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More than 75% of patients presenting to level I trauma centers in the United States with suspicion of TBI sufficient to require a clinical computed tomography scan report injury-related symptoms 3 months later. There are currently no approved treatments, and few clinical trials have evaluated possible treatments. Efficient trials will require subject inclusion and exclusion criteria that balance cost-effective recruitment with enrolling individuals with a higher chance of benefiting from the interventions. Using data from the

The National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH-NINDS) Traumatic Brain Injury (TBI) Imaging Common Data Elements (CDEs) are standardized definitions for pathological intracranial lesions based on their appearance on neuroimaging studies. The NIH-NINDS TBI Imaging CDEs were designed to be as consistent as possible with the U.S. Food and Drug Administration (FDA) definition of biomarkers as "an indicator of normal biological processes, pathogenic processes, or biological responses to an exposure or intervention." However, the FDA qualification process for biomarkers requires proof of reliable biomarker test measurements. We determined the interrater reliability of TBI Imaging CDEs on subacute brain magnetic resonance imaging (MRI) performed on 517 mild TBI patients presenting to 11 U.S. level 1 trauma centers. Three U.S. board-certified neuroradiologists independently evaluated brain MRI performed 2 weeks post-injury for the following CDEs: traumatic axonal injury (TAI), diffuse axonal injury (DAI), and brain contusion. We found very high interrater agreement for brain contusion, with prevalence- and bias-adjusted kappa (PABAK) values for pairs of readers from 0.92 [95% confidence interval, 0.88-0.95] to 0.94 [0.90-0.96]. We found intermediate agreement for TAI and DAI, with PABAK values of 0.74-0.78 [0.70-0.82]. The near-perfect agreement for subacute brain contusion is likely attributable to the high conspicuity and distinctive appearance of these lesions on T1-weighted images. Interrater agreement for TAI and DAI was lower, because signal void in small vascular structures, and artifactual foci of signal void, can be difficult to distinguish from the punctate round or linear areas of slight hemorrhage that are a common hallmark of TAI/DAI on MRI.

The effects of traumatic brain injury (TBI) are difficult to measure in longitudinal cohort studies, because disparate pre-injury characteristics and injury mechanisms produce variable impairment profiles and recovery trajectories. In preparation for the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study, which followed patients with injuries ranging from uncomplicated mild TBI to coma, we designed a multi-dimensional Flexible outcome Assessment Battery (FAB). The FAB relies on a decision-making algorithm that assigns participants to a Comprehensive (CAB) or Abbreviated Assessment Battery (AAB) and guides test selection across all phases of recovery. To assess feasibility of the FAB, we calculated the proportion of participants followed at 2 weeks (2w) and at 3, 6, and 12 months (3m, 6m, 12m) post-injury who completed the FAB and received valid scores. We evaluated utility of the FAB by examining differences in 6m and 12m Glasgow Outcome Scale-Extended (GOSE) scores between participant subgroups derived from the FAB-enabled versus traditional approach to outcome assessment applied at 2w. Among participants followed at 2w (

Adult patients with mild traumatic brain injury (mTBI) exhibit distinct phenotypes of emotional and cognitive functioning identified by latent profile analysis of clinical neuropsychological assessments. When discerned early after injury, these latent clinical profiles have been found to improve prediction of long-term outcomes from mTBI. The present study hypothesized that white matter (WM) microstructure is better preserved in an emotionally resilient (ER) mTBI phenotype compared with a neuropsychiatrically distressed (ND) mTBI phenotype.The present study used diffusion MRI to investigate and compare WM microstructure in major association, projection, and commissural tracts between the two phenotypes and over time. Diffusion MR images from 172 mTBI patients were analyzed to compute individual diffusion tensor imaging (DTI) maps at 2 weeks and 6 months postinjury.By comparing the DTI parameters between the two phenotypes at global, regional, and voxel levels, the present study showed that the ER patients have higher axial diffusivity (AD) compared to their ND counterparts early after mTBI. Longitudinal analysis revealed greater compromise of WM microstructure in ND patients, with greater decrease of global AD and more widespread decrease of regional AD during the first 6 months after injury compared to their ER counterparts.These results provide neuroimaging evidence of WM microstructural differences underpinning mTBI phenotypes identified from neuropsychological assessments and show differing longitudinal trajectories of these biological effects. These findings suggest diffusion MRI can provide short- and long-term imaging biomarkers of resilience.

The Glasgow Outcome Scale (GOS) in its original or extended (GOSE) form is the most widely used assessment of global disability in traumatic brain injury (TBI) research. Several publications have reported concerns about assessor scoring inconsistencies, but without documentation of contributing factors. We reviewed 6801 GOSE assessments collected longitudinally, across 18 sites in the 5-year, observational Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. We recorded error rates (i.e., corrections to a section or an overall rating) based on site assessor documentation and categorized scoring issues, which then informed further training. In cohort 1 (n = 1261; February 2014 to May 2016), 24% of GOSEs had errors identified by central review. In cohort 2 (n = 1130; June 2016 to July 2018), acquired after curation of cohort 1 data, feedback, and further training of site assessors, the error rate was reduced to 10%. GOSE sections associated with the most frequent interpretation and scoring difficulties included whether current functioning represented a change from pre-injury (466 corrected ratings in cohort 1; 62 in cohort 2), defining dependency in the home and community (163 corrections in cohort 1; three in cohort 2) and return to work/school (72 corrections in cohort 1; 35 in cohort 2). These results highlight the importance of central review in improving consistency across sites and over time. Establishing clear scoring criteria, coupled with ongoing guidance and feedback to data collectors, is essential to avoid scoring errors and resultant misclassification, which carry potential to result in "failure" of clinical trials that rely on the GOSE as their primary outcome measure.

Polytrauma and traumatic brain injury (TBI) frequently co-occur and outcomes are routinely measured by the Glasgow Outcome Scale-Extended (GOSE). Polytrauma may confound GOSE measurement of TBI-specific outcomes. Adult patients with TBI from the prospective Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study had presented to a Level 1 trauma center after injury, received head computed tomography (CT) within 24 h, and completed the GOSE at 3 months and 6 months post-injury. Polytrauma was defined as an Abbreviated Injury Score (AIS) ≥3 in any extracranial region. Univariate regressions were performed using known GOSE clinical cutoffs. Multi-variable regressions were performed for the 3- and 6-month GOSE, controlling for known demographic and injury predictors. Of 361 subjects (age 44.9 ± 18.9 years, 69.8% male), 69 (19.1%) suffered polytrauma. By Glasgow Coma Scale (GCS) assessment, 80.1% had mild, 5.8% moderate, and 14.1% severe TBI. On univariate logistic regression, polytrauma was associated with increased odds of moderate disability or worse (GOSE ≤6; 3 month odds ratio [OR] = 2.57 [95% confidence interval (CI): 1.50-4.41; 6 month OR = 1.70 [95% CI: 1.01-2.88]) and death/severe disability (GOSE ≤4; 3 month OR = 3.80 [95% CI: 2.03-7.11]; 6 month OR = 3.33 [95% CI: 1.71-6.46]). Compared with patients with isolated TBI, more polytrauma patients experienced a decline in GOSE from 3 to 6 months (37.7 vs. 24.7%), and fewer improved (11.6 vs. 22.6%). Polytrauma was associated with greater univariate ordinal odds for poorer GOSE (3 month OR = 2.79 [95% CI: 1.73-4.49]; 6 month OR = 1.73 [95% CI: 1.07-2.79]), which was conserved on multi-variable ordinal regression (3 month OR = 3.05 [95% CI: 1.76-5.26]; 6 month OR = 2.04 [95% CI: 1.18-3.42]). Patients with TBI with polytrauma are at greater risk for 3- and 6-month disability compared with those with isolated TBI. Methodological improvements in assessing TBI-specific disability, versus disability attributable to all systemic injuries, will generate better TBI outcomes assessment tools.

Background: Frailty is known to be associated with poorer outcomes in individuals admitted to hospital for medical conditions requiring intensive care. However, little evidence is available for the effect of frailty on patients’ outcomes after traumatic brain injury. Many frailty indices have been validated for clinical practice and show good performance to predict clinical outcomes. However, each is specific to a particular clinical context. We aimed to develop a frailty index to predict 6-month outcomes in patients after a traumatic brain injury. Methods: A cumulative deficit approach was used to create a novel frailty index based on 30 items dealing with disease states, current medications, and laboratory values derived from data available from CENTER-TBI, a prospective, longitudinal observational study of patients with traumatic brain injury presenting within 24 h of injury and admitted to a ward or an intensive care unit at 65 centres in Europe between Dec 19, 2014, and Dec 17, 2017. From the individual cumulative CENTER-TBI frailty index (range 0–30), we obtained a standardised value (range 0–1), with high scores indicating higher levels of frailty. The effect of frailty on 6-month outcome evaluated with the extended Glasgow Outcome Scale (GOSE) was assessed through a proportional odds logistic model adjusted for known outcome predictors. An unfavourable outcome was defined as death or severe disability (GOSE score ≤4). External validation was performed on data from TRACK-TBI, a prospective observational study co-designed with CENTER-TBI, which enrolled patients with traumatic brain injury at 18 level I trauma centres in the USA from Feb 26, 2014, to July 27, 2018. CENTER-TBI is registered with ClinicalTrials.gov, NCT02210221; TRACK-TBI is registered at ClinicalTrials.gov, NCT02119182. Findings: 2993 participants (median age was 51 years [IQR 30–67], 2058 [69%] were men) were included in this analysis. The overall median CENTER-TBI frailty index score was 0·07 (IQR 0·03–0·15), with a median score of 0·17 (0·08–0·27) in older adults (aged ≥65 years). The CENTER-TBI frailty index score was significantly associated with the probability of an increasingly unfavourable outcome (cumulative odds ratio [OR] 1·03, 95% CI 1·02–1·04; p

Key Points Question Is posttraumatic epilepsy (PTE) associated with unfavorable functional outcomes after traumatic brain injury (TBI)? Findings In this cohort study that included 3296 individuals, the incidence of self-reported diagnosis of PTE at 1 year after injury among individuals who had experienced TBI was 2.8%. Patients with PTE had worse outcome scores at 1 year after injury compared with those without PTE, even after accounting for injury severity and neuroimaging findings on cranial computed tomography. Meaning These findings suggest that PTE is a significant sequela of TBI with adverse associations with recovery., This cohort study assesses the incidence, risk factors, and functional outcomes associated with self-reported posttraumatic epilepsy in patients with traumatic brain injury., Importance Posttraumatic epilepsy (PTE) is a recognized sequela of traumatic brain injury (TBI), but the long-term outcomes associated with PTE independent of injury severity are not precisely known. Objective To determine the incidence, risk factors, and association with functional outcomes and self-reported somatic, cognitive, and psychological concerns of self-reported PTE in a large, prospectively collected TBI cohort. Design, Setting, and Participants This multicenter, prospective cohort study was conducted as part of the Transforming Research and Clinical Knowledge in Traumatic Brain Injury study and identified patients presenting with TBI to 1 of 18 participating level 1 US trauma centers from February 2014 to July 2018. Patients with TBI, extracranial orthopedic injuries (orthopedic controls), and individuals without reported injuries (eg, friends and family of participants; hereafter friend controls) were prospectively followed for 12 months. Data were analyzed from January 2020 to April 2021. Exposure Demographic, imaging, and clinical information was collected according to TBI Common Data Elements. Incidence of self-reported PTE was assessed using the National Institute of Neurological Disorders and Stroke Epilepsy Screening Questionnaire (NINDS-ESQ). Main Outcomes and Measures Primary outcomes included Glasgow Outcome Scale Extended, Rivermead Cognitive Metric (RCM; derived from the Rivermead Post Concussion Symptoms Questionnaire), and the Brief Symptom Inventory-18 (BSI). Results Of 3296 participants identified as part of the study, 3044 met inclusion criteria, and 1885 participants (mean [SD] age, 41.3 [17.1] years; 1241 [65.8%] men and 644 [34.2%] women) had follow-up information at 12 months, including 1493 patients with TBI; 182 orthopedic controls, 210 uninjured friend controls; 41 patients with TBI (2.8%) and no controls had positive screening results for PTE. Compared with a negative screening result for PTE, having a positive screening result for PTE was associated with presenting Glasgow Coma Scale score (8.1 [4.8] vs.13.5 [3.3]; P

In nearly all clinical and research contexts, the initial severity of a traumatic brain injury (TBI) is measured using the Glasgow Coma Scale (GCS) total score. However, the GCS total score may not accurately reflect level of consciousness, a critical indicator of injury severity. We investigated the relationship between GCS total scores and level of consciousness in a consecutive sample of 2,455 adult subjects assessed with the GCS 69,487 times as part of the multi-center Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. We assigned each GCS subscale score combination a level of consciousness rating based upon published criteria for the following disorders of consciousness (DoC) diagnoses: coma, vegetative state/unresponsive wakefulness syndrome, minimally conscious state, and post-traumatic confusional state, and present our findings using summary statistics and four illustrative cases. Participants had the following characteristics: mean (standard deviation) age 41.9 (17.6) years, 69% male, initial GCS 3-8=13%; 9-12=5%; 13-15=82%. All GCS total scores between 4-14 were associated with more than one DoC diagnosis; the greatest variability was observed for scores of 7-11. Furthermore, a wide range of total scores were associated with identical DoC diagnoses. Importantly, a diagnosis of coma was only possible with GCS total scores of 3-6. The GCS total score does not accurately reflect level of consciousness based on published DoC diagnostic criteria. To improve the classification of patients with TBI and to inform the design of future clinical trials, clinicians and investigators should consider individual subscale behaviors and more comprehensive assessments when evaluating TBI severity.

Key Points Question Are different patterns of intracranial injury on head computed tomography associated with prognosis after mild traumatic brain injury (mTBI)? Findings In this cohort study, subarachnoid hemorrhage, subdural hematoma, and contusion often co-occurred and were associated with both incomplete recovery and more severe impairment out to 12 months after injury, while intraventricular and/or petechial hemorrhage co-occurred and were associated with more severe impairment up to 12 months after injury; epidural hematoma was associated with incomplete recovery at some points but not with more severe impairment. Some intracranial hemorrhage patterns were more strongly associated with outcomes than previously validated demographic and clinical variables. Meaning In this study, different pathological features on head computed tomography carried different implications for mild traumatic brain injury prognosis to 1 year., The longitudinal, observational study aims to identify pathological computed tomography features associated with adverse outcomes after mild traumatic brain injury., Importance A head computed tomography (CT) with positive results for acute intracranial hemorrhage is the gold-standard diagnostic biomarker for acute traumatic brain injury (TBI). In moderate to severe TBI (Glasgow Coma Scale [GCS] scores 3-12), some CT features have been shown to be associated with outcomes. In mild TBI (mTBI; GCS scores 13-15), distribution and co-occurrence of pathological CT features and their prognostic importance are not well understood. Objective To identify pathological CT features associated with adverse outcomes after mTBI. Design, Setting, and Participants The longitudinal, observational Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study enrolled patients with TBI, including those 17 years and older with GCS scores of 13 to 15 who presented to emergency departments at 18 US level 1 trauma centers between February 26, 2014, and August 8, 2018, and underwent head CT imaging within 24 hours of TBI. Evaluations of CT imaging used TBI Common Data Elements. Glasgow Outcome Scale–Extended (GOSE) scores were assessed at 2 weeks and 3, 6, and 12 months postinjury. External validation of results was performed via the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. Data analyses were completed from February 2020 to February 2021. Exposures Acute nonpenetrating head trauma. Main Outcomes and Measures Frequency, co-occurrence, and clustering of CT features; incomplete recovery (GOSE scores

Importance Moderate to severe traumatic brain injury (msTBI) is a major cause of death and disability in the US and worldwide. Few studies have enabled prospective, longitudinal outcome data collection from the acute to chronic phases of recovery after msTBI. Objective To prospectively assess outcomes in major areas of life function at 2 weeks and 3, 6, and 12 months after msTBI. Design, Setting, and Participants This cohort study, as part of the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study, was conducted at 18 level 1 trauma centers in the US from February 2014 to August 2018 and prospectively assessed longitudinal outcomes, with follow-up to 12 months postinjury. Participants were patients with msTBI (Glasgow Coma Scale scores 3-12) extracted from a larger group of patients with mild, moderate, or severe TBI who were enrolled in TRACK-TBI. Data analysis took place from October 2019 to April 2021. Exposures Moderate or severe TBI. Main Outcomes and Measures The Glasgow Outcome Scale–Extended (GOSE) and Disability Rating Scale (DRS) were used to assess global functional status 2 weeks and 3, 6, and 12 months postinjury. Scores on the GOSE were dichotomized to determine favorable (scores 4-8) vs unfavorable (scores 1-3) outcomes. Neurocognitive testing and patient reported outcomes at 12 months postinjury were analyzed. Results A total of 484 eligible patients were included from the 2679 individuals in the TRACK-TBI study. Participants with severe TBI (n = 362; 283 men [78.2%]; median [interquartile range] age, 35.5 [25-53] years) and moderate TBI (n = 122; 98 men [80.3%]; median [interquartile range] age, 38 [25-53] years) were comparable on demographic and premorbid variables. At 2 weeks postinjury, 36 of 290 participants with severe TBI (12.4%) and 38 of 93 participants with moderate TBI (41%) had favorable outcomes (GOSE scores 4-8); 301 of 322 in the severe TBI group (93.5%) and 81 of 103 in the moderate TBI group (78.6%) had moderate disability or worse on the DRS (total score ≥4). By 12 months postinjury, 142 of 271 with severe TBI (52.4%) and 54 of 72 with moderate TBI (75%) achieved favorable outcomes. Nearly 1 in 5 participants with severe TBI (52 of 270 [19.3%]) and 1 in 3 with moderate TBI (23 of 71 [32%]) reported no disability (DRS score 0) at 12 months. Among participants in a vegetative state at 2 weeks, 62 of 79 (78%) regained consciousness and 14 of 56 with available data (25%) regained orientation by 12 months. Conclusions and Relevance In this study, patients with msTBI frequently demonstrated major functional gains, including recovery of independence, between 2 weeks and 12 months postinjury. Severe impairment in the short term did not portend poor outcomes in a substantial minority of patients with msTBI. When discussing prognosis during the first 2 weeks after injury, clinicians should be particularly cautious about making early, definitive prognostic statements suggesting poor outcomes and withdrawal of life-sustaining treatment in patients with msTBI.

Introduction: Risk factors for young adults with mTBI are not well understood. Improved understanding of age and sex as risk factors for impaired six-month outcomes in young adults is needed.Methods: Young adult mTBI subjects aged 18-39 years (18-29y; 30-39y) with six-month outcomes were extracted from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study. Multivariable regressions were performed for outcomes with age, sex, and the interaction factor age-group*sex as variables of interest, controlling for demographic and injury variables. Mean-differences (B) and 95% CIs are reported.Results: One hundred mTBI subjects (18-29y, 70%; 30-39y, 30%; male, 71%; female, 29%) met inclusion criteria. On multivariable analysis, age-group*sex was associated with six-month post-traumatic stress disorder (PTSD; PTSD Checklist-Civilian version); compared with female 30-39y, female 18-29y (B= -19.55 [-26.54, -4.45]), male 18-29y (B= -19.70 [-30.07, -9.33]), and male 30-39y (B= -15.49 [-26.54, -4.45]) were associated with decreased PTSD symptomatology. Female sex was associated with decreased six-month functional outcome (Glasgow Outcome Scale-Extended (GOSE): B= -0.6 [1.0, -0.1]). Comparatively, 30-39y scored higher on six-month nonverbal processing speed (Wechsler Adult Intelligence Scale-Processing Speed Index (WAIS-PSI); B= 11.88, 95% CI [1.66, 22.09]).Conclusions: Following mTBI, young adults aged 18-29y and 30-39y may have different risks for impairment. Sex may interact with age for PTSD symptomatology, with females 30-39y at highest risk. These results may be attributable to cortical maturation, biological response, social modifiers, and/or differential self-report. Confirmation in larger samples is needed; however, prevention and rehabilitation/counseling strategies after mTBI should likely be tailored for age and sex.

Introduction Return to work (RTW) is an important milestone of mild traumatic brain injury (mTBI) recovery. The objective of this study was to evaluate whether baseline clinical variables, three-month RTW, and three-month postconcussional symptoms (PCS) were associated with six-month RTW after mTBI. Methods Adult subjects from the prospective multicenter Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot study with mTBI (Glasgow Coma Scale 13–15) who were employed at baseline, with completed three- and six-month RTW status, and three-month Acute Concussion Evaluation (ACE), were extracted. Univariate and multivariable analyses were performed for six-month RTW, with focus on baseline employment, three-month RTW, and three-month ACE domains (physical, cognitive, sleep, and/or emotional postconcussional symptoms (PCS)). Odds ratios (OR) and 95% confidence intervals [CI] were reported. Significance was assessed at p Results In 152 patients aged 40.7 ± 15.0 years, 72% were employed full-time at baseline. Three- and six-month RTW were 77.6% and 78.9%, respectively. At three months, 59.2%, 47.4%, 46.1% and 31.6% scored positive for ACE physical, cognitive, sleep, and emotional PCS domains, respectively. Three-month RTW predicted six-month RTW (OR = 19.80, 95% CI [7.61–51.52]). On univariate analysis, scoring positive in any three-month ACE domain predicted inability for six-month RTW (OR = 0.10–0.11). On multivariable analysis, emotional symptoms predicted inability to six-month RTW (OR = 0.19 [0.04–0.85]). Subjects who scored positive in all four ACE domains were more likely to be unable to RTW at six months (4 domains: 58.3%, vs. 0-to-3 domains: 9.5%; multivariable OR = 0.09 [0.02–0.33]). Conclusions Three-month post-injury is an important time point at which RTW status and PCS should be assessed, as both are prognostic markers for six-month RTW. Clinicians should be particularly vigilant of patients who present with emotional symptoms, and patients with symptoms across multiple PCS categories, as these patients are at further risk of inability to RTW and may benefit from targeted evaluation and support.

Systemic inflammation impacts outcome after traumatic brain injury (TBI), but most TBI biomarker studies have focused on brain-specific proteins. C-reactive protein (CRP) is a widely used biomarker of inflammation with potential as a prognostic biomarker after TBI. The Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study prospectively enrolled TBI patients within 24 h of injury, as well as orthopedic injury and uninjured controls; biospecimens were collected at enrollment. A subset of hospitalized participants had blood collected on day 3, day 5, and 2 weeks. High-sensitivity CRP (hsCRP) and glial fibrillary acidic protein (GFAP) were measured. Receiver operating characteristic analysis was used to evaluate the prognostic ability of hsCRP for 6-month outcome, using the Glasgow Outcome Scale-Extended (GOSE). We included 1206 TBI subjects, 122 orthopedic trauma controls (OTCs), and 209 healthy controls (HCs). Longitudinal biomarker sampling was performed in 254 hospitalized TBI subjects and 19 OTCs. hsCRP rose between days 1 and 5 for TBI and OTC subjects, and fell by 2 weeks, but remained elevated compared with HCs (p

Glial fibrillary acidic protein (GFAP) is cleared by the Food and Drug Administration (FDA) to determine need for head computed tomography (CT) within 12 h after mild traumatic brain injury (TBI) (Glasgow Coma Score [GCS] 13-15); S100 calcium-binding protein B (S100B) serves this function in Europe. This phase 1 biomarker cohort analysis of the multi-center, observational Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study compares GFAP's diagnostic performance, measured on a rapid point-of-care platform, against protein S100B to predict intracranial abnormalities on CT within 24 h post-injury across the spectrum of TBI (GCS 3-15). Head CT scan performed in TBI subjects and blood was collected for all consenting subjects presenting to 18 United States level 1 trauma centers. Plasma was analyzed on a point-of-care device prototype assay for GFAP and serum was analyzed for S100B. In 1359 patients with TBI (GCS 3-15), mean (standard deviation [SD]) age = 40.1 (17.0) years; 68% were male. Plasma GFAP levels were significantly higher in CT+ TBI subjects (median = 1358 pg/mL, interquartile range [IQR]: 472-3803) than in CT- TBI subjects (median = 116 pg/mL, IQR: 26-397) or orthopedic trauma controls (n = 122; median = 13 pg/mL, IQR: 7-20), p

Background Brain volumes in regions such as the hippocampus and amygdala have been associated with risk for the development of posttraumatic stress disorder (PTSD). The objective of this study was to determine whether a set of regional brain volumes, measured by magnetic resonance imaging at 2 weeks following mild traumatic brain injury, were predictive of PTSD at 3 and 6 months after injury. Methods Using data from TRACK-TBI (Transforming Research and Clinical Knowledge in TBI), we included patients (N = 421) with Glasgow Coma Scale scores 13–15 assessed after evaluation in the emergency department and at 2 weeks, 3 months, and 6 months after injury. Probable PTSD diagnosis (PTSD Checklist for DSM-5 score, ≥33) was the outcome. FreeSurfer 6.0 was used to perform volumetric analysis of three-dimensional T1-weighted magnetic resonance images at 3T obtained 2 weeks post injury. Brain regions selected a priori for volumetric analyses were insula, hippocampus, amygdala, superior frontal cortex, rostral and caudal anterior cingulate, and lateral and medial orbitofrontal cortices. Results Overall, 77 (18.3%) and 70 (16.6%) patients had probable PTSD at 3 and 6 months. A composite volume derived as the first principal component incorporating 73.8% of the variance in insula, superior frontal cortex, and rostral and caudal cingulate contributed to the prediction of 3-month (but not 6-month) PTSD in multivariable models incorporating other established risk factors. Conclusions Results, while needing replication, provide support for a brain reserve hypothesis of PTSD and proof of principle for how prediction of at-risk individuals might be accomplished to enhance prognostic accuracy and enrich clinical prevention trials for individuals at the highest risk of PTSD following mild traumatic brain injury.

INTRODUCTION: Mild traumatic brain injury (MTBI) can cause persistent functional deficits and healthcare burden. Intracerebral contusions cause permanent parenchymal injury, and understanding their association with outcomes may aid in treatment and prognosis. METHODS: Adult MTBI patients with arrival GCS 13–15 and six-month outcomes [Glasgow Outcome Scale Extended (GOSE)], without polytrauma or operative neurosurgery from the prospective TRACK-TBI Pilot study were analyzed. Intracranial contusions detected by computed tomography (CT) were coded by location. Multivariable regression evaluated associations between intracranial injury type (temporal contusion (TC), frontal contusion, extraaxial [epidural/subdural/subarachnoid], other-intraaxial [intracerebral/intraventricular hemorrhage, axonal injury]) and GOSE. Odds ratios (OR) are reported. RESULTS: Overall, 260 MTBI subjects were aged 44.4±18.1-years and 67.7%-male. Ninety-seven subjects were CT-positive, of which 46 had contusions (41.3%-frontal, 30.4%-temporal, 21.7%-frontal+temporal, 2.2%-parietal, 2.2%-occipital, 2.2%-brainstem); 95.7% had concurrent extraaxial hemorrhage. Mortality was 0% at discharge and 2.3% by six months. Six-month GOSE was distributed with 2.3%-death, 1.5%-severe disability, 27.7%-moderate disability, 68.5%-good recovery. Nearly 46% of TC-positive subjects suffered moderate disability or worse (GOSE≤6) and 41.7% were unable to return to baseline work capacity (RTBWC), compared to 29.1%/20.4% for CT-negative and 26.1%/20.9% for CT-positive subjects without TC. On multivariable regression, TC associated with OR=3.33 (95% CI [1.16–9.60], p=0.026) for GOSE≤6, and OR=4.48 ([1.49–13.51], p=0.008) for inability to RTBWC. CONCLUSIONS: Parenchymal contusions in MTBI are often accompanied by extraaxial hemorrhage. TCs may be associated with six-month functional impairment. Their presence on imaging should alert the clinician to the need for heightened surveillance of sequelae complicating RTBWC, with low threshold for referral to services.

Most traumatic brain injuries (TBIs) are classified as mild (mTBI) based on admission Glasgow Coma Scale (GCS) scores of 13 to 15. The prevalence of persistent functional limitations for these patients is unclear.To characterize the natural history of recovery of daily function following mTBI vs peripheral orthopedic traumatic injury in the first 12 months postinjury using data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study, and, using clinical computed tomographic (CT) scans, examine whether the presence (CT+) or absence (CT-) of acute intracranial findings in the mTBI group was associated with outcomes.TRACK-TBI, a cohort study of patients with mTBI presenting to US level I trauma centers, enrolled patients from February 26, 2014, to August 8, 2018, and followed up for 12 months. A total of 1453 patients at 11 level I trauma center emergency departments or inpatient units met inclusion criteria (ie, mTBI [n = 1154] or peripheral orthopedic traumatic injury [n = 299]) and were enrolled within 24 hours of injury; mTBI participants had admission GCS scores of 13 to 15 and clinical head CT scans. Patients with peripheral orthopedic trauma injury served as the control (OTC) group.Participants with mTBI or OTC.The Glasgow Outcome Scale Extended (GOSE) scale score, reflecting injury-related functional limitations across broad life domains at 2 weeks and 3, 6, and 12 months postinjury was the primary outcome. The possible score range of the GOSE score is 1 (dead) to 8 (upper good recovery), with a score less than 8 indicating some degree of functional impairment.Of the 1453 participants, 953 (65.6%) were men; mean (SD) age was 40.9 (17.1) years in the mTBI group and 40.9 (15.4) years in the OTC group. Most participants (mTBI, 87%; OTC, 93%) reported functional limitations (GOSE8) at 2 weeks postinjury. At 12 months, the percentage of mTBI participants reporting functional limitations was 53% (95% CI, 49%-56%) vs 38% (95% CI, 30%-45%) for OTCs. A higher percentage of CT+ patients reported impairment (61%) compared with the mTBI CT- group (49%; relative risk [RR], 1.24; 95% CI, 1.08-1.43) and a higher percentage in the mTBI CT-group compared with the OTC group (RR, 1.28; 95% CI, 1.02-1.60).Most patients with mTBI presenting to US level I trauma centers report persistent, injury-related life difficulties at 1 year postinjury, suggesting the need for more systematic follow-up of patients with mTBI to provide treatments and reduce the risk of chronic problems after mTBI.

Key Points Question Do postacute mild traumatic brain injury (mTBI) symptoms differ between men and women? Findings In this cohort study of 2000 patients with mTBI, the severity of cognitive and somatic symptoms on the Rivermead Post Concussion Symptoms Questionnaire at 12 months after injury was significantly worse in women than in men, whereas this difference was not significant in an orthopedic trauma control group. The association between mTBI and somatic symptoms was greater in women aged 35 to 49 years than those aged 17 to 34 years or older than 50 years. Meaning Sex and age may be important factors in the individualized, postacute treatment of patients with mTBI., This cohort study uses data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study to assess whether patient sex and age are associated with mild traumatic brain injury symptoms., Importance Knowledge of differences in mild traumatic brain injury (mTBI) recovery by sex and age may inform individualized treatment of these patients. Objective To identify sex-related differences in symptom recovery from mTBI; secondarily, to explore age differences within women, who demonstrate poorer outcomes after TBI. Design, Setting, and Participants The prospective cohort study Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) recruited 2000 patients with mTBI from February 26, 2014, to July 3, 2018, and 299 patients with orthopedic trauma (who served as controls) from January 26, 2016, to July 27, 2018. Patients were recruited from 18 level I trauma centers and followed up for 12 months. Data were analyzed from August 19, 2020, to March 3, 2021. Exposures Patients with mTBI (defined by a Glasgow Coma Scale score of 13-15) triaged to head computed tomography in 24 hours or less; patients with orthopedic trauma served as controls. Main Outcomes and Measures Measured outcomes included (1) the Rivermead Post Concussion Symptoms Questionnaire (RPQ), a 16-item self-report scale that assesses postconcussion symptom severity over the past 7 days relative to preinjury; (2) the Posttraumatic Stress Disorder Checklist for the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (PCL-5), a 20-item test that measures the severity of posttraumatic stress disorder symptoms; (3) the Patient Health Questionnaire-9 (PHQ-9), a 9-item scale that measures depression based on symptom frequency over the past 2 weeks; and (4) the Brief Symptom Inventory-18 (BSI-18), an 18-item scale of psychological distress (split into Depression and Anxiety subscales). Results A total of 2000 patients with mTBI (1331 men [67%; mean (SD) age, 41.0 (17.3) years; 1026 White (78%)] and 669 women [33%; mean (SD) age, 43.0 (18.5) years; 505 (76%) White]). After adjustment of multiple comparisons, significant TBI × sex interactions were observed for cognitive symptoms (B = 0.76; 5% false discovery rate–corrected P = .02) and somatic RPQ symptoms (B = 0.80; 5% false discovery rate–corrected P = .02), with worse symptoms in women with mTBI than men, but no sex difference in symptoms in control patients with orthopedic trauma. Within the female patients evaluated, there was a significant TBI × age interaction for somatic RPQ symptoms, which were worse in female patients with mTBI aged 35 to 49 years compared with those aged 17 to 34 years (B = 1.65; P = .02) or older than 50 years (B = 1.66; P = .02). Conclusions and Relevance This study found that women were more vulnerable than men to persistent mTBI-related cognitive and somatic symptoms, whereas no sex difference in symptom burden was seen after orthopedic injury. Postconcussion symptoms were also worse in women aged 35 to 49 years than in younger and older women, but further investigation is needed to corroborate these findings and to identify the mechanisms involved. Results suggest that individualized clinical management of mTBI should consider sex and age, as some women are especially predisposed to chronic postconcussion symptoms even 12 months after injury.

Importance Heterogeneity across patients with traumatic brain injury (TBI) presents challenges for clinical care and intervention design. Identifying distinct clinical phenotypes of TBI soon after injury may inform patient selection for precision medicine clinical trials. Objective To investigate whether distinct neurobehavioral phenotypes can be identified 2 weeks after TBI and to characterize the degree to which early neurobehavioral phenotypes are associated with 6-month outcomes. Design, setting, and participants This prospective cohort study included patients presenting to 18 US level 1 trauma centers within 24 hours of TBI from 2014 to 2019 as part of the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. Data were analyzed from January 28, 2020, to January 11, 2021. Exposures TBI. Main outcomes and measures Latent profiles (LPs) were derived from common dimensions of neurobehavioral functioning at 2 weeks after injury, assessed through National Institutes of Health TBI Common Data Elements (ie, Brief Symptom Inventory-18, Patient Health Questionnaire-9 Depression checklist, Posttraumatic Stress Disorder Checklist for DSM-5, PROMIS Pain Intensity scale, Insomnia Severity Index, Rey Auditory Verbal Learning Test, Wechsler Adult Intelligence Scale-Fourth Edition Coding and Symbol Search subtests, Trail Making Test, and NIH Toolbox Cognitive Battery Pattern Comparison Processing Speed, Dimensional Change Card Sort, Flanker Inhibitory Control and Attention, and Picture Sequence Memory subtests). Six-month outcomes were the Satisfaction With Life Scale (SWLS), Quality of Life after Brain Injury-Overall Scale (QOLIBRI-OS), Glasgow Outcome Scale-Extended (GOSE), and Rivermead Post-Concussion Symptoms Questionnaire (RPQ). Results Among 1757 patients with TBI included, 1184 (67.4%) were men, and the mean (SD) age was 39.9 (17.0) years. LP analysis revealed 4 distinct neurobehavioral phenotypes at 2 weeks after injury: emotionally resilient (419 individuals [23.8%]), cognitively impaired (368 individuals [20.9%]), cognitively resilient (620 individuals [35.3%]), and neuropsychiatrically distressed (with cognitive weaknesses; 350 individuals [19.9%]). Adding LP group to models including demographic characteristics, medical history, Glasgow Coma Scale score, and other injury characteristics was associated with significantly improved estimation of association with 6-month outcome (GOSE R2 increase = 0.09-0.19; SWLS R2 increase = 0.12-0.22; QOLIBRI-OS R2 increase = 0.14-0.32; RPQ R2 = 0.13-0.34). Conclusions and relevance In this cohort study of patients with TBI presenting to US level-1 trauma centers, qualitatively distinct profiles of symptoms and cognitive functioning were identified at 2 weeks after TBI. These distinct phenotypes may help optimize clinical decision-making regarding prognosis, as well as selection and stratification for randomized clinical trials.

Summary Background After traumatic brain injury (TBI), plasma concentration of glial fibrillary acidic protein (GFAP) correlates with intracranial injury visible on CT scan. Some patients with suspected TBI with normal CT findings show pathology on MRI. We assessed the discriminative ability of GFAP to identify MRI abnormalities in patients with normal CT findings. Methods TRACK-TBI is a prospective cohort study that enrolled patients with TBI who had a clinically indicated head CT scan within 24 h of injury at 18 level 1 trauma centres in the USA. For this analysis, we included patients with normal CT findings (Glasgow Coma Scale score 13–15) who consented to venepuncture within 24 h post injury and who had an MRI scan 7–18 days post injury. We compared MRI findings in these patients with those of orthopaedic trauma controls and healthy controls recruited from the study sites. Plasma GFAP concentrations (pg/mL) were measured using a prototype assay on a point-of-care platform. We used receiver operating characteristic (ROC) analysis to evaluate the discriminative ability of GFAP for positive MRI scans in patients with negative CT scans over 24 h (time between injury and venepuncture). The primary outcome was the area under the ROC curve (AUC) for GFAP in patients with CT-negative and MRI-positive findings versus patients with CT-negative and MRI-negative findings within 24 h of injury. The Dunn Kruskal–Wallis test was used to compare GFAP concentrations between MRI lesion types with Benjamini–Hochberg correction for multiple comparisons. This study is registered with ClinicalTrials.gov , number NCT02119182 . Findings Between Feb 26, 2014, and June 15, 2018, we recruited 450 patients with normal head CT scans (of whom 330 had negative MRI scans and 120 had positive MRI scans), 122 orthopaedic trauma controls, and 209 healthy controls. AUC for GFAP in patients with CT-negative and MRI-positive findings versus patients with CT-negative and MRI-negative findings was 0·777 (95% CI 0·726–0·829) over 24 h. Median plasma GFAP concentration was highest in patients with CT-negative and MRI-positive findings (414·4 pg/mL, 25–75th percentile 139·3–813·4), followed by patients with CT-negative and MRI-negative findings (74·0 pg/mL, 17·5–214·4), orthopaedic trauma controls (13·1 pg/mL, 6·9–20·0), and healthy controls (8·0 pg/mL, 3·0–14·0; all comparisons between patients with CT-negative MRI-positive findings and other groups p Interpretation Analysis of blood GFAP concentrations using prototype assays on a point-of-care platform within 24 h of injury might improve detection of TBI and identify patients who might need subsequent MRI and follow-up. Funding National Institute of Neurological Disorders and Stroke and US Department of Defense.

BACKGROUND Preinjury employment status may contribute to disparity, injury risk, and recovery patterns following mild traumatic brain injury (MTBI). OBJECTIVE To characterize associations between preinjury unemployment, prior comorbidities, and outcomes following MTBI. METHODS MTBI patients from TRACK-TBI Pilot with complete six-month outcomes were extracted. Preinjury unemployment, comorbidities, injury factors, and intracranial pathology were considered. Multivariable regression was performed for employment and outcomes, correcting for demographic and injury factors. Mean-differences (B) and 95% CIs are reported. Statistical significance was assessed at p < 0.05. RESULTS 162 MTBI patients were aged 39.8±15.4-years and 24.6% -unemployed. Unemployed patients demonstrated increased psychiatric comorbidities (45.0% -vs.- 23.8%; p = 0.010), drug use (52.5% -vs.- 21.3%; p < 0.001), smoking (62.5% -vs.- 27.0%; p < 0.001), prior TBI (78.4% -vs.- 55.0%; p = 0.012), and lower education (15.0% -vs.- 45.1% college degree; p = 0.003). On multivariable analysis, unemployment associated with decreased six-month functional outcome (Glasgow Outcome Scale-Extended: B = - 0.50, 95% CI [- 0.88, - 0.11]), increased psychiatric disturbance (Brief Symptom Inventory-18: B = 6.22 [2.33, 10.10]), postconcussional symptoms (Rivermead Questionnaire: B = 4.91 [0.38, 9.44]), and post-traumatic stress disorder (PTSD Checklist-Civilian: B = 5.99 [0.76, 11.22]). No differences were observed for cognitive measures or satisfaction with life. CONCLUSIONS Unemployed patients are at risk for preinjury psychosocial comorbidities, poorer six-month functional recovery and increased psychiatric/postconcussional/PTSD symptoms. Resource allocation and return precautions should be implemented to mitigate and/or prevent the decline of at-risk patients.

Traumatic brain injury (TBI) is a global public health problem that affects the long-term cognitive, physical, and psychological health of patients, while also having a major impact on family and caregivers. In stark contrast to the effective trials that have been conducted in other neurological diseases, nearly 30 studies of interventions employed during acute hospital care for TBI have failed to identify treatments that improve outcome. Many factors may confound the ability to detect true and meaningful treatment effects. One promising area for improving the precision of intervention studies is to optimize the validity of the outcome assessment battery by using well-designed tools and data collection strategies to reduce variability in the outcome data. The Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study, conducted at 18 sites across the United States, implemented a multi-dimensional outcome assessment battery with 22 measures aimed at characterizing TBI outcome up to one year post-injury. In parallel, through the TBI Endpoints Development (TED) Initiative, federal agencies and investigators have partnered to identify the most valid, reliable, and sensitive outcome assessments for TBI. Here we present lessons learned from the TRACK-TBI and TED initiatives aimed at optimizing the validity of outcome assessment in TBI.

The Traumatic Brain Injury Endpoints Development (TED) Initiative is a 5-year, Department of Defense-funded project that is working toward the ultimate goal of developing better designed clinical trials, leading to more precise diagnosis, and effective treatments for traumatic brain injury (TBI). TED is comprised of leading academic clinician-scientists, along with innovative industry leaders in biotechnology and imaging technology, patient advocacy organizations, and philanthropists, working collaboratively with regulatory authorities, specifically the U.S. Food and Drug Administration (FDA). The goals of the TED Initiative are to gain consensus and validation of TBI clinical outcome assessment measures and biomarkers for endorsement by global regulatory agencies for use in drug and device development processes. This article summarizes the Initiative's Stage I progress over the first 18 months, including intensive engagement with a number of FDA divisions responsible for review and validation of biomarkers and clinical outcome assessments, progression into the prequalification phase of the FDA's Medical Device Development Tool program for a candidate set of neuroimaging biomarkers, and receipt of the FDA's Recognition of Research Importance Letter and a Letter of Support regarding TBI. Other signal achievements relate to the creation of the TED Metadataset, harmonizing study measures across eight major TBI studies, and the leadership role played by TED investigators in the conversion of the NINDS TBI Common Data Elements to Clinical Data Interchange Standards Consortium standards. This article frames both the near-term expectations and the Initiative's long-term vision to accelerate approval of treatments for patients affected by TBI in urgent need of effective therapies.

Object Traumatic brain injury (TBI) is the leading cause of acquired disability in children, yet innate repair mechanisms are incompletely understood. Given data from animal studies documenting neurogenesis in response to trauma and other insults, the authors investigated whether similar responses could be found in children of different ages after TBI. Methods Immunohistochemistry was used to label doublecortin (DCX), a protein expressed by immature migrating neuroblasts (newborn neurons), in specimens from patients ranging in age from 3 weeks to 10 years who had died either after TBI or from other causes. Doublecortin-positive (DCX+) cells were examined in the subventricular zone (SVZ) and periventricular white matter (PWM) and were quantified within the granule cell layer (GCL) and subgranular zone (SGZ) of the dentate gyrus to determine if age and/or injury affect the number of DCX+ cells in these regions. Results The DCX+ cells decreased in the SVZ as patient age increased and were found in abundance around a focal subacute infarct in a 1-month-old non-TBI patient, but were scarce in all other patients regardless of age or history of trauma. The DCX+ cells in the PWM and dentate gyrus demonstrated a migratory morphology and did not co-localize with markers for astrocytes, microglia, or macrophages. In addition, there were significantly more DCX+ cells in the GCL and SGZ of the dentate gyrus in children younger than 1 year old than in older children. The density of immature migrating neuroblasts in infants (under 1 year of age) was significantly greater than in young children (2–6 years of age, p = 0.006) and older children (7–10 years of age, p = 0.007). Conclusions The main variable influencing the number of migrating neuroblasts observed in the SVZ, PWM, and hippocampus was patient age. Trauma had no discernible effect on the number of migrating neuroblasts in this cohort of patients in whom death typically occurred within hours to days after TBI.

Key Points Question Do patients with mild traumatic brain injury (mTBI) receive adequate levels of follow-up care? Findings In a cohort study using data on 831 patients with mTBI presenting to the emergency department at 1 of 11 level I trauma centers across the United States, 42% of patients reported receiving educational material at discharge and 44% reported seeing a physician or other medical practitioner within 3 months after injury. Among patients with 3 or more moderate to severe postconcussive symptoms, only 52% reported having seen a practitioner within 3 months following the injury. Meaning A large proportion of patients with mTBI do not receive follow-up care after injury even when they experience ongoing postconcussive symptoms., This cohort study describes follow-up care for patients within 3 months of receiving treatment for mild traumatic brain injury (TBI) or concussion at US emergency departments of level I trauma centers., Importance Mild traumatic brain injury (mTBI) affects millions of Americans each year. Lack of consistent clinical practice raises concern that many patients with mTBI may not receive adequate follow-up care. Objective To characterize the provision of follow-up care to patients with mTBI during the first 3 months after injury. Design, Setting, and Participants This cohort study used data on patients with mTBI enrolled in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study between February 26, 2014, and August 25, 2016. We examined site-specific variations in follow-up care, the types of clinicians seen by patients receiving follow-up care, and patient and injury characteristics associated with a higher likelihood of receiving follow-up care. The TRACK-TBI study is a prospective, multicenter, longitudinal observational study of patients with TBI presenting to the emergency department of 1 of 11 level I US trauma centers. Study data included patients with head trauma who underwent a computed tomography (CT) scan within 24 hours of injury, had a Glasgow Coma Scale score of 13 to 15, were aged 17 years or older, and completed follow-up care surveys at 2 weeks and 3 months after injury (N = 831). Main Outcomes and Measures Follow-up care was defined as hospitals providing TBI educational material at discharge, hospitals calling patients to follow up, and patients seeing a physician or other medical practitioner within 3 months after the injury. Unfavorable outcomes were assessed with the Rivermead Post Concussion Symptoms Questionnaire. Results Of 831 patients (289 [35%] female; 483 [58%] non-Hispanic white; mean [SD] age, 40.3 [16.9] years), less than half self-reported receiving TBI educational material at discharge (353 patients [42%]) or seeing a physician or other health care practitioner within 3 months after injury (367 patients [44%]). Follow-up care varied by study site; adjusting for patient characteristics, the provision of educational material varied from 19% to 72% across sites. Of 236 patients with a positive finding on a CT scan, 92 (39%) had not seen a medical practitioner 3 months after the injury. Adjusting for injury severity and demographics, patient admission to the hospital ward or intensive care unit, patient income, and insurance status were not associated with the probability of seeing a medical practitioner. Among the patients with 3 or more moderate to severe postconcussive symptoms, only 145 of 279 (52%) reported having seen a medical practitioner by 3 months. Conclusions and Relevance There are gaps in follow-up care for patients with mTBI after hospital discharge, even those with a positive finding on CT or who continue to experience postconcussive symptoms.

Stimulation of postnatal neurogenesis in the subventricular zone (SVZ) and robust migration of neuroblasts to the lesion site in response to traumatic brain injury (TBI) is well established in rodent species; however, it is not yet known whether postnatal neurogenesis plays a role in repair after TBI in gyrencephalic species. Here we describe the anatomy of the SVZ in the piglet for the first time and initiate an investigation into the effect of TBI on the SVZ architecture and the number of neuroblasts in the white matter. Among all ages of immaturity examined the SVZ contained a dense mesh network of neurogenic precursor cells (doublecortin+) positioned directly adjacent to the ependymal cells (ventricular SVZ, Vsvz) and neuroblasts organized into chains that were distinct from the Vsvz (abventricular SVZ, Asvz). Though the architecture of the SVZ was similar among ages, the areas of Vsvz and Asvz neuroblast chains declined with age. At postnatal day (PND) 14 the white matter tracts have a tremendous number of individual neuroblasts. In our scaled cortical impact model, lesion size increased with age. Similarly, the response of the SVZ to injury was also age dependent. The younger age groups that sustained the proportionately smallest lesions had the largest SVZ areas, which further increased in response to injury. In piglets that were injured at 4 months of age and had the largest lesions, the SVZ did not increase in response to injury. Similar to humans, swine have abundant gyri and gyral white matter, providing a unique platform to study neuroblasts potentially migrating from the SVZ to the lesioned cortex along these white matter tracts. In piglets injured at PND 7, TBI did not increase the total number of neuroblasts in the white matter compared to uninjured piglets, but redistribution occurred with a greater number of neuroblasts in the white matter of the hemisphere ipsilateral to the injury compared to the contralateral hemisphere. At 7 days after injury, less than 1% of neuroblasts in the white matter were born in the 2 days following injury. These data show that the SVZ in the piglet shares many anatomical similarities with the SVZ in the human infant, and that TBI had only modest effects on the SVZ and the number of neuroblasts in the white matter. Piglets at an equivalent developmental stage to human infants were equipped with the largest SVZ and a tremendous number of neuroblasts in the white matter, which may be sufficient in lesion repair without the dramatic stimulation of neurogenic machinery. It has yet to be determined whether neurogenesis and migrating neuroblasts play a role in repair after TBI and/or whether an alteration of normal migration during active postnatal population of brain regions is beneficial in species with gyrencephalic brains.

Traumatic brain injury (TBI) is the leading cause of acquired disability in children, yet innate repair mechanisms are incompletely understood. Given data from animal studies documenting neurogenesis in response to trauma and other insults, the authors investigated whether similar responses could be found in children of different ages after TBI.Immunohistochemistry was used to label doublecortin (DCX), a protein expressed by immature migrating neuroblasts (newborn neurons), in specimens from patients ranging in age from 3 weeks to 10 years who had died either after TBI or from other causes. Doublecortin-positive (DCX+) cells were examined in the subventricular zone (SVZ) and periventricular white matter (PWM) and were quantified within the granule cell layer (GCL) and subgranular zone (SGZ) of the dentate gyrus to determine if age and/or injury affect the number of DCX+ cells in these regions.The DCX+ cells decreased in the SVZ as patient age increased and were found in abundance around a focal subacute infarct in a 1-month-old non-TBI patient, but were scarce in all other patients regardless of age or history of trauma. The DCX+ cells in the PWM and dentate gyrus demonstrated a migratory morphology and did not co-localize with markers for astrocytes, microglia, or macrophages. In addition, there were significantly more DCX+ cells in the GCL and SGZ of the dentate gyrus in children younger than 1 year old than in older children. The density of immature migrating neuroblasts in infants (under 1 year of age) was significantly greater than in young children (2-6 years of age, p = 0.006) and older children (7-10 years of age, p = 0.007).The main variable influencing the number of migrating neuroblasts observed in the SVZ, PWM, and hippocampus was patient age. Trauma had no discernible effect on the number of migrating neuroblasts in this cohort of patients in whom death typically occurred within hours to days after TBI.

Photoaffinity labeling techniques have recently demonstrated that mammalian β 1 - and β 2 -adrenergic receptors reside on peptides of M r 62 000–64 000. These receptor peptides are susceptible to endogenous metalloproteinases which produce peptides of M r 30 000–55 000. Several proteinase inhibitors markedly attenuate this process, specifically EDTA and EGTA. In this study we investigated the functional significance of this proteolysis (and its inhibition) in the β 2 -adrenergic receptor-adenylate cyclase system derived from rat lung membranes. Membrane preparations containing proteolytically derived fragments of the receptor of M r 40000–55 000 are fully functional with respect to their ability to bind β-adrenergic antagonist radioligands such as [ 3 H]dihydroalprenolol and β-adrenergic antagonist photoaffinity reagents such as p- azido -m-[ 125 I ] iodobenzylcarazolol . They retain the ability to form a high-affinity, agonist-promoted, guanine nucleotide-sensitive complex thought to represent a ternary complex of agonist, receptor and guanine nucleotide regulatory protein. Nonetheless, after proteolysis, GTP is less able to revert this high-affinity receptor complex to one of lower affinity, and all aspects of adenylate cyclase stimulation are reduced. In addition, the functional integrity of the N protein in membranes prepared without proteinase inhibitors is reduced as assessed by reconstitution studies with the cyc[su− variant of S49 lymphoma cell membranes. These results suggest that endogenous proteolysis does not directly impair the ability of β-adrenergic receptors to either bind ligands or interact with the guanine nucleotide regulatory protein. However, they imply that endogenous proteolysis likely impairs the functionality of other components of the adenylate cyclase system, such as the nucleotide regulatory protein.