Systemic, local, and imaging biomarkers of brain injury: more needed, and better use of those already established?

Advanced perioperative assessment of neurological function in acute Stanford A aortic dissection

OBJECTIVE

Acute Stanford Type A aortic dissection (AAAD) is a critical condition in vascular surgery, and total aortic arch replacement surgery is the preferred method to save patients' lives. In recent years, as clinical research has advanced, there has been a growing realization of the close association between poor postoperative outcomes in patients and neurological functional deficits. Neurological function monitoring is a medical technique used to evaluate and monitor the functional status of the nervous system.

METHODS

This monitoring involves the assessment of various aspects of the nervous system, including but not limited to nerve conduction velocity, neuromuscular function, electroencephalographic activity, and sensory nerve transmission. Neurological function monitoring has broad clinical applications and can be used to diagnose and monitor many neurological disorders, helping physicians understand patients' neurological functional status and guide treatment plans. During the postoperative recovery process, neurological function monitoring can assist physicians in assessing the potential impact of surgery on the nervous system and monitor the recovery of patients' neurological function.

RESULTS

Studies have shown that neurological function monitoring holds promise in predicting neurological functional prognosis and interventions for patients with aortic dissection.

CONCLUSION

Therefore, the primary objective of this study is to evaluate the effectiveness and reliability of various intraoperative neurological monitoring techniques, neuroimaging examinations, and biomarkers in predicting and assessing postoperative neurological outcomes in patients undergoing AAAD surgery.

Post-mortem detection of neuronal and astroglial biochemical markers in serum and urine for diagnostics of traumatic brain injury

Currently available epidemiological data shows that traumatic brain injury (TBI) represents one of the leading causes of death that is associated with medico-legal practice, including forensic autopsy, criminological investigation, and neuropathological examination. Attention focused on TBI research is needed to advance its diagnostics in ante- and post-mortem cases with regard to identification and validation of novel biomarkers. Recently, several markers of neuronal, astroglial, and axonal injury have been explored in various biofluids to assess the clinical origin, progression, severity, and prognosis of TBI. Despite clinical usefulness, understanding their diagnostic accuracy could also potentially help translate them either into forensic or medico-legal practice, or both. The aim of this study was to evaluate post-mortem pro-BDNF, NSE, UCHL1, GFAP, S100B, SPTAN1, NFL, MAPT, and MBP levels in serum and urine in TBI cases. The study was performed using cases (n = 40) of fatal head injury and control cases (n = 20) of sudden death. Serum and urine were collected within ∼ 24 h after death and compared using ELISA test. In our study, we observed the elevated concentration levels of GFAP and MAPT in both serum and urine, elevated concentration levels of S100B and SPTAN1 in serum, and decreased concentration levels of pro-BDNF in serum compared to the control group. The obtained results anticipate the possible implementation of performed assays as an interesting tool for forensic and medico-legal investigations regarding TBI diagnosis where the head injury was not supposed to be the direct cause of death.

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

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

Microcirculatory Biomarkers of Secondary Cerebral Ischemia in Traumatic Brain Injury

AIM

The purpose of this study was to study changes in cerebral microcirculation parameters in the development of secondary cerebral ischemia (SCI).

METHODS

A total of 202 patients with a Glasgow Coma Scale score ≤ 12 after experiencing a traumatic brain injury (TBI) were recruited for the study within 6 h of the injury. All patients were subjected to perfusion computed tomography. The cerebral blood flow velocity was recorded using transcranial Doppler ultrasound. The arterial blood pressure was measured noninvasively. The cerebrovascular resistance (CVR), cerebral arterial compliance (CAC), cerebrovascular time constant (CTC), and critical closing pressure (CCP) were measured using the neuromonitoring complex. All patients had unilateral foci of posttraumatic ischemia. Statistical analysis was performed using a paired Student's t test and factor analysis.

RESULTS AND CONCLUSION

The CVR and CCP were significantly increased in patients who developed SCI after TBI, whereas the CAC and CTC were significantly decreased (P < 0.05). Factor analyses revealed that the CVR, CAC, and CTC were significantly associated with development of posttraumatic ischemia (P < 0.05). The changes in the CVR and CCP in patients with TBI were significantly associated with SCI development (P < 0.05).

Can admission lipoprotein-associated phospholipase A2 predict the symptomatic cerebral vasospasm following aneurysmal subarachnoid hemorrhage?

Background

Inflammation has been believed to be related to the development of cerebral vasospasm following aneurysmal subarachnoid hemorrhage (aSAH). A potential biomarker for vascular inflammation that is well recognized is the lipoprotein-associated phospholipase A2 (Lp-PLA2). However, whether Lp-PLA2 can predict the occurrence of symptomatic cerebral vasospasm (SCV) in aSAH patients is still unknown. Thus, this study aimed to assess the value of Lp-PLA2 for predicting SCV in patients with aSAH.

Methods

Between March 2017 and April 2018, we evaluated 128 consecutive aSAH patients who were admitted in the First Affiliated Hospital of Fujian Medical University. Their Lp-PLA2 level was obtained within 24 h of the initial bleeding. Factors might be related to SCV were analyzed.

Results

Compared to patients without SCV, those with SCV (9.4%, 12/128) had significantly higher Lp-PLA2 level. Multivariate logistic analysis revealed that worse modified Fisher grade (OR = 10.08, 95% CI = 2.04-49.86, P = 0.005) and higher Lp-PLA2 level (OR = 6.66, 95% CI = 1.33-3.30, P = 0.021) were significantly associated with SCV, even after adjustment for confounders. Based on the best threshold, Lp-PLA2 had a sensitivity of 83.3% and a specificity of 51.7% for predicting SCV, as shown by the receiver operating characteristic curve analysis. In the poor World Federation of Neurosurgical Societies grade patient sub-group, patients with Lp-PLA2 > 200 μg/L had significantly higher SCV rate than that of patients having Lp-PLA2 ≤ 200 μg/L.

Conclusion

The admission Lp-PLA2 level might be a helpful predictor for SCV in aSAH.

Inducing Brain Cooling Without Core Temperature Reduction in Pigs Using a Novel Nasopharyngeal Method: An Effectiveness and Safety Study

BACKGROUND

Acute brain lesions constitute an alarming public health concern. Neuroprotective therapies have been implemented to stabilize, prevent, or reduce brain lesions, thus improving neurological outcomes and survival rates. Hypothermia is the most effective approach, mainly attributed to the reduction in cellular metabolic activity. Whole-body cooling is currently implemented by healthcare professionals; however, adverse events are frequent, limiting the potential benefits of therapeutic hypothermia. Therefore, selective methods have been developed to reduce adverse events while delivering neuroprotection. Nasopharyngeal approaches are the safest and most effective methods currently considered. Our primary objective was to determine the effects of a novel nasopharyngeal catheter on the brain temperature of pigs.

METHODS

In this prospective, non-randomized, interventional experimental trial, 10 crossbred pigs underwent nasopharyngeal cooling for 60 min followed by 15 min of rewarming. Nasopharyngeal catheters were inserted into the left nostril and properly positioned at the nasopharyngeal cavity.

RESULTS

Nasopharyngeal cooling was associated with a decrease in brain temperature, which was more significant in the left cerebral hemisphere (p = 0.01). There was a reduction of 1.47 ± 0.86 °C in the first 5 min (p < 0.001), 2.45 ± 1.03 °C within 10 min (p < 0.001), and 4.45 ± 1.36 °C after 1 h (p < 0.001). The brain-core gradient was 4.57 ± 0.87 °C (p < 0.001). Rectal, esophageal, and pulmonary artery temperatures and brain and systemic hemodynamic parameters, remained stable during the procedure. Following brain cooling, values of oxygen partial pressure in brain tissue significantly decreased. No mucosal lesions were detected during nasal, pharyngeal, or oral inspection after nasopharyngeal catheter removal.

CONCLUSIONS

In this study, a novel nasopharyngeal cooling catheter effectively induced and maintained exclusive brain cooling when combined with effective counter-warming methods. Exclusive brain cooling was safe with no device-related local or systemic complications and may be desired in selected patient populations.

Early stage neuroglobin level as a predictor of delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage

BACKGROUND

The neuroglobin (Ngb) is well recognized as a potential biomarker for the hypoxic-ischemic brain injury. However, connection between Ngb and delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH) is still unclear.

OBJECTIVE

To investigate the relationship between early stage Ngb level of aSAH patient and the occurrence of DCI.

METHODS

We evaluated 126 aSAH patients who were enrolled into a prospective observational cohort study. Serum Ngb level on days 1, 2, 3, 5, and 7 after aSAH were determined using a commercial enzyme-linked immunosorbent assay kit. The relationship between Ngb level and DCI was analyzed.

RESULTS

Forty-six (36.5%) aSAH patients experienced DCI. Patients with DCI had significantly higher Ngb levels than those without (p < .001). Multivariate model analysis revealed that day 3 Ngb level remained a significant factor after adjusting for World Federation of Neurosurgical Societies (WFNS) grade, modified Fisher grade, clipping and Ngb levels on days 1, 2, 5, and 7. Sensitivity, specificity, and Youden index of day 3 Ngb level for identifying DCI were derived as 73.9%, 72.5%, and 0.46, respectively, based on the best threshold of 8.4 ng/ml. Regardless in good-grade group or in poor-grade group, patients having day 3 Ngb level > 8.4 ng/ml has a significantly worse DCI survival rate than those having day 3 Ngb level <=8.4 ng/ml (p = .026 and .009, respectively).

CONCLUSIONS

Serum Ngb level was significantly elevated in DCI patients. Early stage aSAH Ngb level has the potential of being used as a novel DCI occurrence predictor, especially when Ngb level was combined with WFNS grade.

Blast traumatic brain injury and serum inflammatory cytokines: a repeated measures case-control study among U.S. military service members

Background

There is a paucity of human data on exposure to blast traumatic brain injury (bTBI) and the corresponding systemic cytokine immune response at later time points (i.e., months, years) post-injury.

Methods

We conducted a repeated measures, case-control study, examining associations of serum levels of pro- and anti-inflammatory cytokines, measured both pre- and post-deployment with having mild and moderate/severe bTBI. Utilizing serum from the Department of Defense Serum Repository cytokines were measured via an ELISA-based array for 15 cytokines. We compared pre- vs. post-levels among mild cases, moderate/severe cases, and controls and carried out case-control comparisons, using paired t- tests and generalized linear models.

Results

The average time between bTBI and post-deployment/bTBI serum among cases was 315.8 days. From pre- to post-deployment/bTBI, levels of interleukin 8 (IL-8) were decreased among both mild cases (μ = − 83.43 pg/ml; s.e. = 21.66) and moderate/severe cases (μ = − 107.67 pg/ml; s.e. = 28.74 pg/ml), while levels increased among controls (μ = 32.86 pg/ml; s.e. = 30.29). The same pattern occurred for matrix metallopeptidase 3 (MMP3), with levels decreasing for moderate/severe cases (μ = − 3369.24 pg/ml; s.e. = 1701.68) and increasing for controls (μ = 1859.60 pg/ml; s.e. = 1737.51) from pre- to post-deployment/bTBI. Evidence was also suggestive of case-control differences, from pre- to post-deployment/bTBI for interleukin 1 alpha (IL-1α), interleukin 4 (IL-4), and interleukin 6 (IL-6) among moderate/severe cases.

Conclusion

The findings of this longitudinal study indicate that in the chronic phase of bTBI, levels of IL-8 and MMP3 may be substantially lower than pre-injury. These results need confirmation in other studies, potentially those that account for treatment differences, which was not possible in our study.

Magnetic Resonance Imaging in Aneurysmal Subarachnoid Hemorrhage: Current Evidence and Future Directions

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with an unacceptably high mortality and chronic disability in survivors, underscoring a need to validate new approaches for treatment and prognosis. The use of advanced imaging, magnetic resonance imaging (MRI) in particular, could help address this gap given its versatile capacity to quantitatively evaluate and map changes in brain anatomy, physiology and functional activation. Yet there is uncertainty about the real value of brain MRI in the clinical setting of aSAH.

METHODS

In this review, we discuss current and emerging MRI research in aSAH. PubMed was searched from inception to June 2017, and additional studies were then chosen on the basis of relevance to the topics covered in this review.

RESULTS

Available studies suggest that brain MRI is a feasible, safe, and valuable testing modality. MRI detects brain abnormalities associated with neurologic examination, outcomes, and aneurysm treatment and thus has the potential to increase knowledge of aSAH pathophysiology as well as to guide management and outcome prediction. Newer pulse sequences have the potential to reveal structural and physiological changes that could also improve management of aSAH.

CONCLUSION

Research is needed to confirm the value of MRI-based biomarkers in clinical practice and as endpoints in clinical trials, with the goal of improving outcome for patients with aSAH.

Osteopontin in the Cerebrospinal Fluid of Patients with Severe Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is associated with high morbidity and mortality. In SAH patients, plasma osteopontin (OPN) has been shown to independently predict poor outcome. The aim of the study is to investigate, in a selected population with severe SAH, OPN time course in cerebrospinal fluid (CSF) and plasma during the first week after aneurism rupture, and OPN prognostic value. We included 44 patients with the following criteria: (1) age 18 and 80 years, (2) diagnosis of SAH from cerebral aneurysm rupture, (3) insertion of external ventricular drain. Plasma and CSF were sampled at day 1, 4, and 8. OPN levels, in CSF and plasma, displayed a weak correlation on day 1 and were higher, in CSF, in all time points. Only in poor prognosis patients, OPN levels in CSF significantly increased at day 4 and day 8. Plasma OPN at day 1 and 4 was predictor of poor outcome. In conclusion, plasma and CSF OPN displays a weak correlation, on day 1. The higher levels of OPN found in the CSF compared to plasma, suggest OPN production within the CNS after SAH. Furthermore, plasma OPN, at day 1 and 4, seems to be an independent predictor of poor outcome.

Blood and cerebrospinal fluid biomarkers

Sports-related traumatic brain injuries (TBIs) range in severity from severe to subconcussive. Although technologies exist for clinical diagnosis of more severe injuries, methods for diagnosis of milder forms of brain injury are limited. Developing objective measures to indicate pathogenic processes after a suspected mild TBI is challenging for multiple reasons. The field of biomarker discovery for diagnosing TBI continues to expand, with newly identified candidate biomarkers being reported regularly. Brain-specific biomarkers include proteins derived from neurons and glia, and are often measured to assess neural injury and repair, and to predict outcomes. Ideally, changes in biomarker levels should indicate pathologic events and answer critical questions for accurate diagnosis and prognosis. For example, does the presence or a change in the biomarker level suggest greater vulnerability for sustaining a second concussion or show that the window of increased vulnerability has passed? Likewise, do changes in biomarker levels predict postconcussion syndrome or recovery/repair? Although there are numerous promising candidates for fluid biomarkers that may diagnose mild TBI or concussion, none has reached the clinic to date. In this chapter, we will define biomarkers, discuss the importance of understanding their normal and pathologic functions, and outline some considerations for interpreting detection assay results in TBI. We will then review five proposed blood and cerebrospinal fluid biomarkers (tau, neurofilament, ubiquitin carboxyl-terminal hydrolase L1, S100β, and glial fibrillary acidic protein) used currently to address TBI. Lastly, we will discuss a future trajectory for developing new, clinically useful fluid biomarkers.

Is Admission Lipoprotein-Associated Phospholipase A2 a Novel Predictor of Vasospasm and Outcome in Patients With Aneurysmal Subarachnoid Hemorrhage?

BACKGROUND

The relationships between lipoprotein-associated phospholipase A2 (Lp-PLA2) level, vasospasm, and clinical outcome of patients with aneurysmal subarachnoid hemorrhage (aSAH) are still unclear.

OBJECTIVE

To identify the associations between admission Lp-PLA2 and vasospasm following subarachnoid hemorrhage and the clinical outcome of aSAH.

METHODS

A total of 103 aSAH patients who had Lp-PLA2 level obtained within 24 h postbleeding were included. The relationships between Lp-PLA2 level, vasospasm, and clinical outcome were analyzed.

RESULTS

Vasospasm was observed in 52 patients (50.49%). Patients with vasospasm had significantly higher Lp-PLA2 level than those without (P &lt; .001). Both modified Fisher grade (P = .014) and Lp-PLA2 level (P &lt; .001) were significant predictors associated with vasospasm. The Z test revealed that power of Lp-PLA2 was significantly higher than that of modified Fisher grade in predicting vasospasm (Z = 2.499, P = .012). At 6-mo follow-up, 44 patients (42.72%) had unfavorable outcome and 36 patients (34.95%) died. The World Federation of Neurosurgical Societies (WFNS) grade and Lp-PLA2 level were both significant predictors associated with 6-mo unfavorable outcome and mortality (all P &lt; .001). The predictive values of Lp-PLA2 for unfavorable outcome and mortality at 6-mo tended to be lower than those of the WFNS grade, but the differences were not statistically significant (P = .366 and 0.115, respectively). Poor-grade patients having Lp-PLA2 &gt; 200 μg/L had significantly worse 6-mo survival rate than poor-grade patients having Lp-PLA2 ≤ 200 μg/L (P = .001).

CONCLUSION

The Lp-PLA2 might be useful as a novel predictor in aSAH patients. A total of 30 poor-grade patients; those with elevated Lp-PLA2 level have higher risk of 6-mo mortality compared to those without.

Assessment of lipoprotein-associated phospholipase A2 level and its changes in the early stages as predictors of delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

The relationship between lipoprotein-associated phospholipase A2 (Lp-PLA2) and various cardiovascular and cerebrovascular diseases is inconsistent. However, the connection between Lp-PLA2 level and delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH) remains unclear. The objective of this study was to investigate the relationships between the Lp-PLA2 levels in the early stages of aSAH and the occurrence of DCI.

METHODS

The authors evaluated 114 patients with aSAH who were enrolled into a prospective observational cohort study. Serum Lp-PLA2 level at admission (D0), on the first morning (D1), and on the second morning of hospitalization (D2) were determined using commercial enzyme-linked immunosorbent assay kits. The relationship between Lp-PLA2 levels and DCI was analyzed.

RESULTS

Forty-three patients with aSAH (37.72%) experienced DCI. Mean serum Lp-PLA2 level decreased from 183.06 ± 61.36 μg/L at D0 (D0 vs D1, p = 0.303), to 175.32 ± 51.49 μg/L at D1 and 167.24 ± 54.10 μg/L at D2 (D0 vs D2, p = 0.040). The Lp-PLA2 level changes (D0-D1 and D0-D2) were comparable between patients with and without DCI. Multivariate model analysis revealed Lp-PLA2 level (D0) > 200 μg/L was a more significant factor of DCI compared with Lp-PLA2 (D1) and Lp-PLA2 (D2), and was a strong predictor of DCI (odds ratio [OR] 6.24, 95% confidence interval [CI] 2.05-18.94, p = 0.001) after controlling for World Federation of Neurosurgical Societies (WFNS) grade (OR 3.35, 95% CI 1.18-9.51, p = 0.023) and modified Fisher grade (OR 6.07, 95% CI 2.03-18.14, p = 0.001). WFNS grade (area under the curve [AUC] = 0.792), modified Fisher grade (AUC = 0.731), and Lp-PLA2 level (D0; AUC = 0.710) were all strong predictors of DCI. The predictive powers of WFNS grade, modified Fisher grade, and Lp-PLA2 (D0) were comparable (WFNS grade vs Lp-PLA2: p = 0.233; modified Fisher grade vs Lp-PLA2: p = 0.771). The poor-grade patients with Lp-PLA2 (D0) > 200 μg/L had significantly worse DCI survival rate than poor-grade patients with Lp-PLA2 (D0) ≤ 200 μg/L (p < 0.001).

CONCLUSIONS

The serum level of Lp-PLA2 was significantly elevated in patients with DCI, and decreased within the first 2 days after admission. Lp-PLA2 in the early stages of aSAH might be a novel predictive biomarker for the occurrence of DCI.

From Analysis of Ischemic Mouse Brain Proteome to Identification of Human Serum Clusterin as a Potential Biomarker for Severity of Acute Ischemic Stroke

Ischemic stroke is a devastating neurological disease that can cause permanent brain damage, but to date, few biomarkers are available to reliably assess the severity of injury during acute onset. In this study, quantitative proteomic analysis of ischemic mouse brain detected the increase in expression levels of clusterin (CLU) and cystatin C (CST3). Since CLU is a secretary protein, serum samples (n = 70) were obtained from acute ischemic stroke (AIS) patients within 24 h of stroke onset and together with 70 matched health controls. Analysis of CLU levels indicated significantly higher levels in AIS patients than healthy controls (14.91 ± 4.03 vs. 12.79 ± 2.22 ng/L; P = 0.0004). Analysis of serum CST3 also showed significant increase in AIS patients as compared with healthy controls (0.90 ± 0.19 vs. 0.84 ± 0.12 ng/L; P = 0.0064). The serum values of CLU were also positively correlated with the NIH Stroke Scale (NIHSS) scores, the time interval after stroke onset, as well as major stroke risk factors associated with lipid profile. These data demonstrate that elevated levels of serum CLU and CST3 are independently associated with AIS and may serve as peripheral biomarkers to aid clinical assessment of AIS and its severity. This pilot study thus contributes to progress toward preclinical proteomic screening by using animal models and allows translation of results from bench to bedside.

Interleukin-6 Levels in Cerebrospinal Fluid and Plasma in Patients with Severe Spontaneous Subarachnoid Hemorrhage

BACKGROUND

Inflammatory processes play a key role in the pathophysiology of subarachnoid hemorrhage (SAH). This study evaluated whether different temporal patterns of intrathecal and systemic inflammation could be identified in the acute phase after SAH. The intensity of the inflammation was also assessed in clinical subgroups.

METHODS

Cerebrospinal fluid (CSF) and blood samples were collected at days 1, 4, and 10 after ictus in 44 patients with severe SAH. Interleukin-6 (IL-6) was analyzed by a routine monoclonal antibody-based method. Median IL-6 values for each day were calculated. Day 4 IL-6 values were compared in dichotomized groups (age, sex, World Federation of Neurosurgical Societies [WFNS] grade, Fisher scale grade, outcome, vasospasm, central nervous system infection and systemic infections).

RESULTS

CSF IL-6 levels were significantly elevated from day 1 to days 4 and 10, whereas plasma IL-6 showed a different trend at lower levels. Median CSF IL-6 concentrations for days 1, 4, and 10 were 876.5, 3361, and 1567 ng/L, whereas plasma was 26, 27.5, and 15.9 ng/L, respectively. No significant differences in CSF concentrations were observed between the subgroups, with the most prominent one being in day 4 IL-6 in the WFNS subgroups (grades 1-3 vs. 4-5, 1158.5 vs. 5538 ng/L; P = 0.056). Patients with systemic infection had significantly higher plasma IL-6 concentrations than patients without infection (31 vs. 16.05 ng/L, respectively; P = 0.028).

CONCLUSIONS

Distinctly different inflammatory patterns could be seen intrathecally compared with the systemic circulation. In plasma, a significant difference in the intensity of the inflammation was seen in cases with systemic infection. No other subgroup showed statistically significant differences.

The effect of succinate on brain NADH/NAD+ redox state and high energy phosphate metabolism in acute traumatic brain injury

A key pathophysiological process and therapeutic target in the critical early post-injury period of traumatic brain injury (TBI) is cell mitochondrial dysfunction; characterised by elevation of brain lactate/pyruvate (L/P) ratio in the absence of hypoxia. We previously showed that succinate can improve brain extracellular chemistry in acute TBI, but it was not clear if this translates to a change in downstream energy metabolism. We studied the effect of microdialysis-delivered succinate on brain energy state (phosphocreatine/ATP ratio (PCr/ATP)) with 31P MRS at 3T, and tissue NADH/NAD+ redox state using microdialysis (L/P ratio) in eight patients with acute major TBI (mean 7 days). Succinate perfusion was associated with increased extracellular pyruvate (+26%, p < 0.0001) and decreased L/P ratio (-13%, p < 0.0001) in patients overall (baseline-vs-supplementation over time), but no clear-cut change in 31P MRS PCr/ATP existed in our cohort (p > 0.4, supplemented-voxel-vs-contralateral voxel). However, the percentage decrease in L/P ratio for each patient following succinate perfusion correlated significantly with their percentage increase in PCr/ATP ratio (Spearman's rank correlation, r = -0.86, p = 0.024). Our findings support the interpretation that L/P ratio is linked to brain energy state, and that succinate may support brain energy metabolism in select TBI patients suffering from mitochondrial dysfunction.

Neuroglobin as a Novel Biomarker for Predicting Poor Outcomes in Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Neuroglobin (Ngb) has a high affinity for oxygen and helps prevent hypoxic-ischemic brain damage. In this study we analyzed the relationship between Ngb levels and clinical outcomes of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

Serum Ngb levels were measured in 58 patients with aSAH and 27 control individuals using the enzyme-linked immunosorbent assay. To continuously assess aSAH, we measured serum Ngb levels on days 1, 2, 3, 5, and 7 after aSAH. Clinical data were collected using the Hunt and Hess Scale, the Glasgow Coma Scale (GCS), the World Federation of Neurological Surgeons (WFNS) Scale, and the modified Fisher Scale. Clinical outcomes included 6-month mortality and 6-month unfavorable outcomes (modified Rankin Scale (mRS) score of 3-6).

RESULTS

Serum Ngb levels increased after aSAH, peaked on day 2, and then gradually decreased. Serum Ngb levels on admission were higher in the patient group than in the control group (7.67 ± 2.56 ng/mL vs. 6.45 ± 0.88 ng/mL, P < 0.05). Multivariate logistic regression analysis indicated that serum Ngb levels on day 2 after aSAH were independently related to 6-month mortality (odds ratio [OR] = 0.265, 95% confidence interval [CI] = 0.094-0.747, P < 0.05) and 6-month unfavorable outcomes (OR = 1.919, 95% CI = 1.158-3.180, P < 0.05), and receiver operating characteristic curve analysis showed that serum Ngb levels on day 2 predicted 6-month mortality and 6-month unfavorable outcomes, with areas under the curve of 0.893 (P < 0.05; 95% CI, 0.812-0.974) and 0.818 (P < 0.05; 95% CI, 0.691-0.954), respectively, based on the best thresholds.

CONCLUSIONS

Serum Ngb levels on day 2 after aSAH were strongly associated with poor outcomes in aSAH, suggesting that Ngb may be a novel biomarker for predicting poor outcomes in aSAH.

Multimodality neuromonitoring in severe pediatric traumatic brain injury

Each year, the annual hospitalization rates of traumatic brain injury (TBI) in children in the United States are 57.7 per 100K in the <5 years of age and 23.1 per 100K in the 5-14 years age group. Despite this, little is known about the pathophysiology of TBI in children and how to manage it most effectively. Historically, TBI management has been guided by clinical examination. This has been assisted progressively by clinical imaging, intracranial pressure (ICP) monitoring, and finally a software that can calculate optimal brain physiology. Multimodality monitoring affords clinicians an early indication of secondary insults to the recovering brain including raised ICP and decreased cerebral perfusion pressure. From variables such as ICP and arterial blood pressure, correlations can be drawn to determine parameters of cerebral autoregulation (pressure reactivity index) and "optimal cerebral perfusion pressure" at which the vasculature is most reactive. More recently, significant advances using both direct and near-infrared spectroscopy-derived brain oxygenation plus cerebral microdialysis to drive management have been described. Here in, we provide a perspective on the state-of-the-art techniques recently implemented in clinical practice for pediatric TBI.

Assessing Metabolism and Injury in Acute Human Traumatic Brain Injury with Magnetic Resonance Spectroscopy: Current and Future Applications

Traumatic brain injury (TBI) triggers a series of complex pathophysiological processes. These include abnormalities in brain energy metabolism; consequent to reduced tissue pO₂ arising from ischemia or abnormal tissue oxygen diffusion, or due to a failure of mitochondrial function. In vivo magnetic resonance spectroscopy (MRS) allows non-invasive interrogation of brain tissue metabolism in patients with acute brain injury. Nuclei with “spin,” e.g., ¹H, ³¹P, and ¹³C, are detectable using MRS and are found in metabolites at various stages of energy metabolism, possessing unique signatures due to their chemical shift or spin–spin interactions (J-coupling). The most commonly used clinical MRS technique, ¹H MRS, uses the great abundance of hydrogen atoms within molecules in brain tissue. Spectra acquired with longer echo-times include N-acetylaspartate (NAA), creatine, and choline. NAA, a marker of neuronal mitochondrial activity related to adenosine triphosphate (ATP), is reported to be lower in patients with TBI than healthy controls, and the ratio of NAA/creatine at early time points may correlate with clinical outcome. ¹H MRS acquired with shorter echo times produces a more complex spectrum, allowing detection of a wider range of metabolites.³¹ P MRS detects high-energy phosphate species, which are the end products of cellular respiration: ATP and phosphocreatine (PCr). ATP is the principal form of chemical energy in living organisms, and PCr is regarded as a readily mobilized reserve for its replenishment during periods of high utilization. The ratios of high-energy phosphates are thought to represent a balance between energy generation, reserve and use in the brain. In addition, the chemical shift difference between inorganic phosphate and PCr enables calculation of intracellular pH.¹³ C MRS detects the ¹³C isotope of carbon in brain metabolites. As the natural abundance of ¹³C is low (1.1%), ¹³C MRS is typically performed following administration of ¹³C-enriched substrates, which permits tracking of the metabolic fate of the infused ¹³C in the brain over time, and calculation of metabolic rates in a range of biochemical pathways, including glycolysis, the tricarboxylic acid cycle, and glutamate–glutamine cycling. The advent of new hyperpolarization techniques to transiently boost signal in ¹³C-enriched MRS in vivo studies shows promise in this field, and further developments are expected.

Metabolomics Profiling As a Diagnostic Tool in Severe Traumatic Brain Injury

Traumatic brain injury (TBI) is a complex disease with a multifaceted pathophysiology. Impairment of energy metabolism is a key component of secondary insults. This phenomenon is a consequence of multiple potential mechanisms including diffusion hypoxia, mitochondrial failure, and increased energy needs due to systemic trauma responses, seizures, or spreading depolarization. The degree of disturbance in brain metabolism is affected by treatment interventions and reflected in clinical patient outcome. Hence, monitoring of these secondary events in peripheral blood will provide a window into the pathophysiological course of severe TBI. New methods for assessing perturbation of brain metabolism are needed in order to monitor on-going pathophysiological processes and thus facilitate targeted interventions and predict outcome. Circulating metabolites in peripheral blood may serve as sensitive markers of pathological processes in TBI. The levels of these small molecules in blood are less dependent on the integrity of the blood–brain barrier as compared to protein biomarkers. We have recently characterized a specific metabolic profile in serum that is associated with both initial severity and patient outcome of TBI. We found that two medium-chain fatty acids, octanoic and decanoic acids, as well as several sugar derivatives are significantly associated with the severity of TBI. The top ranking peripheral blood metabolites were also highly correlated with their levels in cerebral microdialyzates. Based on the metabolite profile upon admission, we have been able to develop a model that accurately predicts patient outcome. Moreover, metabolomics profiling improved the performance of the well-established clinical prognostication model. In this review, we discuss metabolomics profiling in patients with severe TBI. We present arguments in support of the need for further development and validation of circulating biomarkers of cerebral metabolism and for their use in assessing patients with severe TBI.

Big Data in traumatic brain injury; promise and challenges

Traumatic brain injury (TBI) is a spectrum disease of overwhelming complexity, the research of which generates enormous amounts of structured, semi-structured and unstructured data. This resulting big data has tremendous potential to be mined for valuable information regarding the "most complex disease of the most complex organ". Big data analyses require specialized big data analytics applications, machine learning and artificial intelligence platforms to reveal associations, trends, correlations and patterns not otherwise realized by current analytical approaches. The intersection of potential data sources between experimental TBI and clinical TBI research presents inherent challenges for setting parameters for the generation of common data elements and to mine existing legacy data that would allow highly translatable big data analyses. In order to successfully utilize big data analyses in TBI, we must be willing to accept the messiness of data, collect and store all data and give up causation for correlation. In this context, coupling the big data approach to established clinical and pre-clinical data sources will transform current practices for triage, diagnosis, treatment and prognosis into highly integrated evidence-based patient care.

Treatment of traumatic brain injury with 17α-ethinylestradiol-3-sulfate in a rat model

OBJECTIVE

17α-ethynylestradiol-3-sulfate (EE-3-SO4) is a highly water-soluble synthetic estrogen that has an extended half-life (∼ 10 hours) over that of naturally occurring estrogen (∼ 10 minutes). In this study, EE-3-SO4 was evaluated in a lateral fluid percussion–induced traumatic brain injury (TBI) model in rats.

METHODS

A total of 9 groups of Sprague-Dawley rats underwent craniectomy. Twenty-four hours later, lateral fluid percussion was applied to 6 groups of animals to induce TBI; the remaining 3 groups served as sham control groups. EE-3-SO4 (1 mg/kg body weight in 0.4 ml/kg body weight) or saline (vehicle control) was injected intravenously 1 hour after TBI; saline was injected in all sham animals. One day after EE-3-SO4/saline injection, intracranial pressure (ICP), cerebral perfusion pressure (CPP), and partial brain oxygen pressure (PbtO2) were measured in Groups 1–3 (2 TBI groups and 1 sham group), and brain edema, diffusion axonal injury, and cerebral glycolysis were assessed in Groups 4–6 using MRI T2 mapping, diffusion tensor imaging (DTI), and FDG-PET imaging, respectively. Four days after dosing, the open-field anxiety of animals was assessed in Groups 7–9 by measuring the duration that each animal spent in the center area of an open chamber during 4 minutes of monitoring.

RESULTS

EE-3-SO4 significantly lowered ICP while raising CPP and PbtO2, compared with vehicle treatment in TBI-induced animals (p < 0.05). The mean size of cerebral edema of TBI animals treated with EE-3-SO4 was 25 ± 3 mm3 (mean ± SE), which was significantly smaller than that of vehicle-treated animals (67 ± 6 mm3, p < 0.001). Also, EE-3-SO4 treatment significantly increased the fractional anisotropy of the white matter in the ipsilateral side (p = 0.003) and cerebral glycolysis (p = 0.014). The mean duration that EE-3-SO4-treated animals spent in the center area was 12 ± 2 seconds, which was significantly longer than that of vehicle-treated animals (4 ± 1 seconds; p = 0.008) but not different from that of sham animals (11 ± 3 seconds; p > 0.05).

CONCLUSIONS

These data support the clinical use of EE-3-SO4 for early TBI treatment.

Plasma Soluble Urokinase-Type Plasminogen Activator Receptor Is Not Associated with Neurological Outcome in Patients with Aneurysmal Subarachnoid Hemorrhage

Object

Aneurysmal subarachnoid hemorrhage (aSAH) is a common cause of death or long-term disability. Despite advances in neurocritical care, there is still only a very limited ability to monitor the development of secondary brain injury or to predict neurological outcome after aSAH. Soluble urokinase-type plasminogen activator receptor (suPAR) has shown potential as a prognostic and as an inflammatory biomarker in a wide range of critical illnesses since it displays an association with overall immune system activation. This is the first time that suPAR has been evaluated as a prognostic biomarker in aSAH.

Methods

In this prospective population-based study, plasma suPAR levels were measured in aSAH patients (n = 47) for up to 5 days. suPAR was measured at 0, 12, and 24 h after patient admission to the intensive care unit (ICU) and daily thereafter until he/she was transferred from the ICU. The patients’ neurological outcome was evaluated with the modified Rankin Scale (mRS) at 6 months after aSAH.

Results

suPAR levels (n = 47) during the first 24 h after aSAH were comparable in groups with a favorable (mRS 0–2) or an unfavorable (mRS 3–6) outcome. suPAR levels during the first 24 h were not associated with the findings in the primary brain CT, with acute hydrocephalus, or with antimicrobial medication use during 5-days’ follow-up. suPAR levels were associated with generally accepted inflammatory biomarkers (C-reactive protein, leukocyte count).

Conclusion

Plasma suPAR level was not associated with either neurological outcome or selected clinical conditions. While suPAR is a promising biomarker for prognostication in several conditions requiring intensive care, it did not reveal any value as a prognostic biomarker after aSAH.

The nature of early astroglial protection-Fast activation and signaling

Our present review is focusing on the uniqueness of balanced astroglial signaling. The balance of excitatory and inhibitory signaling within the CNS is mainly determined by sharp synaptic transients of excitatory glutamate (Glu) and inhibitory γ-aminobutyrate (GABA) acting on the sub-second timescale. Astroglia is involved in excitatory chemical transmission by taking up i) Glu through neurotransmitter-sodium transporters, ii) K⁺ released due to presynaptic action potential generation, and iii) water keeping osmotic pressure. Glu uptake-coupled Na⁺ influx may either ignite long-range astroglial Ca²⁺ transients or locally counteract over-excitation via astroglial GABA release and increased tonic inhibition. Imbalance of excitatory and inhibitory drives is associated with a number of disease conditions, including prevalent traumatic and ischaemic injuries or the emergence of epilepsy. Therefore, when addressing the potential of early therapeutic intervention, astroglial signaling functions combating progress of Glu excitotoxicity is of critical importance. We suggest, that excitotoxicity is linked primarily to over-excitation induced by the impairment of astroglial Glu uptake and/or GABA release. Within this framework, we discuss the acute alterations of Glu-cycling and metabolism and conjecture the therapeutic promise of regulation. We also confer the role played by key carrier proteins and enzymes as well as their interplay at the molecular, cellular, and organ levels. Moreover, based on our former studies, we offer potential prospect on the emerging theme of astroglial succinate sensing in course of Glu excitotoxicity.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

Background

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein “biomarker” of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

Results

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

Conclusion

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

Microdialysis Monitoring in Clinical Traumatic Brain Injury and Its Role in Neuroprotective Drug Development

Injuries to the central nervous system continue to be vast contributors to morbidity and mortality; specifically, traumatic brain injury (TBI) is the most common cause of death during the first four decades of life. Several modalities are used to monitor patients suffering from TBI in order to prevent detrimental secondary injuries. The microdialysis (MD) technique, introduced during the 1990s, presents the treating physician with a robust monitoring tool for brain chemistry in addition to conventional intracranial pressure monitoring. Nevertheless, some limitations remain, such as limited spatial resolution. Moreover, while there have been several attempts to develop new potential pharmacological therapies in TBI, there are currently no available drugs which have shown clinical efficacy that targets the underlying pathophysiology, despite various trials investigating a plethora of pharmaceuticals. Specifically in the brain, MD is able to demonstrate penetration of the drug through the blood-brain barrier into the brain extracellular space at potential site of action. In addition, the downstream effects of drug action can be monitored directly. In the future, clinical MD, together with other monitoring modalities, can identify specific pathological substrates which require tailored treatment strategies for patients suffering from TBI.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

BACKGROUND

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein "biomarker" of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

RESULTS

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

CONCLUSION

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

Mapping the Connectome Following Traumatic Brain Injury

There is a paucity of accurate and reliable biomarkers to detect traumatic brain injury, grade its severity, and model post-traumatic brain injury (TBI) recovery. This gap could be addressed via advances in brain mapping which define injury signatures and enable tracking of post-injury trajectories at the individual level. Mapping of molecular and anatomical changes and of modifications in functional activation supports the conceptual paradigm of TBI as a disorder of large-scale neural connectivity. Imaging approaches with particular relevance are magnetic resonance techniques (diffusion weighted imaging, diffusion tensor imaging, susceptibility weighted imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, and positron emission tomographic methods including molecular neuroimaging). Inferences from mapping represent unique endophenotypes which have the potential to transform classification and treatment of patients with TBI. Limitations of these methods, as well as future research directions, are highlighted.

Clinical relevance of midline fluid percussion brain injury: Acute deficits, chronic morbidities and the utility of biomarkers

BACKGROUND

After 30 years of characterisation and implementation, fluid percussion injury (FPI) is firmly recognised as one of the best-characterised reproducible and clinically relevant models of TBI, encompassing concussion through diffuse axonal injury (DAI). Depending on the specific injury parameters (e.g. injury site, mechanical force), FPI can model diffuse TBI with or without a focal component and may be designated as mild-to-severe according to the chosen mechanical forces and resulting acute neurological responses. Among FPI models, midline FPI may best represent clinical diffuse TBI, because of the acute behavioural deficits, the transition to late-onset behavioural morbidities and the absence of gross histopathology.

REVIEW

The goal here was to review acute and chronic physiological and behavioural deficits and morbidities associated with diffuse TBI induced by midline FPI. In the absence of neurodegenerative sequelae associated with focal injury, there is a need for biomarkers in the diagnostic, prognostic, predictive and therapeutic approaches to evaluate outcomes from TBI.

CONCLUSIONS

The current literature suggests that midline FPI offers a clinically-relevant, validated model of diffuse TBI to investigators wishing to evaluate novel therapeutic strategies in the treatment of TBI and the utility of biomarkers in the delivery of healthcare to patients with brain injury.

Biomarkers of brain injury following an American football game: A pilot study

The goals of this study were to determine if the biomarkers of head injury, NSE and S100B, increased in serum following an American football game. Serum creatine kinase (CK) and cortisol levels were also measured to determine muscle damage and stress caused by the football game. NSE, S100B, CK, and cortisol were measured in the serum of 17 football players before and after a collegiate junior varsity football game. No head injuries were reported by the players, athletic training staff, or coaches yet both NSE (Pre-game: 7.0 μg•L-1 ± 2.2 versus Post-game: 13.1 μg•L-1 ± 7.0, P <0.001) and S100B (Pre-game: 0.013 μg•L-1 ± 0.012 versus Post-game: 0.069 μg•L-1 ± 0.036, P <0.001) increased significantly. Neither CK (Pre-game: 90.5 U•L-1 ± 41.9 versus Post-game: 120.2 U•L-1 ± 62.7, P = 0.116) nor cortisol (Pre-game: 369.2 nmoles•L-1 ± 159.8 versus Post-game: 353.0 nmoles•L-1 ± 170.5, P = 0.349) increased significantly following the football game. There was little correlation found between S100B and body mass (R2 = 0.029) or CK (R2 = 0.352) levels. Although serum NSE and S100B increase as a result of playing in an American football game, the values are similar to or lower than levels found following competition in other contact and non-contact sports. Furthermore, the lack of correlation between S100B and body mass or CK indicates that S100B increases independent of body mass or muscle injury.

Kinetic modelling of serum S100b after traumatic brain injury

Background

An understanding of the kinetics of a biomarker is essential to its interpretation. Despite this, little kinetic modelling of blood biomarkers can be found in the literature. S100b is an astrocyte related marker of brain injury used primarily in traumatic brain injury (TBI). Serum levels are expected to be the net result of a multi-compartmental process. The optimal sample times for TBI prognostication, and to follow injury development, are unclear. The purpose of this study was to develop a kinetic model to characterise the temporal course of serum S100b concentration after primary traumatic brain injury.

Methods

Data of serial serum S100b samples from 154 traumatic brain injury patients in a neurointensive care unit were retrospectively analysed, including only patients without secondary peaks of this biomarker. Additionally, extra-cranial S100b can confound samples earlier than 12 h after trauma and were therefore excluded. A hierarchical, Bayesian gamma variate kinetic model was constructed and the parameters estimated by Markov chain Monte Carlo sampling.

Results

We demonstrated that S100b concentration changes dramatically over timescales that are clinically important for early prognostication with a peak at 27.2 h (95 % credible interval [25.6, 28.8]). Baseline S100b levels was found to be 0.11 μg/L (95 % credible interval [0.10, 0.12]).

Conclusions

Even small differences in injury to sample time may lead to marked changes in S100b during the first days after injury. This must be taken into account in interpretation. The model offers a way to predict the peak and trajectory of S100b from 12 h post trauma in TBI patients, and to identify deviations from this, possibly indicating a secondary event. Kinetic modelling, providing an equation for the peak and projection, may offer a way to reduce the ambiguity in interpretation of, in time, randomly sampled acute biomarkers and may be generally applicable to biomarkers with, in time, well defined hits.

Thioredoxin-Mimetic-Peptides Protect Cognitive Function after Mild Traumatic Brain Injury (mTBI)

Mild traumatic brain injury (mTBI) is recognized as a common injury among children, sportsmen, and elderly population. mTBI lacks visible objective structural brain damage but patients frequently suffer from long-lasting cognitive, behavioral and emotional difficulties associated with biochemical and cellular changes. Currently there is no effective treatment for patients with mTBI. The thioredoxin reductase/thioredoxin pathway (TrxR/Trx1) has both anti-inflammatory and anti-oxidative properties. If the system is compromised, Trx1 remains oxidized and triggers cell death via an ASK1-Trx1 signal transduction mechanism. We previously showed tri and tetra peptides which were derived from the canonical -CxxC- motif of the Trx1-active site, called thioredoxin mimetic (TXM) peptides, reversed inflammatory and oxidative stress damage mimicking Trx1 activity. Here, TXM-peptides were examined for protecting cognitive function following weight drop closed-head injury in a mouse model of mTBI. TXM-CB3 (AcCys-Pro-CysNH₂), TXM-CB13 (DY-70; AcCys-Met-Lys-CysNH₂) or AD4 (ACysNH₂) were administered at 50 mg/kg, 60 min after injury and cognitive performance was monitored by the novel-object-recognition and Y-maze tests. Behavioral deficits subsequent to mTBI injury were reversed by a single dose of TXM-CB3, TXM-CB13 and, to a lesser extent, by AD4. TXM-CB13 similar to TXM-CB3 and AD4 reversed oxidative stress-induced phosphorylation of mitogen-activated kinases, p38^MAPK and c-Jun N-terminal kinase, (JNK) in human neuronal SH-SY5Y cells. We conclude that significantly improved cognitive behavior post mTBI by the TXM-peptides could result from anti-apoptotic, and/or anti-inflammatory activities. Future preclinical studies are required to establish the TXM-peptides as potential therapeutic drugs for brain injuries.

Traumatic Axonal Injury: Mechanisms and Translational Opportunities

Traumatic axonal injury (TAI) is an important pathoanatomical subgroup of traumatic brain injury (TBI) and a major driver of mortality and functional impairment. Experimental models have provided insights into the effects of mechanical deformation on the neuronal cytoskeleton and the subsequent processes that drive axonal injury. There is also increasing recognition that axonal or white matter loss may progress for years post-injury and represent one mechanistic framework for progressive neurodegeneration after TBI. Previous trials of novel therapies have failed to make an impact on clinical outcome, in both TBI in general and TAI in particular. Recent advances in understanding the cellular and molecular mechanisms of injury have the potential to translate into novel therapeutic targets.

Multiple therapeutic targets are emerging that offer the potential to reduce secondary brain injury at a cellular level. These include cytoskeletal and membrane stabilisation, control of calcium flux and calpain activation, optimisation of cellular energetics, and modulation of the inflammatory response.

Wallerian degeneration, as occurs following an axonal injury, is an active, cell-autonomous death pathway that involves failure of axonal transport to deliver key enzymes involved in NAD biosynthesis.

Chronic microglial activation occurs following traumatic brain injury (TBI) and may persist for decades afterwards. This ongoing response has been linked to long-term neurodegeneration, particularly of white matter tracts.

Phagoptosis is the process whereby physiologically stressed but otherwise viable neurons are phagocytosed by microglia in response to a range of eat-me signals induced by tissue injury.

Neuron-Specific Enolase Is Correlated to Compromised Cerebral Metabolism in Patients Suffering from Acute Bacterial Meningitis; An Observational Cohort Study

Introduction

Patients suffering from acute bacterial meningitis (ABM) with a decreased level of consciousness have been shown to have an improved clinical outcome if treated with an intracranial pressure (ICP) guided therapy. By using intracranial microdialysis (MD) to monitor cerebral metabolism in combination with serum samples of biomarkers indicating brain tissue injury, S100B and Neuron Specific Enolase (NSE), additional information might be provided. The aim of this study was to evaluate biomarkers in serum and MD parameters in patients with ABM.

Methods

From a prior study on patients (n = 52) with a confirmed ABM and impaired consciousness (GCS ≤ 9, or GCS = 10 combined with lumbar spinal opening pressure > 400 mmH₂O), a subgroup of patients (n = 21) monitored with intracerebral MD and biomarkers was included in the present study. All patients were treated in the NICU with intracranial pressure (ICP) guided therapy. Serum biomarkers were obtained at admission and every 12 hours. The MD parameters glucose, lactate, pyruvate and glycerol were analyzed. Outcome was assessed at 12–55 months after discharge from hospital. Mann-Whitney U-Test and Wilcoxon matched-pairs signed rank test were applied.

Results

The included patients had a mean GCS of 8 (range, 3–10) on admission and increased ICP (>20 mmHg) was observed in 62% (n = 13/21) of the patients. Patients with a lactate:pyruvate ratio (LPR) >40 (n = 9/21, 43%) had significantly higher peak levels of serum NSE (p = 0.03), with similar, although non-significant observations made in patients with high levels of glycerol (>500 μmol/L, p = 0.11) and those with a metabolic crisis (Glucose <0.8 mmol/L, LPR >25, p = 0.09). No associations between serum S100B and MD parameters were found. Furthermore, median MD glucose levels decreased significantly between day 1 (0–24h) and day 3 (48–72h) after admission to the NICU (p = 0.0001). No correlation between MD parameters or biomarkers and outcome was found.

Conclusion

In this observational cohort study, we were able to show that cerebral metabolism is frequently affected in patients with ABM. Furthermore, patients with high LPR (LPR>40) had significantly higher levels of NSE, suggesting ongoing deterioration in compromised cerebral tissue. However, the potential clinical impact of MD and biomarker monitoring in ABM patients will need to be further elaborated in larger clinical trials.

Increased plasma UCH-L1 after aneurysmal subarachnoid hemorrhage is associated with unfavorable neurological outcome

OBJECTIVE

Aneurysmal subarachnoid hemorrhage (aSAH) is a common cause of long-term disability and death. After primary hemorrhage, secondary brain injury is the main cause of mortality and morbidity. Despite extensive research, reliable prognostic biomarkers are lacking. We measured ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) levels in aSAH patients to evaluate its prognostic potential. This is the first time that plasma UCH-L1 has been studied as a potential prognostic biomarker in patients with aSAH.

METHODS

In this prospective population-based study, UCH-L1 levels were measured in aSAH patients (n=47) for up to five days. UCH-L1 was measured at 0, 12 and 24h after the admission to the intensive care unit (ICU) and daily thereafter until the patient was transferred from the ICU. Only patients whose UCH-L1 was measured within 24h from aSAH were included in the study. The patients' neurological outcome was evaluated with the modified Rankin Scale (mRS) at six months after aSAH.

RESULTS

UCH-L1 levels during the first 24h after aSAH were not significantly different between the groups with favorable (mRS 0-2) and unfavorable (mRS 3-6) neurological outcome. In 22 patients, UCH-L1 levels were obtained for up to five days. In this subgroup, UCH-L1 measured at day five showed significant elevation from baseline levels in patients with unfavorable outcome (p=0.026). Elevated UCH-L1 levels at day five were higher in patients with unfavorable outcome than in patients with favorable outcome (p=0.001).

CONCLUSIONS

Elevated UCH-L1 levels during the five-day follow-up were associated with unfavorable neurological outcome. Repetitive measurements of UCH-L1 concentrations with an emphasis on change relative to the individual baseline could be the optimal approach for future clinical studies.

Clinical utility of brain stimulation modalities following traumatic brain injury: current evidence

Traumatic brain injury (TBI) remains the main cause of disability and a major public health problem worldwide. This review focuses on the neurophysiology of TBI, and the rationale and current state of evidence of clinical application of brain stimulation to promote TBI recovery, particularly on consciousness, cognitive function, motor impairments, and psychiatric conditions. We discuss the mechanisms of different brain stimulation techniques including major noninvasive and invasive stimulations. Thus far, most noninvasive brain stimulation interventions have been nontargeted and focused on the chronic phase of recovery after TBI. In the acute stages, there is limited available evidence of the efficacy and safety of brain stimulation to improve functional outcomes. Comparing the studies across different techniques, transcranial direct current stimulation is the intervention that currently has the higher number of properly designed clinical trials, though total number is still small. We recognize the need for larger studies with target neuroplasticity modulation to fully explore the benefits of brain stimulation to effect TBI recovery during different stages of recovery.