Julianne D. Schmidt

Identifying Impairments after Concussion: Normative Data versus Individualized Baselines

PURPOSE This study aimed to determine whether agreement exists between baseline comparison (comparison of postconcussion scores to individualized baseline scores) and normative comparison (comparison of postconcussion scores to a normative mean) in identifying impairments after concussion. METHODS A total of 1060 collegiate student-athletes completed baseline testing as part of an ongoing clinical program. Gender-specific normative means were obtained from a subset of 673 athletes with no history of self-reported concussion, learning disabilities, or attention-deficit disorders. Concussions were later diagnosed in 258 athletes who had completed baseline testing. The athletes completed their first assessment within 10 d after injury. Athletes completed a computerized neurocognitive test (Automated Neuropsychological Assessment Metrics), postural control assessment (Sensory Organization Test), and a 15-item graded symptom checklist at baseline and again after injury. We computed two postconcussion difference scores for each outcome measure: 1) baseline difference = postconcussion score--individualized baseline score and 2) normative difference = postconcussion score--normative mean. Athletes were considered impaired if postconcussion difference exceeded the reliable change parameters. McNemar tests were used to assess agreement on impairment status (impaired and unimpaired) between comparison methods for each outcome measure. RESULTS The baseline comparison method identified 2.6 times more impairments than the normative comparison method for the Simple Reaction Time Test 1 (P = 0.043). The normative comparison method identified 7.6 times more impairments than the baseline comparison method for Mathematical Processing (P < 0.001). No other disagreements were observed for postural control or symptom severity. CONCLUSIONS Our findings suggest that, when using these concussion assessment tools, clinicians may consider using normative data in lieu of individualized baseline measures. This may be especially useful to clinicians with limited resources and an inability to capture valid baselines on all athletes.

Reliable change, sensitivity, and specificity of a multidimensional concussion assessment battery: implications for caution in clinical practice.

Objective:To provide reliable change confidence intervals for common clinical concussion measures using a healthy sample of collegiate athletes and to apply these reliable change parameters to a sample of concussed collegiate athletes. Methods:Two independent samples were included in the study and evaluated on common clinical measures of concussion. The healthy sample included male, collegiate football student-athletes (n = 38) assessed at 2 time points. The concussed sample included college-aged student-athletes (n = 132) evaluated before and after a concussion. Outcome measures included symptom severity scores, Automated Neuropsychological Assessment Metrics throughput scores, and Sensory Organization Test composite scores. Results:Application of the reliable change parameters suggests that a small percentage of concussed participants were impaired on each measure. We identified a low sensitivity of the entire battery (all measures combined) of 50% but high specificity of 96%. Conclusions:Clinicians should be trained in understanding clinical concussion measures and should be aware of evidence suggesting the multifaceted battery is more sensitive than any single measure. Clinicians should be cautioned that sensitivity to balance and neurocognitive impairments was low for each individual measure. Applying the confidence intervals to our injured sample suggests that these measures do not adequately identify postconcussion impairments when used in isolation.

The effect of play type and collision closing distance on head impact biomechanics.

Football accounts for 55% of concussions to collegiate athletes. In the National Football League, players are at a greater risk for concussion during kickoffs and punts compared to rushing and passing plays. The two primary purposes of this study were to determine if game-related special teams head impacts were greater in magnitude than head impacts sustained during offensive and defensive plays, and to better understand the effect closing distance between players (short vs. long) had on head impact magnitude. Collegiate football players were enrolled in a prospective cohort study assessing head impact biomechanics during special teams, offensive, and defensive collisions; long closing distance (≥10 yards) and short closing distance (<10 yards) impacts were also studied. Data were analyzed using random intercepts general linear mixed models. Long closing distance collisions generated more severe head impacts than short closing distances. Collisions occurring on special teams plays over long closing distances were most severe while collisions occurring on special teams and defensive plays over short closing distances resulted in the least severe impacts. Decreasing the impact severity of collisions in collegiate football may be accomplished by reducing the closing distance prior to impact.

The Influence of Cervical Muscle Characteristics on Head Impact Biomechanics in Football

Background: An athlete is thought to reduce head acceleration after impact by contracting the cervical musculature, which increases the effective mass of the head. Purpose: To compare the odds of sustaining higher magnitude in-season head impacts between athletes with higher and lower preseason performance on cervical muscle characteristics. Study Design: Cohort study; Level of evidence, 2. Methods: Forty-nine high school and collegiate American football players completed a preseason cervical testing protocol that included measures of cervical isometric strength, muscle size, and response to cervical perturbation. Head impact biomechanics were captured for each player using the Head Impact Telemetry System. A median split was used to categorize players as either high or low performers for each of the following outcome measures: isometric strength (peak torque, rate of torque development), muscle size (cross-sectional area), and response to cervical perturbation (stiffness, angular displacement, muscle onset latency). The odds of sustaining moderate and severe head impacts were computed against the reference odds of sustaining mild head impacts across cervical characteristic categorizations. Results: Linemen with stronger lateral flexors and composite cervical strength had about 1.75 times’ increased odds of sustaining moderate linear head impacts rather than mild impacts compared with weaker linemen. Players who developed extensor torque more quickly had 2 times the increased odds of sustaining severe linear head impacts (odds ratio [OR], 2.10; 95% CI, 1.08-4.05) rather than mild head impacts. However, players with greater cervical stiffness had reduced odds of sustaining both moderate (OR, 0.77; 95% CI, 0.61-0.96) and severe (OR, 0.64; 95% CI, 0.46-0.89) head impacts compared with players with less cervical stiffness. Conclusion: The study findings showed that greater cervical stiffness and less angular displacement after perturbation reduced the odds of sustaining higher magnitude head impacts; however, the findings did not show that players with stronger and larger neck muscles mitigate head impact severity.

The sensitivity and specificity of clinical measures of sport concussion: three tests are better than one

Context A battery of clinical measures of neurocognition, balance and symptoms has been recommended for the management of sport concussion (SC) but is based on variable evidence. Objective To examine the sensitivity and specificity of a battery of tests to assess SC in college athletes. Design Cross-sectional. Setting Research laboratory. Patients or other participants Division 1 athletes diagnosed with a SC (n=40) who were 20.2±1.60 years of age and 180.5±11.12 cm tall and healthy athletes (n=40) who were 19.0±0.93 years of age and 179.1±11.39 cm tall were enrolled. Intervention(s) Participants were administered Immediate Postconcussion Assessment and Cognitive Test (ImPACT), the Sensory Organization Test (SOT) and the Revised Head Injury Scale (HIS-r) prior to and up to 24 h following injury between the 2004 and 2014 sport seasons. Sensitivity and specificity were calculated using predictive discriminant analyses (PDA) and clinical interpretation guidelines. Main outcome measures Outcome measures included baseline and postinjury ImPACT, SOT and HIS-r composite scores. Results Using PDA, each clinical measures sensitivity ranged from 55.0% to 77.5% and specificity ranged from 52.5% to 100%. The test battery possessed a sensitivity and specificity of 80.0% and 100%, respectively. Using clinical interpretation guidelines, sensitivity ranged from 55% to 97.5% individually, and 100% when combined. Conclusions Our results support a multidimensional approach to assess SC in college athletes which correctly identified 80–100% of concussed participants as injured. When each test was evaluated separately, up to 47.5% of our sample was misclassified. Caution is warranted when using singular measures to manage SC.

Effects of Attention Deficit Hyperactivity Disorder and Stimulant Medication on Concussion Symptom Reporting and Computerized Neurocognitive Test Performance

Effects of attention deficit hyperactivity disorder (ADHD) and stimulant medications on concussion measures are unclear. The objectives of this study were to (i) examine consistency of performance in an unmedicated ADHD group and a control group on concussion measures, (ii) assess performance differences between the two groups, and (iii) assess the effect of stimulant medication on performance in the ADHD group. College-aged participants (22 ADHD and 22 matched controls) were administered a symptom checklist and a computerized neurocognitive test (CNS Vital Signs, CNSVS) 3 times (1 week apart): Sessions 1 and 2 were unmedicated for all participants; Session 3 was medicated for the ADHD group. The reliability of the measures (intraclass correlation coefficients, ICC2,1) was consistent for both groups. When unmedicated, the ADHD group performed worse than controls on psychomotor speed [F(1,40) = 15.19, p < 0.001], and worse than when medicated on reaction time [F(1,39) = 6.34, p = 0.02]. The ADHD group performed better and comparable with controls when medicated. Clinicians should take medication status into account when interpreting scores.

Outcomes, utility, and feasibility of single task and dual task intervention programs: preliminary implications for post-concussion rehabilitation.

OBJECTIVES To examine neurocognitive and balance performance in recreational athletes, prior to and following a dual-task training intervention compared to single-task controls in order to assess the utility and feasibility of these interventions in the clinical setting. DESIGN Controlled laboratory study. METHODS Thirty healthy, physically active recreational athletes (dual-task group = 15; single-task group = 15; age: 20.3 ± 1.9 years) completed neurocognitive and balance assessments before and after a four-week intervention. Sensory Organization Test composite score and ratio scores, Balance Error Scoring System total score, and nine CNS Vital Signs composite scores served as outcome measures. Mixed model analyses of variance were used to examine each measure. RESULTS The single-task group showed greater improvement for complex attention (F1,26 = 5.48, p = .027) following the training period. Both groups improved their performance on the complex attention domain (F1,26 = 6.73, p = .015), the Balance Error Scoring System score (F1,26 = 42.34, p < .001), and the Sensory Organization Test vestibular ratio score (F1,28 = 6.55, p = .016) following the intervention. CONCLUSIONS Our findings suggest combining cognitive and balance tasks as performed does not provide additional benefit to performing these tasks independently among healthy individuals, but appear to be feasible in this setting. Future research should examine integration of single-task and dual-task exercises for concussed patients.

Prevention and Management of Physical and Social Environment Risk Factors for Sports-Related Injuries

An understanding of the environmental factors that contribute to injury risk will allow for the optimization of athletic performance and minimize morbidity. The purpose of this review is to discuss the physical and social environments of sport that affect injury risk, and to review the strategies that sports medicine professionals (eg, clinicians, certified athletic trainers) can implement to prevent injury. Searches using the PubMed, Cochrane, and Google Scholar databases were used to identify injury risk factors pertaining to the physical and social environment of athletics. Physical environmental risk factors identified include weather, air quality, playing surface, and the presence of sports medicine professionals. Social environmental factors include parents, teammates, coaches, media, policy/legislation, and sports medicine professionals. Sports medicine professionals seeking effective prevention and care strategies will benefit from (1) education about the physical and social environmental risk factors that place athletes at risk for injury and (2) a holistic approach that recognizes that physical and social factors are as important as individual risk factors in determining injury risk.

Does visual performance influence head impact severity among high school football athletes

Objective:To compare the odds of sustaining moderate and severe head impacts, rather than mild, between high school football players with high and low visual performance. Design:Prospective quasi-experimental. Setting:Clinical Research Center/On-field. Participants:Thirty-seven high school varsity football players. Interventions:Athletes completed the Nike SPARQ Sensory Station visual assessment before the season. Head impact biomechanics were captured at all practices and games using the Head Impact Telemetry System. Main Outcome Measures:Each player was classified as either a high or low performer using a median split for each of the following visual performance measures: visual clarity, contrast sensitivity, depth perception, near–far quickness, target capture, perception span, eye–hand coordination, go/no go, and reaction time. We computed the odds of sustaining moderate and severe head impacts against the reference odds of sustaining mild head impacts across groups of high and low performers for each of the visual performance measures. Results:Players with better near–far quickness had increased odds of sustaining moderate [odds ratios (ORs), 1.27; 95% confidence intervals (CIs), 1.04-1.56] and severe head impacts (OR, 1.45; 95% CI, 1.05-2.01) as measured by Head Impact Technology severity profile. High and low performers were at equal odds on all other measures. Conclusions:Better visual performance did not reduce the odds of sustaining higher magnitude head impacts. Visual performance may play less of a role than expected for protecting against higher magnitude head impacts among high school football players. Further research is needed to determine whether visual performance influences concussion risk. Clinical Relevance:Based on our results, we do not recommend using visual training programs at the high school level for the purpose of reducing the odds of sustaining higher magnitude head impacts.

Driving after Concussion: Is It Safe To Drive after Symptoms Resolve?

Post-concussion impairments may result in unsafe driving performance, but little research is available to guide consensus on when concussed individuals should return to driving. The purpose of this study was to compare driving performance between individuals with and without a concussion and to explore relationships between neuropsychological and driving performance. Fourteen participants with concussion (age 20.2 ± 0.9 years old) and 14 non-concussed age- and driving experience-matched controls (age 20.4 ± 1.1 years old) completed a graded symptom checklist, a brief neuropsychological exam, and a 20.5 km driving simulation task. Participants with a concussion completed driving simulation within 48 h of becoming asymptomatic (15.9 ± 9.0 days post-concussion). One-way analyses of variance were used to compare total number of crashes, tickets, and lane excursions, as well as standard deviation of lateral position (SDLP) and standard deviation of speed. Pearsons correlations were conducted to explore the relationship between the neuropsychological and driving performance separately by group (α = 0.05). Participants with a concussion committed more frequent lane excursions (concussed 10.9 ± 4.5; controls 7.4 ± 2.4; p = 0.017) and exhibited greater SDLP, compared with controls, during the first curve (concussed 45.7 ± 21.3 cm, controls 27.4 ± 6.1 cm; p = 0.030) and final curve (concussed 39.6 ± 24.4 cm; controls 33.5 ± 21.3 cm; p = 0.036). Poorer performance on symbol digit modalities (r = -0.54), Rey Osterrieth Complex Figure (r = -0.53), verbal memory (r = -0.77), and motor speed (r = -0.54) were correlated with more frequent lane excursions in the concussed group, but not in the control group. Despite being asymptomatic, concussed participants exhibited poorer vehicle control, especially when navigating curves. Driving impairments may persist beyond when individuals with a concussion have returned to driving. Our study provides preliminary guidance regarding which neuropsychological functions may best indicate driving impairment following concussion.