A Pilot Study Investigating the Use of serum GFAP to Monitor Changes in Brain White Matter Integrity after Repetitive Head Hits During a Single Collegiate football game

Repetitive head hits (RHHs) in sports and military settings are increasingly recognized as a risk factor for adverse neurologic outcomes, but they are not currently tracked. Blood-based biomarkers of concussion have recently been shown to increase after non-concussive RHHs during a single sporting contest, raising the possibility that they could be used in real-time to monitor the brain's early response to repeated asymptomatic head hits. In order to test this hypothesis, we measured GFAP in serum immediately before (T0), immediately after (T1) and 45 minutes (T2) after a single collegiate football game in 30 athletes. GFAP changes were correlated to 3 measures of head impact exposure (number of hits, total linear acceleration, and total rotational acceleration captured by helmet impact sensors) and to changes in brain white matter (WM) integrity, estimated by regional changes in fractional anisotropy (FA) and mean diffusivity (MD) on diffusion tensor imaging from 24 hours before (T-1) to 48 hours after (T3) the game). To account for the potentially confounding effects of physical exertion on GFAP, correlations were adjusted for kilocalories of energy expended during the game measured by wearable body sensors. All 30 participants were male with a mean age of 19.5+1.2 years. No participant had a concussion during the index game. We observed a significant increase in GFAP from T0 to T1 (mean 79.69 vs 91.95 pg/mL, p=0.008) and from T0 to T2 (mean 79.69 vs 99.21 pg/mL, p<0.001). White matter integrity decreased in multiple WM regions but was statistically significant in the right fornix (mean % FA change -1.43, 95% CI:-2.20, -0.66). T0 to T2 increases in GFAP correlated with reduced FA in the left fornix, right fornix, and right medical meniscus, and with increased MD in the right fornix (|r-values| ranged from 0.59-0.61). Adjustment for exertion had minimal effect on these correlations. GFAP changes did not correlate to head hit exposure, but after adjustment for exertion, T0 to T2 increases correlated with all three hit metrics (r-values ranged from 0.69-0.74). Thus, acute elevations in GFAP after a single collegiate football game of RHHs correlated with in-game head hit exposure and with reduced WM integrity 2 days later. These results suggest that GFAP may be a biologically relevant indicator of the brain's early response to RHHs during a single sporting event. Developing tools to measure the neurologic response to RHHs on an individual level has the potential to provide insight into the heterogeneity in adverse outcomes after RHH exposure and for developing effective and personalized countermeasures. Due to small sample size, these findings should be considered preliminary; validation in a larger, independent cohort is necessary.

Social Determinants of Health and Health Equity in the Treatment and Rehabilitation of Sport-Related Concussion: A Content Analysis of Intervention Research and Call-To-Action

This review was designed to (i) determine the extent to which the clinical science on sport-related concussion treatment and rehabilitation has considered social determinants of health (SDoH) or health equity and (ii) offer recommendations to enhance the incorporation of SDoH and health equity in concussion treatment research and clinical care. The Concussion in Sport Group consensus statement (2023) was informed by two systematic reviews examining prescribed rest or exercise following concussion and targeted interventions to facilitate concussion recovery. We examined 31 studies, including 2,698 participants, from those two reviews. Race (k=6; 19.4%) and ethnicity (k=4; 12.9%) were usually not reported. Four studies examined ethnicity (i.e., Hispanic), exclusively as a demographic category. Five studies (16.1%) examined race as a demographic category. Three studies (9.7%) examined socioeconomic status (SES; measured as household income) as a demographic category/sample descriptor and one study (3.2%) examined SES in depth, by testing whether the treatment and control groups differed by SES. Five studies examined a SDoH domain in a descriptive manner and four studies in an inferential/intentional manner. No study mentioned SDoH, health equity, or disparities by name. Many studies (61.3%) excluded participants based on demographic, sociocultural, or health factors, primarily due to language proficiency. The new consensus statement includes recommendations for concussion treatment and rehabilitation that rely on an evidence base that has not included SDoH or studies addressing health equity. Researchers are encouraged to design treatment and rehabilitation studies that focus specifically on under-represented groups to determine if they have specific and unique treatment and rehabilitation needs, whether certain practical modifications to treatment protocols might be necessary, and whether completion rates and treatment adherence and response are similar.

White Matter Hyperintensities and Microstructural Alterations in Contact Sport Athletes from Adolescence to Early Midlife

Studies have demonstrated associations between cumulative concussion and repetitive head impact exposure (RHI) via contact sports with white matter (WM) alterations later in life. The course of WM changes associated with exposure earlier in the lifespan are unclear. This study investigated alterations in white matter (WM hyperintensity [WMH] volume and microstructural changes) associated with concussion and RHI exposure from adolescence to early midlife, as well as the interaction between exposure and age-cohort (i.e., adolescent/young adult compared to early midlife athlete cohorts) on WM outcomes. Participating football players included an adolescent/young adulthood cohort (n=82; Mage=18.41.7) and an early midlife cohort (37 former collegiate players approximately 15-years removed from sport; Mage=37.71.4). Years of football participation and number of prior concussions were exposures of interest. White matter outcomes included log-transformed manually segmented total WMH volume and neurite orientation dispersion and density imaging metrics of microstructure/organization (isotropic volume fraction[Viso], intra-cellular volume fraction[Vic], and orientation dispersion[OD]). Regression models were fit to test effects of concussion history, years of football participation, and age-cohort by years of football participation with WM outcomes. Spearman's correlations assessed associations between significant WM metrics and measures of cognitive and psychological function. A significant age-cohort by years of participation effect was observed for whole brain white matter OD, B=-0.002, SE=0.001, p=0.001. The interaction was driven by a negative association between years of participation and OD within the younger cohort, B=-0.001, SE=0.0004, p=0.008, whereas a positive association between participation and OD in the early midlife cohort, B=0.001, SE=0.0003, p=0.039, was observed. Follow-up ROI analyses showed significant interaction effects for OD in the body of the corpus callosum, genu of the corpus callosum, cingulum, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, posterior thalamic radiation (ps<0.05). Greater concussion history was significantly associated with greater Viso in the early midlife cohort, B=0.001, SE= 0.0002, p=0.010. Years of participation and concussion history were not associated with WMH volume, ps>0.05. Performance on a measure of executive function was significantly associated with years of participation, =.34, p=.04, and a trend was observed for OD, =.28, p=.09 in the early midlife cohort only. The global characterization of white matter changes associated with years of football participation were broadly similar and stable from adolescence through early midlife (i.e., microstructural alterations, but not macroscopic lesions). An inverse association between years of participation and orientation dispersion across age-cohorts may represent a process of initial recovery/reorganization proximal to sport, followed by later reduction of white matter coherence.

Psychological Predictors of Mental Health Difficulties after Pediatric Concussion

Children often experience mental health difficulties after a concussion. Yet, the extent to which a concussion precipitates or exacerbates mental health difficulties remains unclear. This study aimed to examine psychological predictors of mental health difficulties after pediatric concussion. Children (aged 5 to <18 years, M=11.7, SD=3.3) with concussion were recruited in a single-site longitudinal prospective cohort study conducted at a tertiary children's hospital (n=115, 73.9% male). The primary outcomes included internalizing (anxious, depressed, withdrawn behaviors), externalizing (risk-taking, aggression, attention difficulties), and total mental health problems, as measured by the Child Behavior Checklist at two weeks (acute) and three months (post-acute) after concussion. Predictors included parents' retrospective reports of premorbid concussive symptoms (Post-Concussion Symptom Inventory; PCSI), the child and their family's psychiatric history, child-rated perfectionism (Adaptive-Maladaptive Perfectionism Scale), and child-rated resilience (Youth Resilience Measure). Higher premorbid PCSI ratings consistently predicted acute and post-acute mental health difficulties. This relationship was significantly moderated by child psychiatric history. Furthermore, pre-injury learning difficulties, child psychiatric diagnoses, family psychiatric history, lower resilience, previous concussions, female sex, and older age at injury were associated with greater mental health difficulties after concussion. Pre-injury factors accounted for 23.4-39.9% of acute mental health outcomes, and 32.3-37.8% of post-acute mental health outcomes. When acute mental health was factored into the model, a total of 47.0%-68.8% of variance was explained by the model. Overall, in this sample of children, several pre-injury demographic and psychological factors were observed to predict mental health difficulties after a concussion. These findings need to be validated in future research involving larger, multi-site studies that include a broader cohort of children after concussion.

Emergency Department Risk Factors for Post-Concussion Syndrome After Mild Traumatic Brain Injury: A Systematic Review

Around 16% of patients with mild traumatic brain injury (mTBI) develop a post-concussion syndrome (PCS) with persistent physical, neurological and behavioural complaints. PCS has a great impact on a patient's quality of life, often decreases the ability to return to work, and henceforth has a great economic impact. Recent studies suggest that early treatment can greatly improve prognosis and prevent long-term effects in these patients. However, early recognition of patients at high risk of PCS remains difficult. The objective of this systematic review is to assess risk factors associated with the development of PCS, it primarily aims at the group of non-hospitalized patients who were seen with mTBI at the Emergency Department (ED). We searched PubMed/MEDLINE, Cochrane Library and EMBASE on 23-09-2022 for prospective studies which assessed the risk factors for the development of PCS. Exclusion criteria were: retrospective studies, >20% CT abnormalities, <18 years of age, follow-up < four weeks, severe trauma, and study population <100 patients. The search strategy identified 1628 articles, of which 17 studies met eligibility criteria. Risk factors found in this systematic review are pre-existing psychiatric history, headache at the ED, neurological symptoms at the ED, female sex, CT abnormalities, pre-existent sleeping problems, and neck pain at the ED. This systematic review identified seven risk factors for development of PCS in patients with mTBI. Future research should assess if implementation of these risk factors into a risk stratification tool will assist the emergency physician in the identification of patients at high risk of PCS.

Prior Concussion History and Clinical Recovery Following Sport-Related Concussion in High School Athletes

Clinical recovery following sport-related concussion varies as a function of preinjury and acute factors. Whether, or the extent to which, concussion history is associated with clinical outcome following sport-related concussion is uncertain, as research has produced mixed findings. The present study aimed to assess whether a history of prior concussions is associated with prolonged clinical recovery following a subsequent sport-related concussion. The sample was comprised of 780 adolescent student athletes (mean age= M=16.3, SD=1.3 years; 56.8% boys, 43.2% girls) whose school participated in the Maine Concussion Management Initiative (MCMI). Survival analyses were used to compare recovery times among adolescents with a history of 0, 1, or 2 prior concussions following a subsequent sport-related concussion. The two primary outcomes of interest were the number of days to return to school and sports. There were no statistically significant differences in total time to return to school and sports, or the proportion of adolescents who returned to school and sports at most intervals (e.g., 7, 14, 28 days), between those with 0, 1, or 2 prior concussions. However, a greater proportion of adolescents with a history of 2 prior concussions remained out of sports at 28 days as compared to those with no prior concussions (23.5% vs. 12.7%; OR=2.10, 95% CI 1.18-3.73). Having sustained prior concussions was not associated with time to return to school following a subsequent sport-related concussion. However, a greater proportion of adolescents with two or more prior concussions experienced a prolonged return to sports. Further research is warranted to identify risk factors for worse outcomes among the subset of adolescents with a history of multiple prior concussions who experience prolonged recoveries.

Shorter recovery time in concussed elite ice hockey players by early head-and-neck cooling - a clinical trial

A sports-related concussion (SRC) is most commonly sustained in contact sports, and is defined as a mild traumatic brain injury. An exercise-induced elevation of core body temperature is associated with increased brain temperature that may accelerate secondary injury processes following SRC, and exacerbate the brain injury. In a recent pilot study, acute head-neck cooling of 29 concussed ice hockey players resulted in shorter time to return-to-play. Here, we extended the clinical trial to include players of 19 male elite Swedish ice hockey teams over 5 seasons (2016-2021). In the intervention teams, acute head-neck cooling was implemented using a head cap for ≥45 minutes in addition to the standard SRC management used in controls. The primary endpoint was time from SRC until return-to-play (RTP). Sixty-one SRCs were included in the intervention group and 71 SRCs in the control group. The number of previous SRCs was 2 (median and interquartile range (IQR): 1.0 - 2.0) and 1 (IQR 1.0 - 2.0) in the intervention and control groups, respectively; p= 0.293. Median time to initiate head-neck cooling was 10 min (IQR 7-15; range 5-30 min) and median duration of cooling was 45 min (IQR 45-50; range 45-70 min). The median time to RTP was 9 days in the intervention group (IQR 7-13.5 days) and 13 days in the control group (IQR 9-30; p<0.001). The proportion of players out from play for more than the expected recovery time of 14 days was 24.7% in the intervention group, and 43.7% in controls (p<0.05). Study limitations include that a) allocation to cooling or control management was at the discretion of the medical staff of each teams, decided prior to each season, and not by strict randomization, b) no sham cap was used and evaluations could not be performed by blinded assessors and c) it could not be established with certainty that injury severity was similar between groups. While the results should thus be interpreted with caution, early head-neck cooling, with the aim of attenuating cerebral hyperthermia, may reduce post-SRC symptoms and lead to earlier return-to-play in elite ice hockey players.

Impact of Chronological Age and Biological Sex on Cerebrovascular Reactivity in Moderate/Severe Traumatic Brain Injury: A CAnadian High-Resolution TBI (CAHR-TBI) Study

Impaired cerebrovascular reactivity has emerged as an important associate with poor long-term outcome after moderate/severe traumatic brain injury (TBI). However, our understanding of what drives or modulates the degree of impaired cerebrovascular function remains poor. Age and biological sex remain important modifiers of cerebrovascular function in health and disease, yet their impact on cerebrovascular reactivity after TBI remains unclear. The aim of this study was to explore subgroup responses based on age and biological sex on cerebral physiology. Data from 283 TBI patients from the CAnadian High Resolution TBI (CAHR-TBI) Research Collaborative were evaluated. Cerebrovascular reactivity was determined using high-frequency cerebral physiology for the derivation of three intracranial pressure (ICP) based indices: (1). PRx - correlation between ICP and mean arterial pressure (MAP), (2). PAx - correlation between pulse amplitude of ICP (AMP) and MAP and (3). RAC - correlation between AMP and cerebral perfusion pressure (CPP). Insult burden (% time above clinically defined thresholds) were calculated for these indices. These cerebral physiology indices were studied for their relationship with age via linear regression, age trichotomization (< 40, 40 - 60, > 60) and decades of age (< 30, 30 - 39, 40 - 49, 50 - 59, 60 - 69, > 69) schemes. Similarly, differences based on biological sex were assessed. A statistically significant positive linear correlation was found between PAx, RAC and age. In corollary, a statistically significant relationship was found between increasing age on trichotomized and decades of age analysis with PAx and RAC measures. PRx failed to demonstrate such relationships to advancing age. There was no clear difference in cerebrovascular reactivity profiles between biological sex categories. These findings suggest that AMP-based cerebrovascular reactivity indices may be better positioned to detect impairment in TBI patients with advancing age. Further investigation into the utility of PAx and RAC is required, as they may prove useful for certain subgroups of patients.

Magnetic resonance spectroscopy of traumatic brain injury and subconcussive hits: A systematic review and meta-analysis

Magnetic resonance spectroscopy (MRS) is a non-invasive technique used to study metabolites in the brain. MRS findings in traumatic brain injury (TBI) and subconcussive hit literature have been mixed. The most common observation is a decrease in N-acetyl-aspartate (NAA), traditionally considered a marker of neuronal integrity. Other metabolites, however, such as creatine (Cr), choline (Cho), glutamate+glutamine (Glx) and myo-inositol (mI) have shown inconsistent changes in these populations. The objective of this systematic review and meta-analysis was to synthesize MRS literature in head injury and explore factors (brain region, injury severity, time since injury, demographic, technical imaging factors, etc.) that may contribute to differential findings. One hundred and thirty-eight studies met inclusion criteria for the systematic review and of those, 62 NAA, 24 Cr, 49 Cho, 18 Glx and 21 mI studies met inclusion criteria for meta-analysis. A random effects model was used for meta-analyses with brain region as a subgroup for each of the five metabolites studied. Meta-regression was used to examine the influence of potential moderators including injury severity, time since injury, age, sex, tissue composition and methodological factors. In this analysis of 1428 unique head-injured subjects and 1132 controls, the corpus callosum was identified as a brain region highly susceptible to metabolite alteration. NAA was consistently decreased in TBI of all severity, but not in subconcussive hits. Cho and mI were found to be increased in moderate-to-severe TBI but not mild TBI. Glx and Cr were largely unaffected, however did show alterations in certain conditions.

Cerebral Autoregulation Monitoring in Traumatic Brain Injury: An Overview of Recent Advances in Personalized Medicine

Impaired cerebral autoregulation (CA) in moderate/severe traumatic brain injury (TBI) has been identified as a strong associate with poor long-term outcomes, with recent data highlighting its dominance over cerebral physiologic dysfunction seen in the acute phase post injury. With advances in bedside continuous cerebral physiologic signal processing, continuously derived metrics of CA capacity have been described over the past two decades, leading to improvements in cerebral physiologic insult detection and development of novel personalized approaches to TBI care in the intensive care unit (ICU). This narrative review focuses on highlighting the concept of continuous CA monitoring and consequences of impairment in moderate/severe TBI. Further, we provide a comprehensive description and overview of the main personalized cerebral physiologic targets, based on CA monitoring, that are emerging as strong associates with patient outcomes. CA-based personalized targets, such as optimal cerebral perfusion pressure (CPPopt), lower/upper limit of regulation (LLR/ULR), and individualized intra-cranial pressure (iICP) are positioned to change the way we care for TBI patients in the ICU, moving away from the "one treatment fits all" paradigm of current guideline-based therapeutic approaches, towards a true personalized medicine approach tailored to the individual patient. Future perspectives regarding research needs in this field are also discussed.

Letter to the Editor - Bodien et al

Bodien et al (1) note that the Glasgow Coma Scale (GCS) is the most widely used behavioural measure for assessment of acute head injury severity. We welcome the support they express for reporting the findings separately for its 3 component subscales. In contrast, their portrayal of supposed limitations of the aggregate Coma Score is flawed and based on criticisms for not doing something it was never intended to do.

Females Exhibit Better Cerebral Pressure Autoregulation, Less Mitochondrial Dysfunction, and Reduced Excitotoxicity following Severe Traumatic Brain Injury

The aim of the study was to investigate sex-related differences in intracranial pressure (ICP) dynamics, cerebral pressure autoregulation (PRx55-15), cerebral energy metabolism, and clinical outcome after severe traumatic brain injury (TBI). One-hundred sixty-nine adult TBI patients, treated at the neurointensive care (NIC) unit, at Uppsala University Hospital, 2008-2020, with ICP and cerebral microdialysis (MD) monitoring, were included. Of the 169 TBI patients, 131 (78%) were male and 38 (22%) female. Male patients were more often injured by motor vehicle accidents and less often by bicycle accidents (p < 0.05). There were otherwise no difference in age, neurological status at admission, and types of intracranial hemorrhages between the sexes. The percent of monitoring time with ICP above 20 mmHg and CPP below 60 mmHg were similar for both sexes. Males exhibited more disturbed cerebral pressure autoregulation (PRx55-15 (mean ± SD); 0.28 ± 0.18 vs. 0.17 ± 0.23, p < 0.05) day 1, worse cerebral energy metabolism (MD-lactate-/pyruvate-ratio (median (IQR)); 25 (19-31) vs. 20 (17-25), p < 0.01) and mitochondrial dysfunction (higher burden of MD-LPR > 25 and MD-pyruvate > 120 µM (median (IQR)); 13 (0-58) % vs. 3 (0-17) %, p < 0.05) day 2 to 5, increased excitotoxicity (MD-glutamate median (IQR); 9 (4-32) µM vs. 5 (3-10) µM, p < 0.05) day 2 to 5, and higher biomarker levels of cellular injury (MD-glycerol median (IQR); 103 (66-193) µM vs. 68 (49-106) µM, p < 0.01) most pronounced day 6 to 10. There was no difference in mortality or the degree of favorable outcome between the sexes. Altogether, females exhibited more favorable cerebral physiology post-TBI, particularly better mitochondrial function and reduced excitotoxicity, but this did not translate into better clinical outcome compared to males. Future studies needs to further explore potential sex differences in secondary injury mechanisms in TBI.

Interleukin-4 reduces lesion volume and improves neurological function in the acute phase after experimental traumatic brain injury in mice

Little is known about the impact of Interleukin-4 (IL-4) on secondary brain damage in the acute phase after experimental traumatic brain injury (TBI). Therefore, we evaluated the effect of IL-4-Knockout on structural damage as well as functional impairment in the acute phase after experimental TBI in mice. 28 C57Bl/6 wildtype and 20 C57BL/6-Il4tm1Nnt/J Interleukin-4-Knockout (IL-4-KO) mice were subjected to Controlled Cortical Impact (CCI). Contusion volumes, body weight and functional outcome (Video Open Field Test (VOF), Hole Board Test (HB), CatWalkXT®) were determined on postoperative days one (D1), three (D3) and seven (D7). Contusion volume (13.45 +/- 0.88 mm³ vs. 9.50 +/- 0.97 mm³, p=0.015) and weight loss (-2.92 +/- 0.52% vs. -0.85 +/- 0.67%, p=0.027) were significantly higher and exploration behavior significantly more impaired (e.g., 150.44 +/- 18.71 fields explored vs. 211.56 +/- 18.90 fields explored, p=0.028 in the VOF; 23.31 +/- 2.03 holes explored vs. 35.65 +/- 1.93 holes explored, p<0.001 in the HB) in IL-4-KO mice on D1. Gait impairment was significantly more pronounced in IL-4-KO mice throughout the first week after CCI (e.g., 0.07 +/- 0.01s vs. 0.00 +/- 0.01s, p=0.047 for right hindpaw Swing on D1; -1.76 +/- 1.34 U vs. 2.53 +/- 0.90 U, p=0.01 for right forepaw Mean Intensity on D3; -0.01 +/- 0.01cm² vs. 0.05 +/- 0.01cm², p=0.015 for left forepaw Mean Area on D7). In conclusion, IL-4 reduces structural damage and improves functional outcome in the acute phase after CCI. Neurobehavioral outcome assessment in IL-4-related studies should focus on motor function on the first three days after trauma induction.

Clinical Outcome Following Sport-Related Concussion Among Children and Adolescents with a History of Prior Concussion: A Systematic Review

Authoritative sources advise clinicians and parents that a history of prior concussion confers increased risk for worse outcome from a future concussion. However, the strength of the evidence supporting such pronouncements and thus the extent to which clinicians should incorporate this information into their care and management of pediatric concussion is unclear. This systematic review critically analyzed and synthesized the literature on the association between a history of prior concussion and prognosis/clinical outcome following a subsequent sport-related concussion among children and adolescents. The online databases PubMed, MEDLINE®, PsycINFO®, CINAHL, Cochrane Library, EMBASE, SPORTDiscus, Scopus, and Web of Science were searched from inception to May 15, 2021. From 5,118 total records screened, 51 studies (46 cohort studies and 5 case-control studies) met inclusion criteria, reporting concussion recovery or outcome for 26,643 youth. A median of 36% had a prior history of concussion. Across all studies and outcomes, the majority (k=37, 72.5%) did not find a statistically significant association between lifetime history of concussion and outcome from a subsequent concussion. Important methodological limitations in the literature were identified. Available studies do not provide consistent or compelling evidence that children and adolescents with a history of concussions are at increased risk for worse clinical outcome following a subsequent sport-related concussion-although methodological limitations temper the strength of this conclusion. Clinicians are cautioned against routinely treating children and adolescents with one or more prior injuries differently, and more conservatively, because doing so, in some cases, might be counterproductive.

Presence of persistent parent reported emotional and behavioral-related concussion symptoms is associated with lower health-related quality of life in adolescent athletes

Persistent concussion symptoms in adolescents are associated with lower health-related quality of life (HRQOL). However, the association between persistent emotional and behavioral-related concussion symptoms (EBS) and HRQOL is unknown. This study was a prospective cohort of adolescent athletes presenting to a concussion clinic within three days post-concussion and completing a one-month follow up. The independent variable in these analyses was parent reported EBS symptom presence grouped as: 1) no EBS; 2) EBS present at pre-concussion levels; and 3) EBS worse than pre-concussion. EBS included the following concussion symptoms: feeling irritable, depressed, frustrated/impatient, restless, reduced tolerance to stress/emotion, poor concentration, and fear of permanent symptoms. Dependent variables were parent reported psychosocial, physical, and total HRQOL. Separate multivariable linear regression models controlling for age, sex, and concussion history were used to assess the association between EBS and HRQOL. Estimated adjusted mean differences (MD) and 95% confidence intervals (CI) were used to assess associations; MDs with a 95%CI excluding 0.0 were considered statistically significant. Overall, n=245 presented to the study clinic three days post-concussion and completed the one-month follow-up (Mage=14.28±2.09 years, 59.02% male, 90.64% Caucasian, 31.84% with concussion history). At one-month post-concussion, adolescents with pre-concussion EBS levels had significantly lower psychosocial, physical, and total HRQOL than those with no EBS. Additionally, those with EBS worse than pre-concussion had significantly lower psychosocial, physical, and total HRQOL than those with no EBS and EBS at pre-concussion levels. These findings highlight the importance of HRQOL assessments and that targeted interventions may be needed for those with EBS at one-month post-concussion to improve HRQOL.

Decompressive craniectomy practice following traumatic brain injury, in comparison with randomized trials

High quality evidence shows decompressive craniectomy (DC) following traumatic brain injury (TBI) may improve survival but increase the number of severely disabled survivors. Contemporary international practice is unknown. We sought to describe international use of DC, and the alignment with evidence and clinical practice guidelines, by analyzing the harmonized CENTER-TBI and OzENTER-TBI Core study datasets. These include patients admitted to ICUs in Europe, the United Kingdom and Australia between 2015 and 2017. Outcomes of interest were treatment with DC relative to clinical trial evidence and the Brain Trauma Foundation guidelines. Of 2336 people admitted to ICUs following TBI, DC was performed in 320 (13.7%): in 64/1422 (4.5%) patients with diffuse TBI, and 195/640 (30.5%) patients with traumatic mass lesions. Secondary DC (for treatment of intracranial hypertension) was used infrequently in patients who met enrolment criteria of the two randomised clinical trials informing the guidelines: in 11/124 (8.9%) of those matching DECRA enrolment, and in 30/224 (13.4%) of those matching RESCUEicp. Of patients who underwent DC 258/320 (80.6%) were ineligible for either trial: 149/320 (46.6%) underwent primary DC, 62/320 (19.4%) were outside the trials' age criteria, and 126/320 (39.4%) did not develop intracranial hypertension refractory to non-operative therapies prior to DC. Secondary DC was used infrequently in patients in whom it had been shown to be potentially harmful, indicating alignment between contemporaneous evidence and practice. However, most patients who underwent DC were ineligible for the key trials; whether they benefitted from DC remains unknown.

Neuroimaging correlates of depression after traumatic brain injury: A systematic review

Depression is the most frequent neuropsychiatric complication after traumatic brain injury (TBI) and is associated with poorer outcomes. Neuroimaging has the potential to improve our understanding of the neural correlates of depression after TBI and may improve our capacity to accurately predict and effectively treat this condition. We conducted a systematic review of structural and functional neuroimaging studies that examined the association between depression after TBI, and neuroimaging measures. Electronic searches were conducted in four databases and were complemented by manual searches. In total, 2,035 citations were identified and, ultimately, 38 articles were included totaling 1,793 individuals (median [25%-75%] sample size of 38.5 (21.8-54.3) individuals). The most frequently used modality was structural magnetic resonance imaging (MRI) (n=17, 45%), followed by diffusion tensor imaging (n=11, 29%), resting-state functional MRI (n=10, 26%), task-based functional MRI (n=4, 8%), and positron emission tomography (n=2, 4%). Most studies (n=27, 71%) were cross-sectional. Overall, depression after TBI was associated with lower grey matter measures (volume, thickness, and/or density) and greater white matter damage. However, identification of specific brain areas was somewhat inconsistent. Findings that were replicated in more than one study included reduced grey matter in the rostral anterior cingulate cortex, prefrontal cortex and hippocampus, and damage in five white matter tracts (cingulum, internal capsule, superior longitudinal fasciculi, anterior, and posterior corona radiata). This systematic review found that the available data did not converge on a clear neuroimaging biomarker for depression after TBI. However, there are promising targets that warrant further study.

Cervicovestibular Rehabilitation in Adults with Mild Traumatic Brain Injury: A Randomised Clinical Trial

The objective of this study was to compare the effects of a cervicovestibular rehabilitation program combined with symptom-limited aerobic exercise (SLAE) program to a SLAE program alone in adults with persistent symptoms following mild traumatic brain injury (mTBI) on severity of symptoms and other indicators of clinical recovery. In this single-blind, parallel-group randomised clinical trial, 60 adults with persistent symptoms following mTBI were randomly assigned to: 1) a 6-week SLAE program or 2) a 6-week cervicovestibular rehabilitation program combined with SLAE program. All participants took part in 4 evaluation sessions (baseline, week 6, 12 and 26) performed by a blinded evaluator. The primary outcome was the Post-Concussion Symptoms Scale (PCSS). The secondary outcomes were Numerical Pain Rating Scale (NPRS), Neck Disability Index (NDI), Headache Disability Inventory (HDI), Dizziness Handicap Inventory (DHI), time to return to function, and physical cervical and vestibular measures. Nonparametric analysis for longitudinal data was used to evaluate the effect of interventions on outcomes. For PCSS, NPRS, NDI, HDI, DHI and return to function, there were no group-by-time interactions at any time-points follow-up (p>0.05); clinically significant time effects were however observed (p0.05). There were group-by-time interactions at weeks 6 and 12 for vestibulo-ocular reflex (p0.003) and the cranio-vertebral mobility (p0.001) measures in favor of the cervicovestibular rehabilitation group. The study indicates that a cervicovestibular rehabilitation program combined with SLAE was not superior to a SLAE program alone in term of symptoms and functional level improvement but resulted in improved physical cervical and vestibular function. Keywords: mild traumatic brain injury, rehabilitation, neck pain, dizziness, headache.

Association between serum calcium level and hemorrhagic progression in patients with traumatic intraparenchymal hemorrhage: Investigating the mediation and interaction effects of coagulopathy

In this study, we investigate the association of serum calcium with coagulopathy and hemorrhagic progression contusion (HPC) in patients with traumatic intraparenchymal hemorrhage (tIPH), and further explored the interaction and mediation effect between serum calcium as well as coagulopathy on HPC. Retrospective analyses of patients with tIPH admitted to the First Affiliated Hospital of Wenzhou Medical University between January 2016 to December 2019. The clinical data, coagulation parameters, and serum calcium levels were collected for further analysis. Multivariate logistic regression analysis was applied to identify the association of serum calcium level with coagulopathy and HPC. Causal mediation analysis (CMA) and additive interaction model were used to estimate the interaction and mediation effect between serum calcium as well as coagulopathy on HPC. Additionally, we repeated the analysis using corrected calcium. A total of 473 patients were included in this study. Of these, 54 (11.4%) patients had hypocalcemia at admission, 105 (22.2%) presented with coagulopathy, and 187 (39.5%) experienced HPC. Admission serum calcium level in patients presented with coagulopathy and HPC were 8.84 [IQR: 8.44-9.40] and 8.92 [IQR: 8.48-9.40] mg/dL respectively, which were significantly lower than that of patients without (9.10 [IQR: 8.68-9.88] and 9.12 [IQR: 8.72-9.89] mg/dL; all p < 0.001). Multivariate logistic regression analysis identified that hypocalcemia emerged as an independent risk factor for coagulopathy and HPC. However, no significant interaction was detected between hypocalcemia and coagulopathy. CMA showed that the mediator coagulopathy explained 24.4% (95% CI: 4.7-65.0%; p = 0.006) of the association between hypocalcemia and HPC. Moreover, comparable results were held using corrected calcium as well. Admission serum calcium level is associated with the HPC for patients with tIPH and this relationship is partially mediated by coagulopathy, but no significant interaction is detected. Further studies are needed to validate the findings and explore its mechanisms.

Head impact exposure, grey matter volume, and moderating effects of estimated IQ and educational attainment in former athletes at midlife

Repetitive head impact (RHI) exposure has been associated with differences in brain structure among younger active athletes, most often within the hippocampus. Studies of former athletes at early-midlife are limited. We investigated the association between RHI exposure and grey matter structure, as well as moderating factors, among former athletes in early-midlife. Former collegiate football players (N=55; age=37.9+1.5 years) completed magnetic resonance imaging to quantify grey matter morphometry and extensive structured interviews of RHI history (Head Impact Exposure Estimate). Linear regression models tested the association between RHI exposure and GM structures of interest. Interactions were tested for moderators: two estimates of IQ (single word reading and picture vocabulary) and education history. Greater RHI exposure was associated with smaller hippocampal volume, β=-.36, p=.004. Conversely, RHI exposure was not significantly associated with other GM outcomes ps>.05. Education history significantly moderated the association between RHI exposure and hippocampal volume, β=.69, p=.047. Among those with a bachelor's degree, greater RHI exposure was significantly associated with smaller hippocampal volumes, β=-.58, p<.001. For those with graduate/professional degrees, the association between RHI and hippocampal volume was not significant, β=-.33, p=.134. Consistent with studies involving younger, active athletes, smaller hippocampal volumes were selectively associated with greater RHI exposure among former collegiate football players at midlife. This relationship was moderated by higher levels of education. Future longitudinal studies are needed to investigate the course of possible changes that can occur between early-midlife to older ages, as well as the continued protective effect of education and other potential influential factors.

Predicting Neurological Deterioration after Moderate Traumatic Brain Injury: Development and Validation of a Prediction Model Based on Data Collected on Admission

Moderate traumatic brain injury (mTBI) is a heterogeneous entity that poorly defined in the literature. mTBI patients suffer from a high rate of neurological deterioration (ND), which is usually accompanied with poor prognosis and no definitive methods to predict. The purpose of this study is to develop and validate a prediction model that estimates the ND risk in mTBI patients using data collected on admission. Retrospectively collected 479 mTBI patients' data in our department were analyzed by logistic regression models. Bivariable logistic regression identified variables with a p-value<0.05. Multivariable logistic regression modeling with backward stepwise elimination was used to determine reduced parameters and establish a prediction model. The discrimination efficacy, calibration efficacy, and clinical utility of the prediction model were evaluated. The prediction model was validated using 176 patients' data collected from another hospital. Eight independent prognostic factors were identified: hypertension, Marshall's scale (types III and IV), subdural hemorrhage (SDH), location of contusion (LOC) (frontal and temporal contusions), Injury Severity Score (ISS) >13, D-dimer level >11.4 mg/L, Glasgow Coma Scale (GCS) score ≤10, and platelet (PLT) count ≤152×109/L. A prediction model was established and was shown as a nomogram. Using bootstrapping, internal validation showed that the C-statistic of the prediction model was 0.881 (95% confidence interval (CI): 0.849-0.909). The results of external validation showed that the nomogram could predict ND with an area under the curve (AUC) of 0.827 (95% CI: 0763.-0.880). The present model, based on simple parameters collected on admission, can predict the risk of ND in mTBI patients accurately. The high discriminative ability indicates the potential of this model for classifying mTBI patients according to ND risk.

Repeated subconcussive exposure alters low-frequency neural oscillation in memory retrieval processing

Repeated subconcussive head impacts are frequently experienced by athletes involved in competitive sports, such as boxing. The objective of the present study was to investigate the changes in working memory performance and memory retrieval-related neural oscillations in boxing athletes who experienced repeated subconcussive head impacts. Twenty-one boxing athletes (boxing group) and twenty-five matched controls (control group) completed a modified visual working memory task, and their continuous scalp electroencephalography (EEG) data were collected simultaneously. The behavioral measures and retrieval-related low-frequency neural oscillations were analyzed at each working memory set size in both groups. Subjects in the boxing group showed a reduced mean accuracy, diminished capacity estimates, and slower reaction time at demanding set sizes and a marginally increased intraindividual coefficient of variation (ICV) for overall set sizes. Additionally, decreased event-related frontal theta synchronization, parieto-occipital alpha desynchronization, and frontal low beta synchronization were observed in the boxing group, suggesting underlying working memory dysfunction for efficient neurocognitive resource employment, inhibition of distracting stimuli, and post-retrieval control in the boxing group. Moreover, a negative correlation was found between frontal beta synchronization and reaction time for most set sizes in both groups. The present study was the first to reveal the underlying working memory deficits caused by the cumulative effects of boxing-related subconcussive head impacts from the perspective of behavior and EEG time-frequency oscillations. Joint analysis of EEG low-frequency oscillations and the innovative task with multiple challenging load conditions may serve as a promising way to detect concealed deficiencies within working memory processing. Keywords: repeated subconcussive head impacts, working memory, modified Sternberg task, event-related desynchronization, event-related synchronization, boxing athletes.

Incidence of Depression after Traumatic Brain Injury: A Nationwide Longitudinal Study of 2.2 Million Adults

Although improvements in acute care for traumatic brain injury (TBI) have increased the patient survival rate, many survivors often suffer from neuropsychiatric sequelae such as depression. This study investigated the influence of TBI on the risk of depression using South Korean nationwide data. Data were extracted from the National Health Insurance Service database for patients who experienced TBI from 2010 to 2017 (n = 1,141,593) and for 1:1 matched controls without TBI (n = 1,141,593). Patients under 18 years old or with a history of depression were excluded. TBI was used as a time-varying exposure and a time-dependent Cox regression model was adopted. Age, sex, insurance premium and type, region of residence, past psychiatric diseases, and Charlson Comorbidity Index were adjusted. The incidence of depression in the patients with TBI and matched controls was 34.60 and 21.42 per 1000 person-years, respectively. The risk of depression was higher in the patients with TBI (hazard ratio [HR] 1.19, 95% confidence interval [CI] = 1.18-1.20) than in the matched control group. After stratification by sex and age, the risk was higher in men and the younger age group. In subgroup analyses, patients with skull fracture showed the highest risk of depression. Notably, during the first year after TBI, the depression risk was almost 11 times higher than that in the matched control group (HR 11.71, 95% CI = 11.54-11.87). Our findings highlight a significant association of TBI with an increased risk of subsequent depression. Therefore, continuous awareness with regard to patients' mental health is needed.

Alzheimer's Disease-Related Dementias Summit 2019: National research priorities for the investigation of traumatic brain injury as a risk factor for Alzheimer's Disease and Related Dementias

TBI is a risk factor for later life dementia. Clinical and preclinical studies have elucidated multiple mechanisms through which TBI may influence or exacerbate multiple pathological processes underlying Alzheimer's Disease and Alzheimer's Disease Related Dementias (AD/ADRD). The National Institutes of Health hosts triennial ADRD Summits to inform a national research agenda, and the 2019 ADRD Summit was the first to highlight 'TBI and AD/ADRD Risk' as an emerging topic in the field. A multidisciplinary committee of TBI researchers with relevant expertise reviewed extant literature, identified research gaps and opportunities, and proposed draft research recommendations at the 2019 ADRD Summit. These research recommendations, further refined after broad stakeholder input at the Summit, cover four overall areas: (1) Encourage crosstalk and interdisciplinary collaboration between TBI and dementia researchers, (2) Establish infrastructure to study TBI as a risk factor for AD/ADRD, (3) Promote basic and clinical research examining the development and progression of TBI AD/ADRD neuropathologies and associated clinical symptoms, and (4) Characterize the clinical phenotype of progressive dementia associated with TBI and develop non-invasive diagnostic approaches. These recommendations recognize a need to strengthen communication and build frameworks to connect the complexity of TBI with rapidly evolving AD/ADRD research. Recommendations acknowledge TBI as a clinically and pathologically heterogeneous disease whose associations with AD/ADRDs remain incompletely understood. The recommendations highlight the scientific advantage of investigating AD/ADRD in the context of a known TBI exposure, the study of which can directly inform on disease mechanisms and treatment targets for AD/ADRDs with shared common pathways.

Repeated 31P-MRS in severe traumatic brain injury: Insights into cerebral energy status and altered metabolism

Phosphorous magnetic resonance spectroscopy (31P-MRS) is suited to non-invasively investigate energy metabolism and to detect molecules containing phosphorus in the human brain. The aim of this longitudinal study was to perform 31P-MRS at two different time points (within 72 hours and between day 10-14) after severe traumatic brain injury (sTBI) to reveal alterations in cerebral energy metabolism. Twenty-six ventilated sTBI patients, aged between 20 to 75 years, with a median initial GCS of 5 were prospectively analyzed. 31P-MRS data of the structurally more affected side were compared to data from contralateral normal appearing areas and to data of age- and gender-matched healthy controls. There were no significant intraindividual differences between the lesioned and the less affected side at either of time points. In the acute phase, PCr/ATP and PCr/Pi were significantly elevated whereas PME/PDE and Pi/ATP were significantly decreased in contrast to healthy controls. In the subacute phase these differences gradually dissipated, remaining lower Pi/ATP ratio, and only partly altered levels of PCr/Pi and PME/PDE. Our data affirm that cerebral metabolism is globally altered after sTBI, demonstrating the diffuse impairment of brain bioenergetics at multiple levels, with resultant developments in terms of time.