Partial Balint's syndrome and left homonymous hemianopsia presenting after resection of a right occipito-parietal glioblastoma.

A 66-year-old left-handed male was admitted to our acute inpatient rehabilitation (AIR) unit following a resection of the right occipito-parietal glioblastoma. He presented with symptoms of horizontal oculomotor apraxia, contralateral optic ataxia and left homonymous hemianopsia. We diagnosed this patient with partial Bálint's syndrome (BS)- oculomotor apraxia, optic ataxia but not simultanagnosia. BS is typically caused by bilateral posterior parietal lesions, but we here describe a unique case due toresection of a right intracranial tumor. A short AIR stay allowed our patient to learn how to compensate for visuomotor and visuospatial deficits, and improved his quality of life significantly.

Adverse events related to total ankle replacement devices: an analysis of reports to the United States Food and Drug Administration.

BACKGROUND: The published outcomes of total ankle replacement (TAR) implants came from limited institutions creating observational bias. For broader perspective, we queried the Food and Drug Administration's (FDA) Manufacturer and User Facility Device Experience (MAUDE) voluntary database to explore complications reported outside published literature. METHODS: The database was reviewed retrospectively between November 2011 and April 2019 using two product codes assigned to six TAR devices. RESULTS: Among 648 relevant reports available in the database, common complications were aseptic loosening (19.3%), infection (18.2%), and alignment/mechanical issues (16.5%). Others included instrument/instrumentation complications, impingement, polyethylene problems, fractures, avascular necrosis of talus (AVN), and packaging issues. CONCLUSION: MAUDE database revealed various patterns of device-related malfunctions that have been under-reported in published data. Despite inconsistency in the available reports, it provided opportunities for improvements in quality control, device design, and ultimately patient safety. Database would be further strengthened by more robust reporting mechanism or mandatory reporting of device-related complications.

Continuous electroencephalography predicts delayed cerebral ischemia after subarachnoid hemorrhage: A prospective study of diagnostic accuracy.

OBJECTIVE: Delayed cerebral ischemia (DCI) is a common, disabling complication of subarachnoid hemorrhage (SAH). Preventing DCI is a key focus of neurocritical care, but interventions carry risk and cannot be applied indiscriminately. Although retrospective studies have identified continuous electroencephalographic (cEEG) measures associated with DCI, no study has characterized the accuracy of cEEG with sufficient rigor to justify using it to triage patients to interventions or clinical trials. We therefore prospectively assessed the accuracy of cEEG for predicting DCI, following the Standards for Reporting Diagnostic Accuracy Studies. METHODS: We prospectively performed cEEG in nontraumatic, high-grade SAH patients at a single institution. The index test consisted of clinical neurophysiologists prospectively reporting prespecified EEG alarms: (1) decreasing relative alpha variability, (2) decreasing alpha-delta ratio, (3) worsening focal slowing, or (4) late appearing epileptiform abnormalities. The diagnostic reference standard was DCI determined by blinded, adjudicated review. Primary outcome measures were sensitivity and specificity of cEEG for subsequent DCI, determined by multistate survival analysis, adjusted for baseline risk. RESULTS: One hundred three of 227 consecutive patients were eligible and underwent cEEG monitoring (7.7-day mean duration). EEG alarms occurred in 96.2% of patients with and 19.6% without subsequent DCI (1.9-day median latency, interquartile range = 0.9-4.1). Among alarm subtypes, late onset epileptiform abnormalities had the highest predictive value. Prespecified EEG findings predicted DCI among patients with low (91% sensitivity, 83% specificity) and high (95% sensitivity, 77% specificity) baseline risk. INTERPRETATION: cEEG accurately predicts DCI following SAH and may help target therapies to patients at highest risk of secondary brain injury. Ann Neurol 2018;83:958-969.

Early detection of consciousness in patients with acute severe traumatic brain injury.

See Schiff (doi:10.1093/awx209) for a scientific commentary on this article. Patients with acute severe traumatic brain injury may recover consciousness before self-expression. Without behavioural evidence of consciousness at the bedside, clinicians may render an inaccurate prognosis, increasing the likelihood of withholding life-sustaining therapies or denying rehabilitative services. Task-based functional magnetic resonance imaging and electroencephalography techniques have revealed covert consciousness in the chronic setting, but these techniques have not been tested in the intensive care unit. We prospectively enrolled 16 patients admitted to the intensive care unit for acute severe traumatic brain injury to test two hypotheses: (i) in patients who lack behavioural evidence of language expression and comprehension, functional magnetic resonance imaging and electroencephalography detect command-following during a motor imagery task (i.e. cognitive motor dissociation) and association cortex responses during language and music stimuli (i.e. higher-order cortex motor dissociation); and (ii) early responses to these paradigms are associated with better 6-month outcomes on the Glasgow Outcome Scale-Extended. Patients underwent functional magnetic resonance imaging on post-injury Day 9.2 ± 5.0 and electroencephalography on Day 9.8 ± 4.6. At the time of imaging, behavioural evaluation with the Coma Recovery Scale-Revised indicated coma (n = 2), vegetative state (n = 3), minimally conscious state without language (n = 3), minimally conscious state with language (n = 4) or post-traumatic confusional state (n = 4). Cognitive motor dissociation was identified in four patients, including three whose behavioural diagnosis suggested a vegetative state. Higher-order cortex motor dissociation was identified in two additional patients. Complete absence of responses to language, music and motor imagery was only observed in coma patients. In patients with behavioural evidence of language function, responses to language and music were more frequently observed than responses to motor imagery (62.5-80% versus 33.3-42.9%). Similarly, in 16 matched healthy subjects, responses to language and music were more frequently observed than responses to motor imagery (87.5-100% versus 68.8-75.0%). Except for one patient who died in the intensive care unit, all patients with cognitive motor dissociation and higher-order cortex motor dissociation recovered beyond a confusional state by 6 months. However, 6-month outcomes were not associated with early functional magnetic resonance imaging and electroencephalography responses for the entire cohort. These observations suggest that functional magnetic resonance imaging and electroencephalography can detect command-following and higher-order cortical function in patients with acute severe traumatic brain injury. Early detection of covert consciousness and cortical responses in the intensive care unit could alter time-sensitive decisions about withholding life-sustaining therapies.

Electronic Health Data Predict Outcomes After Aneurysmal Subarachnoid Hemorrhage.

BACKGROUD: Using electronic health data, we sought to identify clinical and physiological parameters that in combination predict neurologic outcomes after aneurysmal subarachnoid hemorrhage (aSAH). METHODS: We conducted a single-center retrospective cohort study of patients admitted with aSAH between 2011 and 2016. A set of 473 predictor variables was evaluated. Our outcome measure was discharge Glasgow Outcome Scale (GOS). For laboratory and physiological data, we computed the minimum, maximum, median, and variance for the first three admission days. We created a penalized logistic regression model to determine predictors of outcome and a multivariate multilevel prediction model to predict poor (GOS 1-2), intermediate (GOS 3), or good (GOS 4-5) outcomes. RESULTS: One hundred and fifty-three patients met inclusion criteria; most were discharged with a GOS of 3. Multivariate analysis predictors of mortality (AUC 0.9198) included APACHE II score, Glasgow Come Scale (GCS), white blood cell (WBC) count, mean arterial pressure, variance of serum glucose, intracranial pressure (ICP), and serum sodium. Predictors of death/dependence versus independence (GOS 4-5)(AUC 0.9456) were levetiracetam, mechanical ventilation, WBC count, heart rate, ICP variance, GCS, APACHE II, and epileptiform discharges. The multiclass prediction model selected GCS, admission APACHE II, periodic discharges, lacosamide, and rebleeding as significant predictors; model performance exceeded 80% accuracy in predicting poor or good outcome and exceeded 70% accuracy for predicting intermediate outcome. CONCLUSIONS: Variance in early physiologic data can impact patient outcomes and may serve as targets for early goal-directed therapy. Electronically retrievable features such as ICP, glucose levels, and electroencephalography patterns should be considered in disease severity and risk stratification scores.

High risk for seizures following subarachnoid hemorrhage regardless of referral bias.

BACKGROUND: To investigate the frequency, predictors, and clinical impact of electrographic seizures in patients with high clinical or radiologic grade non-traumatic subarachnoid hemorrhage (SAH), independent of referral bias. METHODS: We compared rates of electrographic seizures and associated clinical variables and outcomes in patients with high clinical or radiologic grade non-traumatic SAH. Rates of electrographic seizure detection before and after institution of a guideline which made continuous EEG monitoring routine in this population were compared. RESULTS: Electrographic seizures occurred in 17.6 % of patients monitored expressly because of clinically suspected subclinical seizures. In unselected patients, seizures still occurred in 9.6 % of all cases, and in 8.6 % of cases in which there was no a priori suspicion of seizures. The first seizure detected occurred 5.4 (IQR 2.9-7.3) days after onset of subarachnoid hemorrhage with three of eight patients (37.5 %) having the first recorded seizure more than 48 h following EEG initiation, and 2/8 (25 %) at more than 72 h following EEG initiation. High clinical grade was associated with poor outcome at time of hospital discharge; electrographic seizures were not associated with poor outcome. CONCLUSIONS: Electrographic seizures occur at a relatively high rate in patients with non-traumatic SAH even after accounting for referral bias. The prolonged time to the first detected seizure in this cohort may reflect dynamic clinical features unique to the SAH population.

Adverse Events Related to Cartiva Hemiarthroplasty of First Metatarsal: An Analysis of Reports to the United States Food and Drug Administration.

Background: The results supporting Cartiva, a synthetic cartilage implant (Wright Medical) in hallux rigidus have come from limited institutions creating observational bias. Complications experienced in community centers are not routinely included in the published literature. To look at a broader range of potential complications, we reviewed the United States Food and Drug Administration's (FDA) voluntary device database and compared that data with published literature. Methods: The Manufacturer and User Facility Device Experience (MAUDE) database of the FDA was retrospectively reviewed between July 2016 and October 2019 using the product code: PNW, assigned for Cartiva. Results: A total of 49 events have been reported and implant subsidence was the most common with 16 reports. Others include fragmentation (9), infection (4), bone erosion (3), foreign body reaction (1) and unspecified (16). Thirty-five events mentioned further surgeries at a mean interval of 4.75 months. Conclusions: The analysis of the MAUDE database disclosed certain device-related dysfunctions that have been underreported in the published literature. Because of the voluntary nature of reporting, the true incidence of each complication is unknown with this data representing a baseline. The MAUDE database could be further strengthened by a more robust reporting mechanism or mandatory reporting of device-related complications.Levels of Evidence: Level IV: Case series from large database analysis.

Speed vernalization to accelerate generation advance in winter cereal crops.

There are many challenges facing the development of high-yielding, nutritious crops for future environments. One limiting factor is generation time, which prolongs research and plant breeding timelines. Recent advances in speed breeding protocols have dramatically reduced generation time for many short-day and long-day species by optimizing light and temperature conditions during plant growth. However, winter crops with a vernalization requirement still require up to 6-10 weeks in low-temperature conditions before the transition to reproductive development. Here, we tested a suite of environmental conditions and protocols to investigate whether the vernalization process can be accelerated. We identified a vernalization method consisting of exposing seeds at the soil surface to an extended photoperiod of 22 h day:2 h night at 10°C with transfer to speed breeding conditions that dramatically reduces generation time in both winter wheat (Triticum aestivum) and winter barley (Hordeum vulgare). Implementation of the speed vernalization protocol followed by speed breeding allowed the completion of up to five generations per year for winter wheat or barley, whereas only two generations can be typically completed under standard vernalization and plant growth conditions. The speed vernalization protocol developed in this study has great potential to accelerate biological research and breeding outcomes for winter crops.

Patient factors in the selection of operative versus nonoperative treatment for posterior tibial tendon dysfunction.

BACKGROUND: The influence of demographic, medical history, and treatment variables on the maintenance of nonoperative care or progression to operative intervention in Posterior Tibial Tendon Dysfunction (PTTD) was explored. This retrospective study compared demographic, medical history and treatment variables between operative and nonoperative care in subjects with PTTD. MATERIALS AND METHODS: Charts with the ICD-9 codes (726.72, 726.90) and brace distribution records for 2005 and 2006 were used to identify subjects. From these, 166 of 606 charts included documentation of PTTD. Variables were grouped into three categories including demographics (Age, body mass index, gender and working status), medical (stage, symptom duration, pain at initial evaluation, and past treatments) and treatment (initial brace, length of care episode, and brace change). Statistical comparisons between subjects treated nonoperatively and operatively were made. Significant variables were entered into a logistic regression analysis. Accuracy (sensitivity/specificity) was assessed by examining the success of predicting which subjects were treated operatively or nonoperatively. RESULTS: Of the 166 subjects, 125 (75.4%) received nonoperative care and 41 (24.6%) operative care. Nine variables distinguished the operative from the nonoperative group (p<0.05): including BMI, work status, stage, symptom duration, prior orthotic use, prior injection, custom brace, brace changes, and length of care episode. The logistic regression model identified BMI, symptom duration, prior cortisone injections, and prior orthotic use as significant and resulted in a specificity of 95.4% and sensitivity of 38.2%. CONCLUSION: This retrospective analysis provides a patient profile of factors in the success of nonoperative care in PTTD.

Instrumented immobilizing boot paradigm quantifies reduced Achilles tendon loading during gait.

Achilles tendon ruptures are common injuries that lead to functional deficits in two-thirds of patients. Progressively loading the healing tendon has been associated with superior outcomes, but the loading profiles that patients experience throughout rehabilitation have not yet been established. In this study, we developed and calibrated an instrumented immobilizing boot paradigm that is aimed at longitudinally quantifying patient loading biomechanics to develop personalized rehabilitation protocols. We used a 3-part instrumented insole to quantify the ankle loads generated by the Achilles tendon and secured a load cell inline with the posterior strut of the immobilizing boot to quantify boot loading. We then collected gait data from five healthy young adults to demonstrate the validity of this instrumented immobilizing boot paradigm to assess Achilles tendon loading during ambulation. We developed a simple calibration procedure to improve the measurement fidelity of the instrumented insole needed to quantify Achilles tendon loading while ambulating with an immobilizing boot. By assessing Achilles tendon loading with the ankle constrained to 0 degrees and 30 degrees plantar flexion, we confirmed that walking with the foot supported in plantar flexion decreased Achilles tendon loading by 60% (P < 0.001). This instrumented immobilizing boot paradigm leverages commercially available sensors and logs data using a small microcontroller secured to the boot and a handheld device, making our paradigm capable of continuously monitoring biomechanical loading outside of the lab or clinic.

Ultrasound echogenicity is associated with fatigue-induced failure in a cadaveric Achilles tendon model.

Achilles tendon disorders are among the most difficult sports-related injuries to predict with current diagnostic tools. The purpose of this study was to identify a clinically useful marker for early tendon damage. We hypothesized that alterations in mean echogenicity are linked with changes in vitro tendon mechanics. To test our hypothesis, we harvested Achilles tendons from 10 fresh-frozen cadaveric feet and cyclically fatigued them using a universal test frame while we continuously acquired ultrasound images. Throughout this fatigue protocol, we applied 2 stress tests every 500 loading cycles to quantify changes in ultrasound imaging echogenicity. We continued this fatigue protocol until each tendon either failed completely or survived 150,000 cycles. Tendons that failed during the fatigue loading (6/10) underwent greater changes in mean echogenicity compared to tendons that did not fail (P = 0.031). These tendons that failed during fatigue loading demonstrated greater changes in mean echogenicity that surpassed 1.0%; whereas survivor tendons exhibited less than 0.5% changes in mean echogenicity. We found that changes in mean echogenicity measured with ultrasound increased proportionally with increased tendon damage. The magnitude of these changes was relatively small (<1.5% change in mean echogenicity) but may be an effective predictor of tendon failure. Mean echogenicity is a promising marker for quantifying fatigue damage in cadaveric Achilles tendons during a stress test. Although these changes cannot be detected with the naked eye, computer-based predictive models may effectively assess risk of tendon damage in physically active adults.

Gastrocnemius fascicles are shorter and more pennate throughout the first month following acute Achilles tendon rupture.

The purpose of this study was to characterize the short-term effects of Achilles tendon ruptures on medial gastrocnemius. We hypothesized that the fascicles of the medial gastrocnemius muscle of the injured Achilles tendon would be shorter and more pennate immediately following the injury and would persist throughout 4 weeks post-injury. B-mode longitudinal ultrasound images of the medial gastrocnemius were acquired in 10 adults who suffered acute Achilles tendon ruptures and were treated non-operatively. Ultrasound images were acquired during the initial clinical visit following injury as well as 2 and 4 weeks following this initial clinical visit. Resting muscle structure was characterized by measuring fascicle length, pennation angle, muscle thickness, and muscle echo intensity in both the injured and contralateral (control) limbs. Fascicle length was 15% shorter (P < 0.001) and pennation angle was 21% greater (P < 0.001) in the injured muscle compared to the uninjured (control) muscle at the presentation of injury (week 0). These differences in fascicle length persisted through 4 weeks after injury (P < 0.002) and pennation angle returned to pre-injury levels. Muscle thickness changes were not detected at any of the post-injury visits (difference < 4%, P > 0.026). Echo intensity of the injured limb was 8% lower at the presentation of the injury but was not different compared to the contralateral muscle at 2 and 4 weeks post-injury. Our results suggest that Achilles tendon ruptures elicit rapid changes in the configuration of the medial gastrocnemius, which may explain long-term functional deficits.

Medial gastrocnemius muscle remodeling correlates with reduced plantarflexor kinetics 14 weeks following Achilles tendon rupture.

Deficits in plantarflexor kinetics are associated with poor outcomes in patients following Achilles tendon rupture. In this longitudinal study, we analyzed the fascicle length and pennation angle of the medial gastrocnemius muscle and the length of the Achilles tendon using ultrasound imaging. To determine the relationship between muscle remodeling and deficits in plantarflexor kinetics measured at 14 wk after injury, we correlated the reduction in fascicle length and increase in pennation angle with peak torque measured during isometric and isokinetic plantarflexor contractions. We found that the medial gastrocnemius underwent an immediate change in structure, characterized by decreased length and increased pennation of the muscle fascicles. This decrease in fascicle length was coupled with an increase in tendon length. These changes in muscle-tendon structure persisted throughout the first 14 wk following rupture. Deficits in peak plantarflexor torque were moderately correlated with decreased fascicle length at 120 degrees per second (R2 = 0.424, P = 0.057) and strongly correlated with decreased fascicle length at 210 degrees per second (R2 = 0.737, P = 0.003). However, increases in pennation angle did not explain functional deficits. These findings suggest that muscle-tendon structure is detrimentally affected following Achilles tendon rupture. Plantarflexor power deficits are positively correlated with the magnitude of reductions in fascicle length. Preserving muscle structure following Achilles tendon rupture should be a clinical priority to maintain plantarflexor kinetics.NEW & NOTEWORTHY In our study, we found that when the Achilles tendon ruptures due to excessive biomechanical loading, the neighboring skeletal muscle undergoes rapid changes in its configuration. The magnitude of this muscle remodeling explains the amount of ankle power loss demonstrated by these patients once their Achilles tendons are fully healed. These findings highlight the interconnected relationship between muscle and tendon. Isolated injuries to the tendon stimulate detrimental changes to the muscle, thereby limiting joint-level function.

Postural adaptations to repeated optic flow stimulation in older adults.

The purpose of this study is to understand the processes of adaptation (changes in within-trial postural responses) and habituation (reductions in between-trial postural responses) to visual cues in older and young adults. Of particular interest were responses to sudden increases in optic flow magnitude. The postural sway of 25 healthy young adults and 24 healthy older adults was measured while subjects viewed anterior-posterior 0.4 Hz sinusoidal optic flow for 45 s. Three trials for each of three conditions were performed: (1) constant 12 cm optic flow amplitude (24 cm peak-to-peak), (2) constant 4 cm amplitude (8 cm p-t-p), and (3) a transition in amplitude from 4 to 12 cm. The average power of head sway velocity (P(vel)) was calculated for consecutive 5s intervals during the trial to examine the changes in sway within and between trials. A mixed factor repeated measures ANOVA was performed to examine the effects of subject Group, Trial, and Interval on the P(vel). P(vel) was greater in older adults in all conditions (p<0.001). During the 12 cm constant amplitude trials, within-trial adaptation occurred for all subjects, but there were differences in the between-trial habituation. P(vel) of the older adults decreased significantly between all 3 trials, but decreased only between Trials 1 and 2 in young adults. While the responses of the young adults to the transition in optic flow from 4 to 12 cm did not significantly change, older adults had an increase in P(vel) following the transition, ranging from 6.5 dB for the first trial to 3.4 dB for the third trial. These results show that older adults can habituate to repeated visual perturbation exposures; however, this habituation requires a greater number of exposures than young adults. This suggests aging impacts the ability to quickly modify the relative weighting of the sensory feedback for postural stabilization.

Comparison of Head Impact Exposure Between Male and Female High School Ice Hockey Athletes.

BACKGROUND: Concussion incidence rates are higher among female than male athletes in sports played by both sexes. Biomechanical factors may play a role in observed sex-based differences in concussion incidence. PURPOSE: To compare head impact counts and magnitudes during sports participation between male and female high school ice hockey athletes. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Over 2 seasons, a total of 21 male and 19 female ice hockey athletes from a single high school were instrumented with impact-sensing adhesive skin patches worn over the mastoid process while participating in games and practices. The impact sensors recorded the number, magnitude (peak linear acceleration [PLA, g] and peak angular acceleration [PAA, rad/s2] of the head; Head Impact Telemetry severity profile [HITsp]), and location of impacts sustained during each instrumented session. Head impact counts, magnitudes, and locations were compared between the sexes. RESULTS: Males experienced more head impacts than females during games (mean ± SD: 7.7 ± 3.0 vs 5.3 ± 2.0, P < .001) as well as practices (4.3 ± 1.6 vs 3.8 ± 1.1, P = .002). Mean impact magnitudes were greater for females for PLA (18.8 g ± 1.7 g vs 17.1 g ± 1.6 g, P < .001) and HITsp (19.7 ± 1.5 vs 17.7 ± 1.4, P < .001), while mean PAA was greater for males (3057.6 ± 2.0 rad/s2 vs 2778.3 ± 2.7 rad/s2, P < .001). Female athletes experienced higher PLA, PAA, and HITsp magnitudes for the top 10%, 5%, and 1% of impacts (all P < .050). Males experienced more impacts to the front (34.3%) and back (31.7%) of the head, while females experienced more impacts to the side (43.1%) and top (4.1%) (χ2 = 295.70, df = 3, P < .001). CONCLUSION: While male high school ice hockey athletes experienced more head impacts than females, impact magnitudes tended to be higher for females.

Effect of epileptiform abnormality burden on neurologic outcome and antiepileptic drug management after subarachnoid hemorrhage.

OBJECTIVE: To quantify the burden of epileptiform abnormalities (EAs) including seizures, periodic and rhythmic activity, and sporadic discharges in patients with aneurysmal subarachnoid hemorrhage (aSAH), and assess the effect of EA burden and treatment on outcomes. METHODS: Retrospective analysis of 136 high-grade aSAH patients. EAs were defined using the American Clinical Neurophysiology Society nomenclature. Burden was defined as prevalence of <1%, 1-9%, 10-49%, 50-89%, and >90% for each 18-24 hour epoch. Our outcome measure was 3-month Glasgow Outcome Score. RESULTS: 47.8% patients had EAs. After adjusting for clinical covariates EA burden on first day of recording and maximum daily burden were associated with worse outcomes. Patients with higher EA burden were more likely to be treated with anti-epileptic drugs (AEDs) beyond the standard prophylactic protocol. There was no difference in outcomes between patients continued on AEDs beyond standard prophylaxis compared to those who were not. CONCLUSIONS: Higher burden of EAs in aSAH independently predicts worse outcome. Although nearly half of these patients received treatment, our data suggest current AED management practices may not influence outcome. SIGNIFICANCE: EA burden predicts worse outcomes and may serve as a target for prospective interventional controlled studies to directly assess the impact of AEDs, and create evidence-based treatment protocols.

Descriptive Analysis of a Baseline Concussion Battery Among U.S. Service Academy Members: Results from the Concussion Assessment, Research, and Education (CARE) Consortium.

Introduction: The prevalence and possible long-term consequences of concussion remain an increasing concern to the U.S. military, particularly as it pertains to maintaining a medically ready force. Baseline testing is being used both in the civilian and military domains to assess concussion injury and recovery. Accurate interpretation of these baseline assessments requires one to consider other influencing factors not related to concussion. To date, there is limited understanding, especially within the military, of what factors influence normative test performance. Given the significant physical and mental demands placed on service academy members (SAM), and their relatively high risk for concussion, it is important to describe demographics and normative profile of SAMs. Furthermore, the absence of available baseline normative data on female and non-varsity SAMs makes interpretation of post-injury assessments challenging. Understanding how individuals perform at baseline, given their unique individual characteristics (e.g., concussion history, sex, competition level), will inform post-concussion assessment and management. Thus, the primary aim of this manuscript is to characterize the SAM population and determine normative values on a concussion baseline testing battery. Materials and Methods: All data were collected as part of the Concussion Assessment, Research and Education (CARE) Consortium. The baseline test battery included a post-concussion symptom checklist (Sport Concussion Assessment Tool (SCAT), psychological health screening inventory (Brief Symptom Inventory (BSI-18) and neurocognitive evaluation (ImPACT), Balance Error Scoring System (BESS), and Standardized Assessment of Concussion (SAC). Linear regression models were used to examine differences across sexes, competition levels, and varsity contact levels while controlling for academy, freshman status, race, and previous concussion. Zero inflated negative binomial models estimated symptom scores due to the high frequency of zero scores. Results: Significant, but small, sex effects were observed on the ImPACT visual memory task. While, females performed worse than males (p < 0.0001, pη2 = 0.01), these differences were small and not larger than the effects of the covariates. A similar pattern was observed for competition level on the SAC. There was a small, but significant difference across competition level. SAMs participating in varsity athletics did significantly worse on the SAC compared to SAMs participating in club or intramural athletics (all p's < 0.001, η2 = 0.01). When examining symptom reporting, males were more than two times as likely to report zero symptoms on the SCAT or BSI-18. Intramural SAMs had the highest number of symptoms and severity compared to varsity SAMs (p < 0.0001, Cohen's d < 0.2). Contact level was not associated with SCAT or BSI-18 symptoms among varsity SAMs. Notably, the significant differences across competition level on SCAT and BSI-18 were sub-clinical and had small effect sizes. Conclusion: The current analyses provide the first baseline concussion battery normative data among SAMs. While statistically significant differences may be observed on baseline tests, the effect sizes for competition and contact levels are very small, indicating that differences are likely not clinically meaningful at baseline. Identifying baseline differences and significant covariates is important for future concussion-related analyses to inform concussion evaluations for all athlete levels.

Individual Impact Magnitude vs. Cumulative Magnitude for Estimating Concussion Odds.

Helmeted impact devices have allowed researchers to investigate the biomechanics of head impacts in vivo. While increased impact magnitude has been associated with greater concussion risk, a definitive concussive threshold has not been established. It is likely that concussion risk is not determined by a single impact itself, but a host of predisposing factors. These factors may include genetics, fatigue, and/or prior head impact exposure. The objective of the current paper is to investigate the association between cumulative head impact magnitude and concussion risk. It is hypothesized that increased cumulative magnitudes will be associated with greater concussion risk. This retrospective analysis included participants that were recruited from regional high-schools in Illinois and Michigan from 2007 to 2014 as part of an ongoing study on concussion biomechanics. Across seven seasons, 185 high school football athletes were instrumented with the Head Impact Telemetry system. Out of 185 athletes, 31 (17%) sustained a concussion, with two athletes sustaining two concussions over the study period, yielding 33 concussive events. The system recorded 78,204 impacts for all concussed players. Linear acceleration, rotational acceleration, and head impact telemetry severity profile (HITsp) magnitudes were summed within five timeframes: the day of injury, three days prior to injury, seven days prior to injury, 30 days prior to injury, and prior in-season exposure. Logistic regressions were modeled to explain concussive events based on the singular linear acceleration, rotational acceleration, and HITsp event along with the calculated summations over time. Linear acceleration, rotational acceleration, and HITsp all produced significant models estimating concussion (p < 0.05). The strongest estimators of a concussive impact were the linear acceleration (OR = 1.040, p < 0.05), rotational acceleration (OR = 1.001, p < 0.05), and HITsp (OR = 1.003, p < 0.05) for the singular impact rather than any of the cumulative magnitude calculations. Moreover, no cumulative count measure was significant for linear or rotational acceleration. Results from this investigation support the growing literature indicating cumulative magnitude is not related to concussion likelihood. Cumulative magnitude is a simplistic measure of the total exposure sustained by a player over a given period. However, this measure is limited as it assumes the brain is a static structure unable to undergo self-repair. Future research should consider how biological recovery between impacts may influence concussion risk.