Cerebral blood flow as a predictor of outcome following traumatic brain injury

Supra-Prophylactic Doses of Enoxaparin Reduces Fibrin Deposition Without Exacerbation of Intracerebral Hemorrhage in a Rat Model of Penetrating Traumatic Brain Injury

Deep vein thrombosis and pulmonary embolism prophylaxis is an important part of trauma care. Despite an increased risk of thrombotic complications, the use of venous thrombosis chemoprophylaxis in penetrating traumatic brain injury (pTBI) patients is met with reluctance from neurosurgeons because of concern for the exacerbation of intracerebral hemorrhage. The objective of this study was to provide initial pre-clinical evidence of the effects of Lovenox (LVX) administration following pTBI with significant intracerebral hemorrhage. Sprague-Dawley rats received a penetrating ballistic-like brain injury. Animals were randomly divided into two groups following injury: LVX (25 mg/kg) or vehicle (VEH, saline). LVX or vehicle was administered subcutaneously beginning 24 h after the injury and continued daily for 7 days post-injury. A neurological assessment was performed daily and magnetic resonance imaging (MRI) was performed at baseline, 1, 2, 3, and 7 days post-injury. Following the final MRI, brains were isolated and prepared for histological analysis. Thromboelastography demonstrated dramatic anticoagulation effects which were confirmed by significant increases in partial thromboplastin time (p < 0.001). Daily neurological assessment revealed no worsening of functional deficits following LVX treatment. MRI analysis demonstrated no differences in cerebral edema or intracranial hemorrhage volumes between treatment groups at any tested post-injury time points. However, LVX elicited a significant reduction in fibrin deposition in the ipsilateral striatum and lesion site at 7 days post-injury (p < 0.05). Serum levels of beta-amyloid were decreased at 7 days following LVX treatment (p < 0.05) which may indicate neuroprotective effects but was not correlated to brain levels. The results presented indicate that administration of LVX at a dose capable of inducing anticoagulation is safe in a rodent model of pTBI without exacerbation of intracerebral hemorrhage within the first 7 days of injury.

Choosing a camera and optimizing system parameters for speckle contrast optical spectroscopy

Speckle contrast optical spectroscopy (SCOS) is an emerging camera-based technique that can measure human cerebral blood flow (CBF) with high signal-to-noise ratio (SNR). At low photon flux levels typically encountered in human CBF measurements, camera noise and nonidealities could significantly impact SCOS measurement SNR and accuracy. Thus, a guide for characterizing, selecting, and optimizing a camera for SCOS measurements is crucial for the development of next-generation optical devices for monitoring human CBF and brain function. Here, we provide such a guide and illustrate it by evaluating three commercially available complementary metal-oxide-semiconductor cameras, considering a variety of factors including linearity, read noise, and quantization distortion. We show that some cameras that are well-suited for general intensity imaging could be challenged in accurately quantifying spatial contrast for SCOS. We then determine the optimal operating parameters for the preferred camera among the three and demonstrate measurement of human CBF with this selected low-cost camera. This work establishes a guideline for characterizing and selecting cameras as well as for determining optimal parameters for SCOS systems.

Anesthesia strategies for elderly patients with craniocerebral injury due to foreign-body penetration in the plateau region: a case report

Background

The administration of anesthesia for elderly individuals who are critically ill, suffering from severe craniocerebral injuries, and living in plateau regions presents a rare, intricate, and high-risk challenge. This case study outlines the specific anesthesia management protocols necessary for plateau-dwelling patients with significant craniocerebral damage undergoing prolonged invasive procedures.

Case report

A 76-year-old male patient had a 26-year history of foreign-body penetration of the skull and had experienced local purulent discharge and pain for the previous 20 days. The diagnoses included right hypoplasia, a foreign body in the skull with an infection, hypokalemia, hypoproteinemia, pulmonary fibrous foci, and bilateral pleural effusion. For almost 6 months, the patient suffered from recurring headaches, blurred vision, and sluggish bodily movement. The patient had a poor diet, poor sleep quality, normal urination, and no noticeable weight loss since the onset of the illness. The right anterior ear had a 2 cm skin abscess with yellow pus and a black metal foreign body tip. The left eyelid was red and swollen, and the left conjunctiva was hyperemic; the right eyelid showed no abnormalities, and both pupils were wide and round, with light and adjustment reflexes and no cyanosis on the lips. Skull development was normal. No dry or moist rales were audible in either lung. The heart rhythm was regular, and the heart rate was 50 bpm. Chest CT revealed left lung calcification foci, bilateral pleural effusion, and fiber foci in the lower lobes of both lungs.

Conclusion

Furthermore, the patient in question was of advanced age and had a complex medical history, including prolonged exposure to high altitudes and previous instances of severe craniocerebral trauma, among other uncommon pathophysiological characteristics. In particular, the patient also underwent surgical interventions at both high and low altitudes, adding to the complexity of their case. To ensure patient safety, close multidisciplinary collaboration, the development of a precise surgical plan, and the implementation of a suitable perioperative anesthetic management strategy are imperative.

Sleep, inflammation, and hemodynamics in rodent models of traumatic brain injury

Traumatic brain injury (TBI) can induce dysregulation of sleep. Sleep disturbances include hypersomnia and hyposomnia, sleep fragmentation, difficulty falling asleep, and altered electroencephalograms. TBI results in inflammation and altered hemodynamics, such as changes in blood brain barrier permeability and cerebral blood flow. Both inflammation and altered hemodynamics, which are known sleep regulators, contribute to sleep impairments post-TBI. TBIs are heterogenous in cause and biomechanics, which leads to different molecular and symptomatic outcomes. Animal models of TBI have been developed to model the heterogeneity of TBIs observed in the clinic. This review discusses the intricate relationship between sleep, inflammation, and hemodynamics in pre-clinical rodent models of TBI.

Neutrophil biology in injuries and diseases of the central and peripheral nervous systems

The role of inflammation in nervous system injury and disease is attracting increased attention. Much of that research has focused on microglia in the central nervous system (CNS) and macrophages in the peripheral nervous system (PNS). Much less attention has been paid to the roles played by neutrophils. Neutrophils are part of the granulocyte subtype of myeloid cells. These cells, like macrophages, originate and differentiate in the bone marrow from which they enter the circulation. After tissue damage or infection, neutrophils are the first immune cells to infiltrate into tissues and are directed there by specific chemokines, which act on chemokine receptors on neutrophils. We have reviewed here the basic biology of these cells, including their differentiation, the types of granules they contain, the chemokines that act on them, the subpopulations of neutrophils that exist, and their functions. We also discuss tools available for identification and further study of neutrophils. We then turn to a review of what is known about the role of neutrophils in CNS and PNS diseases and injury, including stroke, Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, spinal cord and traumatic brain injuries, CNS and PNS axon regeneration, and neuropathic pain. While in the past studies have focused on neutrophils deleterious effects, we will highlight new findings about their benefits. Studies on their actions should lead to identification of ways to modify neutrophil effects to improve health.

Cannabidiol's neuroprotective properties and potential treatment of traumatic brain injuries

Cannabidiol (CBD) has numerous pharmacological targets that initiate anti-inflammatory, antioxidative, and antiepileptic properties. These neuroprotective benefits have generated interest in CBD's therapeutic potential against the secondary injury cascade from traumatic brain injury (TBI). There are currently no effective broad treatment strategies for combating the damaging mechanisms that follow the primary injury and lead to lasting neurological consequences or death. However, CBD's effects on different neurotransmitter systems, the blood brain barrier, oxidative stress mechanisms, and the inflammatory response provides mechanistic support for CBD's clinical utility in TBI. This review describes the cascades of damage caused by TBI and CBD's neuroprotective mechanisms to counter them. We also present challenges in the clinical treatment of TBI and discuss important future clinical research directions for integrating CBD in treatment protocols. The mechanistic evidence provided by pre-clinical research shows great potential for CBD as a much-needed improvement in the clinical treatment of TBI. Upcoming clinical trials sponsored by major professional sport leagues are the first attempts to test the efficacy of CBD in head injury treatment protocols and highlight the need for further clinical research.

Influence of traumatic brain injury on ipsilateral and contralateral cortical perfusion in mice

Traumatic brain injury (TBI) is one of the most important causes of death in young adults. After brain injury cortical perfusion is impaired by cortical spreading depression, cerebral microvasospasm or microvascular thrombosis and contributes to secondary expansion of lesion into surrounding healthy brain tissue. The present study was designed to determine the regional cortical perfusion pattern after experimental TBI induced by controlled cortical impact (CCI) in male C57/BL6N mice. We performed a longitudinal time series analysis by Laser speckle contrast imaging (LSCI). Measurements were carried out before, immediately and 24 h after trauma. Immediately after CCI cortical perfusion in the lesion core dropped to 10 % of before injury (baseline; %BL) and to 21-24 %BL in the cortical area surrounding the core. Interestingly, cortical perfusion was also significantly reduced in the contralateral non-injured hemisphere (41-58 %BL) matching the corresponding brain region of the injured hemisphere. 24 h after CCI perfusion of the contralateral hemisphere returned to baseline level in the area corresponding to the lesion core, whereas the lateral area of the parietal cortex was hyperperfused (125 %BL). The lesion core region itself remained severely hypoperfused (18 to 26 %BL) during the observation period. TBI causes a maldistribution of both ipsi- and contralateral cerebral perfusion immediately after trauma, which persist for at least 24 h. Higher perfusion levels in the lesion core 24 h after trauma were associated with increased tissue damage, which supports the role of reperfusion injury for secondary brain damage after TBI.

Review: Emerging Eye-Based Diagnostic Technologies for Traumatic Brain Injury

The study of ocular manifestations of neurodegenerative disorders, Oculomics, is a growing field of investigation for early diagnostics, enabling structural and chemical biomarkers to be monitored overtime to predict prognosis. Traumatic brain injury (TBI) triggers a cascade of events harmful to the brain, which can lead to neurodegeneration. TBI, termed the "silent epidemic" is becoming a leading cause of death and disability worldwide. There is currently no effective diagnostic tool for TBI, and yet, early-intervention is known to considerably shorten hospital stays, improve outcomes, fasten neurological recovery and lower mortality rates, highlighting the unmet need for techniques capable of rapid and accurate point-of-care diagnostics, implemented in the earliest stages. This review focuses on the latest advances in the main neuropathophysiological responses and the achievements and shortfalls of TBI diagnostic methods. Validated and emerging TBI-indicative biomarkers are outlined and linked to ocular neuro-disorders. Methods detecting structural and chemical ocular responses to TBI are categorised along with prospective chemical and physical sensing techniques. Particular attention is drawn to the potential of Raman spectroscopy as a non-invasive sensing of neurological molecular signatures in the ocular projections of the brain, laying the platform for the first tangible path towards alternative point-of-care diagnostic technologies for TBI.

Genetic deletion of Krüppel-like factor 11 aggravates traumatic brain injury

BACKGROUND

The long-term functional recovery of traumatic brain injury (TBI) is hampered by pathological events, such as parenchymal neuroinflammation, neuronal death, and white matter injury. Krüppel-like transcription factor 11 (KLF 11) belongs to the zinc finger family of transcription factors and actively participates in various pathophysiological processes in neurological disorders. Up to now, the role and molecular mechanisms of KLF11 in regulating the pathogenesis of brain trauma is poorly understood.

METHODS

KLF11 knockout (KO) and wild-type (WT) mice were subjected to experimental TBI, and sensorimotor and cognitive functions were evaluated by rotarod, adhesive tape removal, foot fault, water maze, and passive avoidance tests. Brain tissue loss/neuronal death was examined by MAP2 and NeuN immunostaining, and Cresyl violet staining. White matter injury was assessed by Luxol fast blue staining, and also MBP/SMI32 and Caspr/Nav1.6 immunostaining. Activation of cerebral glial cells and infiltration of blood-borne immune cells were detected by GFAP, Iba-1/CD16/32, Iba-1/CD206, Ly-6B, and F4/80 immunostaining. Brian parenchymal inflammatory cytokines were measured with inflammatory array kits.

RESULTS

Genetic deletion of KLF11 worsened brain trauma-induced sensorimotor and cognitive deficits, brain tissue loss and neuronal death, and white matter injury in mice. KLF11 genetic deficiency in mice also accelerated post-trauma astrocytic activation, promoted microglial polarization to a pro-inflammatory phenotype, and increased the infiltration of peripheral neutrophils and macrophages into the brain parenchyma. Mechanistically, loss-of-KLF11 function was found to directly increase the expression of pro-inflammatory cytokines in the brains of TBI mice.

CONCLUSION

KLF11 acts as a novel protective factor in TBI. KLF11 genetic deficiency in mice aggravated the neuroinflammatory responses, grey and white matter injury, and impaired long-term sensorimotor and cognitive recovery. Elucidating the functional importance of KLF11 in TBI may lead us to discover novel pharmacological targets for the development of effective therapies against brain trauma.

Neutrophil-lymphocyte ratio as a predictor of outcome following traumatic brain injury: Systematic review and meta-analysis

OBJECTIVES

The neutrophil-to-lymphocyte ratio (NLR) is a simple and routinely performed hematological parameter; however, studies on NLR as a prognostic tool in traumatic brain injury (TBI) have yielded contradictory results.

MATERIALS AND METHODS

This systematic review and meta-analysis was conducted according to the Preferred Reporting Items in the Systematic Review and Meta-Analysis guidelines 2020. Electronic databases of PubMed, Cochrane Library, Web of Science, and Scopus were searched. The population consisted of TBI patients in the absence of moderate and severe extracranial injury. Day 1 NLR was taken for the analysis. The outcomes evaluated were mortality and the Glasgow Outcome Scale (GOS). No restrictions were placed on the language, year and country of publication, and duration of follow-up. Animal studies were excluded from the study. Studies, where inadequate data were reported for the outcomes, were included in the qualitative synthesis but excluded from the quantitative synthesis. Study quality was evaluated using the Newcastle-Ottawa scale (NOS). The risk of bias was estimated using the Cochrane RoBANS risk of bias tool.

RESULTS

We retrieved 7213 citations using the search strategy and 2097 citations were excluded based on the screening of the title and abstract. Full text was retrieved for 40 articles and subjected to the eligibility criteria, of which 28 were excluded from the study. Twelve studies were eligible for the synthesis of the systematic review while seven studies qualified for the meta-analysis. The median score of the articles was 8/9 as per NOS. The risk of selection bias was low in all the studies while the risk of detection bias was high in all except one study. Ten studies were conducted on adult patients, while two studies reported pediatric TBI. A meta-analysis for GOS showed that high NLR predicted unfavorable outcomes at ≥6 months with a mean difference of -5.18 (95% confidence interval: -10.04, -0.32); P = 0.04; heterogeneity (I2), being 98%. The effect estimates for NLR and mortality were a mean difference of -3.22 (95% confidence interval: -7.12, 0.68), P = 0.11, and an I2 of 85%. Meta-analysis for Area under the curve (AUC) receiver operating characteristic of the included studies showed good predictive power of NLR in predicting outcomes following TBI with AUC 0.706 (95% CI: 0.582-0.829).

CONCLUSION

A higher admission NLR predicts an increased mortality risk and unfavorable outcomes following TBI. However, future research will likely address the existing gaps.

The Clinical Differences of Patients With Traumatic Brain Injury in Plateau and Plain Areas

Objective

Traumatic brain injury (TBI) is a leading cause of death and disability, which tends to have a worse clinical recovery if it occurs in plateau areas than in plain areas. To explore the underlying cause of this outcome preliminarily, this retrospective study was conducted to compare the clinical differences of patients with TBI in plateau and plain areas.

Methods

In this study, 32 patients with TBI in plateau areas (altitude ≥ 4,000 m) and 32 in plain areas (altitude ≤ 1,000 m) were recruited according to the inclusion and exclusion criteria from June 2020 to December 2021. The collected data and compared parameters include clinical features, head CT presentations and Marshall classifications, hematology profile, lipid profile, coagulation profile, and multiorgan (cardiac, liver, renal) function within 24 h of hospital admission, as well as the treatment method and final outcome.

Results

There were no obvious differences in demographic characteristics, including gender, age, height, and weight, between patients with TBI in plateau and plain areas (all P > 0.05). Compared to patients with TBI in plain areas, the time before hospital admission was longer, heartbeat was slower, systolic blood pressure (SBP) was lower, and hospital stays were longer in patients with TBI in plateau areas (all P < 0.05). More importantly, elevated red blood cells (RBCs) count and hemoglobin (HGB) level, enhanced coagulation function, and higher rates of multiorgan (cardiac, liver, and renal) injury were found in patients with TBI in plateau areas (all P < 0.05).

Conclusion

Patients with TBI in plateau areas presented with altered clinical characteristics, enhanced coagulation function, and aggravated predisposition toward multiorgan (cardiac, liver, and renal) injury, compared to patients with TBI in plain areas. Future prospective studies are needed to further elucidate the influences of high altitude on the disease course of TBI.

Dynamics of neutrophil-to-lymphocyte ratio can be associated with clinical outcomes of children with moderate to severe traumatic brain injury: A retrospective observational study

BACKGROUND

The neutrophil to lymphocyte ratio (NLR) has been reported to be associated with clinical outcomes of patients with severe traumatic brain injury (TBI). This study aimed to evaluate the correlation between the dynamics of NLR and clinical outcomes of pediatric patients with moderate to severe TBI.

METHODS

We retrospectively evaluated the clinical data of a total of 374 pediatric patients with moder-ate to severe TBI who were treated in our department between May 2016 and May 2020. Clinical and laboratory data including the NLR upon admission and the NLR on hospital day four were collected. Poor clinical outcome was defined as Glasgow Outcome Scale (GOS) of 1-3. Multivariable logistic regression analyses were performed to investigate the correlation between the dynamics of NLR and clinical outcome.

RESULTS

Three hundred seventy-four pediatric patients (mean age 7.37 ± 3.11, 52.7% male) were evaluated. Based on the ROC curves, a value of 5 was determined as the NLR cut-off value. The corresponding cutoff value for delta NLR was 1. The Glasgow Coma Scale (GCS) (OR, 3.42; 95% CI: 1.88-5.28; P <0.001), the light reflex (OR, 1.79; 95% CI: 1.34- 2.84; P = 0.027), the Rotterdam CT score (OR, 2.71; 95% CI: 1.72-4.13; P = 0.021), and delta NLR (OR, 1.71; 95% CI: 1.13- 2.52; P = 0.034) were identified as independent predictors for unfavorable outcomes in multivariable logistic regression analysis.

CONCLUSIONS

The result of the present study suggest that delta NLR could be a predictor of poor clinical outcome of pediatrics with moderate to severe TBI. This cost-effective and easily available biomarker could be used to predict clinical outcomes in these patients.

CBF oscillations induced by trigeminal nerve stimulation protect the pericontusional penumbra in traumatic brain injury complicated by hemorrhagic shock

Traumatic peri-contusional penumbra represents crucial targets for therapeutic interventions after traumatic brain injury (TBI). Current resuscitative approaches may not adequately alleviate impaired cerebral microcirculation and, hence, compromise oxygen delivery to peri-contusional areas. Low-frequency oscillations in cerebral blood flow (CBF) may improve cerebral oxygenation in the setting of oxygen deprivation. However, no method has been reported to induce controllable oscillations in CBF and it hasn't been applied as a therapeutic strategy. Electrical stimulation of the trigeminal nerve (TNS) plays a pivotal role in modulating cerebrovascular tone and cerebral perfusion. We hypothesized that TNS can modulate CBF at the targeted frequency band via the trigemino-cerebrovascular network, and TNS-induced CBF oscillations would improve cerebral oxygenation in peri-contusional areas. In a rat model of TBI complicated by hemorrhagic shock, TNS-induced CBF oscillations conferred significant preservation of peri-contusional tissues leading to reduced lesion volume, attenuated hypoxic injury and neuroinflammation, increased eNOS expression, improved neurological recovery and better 10-day survival rate, despite not significantly increasing CBF as compared with those in immediate and delayed resuscitation animals. Our findings indicate that low-frequency CBF oscillations enhance cerebral oxygenation in peri-contusional areas, and play a more significant protective role than improvements in non-oscillatory cerebral perfusion or volume expansion alone.

Drosophila as a model to explore secondary injury cascades after traumatic brain injury

Drosophilae are emerging as a valuable model to study traumatic brain injury (TBI)-induced secondary injury cascades that drive persisting neuroinflammation and neurodegenerative pathology that imposes significant risk for long-term neurological deficits. As in mammals, TBI in Drosophila triggers axonal injury, metabolic crisis, oxidative stress, and a robust innate immune response. Subsequent neurodegeneration stresses quality control systems and perpetuates an environment for neuroprotection, regeneration, and delayed cell death via highly conserved cell signaling pathways. Fly injury models continue to be developed and validated for both whole-body and head-specific injury to isolate, evaluate, and modulate these parallel pathways. In conjunction with powerful genetic tools, the ability for longitudinal evaluation, and associated neurological deficits that can be tested with established behavioral tasks, Drosophilae are an attractive model to explore secondary injury cascades and therapeutic intervention after TBI. Here, we review similarities and differences between mammalian and fly pathophysiology and highlight strategies for their use in translational neurotrauma research.

Statins' Effect on Cognitive Outcome After Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI), also known as the "Silent Epidemic," is a growing devastating global health problem estimated to affect millions of individuals yearly worldwide with little public recognition, leading to many individuals living with a TBI-related disability. TBI has been associated with up to five times increase in the risk of dementia among multiple neurologic complications compared with the general population. Several therapies, including statins, have been tried and showed promising benefits for TBI patients. In this systematic review, we evaluated the recent literature that tested the role of statins on neurological and cognitive outcomes such as Alzheimer's Disease and non-Alzheimer's dementia in survivors of TBI with various severities. We conducted a systematic search on PubMed, PubMed Central, MEDLINE, and Google Scholar. MeSH terms and keywords were used to search for full-text randomized clinical trials (RCTs), cross-sectional, case-control, cohort studies, systematic reviews, and animal studies published in English. Inclusion and exclusion criteria were applied, and the articles were subjected to quality appraisal by two reviewers. Our data search retrieved 4948 nonduplicate records. A total of 18 studies were included - nine human studies, and nine animal laboratory trials - after meeting inclusion, eligibility, and quality assessment criteria. Simvastatin was the most tested statin, and the oral route of administration was the most used. Eight human studies showed a significant neuroprotective effect and improvement in the cognitive outcomes, including dementia. Four randomized clinical trials with 296 patients showed that statins play a neuroprotective role and improve cognitive outcomes through different mechanisms, especially their anti-inflammatory effect; they were shown to lower tumor necrosis factor (TNF)-α and C-reactive protein (CRP) levels. Also, they decreased axonal injury and cortical thickness changes. In addition, four cohort studies compared a total of 867.953 patients. One study showed a decrease in mortality in statin-treated patients (p=0.05). Another study showed a reduction in the incidence of Alzheimer's disease and related dementias (RR, 0.77; 95% CI, 0.73-0.81), while one study showed a decreased risk of dementia after concussions by 6.13% (p=0.001). On the other hand, one cohort study showed no significant difference with the use of statins. In eight animal trials, statins showed a significant neuroprotective effect, improved cognitive outcomes, and neurological functions. Different molecular and cellular mechanisms were suggested, including anti-inflammatory effects, promoting angiogenesis, neurogenesis, increasing cerebral blood flow, neurite outgrowth, promoting the proliferation and differentiation of neural stem cells, and reducing axonal injury. On the contrary, one study showed no benefit and actual adverse effect on the cognitive outcome. Most of the studies showed promising neuroprotective effects of statins in TBI patients. Cognitive outcomes, especially dementia, were improved. However, the optimal therapeutic protocol is still unknown. Thus, statins are candidates for more advanced studies to test their efficacy in preventing cognitive decline in patients with TBI.

A multiscale computational model of angiogenesis after traumatic brain injury, investigating the role location plays in volumetric recovery

Vascular endothelial growth factor (VEGF) is a key protein involved in the process of angiogenesis. VEGF is of particular interest after a traumatic brain injury (TBI), as it re-establishes the cerebral vascular network in effort to allow for proper cerebral blood flow and thereby oxygenation of damaged brain tissue. For this reason, angiogenesis is critical in the progression and recovery of TBI patients in the days and weeks post injury. Although well established experimental work has led to advances in our understanding of TBI and the progression of angiogenisis, many constraints still exist with existing methods, especially when considering patient progression in the days following injury. To better understand the healing process on the proposed time scales, we develop a computational model that quickly simulates vessel growth and recovery by coupling VEGF and its interactions with its associated receptors to a physiologically inspired fractal model of the microvascular re-growth. We use this model to clarify the role that diffusivity, receptor kinetics and location of the TBI play in overall blood volume restoration in the weeks post injury and show that proper therapeutic angiogenesis, or vasculogenic therapies, could speed recovery of the patient as a function of the location of injury.

Cerebral Blood Flow Deviations in Critically Ill Patients: Potential Insult Contributing to Ischemic and Hyperemic Injury

Background: Ischemic and hyperemic injury have emerged as biologic mechanisms that contribute to cognitive impairment in critically ill patients. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation.

Methods: We used transcranial Doppler to measure the proportion of time that CBF velocity (CBFv) deviated beyond previously reported ischemic and hyperemic thresholds in a cohort of critically ill patients with respiratory failure and/or shock within 48 h of ICU admission. We also assessed whether these CBFv deviations were more common during periods of impaired dynamic autoregulation, and whether they are explained by concurrent variations in mean arterial pressure (MAP) and end-tidal PCO₂ (PetCO₂).

Results: We enrolled 12 consecutive patients (three females) who were monitored for a mean duration of 462.6 ± 39.8 min. Across patients, CBFv deviated by more than 20–30% from its baseline for 17–24% of the analysis time. These CBFv deviations occurred equally during periods of preserved and impaired autoregulation, while concurrent variations in MAP and PetCO₂ explained only 13–21% of these CBFv deviations.

Conclusion: CBFv deviations beyond ischemic and hyperemic thresholds are common in critically ill patients with respiratory failure or shock. These deviations occur irrespective of the state of dynamic autoregulation and are not explained by changes in MAP and CO₂. Future studies should explore mechanisms responsible for these CBFv deviations and establish whether their cumulative burden predicts poor neurocognitive outcomes.

The Prehospital Evaluation and Care of Moderate/Severe TBI in the Austere Environment

Increased resource constraints secondary to a smaller medical footprint, prolonged evacuation times, or overwhelming casualty volumes all increase the challenges of effective management of traumatic brain injury (TBI) in the austere environment. Prehospital providers are responsible for the battlefield recognition and initial management of TBI. As such, targeted education is critical to efficient injury recognition, promoting both provider readiness and improved patient outcomes. When austere conditions limit or prevent definitive treatment, a comprehensive understanding of TBI pathophysiology can help inform acute care and enhance prevention of secondary brain injury. Field deployable, noninvasive TBI assessment and monitoring devices are urgently needed and are currently undergoing clinical evaluation. Evidence shows that the assessment, monitoring, and treatment in the first few hours and days after injury should focus on the preservation of cerebral perfusion and oxygenation. For cases where medical management is inadequate (eg, evidence of an enlarging intracranial hematoma), guidelines have been developed for the performance of cranial surgery by nonneurosurgeons. TBI management in the austere environment will continue to be a challenge, but research focused on improving evidence-based monitoring and therapeutic interventions can help to mitigate some of these challenges and improve patient outcomes.

Low-resolution pressure reactivity index and its derived optimal cerebral perfusion pressure in adult traumatic brain injury: a CENTER-TBI study

BACKGROUND

After traumatic brain injury (TBI), brain tissue can be further damaged when cerebral autoregulation is impaired. Managing cerebral perfusion pressure (CPP) according to computed "optimal CPP" values based on cerebrovascular reactivity indices might contribute to preventing such secondary injuries. In this study, we examined the discriminative value of a low-resolution long pressure reactivity index (LPRx) and its derived "optimal CPP" in comparison to the well-established high-resolution pressure reactivity index (PRx).

METHODS

Using the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study dataset, the association of LPRx (correlation between 1-min averages of intracranial pressure and arterial blood pressure over a moving time frame of 20 min) and PRx (correlation between 10-s averages of intracranial pressure and arterial blood pressure over a moving time frame of 5 min) to outcome was assessed and compared using univariate and multivariate regression analysis. "Optimal CPP" values were calculated using a multi-window algorithm that was based on either LPRx or PRx, and their discriminative ability was compared.

RESULTS

LPRx and PRx were both significant predictors of mortality in univariate and multivariate regression analysis, but PRx displayed a higher discriminative ability. Similarly, deviations of actual CPP from "optimal CPP" values calculated from each index were significantly associated with outcome in univariate and multivariate analysis. "Optimal CPP" based on PRx, however, trended towards more precise predictions.

CONCLUSIONS

LPRx and its derived "optimal CPP" which are based on low-resolution data were significantly associated with outcome after TBI. However, they did not reach the discriminative ability of the high-resolution PRx and its derived "optimal CPP." Nevertheless, LPRx might still be an interesting tool to assess cerebrovascular reactivity in centers without high-resolution signal monitoring.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02210221. First submitted July 29, 2014. First posted August 6, 2014.

Neuroimaging of traumatic brain injury in military personnel: An overview

BACKGROUND

The incidence of blunt-force traumatic brain injury (TBI) is especially prevalent in the military, where the emergency care admission rate has been reported to be 24.6-41.8 per 10,000 soldier-years. Given substantial advancements in modern neuroimaging techniques over the past decade in terms of structural, functional, and connectomic approaches, this mode of exploration can be viewed as best suited for understanding the underlying pathology and for providing proper intervention at effective time-points.

APPROACH

Here we survey neuroimaging studies of mild-to-severe TBI in military veterans with the intent to aid the field in the creation of a roadmap for clinicians and researchers whose aim is to understand TBI progression.

DISCUSSION

Recent advancements on the quantification of neurocognitive dysfunction, cellular dysfunction, intracranial pressure, cerebral blood flow, inflammation, post-traumatic neuropathophysiology, on blood serum biomarkers and on their correlation to neuroimaging findings are reviewed to hypothesize how they can be used in conjunction with one another. This may allow clinicians and scientists to comprehensively study TBI in military service members, leading to new treatment strategies for both currently-serving as well as veteran personnel, and to improve the study of TBI more broadly.

Pioglitazone Therapy and Fractures: Systematic Review and Meta- Analysis

INTRODUCTION

Thiazolidinediones are a group of synthetic medications used in type 2 diabetes treatment. Among available thiazolidinediones, pioglitazone is gaining increased attention due to its lower cardiovascular risk in type 2 diabetes mellitus sufferers and seems a promising future therapy. Accumulating evidence suggests that diabetic patients may exert bone fractures due to such treatments. Simultaneously, the female population is thought to be at greater risk. Still, the safety outcomes of pioglitazone treatment especially in terms of fractures are questionable and need to be clarified.

METHODS

We searched MEDLINE, Scopus, PsyInfo, eLIBRARY.ru electronic databases and clinical trial registries for studies reporting an association between pioglitazone and bone fractures in type 2 diabetes mellitus patients published before Feb 15, 2016. Among 1536 sources that were initially identified, six studies including 3172 patients proved relevant for further analysis.

RESULT

Pooled analysis of the included studies demonstrated that after treatment with pioglitazone patients with type 2 diabetes mellitus had no significant increase in fracture risk [odds ratio (OR): 1.18, 95% confidence interval (CI): 0.82 to 1.71, p=0.38] compared to other antidiabetic drugs or placebo. Additionally, no association was found between the risk of fractures and pioglitazone therapy duration. The gender of the patients involved was not relevant to the risk of fractures, too.

CONCLUSION

Pioglitazone treatment in diabetic patients does not increase the incidence of bone fractures. Moreover, there is no significant association between patients' fractures, their gender and the period of exposure to pioglitazone. Additional longitudinal studies need to be undertaken to obtain more detailed information on bone fragility and pioglitazone therapy.

The anti-anaphylactoid effects of hydroxysafflor yellow A on the suppression of mast cell Ca2+ influx and degranulation

BACKGROUND

Anaphylaxis is a type of potentially fatal hypersensitivity reaction resulting from the activation of mast cell mediators, especially histamine and lipid mediators. Non-IgE-mediated anaphylaxis can occur because of the direct activation of mast cells. Hydroxysafflor yellow A (HSYA) is the main chemical component of safflower (Carthamus tinctorius) and has been reported to have pharmacological activities. However, the anti-anaphylactoid effect of HSYA has not yet been investigated.

PURPOSE

The aims of this study were to evaluate the anti-anaphylactoid activity of HSYA in vivo and to investigate the underlying mechanism in vitro.

METHODS

The anti-anaphylactoid activity of HSYA was evaluated in a mouse model of hindpaw extravasation. Calcium imaging was used to assess intracellular Ca²⁺ mobilization. The levels of cytokines and chemokines released by stimulated mast cells were measured using enzyme immunoassay kits. Western blotting was used to explore the related molecular signaling pathways.

RESULTS

HSYA markedly inhibited mast cell degranulation by suppressing the activation of intracellular Ca²⁺ mobilization and preventing the release of cytokines and chemokines from mast cells in a dose-dependent manner via the PKC-PLCγ-IP3R signaling pathway.

CONCLUSION

In summary, HSYA has anti-anaphylactoid pharmacological activity, which makes it a potential candidate for the development of a novel agent to suppress drug-induced anaphylactoid reactions.

Vascular Abnormalities within Normal Appearing Tissue in Chronic Traumatic Brain Injury

Magnetic resonance imaging (MRI) is a powerful tool for visualizing traumatic brain injury(TBI)-related lesions. Trauma-induced encephalomalacia is frequently identified by its hyperintense appearance on fluid-attenuated inversion recovery (FLAIR) sequences. In addition to parenchymal lesions, TBI commonly results in cerebral microvascular injury, but its anatomical relationship to parenchymal encephalomalacia is not well characterized. The current study utilized a multi-modal MRI protocol to assess microstructural tissue integrity (by mean diffusivity [MD] and fractional aniosotropy [FA]) and altered vascular function (by cerebral blood flow [CBF] and cerebral vascular reactivity [CVR]) within regions of visible encephalomalacia and normal appearing tissue in 27 chronic TBI (minimum 6 months post-injury) subjects. Fifteen subjects had visible encephalomalacias whereas 12 did not have evident lesions on MRI. Imaging from 14 age-matched healthy volunteers were used as controls. CBF was assessed by arterial spin labeling (ASL) and CVR by measuring the change in blood-oxygen-level-dependent (BOLD) MRI during a hypercapnia challenge. There was a significant reduction in FA, CBF, and CVR with a complementary increase in MD within regions of FLAIR-visible encephalomalacia (p < 0.05 for all comparisons). In normal-appearing brain regions, only CVR was significantly reduced relative to controls (p < 0.05). These findings indicate that vascular dysfunction represents a TBI endophenotype that is distinct from structural injury detected using conventional MRI, may be present even in the absence of visible structural injury, and persists long after trauma. CVR may serve as a useful diagnostic and pharmacodynamic imaging biomarker of traumatic microvascular injury.

Neutrophils in traumatic brain injury (TBI): friend or foe?

Our knowledge of the pathophysiology about traumatic brain injury (TBI) is still limited. Neutrophils, as the most abundant leukocytes in circulation and the first-line transmigrated immune cells at the sites of injury, are highly involved in the initiation, development, and recovery of TBI. Nonetheless, our understanding about neutrophils in TBI is obsolete, and mounting evidences from recent studies have challenged the conventional views. This review summarizes what is known about the relationships between neutrophils and pathophysiology of TBI. In addition, discussions are made on the complex roles as well as the controversial views of neutrophils in TBI.

Thermoregulation in brain injury

Different mechanisms explain thermoregulatory dysfunction following ischemic stroke, hemorrhagic stroke, and traumatic brain injury. Temperature instability following brain injury likely involves hypothalamic injury, pathologic changes in cerebral blood flow, metabolic derangement, and a neurogenic inflammatory response. Although targeted temperature management (TTM) exerts pleiotropic effects, the heterogeneity of brain injury has hindered identification of patient subsets most likely to benefit from TTM. Early optimism about TTM's role in brain injury has been tempered by the failure of successive clinical trials to show improved patient outcomes. However, given the deleterious effects of fever, aggressive fever management is still warranted in the critically ill neurologic patient.

Chronic global analysis of vascular permeability and cerebral blood flow after bone marrow stromal cell treatment of traumatic brain injury in the rat: A long-term MRI study

Vascular permeability and hemodynamic alteration in response to the transplantation of human bone marrow stromal cells (hMSCs) after traumatic brain injury (TBI) were longitudinally investigated in non directly injured and normal-appearing cerebral tissue using magnetic resonance imaging (MRI). Male Wistar rats (300-350g, n=30) subjected to controlled cortical impact TBI were intravenously injected with 1ml of saline (at 6-h or 1-week post-injury, n=5/group) or with hMSCs in suspension (∼3×10⁶ hMSCs, at 6-h or 1-week post-injury, n=10/group). MRI measurements of T2-weighted imaging, cerebral blood flow (CBF) and blood-to-brain transfer constant (Ki) of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA), and neurological behavioral estimates were performed on all animals at multiple time points up to 3-months post-injury. Our long-term imaging data show that blood-brain barrier (BBB) breakdown and hemodynamic disruption after TBI, as revealed by Ki and CBF, respectively, affect both hemispheres of the brain in a diffuse manner. Our data reveal a sensitive vascular permeability and hemodynamic reaction in response to the time-dependent transplantation of hMSCs. A more rapid reduction of Ki following cell treatment is associated with a higher level of CBF in the injured brain, and acute (6h) cell administration leads to enhanced therapeutic effects on both the recovery of vascular integrity and stabilization of cerebral perfusion compared to delayed (1w) cell engraftment. Our results indicate that cell-enhanced BBB reconstitution plays an important role in underlying the restoration of CBF in the injured brain, which in turn, contributes to the improvement of functional outcome.

Glibenclamide pretreatment protects against chronic memory dysfunction and glial activation in rat cranial blast traumatic brain injury

Blast traumatic brain injury (bTBI) affects both military and civilian populations, and often results in chronic deficits in cognition and memory. Chronic glial activation after bTBI has been linked with cognitive decline. Pharmacological inhibition of sulfonylurea receptor 1 (SUR1) with glibenclamide was shown previously to reduce glial activation and improve cognition in contusive models of CNS trauma, but has not been examined in bTBI. We postulated that glibenclamide would reduce chronic glial activation and improve long-term memory function after bTBI. Using a rat direct cranial model of bTBI (dc-bTBI), we evaluated the efficacy of two glibenclamide treatment paradigms: glibenclamide prophylaxis (pre-treatment), and treatment with glibenclamide starting after dc-bTBI (post-treatment). Our results show that dc-bTBI caused hippocampal astrocyte and microglial/macrophage activation that was associated with hippocampal memory dysfunction (rapid place learning paradigm) at 28days, and that glibenclamide pre-treatment, but not post-treatment, effectively protected against glial activation and memory dysfunction. We also report that a brief transient time-window of blood-brain barrier (BBB) disruption occurs after dc-bTBI, and we speculate that glibenclamide, which is mostly protein bound and does not normally traverse the intact BBB, can undergo CNS delivery only during this brief transient opening of the BBB. Together, our findings indicate that prophylactic glibenclamide treatment may help to protect against chronic cognitive sequelae of bTBI in warfighters and other at-risk populations.

Endocannabinoids: A Promising Impact for Traumatic Brain Injury

The endogenous cannabinoid (endocannabinoid) system regulates a diverse array of physiological processes and unsurprisingly possesses considerable potential targets for the potential treatment of numerous disease states, including two receptors (i.e., CB1 and CB2 receptors) and enzymes regulating their endogenous ligands N-arachidonoylethanolamine (anandamide) and 2-arachidonyl glycerol (2-AG). Increases in brain levels of endocannabinoids to pathogenic events suggest this system plays a role in compensatory repair mechanisms. Traumatic brain injury (TBI) pathology remains mostly refractory to currently available drugs, perhaps due to its heterogeneous nature in etiology, clinical presentation, and severity. Here, we review pre-clinical studies assessing the therapeutic potential of cannabinoids and manipulations of the endocannabinoid system to ameliorate TBI pathology. Specifically, manipulations of endocannabinoid degradative enzymes (e.g., fatty acid amide hydrolase, monoacylglycerol lipase, and α/β-hydrolase domain-6), CB1 and CB2 receptors, and their endogenous ligands have shown promise in modulating cellular and molecular hallmarks of TBI pathology such as; cell death, excitotoxicity, neuroinflammation, cerebrovascular breakdown, and cell structure and remodeling. TBI-induced behavioral deficits, such as learning and memory, neurological motor impairments, post-traumatic convulsions or seizures, and anxiety also respond to manipulations of the endocannabinoid system. As such, the endocannabinoid system possesses potential drugable receptor and enzyme targets for the treatment of diverse TBI pathology. Yet, full characterization of TBI-induced changes in endocannabinoid ligands, enzymes, and receptor populations will be important to understand that role this system plays in TBI pathology. Promising classes of compounds, such as the plant-derived phytocannabinoids, synthetic cannabinoids, and endocannabinoids, as well as their non-cannabinoid receptor targets, such as TRPV1 receptors, represent important areas of basic research and potential therapeutic interest to treat TBI.

Evaluating the Role of Reduced Oxygen Saturation and Vascular Damage in Traumatic Brain Injury Using Magnetic Resonance Perfusion-Weighted Imaging and Susceptibility-Weighted Imaging and Mapping

The cerebral vasculature, along with neurons and axons, is vulnerable to biomechanical insult during traumatic brain injury (TBI). Trauma-induced vascular injury is still an underinvestigated area in TBI research. Cerebral blood flow and metabolism could be important future treatment targets in neural critical care. Magnetic resonance imaging offers a number of key methods to probe vascular injury and its relationship with traumatic hemorrhage, perfusion deficits, venous blood oxygen saturation changes, and resultant tissue damage. They make it possible to image the hemodynamics of the brain, monitor regional damage, and potentially show changes induced in the brain's function not only acutely but also longitudinally following treatment. These methods have recently been used to show that even mild TBI (mTBI) subjects can have vascular abnormalities, and thus they provide a major step forward in better diagnosing mTBI patients.

Regulation of the cerebral circulation: bedside assessment and clinical implications

Regulation of the cerebral circulation relies on the complex interplay between cardiovascular, respiratory, and neural physiology. In health, these physiologic systems act to maintain an adequate cerebral blood flow (CBF) through modulation of hydrodynamic parameters; the resistance of cerebral vessels, and the arterial, intracranial, and venous pressures. In critical illness, however, one or more of these parameters can be compromised, raising the possibility of disturbed CBF regulation and its pathophysiologic sequelae. Rigorous assessment of the cerebral circulation requires not only measuring CBF and its hydrodynamic determinants but also assessing the stability of CBF in response to changes in arterial pressure (cerebral autoregulation), the reactivity of CBF to a vasodilator (carbon dioxide reactivity, for example), and the dynamic regulation of arterial pressure (baroreceptor sensitivity). Ideally, cerebral circulation monitors in critical care should be continuous, physically robust, allow for both regional and global CBF assessment, and be conducive to application at the bedside. Regulation of the cerebral circulation is impaired not only in primary neurologic conditions that affect the vasculature such as subarachnoid haemorrhage and stroke, but also in conditions that affect the regulation of intracranial pressure (such as traumatic brain injury and hydrocephalus) or arterial blood pressure (sepsis or cardiac dysfunction). Importantly, this impairment is often associated with poor patient outcome. At present, assessment of the cerebral circulation is primarily used as a research tool to elucidate pathophysiology or prognosis. However, when combined with other physiologic signals and online analytical techniques, cerebral circulation monitoring has the appealing potential to not only prognosticate patients, but also direct critical care management.

Traumatic brain injury: pathophysiology for neurocritical care

Severe cases of traumatic brain injury (TBI) require neurocritical care, the goal being to stabilize hemodynamics and systemic oxygenation to prevent secondary brain injury. It is reported that approximately 45 % of dysoxygenation episodes during critical care have both extracranial and intracranial causes, such as intracranial hypertension and brain edema. For this reason, neurocritical care is incomplete if it only focuses on prevention of increased intracranial pressure (ICP) or decreased cerebral perfusion pressure (CPP). Arterial hypotension is a major risk factor for secondary brain injury, but hypertension with a loss of autoregulation response or excess hyperventilation to reduce ICP can also result in a critical condition in the brain and is associated with a poor outcome after TBI. Moreover, brain injury itself stimulates systemic inflammation, leading to increased permeability of the blood–brain barrier, exacerbated by secondary brain injury and resulting in increased ICP. Indeed, systemic inflammatory response syndrome after TBI reflects the extent of tissue damage at onset and predicts further tissue disruption, producing a worsening clinical condition and ultimately a poor outcome.

Elevation of blood catecholamine levels after severe brain damage has been reported to contribute to the regulation of the cytokine network, but this phenomenon is a systemic protective response against systemic insults. Catecholamines are directly involved in the regulation of cytokines, and elevated levels appear to influence the immune system during stress. Medical complications are the leading cause of late morbidity and mortality in many types of brain damage. Neurocritical care after severe TBI has therefore been refined to focus not only on secondary brain injury but also on systemic organ damage after excitation of sympathetic nerves following a stress reaction.

The Formation of Microthrombi in Parenchymal Microvessels after Traumatic Brain Injury Is Independent of Coagulation Factor XI

Microthrombus formation and bleeding worsen the outcome after traumatic brain injury (TBI). The aim of the current study was to characterize these processes in the brain parenchyma after experimental TBI and to determine the involvement of coagulation factor XI (FXI). C57BL/6 mice (n = 101) and FXI-deficient mice (n = 15) were subjected to controlled cortical impact (CCI). Wild-type mice received an inhibitory antibody against FXI (14E11) or control immunoglobulin G 24 h before or 30 or 120 min after CCI. Cerebral microcirculation was visualized in vivo by 2-photon microscopy 2-3 h post-trauma and histopathological outcome was assessed after 24 h. TBI induced hemorrhage and microthrombus formation in the brain parenchyma (p < 0.001). Inhibition of FXI activation or FXI deficiency did not reduce cerebral thrombogenesis, lesion volume, or hemispheric swelling. However, it also did not increase intracranial hemorrhage. Formation of microthrombosis in the brain parenchyma after TBI is independent of the intrinsic coagulation cascade since it was not reduced by inhibition of FXI. However, since targeting FXI has well-established antithrombotic effects in humans and experimental animals, inhibition of FXI could represent a reasonable strategy for the prevention of deep venous thrombosis in immobilized patients with TBI.

A semi-automated workflow solution for multimodal neuroimaging: application to patients with traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity, placing a significant financial burden on the healthcare system worldwide. Non-invasive neuroimaging technologies have been playing a pivotal role in the study of TBI, providing important information for surgical planning and patient management. Advances in understanding the basic mechanisms and pathophysiology of the brain following TBI are hindered by a lack of reliable image analysis methods for accurate quantitative assessment of TBI-induced structural and pathophysiological changes seen on anatomical and functional images obtained from multiple imaging modalities. Conventional region-of-interest (ROI) analysis based on manual labeling of brain regions is time-consuming and the results could be inconsistent within and among investigators. In this study, we propose a workflow solution framework that combined the use of non-linear spatial normalization of structural brain images and template-based anatomical labeling to automate the ROI analysis process. The proposed workflow solution is applied to dynamic PET scanning with 15O-water (0-10 min) and 18F-FDDNP (0-6 min) for measuring cerebral blood flow in patients with TBI.

Should the neurointensive care management of traumatic brain injury patients be individualized according to autoregulation status and injury subtype?

INTRODUCTION

The status of autoregulation is an important prognostic factor in traumatic brain injury (TBI), and is important to consider in the management of TBI patients. Pressure reactivity index (PRx) is a measure of autoregulation that has been thoroughly studied, but little is known about its variation in different subtypes of TBI. In this study, we examined the impact of PRx and cerebral perfusion pressure (CPP) on outcome in different TBI subtypes.

METHODS

107 patients were retrospectively studied. Data on PRx, CPP, and outcome were collected from our database. The first CT scan was classified according to the Marshall classification system. Patients were assigned to "diffuse" (Marshall class: diffuse-1, diffuse-2, and diffuse-3) or "focal" (Marshall class: diffuse-4, evacuated mass lesion, and non-evacuated mass lesion) groups. 2 × 2 tables were constructed calculating the proportions of favorable/unfavorable outcome at different combinations of PRx and CPP.

RESULTS

Low PRx was significantly associated with favorable outcome in the combined group (p = 0.002) and the diffuse group (p = 0.04), but not in the focal group (p = 0.06). In the focal group higher CPP values were associated with worse outcome (p = 0.02). In diffuse injury patients with disturbed autoregulation (PRx >0.1), CPP >70 mmHg was associated with better outcome (p = 0.03).

CONCLUSION

TBI patients with diffuse injury may differ from those with mass lesions. In the latter higher levels of CPP may be harmful, possibly due to BBB disruption. In TBI patients with diffuse injury and disturbed autoregulation higher levels of CPP may be beneficial.

Accuracy of brain multimodal monitoring to detect cerebral hypoperfusion after traumatic brain injury*

OBJECTIVE

To examine the accuracy of brain multimodal monitoring-consisting of intracranial pressure, brain tissue PO2, and cerebral microdialysis--in detecting cerebral hypoperfusion in patients with severe traumatic brain injury.

DESIGN

Prospective single-center study.

PATIENTS

Patients with severe traumatic brain injury.

SETTING

Medico-surgical ICU, university hospital.

INTERVENTION

Intracranial pressure, brain tissue PO2, and cerebral microdialysis monitoring (right frontal lobe, apparently normal tissue) combined with cerebral blood flow measurements using perfusion CT.

MEASUREMENTS AND MAIN RESULTS

Cerebral blood flow was measured using perfusion CT in tissue area around intracranial monitoring (regional cerebral blood flow) and in bilateral supra-ventricular brain areas (global cerebral blood flow) and was matched to cerebral physiologic variables. The accuracy of intracranial monitoring to predict cerebral hypoperfusion (defined as an oligemic regional cerebral blood flow < 35 mL/100 g/min) was examined using area under the receiver-operating characteristic curves. Thirty perfusion CT scans (median, 27 hr [interquartile range, 20-45] after traumatic brain injury) were performed on 27 patients (age, 39 yr [24-54 yr]; Glasgow Coma Scale, 7 [6-8]; 24/27 [89%] with diffuse injury). Regional cerebral blood flow correlated significantly with global cerebral blood flow (Pearson r = 0.70, p < 0.01). Compared with normal regional cerebral blood flow (n = 16), low regional cerebral blood flow (n = 14) measurements had a higher proportion of samples with intracranial pressure more than 20 mm Hg (13% vs 30%), brain tissue PO2 less than 20 mm Hg (9% vs 20%), cerebral microdialysis glucose less than 1 mmol/L (22% vs 57%), and lactate/pyruvate ratio more than 40 (4% vs 14%; all p < 0.05). Compared with intracranial pressure monitoring alone (area under the receiver-operating characteristic curve, 0.74 [95% CI, 0.61-0.87]), monitoring intracranial pressure + brain tissue PO2 (area under the receiver-operating characteristic curve, 0.84 [0.74-0.93]) or intracranial pressure + brain tissue PO2+ cerebral microdialysis (area under the receiver-operating characteristic curve, 0.88 [0.79-0.96]) was significantly more accurate in predicting low regional cerebral blood flow (both p < 0.05).

CONCLUSION

Brain multimodal monitoring-including intracranial pressure, brain tissue PO2, and cerebral microdialysis--is more accurate than intracranial pressure monitoring alone in detecting cerebral hypoperfusion at the bedside in patients with severe traumatic brain injury and predominantly diffuse injury.

Cerebral hemodynamic changes of mild traumatic brain injury at the acute stage

Mild traumatic brain injury (mTBI) is a significant public health care burden in the United States. However, we lack a detailed understanding of the pathophysiology following mTBI and its relation to symptoms and recovery. With advanced magnetic resonance imaging (MRI), we can investigate brain perfusion and oxygenation in regions known to be implicated in symptoms, including cortical gray matter and subcortical structures. In this study, we assessed 14 mTBI patients and 18 controls with susceptibility weighted imaging and mapping (SWIM) for blood oxygenation quantification. In addition to SWIM, 7 patients and 12 controls had cerebral perfusion measured with arterial spin labeling (ASL). We found increases in regional cerebral blood flow (CBF) in the left striatum, and in frontal and occipital lobes in patients as compared to controls (p = 0.01, 0.03, 0.03 respectively). We also found decreases in venous susceptibility, indicating increases in venous oxygenation, in the left thalamostriate vein and right basal vein of Rosenthal (p = 0.04 in both). mTBI patients had significantly lower delayed recall scores on the standardized assessment of concussion, but neither susceptibility nor CBF measures were found to correlate with symptoms as assessed by neuropsychological testing. The increased CBF combined with increased venous oxygenation suggests an increase in cerebral blood flow that exceeds the oxygen demand of the tissue, in contrast to the regional hypoxia seen in more severe TBI. This may represent a neuroprotective response following mTBI, which warrants further investigation.

Targeting the neurovascular unit in brain trauma

Although the neurovascular unit was originally developed as a conceptual framework for stroke, it is now recognized that these cell-cell interactions play critical roles in many other CNS disorders as well. In brain trauma, perturbations within the neurovascular unit may be especially important. Changes in neurovascular coupling may disrupt blood flow and metabolic regulation. Disruption of transmitter release-reuptake kinetics in neurons and astrocytes may augment excitotoxicity. Alterations in gliovascular signaling may underlie blood-brain barrier disruptions and traumatic edema. Perturbations in cell-cell signaling between all neuronal, glial, and vascular compartments may increase susceptibility to cell death. Finally, repairing the brain after trauma requires the integrated restoration of all neural, glial, and vascular connectivity for effective functional recovery. Just as in stroke, saving neurons alone may also be insufficient for treating brain trauma. In this minireview, we attempt to briefly highlight some of these pathways to underscore the importance of rescuing the entire neurovascular unit in brain trauma.

Quantitative lobar cerebral blood flow for outcome prediction after traumatic brain injury

The aim of this study was to examine cortical cerebral blood flow (CBF) in patients with traumatic brain injury (TBI) and determine whether lobar cortical CBF is a better predictor of long-term neurological outcome assessed by the Glasgow Outcome Scale (GOS) than global cortical CBF. Ninety-eight patients with TBI had a stable xenon computed tomography scan (Xe/CT-CBF study) performed at various time points after their initial injury. Spearman's correlation coefficients and Kruskall-Wallis' test were used to examine the relationship between patient age, emergency room Glasgow Coma Scale (GCS), Injury Severity Score, prehospital hypotension, prehospital hypoxia, mechanism of injury, type of injury, side of injury, global average CBF, lobar CBF, number of lobes with CBF below normal, and GOS (discharge, 3 and 6 months). Univariate ordinal regression was performed using these same variables and in combination with principle component analysis (PCA) to determine independent variables for multi-variate ordinal regression. Significant correlation between age, GCS, prehospital hypotension, type of injury, global average CBF, lobar CBF, number of lobes below normal CBF, and GOS was found. Individual lobar CBF was highly correlated with global CBF and the number of lobes below normal CBF. PCA found one principle component among these three CBF variables; therefore, average global CBF and number of lobes with CBF below normal were each chosen as independent variables for multiple ordinal regression, which found age, GCS, and prehospital hypotension, global average CBF, and number of lobes below normal CBF significantly associated with GOS. This study found global average CBF and lobar CBF significantly correlated with GOS at follow-up. There was, however, no individual cerebral lobe that was more predictive than any other, which puts into question the value of calculating lobar CBF versus global CBF in predicting GOS.

Imaging of cerebral blood flow in patients with severe traumatic brain injury in the neurointensive care

Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI.

Neurotraumatology

Neurotraumatology has its roots in ancient history, but its modern foundations are the physical examination, imaging to localize the pathology, and thoughtful medical and surgical decision making. The neurobiology of cranial and spinal injury is similar, with the main goal of therapies being to limit secondary injury. Brain injury treatment focuses on minimizing parenchymal swelling within the confined cranial vault. Spine injury treatment has the additional consideration of spinal coumn stability. Current guidelines for non-operative and operative management are reviewed in this chapter.

Posttraumatic refractory intracranial hypertension and brain herniation syndrome: cerebral hemodynamic assessment before decompressive craniectomy

Background. The pathophysiology of traumatic brain swelling remains little understood. An improved understanding of intracranial circulatory process related to brain herniation may have treatment implications. Objective. To investigate the cerebral hemodynamic changes associated with brain herniation syndrome due to traumatic brain swelling. Methods. Nineteen head-injured patients with evidence of refractory intracranial hypertension and transtentorial herniation were prospectively studied. Cerebral hemodynamic assessment by transcranial Doppler (TCD) ultrasonography was performed prior to decompressive craniectomy. Patients and their cerebral hemispheres were classified according to TCD-hemodynamic patterns, and the data correlated with neurological status, midline shift on CT scan, and Glasgow outcome scale scores at 6 months after injury. Results. A wide variety of cerebral hemodynamic findings were observed. Ten patients (52.7%) presented with cerebral oligoemia, 3 patients (15.8%) with cerebral hyperemia, and 6 patients with nonspecific circulatory pattern. Circulatory disturbances were more frequently found in the side of maximal cerebral swelling than in the opposite side. Pulsatility index (PI) values suggested that ICP varied from acceptable to considerably high; patients with increased PI, indicating higher microvascular resistance. No correlation was found between cerebral hemodynamic findings and outcome. Conclusions. There is a marked heterogeneity of cerebral hemodynamic disturbances among patients with brain herniation syndrome.

Cerebral blood flow changes after brain injury in human amyloid-beta knock-in mice

Traumatic brain injury (TBI) is an environmental risk factor for Alzheimer's disease (AD). Increased brain concentrations of amyloid-β (Aβ) peptides and impaired cerebral blood flow (CBF) are shared pathologic features of TBI and AD and promising therapeutic targets. We used arterial spin-labeling magnetic resonance imaging to examine if CBF changes after TBI are influenced by human Aβ and amenable to simvastatin therapy. CBF was measured 3 days and 3 weeks after controlled cortical impact (CCI) injury in transgenic human Aβ-expressing APP(NLh/NLh) mice compared to murine Aβ-expressing C57Bl/6J wild types. Compared to uninjured littermates, CBF was reduced in the cortex of the injured hemisphere in both Aβ transgenics and wild types; deficits were more pronounced in the transgenic group, which exhibited injury-induced increased concentrations of human Aβ. In the hemisphere contralateral to CCI, CBF levels were stable in Aβ transgenic mice but increased in wild-type mice, both relative to uninjured littermates. Post-injury treatment of Aβ transgenic mice with simvastatin lowered brain Aβ concentrations, attenuated deficits in CBF ipsilateral to injury, restored hyperemia contralateral to injury, and reduced brain tissue loss. Future studies examining long-term effects of simvastatin therapy on CBF and chronic neurodegenerative changes after TBI are warranted.

Alterations in cerebral oxygen metabolism after traumatic brain injury in children

Traumatic brain injury (TBI) is the most common cause of acquired disability in children. Metabolic defects, and in particular mitochondrial dysfunction, are important contributors to brain injury after TBI. Studies of metabolic dysfunction are limited, but magnetic resonance methods suitable for use in children are overcoming this limitation. We performed noninvasive measurements of cerebral blood flow and oxygen metabolic index (OMI) to assess metabolic dysfunction in children with severe TBI. Cerebral blood flow is variable after TBI but hypoperfusion and low OMI are predominant, supporting metabolic dysfunction. This finding is consistent with preclinical and adult clinical studies of brain metabolism and mitochondrial dysfunction after TBI.

Outcome prediction within twelve hours after severe traumatic brain injury by quantitative cerebral blood flow

We measured quantitative cortical mantle cerebral blood flow (CBF) by stable xenon computed tomography (CT) within the first 12 h after severe traumatic brain injury (TBI) to determine whether neurologic outcome can be predicted by CBF stratification early after injury. Stable xenon CT was used for quantitative measurement of CBF (mL/100 g/min) in 22 cortical mantle regions stratified as follows: low (0-8), intermediate (9-30), normal (31-70), and hyperemic (>70) in 120 patients suffering severe (Glasgow Coma Scale [GCS] score ≤8) TBI. For each of these CBF strata, percentages of total cortical mantle volume were calculated. Outcomes were assessed by Glasgow Outcome Scale (GOS) score at discharge (DC), and 1, 3, and 6 months after discharge. Quantitative cortical mantle CBF differentiated GOS 1 and GOS 2 (dead or vegetative state) from GOS 3-5 (severely disabled to good recovery; p<0.001). Receiver operating characteristic (ROC) curve analysis for percent total normal plus hyperemic flow volume (TNHV) predicting GOS 3-5 outcome at 6 months for CBF measured <6 and <12 h after injury showed ROC area under the curve (AUC) cut-scores of 0.92 and 0.77, respectively. In multivariate analysis, percent TNHV is an independent predictor of GOS 3-5, with an odds ratio of 1.460 per 10 percentage point increase, as is initial GCS score (OR=1.090). The binary version of the Marshall CT score was an independent predictor of 6-month outcome, whereas age was not. These results suggest that quantitative cerebral cortical CBF measured within the first 6 and 12 h after TBI predicts 6-month outcome, which may be useful in guiding patient care and identifying patients for randomized clinical trials. A larger multicenter randomized clinical trial is indicated.

Predictors and incidence of posttraumatic seizures in children and adolescents after brain injury

The present study evaluates the incidence of early and late seizures after head injury in patients under 18 years old. Factors correlating with a high risk of developing posttraumatic seizures were identified. Such risk factors were the severity of the head trauma and a Glasgow Coma Scale of 3-8. In contrast to many studies, we observed that the incidence of posttraumatic seizures was significantly higher in patients older than 12 years old (12-16 and 12-18). Most of the late seizures were paroxysmal electroencephalography (EEG) discharges diagnosed on a snapshot-EEG during the follow-up examination of the patients without clinical symptoms. We suppose that EEG-examination in head injured children is important to identify patients with epileptic potentials without clinical symptoms. Epileptic patterns of the EEG could worsen the diagnosis and clinical outcome of the children in accordance to studies performed in the adult population.

Reviewing the reliability, effectiveness and applications of Licox in traumatic brain injury

AIMS AND OBJECTIVES

To review the pathophysiology, accuracy, effectiveness and use of Licox for brain tissue oxygen monitoring in traumatic brain injury (TBI).

BACKGROUND

The Licox monitoring system allows continuous monitoring of partial pressure of brain tissue oxygen (PbO(2)), brain tissue temperature and intracranial pressure (ICP). The application and effectiveness of the use of Licox in TBI is not clearly explored within the literature.

INCLUSION CRITERIA

A date limit of 1995-2009, English language, all animal and human studies and the following terms were searched: Licox, brain tissue oxygenation, cerebral oxygenation and TBI. MEDLINE database was the primary data source.

EXCLUSION CRITERIA

All paediatric papers were excluded from the search. Studies not related to pathophysiology and management of TBI and brain tissue oximetry in adults were excluded. Data relevant to the subject under consideration were extracted by three independent clinicians to form a narrative report. Studies were critically evaluated using the NHS Public Health Resource Unit's checklist for each study analysed.

CONCLUSIONS

Licox offers new insights into cerebral pathology and physiology. The continuous bedside monitoring provides real-time data that can be used to improve patient management and prognosis in specialist units by trained and experienced staff. More research is required to understand the limitations of this technology and why it is not in widespread use. RELEVENCE TO CLINICAL PRACTICE: A clinical tool that could be utilized more often in the right setting to improve care to patients suffering from TBI by disseminating more information on this unique tool.

Depression of whole-brain oxygen extraction fraction is associated with poor outcome in pediatric traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a leading cause of death and disability in children. Metabolic failure is an integral component of the pathological aftermath of TBI. The oxygen extraction fraction (OEF) is a valuable parameter for characterization and description of metabolic abnormalities; however, OEF measurement has required either invasive procedures or the use of ionizing radiation, which significantly limits its use in pediatric research.

RESULTS

Patients with TBI had depressed OEF levels that correlated with the severity of injury. In addition, the OEF measured within 2 weeks of injury was predictive of patient outcome at 3 mo after injury. In pediatric TBI patients, low OEF-a marker of metabolic dysfunction-correlates with the severity of injury and outcome.

DISCUSSION

Our findings support previous literature on the role of metabolic dysfunction after TBI.

METHODS

Using a recently developed magnetic resonance (MR) technique for the measurement of oxygen saturation, we determined the whole-brain OEF in both pediatric TBI patients and in healthy controls. Injury and outcome were classified using pediatric versions of the Glasgow Coma Scale (GCS) and Glasgow Outcome Scale-Extended (GOS-E), respectively.