Cerebral perfusion and blood-brain barrier assessment in brain trauma using contrast-enhanced near-infrared spectroscopy with indocyanine green: A review

The effects of real vs simulated high altitude on associative memory for emotional stimuli

INTRODUCTION

This study aimed to investigate the effects of normobaric hypoxia (NH) and hypobaric hypoxia (HH) on associative memory performance for emotionally valenced stimuli.

METHODS

Two experiments were conducted. In Study 1, n=18 undergraduates performed an associative memory task under three NH conditions (FiO2= 20.9%, 15.1%, 13.6%) using a tent with a hypoxic generator. In Study 2, n=20 participants were assessed in a field study at various altitudes on the Himalayan mountains, including the Pyramid Laboratory (5,000 meters above sea level), using functional Near-Infrared Spectroscopy (fNIRS) and behavioral assessments.

RESULTS

Study 1 revealed no significant differences in recognition accuracy across NH conditions. However, Study 2 showed a complex relationship between altitude and memory for emotionally valenced stimuli. At lower altitudes, participants more accurately recognized emotional stimuli compared to neutral ones, a trend that reversed at higher altitudes. Brain oxygenation varied with altitude, indicating adaptive cognitive processing, as revealed by fNIRS measurements.

CONCLUSIONS

These findings suggest that hypoxia affects associative memory and emotional processing in an altitude-dependent manner, highlighting adaptive cognitive mechanisms. Understanding the effects of hypobaric hypoxia on cognition and memory can help develop strategies to mitigate its impact in high-altitude and hypoxic environments.

Application of preoperative three-dimensional reconstruction combined with fluorescence imaging in simultaneous bilateral single-port thoracoscopic anatomical pneumonectomy

We report a clinical case of preoperative three-dimensional reconstruction combined with fluorescence imaging in simultaneous bilateral single-hole thoracoscopic treatment of pulmonary nodules. Fluorescent staining is widely used in clinics to show the interface between lung segments, and there are many reports in the literature. Indocyanine green (ICG), fluorescent staining method has the advantages of no need for repeated lung inflation and short time consumption. Moreover, the development of imaging three-dimensional reconstruction technology also provides convenience for accurate positioning of anatomical structures. Finally, we think that the application of preoperative three-dimensional reconstruction combined with fluorescence imaging for simultaneous double-lung single-hole thoracoscopic pneumonectomy can quickly and clearly display the interface between lung segments, provide technical support for the operation, shorten the operation time, reduce intraoperative bleeding, and have relatively high safety, and may shorten the learning curve for the growth of clinical thoracic surgeons, which may be worth popularizing and applying.

Impact of the severity of brain injury on secondary adrenal insufficiency in traumatic brain injury patients and the influence of HPA axis dysfunction on prognosis

OBJECTIVE

To investigate secondary adrenal insufficiency post varying traumatic brain injuries' and its impact on prognosis.

METHODS

120 traumatic brain injury patients were categorized into mild, moderate and severe groups based on Glasgow Coma Scale. Adrenal function was evaluated through testing.

RESULTS

Secondary adrenal insufficiency rates were 0% (mild), 22.85% (moderate) and 44.82% (severe). Hypothalamus-pituitary-adrenal axis dysfunction rates were 14.81% (mild), 42.85% (moderate) and 63.79% (severe). Differences among groups were significant (p < .05). Patients with intact hypothalamus-pituitary-adrenal axis had shorter hospital stays and higher Glasgow Coma Scale scores. Receiver operating characteristic analysis of 24-h urinary free cortisol showed an area of 0.846, with a 17.62 μg/24h cutoff, 98.32% sensitivity and 52.37% specificity. In the low-dose adrenocorticotropic hormone test, with an 18 μg/dL cutoff, the receiver operating characteristic area was 0.546, with 46.28% sensitivity and 89.39% specificity.

CONCLUSION

As traumatic brain injury severity increases, secondary adrenal insufficiency incidence rises. The low-dose adrenocorticotropic hormone test is promising for hypothalamus-pituitary-adrenal axis evaluation. Patients with hypothalamus-pituitary-adrenal dysfunction experience prolonged hospitalization and worse prognosis.

Use and Effectiveness of Electrosuit in Neurological Disorders: A Systematic Review with Clinical Implications

Electrical stimulation through surface electrodes is a non-invasive therapeutic technique used to improve voluntary motor control and reduce pain and spasticity in patients with central nervous system injuries. The Exopulse Mollii Suit (EMS) is a non-invasive full-body suit with integrated electrodes designed for self-administered electrical stimulation to reduce spasticity and promote flexibility. The EMS has been evaluated in several clinical trials with positive findings, indicating its potential in rehabilitation. This review investigates the effectiveness of the EMS for rehabilitation and its acceptability by patients. The literature was collected through several databases following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Positive effects of the garment on improving motor functions and reducing spasticity have been shown to be related to the duration of the administration period and to the dosage of the treatment, which, in turn, depend on the individual's condition and the treatment goals. Moreover, patients reported wellbeing during stimulation and a muscle-relaxing effect on the affected limb. Although additional research is required to determine the efficacy of this device, the reviewed literature highlights the EMS potential to improve the motor capabilities of neurological patients in clinical practice.

Application of indocyanine green in surgery: A review of current evidence and implementation in trauma patients

Background: Modern surgical medicine strives to manage trauma while improving outcomes using functional imaging. Identification of viable tissues is crucial for the surgical management of polytrauma and burn patients presenting with soft tissue and hollow viscus injuries. Bowel anastomosis after trauma-related resection is associated with a high rate of leakage. The ability of the surgeon’s bare eye to determine bowel viability remains limited, and the need for a more standardized objective assessment has not yet been fulfilled. Hence, there is a need for more precise diagnostic tools to enhance surgical evaluation and visualization to aid early diagnosis and timely management to minimize trauma-associated complications. Indocyanine green (ICG) coupled with fluorescence angiography is a potential solution for this problem. ICG is a fluorescent dye that responds to near-infrared irradiation. Methods: We conducted a narrative review to address the utility of ICG in the surgical management of patients with trauma as well as elective surgery. Discussion: ICG has many applications in different medical fields and has recently become an important clinical indicator for surgical guidance. However, there is a paucity of information regarding the use of this technology to treat traumas. Recently, angiography with ICG has been introduced in clinical practice to visualize and quantify organ perfusion under several conditions, leading to fewer cases of anastomotic insufficiency. This has great potential to bridge this gap and enhance the clinical outcomes of surgery and patient safety. However, there is no consensus on the ideal dose, time, and manner of administration nor the indications that ICG provides a genuine advantage through greater safety in trauma surgical settings. Conclusions: There is a scarcity of publications describing the use of ICG in trauma patients as a potentially useful strategy to facilitate intraoperative decisions and to limit the extent of surgical resection. This review will improve our understanding of the utility of intraoperative ICG fluorescence in guiding and assisting trauma surgeons to deal with the intraoperative challenges and thus improve the patients’ operative care and safety in the field of trauma surgery.

Evaluation of MTT Heterogeneity of Perfusion CT Imaging in the Early Brain Injury Phase: An Insight into aSAH Pathopysiology

The concept of early brain injury (EBI) is based on the assumption of a global reduction in brain perfusion following aneurysmal subarachnoid hemorrhage (aSAH). However, the heterogeneity of computed tomography perfusion (CTP) imaging in EBI has not yet been investigated. In contrast, increased mean transit time (MTT) heterogeneity, a possible marker of microvascular perfusion heterogeneity, in the delayed cerebral ischemia (DCI) phase has recently been associated with a poor neurological outcome after aSAH. Therefore, in this study, we investigated whether the heterogeneity of early CTP imaging in the EBI phase is an independent predictor of the neurological outcome after aSAH. We retrospectively analyzed the heterogeneity of the MTT using the coefficient of variation (cvMTT) in early CTP scans (within 24 h after ictus) of 124 aSAH patients. Both linear and logistic regression were used to model the mRS outcome, which were treated as numerical and dichotomized values, respectively. Linear regression was used to investigate the linear dependency between the variables. No significant difference in cvMTT between the patients with and those without EVD could be observed (p = 0.69). We found no correlation between cvMTT in early CTP imaging and initial modified Fisher (p = 0.07) and WFNS grades (p = 0.23). The cvMTT in early perfusion imaging did not correlate significantly with the 6-month mRS for the entire study population (p = 0.15) or for any of the subgroups (without EVD: p = 0.21; with EVD: p = 0.3). In conclusion, microvascular perfusion heterogeneity, assessed by the heterogeneity of MTT in early CTP imaging, does not appear to be an independent predictor of the neurological outcome 6 months after aSAH.

Fast Optical Signals for Real-Time Retinotopy and Brain Computer Interface

A brain-computer interface (BCI) allows users to control external devices through brain activity. Portable neuroimaging techniques, such as near-infrared (NIR) imaging, are suitable for this goal. NIR imaging has been used to measure rapid changes in brain optical properties associated with neuronal activation, namely fast optical signals (FOS) with good spatiotemporal resolution. However, FOS have a low signal-to-noise ratio, limiting their BCI application. Here FOS were acquired with a frequency-domain optical system from the visual cortex during visual stimulation consisting of a rotating checkerboard wedge, flickering at 5 Hz. We used measures of photon count (Direct Current, DC light intensity) and time of flight (phase) at two NIR wavelengths (690 nm and 830 nm) combined with a machine learning approach for fast estimation of visual-field quadrant stimulation. The input features of a cross-validated support vector machine classifier were computed as the average modulus of the wavelet coherence between each channel and the average response among all channels in 512 ms time windows. An above chance performance was obtained when differentiating visual stimulation quadrants (left vs. right or top vs. bottom) with the best classification accuracy of ~63% (information transfer rate of ~6 bits/min) when classifying the superior and inferior stimulation quadrants using DC at 830 nm. The method is the first attempt to provide generalizable retinotopy classification relying on FOS, paving the way for the use of FOS in real-time BCI.

Intraoperative Fluorescence Visualization in Thoracoscopic Surgery

We report a clinical case of using indocyanine green inhalation to achieve intraoperative near-infrared fluorescence visualization of pulmonary ground-glass opacity in thoracoscopic wedge resection. The patient underwent thoracoscopic wedge resection under the real-time navigation of a near-infrared fluorescence imaging system with the indocyanine green inhalation performed 85 minutes before the surgery. The nebulized inhalation of indocyanine green (dose of 0.25 mg/kg) successfully guided surgeons to localize the small ground-glass opacity due to a filling defect of the fluorescence. The thoracoscopic near-infrared fluorescence navigation system delineated the tumor margin with high contrast and helped to minimize the damage to lung function.

Psychophysiological Assessment of Children with Cerebral Palsy during Robotic-Assisted Gait Training through Infrared Imaging

Cerebral palsy (CP) is a non-progressive neurologic pathology representing a leading cause of spasticity and concerning gait impairments in children. Robotic-assisted gait training (RAGT) is widely employed to treat this pathology to improve children's gait pattern. Importantly, the effectiveness of the therapy is strictly related to the engagement of the patient in the rehabilitation process, which depends on his/her psychophysiological state. The aim of the study is to evaluate the psychophysiological condition of children with CP during RAGT through infrared thermography (IRT), which was acquired during three sessions in one month. A repeated measure ANOVA was performed (i.e., mean value, standard deviation, and sample entropy) extracted from the temperature time course collected over the nose and corrugator, which are known to be indicative of the psychophysiological state of the individual. Concerning the corrugator, significant differences were found for the sample entropy (F (1.477, 5.907) = 6.888; p = 0.033) and for the mean value (F (1.425, 5.7) = 5.88; p = 0.047). Regarding the nose tip, the sample entropy showed significant differences (F (1.134, 4.536) = 11.5; p = 0.041). The findings from this study suggests that this approach can be used to evaluate in a contactless manner the psychophysiological condition of the children with CP during RAGT, allowing to monitor their engagement to the therapy, increasing the benefits of the treatment.

Theoretical Study on Spectrum and Luminescence Mechanism of Indocyanine Green Dye Based on Density Functional Theory (DFT)

Indocyanine green is a great near-infrared fluorescence with good luminescent properties and important medical applications. In this paper, the theoretical spectrum and orbital model of its molecular level are established. The two most probable conformations were studied, and their energies, vibrational spectra, UV-Vis absorption spectra, frontier molecular orbitals (HOMO and LUMO), and energy gaps were obtained by density functional theory (DFT) calculations, respectively. This provides a theoretical and design basis for the development of novel dyes similar to indocyanine green dyes and a reference case for improved application methods and synthetic predesign of novel fluorescent dyes.

Identification of Functional Cortical Plasticity in Children with Cerebral Palsy Associated to Robotic-Assisted Gait Training: An fNIRS Study

Cerebral palsy (CP) is a non-progressive neurologic condition that causes gait limitations, spasticity, and impaired balance and coordination. Robotic-assisted gait training (RAGT) has become a common rehabilitation tool employed to improve the gait pattern of people with neurological impairments. However, few studies have demonstrated the effectiveness of RAGT in children with CP and its neurological effects through portable neuroimaging techniques, such as functional near-infrared spectroscopy (fNIRS). The aim of the study is to evaluate the neurophysiological processes elicited by RAGT in children with CP through fNIRS, which was acquired during three sessions in one month. The repeated measure ANOVA was applied to the β-values delivered by the General Linear Model (GLM) analysis used for fNIRS data analysis, showing significant differences in the activation of both prefrontal cortex (F (1.652, 6.606) = 7.638; p = 0.022), and sensorimotor cortex (F (1.294, 5.175) = 11.92; p = 0.014) during the different RAGT sessions. In addition, a cross-validated Machine Learning (ML) framework was implemented to estimate the gross motor function measure (GMFM-88) from the GLM β-values, obtaining an estimation with a correlation coefficient r = 0.78. This approach can be used to tailor clinical treatment to each child, improving the effectiveness of rehabilitation for children with CP.

Effect of Early Rehabilitation Nursing on Motor Function and Living Ability of Patients with Traumatic Brain Injury Based on Orem’s Self-Care Theory

Objective

To explore the effect of early rehabilitation nursing on motor function and living ability of patients with traumatic brain injury (TBI) based on Orem's self-care theory.

Methods

A total of 60 patients with TBI treated in our hospital from February 2019 to June 2021 were enrolled. The patients were randomly divided into a control group and a research group. The control group adopted the early rehabilitation nursing model, while the research group adopted the early rehabilitation nursing model based on Orem's self-nursing theory. Nursing satisfaction, Fugl-Meyer score, NIH-SS score, Barthel index, quality of life score, and compliance were in the comparison of the two groups.

Results

The nursing satisfaction of the research group was higher than that of the control group (P < 0.05). Compared with the control group, the Fugl-Meyer scores of the research group were higher at 1 month, 2 months, and 3 months after nursing (P < 0.05). After nursing, the NIH-SS score of the two groups decreased. In the comparison of the two groups, the NIH-SS score of the research group at 1 month, 2 months, and 3 months after nursing was lower (P < 0.05). After nursing, the Barthel index of the two groups increased. In the comparison of the two groups, the Barthel index of the research group was higher compared to the control group at 1 month, 2 months, and 3 months after nursing (P < 0.05). The scores of physiological function, psychological function, social function, and health self-cognition in the research group were lower (P < 0.05). The compliance rate of the research group was higher than that of the control group (P < 0.05).

Conclusion

Patients with TBI receive early rehabilitation nursing based on Orem's self-care theory, which can effectively improve patient satisfaction and compliance and achieve the purpose of improving motor function and living ability. This nursing program is worth popularizing in the clinic.

Sterically Shielded Hydrophilic Analogs of Indocyanine Green

A modular synthetic process enables two or four shielding arms to be appended strategically over the fluorochromes of near-infrared cyanine heptamethine dyes to create hydrophilic analogs of clinically approved indocyanine green. A key synthetic step is the facile substitution of a heptamethine 4'-Cl atom by a phenol bearing two triethylene glycol chains. The lead compound is a heptamethine dye with four shielding arms, and a series of comparative spectroscopy studies showed that the shielding arms (a) increased dye photostability and chemical stability and (b) inhibited dye self-aggregation and association with albumin protein. In mice, the dye cleared from the blood primarily through the renal pathway rather than the biliary pathway for ICG. This change in biodistribution reflects the much smaller hydrodynamic diameter of the shielded hydrophilic ICG analog compared to the 67 kDa size of the ICG/albumin complex. An attractive feature of versatile synthetic chemistry is the capability to systematically alter the dye's hydrodynamic diameter. The sterically shielded hydrophilic ICG dye platform is well-suited for immediate incorporation into dynamic contrast-enhanced (DCE) spectroscopy or imaging protocols using the same cameras and detectors that have been optimized for ICG.

Near-infrared fluorescence imaging with indocyanine green for assessment of donor livers in a rat model of ischemia-reperfusion

BACKGROUND

Although marginal donor livers expand the donor pool, an ideal method for quantitatively evaluating the quality of donor livers has not been developed. This study aimed to explore the feasibility of indocyanine green (ICG) fluorescence imaging for estimating liver function in an ischemia-reperfusion model.

METHODS

Forty-eight rats were randomly and evenly divided into 8 groups: the control group and the experimental groups (I-VII). The portal vein blocking period was 0 min, 10 min, 20 min, 30 min, 40 min, 50 min and 60 min. After blood flow was reestablished and the hemodynamics stabilized, ICG was injected through the dorsal penile vein as a bolus, and the fluorescence signal was recorded for 30 min in real time. The fluorescence intensity (FI) curve of the liver was fitted with an asymptotic regression model. Fresh liver tissues and serum were obtained from the middle lobe of the liver on postoperative day (POD) 1 and POD 7 for histopathological evaluation and liver function tests.

RESULTS

The growth rate of the FI curve, parameter b3, decreased from groups I to VII. According to the two sudden changes in b3 (20 min, 50 min), the experimental groups could be classified into 3 groups (A, B and C). Hepatocytes in groups I-II showed slight edema, group III began to show obvious hepatocyte edema and vacuolar degeneration, and in groups VI-VII, severe hepatocyte degeneration, necrosis and large inflammatory cell infiltration were observed. Suzuki's scores in the 3 groups were also significantly different (P < 0.01). At the same time, the serum liver function in the experimental groups showed a significant increase on POD 1 and a decrease on POD 7. The alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TB) levels of groups A, B, and C were significantly different on POD 1 (P < 0.05), and the ALT and direct bilirubin (DB) levels were significantly different on POD 7 (P < 0.05); the lactic dehydrogenase (LDH) level of the group C was significantly higher than that of the groups A and B on POD 1 and POD 7. Meanwhile, the 7-day survival rate of the rats in group C was poor compared to that of the rats in groups A and B (58.3% vs. 100% vs. 100%).

CONCLUSION

ICG fluorescence imaging is effective for estimating the degree of liver damage and grading in an ischemia-reperfusion model. It probably has the potential for use in assessing the quality of the donor liver in liver transplantation.

Resting-State Functional Magnetic Resonance Imaging of Interhemispheric Functional Connectivity in Experimental Traumatic Brain Injury

Although resting-state functional magnetic resonance imaging (rsfMRI) has the potential to offer insights into changes in functional connectivity networks after traumatic brain injury (TBI), there are few studies that examine the effects of moderate TBI for monitoring functional recovery in experimental TBI, and thus the neural correlates of brain recovery from moderate TBI remain incompletely understood. Non-invasive rsfMRI was used to longitudinally investigate changes in interhemispheric functional connectivity (IFC) after a moderate TBI to the unilateral sensorimotor cortex in rats (n = 9) up to 14 days. Independent component analysis of the rsfMRI data was performed. Correlations of rsfMRI sensorimotor networks were made with changes in behavioral scores, lesion volume, and T₂- and diffusion-weighted images across time. TBI animals showed less localized rsfMRI patterns in the sensorimotor network compared to sham (n = 6) and normal (n = 5) animals. rsfMRI clusters in the sensorimotor network showed less bilateral symmetry compared to sham and normal animals, indicative of IFC disruption. With time after injury, many of the rsfMRI patterns in the sensorimotor network showed more bilateral symmetry, indicative of IFC recovery. The disrupted IFC in the sensorimotor and subsequent partial recovery showed a positive correlation with changes in behavioral scores. Overall, rsfMRI detected widespread disruption and subsequent recovery of IFC within the sensorimotor networks post-TBI, which correlated with behavioral changes. Therefore, rsfMRI offers the means to probe functional brain reorganization and thus has the potential to serve as an imaging marker to longitudinally stage TBI and monitor for novel treatments.

Indocyanine Green-Camptothecin Co-Loaded Perfluorocarbon Double-Layer Nanocomposite: A Versatile Nanotheranostics for Photochemotherapy and FDOT Diagnosis of Breast Cancer

Breast cancer remains the most frequently diagnosed cancer and is the leading cause of neoplastic disease burden for females worldwide, suggesting that effective therapeutic and/or diagnostic strategies are still urgently needed. In this study, a type of indocyanine green (ICG) and camptothecin (CPT) co-loaded perfluorocarbon double-layer nanocomposite named ICPNC was developed for detection and photochemotherapy of breast cancer. The ICPNCs were designed to be surface modifiable for on-demand cell targeting and can serve as contrast agents for fluorescence diffuse optical tomography (FDOT). Upon near infrared (NIR) irradiation, the ICPNCs can generate a significantly increased production of singlet oxygen compared to free ICG, and offer a comparable cytotoxicity with reduced chemo-drug dosage. Based on the results of animal study, we further demonstrated that the ICPNCs ([ICG]/[CPT] = 40-/7.5-μM) in association with 1-min NIR irradiation (808 nm, 6 W/cm²) can provide an exceptional anticancer effect to the MDA-MB-231 tumor-bearing mice whereby the tumor size was significantly reduced by 80% with neither organ damage nor systemic toxicity after a 21-day treatment. Given a number of aforementioned merits, we anticipate that the developed ICPNC is a versatile theranostic nanoagent which is highly promising to be used in the clinic.

Blood-Brain Barrier Breakdown in Stress and Neurodegeneration: Biochemical Mechanisms and New Models for Translational Research

Blood-brain barrier (BBB) is a structural and functional element of the neurovascular unit (NVU), which includes cells of neuronal, glial, and endothelial nature. The main functions of NVU include maintenance of the control of metabolism and chemical homeostasis in the brain tissue, ensuring adequate blood flow in active regions, regulation of neuroplasticity processes, which is realized through intercellular interactions under normal conditions, under stress, in neurodegeneration, neuroinfection, and neurodevelopmental diseases. Current versions of the BBB and NVU models, static and dynamic, have significantly expanded research capabilities, but a number of issues remain unresolved, in particular, personification of the models for a patient. In addition, application of both static and dynamic models has an important problem associated with the difficulty in reproducing pathophysiological mechanisms responsible for the damage of the structural and functional integrity of the barrier in the diseases of the central nervous system. More knowledge on the cellular and molecular mechanisms of BBB and NVU damage in pathology is required to solve this problem. This review discusses current state of the cellular and molecular mechanisms that control BBB permeability, pathobiochemical mechanisms and manifestations of BBB breakdown in stress and neurodegenerative diseases, as well as the problems and prospects of creating in vitro BBB and NVU models for translational studies in neurology and neuropharmacology. Deciphering BBB (patho)physiology will open up new opportunities for further development in the related areas of medicine such as regenerative medicine, neuropharmacology, and neurorehabilitation.

A novel wireless optical technique for quantitative evaluation of cerebral perfusion pressure in a fluid percussion animal model of traumatic brain injury

Background

Cerebral perfusion pressure (CPP) calculated by mean arterial pressure (MAP) minus intracranial pressure (ICP) is related to blood flow into the brain and reflects cerebral ischemia and oxygenation indirectly. Near-infrared spectroscopy (NIRS) can assess cerebral ischemia and hypoxia non-invasively and has been widely used in neuroscience. However, the correlation between CPP and NIRS, and its potential application in traumatic brain injury, has seldom been investigated.

Methods

We used a novel wireless NIRS system and commercial ICP and MAP devices to assess the trauma to rat brains using different impact intensity. The relationship between CPP and NIRS parameters with increasing impact strength were investigated.

Results

The results showed that changes in CPP (∆CPP), oxy-hemoglobin {∆[HbO₂]}, total-hemoglobin {∆[HbT]}, and deoxy-hemoglobin were inversely proportional to the increase in impact intensity, and the correlations between ∆CPP, NIRS parameters {∆[HbO₂], and ∆[HbT]} were significant.

Conclusions

The NIRS system can assess cerebral ischemia and oxygenation non-invasively and changes of HbO₂ and HbT may be used as reference parameters to assess the level of CPP in an animal model of traumatic brain injury.

Mismatch between Tissue Partial Oxygen Pressure and Near-Infrared Spectroscopy Neuromonitoring of Tissue Respiration in Acute Brain Trauma: The Rationale for Implementing a Multimodal Monitoring Strategy

The brain tissue partial oxygen pressure (PbtO₂) and near-infrared spectroscopy (NIRS) neuromonitoring are frequently compared in the management of acute moderate and severe traumatic brain injury patients; however, the relationship between their respective output parameters flows from the complex pathogenesis of tissue respiration after brain trauma. NIRS neuromonitoring overcomes certain limitations related to the heterogeneity of the pathology across the brain that cannot be adequately addressed by local-sample invasive neuromonitoring (e.g., PbtO₂ neuromonitoring, microdialysis), and it allows clinicians to assess parameters that cannot otherwise be scanned. The anatomical co-registration of an NIRS signal with axial imaging (e.g., computerized tomography scan) enhances the optical signal, which can be changed by the anatomy of the lesions and the significance of the radiological assessment. These arguments led us to conclude that rather than aiming to substitute PbtO₂ with tissue saturation, multiple types of NIRS should be included via multimodal systemic- and neuro-monitoring, whose values then are incorporated into biosignatures linked to patient status and prognosis. Discussion on the abnormalities in tissue respiration due to brain trauma and how they affect the PbtO₂ and NIRS neuromonitoring is given.

The AMPAR antagonist perampanel protects the neurovascular unit against traumatic injury via regulating Sirt3

Introduction

Perampanel is a highly selective and noncompetitive α‐amino‐3 ‐hydroxy‐5‐methyl‐4‐isoxazole propionate receptor (AMPAR) antagonist, which has been used as an orally administered antiepileptic drug in more than 55 countries. Recently, perampanel was shown to exert neuroprotective effects in hemorrhagic and ischemic stroke models via regulating blood–brain barrier (BBB) function.

Aim

Here, the protective effects of perampanel were investigated in an in vitro neurovascular unit (NVU) system established using a triple cell co‐culture model (neurons, astrocytes, and brain microvascular endothelial cells) and in an in vivo traumatic brain injury (TBI) model.

Results

Neurons in the NVU system exhibit a more mature morphological phenotype compared with neurons cultured alone, and the co‐culture system mimicked an impermeable barrier in vitro. Perampanel protects the NVU system against traumatic and excitotoxic injury, as evidenced by reduced lactate dehydrogenase (LDH) release and apoptotic rate. Treatment with perampanel attenuated lipid peroxidation and expression of inflammatory cytokines. In addition, perampanel increased Sirt3 protein expression, enhanced the activities of mitochondrial enzyme IDH2 and SOD2, and preserved BBB function in vitro. Knockdown of Sirt3 using specific siRNA (Si‐Sirt3) partially reserved the effects of perampanel on neuronal injury and BBB function. Treatment with perampanel in vivo attenuated brain edema, preserved neurological function, inhibited apoptosis and microglia activation after TBI. Furthermore, perampanel increased the expression of Sirt3 and preserved BBB function after TBI. The effect of perampanel on BBB function and brain edema was abolished by knockdown of Sirt3 in vivo.

Conclusion

Our results indicate that the noncompetitive AMPAR antagonist perampanel protects the NVU system and reduces brain damage after TBI via activating the Sirt3 cascades.

Dynamic contrast-enhanced near-infrared spectroscopy using indocyanine green on moderate and severe traumatic brain injury: a prospective observational study

BACKGROUND

The care given to moderate and severe traumatic brain injury (TBI) patients may be hampered by the inability to tailor their treatments according to their neurological status. Contrast-enhanced near-infrared spectroscopy (NIRS) with indocyanine green (ICG) could be a suitable neuromonitoring tool.

METHODS

Monitoring the effective attenuation coefficients (EAC), we compared the ICG kinetics between five TBI and five extracranial trauma patients, following a venous-injection of 5 mL of 1 mg/mL ICG, using two commercially available NIRS devices.

RESULTS

A significantly slower passage of the dye through the brain of the TBI group was observed in two parameters related to the first ICG inflow into the brain (P=0.04; P=0.01). This is likely related to the reduction of cerebral perfusion following TBI. Significant changes in ICG optical properties minutes after injection (P=0.04) were registered. The acquisition of valid optical data in a clinical environment was challenging.

CONCLUSIONS

Future research should analyze abnormalities in the ICG kinetic following brain trauma, test how these values can enhance care in TBI, and adapt the current optical devices to clinical settings. Also, studies on the pattern in changes of ICG optical properties after venous injection can improve the accuracy of the values detected.

Fiberless, Multi-Channel fNIRS-EEG System Based on Silicon Photomultipliers: Towards Sensitive and Ecological Mapping of Brain Activity and Neurovascular Coupling

Portable neuroimaging technologies can be employed for long-term monitoring of neurophysiological and neuropathological states. Functional Near-Infrared Spectroscopy (fNIRS) and Electroencephalography (EEG) are highly suited for such a purpose. Their multimodal integration allows the evaluation of hemodynamic and electrical brain activity together with neurovascular coupling. An innovative fNIRS-EEG system is here presented. The system integrated a novel continuous-wave fNIRS component and a modified commercial EEG device. fNIRS probing relied on fiberless technology based on light emitting diodes and silicon photomultipliers (SiPMs). SiPMs are sensitive semiconductor detectors, whose large detection area maximizes photon harvesting from the scalp and overcomes limitations of fiberless technology. To optimize the signal-to-noise ratio and avoid fNIRS-EEG interference, a digital lock-in was implemented for fNIRS signal acquisition. A benchtop characterization of the fNIRS component showed its high performances with a noise equivalent power below 1 pW. Moreover, the fNIRS-EEG device was tested in vivo during tasks stimulating visual, motor and pre-frontal cortices. Finally, the capabilities to perform ecological recordings were assessed in clinical settings on one Alzheimer's Disease patient during long-lasting cognitive tests. The system can pave the way to portable technologies for accurate evaluation of multimodal brain activity, allowing their extensive employment in ecological environments and clinical practice.