reading comprehension performance.

CONCLUSIONS

The lack of differences on behavioral measures between groups, but lower frequencies of spontaneous eye blinking in the mTBI group suggests that while these individuals successfully completed the reading comprehension task, they may require more cognitive resources to do so.

Neurophysiological Biomarkers of Persistent Post-concussive Symptoms: A Scoping Review

Background and Objectives: Persistent post-concussive symptoms (PCS) consist of neurologic and psychological complaints persisting after a mild traumatic brain injury (mTBI). It affects up to 50% of mTBI patients, may cause long-term disability, and reduce patients' quality of life. The aim of this review was to examine the possible use of different neuroimaging modalities in PCS. Methods: Articles from Pubmed database were screened to extract studies that investigated the relationship between any neuroimaging features and symptoms of PCS. Descriptive statistics were applied to report the results. Results: A total of 80 out of 939 papers were included in the final review. Ten examined conventional MRI (30% positive finding), 24 examined diffusion weighted imaging (54.17% positive finding), 23 examined functional MRI (82.61% positive finding), nine examined electro(magneto)encephalography (77.78% positive finding), and 14 examined other techniques (71% positive finding). Conclusion: MRI was the most widely used technique, while functional techniques seem to be the most sensitive tools to evaluate PCS. The common functional patterns associated with symptoms of PCS were a decreased anti-correlation between the default mode network and the task positive network and reduced brain activity in specific areas (most often in the prefrontal cortex). Significance: Our findings highlight the importance to use functional approaches which demonstrated a functional alteration in brain connectivity and activity in most studies assessing PCS.

A Systematic Review of Cognitive Functioning After Traumatic Brain Injury in Individuals Aged 10-30 Years

Given the importance of the period of life from 10 to 30 years in terms of cognitive development and education, combined with the high incidence of traumatic brain injury (TBI) during this period, and limited consensus as to the pattern and degree of cognitive impairment post TBI during this period, we conducted a systematic review to investigate cognitive performance across a range of domains among individuals between the ages of 10 and 30 years who had sustained a TBI. We searched five databases and identified 799 unique records; 52 met our inclusion criteria. These studies reported cognitive function for intelligence, attention, memory, processing speed, and executive function. The majority of the studies reported significant effects, suggesting that TBI is associated with cognitive impairments in these domains. Nine of the studies used physiological tests (EEG and fMRI), the outcomes of which supported behaviorally demonstrated cognitive deficits. In the studies we reviewed, individuals aged 10-30 years who had experienced a TBI performed worse than healthy controls on cognitive function measures-specifically for attention, memory, processing speed, and executive function. In the studies that subjected the individuals with TBI to EEG and fMRI, atypical activation in associated brain regions was demonstrated while the individuals were undergoing cognitive tasks. However, caution should be taken when interpreting the overall results due to the high risk of bias across the majority of the studies. The broader implications of reduced cognitive performance after TBI across this age range are yet to be fully understood.

Scale-free functional brain dynamics during recovery from sport-related concussion

Studies using blood‐oxygenation‐level‐dependent functional magnetic resonance imaging (BOLD fMRI) have characterized how the resting brain is affected by concussion. The literature to date, however, has largely focused on measuring changes in the spatial organization of functional brain networks. In the present study, changes in the temporal dynamics of BOLD signals are examined throughout concussion recovery using scaling (or fractal) analysis. Imaging data were collected for 228 university‐level athletes, 61 with concussion and 167 athletic controls. Concussed athletes were scanned at the acute phase of injury (1–7 days postinjury), the subacute phase (8–14 days postinjury), medical clearance to return to sport (RTS), 1 month post‐RTS and 1 year post‐RTS. The wavelet leader multifractal approach was used to assess scaling (c₁) and multifractal (c₂) behavior. Significant longitudinal changes were identified for c₁, which was lowest at acute injury, became significantly elevated at RTS, and returned near control levels by 1 year post‐RTS. No longitudinal changes were identified for c₂. Secondary analyses showed that clinical measures of acute symptom severity and time to RTP were related to longitudinal changes in c₁. Athletes with both higher symptoms and prolonged recovery had elevated c₁ values at RTS, while athletes with higher symptoms but rapid recovery had reduced c₁ at acute injury. This study provides the first evidence for long‐term recovery of BOLD scale‐free brain dynamics after a concussion.

Characterizing the Link Between Glial Activation and Changed Functional Connectivity in National Football League Players Using Multimodal Neuroimaging

OBJECTIVE

The primary objective of this preliminary study was to examine the impact of NFL play on interregional functional connectivity between two brain regions, the supramarginal gyrus (SMG) and the thalamus, identified as having higher binding of [¹¹C]DPA-713 in NFL players. The authors' secondary objective was to examine the effect of years since play on the interregional connectivity.

METHODS

Resting-state functional MRI was used to examine functional brain changes between regions with evidence of past injury in active or recently retired NFL players (defined as ≤12 years since NFL play) and distantly retired players (defined as >12 years since NFL play). Age-comparable individuals without a history of concussion or participation in collegiate or professional collision sports were included as a control group.

RESULTS

Compared with healthy control subjects, NFL players showed a loss of anticorrelation between the left SMG and bilateral thalami (mean z score=-2.434, p=0.015). No difference was observed when examining right SMG connectivity. The pattern of connectivity in active and recently retired players mimicked the pattern observed in distantly retired players and older control subjects.

CONCLUSIONS

Further study of the clinical significance of this altered pattern of interregional connectivity in active and recently retired NFL players is needed.

Task-related functional magnetic resonance imaging activations in patients with acute and subacute mild traumatic brain injury: A coordinate-based meta-analysis

•

ALE meta-analysis revealed functional activation differences in mTBI.

•

Reduced activation identified within the right middle frontal gyrus.

•

Suggests alteration of prefrontal region, associated with executive functioning.

•

Need for addressing subject- and task-specific variation in future studies.

Task-based functional magnetic resonance imaging (fMRI) has been used to examine neuroanatomical and functional changes following mild traumatic brain injury (mTBI). Prior studies have lacked consistency in identifying common regions of altered neural activity during cognitive tasks. This may be partly due to differences in task paradigm, patient heterogeneity, and methods of fMRI analysis. We conducted a meta-analysis using an activation likelihood estimation (ALE) method to identify regions of differential brain activation in patients with mTBI compared to healthy controls. We included experiments that performed scans from acute to subacute time points post-injury. The seven included studies recruited a total sample of 174 patients with mTBIs and 139 control participants. The results of our coordinate based meta-analysis revealed a single cluster of reduced activation within the right middle frontal gyrus (MFG) that differentiated mTBI from healthy controls. We conclude that the cognitive impairments in memory and attention typically reported in mTBI patients may be associated with a deficit in the right MFG, which impacts the recruitment of neural networks important for attentional control.

Assessment of executive function in bilingual adults with history of mild traumatic brain injury

Background and objective:

Adults with a history of traumatic brain injury (TBI) often show deficits in executive function (EF), including the ability to inhibit, switch, and attend to task relevant information. Although performances differences between bilinguals and monolinguals have been observed in EF tasks, there is little research on the effect of TBI on EF in bilinguals. In this study, an ecologically valid standardized measure and experimental computerized tasks of EF were administered to Spanish-English bilingual adults with and without history of mild traumatic brain injury (mTBI).

Method:

Twenty-two bilinguals with a history of mTBI [mean age=20.1 years, SD=3.7; education=13.4 years, SD=0.7] and 20 control bilinguals [mean age=20.8 years, SD=3.6; education=13.7 years, SD=1.1], matched for age and education, completed language proficiency questionnaires, the Functional Assessment of Verbal Reasoning and Executive Strategies (FAVRES), English and Spanish language assessments, and a Flanker task (a test of inhibition).

Results:

Performance was analyzed using analyses of covariance. The results revealed that bilinguals with a history of mTBI performed worse on both the standardized assessment (FAVRES) and inhibition task. Interestingly, self-reported EF deficits were consistent with performance on these measures.

Conclusion:

The findings of this study provide useful information regarding assessment of EF deficits in bilinguals with a history mTBI. Computerized experimental tasks of EF may also prove useful in the assessment of EF in individuals with mTBI.

MRI Evidence of Neuropathic Changes in Former College Football Players

OBJECTIVE

To examine effects of participating in collegiate football on neural health several years after retirement. We hypothesized that relative cortical thinning and loss of white matter integrity would be observed in former players.

DESIGN

Former NCAA Division I football players were compared with demographically similar track-and-field athletes with regard to cortical thickness and white matter integrity.

SETTING

Participants participated in MRI scans at the Center for Imaging Research at the University of Cincinnati.

PARTICIPANTS

Eleven former football players and 10 demographically similar track-and-field athletes.

MAIN OUTCOME MEASURES

Normalized cortical thickness was compared between groups using 2-tailed Student t test. As a secondary analysis, Spearman correlation coefficient was calculated between cortical thickness and number of concussions. Fractional anisotropy for regions-of-interest placed in frontal white matter tracts and internal capsule were compared between groups using 2-tailed Student t test.

RESULTS

Football players showed significantly lower cortical thickness within portions of both the frontal and temporal cortex. Affected frontal regions included left frontal pole and right superior frontal gyrus. Affected temporal regions included portions of the superior temporal gyrus, left inferior temporal gyrus, and right middle and superior temporal gyri. Cortical thickness inversely correlated with number of reported concussions over most of these regions. In addition, fractional anisotropy was lower in the right internal capsule of former football players, relative to controls.

CONCLUSIONS

These findings suggest that at least some consequences of high-level collegiate football play persist even after the cessation of regular head blows. Longer-term studies are warranted to examine potential cognitive and functional implications of sustained cortical atrophy.

Balance Regularity Among Former High School Football Players With or Without a History of Concussion

CONTEXT

  Subclinical postural-control changes may persist beyond the point when athletes are considered clinically recovered postconcussion.

OBJECTIVE

  To compare postural-control performance between former high school football players with or without a history of concussion using linear and nonlinear metrics.

DESIGN

  Case-control study.

SETTING

  Clinical research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 11 former high school football players (age range, 45-60 years) with 2 or more concussions and 11 age- and height-matched former high school football players without a history of concussion. No participant had college or professional football experience.

MAIN OUTCOME MEASURE(S)

  Participants completed the Sensory Organization Test. We compared postural control (linear: equilibrium scores; nonlinear: sample and multiscale entropy) between groups using a 2 × 3 analysis of variance across conditions 4 to 6 (4: eyes open, sway-referenced platform; 5: eyes closed, sway-referenced platform; 6: eyes open, sway-referenced surround and platform).

RESULTS

  We observed a group-by-condition interaction effect for medial-lateral sample entropy ( F2,40 = 3.26, P = .049, ηp2 = 0.140). Participants with a history of concussion presented with more regular medial-lateral sample entropy values (0.90 ± 0.41) for condition 5 than participants without a history of concussion (1.30 ± 0.35; mean difference = -0.40; 95% confidence interval [CI] = -0.74, -0.06; t20 = -2.48, P = .02), but conditions 4 (mean difference = -0.11; 95% CI: -0.37, 0.15; t20 = -0.86, P = .40) and 6 (mean difference = -0.25; 95% CI: -0.55, 0.06; t20 = -1.66, P = .11) did not differ between groups.

CONCLUSIONS

  Postconcussion deficits, detected using nonlinear metrics, may persist long after injury resolution. Subclinical concussion deficits may persist for years beyond clinical concussion recovery.

Functional Magnetic Resonance Imaging of Cognitive Control following Traumatic Brain Injury

Novel and non-routine tasks often require information processing and behavior to adapt from moment to moment depending on task requirements and current performance. This ability to adapt is an executive function that is referred to as cognitive control. Patients with moderate-to-severe traumatic brain injury (TBI) have been reported to exhibit impairments in cognitive control and functional magnetic resonance imaging (fMRI) has provided evidence for TBI-related alterations in brain activation using various fMRI cognitive control paradigms. There is some support for greater and more extensive cognitive control-related brain activation in patients with moderate-to-severe TBI, relative to comparison subjects without TBI. In addition, some studies have reported a correlation between these activation increases and measures of injury severity. Explanations that have been proposed for increased activation within structures that are thought to be directly involved in cognitive control, as well as the extension of this over-activation into other brain structures, have included compensatory mechanisms, increased demand upon normal processes required to maintain adequate performance, less efficient utilization of neural resources, and greater vulnerability to cognitive fatigue. Recent findings are also consistent with the possibility that activation increases within some structures, such as the posterior cingulate gyrus, may reflect a failure to deactivate components of the default mode network (DMN) and that some cognitive control impairment may result from ineffective coordination between the DMN and components of the salience network. Functional neuroimaging studies examining cognitive control-related activation following mild TBI (mTBI) have yielded more variable results, with reports of increases, decreases, and no significant change. These discrepancies may reflect differences among the various mTBI samples under study, recovery of function in some patients, different task characteristics, and the presence of comorbid conditions such as depression and posttraumatic stress disorder that also alter brain activation. There may be mTBI populations with activation changes that overlap with those found following more severe injuries, including symptomatic mTBI patients and those with acute injuries, but future research to address such dysfunction will require well-defined samples with adequate controls for injury characteristics, comorbid disorders, and severity of post-concussive symptoms.

Language control in bilingual adults with and without history of mild traumatic brain injury

Adults with a history of traumatic brain injury often show deficits in executive functioning (EF), including the ability to inhibit, switch, and attend to tasks. These abilities are critical for language processing in bilinguals. This study examined the effect of mild traumatic brain injury (mTBI) on EF and language processing in bilinguals using behavioral and eye-tracking measures. Twenty-two bilinguals with a history of mTBI and twenty healthy control bilinguals were administered executive function and language processing tasks. Bilinguals with a history of mTBI showed deficits in specific EFs and had higher rates of language processing errors than healthy control bilinguals. Additionally, individuals with a history of mTBI have different patterns of eye movements during reading than healthy control bilinguals. These data suggest that language processing deficits are related to underlying EF abilities. The findings provide important information regarding specific EF and language control deficits in bilinguals with a history mTBI.

A review of neuroimaging findings in repetitive brain trauma

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease confirmed at postmortem. Those at highest risk are professional athletes who participate in contact sports and military personnel who are exposed to repetitive blast events. All neuropathologically confirmed CTE cases, to date, have had a history of repetitive head impacts. This suggests that repetitive head impacts may be necessary for the initiation of the pathogenetic cascade that, in some cases, leads to CTE. Importantly, while all CTE appears to result from repetitive brain trauma, not all repetitive brain trauma results in CTE. Magnetic resonance imaging has great potential for understanding better the underlying mechanisms of repetitive brain trauma. In this review, we provide an overview of advanced imaging techniques currently used to investigate brain anomalies. We also provide an overview of neuroimaging findings in those exposed to repetitive head impacts in the acute/subacute and chronic phase of injury and in more neurodegenerative phases of injury, as well as in military personnel exposed to repetitive head impacts. Finally, we discuss future directions for research that will likely lead to a better understanding of the underlying mechanisms separating those who recover from repetitive brain trauma vs. those who go on to develop CTE.

FMRI hypoactivation during verbal learning and memory in former high school football players with multiple concussions

Multiple concussions before the age of 18 may be associated with late-life memory deficits. This study examined neural activation associated with verbal encoding and memory retrieval in former athletes ages 40-65 who received at least two concussions (median = 3; range = 2-15) playing high school football and a group of former high school football players with no reported history of concussions matched on age, education, and pre-morbid IQ. Functional magnetic resonance imaging data collected during a modified verbal paired associates paradigm indicated that those with concussive histories had hypoactivation in left hemispheric language regions, including the inferior/middle frontal gyri and angular gyrus compared with controls. However, concussive history was not associated with worse memory functioning on neuropsychological tests or worse behavioral performance during the paradigm, suggesting that multiple early-life concussions may be associated with subtle changes in the verbal encoding system that limits one from accessing higher-order semantic networks, but this difference does not translate into measurable cognitive performance deficits.

Multimodal imaging of mild traumatic brain injury and persistent postconcussion syndrome

BACKGROUND

Persistent postconcussion syndrome (PCS) occurs in around 5-10% of individuals after mild traumatic brain injury (mTBI), but research into the underlying biology of these ongoing symptoms is limited and inconsistent. One reason for this could be the heterogeneity inherent to mTBI, with individualized injury mechanisms and psychological factors. A multimodal imaging study may be able to characterize the injury better.

AIM

To look at the relationship between functional (fMRI), structural (diffusion tensor imaging), and metabolic (magnetic resonance spectroscopy) data in the same participants in the long term (>1 year) after injury. It was hypothesized that only those mTBI participants with persistent PCS would show functional changes, and that these changes would be related to reduced structural integrity and altered metabolite concentrations.

METHODS

Functional changes associated with persistent PCS after mTBI (>1 year postinjury) were investigated in participants with and without PCS (both n = 8) and non-head injured participants (n = 9) during performance of working memory and attention/processing speed tasks. Correlation analyses were performed to look at the relationship between the functional data and structural and metabolic alterations in the same participants.

RESULTS

There were no behavioral differences between the groups, but participants with greater PCS symptoms exhibited greater activation in attention-related areas (anterior cingulate), along with reduced activation in temporal, default mode network, and working memory areas (left prefrontal) as cognitive load was increased from the easiest to the most difficult task. Functional changes in these areas correlated with reduced structural integrity in corpus callosum and anterior white matter, and reduced creatine concentration in right dorsolateral prefrontal cortex.

CONCLUSION

These data suggest that the top-down attentional regulation and deactivation of task-irrelevant areas may be compensating for the reduction in working memory capacity and variation in white matter transmission caused by the structural and metabolic changes after injury. This may in turn be contributing to secondary PCS symptoms such as fatigue and headache. Further research is required using multimodal data to investigate the mechanisms of injury after mTBI, but also to aid individualized diagnosis and prognosis.

Combat veterans with comorbid PTSD and mild TBI exhibit a greater inhibitory processing ERP from the dorsal anterior cingulate cortex

Posttraumatic stress disorder (PTSD) is common among combat personnel with mild traumatic brain injury (mTBI). While patients with either PTSD or mTBI share abnormal activation of multiple frontal brain areas, anterior cingulate cortex (ACC) activity during inhibitory processing may be particularly affected by PTSD. To further test this hypothesis, we recorded electroencephalography from 32 combat veterans with mTBI-17 of whom were also comorbid for PTSD (mTBI+PTSD) and 15 without PTSD (mTBI-only). Subjects performed the Stop Task, a validated inhibitory control task requiring inhibition of initiated motor responses. We observed a larger inhibitory processing eventrelated potential (ERP) in veterans with mTBI+PTSD, including greater N200 negativity. Furthermore, greater N200 negativity correlated with greater PTSD severity. This correlation was most dependent on contributions from the dorsal ACC. Support vector machine analysis demonstrated that N200 and P300 amplitudes objectively classified veterans into mTBI-only or mTBI+PTSD groups with 79.4% accuracy. Our results support a model where, in combat veterans with mTBI, larger ERPs from cingulate areas are associated with greater PTSD severity and likely related to difficulty controlling ongoing brain processes, including trauma-related thoughts and feelings.

Return-to-play guidelines in concussion: revisiting the literature

Return-to-play (RTP) guidelines in concussion management and treatment continue to challenge clinicians, despite recent updates to the protocols and the ongoing media attention. The current guidelines address individualized treatment planning but are difficult to apply to athletes who experience prolonged symptoms, are younger, or have sustained multiple concussions. Recent literature findings have contributed to an improved understanding and applicability of the guidelines while emphasizing a multidisciplinary paradigm in formulating an individualized RTP decision. Successful implementation of the RTP guidelines will ensure that athletes are protected from further injury and return to their baseline functional status.

Advanced neuroimaging of mild traumatic brain injury

This article focuses on advancements in neuroimaging techniques, compares the advantages of each of the modalities in the evaluation of mild traumatic brain injury, and discusses their contribution to our understanding of the pathophysiology as it relates to prognosis. Advanced neuroimaging techniques discussed include anatomic/structural imaging techniques, such as diffusion tensor imaging and susceptibility-weighted imaging, and functional imaging techniques, such as functional magnetic resonance imaging, perfusion-weighted imaging, magnetic resonance spectroscopy, and positron emission tomography.

Screening for lifetime concussion in athletes: importance of oculomotor measures

HYPOTHESIS/OBJECTIVE

The purpose of the present study was to determine the utility of oculomotor-based evaluation protocols in screening for lifetime concussion incidence in elite hockey players.

METHODS

Forty-two Division I collegiate male and female hockey players were evaluated using the guidelines of an overall oculomotor-based diagnostic clinical test protocol for the mTBI population. The sensitivity of the collected measures to lifetime concussion was then compared with the corresponding sensitivity of measures of neuropsychological functioning (ImPACT) often used with athletes for acute concussion diagnosis.

RESULTS

This model showed that a hockey player with a Near Point of Fixation Disparity (NPFD) equal to or greater than 15 cm, Visagraph comprehension rate less than 85% and the total score on part A of an ADHD questionnaire equal to or greater than 11 was on average 10.72-times more likely to have previously suffered a concussion than an athlete with lower values on the NPFD and ADHD questionnaire and a higher comprehension rate on the Visagraph. None of the IMPACT baseline assessment measures were significantly predictive of the individual's concussion history.

CONCLUSION

The study provides a relatively sensitive screening tool to assess the probability of previous concussion(s) in an athlete. This model may allow athletic personnel to address in a timely manner the risks associated with repeat concussions and to develop individualized concussion management protocols.

Animal models of sports-related head injury: bridging the gap between pre-clinical research and clinical reality

Sports-related head impact and injury has become a very highly contentious public health and medico-legal issue. Near-daily news accounts describe the travails of concussed athletes as they struggle with depression, sleep disorders, mood swings, and cognitive problems. Some of these individuals have developed chronic traumatic encephalopathy, a progressive and debilitating neurodegenerative disorder. Animal models have always been an integral part of the study of traumatic brain injury in humans but, historically, they have concentrated on acute, severe brain injuries. This review will describe a small number of new and emerging animal models of sports-related head injury that have the potential to increase our understanding of how multiple mild head impacts, starting in adolescence, can have serious psychiatric, cognitive and histopathological outcomes much later in life. Sports-related head injury (SRHI) has emerged as a significant public health issue as athletes can develop psychiatric and neurodegenerative disorders later in life. Animal models have always been an integral part of the study of human TBI but few existing methods are valid for studying SRHI. In this review, we propose criteria for effective animal models of SRHI. Movement of the head upon impact is judged to be of primary importance in leading to concussion and persistent CNS dysfunction.

Concussion symptoms and neurocognitive performance of high school and college athletes who incur multiple concussions

BACKGROUND

Multiple concussions have been associated with prolonged symptoms, recovery time, and risk for future concussions. However, very few studies have examined the effect of multiple concussions on neurocognitive performance and the recently revised symptom clusters using a large database.

PURPOSE

To examine concussed athletes with a history of 0, 1, 2, or ≥3 concussions on neurocognitive performance and the recently revised symptom clusters.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

The independent variables were concussion group (0, 1, 2, and ≥3 concussions) and time (baseline, 3 days, and 8 days). The dependent variables were neurocognitive test scores as measured by the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) neurocognitive test battery (verbal and visual memory, processing speed, and reaction time) and 4 concussion symptom clusters (migraine-cognitive-fatigue, affective, somatic, and sleep). All concussed athletes (n = 596) were administered the ImPACT test at a mean 2.67 ± 1.98 and 7.95 ± 4.46 days after injury. A series of 4 (concussion group) × 3 (time) repeated-measures analyses of covariance (age = covariate) were performed on ImPACT composite scores and symptom clusters.

RESULTS

Concussed athletes with ≥3 concussions were still impaired 8 days after a concussion compared with baseline scores on verbal memory (P < .001), reaction time (P < .001), and migraine-cognitive-fatigue symptoms (P < .001). There were no significant findings on the remaining dependent variables.

CONCLUSION

Concussed athletes with a history of ≥3 concussions take longer to recover than athletes with 1 or no previous concussion. Future research should concentrate on validating the new symptom clusters on multiple concussed athletes, examining longer recovery times (ie, >8 days) among athletes with multiple concussions.

Minimal functional brain differences between older adults with and without mild cognitive impairment during the stroop

This investigation compared the neural correlates of inhibition in normal older adults (OAs) and OAs with mild cognitive impairment (MCI). It was hypothesized the MCI group would require a greater amount of resources for inhibition, and therefore display greater functional activation in specific regions of interest (ROIs). Twenty-six OAs without and 17 with MCI completed the Stroop task during functional neuroimaging, and completed additional out-of-scanner neuropsychological measures. During inhibition, there were minimal functional Magnetic Resonance Imaging (fMRI) differences found between groups in a priori specified ROIs and with post-hoc multiple regression analyses. However, these minimal differences did not survive corrected thresholds. Robust differences were found with several tasks of a neuropsychological screening battery. The results of this study suggest only very minimal group differences in fMRI activation during inhibition which may not reliably identify MCI, and this condition may be best detected by traditional neuropsychological techniques.