Biomarkers in traumatic brain injury (TBI): a review

Predicting Clinical Outcomes 7-10 Years after Severe Traumatic Brain Injury: Exploring the Prognostic Utility of the IMPACT Lab Model and Cerebrospinal Fluid UCH-L1 and MAP-2

BACKGROUND

Severe traumatic brain injury (TBI) is a major contributor to disability and mortality in the industrialized world. Outcomes of severe TBI are profoundly heterogeneous, complicating outcome prognostication. Several prognostic models have been validated for acute prediction of 6-month global outcomes following TBI (e.g., morbidity/mortality). In this preliminary observational prognostic study, we assess the utility of the International Mission on Prognosis and Analysis of Clinical Trials in TBI (IMPACT) Lab model in predicting longer term global and cognitive outcomes (7-10 years post injury) and the extent to which cerebrospinal fluid (CSF) biomarkers enhance outcome prediction.

METHODS

Very long-term global outcome was assessed in a total of 59 participants (41 of whom did not survive their injuries) using the Glasgow Outcome Scale-Extended and Disability Rating Scale. More detailed outcome information regarding cognitive functioning in daily life was collected from 18 participants surviving to 7-10 years post injury using the Cognitive Subscale of the Functional Independence Measure. A subset (n = 10) of these participants also completed performance-based cognitive testing (Digit Span Test) by telephone. The IMPACT lab model was applied to determine its prognostic value in relation to very long-term outcomes as well as the additive effects of acute CSF ubiquitin C-terminal hydrolase-L1 (UCH-L1) and microtubule associated protein 2 (MAP-2) concentrations.

RESULTS

The IMPACT lab model discriminated favorable versus unfavorable 7- to 10-year outcome with an area under the receiver operating characteristic curve of 0.80. Higher IMPACT lab model risk scores predicted greater extent of very long-term morbidity (β = 0.488 p = 0.000) as well as reduced cognitive independence (β =  - 0.515, p = 0.034). Acute elevations in UCH-L1 levels were also predictive of lesser independence in cognitive activities in daily life at very long-term follow-up (β = 0.286, p = 0.048). Addition of two CSF biomarkers significantly improved prediction of very long-term neuropsychological performance among survivors, with the overall model (including IMPACT lab score, UCH-L1, and MAP-2) explaining 89.6% of variance in cognitive performance 7-10 years post injury (p = 0.008). Higher acute UCH-L1 concentrations were predictive of poorer cognitive performance (β =  - 0.496, p = 0.029), whereas higher acute MAP-2 concentrations demonstrated a strong cognitive protective effect (β = 0.679, p = 0.010).

CONCLUSIONS

Although preliminary, results suggest that existing prognostic models, including models with incorporation of CSF markers, may be applied to predict outcome of severe TBI years after injury. Continued research is needed examining early predictors of longer-term outcomes following TBI to identify potential targets for clinical trials that could impact long-ranging functional and cognitive outcomes.

Blood biomarkers for predicting coagulopathy occurrence in patients with traumatic brain injury: a systematic review

Purpose: The occurrence of coagulopathy in patients with traumatic brain injury (TBI) is related to severe complications. The authors performed the first systematic review to investigate whether biomarkers can predict the occurrence of hypocoagulopathy or progressive hemorrhagic injury in patients with TBI. Methods: The authors included studies that performed a receiver operating characteristics analysis for the biomarker and provided a clear value along with the respective sensitivity and specificity. Additionally, they attempted to classify each biomarker, taking into account its physiological role. Results: Twelve studies were included. All biomarkers were protein molecules, except in one study that examined the prognostic role of glucose. Copeptin had the highest sensitivity, and S100A12 had the highest specificity in predicting coagulopathy, while IL-33 had the highest sensitivity and GALECTIN-3 had the highest specificity in predicting progressive hemorrhagic injury. Conclusion: The study of the role of biomarkers in predicting the occurrence of coagulopathy in patients with TBI remains in its infancy.

Biomarkers of Neuroinflammation in Traumatic Brain Injury

Traumatic brain injury (TBI) is characterized by neuroinflammation and structural damage leading to symptoms and altered brain function. Biomarkers are useful in understanding neuroinflammation and correlations with TBI sequalae. The purpose of this paper is to identify and discuss biomarkers of neuroinflammation used to study TBI and its sequalae. A systematic review was conducted using PubMed, CINAHL, Embase, and Web of Science. A total of 350 articles met criteria; 70 used biomarkers. PRISMA criteria were used for Quality Assessment. Articles included reviews (n = 17), case-control (n = 25), cross-sectional (n = 25) studies, and randomized controlled trials (n = 3). Twenty-seven biomarkers were identified, including inflammasomes, cytokines, neuropeptides, complement complexes, miRNA and exosomes, and glial cell-specific proteins. Biomarkers aid in predicting morbidity and mortality and advance our understanding of neuroinflammation in TBI. This systematic review advances our understanding of the neuroinflammatory response to better enable nurses and clinicians to provide informed care of TBI patients.

Progress Toward a Multiomic Understanding of Traumatic Brain Injury: A Review

Traumatic brain injury (TBI) is not a single disease state but describes an array of conditions associated with insult or injury to the brain. While some individuals with TBI recover within a few days or months, others present with persistent symptoms that can cause disability, neuropsychological trauma, and even death. Understanding, diagnosing, and treating TBI is extremely complex for many reasons, including the variable biomechanics of head impact, differences in severity and location of injury, and individual patient characteristics. Because of these confounding factors, the development of reliable diagnostics and targeted treatments for brain injury remains elusive. We argue that the development of effective diagnostic and therapeutic strategies for TBI requires a deep understanding of human neurophysiology at the molecular level and that the framework of multiomics may provide some effective solutions for the diagnosis and treatment of this challenging condition. To this end, we present here a comprehensive review of TBI biomarker candidates from across the multiomic disciplines and compare them with known signatures associated with other neuropsychological conditions, including Alzheimer’s disease and Parkinson’s disease. We believe that this integrated view will facilitate a deeper understanding of the pathophysiology of TBI and its potential links to other neurological diseases.

Central Nervous System Pericytes Contribute to Health and Disease

Successful neuroprotection is only possible with contemporary microvascular protection. The prevention of disease-induced vascular modifications that accelerate brain damage remains largely elusive. An improved understanding of pericyte (PC) signalling could provide important insight into the function of the neurovascular unit (NVU), and into the injury-provoked responses that modify cell-cell interactions and crosstalk. Due to sharing the same basement membrane with endothelial cells, PCs have a crucial role in the control of endothelial, astrocyte, and oligodendrocyte precursor functions and hence blood-brain barrier stability. Both cerebrovascular and neurodegenerative diseases impair oxygen delivery and functionally impair the NVU. In this review, the role of PCs in central nervous system health and disease is discussed, considering their origin, multipotency, functions and also dysfunction, focusing on new possible avenues to modulate neuroprotection. Dysfunctional PC signalling could also be considered as a potential biomarker of NVU pathology, allowing us to individualize therapeutic interventions, monitor responses, or predict outcomes.

Prognostic properties of the association between the S‑100B protein levels and the mean cerebral blood flow velocity in patients diagnosed with severe traumatic brain injury

Craniocerebral injury (CBI) is tissue damage caused by a sudden mechanical force. CBI can result in neurological, neuropsychological and psychiatric dysfunctions. Currently, the severity of CBI is assessed using the Glasgow Coma Scale, brain perfusion pressure measurements, transcranial Doppler tests and biochemical markers. This study aimed to determine the applicability of the S-100B protein levels and the time-averaged mean maximum cerebral blood flow velocity (V_mean) as a means of predicting the treatment outcomes of CBI in the first 4 days of hospitalization. The results validated the standard reference ranges previously proposed for the concentration of S-100B (0.05-0.23 µg/l) and the mean of cerebral blood flow velocity (30.9 to 74.1 cm/sec). The following stratification scheme was used to predict the success of treatment: Patients with a Glasgow Outcome Scale (GOS) score ≥4 or GOS <4 were stratified into ‘favorable’ and ‘unfavorable’ groups, respectively. The favorable group showed relatively constant levels of the S-100B protein close to the normal range and exhibited an increase in V_mean, but this was still within the normal range. The unfavorable group exhibited a high level of S-100B protein and increased V_mean outside of the normal ranges. The changes in the levels of S-100B in the unfavorable and favorable groups were -0.03 and -0.006 mg/l/h, respectively. Furthermore, the rate of decrease in the V_mean value in the unfavorable and favorable groups were -0.26 and -0.18 cm/sec/h, respectively. This study showed that constant levels of S-100B protein, even slightly above the normal range, associated with an increase in V_mean was indicative of a positive therapeutic outcome. However, additional research is required to obtain the appropriate statistical strength required for clinical practice.

Association Between Copeptin and Six-Month Neurologic Outcomes in Patients With Moderate Traumatic Brain Injury

Background

Copeptin has been reported as a predictive biomarker for the prognosis after traumatic brain injury (TBI). However, most of them were in patients with severe TBI and limited value in predicting outcomes in patients with moderate TBI defined as Glasgow Coma Scale (GCS) score from 9 to 12. We aimed to investigate the predictive value of copeptin in assessing the neurologic outcome following moderate TBI.

Methods

Patients were prospectively enrolled between May 2017 and November 2020. We consecutively measured plasma copeptin within 24 h after trauma, days 3, 5, and 7 using ELISA. The primary outcome was to correlate plasma copeptin levels with poor neurologic outcome at 6 months after moderate TBI. The secondary outcome was to compare the prognostic accuracy of copeptin and C-reactive protein (CRP) in assessing the outcome of patient.

Results

A total of 70 patients were included for the final analysis. The results showed that 29 patients (41.4%) experienced a poor neurologic outcome at 6 months. Multivariable logistic regression analysis revealed that increased copeptin (odds ration [OR] = 1.020, 95% CI: 1.005–1.036), GCS score of 9 or 10 (OR = 4.507, 95% CI: 1.266–16.047), and significant abnormal findings on CT (OR = 4.770; 95% CI: 1.133–20.076) were independent risk factors for poor outcomes. Consecutive plasma copeptin levels were significantly different according to outcomes (p < 0.001). Copeptin on day 7 exhibited better prognostic performance than CRP with an area under receiver operating characteristic curve (AUROC) difference of 0.179 (95% CI: 0.032–0.325) in predicting 6-month poor outcomes.

Conclusion

Plasma copeptin level can be a useful marker in predicting 6-month outcomes in patients with moderate TBI.

Diagnostic biomarker kinetics: how brain-derived biomarkers distribute through the human body, and how this affects their diagnostic significance: the case of S100B

Blood biomarkers of neurological diseases are often employed to rule out or confirm the presence of significant intracranial or cerebrovascular pathology or for the differential diagnosis of conditions with similar presentations (e.g., hemorrhagic vs. embolic stroke). More widespread utilization of biomarkers related to brain health is hampered by our incomplete understanding of the kinetic properties, release patterns, and excretion of molecules derived from the brain. This is, in particular, true for S100B, an astrocyte-derived protein released across the blood–brain barrier (BBB). We developed an open-source pharmacokinetic computer model that allows investigations of biomarker’s movement across the body, the sources of biomarker’s release, and its elimination. This model was derived from a general in silico model of drug pharmacokinetics adapted for protein biomarkers. We improved the model’s predictive value by adding realistic blood flow values, organ levels of S100B, lymphatic and glymphatic circulation, and glomerular filtration for excretion in urine. Three key variables control biomarker levels in blood or saliva: blood–brain barrier permeability, the S100B partition into peripheral organs, and the cellular levels of S100B in astrocytes. A small contribution to steady-state levels of glymphatic drainage was also observed; this mechanism also contributed to the uptake of organs of circulating S100B. This open-source model can also mimic the kinetic behavior of other markers, such as GFAP or NF-L. Our results show that S100B, after uptake by various organs from the systemic circulation, can be released back into systemic fluids at levels that do not significantly affect the clinical significance of venous blood or salivary levels after an episode of BBB disruption.

Heterogeneity in Blood Biomarker Trajectories After Mild TBI Revealed by Unsupervised Learning

Concussions, also known as mild traumatic brain injury (mTBI), are a growing health challenge. Approximately four million concussions are diagnosed annually in the United States. Concussion is a heterogeneous disorder in causation, symptoms, and outcome making precision medicine approaches to this disorder important. Persistent disabling symptoms sometimes delay recovery in a difficult to predict subset of mTBI patients. Despite abundant data, clinicians need better tools to assess and predict recovery. Data-driven decision support holds promise for accurate clinical prediction tools for mTBI due to its ability to identify hidden correlations in complex datasets. We apply a Locality-Sensitive Hashing model enhanced by varied statistical methods to cluster blood biomarker level trajectories acquired over multiple time points. Additional features derived from demographics, injury context, neurocognitive assessment, and postural stability assessment are extracted using an autoencoder to augment the model. The data, obtained from FITBIR, consisted of 301 concussed subjects (athletes and cadets). Clustering identified 11 different biomarker trajectories. Two of the trajectories (rising GFAP and rising NF-L) were associated with a greater risk of loss of consciousness or post-traumatic amnesia at onset. The ability to cluster blood biomarker trajectories enhances the possibilities for precision medicine approaches to mTBI.

GFAP and S100B: What You Always Wanted to Know and Never Dared to Ask

Traumatic brain injury (TBI) is a major global health issue, with outcomes spanning from intracranial bleeding, debilitating sequelae, and invalidity with consequences for individuals, families, and healthcare systems. Early diagnosis of TBI by testing peripheral fluids such as blood or saliva has been the focus of many research efforts, leading to FDA approval for a bench-top assay for blood GFAP and UCH-L1 and a plasma point-of-care test for GFAP. The biomarker S100B has been included in clinical guidelines for mTBI (mTBI) in Europe. Despite these successes, several unresolved issues have been recognized, including the robustness of prior data, the presence of biomarkers in tissues beyond the central nervous system, and the time course of biomarkers in peripheral body fluids. In this review article, we present some of these issues and provide a viewpoint derived from an analysis of existing literature. We focus on two astrocytic proteins, S100B and GFAP, the most commonly employed biomarkers used in mTBI. We also offer recommendations that may translate into a broader acceptance of these clinical tools.

Advances in Traumatic Brain Injury Biomarkers

Traumatic brain injury (TBI) is increasingly a major cause of disability across the globe. The current methods of diagnosis are inadequate at classifying patients and prognosis. TBI is a diagnostic and therapeutic challenge. There is no Food and Drug Administration (FDA)-approved treatment for TBI yet. It took about 16 years of preclinical research to develop accurate and objective diagnostic measures for TBI. Two brain-specific protein biomarkers, namely, ubiquitin C-terminal hydrolase-L1 and glial fibrillary acidic protein, have been extensively characterized. Recently, the two biomarkers were approved by the FDA as the first blood-based biomarker, Brain Trauma Indicator™ (BTI™), via the Breakthrough Devices Program. This scoping review presents (i) TBI diagnosis challenges, (ii) the process behind the FDA approval of biomarkers, and (iii) known unknowns in TBI biomarker biology. The current lag in TBI incidence and hospitalization can be reduced if digital biomarkers such as hard fall detection are standardized and used as a mechanism to alert paramedics to an unresponsive trauma patient.

Development of an electrochemical impedance spectroscopy based biosensor for detection of ubiquitin C-Terminal hydrolase L1

Year over year, the incidence of traumatic brain injury (TBI) in the population is dramatically increasing; thus, timely diagnosis is crucial for improving patient outcomes in the clinic. Ubiquitin C-terminal hydrolase L1 (UCH-L1), a blood-based biomarker, has been approved by the FDA as a promising quantitative indicator of mild TBI that arises in blood serum shortly after injury. Current gold standard techniques for its quantitation are time-consuming and require specific laboratory equipment. Hence, development of a hand-held device is an attractive alternative. In this study, we report a novel system for rapid, one-step electrochemical UCH-L1 detection. Electrodes were functionalized with anti-UCH-L1 antibody, which was used as a molecular recognition element for selective sensing of UCH-L1. Electrochemical impedance spectroscopy (EIS) was used as a transduction method to quantify its binding. When the electrode was incubated with different concentrations of UCH-L1, impedance signal increased against a concentration gradient with high logarithmic correlation. Upon single-frequency analysis, a second calibration curve with greater signal to noise was obtained, which was used to distinguish physiologically relevant concentrations of UCH-L1. Notably, our system could detect UCH-L1 within 5 min, without a washing step nor bound/free separation, and had resolution across concentrations ranging from 1 pM to 1000 pM within an artificial serum sample. These attributes, together with the miniaturization potential afforded by an impedimetric sensing platform, make this platform an attractive candidate for scale-up as a device for rapid, on-site detection of TBI. These findings may aid in the future development of sensing systems for quantitative TBI detection.

Pro-resolving lipid mediators in traumatic brain injury: emerging concepts and translational approach

Despite the high mortality and disability associated with traumatic brain injury (TBI), effective pharmacologic treatments are lacking. Of emerging interest, bioactive lipids, including specialized pro-resolving lipid mediators of inflammation (SPMs), act to attenuate inflammation after injury resolution. The SPM lipidome may serve as a biomarker of disease and predictor of clinical outcomes, and the use of exogenous SPM administration represents a novel therapeutic strategy for TBI. This review article provides a comprehensive discussion of the current pre-clinical and clinical literature supporting the importance of bioactive lipids, including SPMs, in TBI recovery. We additionally propose a translational approach to answer important clinical and scientific questions to advance the study of bioactive lipids and SPMs towards clinical research. Given the morbidity and mortality associated with TBI with limited treatment options, novel approaches are needed.

Proteomics and metabolomics approach in adult and pediatric glioma diagnostics

The diagnosis of glioma is mainly based on imaging methods that do not distinguish between stage and subtype prior to histopathological analysis. Patients with gliomas are generally diagnosed in the symptomatic stage of the disease. Additionally, healing scar tissue may be mistakenly identified based on magnetic resonance imaging (MRI) as a false positive tumor recurrence in postoperative patients. Current knowledge of molecular alterations underlying gliomagenesis and identification of tumoral biomarkers allow for their use as discriminators of the state of the organism. Moreover, a multiomics approach provides the greatest spectrum and the ability to track physiological changes and can serve as a minimally invasive method for diagnosing asymptomatic gliomas, preceding surgery and allowing for the initiation of prophylactic treatment. It is important to create a vast biomarker library for adults and pediatric patients due to their metabolic differences. This review focuses on the most promising proteomic, metabolomic and lipidomic glioma biomarkers, their pathways, the interactions, and correlations that can be considered characteristic of tumor grade or specific subtype.

An Interplay Between Post-Traumatic Epilepsy and Associated Cognitive Decline: A Systematic Review

Background

Post-traumatic epilepsy (PTE) is a devastating neurological outcome of traumatic brain injury (TBI), which may negatively impact the quality of life of patients with TBI, and may impose a huge socioeconomic burden. This burden may be due to long-term functional outcomes associated with PTE, particularly cognitive dysfunction. To date, the relationship between TBI and PTE remains unclear, with little known about how the effect of their link on cognitive function as well.

Objective

Thus, this systematic review aimed at elucidating the relationship between PTE and cognitive impairment in adults after TBI based on available clinical studies, in hopes to aid in the development of therapeutic strategies for PTE.

Methods

A systematic literature search was performed using 6 databases; MEDLINE, Embase, CINAHL, Psych INFO, Web of Science, and Cochrane to retrieve relevant clinical studies investigating the link between PTE and cognition in the context of TBI. The Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of relevant studies.

Results

A total of six eligible studies were included for critical appraisal in this review after performing the inclusion and exclusion criteria, which involved 1,100 individuals, from 1996 to 2021. The selected studies were derived from the civilian and military population, with a follow-up period that ranged from 6 months to 35 years. The average quality of the involved studies was moderate (6.6, SD = 1.89). Five out of six studies found poorer cognitive performance in people with PTE, compared with those without PTE. Although the association between PTE and cognitive impairment was insignificant after controlling for specific covariates, there was a statistical trend toward significance.

Conclusion

This systematic review suggests that there may be a possible link between PTE and cognitive decline in TBI patients, with the latter being reported to occur up to 35 years post injury. Variations in sample sizes, follow-up periods, and neuropsychological assessment tools may be the limitations affecting the interpretation and significance of this relationship. Therefore, future studies with standard cognitive assessment tools may be warranted to solidify the link between TBI-PTE-cognitive dysfunction, prior to the development of therapeutic strategies.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020221702, prospero identifier: CRD42020221702.

Advances in point-of-care platforms for traumatic brain injury: recent developments in diagnostics

Traumatic brain injury (TBI) is a major cause of mortality and morbidity, affecting 2 million people annually in the US alone, with direct and indirect costs of $76.3 billion per year. TBI is a progressive disease with no FDA-approved drug for treating patients. Early, accurate and rapid diagnosis can have significant implications for successful triaging and intervention. Unfortunately, current clinical tests for TBI rely on CT scans and MRIs, both of which are expensive, time-consuming, and not accessible to everyone. Recent evidence of biofluid-based biomarkers being released right after a TBI incident has ignited interest in developing point-of-care (POC) platforms for early and on-site TBI diagnosis. These efforts face many challenges to accurate, sensitive, and specific diagnosis and monitoring of TBI. This review includes a deep dive into the latest advances in chemical, mechanical, electrical, and optical sensing systems that hold promise for TBI-POC diagnostic testing platforms. It also focuses on the performance of these proposed biosensors compared to biofluid-based orthodox diagnostic techniques in terms of sensitivity, specificity, and limits of detection. Finally, it examines commercialized TBI-POCs present in the market, the challenges associated with them, and the future directions and prospects of these technologies and the field.

The role of S100B/RAGE-enhanced ADAM17 activation in endothelial glycocalyx shedding after traumatic brain injury

Background

Traumatic brain injury (TBI) remains one of the main causes for disability and death worldwide. While the primary mechanical injury cannot be avoided, the prevention of secondary injury is the focus of TBI research. Present study aimed to elucidate the effects and mechanisms of S100B and its receptor RAGE on mediating secondary injury after TBI.

Methods

This study established TBI animal model by fluid percussion injury in rats, cell model by stretch-injured in astrocytes, and endothelial injury model with conditioned medium stimulation. Pharmacological intervention was applied to interfere the activities of S100B/RAGE/ADAM17 signaling pathway, respectively. The expressions or contents of S100B, RAGE, syndecan-1 and ADAM17 in brain and serum, as well as in cultured cells and medium, were detected by western blot. The distribution of relative molecules was observed with immunofluorescence.

Results

We found that TBI could activate the release of S100B, mostly from astrocytes, and S100B and RAGE could mutually regulate their expression and activation. Most importantly, present study revealed an obvious increase of syndecan-1 in rat serum or in endothelial cultured medium after injury, and a significant decrease in tissue and in cultured endothelial cells, indicating TBI-induced shedding of endothelial glycocalyx. The data further proved that the activation of S100B/RAGE signaling could promote the shedding of endothelial glycocalyx by enhancing the expression, translocation and activity of ADAM17, an important sheddase, in endothelial cells. The damage of endothelial glycocalyx consequently aggravated blood brain barrier (BBB) dysfunction and systemic vascular hyper-permeability, overall resulting in secondary brain and lung injury.

Conclusions

TBI triggers the activation of S100B/RAGE signal pathway. The regulation S100B/RAGE on ADAM17 expression, translocation and activation further promotes the shedding of endothelial glycocalyx, aggravates the dysfunction of BBB, and increases the vascular permeability, leading to secondary brain and lung injury. Present study may open a new corridor for the more in-depth understanding of the molecular processes responsible for cerebral and systemic vascular barrier impairment and secondary injury after TBI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02412-2.

Blood Biomarkers and Structural Imaging Correlations Post-Traumatic Brain Injury: A Systematic Review

BACKGROUND

Blood biomarkers are of increasing importance in the diagnosis and assessment of traumatic brain injury (TBI). However, the relationship between them and lesions seen on imaging remains unclear.

OBJECTIVE

To perform a systematic review of the relationship between blood biomarkers and intracranial lesion types, intracranial lesion injury patterns, volume/number of intracranial lesions, and imaging classification systems.

METHODS

We searched Medical Literature Analysis and Retrieval System Online, Excerpta Medica dataBASE, and Cumulative Index to Nursing and Allied Health Literature from inception to May 2021, and the references of included studies were also screened. Heterogeneity in study design, biomarker types, imaging modalities, and analyses inhibited quantitative analysis, with a qualitative synthesis presented.

RESULTS

Fifty-nine papers were included assessing one or more biomarker to imaging comparisons per paper: 30 assessed imaging classifications or injury patterns, 28 assessed lesion type, and 11 assessed lesion volume or number. Biomarker concentrations were associated with the burden of brain injury, as assessed by increasing intracranial lesion volume, increasing numbers of traumatic intracranial lesions, and positive correlations with imaging classification scores. There were inconsistent findings associating different biomarkers with specific imaging phenotypes including diffuse axonal injury, cerebral edema, and intracranial hemorrhage.

CONCLUSION

Blood-based biomarker concentrations after TBI are consistently demonstrated to correlate burden of intracranial disease. The relation with specific injury types is unclear suggesting a lack of diagnostic specificity and/or is the result of the complex and heterogeneous nature of TBI.

Salivary Biomarkers as Indicators of TBI Diagnosis and Prognosis: A Systematic Review

BACKGROUND AND OBJECTIVE

Traumatic brain injuries are physical injuries to the head that result in disruptions to normal brain function. Diagnostic tools such as computed tomography scans have commonly been used to detect traumatic brain injuries but are costly and not ubiquitously available. Recent research on diagnostic alternatives has focused on using salivary biomarkers, but there is no consensus on the utility of these methods.  The objective of this manuscript is to address the gap in the literature pertaining to the effectiveness of salivary biomarkers for TBI diagnosis and prognosis.

METHODS

A systematic review was conducted between November 2020 and October 2021 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Six databases were searched using the terms "traumatic brain injury," "TBI," "saliva," and "biomarkers." Literature published prior to 2010 was excluded, and two authors reviewed each full-text article to ensure its relevance.

RESULTS

A total of 18 articles were included in this review, with nine articles on salivary microRNA, three on salivary hormones, three on salivary extracellular vesicles, and three on salivary proteins.

CONCLUSIONS

Studies reported changes in salivary biomarkers after traumatic brain injuries and indicated a possible link between salivary biomarker expression and traumatic brain injury severity. However, it is unclear the degree to which salivary biomarkers accurately predict traumatic brain injury diagnosis and prognosis; some studies reported significant associations while others reported weaker associations. More research into the robustness of salivary biomarkers is needed to fully elucidate their utility for the traumatic brain injury population.

Micro-RNA levels and symptom profile after mild traumatic brain injury: A longitudinal cohort study

Micro riboneucleic acids (miRNAs) may be transcribed after brain injury and be detectable in plasma. This study aimed to assess the discriminative ability of seven miRNAs in plasma to differentiate between patients with mild traumatic brain injury (mTBI) and healthy controls. Changes in miRNA levels over 28 days were compared to changes in self-reported symptom profile. This was a prospective cohort study with longitudinal measurements of miRNA levels and symptom self-report. The Rivermead Post-Concussion Symptom Questionnaire (RPQ) was used to determine symptom severity. Mean normalised expression ratios (NER) of miRNAs at day 0 between mTBI and healthy controls were compared. An analysis of response profiles compared the response over time of miRNA species with RPQ symptom severity. miRNA levels of subjects who were defined to have "recovered" on Day 7 and 28 were compared to "non-recovered" subjects. There were 28 mTBI patients and 30 healthy controls included for analysis. Symptom severity was significantly higher on the day of injury among mTBI subjects (p < 0.001), and miRNA 32-5p levels were also higher (p = 0.009). Change of miRNA levels were similar to RPQ change at Day 7, but significantly different at Day 28. Differences were observed among miRNA levels of recovered subjects. This study demonstrated differences in miRNA levels among mTBI subjects compared to healthy controls and different miRNA levels among those who had recovered compared to those reporting symptoms. The change in profiles of miRNAs was different to symptom severity, suggesting that the two measures reflect different aspects of brain injury and recovery.

Behavioral and Cognitive Aspects of Concussion

PURPOSE OF REVIEW

This review provides the reader with an overview of concussion and mild traumatic brain injury (TBI). Key aspects of the pathophysiology, signs, and symptoms, treatment and rehabilitation, and recovery from concussion/mild TBI are reviewed with an emphasis on the variety of factors that may contribute to cognitive concerns following injury.

RECENT FINDINGS

Concussion remains a clinical diagnosis based on symptoms that occur in the immediate aftermath of an applied force and in the hours, days, and weeks thereafter. Although advances have been made in advanced diagnostics, including neuroimaging and fluid biomarkers in hopes of developing objective indicators of injury, such markers currently lack sufficient specificity to be used in clinical diagnostics. The symptoms of concussion are heterogeneous and may be seen to form subtypes, each of which suggests a targeted rehabilitation by the interdisciplinary team. Although the majority of patients with concussion recover within the first 30 to 90 days after injury, some have persistent disabling symptoms. The concept of postconcussion syndrome, implying a chronic syndrome of injury-specific symptoms, is replaced by a broader concept of persistent symptoms after concussion. This concept emphasizes the fact that most persistent symptoms have their basis in complex somatic, cognitive, psychiatric, and psychosocial factors related to risk and resilience. This framework leads to the important conclusion that concussion is a treatable injury from which nearly all patients can be expected to recover.

SUMMARY

Concussion/mild TBI is a significant public health problem in civilian, military, and organized athletic settings. Recent advances have led to a better understanding of underlying pathophysiology and symptom presentation and efficacious treatment and rehabilitation of the resulting symptoms. An interdisciplinary team is well-positioned to provide problem-oriented, integrated care to facilitate recovery and to advance the evidence base supporting effective practice in diagnosis, treatment, and prevention.

Usability of the Level of the S100B Protein, the Gosling Pulsatility Index, and the Jugular Venous Oxygen Saturation for the Prediction of Mortality and Morbidity in Patients with Severe Traumatic Brain Injury

The high frequency of traumatic brain injury imposes severe economic stress on health and insurance services. The objective of this study was to analyze the association between the serum S100B protein, the Gosling pulsatility index (PI), and the level of oxygen saturation at the tip of the internal jugular vein (SjVO2%) in patients diagnosed with severe TBI. The severity of TBI was assessed by a GCS score ≤ 8 stratified by Glasgow outcome scale (GOS) measured on the day of discharge from the hospital. Two groups were included: GOS < 4 (unfavorable group (UG)) and GOS ≥ 4 (favorable group (UG)). S100B levels were higher in the UG than in the FG. PI levels in the UG were also substantially higher than in the FG. There were similar levels of SjVO2 in the two groups. This study confirmed that serum S100B levels were higher in patients with unfavorable outcomes than in those with favorable outcomes. Moreover, a clear demarcation in PI between unfavorable and FGs was observed. This report shows that mortality and morbidity rates in patients with traumatic brain injury can be assessed within the first 4 days of hospitalization using the S100B protein, PI values, and SjVO2.

Extracellular vesicles as distinct biomarker reservoirs for mild traumatic brain injury diagnosis

Mild traumatic brain injury does not currently have a clear molecular diagnostic panel to either confirm the injury or to guide its treatment. Current biomarkers for traumatic brain injury rely mainly on detecting circulating proteins in blood that are associated with degenerating neurons, which are less common in mild traumatic brain injury, or with broad inflammatory cascades which are produced in multiple tissues and are thus not brain specific. To address this issue, we conducted an observational cohort study designed to measure a protein panel in two compartments—plasma and brain-derived extracellular vesicles—with the following hypotheses: (i) each compartment provides independent diagnostic information and (ii) algorithmically combining these compartments accurately classifies clinical mild traumatic brain injury. We evaluated this hypothesis using plasma samples from mild (Glasgow coma scale scores 13–15) traumatic brain injury patients (n = 47) and healthy and orthopaedic control subjects (n = 46) to evaluate biomarkers in brain-derived extracellular vesicles and plasma. We used our Track Etched Magnetic Nanopore technology to isolate brain-derived extracellular vesicles from plasma based on their expression of GluR2, combined with the ultrasensitive digital enzyme-linked immunosorbent assay technique, Single-Molecule Array. We quantified extracellular vesicle-packaged and plasma levels of biomarkers associated with two categories of traumatic brain injury pathology: neurodegeneration and neuronal/glial damage (ubiquitin C-terminal hydrolase L1, glial fibrillary acid protein, neurofilament light and Tau) and inflammation (interleukin-6, interleukin-10 and tumour necrosis factor alpha). We found that GluR2+ extracellular vesicles have distinct biomarker distributions than those present in the plasma. As a proof of concept, we showed that using a panel of biomarkers comprised of both plasma and GluR2+ extracellular vesicles, injured patients could be accurately classified versus non-injured patients.

Serum biomarkers in severe paediatric traumatic brain injury-a narrative review

Severe traumatic brain injury continues to present complex management and prediction challenges for the clinician. While there is some evidence that better systems of care can improve outcome, multiple multi-centre randomised controlled trials of specific therapies have consistently failed to show benefit. In addition, clinicians are challenged in attempting to accurately predict which children will recover well and which children will have severe and persisting neurocognitive deficits. Traumatic brain injury is vastly heterogeneous and so it is not surprising that one therapy or approach, when applied to a mixed cohort of children in a clinical trial setting, has yielded disappointing results. Children with severe traumatic brain injury have vastly different brain injury pathologies of widely varying severity, in any number of anatomical locations at what may be disparate stages of brain development. This heterogeneity may also explain why clinicians are unable to accurately predict outcome. Biomarkers are objective molecular signatures of injury that are released following traumatic brain injury and may represent a way of unifying the heterogeneity of traumatic brain injury into a single biosignature. Biomarkers hold promise to diagnose brain injury severity, guide intervention selection for clinical trials, or provide vital prognostic information so that early intervention and rehabilitation can be planned much earlier in the course of a child's recovery. Serum S100B and serum NSE levels show promise as a diagnostic tool with biomarker levels significantly higher in children with severe TBI including children with inflicted and non-inflicted head injury. Serum S100B and serum NSE also show promise as a predictor of neurodevelopmental outcome. The role of biomarkers in traumatic brain injury is an evolving field with the potential for clinical application within the next few years.

Biofluid Biomarkers in Traumatic Brain Injury: A Systematic Scoping Review

Emerging evidence suggests that biofluid-based biomarkers have diagnostic and prognostic potential in traumatic brain injuries (TBI). However, owing to the lack of a conceptual framework or comprehensive review, it is difficult to visualize the breadth of materials that might be available. We conducted a systematic scoping review to map and categorize the evidence regarding biofluid-based biochemical markers of TBI. A comprehensive search was undertaken in January 2019. Of 25,354 records identified through the literature search, 1036 original human studies were included. Five hundred forty biofluid biomarkers were extracted from included studies and classified into 19 distinct categories. Three categories of biomarkers including cytokines, coagulation tests, and nerve tissue proteins were investigated more than others and assessed in almost half of the studies (560, 515, and 502 from 1036 studies, respectively). S100 beta as the most common biomarker for TBI was tested in 21.2% of studies (220 articles). Cortisol was the only biomarker measured in blood, cerebrospinal fluid, urine, and saliva. The most common sampling time was at admission and within 24 h of injury. The included studies focused mainly on biomarkers from blood and central nervous system sources, the adult population, and severe and blunt injuries. The most common outcome measures used in studies were changes in biomarker concentration level, Glasgow coma scale, Glasgow outcome scale, brain computed tomography scan, and mortality rate. Biofluid biomarkers could be clinically helpful in the diagnosis and prognosis of TBI. However, there was no single definitive biomarker with accurate characteristics. The present categorization would be a road map to investigate the biomarkers of the brain injury cascade separately and detect the most representative biomarker of each category. Also, this comprehensive categorization could provide a guiding framework to design combined panels of multiple biomarkers.

Blood biomarkers for mild traumatic brain injury: a selective review of unresolved issues

Background

The use of blood biomarkers after mild traumatic brain injury (mTBI) has been widely studied. We have identified eight unresolved issues related to the use of five commonly investigated blood biomarkers: neurofilament light chain, ubiquitin carboxy-terminal hydrolase-L1, tau, S100B, and glial acidic fibrillary protein. We conducted a focused literature review of unresolved issues in three areas: mode of entry into and exit from the blood, kinetics of blood biomarkers in the blood, and predictive capacity of the blood biomarkers after mTBI.

Findings

Although a disruption of the blood brain barrier has been demonstrated in mild and severe traumatic brain injury, biomarkers can enter the blood through pathways that do not require a breach in this barrier. A definitive accounting for the pathways that biomarkers follow from the brain to the blood after mTBI has not been performed. Although preliminary investigations of blood biomarkers kinetics after TBI are available, our current knowledge is incomplete and definitive studies are needed. Optimal sampling times for biomarkers after mTBI have not been established. Kinetic models of blood biomarkers can be informative, but more precise estimates of kinetic parameters are needed. Confounding factors for blood biomarker levels have been identified, but corrections for these factors are not routinely made. Little evidence has emerged to date to suggest that blood biomarker levels correlate with clinical measures of mTBI severity. The significance of elevated biomarker levels thirty or more days following mTBI is uncertain. Blood biomarkers have shown a modest but not definitive ability to distinguish concussed from non-concussed subjects, to detect sub-concussive hits to the head, and to predict recovery from mTBI. Blood biomarkers have performed best at distinguishing CT scan positive from CT scan negative subjects after mTBI.

Biomarkers for Traumatic Brain Injury: Data Standards and Statistical Considerations

Recent biomarker innovations hold potential for transforming diagnosis, prognostic modeling, and precision therapeutic targeting of traumatic brain injury (TBI). However, many biomarkers, including brain imaging, genomics, and proteomics, involve vast quantities of high-throughput and high-content data. Management, curation, analysis, and evidence synthesis of these data are not trivial tasks. In this review, we discuss data management concepts and statistical and data sharing strategies when dealing with biomarker data in the context of TBI research. We propose that application of biomarkers involves three distinct steps-discovery, evaluation, and evidence synthesis. First, complex/big data has to be reduced to useful data elements at the stage of biomarker discovery. Second, inferential statistical approaches must be applied to these biomarker data elements for assessment of biomarker clinical utility and validity. Last, synthesis of relevant research is required to support practice guidelines and enable health decisions informed by the highest quality, up-to-date evidence available. We focus our discussion around recent experiences from the International Traumatic Brain Injury Research (InTBIR) initiative, with a specific focus on four major clinical projects (Transforming Research and Clinical Knowledge in TBI, Collaborative European NeuroTrauma Effectiveness Research in TBI, Collaborative Research on Acute Traumatic Brain Injury in Intensive Care Medicine in Europe, and Approaches and Decisions in Acute Pediatric TBI Trial), which are currently enrolling subjects in North America and Europe. We discuss common data elements, data collection efforts, data-sharing opportunities, and challenges, as well as examine the statistical techniques required to realize successful adoption and use of biomarkers in the clinic as a foundation for precision medicine in TBI.

Doxycycline alleviates acute traumatic brain injury by suppressing neuroinflammation and apoptosis in a mouse model

Traumatic brain injury (TBI) is one of the significant causes of death among young people worldwide. Doxycycline (DOX), an antibiotic with anti-inflammatory effects, has not been used as a therapeutic agent to modify the inflammatory response after the traumatic brain injury. In this study, intraperitoneal administration of DOX reduced significantly the acute inflammatory markers like IL-6 and CD3, microglial migration to the damaged area marked with Iba-1, and neuronal apoptosis assessed with TUNEL assay at 72 h after the trauma. The low dose, 10 mg/kg of DOX had a dominant anti-inflammatory effect; while the high dose, 100 mg/kg of DOX, was more effective in decreasing neuronal apoptosis. In early hours after the head trauma, use of a low dose (10 mg/kg) of DOX for decreasing the acute form of inflammation followed by a high dose (100 mg/kg) for the anti-apoptotic effects particularly in severe head traumas, would be a promising approach to alleviate the brain injury.

Neurocognitive Outcomes and Their Diffusion Tensor Imaging Correlates in Children With Mild Traumatic Brain Injury

This study aimed to assess the neurocognitive outcomes and their diffusion tensor imaging correlates in children (aged 6-16 years) with mild traumatic brain injury. This prospective analysis included 74 children with mild traumatic brain injury (52 boys; mean age: 9.5 [±2.7] years). Wechsler Intelligence Scale for Children-Indian adaptation (WISC-IV), Child Behavior Checklist, and Children's Sleep Habits Questionnaire were administered for 57 cases (at 3 months postinjury) and 51 controls of similar age. The findings of diffusion tensor imaging (done within 7 days of injury) were correlated with various WISC-IV indices. The presenting features at the time of injury were loss of consciousness (53%), confusion or disorientation (47%), and post-traumatic amnesia (10%). Other features in the acute phase included drowsiness (86%), headache (78%), balance problems (62%), nausea (47%), fatigue (45%), vomiting (35%), nasal or ear bleed (12%), sensitivity to sound and light (12%), etc. At 3 months postinjury, the children with mild traumatic brain injury performed poorly in terms of Intelligence Quotient, perceptual reasoning index, and processing speed index as compared to controls. Based on the Child Behavior Checklist, 17% of children with mild traumatic brain injury had internalizing behavioral problems in comparison with 4% of controls. Prevalence of poor sleepers in the mild traumatic brain injury cohort and controls was 12.3% and 2% respectively. Headache, reduced attention span, and fatigue were common postconcussion symptoms. There was a positive correlation between right uncinate fasciculus fractional anisotropy and verbal comprehension index (r = 0.32; P < .05).

Novel severe traumatic brain injury blood outcome biomarkers identified with proximity extension assay

OBJECTIVES

Severe traumatic brain injury (sTBI) patients suffer high mortality. Accurate prognostic biomarkers have not been identified. In this exploratory study, we performed targeted proteomics on plasma obtained from sTBI patients to identify potential outcome biomarkers.

METHODS

Blood sample was collected from patients admitted to the ICU suffering a sTBI, using standardized clinical and computerized tomography (CT) imaging criteria. Age- and sex-matched healthy control subjects and sTBI patients were enrolled. Targeted proteomics was performed on plasma with proximity extension assays (1,161 proteins).

RESULTS

Cohorts were well-balanced for age and sex. The majority of sTBI patients were injured in motor vehicle collisions and the most frequent head CT finding was subarachnoid hemorrhage. Mortality rate for sTBI patients was 40%. Feature selection identified the top performing 15 proteins for identifying sTBI patients from healthy control subjects with a classification accuracy of 100%. The sTBI proteome was dominated by markers of vascular pathology, immunity/inflammation, cell survival and macrophage/microglia activation. Receiver operating characteristic (ROC) curve analyses demonstrated areas-under-the-curves (AUC) for identifying sTBI that ranged from 0.870-1.000 (p≤0.005). When mortality was used as outcome, ROC curve analyses identified the top 3 proteins as Willebrand factor (vWF), Wnt inhibitory factor-1 (WIF-1), and colony stimulating factor-1 (CSF-1). Combining vWF with either WIF-1 or CSF-1 resulted in excellent mortality prediction with AUC of 1.000 for both combinations (p=0.011).

CONCLUSIONS

Targeted proteomics with feature classification and selection distinguished sTBI patients from matched healthy control subjects. Two protein combinations were identified that accurately predicted sTBI patient mortality. Our exploratory findings require confirmation in larger sTBI patient populations.

Circulating brain injury biomarkers increase after endoscopic surgery for pituitary tumors

Pituitary tumors and subsequent treatment with endoscopic transsphenoidal surgery (ETSS) may cause injury to suprasellar structures, causing long-term fatigue and neurocognitive impairment. A method to quantify brain injury after ETSS is not available. In this prospective, exploratory study of patients undergoing ETSS for pituitary tumors, a novel approach to detect possible neuronal damage is presented. Plasma concentrations of brain injury biomarkers (glial fibrillary acidic protein [GFAP], tau, and neurofilament light [NFL]) were measured the day before surgery, immediately after surgery, at day 1 and 5, and at 6 and 12 months after surgery, using enzyme-linked immunosorbent assays. The association between the increase of biomarkers with preoperative tumor extension and postoperative patient-perceived fatigue was evaluated. Suprasellar tumor extension was assessed from MRI scans, and self-perceived fatigue was assessed using the Multidimensional Fatigue Inventory before and 6 months after surgery. Thirty-five patients were included in the analysis. Compared to baseline, GFAP showed a maximal increase at day 1 after surgery (p = 0.0005), tau peaked postoperatively on the day of surgery (p = 0.019), and NFL reached its maximum at day 5 after surgery (p < 0.0001). The increase in GFAP correlated with preoperative chiasmal compression (p = 0.020). The increase in tau was correlated with preoperative chiasmal (p = 0.011) and hypothalamus compression (p = 0.016), and fatigue score 6 months after surgery (p = 0.016). In conclusion, the concentrations of brain injury biomarkers in blood increased after ETSS for pituitary tumors. The results indicate that postoperative plasma GFAP and tau might reflect astroglial and neuronal damage after ETSS.

Blood Biomarkers Relate to Cognitive Performance Years after Traumatic Brain Injury in Service Members and Veterans

OBJECTIVE

This study examines the relationship of serum total tau, neurofilament light (NFL), ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), and glial fibrillary acidic protein (GFAP) with neurocognitive performance in service members and veterans with a history of traumatic brain injury (TBI).

METHOD

Service members (n = 488) with a history of uncomplicated mild (n = 172), complicated mild, moderate, severe, or penetrating TBI (sTBI; n = 126), injured controls (n = 116), and non-injured controls (n = 74) prospectively enrolled from Military Treatment Facilities. Participants completed a blood draw and neuropsychological assessment a year or more post-injury. Six neuropsychological composite scores and presence/absence of mild neurocognitive disorder (MNCD) were evaluated. Within each group, stepwise hierarchical regression models were conducted.

RESULTS

Within the sTBI group, increased serum UCH-L1 was related to worse immediate memory and delayed memory (R2Δ = .065-.084, ps < .05) performance, while increased GFAP was related to worse perceptual reasoning (R2Δ = .030, p = .036). Unexpectedly, within injured controls, UCH-L1 and GFAP were inversely related to working memory (R2Δ = .052-.071, ps < .05), and NFL was related to executive functioning (R2Δ = .039, p = .021) and MNCD (Exp(B) = 1.119, p = .029).

CONCLUSIONS

Results suggest GFAP and UCH-L1 could play a role in predicting poor cognitive outcome following complicated mild and more severe TBI. Further investigation of blood biomarkers and cognition is warranted.

High-Sensitivity C-Reactive Protein is a Prognostic Biomarker of Six-Month Disability after Traumatic Brain Injury: Results from the TRACK-TBI Study

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 < 0.001). Longitudinally, hsCRP was significantly higher in the first 2 weeks for subjects with death/severe disability (GOSE <5) compared with those with moderate disability/good recovery (GOSE ≥5); AUC was highest at 2 weeks (AUC = 0.892). Combining hsCRP and GFAP at 2 weeks produced AUC = 0.939 for prediction of disability. Serum hsCRP measured within 2 weeks of TBI is a prognostic biomarker for disability 6 months later. hsCRP may have utility as a biomarker of target engagement for anti-inflammatory therapies.

Neurologic Assessment of the Neurocritical Care Patient

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

Molecular and Diffusion Tensor Imaging Biomarkers of Traumatic Brain Injury: Principles for Investigation and Integration

The last 20 years have seen the advent of new technologies that enhance the diagnosis and prognosis of traumatic brain injury (TBI). There is recognition that TBI affects the brain beyond initial injury, in some cases inciting a progressive neuropathology that leads to chronic impairments. Medical researchers are now searching for biomarkers to detect and monitor this condition. Perhaps the most promising developments are in the biomolecular and neuroimaging domains. Molecular assays can identify proteins indicative of neuronal injury and/or degeneration. Diffusion imaging now allows sensitive evaluations of the brain's cellular microstructure. As the pace of discovery accelerates, it is important to survey the research landscape and identify promising avenues of investigation. In this review, we discuss the potential of molecular and diffusion tensor imaging (DTI) biomarkers in TBI research. Integration of these technologies could advance models of disease prognosis, ultimately improving care. To date, however, few studies have explored relationships between molecular and DTI variables in patients with TBI. Here, we provide a short primer on each technology, review the latest research, and discuss how these biomarkers may be incorporated in future studies.

Post-traumatic Headache and Mild Traumatic Brain Injury: Brain Networks and Connectivity

PURPOSE OF REVIEW

Post-traumatic headache (PTH) consequent to mild traumatic brain injury (mTBI) is a complex, multidimensional, chronic neurological disorder. The purpose of this review is to evaluate the current neuroimaging studies on mTBI and PTH with a specific focus on brain networks and connectivity patterns.

RECENT FINDINGS

We present findings on PTH incidence and prevalence, as well as the latest neuroimaging research findings on mTBI and PTH. Additionally, we propose a new strategy in studying PTH following mTBI. The diversity and heterogeneity of pathophysiological mechanisms underlying mild traumatic brain injury pose unique challenges on how we interpret neuroimaging findings in PTH. Evaluating alterations in the intrinsic brain network connectivity patterns using novel imaging and analytical techniques may provide additional insights into PTH disease state and therefore inform effective treatment strategies.

Peripheral Blood and Salivary Biomarkers of Blood-Brain Barrier Permeability and Neuronal Damage: Clinical and Applied Concepts

Within the neurovascular unit (NVU), the blood–brain barrier (BBB) operates as a key cerebrovascular interface, dynamically insulating the brain parenchyma from peripheral blood and compartments. Increased BBB permeability is clinically relevant for at least two reasons: it actively participates to the etiology of central nervous system (CNS) diseases, and it enables the diagnosis of neurological disorders based on the detection of CNS molecules in peripheral body fluids. In pathological conditions, a suite of glial, neuronal, and pericyte biomarkers can exit the brain reaching the peripheral blood and, after a process of filtration, may also appear in saliva or urine according to varying temporal trajectories. Here, we specifically examine the evidence in favor of or against the use of protein biomarkers of NVU damage and BBB permeability in traumatic head injury, including sport (sub)concussive impacts, seizure disorders, and neurodegenerative processes such as Alzheimer's disease. We further extend this analysis by focusing on the correlates of human extreme physiology applied to the NVU and its biomarkers. To this end, we report NVU changes after prolonged exercise, freediving, and gravitational stress, focusing on the presence of peripheral biomarkers in these conditions. The development of a biomarker toolkit will enable minimally invasive routines for the assessment of brain health in a broad spectrum of clinical, emergency, and sport settings.

Plasma miR-9-3p and miR-136-3p as Potential Novel Diagnostic Biomarkers for Experimental and Human Mild Traumatic Brain Injury

Noninvasive, affordable circulating biomarkers for difficult-to-diagnose mild traumatic brain injury (mTBI) are an unmet medical need. Although blood microRNA (miRNA) levels are reportedly altered after traumatic brain injury (TBI), their diagnostic potential for mTBI remains inconclusive. We hypothesized that acutely altered plasma miRNAs could serve as diagnostic biomarkers both in the lateral fluid percussion injury (FPI) model and clinical mTBI. We performed plasma small RNA-sequencing from adult male Sprague-Dawley rats (n = 31) at 2 days post-TBI, followed by polymerase chain reaction (PCR)-based validation of selected candidates. miR-9a-3p, miR-136-3p, and miR-434-3p were identified as the most promising candidates at 2 days after lateral FPI. Digital droplet PCR (ddPCR) revealed 4.2-, 2.8-, and 4.6-fold elevations in miR-9a-3p, miR-136-3p, and miR-434-3p levels (p < 0.01 for all), respectively, distinguishing rats with mTBI from naïve rats with 100% sensitivity and specificity. DdPCR further identified a subpopulation of mTBI patients with plasma miR-9-3p (n = 7/15) and miR-136-3p (n = 5/15) levels higher than one standard deviation above the control mean at <2 days postinjury. In sTBI patients, plasma miR-9-3p levels were 6.5- and 9.2-fold in comparison to the mTBI and control groups, respectively. Thus, plasma miR-9-3p and miR-136-3p were identified as promising biomarker candidates for mTBI requiring further evaluation in a larger patient population.

Hypobaria-Induced Oxidative Stress Facilitates Homocysteine Transsulfuration and Promotes Glutathione Oxidation in Rats with Mild Traumatic Brain Injury

Background:

United States service members injured in combat theatre are often aeromedically evacuated within a few days to regional military hospitals. Animal and epidemiological research indicates that early exposure to flight hypobaria may worsen brain and other injuries. The mechanisms by which secondary exposure to hypobaria worsen trauma outcomes are not well elucidated. This study tested the hypothesis that hypobaria-induced oxidative stress and associated changes in homocysteine levels play a role in traumatic brain injury (TBI) pathological progression caused by hypobaria.

Methods:

Male Sprague Dawley rats were exposed to a 6 h hypobaria 24 h after mild TBI by the controlled cortical impact. Plasma and brain tissues were assessed for homocysteine levels, oxidative stress markers or glutathione metabolism, and behavioral deficits post-injury in the absence and presence of hypobaria exposure.

Results:

We found that hypobaria after TBI increased oxidative stress markers, altered homocysteine metabolism, and promoted glutathione oxidation. Increased glutathione metabolism was driven by differential upregulation of glutathione metabolizing genes. These changes correlated with increased anxiety-like behavior.

Conclusion:

These data provide evidence that hypobaria exposure after TBI increases oxidative stress and alters homocysteine elimination likely through enhanced glutathione metabolism. This pathway may represent a compensatory mechanism to attenuate free radical formation. Thus, hypobaria-induced enhancement of glutathione metabolism represents a potential therapeutic target for TBI management.

Potential biomarkers of childhood brain tumor identified by proteomics of cerebrospinal fluid from extraventricular drainage (EVD)

Brain tumors are the most common solid tumors in childhood. There is the need for biomarkers of residual disease, therapy response and recurrence. Cerebrospinal fluid (CSF) is a source of brain tumor biomarkers. We analyzed the proteome of waste CSF from extraventricular drainage (EVD) from 29 children bearing different brain tumors and 17 controls needing EVD insertion for unrelated causes. 1598 and 1526 proteins were identified by liquid chromatography-coupled tandem mass spectrometry proteomics in CSF control and brain tumor patients, respectively, 263 and 191 proteins being exclusive of either condition. Bioinformatic analysis revealed promising protein biomarkers for the discrimination between control and tumor (TATA-binding protein-associated factor 15 and S100 protein B). Moreover, Thymosin beta-4 (TMSB4X) and CD109, and 14.3.3 and HSP90 alpha could discriminate among other brain tumors and low-grade gliomas plus glyoneuronal tumors/pilocytic astrocytoma, or embryonal tumors/medulloblastoma. Biomarkers were validated by ELISA assay. Our method was able to distinguish among brain tumor vs non-tumor/hemorrhagic conditions (controls) and to differentiate two large classes of brain tumors. Further prospective studies may assess whether the biomarkers proposed by our discovery approach can be identified in other bodily fluids, therefore less invasively, and are useful to guide therapy and predict recurrences.

Thorough overview of ubiquitin C-terminal hydrolase-L1 and glial fibrillary acidic protein as tandem biomarkers recently cleared by US Food and Drug Administration for the evaluation of intracranial injuries among patients with traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity affecting all ages. It remains to be a diagnostic and therapeutic challenge, in which, to date, there is no Food and Drug Administration‐approved drug for treating patients suffering from TBI. The heterogeneity of the disease and the associated complex pathophysiology make it difficult to assess the level of the trauma and to predict the clinical outcome. Current injury severity assessment relies primarily on the Glasgow Coma Scale score or through neuroimaging, including magnetic resonance imaging and computed tomography scans. Nevertheless, such approaches have certain limitations when it comes to accuracy and cost efficiency, as well as exposing patients to unnecessary radiation. Consequently, extensive research work has been carried out to improve the diagnostic accuracy of TBI, especially in mild injuries, because they are often difficult to diagnose. The need for accurate and objective diagnostic measures led to the discovery of biomarkers significantly associated with TBI. Among the most well‐characterized biomarkers are ubiquitin C‐terminal hydrolase‐L1 and glial fibrillary acidic protein. The current review presents an overview regarding the structure and function of these distinctive protein biomarkers, along with their clinical significance that led to their approval by the US Food and Drug Administration to evaluate mild TBI in patients.

Calcium-Dependent Translocation of S100B Is Facilitated by Neurocalcin Delta

S100B is a calcium-binding protein that governs calcium-mediated responses in a variety of cells—especially neuronal and glial cells. It is also extensively investigated as a potential biomarker for several disease conditions, especially neurodegenerative ones. In order to establish S100B as a viable pharmaceutical target, it is critical to understand its mechanistic role in signaling pathways and its interacting partners. In this report, we provide evidence to support a calcium-regulated interaction between S100B and the neuronal calcium sensor protein, neurocalcin delta both in vitro and in living cells. Membrane overlay assays were used to test the interaction between purified proteins in vitro and bimolecular fluorescence complementation assays, for interactions in living cells. Added calcium is essential for interaction in vitro; however, in living cells, calcium elevation causes translocation of the NCALD-S100B complex to the membrane-rich, perinuclear trans-Golgi network in COS7 cells, suggesting that the response is independent of specialized structures/molecules found in neuronal/glial cells. Similar results are also observed with hippocalcin, a closely related paralog; however, the interaction appears less robust in vitro. The N-terminal region of NCALD and HPCA appear to be critical for interaction with S100B based on in vitro experiments. The possible physiological significance of this interaction is discussed.

Blood Biomarkers for Detection of Brain Injury in COVID-19 Patients

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus attacks multiple organs of coronavirus disease 2019 (COVID-19) patients, including the brain. There are worldwide descriptions of neurological deficits in COVID-19 patients. Central nervous system (CNS) symptoms can be present early in the course of the disease. As many as 55% of hospitalized COVID-19 patients have been reported to have neurological disturbances three months after infection by SARS-CoV-2. The mutability of the SARS-COV-2 virus and its potential to directly affect the CNS highlight the urgency of developing technology to diagnose, manage, and treat brain injury in COVID-19 patients. The pathobiology of CNS infection by SARS-CoV-2 and the associated neurological sequelae of this infection remain poorly understood. In this review, we outline the rationale for the use of blood biomarkers (BBs) for diagnosis of brain injury in COVID-19 patients, the research needed to incorporate their use into clinical practice, and the improvements in patient management and outcomes that can result. BBs of brain injury could potentially provide tools for detection of brain injury in COVID-19 patients. Elevations of BBs have been reported in cerebrospinal fluid (CSF) and blood of COVID-19 patients. BB proteins have been analyzed in CSF to detect CNS involvement in patients with infectious diseases, including human immunodeficiency virus and tuberculous meningitis. BBs are approved by the U.S. Food and Drug Administration for diagnosis of mild versus moderate traumatic brain injury and have identified brain injury after stroke, cardiac arrest, hypoxia, and epilepsy. BBs, integrated with other diagnostic tools, could enhance understanding of viral mechanisms of brain injury, predict severity of neurological deficits, guide triage of patients and assignment to appropriate medical pathways, and assess efficacy of therapeutic interventions in COVID-19 patients.

The role of bioactive lipids in attenuating the neuroinflammatory cascade in traumatic brain injury

Traumatic brain injury (TBI) is a major cause of morbidity, mortality, and economic burden. Despite this, there are no proven medical therapies in the pharmacologic management of TBI. A better understanding of disease pathophysiology might lead to novel approaches. In one area of increasing interest, bioactive lipids known to attenuate inflammation might serve as an important biomarker and mediator of disease after TBI. In this review, we describe the pathophysiology of inflammation following TBI, the actions of endogenous bioactive lipids in attenuating neuroinflammation, and their possible therapeutic role in the management of TBI. In particular, specialized pro‐resolving lipid mediators (SPMs) of inflammation represent endogenous compounds that might serve as important biomarkers of disease and potential therapeutic targets. We aim to discuss the current literature from animal models of TBI and limited human experiences that suggest that bioactive lipids and SPMs are mechanistically important to TBI recovery, and by doing so, aim to highlight the need for further clinical and translational research. Early investigations of dietary and parenteral supplementation of pro‐resolving bioactive lipids have been promising. Given the high morbidity and mortality that occurs with TBI, novel approaches are needed.

Recent progress in therapeutic drug delivery systems for treatment of traumatic CNS injuries

Most therapeutics for the treatment of traumatic central nervous system injuries, such as traumatic brain injury and spinal cord injury, encounter various obstacles in reaching the target tissue and exerting pharmacological effects, including physiological barriers like the blood-brain barrier and blood-spinal cord barrier, instability rapid elimination from the injured tissue or cerebrospinal fluid and off-target toxicity. For central nervous system delivery, nano- and microdrug delivery systems are regarded as the most suitable and promising carriers. In this review, the pathophysiology and biomarkers of traumatic central nervous system injuries (traumatic brain injury and spinal cord injury) are introduced. Furthermore, various drug delivery systems, novel combinatorial therapies and advanced therapies for the treatment of traumatic brain injury and spinal cord injury are emphasized.

Clinical Applications of Extracellular Vesicles in the Diagnosis and Treatment of Traumatic Brain Injury

Extracellular vesicles (EVs) have emerged as key mediators of cell-cell communication during homeostasis and in pathology. Central nervous system (CNS)-derived EVs contain cell type-specific surface markers and intralumenal protein, RNA, DNA, and metabolite cargo that can be used to assess the biochemical and molecular state of neurons and glia during neurological injury and disease. The development of EV isolation strategies coupled with analysis of multi-plexed biomarker and clinical data have the potential to improve our ability to classify and treat traumatic brain injury (TBI) and resulting sequelae. Additionally, their ability to cross the blood-brain barrier (BBB) has implications for both EV-based diagnostic strategies and for potential EV-based therapeutics. In the present review, we discuss encouraging data for EV-based diagnostic, prognostic, and therapeutic strategies in the context of TBI monitoring and management.

Blood-based biomarkers for prediction of intracranial hemorrhage and outcome in patients with moderate or severe traumatic brain injury

BACKGROUND

Early identification of traumatic intracranial hemorrhage (ICH) has implications for triage and intervention. Blood-based biomarkers were recently approved by the Food and Drug Administration (FDA) for prediction of ICH in patients with mild traumatic brain injury (TBI). We sought to determine if biomarkers measured early after injury improve prediction of mortality and clinical/radiologic outcomes compared with Glasgow Coma Scale (GCS) alone in patients with moderate or severe TBI (MS-TBI).

METHODS

We measured glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase L1 (UCH-L1), and microtubule-associated protein-2 (MAP-2) on arrival to the emergency department (ED) in patients with blunt TBI enrolled in the placebo arm of the Prehospital TXA for TBI Trial (prehospital GCS score, 3-12; SPB, > 90). Biomarkers were modeled individually and together with prehospital predictor variables [PH] (GCS score, age, sex). Data were divided into a training data set and test data set for model derivation and evaluation. Models were evaluated for prediction of ICH, mass lesion, 48-hour and 28-day mortality, and 6-month Glasgow Outcome Scale-Extended (GOS-E) and Disability Rating Scale (DRS). Area under the curve (AUC) was evaluated in test data for PH alone, PH + individual biomarkers, and PH + three biomarkers.

RESULTS

Of 243 patients with baseline samples (obtained a median of 84 minutes after injury), prehospital GCS score was 8 (interquartile range, 5-10), 55% had ICH, and 48-hour and 28-day mortality were 7% and 13%, respectively. Poor neurologic outcome at 6 months was observed in 34% based on GOS-E of 4 or less, and 24% based on DRS greater than or equal to7. Addition of each biomarker to PH improved AUC in the majority of predictive models. GFAP+PH compared with PH alone significantly improved AUC in all models (ICH, 0.82 vs. 0.64; 48-hour mortality, 0.84 vs. 0.71; 28-day mortality, 0.84 vs. 0.66; GOS-E, 0.78 vs. 0.69; DRS, 0.84 vs. 0.81, all p < 0.001).

CONCLUSION

Circulating blood-based biomarkers may improve prediction of neurological outcomes and mortality in patients with MS-TBI over prehospital characteristics alone. Glial fibrillary acidic protein appears to be the most promising. Future evaluation in the prehospital setting is warranted.

LEVEL OF EVIDENCE

Prospective, Prognostic and Epidemiological, level II.

A Decade of mTBI Experience: What Have We Learned? A Summary of Proceedings From a NATO Lecture Series on Military mTBI

Mild traumatic brain injury (mTBI, also known as a concussion) as a consequence of battlefield blast exposure or blunt force trauma has been of increasing concern to militaries during recent conflicts. This concern is due to the frequency of exposure to improvised explosive devices for forces engaged in operations both in Iraq and Afghanistan coupled with the recognition that mTBI may go unreported or undetected. Blasts can lead to mTBI through a variety of mechanisms. Debate continues as to whether exposure to a primary blast wave alone is sufficient to create brain injury in humans, and if so, exactly how this occurs with an intact skull. Resources dedicated to research in this area have also varied substantially among contributing NATO countries. Most of the research has been conducted in the US, focused on addressing uncertainties in management practices. Development of objective diagnostic tests should be a top priority to facilitate both diagnosis and prognosis, thereby improving management. It is expected that blast exposure and blunt force trauma to the head will continue to be a potential source of injury during future conflicts. An improved understanding of the effects of blast exposure will better enable military medical providers to manage mTBI cases and develop optimal protective measures. Without the immediate pressures that come with a high operational tempo, the time is right to look back at lessons learned, make full use of available data, and modify mitigation strategies with both available evidence and new evidence as it comes to light. Toward that end, leveraging our cooperation with the civilian medical community is critical because the military experience over the past 10 years has led to a renewed interest in many similar issues pertaining to mTBI in the civilian world. Such cross-fertilization of knowledge will undoubtedly benefit all. This paper highlights similarities and differences in approach to mTBI patient care in NATO and partner countries and provides a summary of and lessons learned from a NATO lecture series on the topic of mTBI, demonstrating utility of having patients present their experiences to a medical audience, linking practical clinical care to policy approaches.

Predicting Neurological Recovery after Traumatic Brain Injury in Children: A Systematic Review of Prognostic Models

Predictive modeling is foundational to treatment and long-term management of children with traumatic brain injury (TBI). Assessment of injury severity in the acute-care setting enables early stratification of patients based on their risk of death, lifelong disability, or unfavorable outcome. This review evaluates predictive models that have been developed or validated for pediatric TBI patients. The predictive accuracy of these models, the outcomes and time points predicted, and the variables and statistical methods utilized in model development were compared. Embase, Scopus, MEDLINE^®, and Web of Science were searched for studies that developed statistical models for predicting patient outcomes following pediatric TBI. Studies were excluded if they focused on adults or non-traumatic brain injury, or if they did not assess classification accuracy. A total of 4538 entries were identified and screened, with 7 studies included for analysis. This included five studies in which adult predictive models were validated for use in the pediatric setting, and two in which new models were derived from a pediatric cohort. Trials of adult prediction tools in pediatric cohorts, including the International Mission for Prognosis and Analysis of Clinical Trials in TBI (IMPACT) and Corticoid Randomisation After Significant Head Injury (CRASH)-TBI models, showed comparable accuracy between classification of adults and children. Models derived from pediatric cohorts showed improved accuracy. Most studies solely focused on clinical variables, with two studies incorporating biochemical and imaging variables. Predictive models for pediatric TBI are primarily based on methods and variables identified in adult studies. Although adult models have proven effective in select pediatric cohorts, they may be suboptimal when compared with models derived or adjusted for children.