Subarachnoid blood acutely induces spreading depolarizations and early cortical infarction

Utility and rationale for continuous EEG monitoring: a primer for the general intensivist

This review offers a comprehensive guide for general intensivists on the utility of continuous EEG (cEEG) monitoring for critically ill patients. Beyond the primary role of EEG in detecting seizures, this review explores its utility in neuroprognostication, monitoring neurological deterioration, assessing treatment responses, and aiding rehabilitation in patients with encephalopathy, coma, or other consciousness disorders. Most seizures and status epilepticus (SE) events in the intensive care unit (ICU) setting are nonconvulsive or subtle, making cEEG essential for identifying these otherwise silent events. Imaging and invasive approaches can add to the diagnosis of seizures for specific populations, given that scalp electrodes may fail to identify seizures that may be detected by depth electrodes or electroradiologic findings. When cEEG identifies SE, the risk of secondary neuronal injury related to the time-intensity "burden" often prompts treatment with anti-seizure medications. Similarly, treatment may be administered for seizure-spectrum activity, such as periodic discharges or lateralized rhythmic delta slowing on the ictal-interictal continuum (IIC), even when frank seizures are not evident on the scalp. In this setting, cEEG is utilized empirically to monitor treatment response. Separately, cEEG has other versatile uses for neurotelemetry, including identifying the level of sedation or consciousness. Specific conditions such as sepsis, traumatic brain injury, subarachnoid hemorrhage, and cardiac arrest may each be associated with a unique application of cEEG; for example, predicting impending events of delayed cerebral ischemia, a feared complication in the first two weeks after subarachnoid hemorrhage. After brief training, non-neurophysiologists can learn to interpret quantitative EEG trends that summarize elements of EEG activity, enhancing clinical responsiveness in collaboration with clinical neurophysiologists. Intensivists and other healthcare professionals also play crucial roles in facilitating timely cEEG setup, preventing electrode-related skin injuries, and maintaining patient mobility during monitoring.

Brief apnea with hypoventilation reduces seizure duration and shifts seizure location for several hours in a model of severe traumatic brain injury

OBJECTIVE

Seizures can be difficult to control in infants and toddlers. Seizures with periods of apnea and hypoventilation are common following severe traumatic brain injury (TBI). We previously observed that brief apnea with hypoventilation (A&H) in our severe TBI model acutely interrupted seizures. The current study is designed to determine the effect of A&H on subsequent seizures and whether A&H has potential therapeutic implications.

METHODS

Piglets (1 week or 1 month old) received multifactorial injuries: cortical impact, mass effect, subdural hematoma, subarachnoid hemorrhage, and seizures induced with kainic acid. A&H (1 min apnea, 10 min hypoventilation) was induced either before or after seizure induction, or control piglets received subdural/subarachnoid hematoma and seizure without A&H. In an intensive care unit, piglets were sedated, intubated, and mechanically ventilated, and epidural electroencephalogram was recorded for an average of 18 h after seizure induction.

RESULTS

In our severe TBI model, A&H after seizure reduced ipsilateral seizure burden by 80% compared to the same injuries without A&H. In the A&H before seizure induction group, more piglets had exclusively contralateral seizures, although most piglets in all groups had seizures that shifted location throughout the several hours of seizure. After 8-10 h, seizures transitioned to interictal epileptiform discharges regardless of A&H or timing of A&H.

SIGNIFICANCE

Even brief A&H may alter traumatic seizures. In our preclinical model, we will address the possibility of hypercapnia with normoxia, with controlled intracranial pressure, as a therapeutic option for children with status epilepticus after hemorrhagic TBI.

Diffuse microglial responses and persistent EEG changes correlate with poor neurological outcome in a model of subarachnoid hemorrhage

The mechanism by which subarachnoid hemorrhage (SAH) leads to chronic neurologic deficits is unclear. One possibility is that blood activates microglia to drive inflammation that leads to synaptic loss and impaired brain function. Using the endovascular perforation model of SAH in rats, we investigated short-term effects on microglia together with long-term effects on EEG and neurologic function for up to 3 months. Within the first week, microglia were increased both at the site of injury and diffusely across the cortex (2.5-fold increase in SAH compared to controls, p = 0.012). Concomitantly, EEGs from SAH animals showed focal increases in slow wave activity and diffuse reduction in fast activity. When expressed as a fast-slow spectral ratio, there were significant interactions between group and time (p < 0.001) with less ipsilateral recovery over time. EEG changes were most pronounced during the first week and correlated with neurobehavioral impairment. In vitro, the blood product hemin was sufficient to increase microglia phagocytosis nearly six-fold (p = 0.032). Immunomodulatory treatment with fingolimod after SAH reduced microglia, improved neurological function, and increased survival. These findings, which parallel many of the EEG changes seen in patients, suggest that targeting neuroinflammation could reduce long-term neurologic dysfunction following SAH.

Multimodal imaging of the role of hyperglycemia following experimental subarachnoid hemorrhage

Hyperglycemia has been linked to worsening outcomes after subarachnoid hemorrhage (SAH). Nevertheless, the mechanisms involved in the pathogenesis of SAH have been scarcely evaluated so far. The role of hyperglycemia was assessed in an experimental model of SAH by T2 weighted, dynamic contrast-enhanced magnetic resonance imaging (T2W and DCE-MRI), [18F]BR-351 PET imaging and immunohistochemistry. Measures included the volume of bleeding, the extent of cerebral infarction and brain edema, blood brain barrier disruption (BBBd), neutrophil infiltration and matrix metalloprotease (MMP) activation. The neurofunctional outcome, neurodegeneration and myelinization were also investigated. The induction of hyperglycemia increased mortality, the size of the ischemic lesion, brain edema, neurodegeneration and worsened neurological outcome during the first 3 days after SAH in rats. In addition, these results show for the first time the exacerbating effect of hyperglycemia on in vivo MMP activation, Intercellular Adhesion Molecule 1 (ICAM-1) expression and neutrophil infiltration together with increased BBBd, bleeding volume and fibrinogen accumulation at days 1 and 3 after SAH. Notably, these data provide valuable insight into the detrimental effect of hyperglycemia on early BBB damage mediated by neutrophil infiltration and MMP activation that could explain the worse prognosis in SAH.

All Three Supersystems-Nervous, Vascular, and Immune-Contribute to the Cortical Infarcts After Subarachnoid Hemorrhage

The recently published DISCHARGE-1 trial supports the observations of earlier autopsy and neuroimaging studies that almost 70% of all focal brain damage after aneurysmal subarachnoid hemorrhage are anemic infarcts of the cortex, often also affecting the white matter immediately below. The infarcts are not limited by the usual vascular territories. About two-fifths of the ischemic damage occurs within ~ 48 h; the remaining three-fifths are delayed (within ~ 3 weeks). Using neuromonitoring technology in combination with longitudinal neuroimaging, the entire sequence of both early and delayed cortical infarct development after subarachnoid hemorrhage has recently been recorded in patients. Characteristically, cortical infarcts are caused by acute severe vasospastic events, so-called spreading ischemia, triggered by spontaneously occurring spreading depolarization. In locations where a spreading depolarization passes through, cerebral blood flow can drastically drop within a few seconds and remain suppressed for minutes or even hours, often followed by high-amplitude, sustained hyperemia. In spreading depolarization, neurons lead the event, and the other cells of the neurovascular unit (endothelium, vascular smooth muscle, pericytes, astrocytes, microglia, oligodendrocytes) follow. However, dysregulation in cells of all three supersystems-nervous, vascular, and immune-is very likely involved in the dysfunction of the neurovascular unit underlying spreading ischemia. It is assumed that subarachnoid blood, which lies directly on the cortex and enters the parenchyma via glymphatic channels, triggers these dysregulations. This review discusses the neuroglial, neurovascular, and neuroimmunological dysregulations in the context of spreading depolarization and spreading ischemia as critical elements in the pathogenesis of cortical infarcts after subarachnoid hemorrhage.

Similarities in the Electrographic Patterns of Delayed Cerebral Infarction and Brain Death After Aneurysmal and Traumatic Subarachnoid Hemorrhage

While subarachnoid hemorrhage is the second most common hemorrhagic stroke in epidemiologic studies, the recent DISCHARGE-1 trial has shown that in reality, three-quarters of focal brain damage after subarachnoid hemorrhage is ischemic. Two-fifths of these ischemic infarctions occur early and three-fifths are delayed. The vast majority are cortical infarcts whose pathomorphology corresponds to anemic infarcts. Therefore, we propose in this review that subarachnoid hemorrhage as an ischemic-hemorrhagic stroke is rather a third, separate entity in addition to purely ischemic or hemorrhagic strokes. Cumulative focal brain damage, determined by neuroimaging after the first 2 weeks, is the strongest known predictor of patient outcome half a year after the initial hemorrhage. Because of the unique ability to implant neuromonitoring probes at the brain surface before stroke onset and to perform longitudinal MRI scans before and after stroke, delayed cerebral ischemia is currently the stroke variant in humans whose pathophysiological details are by far the best characterized. Optoelectrodes located directly over newly developing delayed infarcts have shown that, as mechanistic correlates of infarct development, spreading depolarizations trigger (1) spreading ischemia, (2) severe hypoxia, (3) persistent activity depression, and (4) transition from clustered spreading depolarizations to a negative ultraslow potential. Furthermore, traumatic brain injury and subarachnoid hemorrhage are the second and third most common etiologies of brain death during continued systemic circulation. Here, we use examples to illustrate that although the pathophysiological cascades associated with brain death are global, they closely resemble the local cascades associated with the development of delayed cerebral infarcts.

Prevalence of small vessel disease and incidental DWI-positive lesions in patients with aneurysmal subarachnoid hemorrhage versus intracerebral hemorrhage

INTRODUCTION

Aneurysmal subarachnoid hemorrhage (aSAH) and intracerebral hemorrhage (ICH) are main forms of hemorrhagic stroke. Data regarding cerebral small vessel disease (SVD) burden and incidental small lesions on diffusion-weighted imaging (DWI) following aSAH are sparse.

PATIENTS AND METHODS

We retrospectively analyzed a prospective cohort of aSAH and ICH patients with brain MRI within 30 days after onset from March 2015 to January 2023. White matter hyperintensity (WMH), lacune, perivascular space, cerebral microbleed (CMB), total SVD score, and incidental DWI lesions were assessed and compared between aSAH and ICH. Clinical and radiological characteristics associated with small DWI lesions in aSAH were investigated.

RESULTS

We included 180 patients with aSAH (median age [IQR] 53 [47-61] years) and 299 with ICH (63 [53-73] years). DWI lesions were more common in aSAH than ICH (47.8% vs 14.4%, p < 0.001). Higher total SVD score was associated with ICH versus aSAH irrespective of hematoma location, whereas DWI lesions and strictly lobar CMBs were correlated with aSAH. Multivariable analysis showed that shorter time from onset to MRI, anterior circulation aneurysm rupture, CMB ⩾ 5, and total SVD score were associated with DWI lesions in aSAH.

DISCUSSION AND CONCLUSION

Incidental DWI lesions and strictly lobar CMBs were more frequent in aSAH versus ICH whereas ICH had higher SVD burden. Incidental DWI lesions in aSAH were associated with multiple clinical and imaging factors. Longitudinal studies to investigate the dynamic change and prognostic value of the covert hemorrhagic and ischemic lesions in aSAH seem justified.

Expression, Functional Polymorphism, and Diagnostic Values of MIAT rs2331291 and H19 rs217727 Long Non-Coding RNAs in Cerebral Ischemic Stroke Egyptian Patients

Cerebral ischemic stroke (CIS) is a severe cerebral vascular event. This research aimed to evaluate the role of single-nucleotide polymorphisms (SNPs) of the lncRNAs MIAT rs2331291 and H19 rs217727 and epigenetic methylation in the expression patterns of serum lncRNA H19 in CIS Egyptian patients. It included 80 CIS cases and 40 healthy subjects. Serum MIAT expression levels decreased, whereas serum H19 expression levels increased among CIS compared to controls. For MIAT rs2331291, there were significant differences in the genotypic and allelic frequencies between the CIS and healthy subjects at p = 0.02 and p = 0.0001, respectively. Our findings illustrated a significantly increased MIAT T/T genotype frequency in hypertensive CIS compared to non-hypertensive CIS at p = 0.004. However, H19 rs217727 gene frequency C/C was not significantly higher in non-hypertensive CIS than in hypertensive CIS. The methylation of the H19 gene promoter was significantly higher in CIS patients compared to healthy subjects. The level of MIAT was positively correlated with serum H19 in CIS. Receiver operating characteristics (ROC) analysis revealed that serum MIAT and H19 have a high diagnostic potential for distinguishing CIS subjects from healthy ones. In conclusion, the MIAT-rs2331291 polymorphism might serve as a novel potential indicator of CIS.

Porcine Astrocytes and Their Relevance for Translational Neurotrauma Research

Astrocytes are essential to virtually all brain processes, from ion homeostasis to neurovascular coupling to metabolism, and even play an active role in signaling and plasticity. Astrocytic dysfunction can be devastating to neighboring neurons made inherently vulnerable by their polarized, excitable membranes. Therefore, correcting astrocyte dysfunction is an attractive therapeutic target to enhance neuroprotection and recovery following acquired brain injury. However, the translation of such therapeutic strategies is hindered by a knowledge base dependent almost entirely on rodent data. To facilitate additional astrocytic research in the translatable pig model, we present a review of astrocyte findings from pig studies of health and disease. We hope that this review can serve as a road map for intrepid pig researchers interested in studying astrocyte biology.

Cortical Spreading Depolarization and Delayed Cerebral Ischemia; Rethinking Secondary Neurological Injury in Subarachnoid Hemorrhage

Poor outcomes in Subarachnoid Hemorrhage (SAH) are in part due to a unique form of secondary neurological injury known as Delayed Cerebral Ischemia (DCI). DCI is characterized by new neurological insults that continue to occur beyond 72 h after the onset of the hemorrhage. Historically, it was thought to be a consequence of hypoperfusion in the setting of vasospasm. However, DCI was found to occur even in the absence of radiographic evidence of vasospasm. More recent evidence indicates that catastrophic ionic disruptions known as Cortical Spreading Depolarizations (CSD) may be the culprits of DCI. CSDs occur in otherwise healthy brain tissue even without demonstrable vasospasm. Furthermore, CSDs often trigger a complex interplay of neuroinflammation, microthrombi formation, and vasoconstriction. CSDs may therefore represent measurable and modifiable prognostic factors in the prevention and treatment of DCI. Although Ketamine and Nimodipine have shown promise in the treatment and prevention of CSDs in SAH, further research is needed to determine the therapeutic potential of these as well as other agents.

Immunological Profile of Vasospasm after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) carries high mortality and disability rates, which are substantially driven by complications. Early brain injury and vasospasm can happen after SAH and are crucial events to prevent and treat to improve prognosis. In recent decades, immunological mechanisms have been implicated in SAH complications, with both innate and adaptive immunity involved in mechanisms of damage after SAH. The purpose of this review is to summarize the immunological profile of vasospasm, highlighting the potential implementation of biomarkers for its prediction and management. Overall, the kinetics of central nervous system (CNS) immune invasion and soluble factors' production critically differs between patients developing vasospasm compared to those not experiencing this complication. In particular, in people developing vasospasm, a neutrophil increase develops in the first minutes to days and pairs with a mild depletion of CD45+ lymphocytes. Cytokine production is boosted early on after SAH, and a steep increase in interleukin-6, metalloproteinase-9 and vascular endothelial growth factor (VEGF) anticipates the development of vasospasm after SAH. We also highlight the role of microglia and the potential influence of genetic polymorphism in the development of vasospasm and SAH-related complications.

Multimodal Neuromonitoring and Neurocritical Care in Swine to Enhance Translational Relevance in Brain Trauma Research

Neurocritical care significantly impacts outcomes after moderate-to-severe acquired brain injury, but it is rarely applied in preclinical studies. We created a comprehensive neurointensive care unit (neuroICU) for use in swine to account for the influence of neurocritical care, collect clinically relevant monitoring data, and create a paradigm that is capable of validating therapeutics/diagnostics in the unique neurocritical care space. Our multidisciplinary team of neuroscientists, neurointensivists, and veterinarians adapted/optimized the clinical neuroICU (e.g., multimodal neuromonitoring) and critical care pathways (e.g., managing cerebral perfusion pressure with sedation, ventilation, and hypertonic saline) for use in swine. Moreover, this neurocritical care paradigm enabled the first demonstration of an extended preclinical study period for moderate-to-severe traumatic brain injury with coma beyond 8 h. There are many similarities with humans that make swine an ideal model species for brain injury studies, including a large brain mass, gyrencephalic cortex, high white matter volume, and topography of basal cisterns, amongst other critical factors. Here we describe the neurocritical care techniques we developed and the medical management of swine following subarachnoid hemorrhage and traumatic brain injury with coma. Incorporating neurocritical care in swine studies will reduce the translational gap for therapeutics and diagnostics specifically tailored for moderate-to-severe acquired brain injury.

Neuroinflammatory mediators in acquired epilepsy: an update

Epilepsy is a group of chronic neurological disorders that have diverse etiologies but are commonly characterized by spontaneous seizures and behavioral comorbidities. Although the mechanisms underlying the epileptic seizures mostly remain poorly understood and the causes often can be idiopathic, a considerable portion of cases are known as acquired epilepsy. This form of epilepsy is typically associated with prior neurological insults, which lead to the initiation and progression of epileptogenesis, eventually resulting in unprovoked seizures. A convergence of evidence in the past two decades suggests that inflammation within the brain may be a major contributing factor to acquired epileptogenesis. As evidenced in mounting preclinical and human studies, neuroinflammatory processes, such as activation and proliferation of microglia and astrocytes, elevated production of pro-inflammatory cytokines and chemokines, blood-brain barrier breakdown, and upregulation of inflammatory signaling pathways, are commonly observed after seizure-precipitating events. An increased knowledge of these neuroinflammatory processes in the epileptic brain has led to a growing list of inflammatory mediators that can be leveraged as potential targets for new therapies of epilepsy and/or biomarkers that may provide valued information for the diagnosis and prognosis of the otherwise unpredictable seizures. In this review, we mainly focus on the most recent progress in understanding the roles of these inflammatory molecules in acquired epilepsy and highlight the emerging evidence supporting their candidacy as novel molecular targets for new pharmacotherapies of acquired epilepsy and the associated behavioral deficits.

Less-invasive subdural electrocorticography for investigation of spreading depolarizations in patients with subarachnoid hemorrhage

Introduction

Wyler-strip electrodes for subdural electrocorticography (ECoG) are the gold standard for continuous bed-side monitoring of pathological cortical network events, such as spreading depolarizations (SD) and electrographic seizures. Recently, SD associated parameters were shown to be (1) a marker of early brain damage after aneurysmal subarachnoid hemorrhage (aSAH), (2) the strongest real-time predictor of delayed cerebral ischemia currently known, and (3) the second strongest predictor of patient outcome at 7 months. The strongest predictor of patient outcome at 7 months was focal brain damage segmented on neuroimaging 2 weeks after the initial hemorrhage, whereas the initial focal brain damage was inferior to the SD variables as a predictor for patient outcome. However, the implantation of Wyler-strip electrodes typically requires either a craniotomy or an enlarged burr hole. Neuromonitoring via an enlarged burr hole has been performed in only about 10% of the total patients monitored.

Methods

In the present pilot study, we investigated the feasibility of ECoG monitoring via a less invasive burrhole approach using a Spencer-type electrode array, which was implanted subdurally rather than in the depth of the parenchyma. Seven aSAH patients requiring extraventricular drainage (EVD) were included. For electrode placement, the burr hole over which the EVD was simultaneously placed, was used in all cases. After electrode implantation, continuous, direct current (DC)/alternating current (AC)-ECoG monitoring was performed at bedside in our Neurointensive Care unit. ECoGs were analyzed following the recommendations of the Co-Operative Studies on Brain Injury Depolarizations (COSBID).

Results

Subdural Spencer-type electrode arrays permitted high-quality ECoG recording. During a cumulative monitoring period of 1,194.5 hours and a median monitoring period of 201.3 (interquartile range: 126.1-209.4) hours per patient, 84 SDs were identified. Numbers of SDs, isoelectric SDs and clustered SDs per recording day, and peak total SD-induced depression duration of a recording day were not significantly different from the previously reported results of the prospective, observational, multicenter, cohort, diagnostic phase III trial, DISCHARGE-1. No adverse events related to electrode implantation were noted.

Discussion

In conclusion, our findings support the safety and feasibility of less-invasive subdural electrode implantation for reliable SD-monitoring.

Depth-profile of impairments in endothelin-1 - induced focal cortical ischemia

The development of ischemic lesions has primarily been studied in horizontal cortical space. However, how ischemic lesions develop through the cortical depth remains largely unknown. We explored this question using direct current coupled recordings at different cortical depths using linear arrays of iridium electrodes in the focal epipial endothelin-1 (ET1) ischemia model in the rat barrel cortex. ET1-induced impairments were characterized by a vertical gradient with (i) rapid suppression of the spontaneous activity in the superficial cortical layers at the onset of ischemia, (ii) compartmentalization of spreading depolarizations (SDs) to the deep layers during progression of ischemia, and (iii) deeper suppression of activity and larger histological lesion size in superficial cortical layers. The level of impairments correlated strongly with the rate of spontaneous activity suppression, the rate of SD onset after ET1 application, and the amplitude of giant negative ultraslow potentials (∼-70 mV), which developed during ET1 application and were similar to the tent-shaped ultraslow potentials observed during focal ischemia in the human cortex. Thus, in the epipial ET1 ischemia model, ischemic lesions develop progressively from the surface to the cortical depth, and early changes in electrical activity at the onset of ET1-induced ischemia reliably predict the severity of ischemic damage.

Comparative Use of Contralateral and Sham-Operated Controls Reveals Traces of a Bilateral Genetic Response in the Rat Brain after Focal Stroke

Ischemic stroke is a multifactorial disease with a complex etiology and global consequences. Model animals are widely used in stroke studies. Various controls, either brain samples from sham-operated (SO) animals or symmetrically located brain samples from the opposite (contralateral) hemisphere (CH), are often used to analyze the processes in the damaged (ipsilateral) hemisphere (IH) after focal stroke. However, previously, it was shown that focal ischemia can lead to metabolic and transcriptomic changes not only in the IH but also in the CH. Here, using a transient middle cerebral artery occlusion (tMCAO) model and genome-wide RNA sequencing, we identified 1941 overlapping differentially expressed genes (DEGs) with a cutoff value >1.5 and Padj < 0.05 that reflected the general transcriptome response of IH subcortical cells at 24 h after tMCAO using both SO and CH controls. Concomitantly, 861 genes were differentially expressed in IH vs. SO, whereas they were not vs. the CH control. Furthermore, they were associated with apoptosis, the cell cycle, and neurotransmitter responses. In turn, we identified 221 DEGs in IH vs. CH, which were non-DEGs vs. the SO control. Moreover, they were predominantly associated with immune-related response. We believe that both sets of non-overlapping genes recorded transcriptome changes in IH cells associated with transhemispheric differences after focal cerebral ischemia. Thus, the specific response of the CH transcriptome should be considered when using it as a control in studies of target brain regions in diseases that induce a global bilateral genetic response, such as stroke.

Dynamic Measurements of Cerebral Blood Flow Responses to Cortical Spreading Depolarization in the Murine Endovascular Perforation Subarachnoid Hemorrhage Model

Delayed cerebral ischemia (DCI) is the most severe complication after subarachnoid hemorrhage (SAH), and cortical spreading depolarization (CSD) is believed to play a vital role in it. However, the dynamic changes in cerebral blood flow (CBF) in response to CSD in typical SAH models have not been well investigated. Here, SAH was established in mice with endovascular perforation. Subsequently, the spontaneous CBF dropped instantly and then returned to baseline rapidly. After KCl application to the cortex, subsequent hypoperfusion waves occurred across the groups, while a lower average perfusion level was found in the SAH groups (days 1-7). Moreover, in the SAH groups, the number of CSD decreased within day 7, and the duration and spreading velocity of the CSD increased within day 3 and day 14, respectively. Next, we continuously monitored the local field potential (LFP) in the prefrontal cortex. The results showed that the decrease in the percentage of gamma oscillations lasted throughout the whole process in the SAH group. In the chronic phase after SAH, we found that the mice still had cognitive deficits but experienced no obvious tissue damage. In summary, SAH negatively affects the CBF responses to CSD and the spontaneous LFP activity and causes long-term cognitive deficits in mice. Based on these findings, in the specific phase after SAH, DCI is induced or exacerbated more easily by potential causers of CSD in clinical practice (edema, erythrocytolysis, inflammation), which may lead to neurological deterioration.

Case report: Delayed posttraumatic cortical laminar necrosis secondary to spreading depolarization induced spreading ischemia from old subarachnoid hemorrhage

Cortical laminar necrosis usually occurs secondary to infarcts or hypoxia, however other causes, including hypoglycemia, status epilepticus and immunosuppressive therapy have been reported. To our knowledge, CLN is not a phenomenon expected in the case of trauma. We report a unique case of delayed post-traumatic CLN which occurred 30 days after the initial trauma, without any proven cause apart from possible spreading depolarization induced spreading ischemia from adjacent subarachnoid hemorrhage with distinct radiologic features.

Spreading depolarizations in ischaemia after subarachnoid haemorrhage, a diagnostic phase III study

Focal brain damage after aneurysmal subarachnoid haemorrhage predominantly results from intracerebral haemorrhage, and early and delayed cerebral ischaemia. The prospective, observational, multicentre, cohort, diagnostic phase III trial, DISCHARGE-1, primarily investigated whether the peak total spreading depolarization-induced depression duration of a recording day during delayed neuromonitoring (delayed depression duration) indicates delayed ipsilateral infarction. Consecutive patients (n = 205) who required neurosurgery were enrolled in six university hospitals from September 2009 to April 2018. Subdural electrodes for electrocorticography were implanted. Participants were excluded on the basis of exclusion criteria, technical problems in data quality, missing neuroimages or patient withdrawal (n = 25). Evaluators were blinded to other measures. Longitudinal MRI, and CT studies if clinically indicated, revealed that 162/180 patients developed focal brain damage during the first 2 weeks. During 4.5 years of cumulative recording, 6777 spreading depolarizations occurred in 161/180 patients and 238 electrographic seizures in 14/180. Ten patients died early; 90/170 developed delayed infarction ipsilateral to the electrodes. Primary objective was to investigate whether a 60-min delayed depression duration cut-off in a 24-h window predicts delayed infarction with >0.60 sensitivity and >0.80 specificity, and to estimate a new cut-off. The 60-min cut-off was too short. Sensitivity was sufficient [= 0.76 (95% confidence interval: 0.65-0.84), P = 0.0014] but specificity was 0.59 (0.47-0.70), i.e. <0.80 (P < 0.0001). Nevertheless, the area under the receiver operating characteristic (AUROC) curve of delayed depression duration was 0.76 (0.69-0.83, P < 0.0001) for delayed infarction and 0.88 (0.81-0.94, P < 0.0001) for delayed ischaemia (reversible delayed neurological deficit or infarction). In secondary analysis, a new 180-min cut-off indicated delayed infarction with a targeted 0.62 sensitivity and 0.83 specificity. In awake patients, the AUROC curve of delayed depression duration was 0.84 (0.70-0.97, P = 0.001) and the prespecified 60-min cut-off showed 0.71 sensitivity and 0.82 specificity for reversible neurological deficits. In multivariate analysis, delayed depression duration (β = 0.474, P < 0.001), delayed median Glasgow Coma Score (β = -0.201, P = 0.005) and peak transcranial Doppler (β = 0.169, P = 0.016) explained 35% of variance in delayed infarction. Another key finding was that spreading depolarization-variables were included in every multiple regression model of early, delayed and total brain damage, patient outcome and death, strongly suggesting that they are an independent biomarker of progressive brain injury. While the 60-min cut-off of cumulative depression in a 24-h window indicated reversible delayed neurological deficit, only a 180-min cut-off indicated new infarction with >0.60 sensitivity and >0.80 specificity. Although spontaneous resolution of the neurological deficit is still possible, we recommend initiating rescue treatment at the 60-min rather than the 180-min cut-off if progression of injury to infarction is to be prevented.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

Spatiotemporal Patterns of Spreading Depolarization and its Correlation with Brain Injury During the Acute Stage of Subarachnoid Hemorrhage in Mice

OBJECTIVE

Spreading depolarization (SD) has been regarded as one cause of neuronal injury in subarachnoid hemorrhage (SAH). However, SD in the hyperacute phase of SAH is still unclear. The objective of this study was to detect real-time spatial-temporal patterns of SD, assess the effect of SD on cerebral blood flow, and test the relationship between SD and brain injury in the acute phase of SAH.

METHODS

Twenty-eight mice were separated into two groups: 16 animals in the SAH group and 12 animals in the sham group. Experimental SAH was done with an endovascular filament perforation model. Changes in optical reflection were registered with intrinsic optical signal imaging (IOSI) after SAH. Spatial-temporal patterns of SDs were analyzed and brain injury including brain edema and infarction was tested.

RESULTS

Totally, 117 SDs occurred after SAH. According to the hemodynamic response and duration, SDs could be classified into Type I (short SD), Type II (intermediate SD), and Type III (persistent SD). Most of SDs originated from the somatosensory and visual cortex. SDs demonstrated distinct spreading patterns. Moreover, the number and duration of SDs associated with brain water content (p < 0.05, p < 0.01). SDs, especially, persistent SDs associated with infarct volume in the hyperacute phase of SAH (p < 0.001, p < 0.001).

CONCLUSION

Our results suggest that SD occurs with a high incidence during the acute stage of SAH in mice. And the lissencephalic mouse brain is capable of different SD propagation patterns. Additionally, SD may aggravate brain edema and induce brain infarction, contributing to early brain injury after SAH.

Intracranial Venous Alteration in Patients With Aneurysmal Subarachnoid Hemorrhage: Protocol for the Prospective and Observational SAH Multicenter Study (SMS)

Background

Arterial vasospasm has been ascribed as the responsible etiology of delayed cerebral infarction in patients with aneurysmal subarachnoid hemorrhage (aSAH), but other neurovascular structures may be involved. We present the protocol for a multicenter, prospective, observational study focused on analyzing morphological changes in cerebral veins of patients with aSAH.

Methods and Analysis

In a retrospective arm, we will collect head arterial and venous CT angiograms (CTA) of 50 patients with aSAH and 50 matching healthy controls at days 0–2 and 7–10, comparing morphological venous changes. A multicenter prospective observational study will follow. Patients aged ≥18 years of any gender with aSAH will be enrolled at 9 participating centers based on the predetermined eligibility criteria. A sample size of 52 aSAH patients is expected, and 52 healthy controls matched per age, gender, and comorbidities will be identified. For each patient, sequential CTA will be conducted upon admission (day 0–2), at 7–10 days, and at 14–21 days after aSAH, evaluating volumes and morphology of the cerebral deep veins and main cortical veins. One specialized image collecting center will analyze all anonymized CTA scans, performing volumetric calculation of targeted veins. Morphological venous changes over time will be evaluated using the Dice coefficient and the Jaccard index and scored using the Boeckh–Behrens system. Morphological venous changes will be correlated to clinical outcomes and compared between patients with aSAH and healthy-controls, and among groups based on surgical/endovascular treatments for aSAH.

Ethics and Dissemination

This protocol has been approved by the ethics committee and institutional review board of Ethikkommission, SALK, Salzburg, Austria, and will be approved at all participating sites. The study will comply with the Declaration of Helsinki. Written informed consent will be obtained from all enrolled patients or their legal tutors. We will present our findings at academic conferences and peer-reviewed journals.

Approved Protocol Version and Registration

Version 2, 09 June 2021.

Trigeminal Nerve Stimulation Improves Cerebral Macrocirculation and Microcirculation After Subarachnoid Hemorrhage: An Exploratory Study

BACKGROUND

Delayed cerebral ischemia (DCI) is the most consequential secondary insult after aneurysmal subarachnoid hemorrhage (SAH). It is a multifactorial process caused by a combination of large artery vasospasm and microcirculatory dysregulation. Despite numerous efforts, no effective therapeutic strategies are available to prevent DCI. The trigeminal nerve richly innervates cerebral blood vessels and releases a host of vasoactive agents upon stimulation. As such, electrical trigeminal nerve stimulation (TNS) has the capability of enhancing cerebral circulation.

OBJECTIVE

To determine whether TNS can restore impaired cerebral macrocirculation and microcirculation in an experimental rat model of SAH.

METHODS

The animals were randomly assigned to sham-operated, SAH-control, and SAH-TNS groups. SAH was induced by endovascular perforation on Day 0, followed by KCl-induced cortical spreading depolarization on day 1, and sample collection on day 2. TNS was delivered on day 1. Multiple end points were assessed including cerebral vasospasm, microvascular spasm, microthrombosis, calcitonin gene-related peptide and intercellular adhesion molecule-1 concentrations, degree of cerebral ischemia and apoptosis, and neurobehavioral outcomes.

RESULTS

SAH resulted in significant vasoconstriction in both major cerebral vessels and cortical pial arterioles. Compared with the SAH-control group, TNS increased lumen diameters of the internal carotid artery, middle cerebral artery, and anterior cerebral artery, and decreased pial arteriolar wall thickness. Additionally, TNS increased cerebrospinal fluid calcitonin gene-related peptide levels, and decreased cortical intercellular adhesion molecule-1 expression, parenchymal microthrombi formation, ischemia-induced hypoxic injury, cellular apoptosis, and neurobehavioral deficits.

CONCLUSION

Our results suggest that TNS can enhance cerebral circulation at multiple levels, lessen the impact of cerebral ischemia, and ameliorate the consequences of DCI after SAH.

Numerical Simulation of Concussive-Generated Cortical Spreading Depolarization to Optimize DC-EEG Electrode Spacing for Noninvasive Visual Detection

BACKGROUND

Cortical spreading depolarization (SD) is a propagating depolarization wave of neurons and glial cells in the cerebral gray matter. SD occurs in all forms of severe acute brain injury, as documented by using invasive detection methods. Based on many experimental studies of mechanical brain deformation and concussion, the occurrence of SDs in human concussion has often been hypothesized. However, this hypothesis cannot be confirmed in humans, as SDs can only be detected with invasive detection methods that would require either a craniotomy or a burr hole to be performed on athletes. Typical electroencephalography electrodes, placed on the scalp, can help detect the possible presence of SD but have not been able to accurately and reliably identify SDs.

METHODS

To explore the possibility of a noninvasive method to resolve this hurdle, we developed a finite element numerical model that simulates scalp voltage changes that are induced by a brain surface SD. We then compared our simulation results with retrospectively evaluated data in patients with aneurysmal subarachnoid hemorrhage from Drenckhahn et al. (Brain 135:853, 2012).

RESULTS

The ratio of peak scalp to simulated peak cortical voltage, Vscalp/Vcortex, was 0.0735, whereas the ratio from the retrospectively evaluated data was 0.0316 (0.0221, 0.0527) (median [1st quartile, 3rd quartile], n = 161, p < 0.001, one sample Wilcoxon signed-rank test). These differing values provide validation because their differences can be attributed to differences in shape between concussive SDs and aneurysmal subarachnoid hemorrhage SDs, as well as the inherent limitations in human study voltage measurements. This simulated scalp surface potential was used to design a virtual scalp detection array. Error analysis and visual reconstruction showed that 1 cm is the optimal electrode spacing to visually identify the propagating scalp voltage from a cortical SD. Electrode spacings of 2 cm and above produce distorted images and high errors in the reconstructed image.

CONCLUSIONS

Our analysis suggests that concussive (and other) SDs can be detected from the scalp, which could confirm SD occurrence in human concussion, provide concussion diagnosis on the basis of an underlying physiological mechanism, and lead to noninvasive SD detection in the setting of severe acute brain injury.

Therapeutic Approaches for Cerebrovascular Dysfunction After Aneurysmal Subarachnoid Hemorrhage: An Update and Future Perspectives

Aneurysmal subarachnoid hemorrhage (aSAH) is a severe subtype of stroke occurring at a relatively young age with a significant socioeconomic impact. Treatment of aSAH includes early aneurysm exclusion, intensive care management, and prevention of complications. Once the aneurysm rupture occurs, blood spreading within the subarachnoid space triggers several molecular pathways causing early brain injury and delayed cerebral ischemia. Pathophysiologic mechanisms underlying brain injury after aSAH are not entirely characterized, reflecting the difficulties in identifying effective therapeutic targets for patients with aSAH. Although the improvements of the last decades in perioperative management, early diagnosis, aneurysm exclusion techniques, and medical treatments have increased survival, vasospasm and delayed cerebral infarction are associated with high mortality and morbidity. Clinical practice can rely on a few specific therapeutic agents, such as nimodipine, a calcium-channel blocker proved to reduce severe neurologic deficits in these patients. Therefore, new pharmacologic approaches are needed to improve the outcome of this life-threatening condition, as well as a tailored rehabilitation plan to maintain the quality of life in aSAH survivors. Several clinical trials are investigating the efficacy and safety of emerging drugs, such as magnesium, clazosentan, cilostazol, interleukin 1 receptor antagonists, deferoxamine, erythropoietin, and nicardipine, and continuous lumbar drainage in the setting of aSAH. This narrative review focuses on the most promising therapeutic interventions after aSAH.

Migraine Aura, Transient Ischemic Attacks, Stroke, and Dying of the Brain Share the Same Key Pathophysiological Process in Neurons Driven by Gibbs–Donnan Forces, Namely Spreading Depolarization

Neuronal cytotoxic edema is the morphological correlate of the near-complete neuronal battery breakdown called spreading depolarization, or conversely, spreading depolarization is the electrophysiological correlate of the initial, still reversible phase of neuronal cytotoxic edema. Cytotoxic edema and spreading depolarization are thus different modalities of the same process, which represents a metastable universal reference state in the gray matter of the brain close to Gibbs–Donnan equilibrium. Different but merging sections of the spreading-depolarization continuum from short duration waves to intermediate duration waves to terminal waves occur in a plethora of clinical conditions, including migraine aura, ischemic stroke, traumatic brain injury, aneurysmal subarachnoid hemorrhage (aSAH) and delayed cerebral ischemia (DCI), spontaneous intracerebral hemorrhage, subdural hematoma, development of brain death, and the dying process during cardio circulatory arrest. Thus, spreading depolarization represents a prime and simultaneously the most neglected pathophysiological process in acute neurology. Aristides Leão postulated as early as the 1940s that the pathophysiological process in neurons underlying migraine aura is of the same nature as the pathophysiological process in neurons that occurs in response to cerebral circulatory arrest, because he assumed that spreading depolarization occurs in both conditions. With this in mind, it is not surprising that patients with migraine with aura have about a twofold increased risk of stroke, as some spreading depolarizations leading to the patient percept of migraine aura could be caused by cerebral ischemia. However, it is in the nature of spreading depolarization that it can have different etiologies and not all spreading depolarizations arise because of ischemia. Spreading depolarization is observed as a negative direct current (DC) shift and associated with different changes in spontaneous brain activity in the alternating current (AC) band of the electrocorticogram. These are non-spreading depression and spreading activity depression and epileptiform activity. The same spreading depolarization wave may be associated with different activity changes in adjacent brain regions. Here, we review the basal mechanism underlying spreading depolarization and the associated activity changes. Using original recordings in animals and patients, we illustrate that the associated changes in spontaneous activity are by no means trivial, but pose unsolved mechanistic puzzles and require proper scientific analysis.

Cortical Spreading Depolarizations in a Mouse Model of Subarachnoid Hemorrhage

BACKGROUND

Cortical spreading depolarizations (CSDs) are associated with worse outcomes in patients with aneurysmal subarachnoid hemorrhage (SAH). Animal models are required to assess whether CSDs can worsen outcomes or are an epiphenomenon; however, little is known about the presence of CSDs in existing animal models. Therefore, we designed a study to determine whether CSDs occur in a mouse model of SAH.

METHODS

A total of 36 mice were included in the study. We used the anterior prechiasmatic injection model of SAH under isoflurane anesthesia. A needle was inserted through the mouse olfactory bulb with the point terminating at the base of the skull, and arterial blood or saline (100 µl) was injected over 10 s. Changes in cerebral blood volume over the entire dorsal cortical surface were assessed with optical intrinsic signal imaging for 5 min following needle insertion.

RESULTS

CSDs occurred in 100% of mice in the hemisphere ipsilateral to olfactory bulb needle insertion (CSD1). Saline-injected mice had 100% survival (n = 10). Blood-injected mice had 88% survival (n = 23 of 26). A second, delayed, CSD ipsilateral to CSD1 occurred in 31% of blood-injected mice. An increase in the time interval between CSD1 and blood injection was associated with the occurrence of a second CSD in blood-injected mice (mean intervals 26.4 vs. 72.7 s, p < 0.0001, n = 18 and 8). We observed one blood-injected animal with a second CSD in the contralateral hemisphere and observed terminal CSDs in mice that died following SAH injection.

CONCLUSIONS

The prechiasmatic injection model of SAH includes CSDs that occur at the time of needle insertion. The occurrence of subsequent CSDs depends on the timing between CSD1 and blood injection. The mouse prechiasmatic injection model could be considered an SAH plus CSD model of the disease. Further work is needed to determine the effect of multiple CSDs on outcomes following SAH.

An Update on Antioxidative Stress Therapy Research for Early Brain Injury After Subarachnoid Hemorrhage

The main reasons for disability and death in aneurysmal subarachnoid hemorrhage (aSAH) may be early brain injury (EBI) and delayed cerebral ischemia (DCI). Despite studies reporting and progressing when DCI is well-treated clinically, the prognosis is not well-improved. According to the present situation, we regard EBI as the main target of future studies, and one of the key phenotype-oxidative stresses may be called for attention in EBI after laboratory subarachnoid hemorrhage (SAH). We summarized the research progress and updated the literature that has been published about the relationship between experimental and clinical SAH-induced EBI and oxidative stress (OS) in PubMed from January 2016 to June 2021. Many signaling pathways are related to the mechanism of OS in EBI after SAH. Several antioxidative stress drugs were studied and showed a protective response against EBI after SAH. The systematical study of antioxidative stress in EBI after laboratory and clinical SAH may supply us with new therapies about SAH.

The management of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a rare event affecting relatively young patients therefore leading to a high social impact. The management of SAH follows a biphasic course with early brain injuries in the first 72 hours followed by a phase at risk of secondary deterioration due to delayed cerebral ischemia (DCI) in 20 to 30% patients. Cerebral infarction from DCI is the most preventable cause of mortality and morbidity after SAH. DCI prevention, early detection and treatment is therefore advocated. Formerly limited to the occurrence of vasospasm, DCI is now associated with multiple pathophysiological processes involving for instance the macrocirculation, the microcirculation, neurovascular units, and inflammation. Therefore, the therapeutic targets and management strategies are also evolving and are not only focused on proximal vasospasm. In this review, we describe the current knowledge of DCI pathophysiology. We then discuss the diagnosis strategies that may guide physicians at the bedside with a multimodal approach in the unconscious patient. We will present the prevention strategies that have proven efficient as well as future targets and present the therapeutic approach that is currently being developed when a DCI occurs.

Phase 1/2a Trial of ISPASM

BACKGROUND AND PURPOSE

Microthrombosis could play a role in delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. Tirofiban has shown promising results in reducing delayed cerebral ischemia in retrospective studies. However, the safety of using tirofiban in aneurysmal subarachnoid hemorrhage is not rigorously established.

METHODS

A phase 1/2a double-blinded randomized controlled trial (2:1 randomization) to assess the safety of a 7-day intravenous infusion of tirofiban compared with placebo, in patients with aneurysmal subarachnoid hemorrhage treated with ventriculostomy placed in the operative room and coiling was conducted. The primary end point was any intracranial hemorrhage during the hospital stay. The secondary end points were: incidence of radiographic and clinical vasospasm, incidence of delayed cerebral ischemia, and incidence of cerebral ischemic changes noted on magnetic resonance imaging or computed tomography.

RESULTS

Eighteen patients received intravenous tirofiban and 12 received placebo. There was no difference in baseline characteristics except for higher male proportions in the tirofiban group. There was no difference in death, in development of new or change in existing intracranial hemorrhages, in thrombocytopenia, and need for shunts in the two arms. However, the tirofiban arm had a lower incidence of delayed cerebral ischemia compared with placebo (6% [1/18] versus 33% [4/12]; P=0.04), and less radiographic vasospasm as detected by catheter angiogram or computed tomography angiography (P=0.01) and computed tomography perfusion (P=0.01).

CONCLUSIONS

The above preliminary results support proceeding with further testing of the safety and efficacy of 7-day intravenous infusion of tirofiban in a pragmatic (placing external ventricular drain by the bedside), multicenter setting, and using a larger population. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03691727.

Spreading Diffusion-Restriction Events in the Gyrencephalic Brain After Subarachnoid Hemorrhage Revealed by Continuous Magnetic Resonance Imaging

BACKGROUND

How widely spreading depolarizations (SDs) propagate through the gyrencephalic brain, including sulci and deeper cortical areas, remains an important clinical question. Here, we investigated SDs that occur spontaneously after subarachnoid placement of autologous blood clots in sulci of the juvenile swine brain.

METHODS

To investigate the three-dimensional spread of waves, animals underwent continuous diffusion-weighted magnetic resonance imaging (DW-MRI) for up to 6 h following clot placement. SD is the mechanism of the cytotoxic edema of developing infarction that is diagnosed by DW-MRI, and DW-MRI also captures transient diffusion restriction caused by SD in less injured or healthy brains. Here, images (b = 0, 375, and 750) were acquired across five coronal slices with 1.25 × 1.25-mm in-plane resolution and 5-mm slice thickness, and the protocol was repeated every 6.83-9.15 s. Spatial drift correction, temporal smoothing, and signal intensity normalization were applied to generate videos of diffusion signal intensity changes for each coronal slice.

RESULTS

Review of video data from five animals revealed ten discrete events consisting of focal diffusion restriction that propagated through cerebral cortex. All events originated in the cortex surrounding the sulcal clot, either in the gyrus (n = 4) or in the sulcal depth (n = 6). In six cases, two to three independent waves spread simultaneously in medial, lateral, and antero-posterior directions. Waves traveled within sulcal walls, traversed the depths of sulci to re-emerge on the adjacent gyrus, and, in three cases, spread fully around the dorsolateral convexity. One event spread deep to olfactory regions along midline cortex, and no events were observed contralateral to the subarachnoid clot.

CONCLUSIONS

Together, these results suggest that SDs in the injured gyrencephalic brain originate near the injury focus and can spread extensively through the cortex to wide and deep uninjured regions. These findings have implications for transient neurologic deficits in the neurocritically ill patient and relevance to patient monitoring and therapeutics.

Brainstem and Cortical Spreading Depolarization in a Closed Head Injury Rat Model

Traumatic brain injury (TBI) is the leading cause of death in young individuals, and is a major health concern that often leads to long-lasting complications. However, the electrophysiological events that occur immediately after traumatic brain injury, and may underlie impact outcomes, have not been fully elucidated. To investigate the electrophysiological events that immediately follow traumatic brain injury, a weight-drop model of traumatic brain injury was used in rats pre-implanted with epidural and intracerebral electrodes. Electrophysiological (near-direct current) recordings and simultaneous alternating current recordings of brain activity were started within seconds following impact. Cortical spreading depolarization (SD) and SD-induced spreading depression occurred in approximately 50% of mild and severe impacts. SD was recorded within three minutes after injury in either one or both brain hemispheres. Electrographic seizures were rare. While both TBI- and electrically induced SDs resulted in elevated oxidative stress, TBI-exposed brains showed a reduced antioxidant defense. In severe TBI, brainstem SD could be recorded in addition to cortical SD, but this did not lead to the death of the animals. Severe impact, however, led to immediate death in 24% of animals, and was electrocorticographically characterized by non-spreading depression (NSD) of activity followed by terminal SD in both cortex and brainstem.

Characteristics of MRI Findings after Subarachnoid Hemorrhage and D-Dimer as a Predictive Value for Early Brain Injury

BACKGROUND

The pathological mechanisms of early brain injury (EBI) have remained obscure. Several studies have reported on the neuroradiological findings of EBI. However, to our knowledge, no study has attempted to explore the mechanism of EBI after subarachnoid hemorrhage (SAH). Therefore, this study evaluates whether the initial plasma D-dimer levels were associated with EBI, classifies magnetic resonance imaging (MRI) findings, and speculates about the mechanism of EBI.

METHODS

This study included 97 patients hospitalized within 24 h from the onset of nontraumatic SAH. The patients underwent MRI within 0-5 days from onset (before vasospasm) to detect EBI. EBI was radiologically defined as diffusion-weighted imaging (DWI)-positive lesions that appear dark on apparent diffusion coefficient maps, excluding procedure-related lesions. EBI, plasma D-dimer levels, and clinical features were retrospectively investigated.

RESULTS

Elevated D-dimer levels were associated with poor outcomes. Patients with EBI had significantly higher D-dimer levels than those without EBI. EBI was detected in 24 patients (27.3%) of all, and in 22 (45%) of 49 patients with World Federation of Neurosurgical Societies (WFNS) grade 4-5 SAH. EBI was frequently observed in the paramedian frontal lobe. There were several types of the pathology in EBI, including widespread symmetrical cerebral cortex lesions, focal cortex lesions, periventricular injury, and other lesions impossible to classify due to unknown mechanisms such as thrombotic complication and microcirculatory disturbance, ultra-early spasm, and spreading depolarization.

CONCLUSIONS

This study suggests that D-dimer levels predict poor outcomes in patients with SAH and that EBI was associated high D-dimer levels.

Oxygen-Induced and pH-Induced Direct Current Artifacts on Invasive Platinum/Iridium Electrodes for Electrocorticography

BACKGROUND

Spreading depolarization (SD) and the initial, still reversible phase of neuronal cytotoxic edema in the cerebral gray matter are two modalities of the same process. SD may thus serve as a real-time mechanistic biomarker for impending parenchyma damage in patients during neurocritical care. Using subdural platinum/iridium (Pt/Ir) electrodes, SD is observed as a large negative direct current (DC) shift. Besides SD, there are other causes of DC shifts that are not to be confused with SD. Here, we systematically analyzed DC artifacts in ventilated patients by observing changes in the fraction of inspired oxygen. For the same change in blood oxygenation, we found that negative and positive DC shifts can simultaneously occur at adjacent Pt/Ir electrodes.

METHODS

Nurses and intensivists typically increase blood oxygenation by increasing the fraction of inspired oxygen at the ventilator before performing manipulations on the patient. We retrospectively identified 20 such episodes in six patients via tissue partial pressure of oxygen (p_tiO₂) measurements with an intracortical O₂ sensor and analyzed the associated DC shifts. In vitro, we compared Pt/Ir with silver/silver chloride (Ag/AgCl) to assess DC responses to changes in pO₂, pH, or 5-min square voltage pulses and investigated the effect of electrode polarization on pO₂-induced DC artifacts.

RESULTS

Hyperoxygenation episodes started from a p_tiO₂ of 37 (30-40) mmHg (median and interquartile range) reaching 71 (50-97) mmHg. During a total of 20 episodes on each of six subdural Pt/Ir electrodes in six patients, we observed 95 predominantly negative responses in six patients, 25 predominantly positive responses in four patients, and no brain activity changes. Adjacent electrodes could show positive and negative responses simultaneously. In vitro, Pt/Ir in contrast with Ag/AgCl responded to changes in either pO₂ or pH with large DC shifts. In response to square voltage pulses, Pt/Ir falsely showed smaller DC shifts than Ag/AgCl, with the worst performance under anoxia. In response to pO₂ increase, Pt/Ir showed DC positivity when positively polarized and DC negativity when negatively polarized.

CONCLUSIONS

The magnitude of pO₂-induced subdural DC shifts by approximately 6 mV was similar to that of SDs, but they did not show a sequential onset at adjacent recording sites, could be either predominantly negative or positive in contrast with the always negative DC shifts of SD, and were not accompanied by brain activity depression. Opposing polarities of pO₂-induced DC artifacts may result from differences in baseline electrode polarization or subdural p_tiO₂ inhomogeneities relative to subdermal p_tiO₂ at the quasi-reference.

Emerging immune and cell death mechanisms in stroke: Saponins as therapeutic candidates

The complexity of the ischemic cascade is based on the integrated crosstalk of every cell type in the neurovascular unit. Depending on the features of the ischemic insult, several cell death mechanisms are triggered, such as apoptosis, necroptosis, ferroptosis/oxytosis, ETosis or pyroptosis, leading to reactive astrogliosis. However, emerging evidence demonstrates a dual role for the immune system in stroke pathophysiology, where it exerts both detrimental and also beneficial functions. In this review, we discuss the relevance of several cell death modalities and the dual role of the immune system in stroke pathophysiology. We also provide an overview of some emerging immunomodulatory therapeutic strategies, amongst which saponins, which are promising candidates that exert multiple pharmacological effects.

•

Several cell death mechanisms coexist in stroke pathophysiology.

•

Neurons are more vulnerable to necroptosis than glial cells.

•

Inhibitors of receptor-interacting protein kinases and of ferroptosis induce neuroprotection.

•

Saponins exert modulatory effects on inflammation and neuronal cell death in stroke.

Association Between Spreading Depolarization and Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Post Hoc Analysis of a Randomized Trial of the Effect of Cilostazol on Delayed Cerebral Ischemia

BACKGROUND

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) remains an important problem with a complex pathophysiology. We used data from a single-center randomized trial to assess the effect of a phosphodiesterase inhibitor, cilostazol, in patients with aneurysmal SAH to explore the relationships of DCI with vasospasm, spreading depolarization (SD) and microcirculatory disturbance.

METHODS

A post hoc analysis of a single-center, prospective, randomized trial of the effect of cilostazol on DCI and SD after aneurysmal SAH was performed. From all randomized cohorts, patients who underwent both SD monitoring and digital subtraction angiography (DSA) on day 9 ± 2 from onset were included. Cerebral circulation time (CCT), which was divided into proximal CCT and peripheral CCT (as a measure of microcirculatory disturbance), was obtained from DSA. Logistic regression was conducted to determine factors associated with DCI.

RESULTS

Complete data were available for 28 of 50 patients. Of the 28 patients, 8 (28.5%) had DCI during the study period. Multivariate analysis indicated a strong association between the number of SDs on the day DSA was performed (i.e., a delayed time point after SAH onset) and DCI (odds ratio 2.064, 95% confidence interval 1.045-4.075, P = 0.037, area under the curve 0.836), whereas the degree of angiographic vasospasm and peripheral CCT were not significant factors for DCI.

CONCLUSIONS

There is a strong association between SD and DCI. Our results suggest that SD is an important therapeutic target and a potentially useful biomarker for DCI.

Higher Serum Levels of Lactate Dehydrogenase Before Microsurgery Predict Poor Outcome of Aneurysmal Subarachnoid Hemorrhage

Introduction: We explored whether higher preoperative serum levels of lactate dehydrogenase (LDH) predicted outcome 3 months after surgery in patients with aneurysmal subarachnoid hemorrhage (aSAH) treated using microsurgical clipping in our institution.

Methods: Patients with aSAH treated at our institution between 2010 and 2018 were enrolled. The following parameters were recorded: age, sex, smoking and drinking history, medical history, Hunt–Hess and Fisher grades, aneurysm location, aneurysm size, surgical treatment, delayed cerebral ischemia (DCI), intracranial infection, hydrocephalus, pneumonia, and preoperative serum LDH levels within 24 h of aSAH. We investigated whether preoperative serum LDH levels were associated with Hunt–Hess grade, Fisher grade, and functional neurological outcome.

Results: In total, 2,054 patients with aSAH were enrolled, 874 of whom were treated using microsurgical clipping. The average serum LDH level (U/L) was significantly lower in the good outcome group (180.096 ± 50.237) than in the poor outcome group (227.554 ± 83.002; p < 0.001). After propensity score matching, the average serum LDH level (U/L) was still lower in the good outcome group (205.356 ± 76.785) than in the poor outcome group (227.119 ± 86.469; p = 0.029). The area under the receiver operating characteristic (ROC) curve was 0.702 (95% confidence interval [CI]: 0.650–0.754; p < 0.001). Based on the ROC curve, the optimal cutoff value for serum LDH levels as a predictor of poor 3-month outcome (modified Rankin Scale score > 2) was 201.5 U/L. The results revealed that Hunt–Hess grade, Fisher grade, DCI, pneumonia, and serum LDH (>201.5 U/L) were significantly associated with poor outcome. After propensity score matching, serum LDH levels > 201.5 U/L were still considered an independent risk factor for poor outcome (odds ratio: 2.426, 95% CI = 1.378–4.271, p = 0.002). Serum LDH levels were associated with Hunt–Hess and Fisher grades and were correlated with functional neurological outcomes (p < 0.001).

Conclusions: Our findings showed that higher preoperative serum levels of LDH correlated with Hunt–Hess grade, Fisher grade, and neurological functional outcome, and predicted the outcome of aSAH treated by microsurgical clipping at 3 months, which was involved in the related mechanisms of early brain injury and showed its potential clinical significance in patients with aSAH.

EP2 Antagonists (2011-2021): A Decade's Journey from Discovery to Therapeutics

In the wake of health disasters associated with the chronic use of cyclooxygenase-2 (COX-2) inhibitor drugs, it has been widely proposed that modulation of downstream prostanoid synthases or receptors might provide more specificity than simply shutting down the entire COX cascade for anti-inflammatory benefits. The pathogenic actions of COX-2 have long been thought attributable to the prostaglandin E2 (PGE2) signaling through its Gαs-coupled EP2 receptor subtype; however, the truly selective EP2 antagonists did not emerge until 2011. These small molecules provide game-changing tools to better understand the EP2 receptor in inflammation-associated conditions. Their applications in preclinical models also reshape our knowledge of PGE2/EP2 signaling as a node of inflammation in health and disease. As we celebrate the 10-year anniversary of this breakthrough, the exploration of their potential as drug candidates for next-generation anti-inflammatory therapies has just begun. The first decade of EP2 antagonists passes, while their future looks brighter than ever.

Full-Band EEG Recordings Using Hybrid AC/DC-Divider Filters

Full-band DC recordings enable recording of slow electrical brain signals that are severely compromised during conventional AC recordings. However, full-band DC recordings may be limited by the amplifier's dynamic input range and the loss of small amplitude high-frequency signals. Recently, Neuralynx has proposed full-band recordings with inverse filtering for signal reconstruction based on hybrid AC/DC-divider RRC filters that enable only partial suppression of DC signals. However, the quality of signal reconstruction for biological signals has not yet been assessed. Here, we propose a novel digital inverse filter based on a mathematical model describing RRC filter properties, which provides high computational accuracy and versatility. Second, we propose procedures for the evaluation of the inverse filter coefficients, adapted for each recording channel to minimize the error caused by the deviation of the real values of the RRC filter elements from their nominal values. We demonstrate that this approach enables near 99% reconstruction quality of high-potassium-induced cortical spreading depolarizations (SDs), endothelin-induced ischemic negative ultraslow potentials (NUPs), and whole-cell recordings of membrane potential using RRC filters. The quality of the reconstruction was significantly higher than with the existing inverse filtering procedures. Thus, RRC filters with inverse filtering are optimal for full-band EEG recordings in various applications.

Cerebral Autoregulation in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype with a high rate of mortality and morbidity. The poor clinical outcome can be attributed to the biphasic course of the disease: even if the patient survives the initial bleeding emergency, delayed cerebral ischemia (DCI) frequently follows within 2 weeks time and levies additional serious brain injury. Current therapeutic interventions do not specifically target the microvascular dysfunction underlying the ischemic event and as a consequence, provide only modest improvement in clinical outcome. SAH perturbs an extensive number of microvascular processes, including the “automated” control of cerebral perfusion, termed “cerebral autoregulation.” Recent evidence suggests that disrupted cerebral autoregulation is an important aspect of SAH-induced brain injury. This review presents the key clinical aspects of cerebral autoregulation and its disruption in SAH: it provides a mechanistic overview of cerebral autoregulation, describes current clinical methods for measuring autoregulation in SAH patients and reviews current and emerging therapeutic options for SAH patients. Recent advancements should fuel optimism that microvascular dysfunction and cerebral autoregulation can be rectified in SAH patients.

Nitric Oxide-Based Treatment of Poor-Grade Patients After Severe Aneurysmal Subarachnoid Hemorrhage

Background

Patients with aneurysmal subarachnoid hemorrhage (aSAH) require close treatment in neuro intensive care units (NICUs). The treatments available to counteract secondary deterioration and delayed ischemic events remain restricted; moreover, available neuro-monitoring of comatose patients is undependable. In comatose patients, clinical signs are hidden, and timing interventions to prevent the evolution of a perfusion disorder in response to fixed ischemic brain damage remain a challenge for NICU teams. Consequently, comatose patients often suffer secondary brain infarctions. The outcomes for long-term intubated patients w/wo pupil dilatation are the worst, with only 10% surviving. We previously added two nitroxide (NO) donors to the standard treatment: continuous intravenous administration of Molsidomine in patients with mild-to-moderate aSAH and, if required as a supplement, intraventricular boluses of sodium nitroprusside (SNP) in high-risk patients to overcome the so-called NO-sink effect, which leads to vasospasm and perfusion disorders. NO boluses were guided by clinical status and promptly reversed recurrent episodes of delayed ischemic neurological deficit. In this study, we tried to translate this concept, the initiation of intraventricular NO application on top of continuous Molsidomine infusion, from awake to comatose patients who lack neurological–clinical monitoring but are primarily monitored using frequently applied transcranial Doppler (TCD).

Methods

In this observational, retrospective, nonrandomized feasibility study, 18 consecutive aSAH comatose/intubated patients (Hunt and Hess IV/V with/without pupil dilatation) whose poor clinical status precluded clinical monitoring received standard neuro-intensive care, frequent TCD monitoring, continuous intravenous Molsidomine plus intraventricular SNP boluses after TCD-confirmed macrospasm during the daytime and on a fixed nighttime schedule.

Results

Very likely associated with the application of SNP, which is a matter of further investigation, vasospasm-related TCD findings promptly and reliably reversed or substantially weakened (p < 0.0001) afterward. Delayed cerebral ischemia (DCI) occurred only during loose, low-dose or interrupted treatment (17% vs. an estimated 65% with secondary infarctions) in 17 responders. However, despite their worse initial condition, 29.4% of the responders survived (expected 10%) and four achieved Glasgow Outcome Scale Extended (GOSE) 8–6, modified Rankin Scale (mRS) 0–1 or National Institutes of Health Stroke Scale (NIHSS) 0–2.

Conclusions

Even in comatose/intubated patients, TCD-guided dual-compartment administration of NO donors probably could reverse macrospasm and seems to be feasible. The number of DCI was much lower than expected in this specific subgroup, indicating that this treatment possibly provides a positive impact on outcomes. A randomized trial should verify or falsify our results.

Rapid hematoma growth triggers spreading depolarizations in experimental intracortical hemorrhage

Recurrent waves of spreading depolarization (SD) occur in brain injury and are thought to affect outcomes. What triggers SD in intracerebral hemorrhage is poorly understood. We employed intrinsic optical signaling, laser speckle flowmetry, and electrocorticography to elucidate the mechanisms triggering SD in a collagenase model of intracortical hemorrhage in mice. Hematoma growth, SD occurrence, and cortical blood flow changes were tracked. During early hemorrhage (0-4 h), 17 out of 38 mice developed SDs, which always originated from the hematoma. No SD was detected at late time points (8-52 h). Neither hematoma size, nor peri-hematoma perfusion were associated with SD occurrence. Further, arguing against ischemia as a trigger factor, normobaric hyperoxia did not inhibit SD occurrence. Instead, SDs always occurred during periods of rapid hematoma growth, which was two-fold faster immediately preceding an SD compared with the peak growth rates in animals that did not develop any SDs. Induced hypertension accelerated hematoma growth and resulted in a four-fold increase in SD occurrence compared with normotensive animals. Altogether, our data suggest that spontaneous SDs in this intracortical hemorrhage model are triggered by the mechanical distortion of tissue by rapidly growing hematomas.

Cerebral Amyloid Angiopathy-Related Transient Focal Neurologic Episodes

Transient focal neurologic episodes (TFNEs) are brief disturbances in motor, somatosensory, visual, or language functions that can occur in patients with cerebral amyloid angiopathy (CAA) and may be difficult to distinguish from TIAs or other transient neurologic syndromes. They herald a high rate of future lobar intracerebral hemorrhage, making it imperative to differentiate them from TIAs to avoid potentially dangerous use of antithrombotic drugs. Cortical spreading depression or depolarization triggered by acute or chronic superficial brain bleeding, a contributor to brain injury in other neurologic diseases, may be the underlying mechanism. This review discusses diagnosis, pathophysiology, and management of CAA-related TFNEs.

Cortical spreading depression aggravates early brain injury in a mouse model of subarachnoid hemorrhage

Cortical spreading depression (CSD) has been observed during the early phase of subarachnoid hemorrhage (SAH). However, the effect of CSD on the cerebral blood flow (CBF) and cerebral oxyhemoglobin (CHbO) during the early phase of SAH has not yet been assessed directly. We, therefore, used laser speckle imaging and optical intrinsic sinal imaging to record CBF and CHbO during CSD and cerebral cortex perfusion (CCP) at 24 hours after CSD in a mouse model of SAH. SAH was induced by blood injection into the prechiasmatic cistern. When CSD occurred, the change trend of CBF and CHbO in Sham group and SAH group was the same, but ischemia and hypoxia in SAH group was more significant. At 24 hours after SAH, the CCP of CSD group was lower than that of no CSD group, and the neurological function score of CSD group was lower. We conclude that induction of CSD further aggravates cerebral ischemia and worsens neurological dysfunction in the early stage of experimental SAH. Our study underscores the consequence of CSD in the development of early brain injury after SAH.

Perfusion-weighted MRI in cerebral amyloid angiopathy-related transient focal neurological episodes

INTRODUCTION

Sporadic cerebral amyloid angiopathy (CAA) is a common age-related cerebral small vessel disease characterized by progressive ß-amyloid deposition in the walls of small cortical arteries, arterioles, and capillaries in the cerebral cortex and overlying leptomeninges. CAA-related transient focal neurological episodes (CAA-TFNEs) represent a challenging clinical feature interesting from a pathophysiological point of view.

CASE REPORT

Here we present two cases of CAA-TFNEs in which we performed functional imaging with perfusion-weighted imaging MR and brain 18 F-FDG PET. In both cases, we found a topographic relationship between the involved cortical areas and the clinical expression of CAA-TFNEs. Cortical superficial siderosis in the first case and a convexity subarachnoid hemorrhage in the second case were found in the contralateral rolandic area corresponding to the clinical symptoms. The same areas showed a reduction of rCBV and rCBF on perfusion-weighted MR and were also associated in one case with hypometabolism on 18 F-FDG PET.

DISCUSSION

These new findings strengthen the hypothesis that CAA involves the superficial leptomeningeal arteries but also the short penetrating arterioles reaching different depths in the cortex generating hypoperfusion and altered vascular reactivity and consequently reduced neuronal activity.

CONCLUSION

Understanding CAA-TFNEs is pivotal because they carry a very high risk of subsequent lobar intracerebral hemorrhage but are frequently misdiagnosed as TIAs and treated with antithrombotics enhancing the bleeding risk associated with CAA.

Neuropathological correlates of cortical superficial siderosis in cerebral amyloid angiopathy

Cortical superficial siderosis is an established haemorrhagic neuroimaging marker of cerebral amyloid angiopathy. In fact, cortical superficial siderosis is emerging as a strong independent risk factor for future lobar intracerebral haemorrhage. However, the underlying neuropathological correlates and pathophysiological mechanisms of cortical superficial siderosis remain elusive. Here we use an in vivo MRI, ex vivo MRI, histopathology approach to assess the neuropathological correlates and vascular pathology underlying cortical superficial siderosis. Fourteen autopsy cases with cerebral amyloid angiopathy (mean age at death 73 years, nine males) and three controls (mean age at death 91 years, one male) were included in the study. Intact formalin-fixed cerebral hemispheres were scanned on a 3 T MRI scanner. Cortical superficial siderosis was assessed on ex vivo gradient echo and turbo spin echo MRI sequences and compared to findings on available in vivo MRI. Subsequently, 11 representative areas in four cases with available in vivo MRI scans were sampled for histopathological verification of MRI-defined cortical superficial siderosis. In addition, samples were taken from predefined standard areas of the brain, blinded to MRI findings. Serial sections were stained for haematoxylin and eosin and Perls' Prussian blue, and immunohistochemistry was performed against amyloid-β and GFAP. Cortical superficial siderosis was present on ex vivo MRI in 8/14 cases (57%) and 0/3 controls (P = 0.072). Histopathologically, cortical superficial siderosis corresponded to iron-positive haemosiderin deposits in the subarachnoid space and superficial cortical layers, indicative of chronic bleeding events originating from the leptomeningeal vessels. Increased severity of cortical superficial siderosis was associated with upregulation of reactive astrocytes. Next, cortical superficial siderosis was assessed on a total of 65 Perls'-stained sections from MRI-targeted and untargeted sampling combined in cerebral amyloid angiopathy cases. Moderate-to-severe cortical superficial siderosis was associated with concentric splitting of the vessel wall (an advanced form of cerebral amyloid angiopathy-related vascular damage) in leptomeningeal vessels (P < 0.0001), but reduced cerebral amyloid angiopathy severity in cortical vessels (P = 0.048). In terms of secondary tissue injury, moderate-to-severe cortical superficial siderosis was associated with the presence of microinfarcts (P = 0.025), though not microbleeds (P = 0.973). Collectively, these data suggest that cortical superficial siderosis on MRI corresponds to iron-positive deposits in the superficial cortical layers, representing the chronic manifestation of bleeding episodes from leptomeningeal vessels. Cortical superficial siderosis appears to be the result of predominantly advanced cerebral amyloid angiopathy of the leptomeningeal vessels and may trigger secondary ischaemic injury in affected areas.

The role of spreading depolarizations and electrographic seizures in early injury progression of the rat photothrombosis stroke model

Spreading depolarization (SD) and seizures are pathophysiological events associated with cerebral ischemia. Here, we investigated their role for injury progression in the cerebral cortex. Cerebral ischemia was induced in anesthetized male Wistar rats using the photothrombosis (PT) stroke model. SD and spontaneous neuronal activity were recorded in the presence of either urethane or ketamine/xylazine anesthesia. Blood-brain barrier (BBB) permeability, cerebral perfusion, and cellular damage were assessed through a cranial window and repeated intravenous injection of fluorescein sodium salt and propidium iodide until 4 h after PT. Neuronal injury and early lesion volume were quantified by stereological cell counting and manual and automated assessment of ex vivo T2-weighted magnetic resonance imaging. Onset SDs originated at the thrombotic core and invaded neighboring cortex, whereas delayed SDs often showed opposite propagation patterns. Seizure induction by 4-aminopyridine caused no increase in lesion volume or neuronal injury in urethane-anesthetized animals. Ketamine/xylazine anesthesia was associated with a lower number of onset SDs, reduced lesion volume, and neuronal injury despite a longer duration of seizures. BBB permeability increase inversely correlated with the number of SDs at 3 and 4 h after PT. Our results provide further evidence that ketamine may counteract the early progression of ischemic injury.