Systematic Review of Serum Biomarkers in Traumatic Brain Injury

Blood-Based Protein Biomarkers in the Chronic Phase of Traumatic Brain Injury: A Systematic Review

There has been limited exploration of blood-based biomarkers in the chronic period following traumatic brain injury (TBI). Our objective was to conduct a systematic review of studies examining blood-based protein biomarkers with at least one sample collected 12 months post-TBI in adults (≥16 years). Database searches were conducted in Embase, MEDLINE, and Science Citation Index-Expanded on July 24, 2023. Risk of bias was assessed using modified Joanna Briggs Institute critical appraisal tools. Only 30 of 12,523 articles met inclusion criteria, with samples drawn from 12 months to 48 years. Higher quality evidence (low risk of bias; large samples) identified promising inflammatory biomarkers at 12 months post-injury in both moderate-severe TBI (GFAP) and mild TBI (eotaxin-1, IFN-y, IL-8, IL-9, IL-17A, MCP-1, MIP-1β, FGF-basic, and TNF-α). Studies with low risk of bias but smaller samples also suggest NSE, MME, and CRP may be informative, alongside protein variants for α-syn (10H, D5), amyloid-β (A4, C6T), TDP-43 (AD-TDP 1;2;3;9;11), and tau (D11C). Findings for NfL were inconclusive. Longitudinal data were mostly available for acute samples followed until 12 months post-injury, with limited evaluation of changes beyond 12 months. Associations of some blood-based biomarkers with cognitive, sleep, and functional outcomes were reported. The overall strength of the evidence in this review was limited by the risk of bias and small sample sizes. Replication is required within prospective longitudinal studies that move beyond 12 months post-injury. Novel efforts should be guided by promising neurodegenerative-disease markers and use panels to model polypathology.

Postmortem biochemistry of GFAP, NSE and S100B in cerebrospinal fluid and in vitreous humor for estimation of postmortem interval: a pilot study

Postmortem interval (PMI) is a challenging issue in forensic practice. Although postmortem biomarkers of traumatic brain injury (TBI) are recognised as an emerging resource for PMI estimation, their role remains controversial. This study aims to evaluate postmortem concentrations of three TBI biomarkers (GFAP, NSE and S100B) in two matrices (cerebrospinal fluid and vitreous humor), in order to find out if these markers could be adopted in PMI estimation. Thirty-five deceased individuals with known PMI who underwent forensic autopsy at the University of Parma were examined. Matrices were collected during autopsy, then biomarker concentrations were determined through the enzyme-linked immunosorbent assay. Statistical significance of the data in relation to PMI was studied. The correlation of biomarkers with PMI, examined with samples divided into six groups according to the number of days elapsed since death, was not statistically significant, although S100B in cerebrospinal fluid showed an increasing trend in cases from 1 to 5 days of PMI. Comparison between cases with 1 day of PMI and those with 2 or more days of PMI showed a statistically significant correlation for GFAP and NSE in cerebrospinal fluid. GFAP and NSE in cerebrospinal fluid represent appropriate biomarkers in PMI estimation to distinguish cases with one day of PMI from those with two or more days of PMI. The current study was limited by the scarcity of the cohort and the narrow spectrum of cases. Further research is needed to confirm these observations.

Multimodal evaluation of the effects of low-intensity ultrasound on cerebral blood flow after traumatic brain injury in mice

Traumatic brain injury (TBI) is one of the leading causes of death and disability worldwide, and destruction of the cerebrovascular system is a major factor in the cascade of secondary injuries caused by TBI. Laser speckle imaging (LSCI)has high sensitivity in detecting cerebral blood flow. LSCI can visually show that transcranial focused ultrasound stimulation (tFUS) treatment stimulates angiogenesis and increases blood flow. To study the effect of tFUS on promoting angiogenesis in Controlled Cortical impact (CCI) model. tFUS was administered daily for 10 min and for 14 consecutive days after TBI. Cerebral blood flow was measured by LSCI at 1, 3, 7 and 14 days after trauma. Functional outcomes were assessed using LSCI and neurological severity score (NSS). After the last test, Nissl staining and vascular endothelial growth factor (VEGF) were used to assess neuropathology. TBI can cause the destruction of cerebrovascular system. Blood flow was significantly increased in TBI treated with tFUS. LSCI, behavioral and histological findings suggest that tFUS treatment can promote angiogenesis after TBI.

Identification of patients at high risk for brain death using an automated digital screening tool: a prospective diagnostic accuracy study

BACKGROUND

An automated digital screening tool (DETECT) has been developed to aid in the early identification of patients who are at risk of developing brain death during critical care.

METHODS

This prospective diagnostic accuracy study included consecutive patients ≥ 18 years admitted to neurocritical care for primary or secondary acute brain injury. The DETECT screening tool searched routinely monitored patient data in the electronic medical records every 12 h for a combination of coma and absence of bilateral pupillary light reflexes. In parallel, daily neurological assessment was performed by expert neurointensivists in all patients blinded to the index test results. The primary target condition was the eventual diagnosis of brain death. Estimates of diagnostic accuracy along with their 95%-confidence intervals were calculated to assess the screening performance of DETECT.

RESULTS

During the 12-month study period, 414 patients underwent neurological assessment, with 8 (1.9%) confirmed cases of brain death. DETECT identified 54 positive patients and sent 281 notifications including 227 repeat notifications. The screening tool had a sensitivity of 100% (95% CI 63.1-100%) in identifying patients who eventually developed brain death, with no false negatives. The mean time from notification to confirmed diagnosis of brain death was 3.6 ± 3.2 days. Specificity was 88.7% (95% CI 85.2-91.6%), with 46 false positives. The overall accuracy of DETECT for confirmed brain death was 88.9% (95% CI 85.5-91.8%).

CONCLUSIONS

Our findings suggest that an automated digital screening tool that utilizes routinely monitored clinical data may aid in the early identification of patients at risk of developing brain death.

Inflammation biomarkers IL‑6 and IL‑10 may improve the diagnostic and prognostic accuracy of currently authorized traumatic brain injury tools

Traumatic brain injury (TBI) is currently one of the leading causes of mortality and disability worldwide. At present, no reliable inflammatory or specific molecular neurobiomarker exists in any of the standard models proposed for TBI classification or prognostication. Therefore, the present study was designed to assess the value of a group of inflammatory mediators for evaluating acute TBI, in combination with clinical, laboratory and radiological indices and prognostic clinical scales. In the present single-centre, prospective observational study, 109 adult patients with TBI, 20 adult healthy controls and a pilot group of 17 paediatric patients with TBI from a Neurosurgical Department and two intensive care units of University General Hospital of Heraklion, Greece were recruited. Blood measurements using the ELISA method, of cytokines IL-6, IL-8 and IL-10, ubiquitin C-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein, were performed. Compared with those in healthy control individuals, elevated IL-6 and IL-10 but reduced levels of IL-8 were found on day 1 in adult patients with TBI. In terms of TBI severity classifications, higher levels of IL-6 (P=0.001) and IL-10 (P=0.009) on day 1 in the adult group were found to be associated with more severe TBI according to widely used clinical and functional scales. Moreover, elevated IL-6 and IL-10 in adults were found to be associated with more serious brain imaging findings (rs<0.442; P<0.007). Subsequent multivariate logistic regression analysis in adults revealed that early-measured (day 1) IL-6 [odds ratio (OR)=0.987; P=0.025] and UCH-L1 (OR=0.993; P=0.032) are significant independent predictors of an unfavourable outcome. In conclusion, results from the present study suggest that inflammatory molecular biomarkers may prove to be valuable diagnostic and prognostic tools for TBI.

Platelet levels and age are determinants of survival after mild-moderate TBI: A prospective study in Spain

Introduction

Traumatic brain injury (TBI) is a very important reason for consultation in emergency departments.

Methods

A hospital cohort study with patients who attended a hospital emergency department between June 1, 2018 and December 31, 2020 due to TBI was studied. Clinical and sociodemographic variables were recorded. The levels of biomarkers and management variables were used. Qualitative variables were analyzed using Pearson's chi-square test, and quantitative variables using the Mann-Whitney U-test. Survival analyses were performed by fitting a multivariable Cox regression model for patient survival during the follow-up of the study in relation to the patient's characteristics upon admission to the emergency department.

Results

A total of 540 patients were included. The mean age was 83 years, and 53.9% of the patients were men. Overall, 112 patients (20.7%) died during the study follow-up. The mortality rate per 100 person-years was 14.33 (11.8-17.24), the most frequent mechanism being falls in the home, with none caused on public roads. The multivariable Cox proportional hazards model showed that survival after TBI was significantly associated with age, S100 levels, Charlson index, patient's institutionalized status, the place where the TBI occurred, and hemoglobin and platelet levels.

Discussion

The most common profile for a patient with a TBI was male and aged between 80 and 90 years. The combination of the variables age, Charlson index, place of TBI occurrence, and hemoglobin and platelet levels could offer early prediction of survival in our population independently of TBI severity. With the data obtained, a therapeutic algorithm could be established for patients suffering from mild TBI, allowing the patient to be supervised at home, avoiding futile referrals to emergency services.

Plasma Neurofilament Light Chain (NF-L) Is a Prognostic Biomarker for Cortical Damage Evolution but Not for Cognitive Impairment or Epileptogenesis Following Experimental TBI

Plasma neurofilament light chain (NF-L) levels were assessed as a diagnostic biomarker for traumatic brain injury (TBI) and as a prognostic biomarker for somatomotor recovery, cognitive decline, and epileptogenesis. Rats with severe TBI induced by lateral fluid-percussion injury (n = 26, 13 with and 13 without epilepsy) or sham-operation (n = 8) were studied. During a 6-month follow-up, rats underwent magnetic resonance imaging (MRI) (day (D) 2, D7, and D21), composite neuroscore (D2, D6, and D14), Morris-water maze (D35−D39), and a 1-month-long video-electroencephalogram to detect unprovoked seizures during the 6th month. Plasma NF-L levels were assessed using a single-molecule assay at baseline (i.e., naïve animals) and on D2, D9, and D178 after TBI or a sham operation. Plasma NF-L levels were 483-fold higher on D2 (5072.0 ± 2007.0 pg/mL), 89-fold higher on D9 (930.3 ± 306.4 pg/mL), and 3-fold higher on D176 32.2 ± 8.9 pg/mL after TBI compared with baseline (10.5 ± 2.6 pg/mL; all p < 0.001). Plasma NF-L levels distinguished TBI rats from naïve animals at all time-points examined (area under the curve [AUC] 1.0, p < 0.001), and from sham-operated controls on D2 (AUC 1.0, p < 0.001). Plasma NF-L increases on D2 were associated with somatomotor impairment severity (ρ = −0.480, p < 0.05) and the cortical lesion extent in MRI (ρ = 0.401, p < 0.05). Plasma NF-L increases on D2 or D9 were associated with the cortical lesion extent in histologic sections at 6 months post-injury (ρ = 0.437 for D2; ρ = 0.393 for D9, p < 0.05). Plasma NF-L levels, however, did not predict somatomotor recovery, cognitive decline, or epileptogenesis (p > 0.05). Plasma NF-L levels represent a promising noninvasive translational diagnostic biomarker for acute TBI and a prognostic biomarker for post-injury somatomotor impairment and long-term structural brain damage.

Risk Factors for High Symptom Burden Three Months after Traumatic Brain Injury and Implications for Clinical Trial Design: A Transforming Research and Clinical Knowledge in Traumatic Brain Injury Study

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 Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study, we examined the relationship of 3-month symptoms to pre-injury, demographic, and acute characteristics as well as 2-week symptoms and blood-based biomarkers to identify and evaluate factors that may be used for sample enrichment for clinical trials. Many of the risk factors for TBI symptoms reported in the literature were supported, but the effect sizes of each were small or moderate (< 0.5). The only factors with large effect sizes when predicting 3-month symptom burden were TBI-related (i.e., post-concussive) and post-traumatic stress symptom levels at 2 weeks (respective effect sizes 1.13 and 1.34). TBI severity was not significantly associated with 3-month symptom burden (p = 0.37). Using simulated data to evaluate the effect of enrichment, we showed that including only people with high symptom burden at 2 weeks would permit trials to reduce the sample size by half, with minimal increase in screening, as compared with enrolling an unenriched sample. Clinical trials aimed at reducing symptoms after TBI can be efficiently conducted by enriching the included sample with people reporting a high early symptom burden.

The prognostic significance of biomarkers in cerebrospinal fluid following severe traumatic brain injury: a systematic review and meta-analysis

After severe traumatic brain injury (sTBI) proteins, neurotrophic factors and inflammatory markers are released into the biofluids. This review and meta-analysis searched the literature for prognostic candidate cerebrospinal fluid markers and their relation to sTBI patient outcome. A systematic search of the literature was carried out across PubMed, EMBASE, PubMed Central (PMC), and Cochrane Central Library. Biomarker concentrations were related to the Glasgow Outcome Scale dichotomized into favorable and unfavorable outcomes. When a biomarker was reported in ≥ 3 studies, it was included in meta-analysis. The search returned 1527 articles. After full-text analysis, 54 articles were included, 34 from the search, and 20 from the reference lists. Of 9 biomarkers, 8 were significantly different compared to controls (IL-4, IL-6, IL-8, IL-10, TNFα, sFas, BDNF, and cortisol). Of these, 5 were significantly increased in sTBI patients with unfavorable outcome (IL-6, IL-8, IL-10, TNFα, and cortisol), compared to patients with favorable outcome. This review demonstrated a correlation between 5 biomarkers and clinical outcome in sTBI patients. The paucity of included studies, however, makes it difficult to extrapolate further on this finding.