Current management of delayed cerebral ischemia: update from results of recent clinical trials

PARP-1 dependent cell death pathway (Parthanatos) mediates early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a neurological condition with high mortality and poor prognosis, and there are currently no effective therapeutic drugs available. Poly (ADP-ribose) polymerase 1 (PARP-1) dependent cell death pathway-parthanatos is closely associated with stroke. We investigated improvements in neurological function, oxidative stress, blood-brain barrier and parthanatos-related protein expression in rats with SAH after intraperitoneal administration of PARP-1 inhibitor (AG14361). Our study found that the expression of parthanatos-related proteins was significantly increased after SAH. Immunofluorescence staining showed increased expression of apoptosis-inducing factor (AIF) in the nucleus after SAH. Administration of PARP-1 inhibitor significantly reduced malondialdehyde (MDA) level and the expression of parthanatos-related proteins. Immunofluorescence staining showed that PARP-1 inhibitor reduced the expression of 8-hydroxy-2' -deoxyguanosine (8-OHdG) and thus reduced oxidative stress. Moreover, PARP-1 inhibitor could inhibit inflammation-associated proteins level and neuronal apoptosis, protect the blood-brain barrier and significantly improve neurological function after SAH. These results suggest that PARP-1 inhibitor can significantly improve SAH, and the underlying mechanism may be through inhibiting parthanatos pathway.

Trends in Delayed Cerebral Ischemia After Subarachnoid Hemorrhage Over Past 10 years: A Bibliometric Analysis

BACKGROUND

As a common hemorrhagic cerebrovascular disease, subarachnoid hemorrhage (SAH) has high mortality and disability. Delayed cerebral ischemia (DCI) is among the major complications after SAH, severely affecting the patient prognosis. Through bibliometric analysis, this study investigated the global research status, trends, and hotspots of DCI after SAH from 2013 to 2022, providing a scientific reference for researchers in this field.

METHODS

We searched the Web of Science Core Collection for articles and associated records from 2013 to 2022. The data were analyzed and presented using VOSviewer software.

RESULTS

This study covered 3436 articles, and the number of publications issued by DCI after SAH study increased annually. The United States published the most papers and had the highest number of citations. Harvard University and World Neurosurgery were the institutions and journals with the most published papers. Keyword analysis indicated that the recent research on DCI after SAH has focused on its pathophysiological mechanisms.

CONCLUSIONS

DCI after SAH has drawn increasing interest in academic circles during the past decade. This study presented an objective, systematic, and comprehensive analysis of the literature on DCI after SAH. Currently, the hotspots in this field focus on pathophysiological mechanisms.

Propofol Affords No Protection against Delayed Cerebral Ischemia in a Mouse Model of Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) is an important contributor to poor outcomes in aneurysmal subarachnoid hemorrhage (SAH) patients. We previously showed that volatile anesthetics such as isoflurane, sevoflurane and desflurane provided robust protection against SAH-induced DCI, but the impact of a more commonly used intravenous anesthetic agent, propofol, is not known. The goal of our current study is to examine the neurovascular protective effects of propofol on SAH-induced DCI. Twelve-week-old male wild-type mice were utilized for the study. Mice underwent endovascular perforation SAH or sham surgery followed one hour later by propofol infusion through the internal jugular vein (2 mg/kg/min continuous intravenous infusion). Large artery vasospasm was assessed three days after SAH. Neurological outcome assessment was performed at baseline and then daily until animal sacrifice. Statistical analysis was performed via one-way ANOVA and two-way repeated measures ANOVA followed by the Newman-Keuls multiple comparison test with significance set at p < 0.05. Intravenous propofol did not provide any protection against large artery vasospasm or sensory-motor neurological deficits induced by SAH. Our data show that propofol did not afford significant protection against SAH-induced DCI. These results are consistent with recent clinical studies that suggest that the neurovascular protection afforded by anesthetic conditioning is critically dependent on the class of anesthetic agent.

Intraoperative Blood Pressure and Carbon Dioxide Values during Aneurysmal Repair and the Outcomes after Aneurysmal Subarachnoid Hemorrhage

Cerebral autoregulation impairment is a critical aspect of subarachnoid hemorrhage (SAH)-induced secondary brain injury and is also shown to be an independent predictor of delayed cerebral ischemia (DCI) and poor neurologic outcomes. Interestingly, intraoperative hemodynamic and ventilatory parameters were shown to influence patient outcomes after SAH. The aim of the current study was to evaluate the association of intraoperative hypotension and hypocapnia with the occurrence of angiographic vasospasm, DCI, and neurologic outcomes at discharge. Intraoperative data were collected for 390 patients with aneurysmal SAH who underwent general anesthesia for aneurysm clipping or coiling between January 2010 and May 2018. We measured the mean intraoperative blood pressure and end-tidal carbon dioxide (ETCO2), as well as the area under the curve (AUC) for the burden of hypotension: SBP below 100 or MBP below 65 and hypocapnia (ETCO2 < 30), during the intraoperative period. The outcome measures were angiographic vasospasm, DCI, and the neurologic outcomes at discharge as measured by the modified Rankin scale score (an mRS of 0-2 is a good outcome, and 3-6 is a poor outcome). Univariate and logistic regression analyses were performed to evaluate whether blood pressure (BP) and ETCO2 variables were independently associated with outcome measures. Out of 390 patients, 132 (34%) developed moderate-to-severe vasospasm, 114 (29%) developed DCI, and 46% (169) had good neurologic outcomes at discharge. None of the measured intraoperative BP and ETCO2 variables were associated with angiographic vasospasm, DCI, or poor neurologic outcomes. Our study did not identify an independent association between the degree of intraoperative hypotension or hypocapnia in relation to angiographic vasospasm, DCI, or the neurologic outcomes at discharge in SAH patients.

Isoflurane Conditioning-Induced Delayed Cerebral Ischemia Protection in Subarachnoid Hemorrhage-Role of Inducible Nitric Oxide Synthase

Background Recent evidence implicates inflammation as a key driver in delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage (SAH). Inducible nitric oxide synthase (iNOS) is one of the known major mediators of inflammation. We previously showed that an inhalational anesthetic, isoflurane, provides strong protection against delayed cerebral ischemia after SAH. Our current study aims to define the role of iNOS in isoflurane conditioning-induced protection against delayed cerebral ischemia in a mouse model of SAH. Methods and Results The experiments used 10- to 14-week-old male wild-type (C57BL/6) and iNOS global knockout mice. Anesthetic conditioning was initiated 1 hour after SAH with isoflurane 2% for 1 hour. Isoflurane-induced changes in iNOS expression were measured. N-(3-(aminomethyl) benzyl) acetamidine, a highly selective iNOS inhibitor, was injected intraperitoneally immediately after SAH and then daily. Vasospasm, microvessel thrombosis, and neurological assessment was performed. Data were analyzed by 1-way ANOVA and 2-way repeated measures ANOVA followed by Student Newman Keuls comparison test. Statistical significance was set at P<0.05. Isoflurane conditioning downregulated iNOS expression in naïve and SAH mice. N-(3-(aminomethyl) benzyl) acetamidine attenuated large artery vasospasm and microvessel thrombosis and improved neurological deficits in wild-type animals. iNOS knockout mice were significantly resistant to vasospasm, microvessel thrombosis, and neurological deficits induced by SAH. Combining isoflurane with N-(3-(aminomethyl) benzyl) acetamidine did not offer extra protection, nor did treating iNOS knockout mice with isoflurane. Conclusions Isoflurane conditioning-induced delayed cerebral ischemia protection appears to be mediated by downregulating iNOS. iNOS is a potential therapeutic target to improve outcomes after SAH.

Isoflurane Conditioning Provides Protection against Subarachnoid Hemorrhage Induced Delayed Cerebral Ischemia through NF-kB Inhibition

Delayed cerebral ischemia (DCI) is the largest treatable cause of poor outcome after aneurysmal subarachnoid hemorrhage (SAH). Nuclear Factor Kappa-light-chain-enhancer of Activated B cells (NF-kB), a transcription factor known to function as a pivotal mediator of inflammation, is upregulated in SAH and is pathologically associated with vasospasm. We previously showed that a brief exposure to isoflurane, an inhalational anesthetic, provided multifaceted protection against DCI after SAH. The aim of our current study is to investigate the role of NF-kB in isoflurane-conditioning-induced neurovascular protection against SAH-induced DCI. Twelve-week-old wild type male mice (C57BL/6) were divided into five groups: sham, SAH, SAH + Pyrrolidine dithiocarbamate (PDTC, a selective NF-kB inhibitor), SAH + isoflurane conditioning, and SAH + PDTC with isoflurane conditioning. Experimental SAH was performed via endovascular perforation. Anesthetic conditioning was performed with isoflurane 2% for 1 h, 1 h after SAH. Three doses of PDTC (100 mg/kg) were injected intraperitoneally. NF-kB and microglial activation and the cellular source of NF-kB after SAH were assessed by immunofluorescence staining. Vasospasm, microvessel thrombosis, and neuroscore were assessed. NF-kB was activated after SAH; it was attenuated by isoflurane conditioning. Microglia was activated and found to be a major source of NF-kB expression after SAH. Isoflurane conditioning attenuated microglial activation and NF-kB expression in microglia after SAH. Isoflurane conditioning and PDTC individually attenuated large artery vasospasm and microvessel thrombosis, leading to improved neurological deficits after SAH. The addition of isoflurane to the PDTC group did not provide any additional DCI protection. These data indicate isoflurane-conditioning-induced DCI protection after SAH is mediated, at least in part, via downregulating the NF-kB pathway.

Role of lipocalin 2 in stroke

Stroke is the second leading cause of death worldwide; however, the treatment choices available to neurologists are limited in clinical practice. Lipocalin 2 (LCN2) is a secreted protein, belonging to the lipocalin superfamily, with multiple biological functions in mediating innate immune response, inflammatory response, iron-homeostasis, cell migration and differentiation, energy metabolism, and other processes in the body. LCN2 is expressed at low levels in the brain under normal physiological conditions, but its expression is significantly up-regulated in multiple acute stimulations and chronic pathologies. An up-regulation of LCN2 has been found in the blood/cerebrospinal fluid of patients with ischemic/hemorrhagic stroke, and could serve as a potential biomarker for the prediction of the severity of acute stroke. LCN2 activates reactive astrocytes and microglia, promotes neutrophil infiltration, amplifies post-stroke inflammation, promotes blood-brain barrier disruption, white matter injury, and neuronal death. Moreover, LCN2 is involved in brain injury induced by thrombin and erythrocyte lysates, as well as microvascular thrombosis after hemorrhage. In this paper, we review the role of LCN2 in the pathological processes of ischemic stroke; intracerebral hemorrhage; subarachnoid hemorrhage; and stroke-related brain diseases, such as vascular dementia and post-stroke depression, and their underlying mechanisms. We hope that this review will help elucidate the value of LCN2 as a therapeutic target in stroke.

Slow recruitment in the HIMALAIA study: lessons for future clinical trials in patients with delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage based on feasibility data

Background

Our randomized clinical trial on induced hypertension in patients with delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH) was halted prematurely due to unexpected slow recruitment rates. This raised new questions regarding recruitment feasibility. As our trial can therefore be seen as a feasibility trial, we assessed the reasons for the slow recruitment, aiming to facilitate the design of future randomized trials in aSAH patients with DCI or other critically ill patient categories.

Methods

Efficiency of recruitment and factors influencing recruitment were evaluated, based on the patient flow in the two centers that admitted most patients during the study period. We collected numbers of patients who were screened for eligibility, provided informed consent, and developed DCI and who eventually were randomized.

Results

Of the 862 aSAH patients admitted in the two centers during the course of the trial, 479 (56%) were eligible for trial participation of whom 404 (84%) were asked for informed consent. Of these, 188 (47%) provided informed consent, of whom 50 (27%) developed DCI. Of these 50 patients, 12 (24%) could not be randomized due to a logistic problem or a contraindication for induced hypertension emerging at the time of randomization, and four (8%) were missed for randomization. Eventually, 34 patients were randomized and received intervention or control treatment.

Conclusions

Enrolling patients in a randomized trial on a treatment strategy for DCI proved unfeasible: only 1 out of 25 admitted and 1 out of 14 eligible patients could eventually be randomized. These rates, caused by a large proportion of ineligible patients, a small proportion of patients providing informed consent, and a large proportion of patients with contraindications for treatment, can be used to make sample size calculations for future randomized trials in DCI or otherwise critically ill patients. Facilitating informed consent through improved provision of information on risks, possible benefits, and study procedures may result in improved enrolment.

Trial registration

The original trial was prospectively registered with ClinicalTrials.gov (NCT01613235), date of registration 07-06-2012.

Antiplatelet therapy and delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis

OBJECTIVE

Delayed cerebral ischemia (DCI) is a potentially preventable cause of morbidity and mortality after aneurysmal subarachnoid hemorrhage (aSAH). The authors performed a meta-analysis to assess the effect of antiplatelet therapy (APT) on DCI in patients with aSAH.

METHODS

A systematic review of the PubMed and MEDLINE databases was performed. Study inclusion criteria were 1) ≥ 5 aSAH patients; 2) direct comparison between aSAH management with APT and without APT; and 3) reporting of DCI, angiographic, or symptomatic vasospasm rates for patients treated with versus without APT. The primary efficacy outcome was DCI. The outcomes of the APT versus no-APT cohorts were compared. Bias was assessed using the Downs and Black checklist.

RESULTS

The overall cohort comprised 2039 patients from 15 studies. DCI occurred less commonly in the APT compared with the no-APT cohort (pooled = 15.9% vs 28.6%; OR 0.47, p < 0.01). Angiographic (pooled = 51.6% vs 68.7%; OR 0.46, p < 0.01) and symptomatic (pooled = 23.6% vs 37.7%; OR 0.51, p = 0.01) vasospasm rates were lower in the APT cohort. In-hospital mortality (pooled = 1.7% vs 4.1%; OR 0.53, p = 0.01) and functional dependence (pooled = 21.0% vs 35.7%; OR 0.53, p < 0.01) rates were also lower in the APT cohort. Bleeding event rates were comparable between the two cohorts. Subgroup analysis of cilostazol monotherapy compared with no APT demonstrated a lower DCI rate in the cilostazol cohort (pooled = 10.6% vs 28.1%; OR 0.31, p < 0.01). Subgroup analysis of surgically treated aneurysms demonstrated a lower DCI rate for the APT cohort (pooled = 18.4% vs 33.9%; OR 0.43, p = 0.02).

CONCLUSIONS

APT is associated with improved outcomes in aSAH without an increased risk of bleeding events, particularly in patients who underwent surgical aneurysm repair and those treated with cilostazol. Although study heterogeneity is the most significant limitation of the analysis, the findings suggest that APT is worth exploring in patients with aSAH, particularly in a randomized controlled trial setting.

SIRT1 mediates hypoxic postconditioning- and resveratrol-induced protection against functional connectivity deficits after subarachnoid hemorrhage

Functional connectivity (FC) is a sensitive metric that provides a readout of whole cortex coordinate neural activity in a mouse model. We examine the impact of experimental SAH modeled through endovascular perforation, and the effectiveness of subsequent treatment on FC, through three key questions: 1) Does the endovascular perforation model of SAH induce deficits in FC; 2) Does exposure to hypoxic conditioning provide protection against these FC deficits and, if so, is this neurovascular protection SIRT1-mediated; and 3) does treatment with the SIRT1 activator resveratrol alone provide protection against these FC deficits? Cranial windows were adhered on skull-intact mice that were then subjected to either sham or SAH surgery and either left untreated or treated with hypoxic post-conditioning (with or without EX527) or resveratrol for 3 days. Mice were imaged 3 days post-SAH/sham surgery, temporally aligned with the onset of major SAH sequela in mice. Here we show that the endovascular perforation model of SAH induces global and network-specific deficits in FC by day 3, corresponding with the time frame of DCI in mice. Hypoxic conditioning provides SIRT1-mediated protection against these network-specific FC deficits post-SAH, as does treatment with resveratrol. Conditioning-based strategies provide multifaceted neurovascular protection in experimental SAH.

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.

Inhalational Versus Intravenous Anesthetic Conditioning for Subarachnoid Hemorrhage-Induced Delayed Cerebral Ischemia

BACKGROUND

Inhalational anesthetics were associated with reduced incidence of angiographic vasospasm and delayed cerebral ischemia (DCI) in patients with aneurysmal subarachnoid hemorrhage (SAH). Whether intravenous anesthetics provide similar level of protection is not known.

METHODS

Anesthetic data were collected retrospectively for patients with SAH who received general anesthesia for aneurysm repair between January 1, 2014 and May 31, 2018, at 2 academic centers in the United States (one employing primarily inhalational and the other primarily intravenous anesthesia with propofol). We compared the outcomes of angiographic vasospasm, DCI, and neurological outcome (measured by disposition at hospital discharge), between the 2 sites, adjusting for potential confounders.

RESULTS

We compared 179 patients with SAH receiving inhalational anesthetics at one institution to 206 patients with SAH receiving intravenous anesthetics at the second institution. The rates of angiographic vasospasm between inhalational versus intravenous anesthetic groups were 32% versus 52% (odds ratio, 0.49 [CI, 0.32-0.75]; P=0.001) and DCI were 21% versus 40% (odds ratio, 0.47 [CI, 0.29-0.74]; P=0.001), adjusting for imbalances between sites/groups, Hunt-Hess and Fisher grades, type of aneurysm treatment, and American Society of Anesthesiology status. No impact of anesthetics on neurological outcome at time of discharge was noted with rates of good discharge outcome between inhalational versus intravenous anesthetic groups at (78% versus 72%, P=0.23).

CONCLUSIONS

Our data suggest that those who received inhalational versus intravenous anesthetic for ruptured aneurysm repair had significant protection against SAH-induced angiographic vasospasm and DCI. Although we cannot fully disentangle site-specific versus anesthetic effects in this comparative study, these results, when coupled with preclinical data demonstrating a similar protective effect of inhalational anesthetics on vasospasm and DCI, suggest that inhalational anesthetics may be preferable for patients with SAH undergoing aneurysm repair. Additional investigations examining the effect of inhalational anesthetics on other SAH outcomes such as early brain injury and long-term neurological outcomes are warranted.

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.

Interventions for altering blood pressure in people with acute subarachnoid haemorrhage

BACKGROUND

Subarachnoid haemorrhage has an incidence of up to nine per 100,000 person-years. It carries a mortality of 30% to 45% and leaves 20% dependent in activities of daily living. The major causes of death or disability after the haemorrhage are delayed cerebral ischaemia and rebleeding. Interventions aimed at lowering blood pressure may reduce the risk of rebleeding, while the induction of hypertension may reduce the risk of delayed cerebral ischaemia. Despite the fact that medical alteration of blood pressure has been clinical practice for more than three decades, no previous systematic reviews have assessed the beneficial and harmful effects of altering blood pressure (induced hypertension or lowered blood pressure) in people with acute subarachnoid haemorrhage.

OBJECTIVES

To assess the beneficial and harmful effects of altering arterial blood pressure (induced hypertension or lowered blood pressure) in people with acute subarachnoid haemorrhage.

SEARCH METHODS

We searched the following from inception to 8 September 2020 (Chinese databases to 27 January 2019): Cochrane Stroke Group Trials register; CENTRAL; MEDLINE; Embase; five other databases, and five trial registries. We screened reference lists of review articles and relevant randomised clinical trials.

SELECTION CRITERIA

Randomised clinical trials assessing the effects of inducing hypertension or lowering blood pressure in people with acute subarachnoid haemorrhage. We included trials irrespective of publication type, status, date, and language.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We assessed the risk of bias of all included trials to control for the risk of systematic errors. We performed trial sequential analysis to control for the risks of random errors. We also applied GRADE. Our primary outcomes were death from all causes and death or dependency. Our secondary outcomes were serious adverse events, quality of life, rebleeding, delayed cerebral ischaemia, and hydrocephalus. We assessed all outcomes closest to three months' follow-up (primary point of interest) and maximum follow-up.

MAIN RESULTS

We included three trials: two trials randomising 61 participants to induced hypertension versus no intervention, and one trial randomising 224 participants to lowered blood pressure versus placebo. All trials were at high risk of bias. The certainty of the evidence was very low for all outcomes. Induced hypertension versus control Two trials randomised participants to induced hypertension versus no intervention. Meta-analysis showed no evidence of a difference between induced hypertension versus no intervention on death from all causes (risk ratio (RR) 1.60, 95% confidence interval (CI) 0.57 to 4.42; P = 0.38; I² = 0%; 2 trials, 61 participants; very low-certainty evidence). Trial sequential analyses showed that we had insufficient information to confirm or reject our predefined relative risk reduction of 20% or more. Meta-analysis showed no evidence of a difference between induced hypertension versus no intervention on death or dependency (RR 1.29, 95% CI 0.78 to 2.13; P = 0.33; I² = 0%; 2 trials, 61 participants; very low-certainty evidence). Trial sequential analyses showed that we had insufficient information to confirm or reject our predefined relative risk reduction of 20% or more. Meta-analysis showed no evidence of a difference between induced hypertension and control on serious adverse events (RR 2.24, 95% CI 1.01 to 4.99; P = 0.05; I² = 0%; 2 trials, 61 participants; very low-certainty evidence). Trial sequential analysis showed that we had insufficient information to confirm or reject our predefined relative risk reduction of 20% or more. One trial (41 participants) reported quality of life using the Stroke Specific Quality of Life Scale. The induced hypertension group had a median of 47 points (interquartile range 35 to 55) and the no-intervention group had a median of 49 points (interquartile range 35 to 55). The certainty of evidence was very low. One trial (41 participants) reported rebleeding. Fisher's exact test (P = 1.0) showed no evidence of a difference between induced hypertension and no intervention on rebleeding. The certainty of evidence was very low. Trial sequential analysis showed that we had insufficient information to confirm or reject our predefined relative risk reduction of 20% or more. One trial (20 participants) reported delayed cerebral ischaemia. Fisher's exact test (P = 1.0) showed no evidence of a difference between induced hypertension and no intervention on delayed cerebral ischaemia. The certainty of the evidence was very low. Trial sequential analysis showed that we had insufficient information to confirm or reject our predefined relative risk reduction of 20% or more. None of the trials randomising participants to induced hypertension versus no intervention reported on hydrocephalus. No subgroup analyses could be conducted for trials randomising participants to induced hypertension versus no intervention. Lowered blood pressure versus control One trial randomised 224 participants to lowered blood pressure versus placebo. The trial only reported on death from all causes. Fisher's exact test (P = 0.058) showed no evidence of a difference between lowered blood pressure versus placebo on death from all causes. The certainty of evidence was very low.

AUTHORS' CONCLUSIONS

Based on the current evidence, there is a lack of information needed to confirm or reject minimally important intervention effects on patient-important outcomes for both induced hypertension and lowered blood pressure. There is an urgent need for trials assessing the effects of altering blood pressure in people with acute subarachnoid haemorrhage. Such trials should use the SPIRIT statement for their design and the CONSORT statement for their reporting. Moreover, such trials should use methods allowing for blinded altering of blood pressure and report on patient-important outcomes such as mortality, rebleeding, delayed cerebral ischaemia, quality of life, hydrocephalus, and serious adverse events.

Inflammation and Oxidative Stress: Potential Targets for Improving Prognosis After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) has a high mortality rate and causes long-term disability in many patients, often associated with cognitive impairment. However, the pathogenesis of delayed brain dysfunction after SAH is not fully understood. A growing body of evidence suggests that neuroinflammation and oxidative stress play a negative role in neurofunctional deficits. Red blood cells and hemoglobin, immune cells, proinflammatory cytokines, and peroxidases are directly or indirectly involved in the regulation of neuroinflammation and oxidative stress in the central nervous system after SAH. This review explores the role of various cellular and acellular components in secondary inflammation and oxidative stress after SAH, and aims to provide new ideas for clinical treatment to improve the prognosis of SAH.

MicroRNAs as Biomarkers for Predicting Complications following Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a high mortality hemorrhagic stroke that affects nearly 30,000 patients annually in the United States. Approximately 30% of aSAH patients die during initial hospitalization and those who survive often carry poor prognosis with one in five having permanent physical and/or cognitive disabilities. The poor outcome of aSAH can be the result of the initial catastrophic event or due to the many acute or delayed neurological complications, such as cerebral ischemia, hydrocephalus, and re-bleeding. Unfortunately, no effective biomarker exists to predict or diagnose these complications at a clinically relevant time point when neurologic injury can be effectively treated and managed. Recently, a number of studies have demonstrated that microRNAs (miRNAs) in extracellular biofluids are highly associated with aSAH and complications. Here we provide an overview of the current research on relevant human studies examining the correlation between miRNAs and aSAH complications and discuss the potential application of using miRNAs as biomarkers in aSAH management.

Role of Anesthetics and Their Adjuvants in Neurovascular Protection in Secondary Brain Injury after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal rupture accounts for the majority of subarachnoid hemorrhage and is responsible for most cerebrovascular deaths with high mortality and morbidity. Initial hemorrhage severity and secondary brain injury due to early brain injury and delayed cerebral ischemia are the major determinants of outcomes after aneurysmal subarachnoid hemorrhage. Several therapies have been explored to prevent these secondary brain injury processes after aneurysmal subarachnoid hemorrhage with limited clinical success. Experimental and clinical studies have shown a neuroprotective role of certain anesthetics in cerebrovascular disorders including aneurysmal subarachnoid hemorrhage. The vast majority of aneurysmal subarachnoid hemorrhage patients require general anesthesia for surgical or endovascular repair of their aneurysm. Given the potential impact certain anesthetics have on secondary brain injury after SAH, appropriate selection of anesthetics may prove impactful on overall outcome of these patients. This narrative review focuses on the available evidence of anesthetics and their adjuvants in neurovascular protection in aneurysmal subarachnoid hemorrhage and discusses current impact on clinical care and future investigative directions.

Subacute phase of subarachnoid haemorrhage in female rats: Increased intracranial pressure, vascular changes and impaired sensorimotor function

OBJECTIVE

Early brain injury (EBI) and delayed cerebral ischemia (DCI) after subarachnoid haemorrhage (SAH) has devastating consequences but therapeutic options and the underlying pathogenesis remain poorly understood despite extensive preclinical and clinical research. One of the drawbacks of most preclinical studies to date is that the mechanisms behind DCI after SAH are studied only in male animals. In this study we therefore established a female rat model of SAH in order to determine subacute pathophysiological changes that may contribute to DCI in females.

METHODS

Experimental SAH was induced in female rats by intracisternal injection of 300 μL of autologous blood. Sham operation served as a control. Neurological deficits and intracranial pressure measurements were evaluated at both 1 and 2 days after surgery. Additionally, changes in cerebral vascular contractility were evaluated 2 days after surgery using wire myography.

RESULTS

SAH in female rats resulted in sensorimotor deficits and decreased general wellbeing on both day 1 and day 2 after SAH. Intracranial pressure uniformly increased in all rats subjected to SAH on day 1. On day 2 the intracranial pressure had increased further, decreased slightly or remained at the level seen on day 1. Furthermore, female rats subjected to SAH developed cortical brain edema. Cerebral arteries, isolated 2 days after SAH, exhibited increased vascular contractions to endothelin-1 and 5-carboxamidotryptamine.

CONCLUSION

In the subacute phase after SAH in female rats, we observed increased intracranial pressure, decreased wellbeing, sensorimotor deficits, increased vascular contractility and cortical brain edema. Collectively, these pathophysiological changes may contribute to DCI after SAH in females. Previous studies reported similar pathophysiological changes for male rats in the subacute phase after SAH. Thus, prevention of these gender-independent mechanisms may provide the basis for a universal treatment strategy for DCI after SAH. Nevertheless, preclinical studies of potential therapies should employ both male and female SAH models.

Role of SIRT1 in Isoflurane Conditioning-Induced Neurovascular Protection against Delayed Cerebral Ischemia Secondary to Subarachnoid Hemorrhage

We recently reported that isoflurane conditioning provided multifaceted protection against subarachnoid hemorrhage (SAH)-induced delayed cerebral ischemia (DCI), and this protection was through the upregulation of endothelial nitric oxide synthase (eNOS). SIRT1, an NAD-dependent deacetylase, was shown to be one of the critical regulators of eNOS. The aim of our current study is to examine the role of SIRT1 in isoflurane conditioning-induced neurovascular protection against SAH-induced DCI. Mice were divided into four groups: sham, SAH, or SAH with isoflurane conditioning (with and without EX-527). Experimental SAH via endovascular perforation was performed. Anesthetic conditioning was performed with isoflurane 2% for 1 h, 1 h after SAH. EX-527, a selective SIRT1 inhibitor, 10 mg/kg was injected intraperitoneally immediately after SAH in the EX-527 group. SIRT1 mRNA expression and activity levels were measured. Vasospasm, microvessel thrombosis, and neurological outcome were assessed. SIRT1 mRNA expression was downregulated, and no difference in SIRT1 activity was noted after isoflurane exposure. Isoflurane conditioning with and without EX-527 attenuated vasospasm, microvessel thrombosis and improved neurological outcomes. Our data validate our previous findings that isoflurane conditioning provides strong protection against both the macro and micro vascular deficits induced by SAH, but this protection is likely not mediated through the SIRT1 pathway.

An overview of pharmacotherapy for cerebral vasospasm and delayed cerebral ischemia after subarachnoid hemorrhage

Introduction: Survival from aneurysmal subarachnoid hemorrhage has increased in the past few decades. However, functional outcome after subarachnoid hemorrhage is still suboptimal. Delayed cerebral ischemia (DCI) is one of the major causes of morbidity.Areas covered: Mechanisms underlying vasospasm and DCI after aneurysmal subarachnoid hemorrhage and pharmacological treatment are summarized in this review.Expert opinion: Oral nimodine, an L-type dihydropyridine calcium channel blocker, is the only FDA-approved drug for the prevention and treatment of neurological deficits after aneurysmal subarachnoid hemorrhage. Fasudil, a potent Rho-kinase inhibitor, has also been shown to improve the clinical outcome and has been approved in some countries for use in patients with aneurysmal subarachnoid hemorrhage. Although other drugs, including nicardipine, cilostazol, statins, clazosentan, magnesium and heparin, have been expected to have beneficial effects on DCI, there has been no convincing evidence supporting the routine use of those drugs in patients with aneurysmal subarachnoid hemorrhage in clinical practice. Further elucidation of the mechanisms underlying DCI and the development of effective therapeutic strategies for DCI, including combination therapy, are necessary to further improve the functional outcome and mortality after subarachnoid hemorrhage.

Conditioning Effect of Inhalational Anesthetics on Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) has been identified as an independent predictor of poor outcome in numerous studies.

OBJECTIVE

To investigate the potential protective role of inhalational anesthetics against angiographic vasospasm, DCI, and neurologic outcome in SAH patients.

METHODS

After Institutional Review Board approval, data were collected retrospectively for SAH patients who received general anesthesia for aneurysm repair between January 1st, 2010 and May 31st, 2018. Primary outcomes were angiographic vasospasm, DCI, and neurologic outcome as measured by modified Rankin scale at hospital discharge. Univariate and logistic regression analysis were performed to identify independent predictors of these outcomes.

RESULTS

The cohort included 390 SAH patients with an average age of 56 ± 15 (mean ± SD). Multivariate logistic regression analysis identified inhalational anesthetic only technique, Hunt-Hess grade, age, anterior circulation aneurysm and average intraoperative mean blood pressure as independent predictors of angiographic vasospasm. Inhalational anesthetic only technique and modified Fishers grade were identified as independent predictors of DCI. No impact on neurological outcome at time of discharge was noted.

CONCLUSION

Our data provide additional evidence that inhalational anesthetic conditioning in SAH patients affords protection against angiographic vasospasm and new evidence that it exerts a protective effect against DCI. When coupled with similar results from preclinical studies, our data suggest further investigation into the impact of inhalational anesthetic conditioning on SAH patients, including elucidating the most effective dosing regimen, defining the therapeutic window, determining whether a similar protective effect against early brain injury, and on long-term neurological outcome exists.

CBF changes and cerebral energy metabolism during hypervolemia, hemodilution, and hypertension therapy in patients with poor-grade subarachnoid hemorrhage

OBJECTIVE

Despite the multifactorial pathogenesis of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH), augmentation of cerebral blood flow (CBF) is still considered essential in the clinical management of DCI. The aim of this prospective observational study was to investigate cerebral metabolic changes in relation to CBF during therapeutic hypervolemia, hemodilution, and hypertension (HHH) therapy in poor-grade SAH patients with DCI.

METHODS

CBF was assessed by bedside xenon-enhanced CT at days 0-3, 4-7, and 8-12, and the cerebral metabolic state by cerebral microdialysis (CMD), analyzing glucose, lactate, pyruvate, and glutamate hourly. At clinical suspicion of DCI, HHH therapy was instituted for 5 days. CBF measurements and CMD data at baseline and during HHH therapy were required for study inclusion. Non-DCI patients with measurements in corresponding time windows were included as a reference group.

RESULTS

In DCI patients receiving HHH therapy (n = 12), global cortical CBF increased from 30.4 ml/100 g/min (IQR 25.1-33.8 ml/100 g/min) to 38.4 ml/100 g/min (IQR 34.2-46.1 ml/100 g/min; p = 0.006). The energy metabolic CMD parameters stayed statistically unchanged with a lactate/pyruvate (L/P) ratio of 26.9 (IQR 22.9-48.5) at baseline and 31.6 (IQR 22.4-35.7) during HHH. Categorized by energy metabolic patterns during HHH, no patient had severe ischemia, 8 showed derangement corresponding to mitochondrial dysfunction, and 4 were normal. The reference group of non-DCI patients (n = 11) had higher CBF and lower L/P ratios at baseline with no change over time, and the metabolic pattern was normal in all these patients.

CONCLUSIONS

Global and regional CBF improved and the cerebral energy metabolic CMD parameters stayed statistically unchanged during HHH therapy in DCI patients. None of the patients developed metabolic signs of severe ischemia, but a disturbed energy metabolic pattern was a common occurrence, possibly explained by mitochondrial dysfunction despite improved microcirculation.

Role of Endothelial Nitric Oxide Synthase in Isoflurane Conditioning-Induced Neurovascular Protection in Subarachnoid Hemorrhage

Background

Delayed cerebral ischemia remains a common and profound risk factor for poor outcome after subarachnoid hemorrhage (SAH). The aim of our current study is to define the role of endothelial nitric oxide synthase (eNOS) in isoflurane conditioning‐induced neurovascular protection after SAH.

Methods and Results

Ten‐ to 14‐week‐old male wild‐type mice (C57BL/6) as controls and eNOS knockout male mice (strain # 002684) were obtained for the study. Animals underwent either sham surgery, SAH surgery, or SAH with isoflurane conditioning. Anesthetic post conditioning was performed with isoflurane 2% for 1 hour, 1 hour after SAH. Normothermia was maintained with the homeothermic blanket. In a separate cohort, nitric oxide synthase was inhibited by a pan nitric oxide synthase inhibitor, L‐nitroarginine methyl ester. Vasospasm measurement was assessed 72 hours after SAH and neurological function was assessed daily. Isoflurane‐induced changes in the eNOS protein expression were measured. eNOS protein expression was significantly increased by isoflurane conditioning in naïve mice as well as mice subjected to SAH. Vasospasm of the middle cerebral artery and neurological deficits were evident following SAH versus sham surgery, both in wild‐type mice and eNOS knockout mice. Isoflurane conditioning attenuated vasospasm and neurological deficits in wild‐type mice. This delayed cerebral ischemia protection was lost in L‐nitroarginine methyl ester ‐administered mice and eNOS knockout mice.

Conclusions

Our data indicate isoflurane conditioning provides robust protection against SAH‐induced vasospasm and neurological deficits, and that this delayed cerebral ischemia protection is critically mediated via isoflurane‐induced augmentation of eNOS.

The Role of Thrombin in Brain Injury After Hemorrhagic and Ischemic Stroke

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain.

Microvascular platelet aggregation and thrombosis after subarachnoid hemorrhage: A review and synthesis

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) has been associated with numerous pathophysiological sequelae, including large artery vasospasm and microvascular thrombosis. The focus of this review is to provide an overview of experimental animal model studies and human autopsy studies that explore the temporal-spatial characterization and mechanism of microvascular platelet aggregation and thrombosis following SAH, as well as to critically assess experimental studies and clinical trials highlighting preventative therapeutic options against this highly morbid pathophysiological process. Upon review of the literature, we discovered that microvascular platelet aggregation and thrombosis occur after experimental SAH across multiple species and SAH induction techniques in a similar time frame to other components of DCI, occurring in the cerebral cortex and hippocampus across both hemispheres. We discuss the relationship of these findings to human autopsy studies. In the final section of this review, we highlight the important therapeutic options for targeting microvascular platelet aggregation and thrombosis, and emphasize why therapeutic targeting of this neurovascular pathology may improve patient care. We encourage ongoing research into the pathophysiology of SAH and DCI, especially in regard to microvascular platelet aggregation and thrombosis and the translation to randomized clinical trials.

Early Transcranial Doppler Evaluation of Cerebral Autoregulation Independently Predicts Functional Outcome After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Cerebral autoregulation (CA) impairment after aneurysmal subarachnoid hemorrhage (SAH) has been associated with delayed cerebral ischemia and an unfavorable outcome. We investigated whether the early transient hyperemic response test (THRT), a transcranial Doppler (TCD)-based CA evaluation method, can predict functional outcome 6 months after aneurysmal SAH.

METHODS

This is a prospective observational study of all aneurysmal SAH patients consecutively admitted to a single center between January 2016 and February 2017. CA was evaluated within 72 h of hemorrhage by THRT, which describes the changes in cerebral blood flow velocity after a brief compression of the ipsilateral common carotid artery. CA was considered to be preserved when an increase ≥ 9% of baseline systolic velocity was present. According to the modified Rankin Scale (mRS: 4-6), the primary outcome was unfavorable 6 months after hemorrhage. Secondary outcomes included cerebral infarction, vasospasm on TCD, and an unfavorable outcome at hospital discharge.

RESULTS

Forty patients were included (mean age = 54 ± 12 years, 70% females). CA was impaired in 19 patients (47.5%) and preserved in 21 (52.5%). Impaired CA patients were older (59 ± 13 vs. 50 ± 9, p = 0.012), showed worse neurological conditions (Hunt&Hess 4 or 5-47.4% vs. 9.5%, p = 0.012), and clinical initial condition (APACHE II physiological score-12 [5.57-13] vs. 3.5 [3-5], p = 0.001). Fourteen patients in the impaired CA group and one patient in the preserved CA group progressed to an unfavorable outcome (73.7% vs. 4.7%, p = 0.0001). The impaired CA group more frequently developed cerebral infarction than the preserved CA group (36.8% vs. 0%, p = 0.003, respectively). After multivariate analysis, impaired CA (OR 5.15 95% CI 1.43-51.99, p = 0.033) and the APACHE II physiological score (OR 1.67, 95% CI 1.01-2.76, p = 0.046) were independently associated with an unfavorable outcome.

CONCLUSIONS

Early CA impairment detected by TCD and admission APACHE II physiological score independently predicted an unfavorable outcome after SAH.

Evidence for a conditioning effect of inhalational anesthetics on angiographic vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) is characterized by large-artery vasospasm, distal autoregulatory dysfunction, cortical spreading depression, and microvessel thrombi. Large-artery vasospasm has been identified as an independent predictor of poor outcome in numerous studies. Recently, several animal studies have identified a strong protective role for inhalational anesthetics against secondary brain injury after SAH including DCI-a phenomenon referred to as anesthetic conditioning. The aim of the present study was to assess the potential role of inhalational anesthetics against cerebral vasospasm and DCI in patients suffering from an SAH.

METHODS

After IRB approval, data were collected retrospectively for all SAH patients admitted to the authors' hospital between January 1, 2010, and December 31, 2013, who received general anesthesia with either inhalational anesthetics only (sevoflurane or desflurane) or combined inhalational (sevoflurane or desflurane) and intravenous (propofol) anesthetics during aneurysm treatment. The primary outcomes were development of angiographic vasospasm and development of DCI during hospitalization. Univariate and logistic regression analyses were performed to identify independent predictors of these endpoints.

RESULTS

The cohort included 157 SAH patients whose mean age was 56 ± 14 (± SD). An inhalational anesthetic-only technique was employed in 119 patients (76%), while a combination of inhalational and intravenous anesthetics was employed in 34 patients (22%). As expected, patients in the inhalational anesthetic-only group were exposed to significantly more inhalational agent than patients in the combination anesthetic group (p < 0.05). Multivariate logistic regression analysis identified inhalational anesthetic-only technique (OR 0.35, 95% CI 0.14-0.89), Hunt and Hess grade (OR 1.51, 95% CI 1.03-2.22), and diabetes (OR 0.19, 95% CI 0.06-0.55) as significant predictors of angiographic vasospasm. In contradistinction, the inhalational anesthetic-only technique had no significant impact on the incidence of DCI or functional outcome at discharge, though greater exposure to desflurane (as measured by end-tidal concentration) was associated with a lower incidence of DCI.

CONCLUSIONS

These data represent the first evidence in humans that inhalational anesthetics may exert a conditioning protective effect against angiographic vasospasm in SAH patients. Future studies will be needed to determine whether optimized inhalational anesthetic paradigms produce definitive protection against angiographic vasospasm; whether they protect against other events leading to secondary brain injury after SAH, including microvascular thrombi, autoregulatory dysfunction, blood-brain barrier breakdown, neuroinflammation, and neuronal cell death; and, if so, whether this protection ultimately improves patient outcome.

Risk Factor for Poor Outcome in Elderly Patients with Aneurysmal Subarachnoid Hemorrhage Based on Post Hoc Analysis of the Modified WFNS Scale Study

OBJECTIVE

There is currently no precise guide for the treatment and management of elderly patients with aneurysmal subarachnoid hemorrhage (aSAH). Thus, the aim of this study was to clarify the factors of poor outcome and mortality in elderly patients with aSAH.

METHODS

In the modified World Federation of Neurosurgical Societies (mWFNS) scale study, 1124 patients were divided into 2 groups, elderly (age ≥65 years) and non-elderly (age <65 years), with aSAH investigated between October 2010 and March 2013 in Japan. The odds ratio (OR) and 95% confidence interval (CI) of each risk factor was calculated through multivariate logistic regression analysis for poor outcomes, as indicated by the modified Rankin Scale (mRS) score ≥3 and mortality at 3 months after onset in each group.

RESULTS

Both groups demonstrated that the mWFNS scale was significant as a grade order risk factor for poor outcomes and mortality associated with disease. In the elderly group, risk factors for poor outcomes at 3 months after onset were older age (OR 1.10, 95% CI 1.06-1.14), male sex (OR 2.03, 95% CI 1.10-3.73), and severe cerebral vasospasm category (OR 10.13, 95% CI 4.30-23.87). Risk factors for mortality at 3 months after onset were older age (OR 1.06, 95% CI 1.01-1.11) and severe vasospasm category (OR 2.17, 95% CI 1.00-4.72).

CONCLUSIONS

The mWFNS scale is a useful prognostic predictor for both non-elderly and elderly patients with aSAH. Elderly male patients with aSAH presenting with severe vasospasm should be managed more carefully.

White Blood Cell Count Improves Prediction of Delayed Cerebral Ischemia Following Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Immune dysregulation has long been implicated in the development of delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH).

OBJECTIVE

To determine the relationship of inflammatory cell biomarkers with DCI.

METHODS

We evaluated 849 aSAH patients who were enrolled into a prospective observational cohort study and had a white blood cell (WBC) differential obtained within 72 h of bleed onset.

RESULTS

WBC count > 12.1 × 109/L (odds ratio 4.6; 95% confidence interval [CI]: 1.9-11, P < 0.001) was the strongest Complete Blood Count (CBC) predictor of DCI after controlling for clinical grade (P < .001), thickness of SAH blood on admission computed tomography (P = .002), and clipping aneurysm repair (P < .001). A significant interaction between clinical grade and WBC count (odds ratio 0.8, 95% CI: 0.6-1.0, P = .02) revealed that good-grade patients with elevated WBC counts (49%: 273/558) had increased odds for DCI indistinguishable from poor-grade patients. Multivariable Cox regression also showed that elevated WBC counts in good-grade patients increased the hazard for DCI to that of poor-grade patients (hazard ratio 2.1, 95% CI 1.3-3.2, P < .001). Receiver operating characteristic curve analysis of good-grade patients revealed that WBC count (area under the curve [AUC]: 0.63) is a stronger DCI predictor than the modified Fisher score (AUC: 0.57) and significantly improves multivariable DCI prediction models (Z = 2.0, P = .02, AUC: 0.73; PPV: 34%; NPV: 92%).

CONCLUSION

Good-grade patients with early elevations in WBC count have a similar risk and hazard for DCI as poor-grade patients. Good-grade patients without elevated WBC may be candidates to be safely downgraded from the intensive care unit, leading to cost savings for both patient families and hospitals.

Recombinant Human Milk Fat Globule-Epidermal Growth Factor 8 Attenuates Microthrombosis after Subarachnoid Hemorrhage in Rats

BACKGROUND

Microthrombosis after subarachnoid hemorrhage has an adverse effect on prognosis. Milk fat globule-epidermal growth factor 8 promotes phagocytosis of phagocytic cells and may reduce microthrombosis. This study investigated the effects of recombinant human milk fat globule-epidermal growth factor 8 on microthrombosis and neurological function after subarachnoid hemorrhage.

METHODS

Rats subarachnoid hemorrhage model was induced by intravascular puncture method. Western blot was performed to measure the expression of endogenous milk fat globule-epidermal growth factor 8 after subarachnoid hemorrhage. Microthrombosis was quantified by microthrombi count using immunohistochemistry and immunofluorescence. The neuroprotective effect of recombinant human milk fat globule-epidermal growth factor 8 administration was evaluated by modified Garcia score, beam balance, Rotarod test, and Morris water maze.

RESULTS

Endogenous milk fat globule-epidermal growth factor 8 protein level increased after subarachnoid hemorrhage. Microthrombosis was significantly increased in subarachnoid hemorrhage rats brain, while recombinant human milk fat globule-epidermal growth factor 8 dramatically reduced microthrombosis as well as improve short- and long- term neurobehavior after subarachnoid hemorrhage.

CONCLUSIONS

Recombinant human milk fat globule-epidermal growth factor 8 reduces microthrombosis and improves neurological function after subarachnoid hemorrhage, which may be an effective strategy for treating subarachnoid hemorrhage.

Recent Advances in Stem Cell Research in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke with significant morbidity and mortality, and it often leads to poor clinical outcome. Although great efforts have been made toward animal and clinical studies, optimal therapy of SAH remains a challenge for scientists and clinicians. Increasing evidence suggests that stem-cell-based therapies may provide innovative approaches for treatment of SAH-related disability. In this review, we summarized the recent advances in stem cell research in SAH. Neuroregeneration after SAH could be conducted by the activation of endogenous neural stem cells (NSCs), transplantation of external stem cells, or reprogramming non-neuronal cell to neurons. The potential mechanism and signaling pathways, as well as the efficiency and safety of these stem cell treatments, were discussed in detail. Although lots of challenges remain for translating the laboratory findings and technologies into clinical therapies, these research studies provided the foundation and guidance for using different resources of stem cells as a brain repair strategy after SAH.

High-Resolution MRI Vessel Wall Imaging in Acute Aneurysmal Subarachnoid Hemorrhage : Spatiotemporal Pattern and Clinicoradiologic Implications

PURPOSE

The spatiotemporal pattern of vessel wall changes was investigated on two time point magnetic resonance images (MRI) in patients with aneurysmal subarachnoid hemorrhages (aSAH) and its association with clinicoradiologic severity score and delayed cerebral ischemia (DCI) was analyzed.

METHODS

A total of 32 prospectively enrolled patients with aSAH (mean age 56.94 years; 9 male and 23 female) underwent vessel wall imaging (VWI) MRI. Of the patients 20 completed two time point MRIs early and late during the admission, 10 patients only had early MRI and 2 patients only had late MRI. Timing of early MRI had a mean of 2.5 days (range 1-6 days) and late MRI had a mean of 10.5 days (range 7-16 days) from time of admission. Spatiotemporal pattern of vessel wall enhancement (VWE), vasospasm, diffusion-weighted imaging (DWI) lesion burden (grade 0-III) and infarcts were analyzed against the clinicoradiologic severity score (high-risk: vasograde red and yellow, low-risk: vasograde green) and DCI.

RESULTS

On the early MRI, mild VWE alone was significantly more frequent in the high-risk group (36.7% versus 20.0%; P = 0.024). On the late MRI, vasospasm was significantly more frequent in the high-risk group (27.2% versus 4.5%; P = 0.022). Vasospasm infrequently showed mild VWE (6.67% on early MRI and 9.09% on late MRI). Both mild VWE alone on early MRI and on late MRI were significantly associated with development of DCI during the admission (P = 0.034 and P = 0.035, respectively).

CONCLUSION

Mild VWE on early MRI and vasospasm on late MRI were significantly more prevalent in high-risk and DCI patients suggesting VWI might enable imaging of early neuroinflammatory changes which are part of the pathomechanism of vasospasm and DCI.

Effect of HHH-Therapy on Regional CBF after Severe Subarachnoid Hemorrhage Studied by Bedside Xenon-Enhanced CT

Background

Management of delayed cerebral ischemia (DCI) following subarachnoid hemorrhage (SAH) is difficult and still carries controversies. In this study, the effect of therapeutic hypervolemia, hemodilution, and hypertension (HHH-therapy) on cerebral blood flow (CBF) was assessed by xenon-enhanced computerized tomography (XeCT) hypothesizing an increase in CBF in poorly perfused regions.

Methods

Bedside XeCT measurements of regional CBF in mechanically ventilated SAH patients were routinely scheduled for day 0–3, 4–7, and 8–12. At clinical suspicion of DCI, patients received 5-day HHH-therapy. For inclusion, XeCT was required at 0–48 h before start of HHH (baseline) and during therapy. Data from corresponding time-windows were also collected for non-DCI patients.

Results

Twenty patients who later developed DCI were included, and twenty-eight patients without DCI were identified for comparison. During HHH, there was a slight nonsignificant increase in systolic blood pressure (SBP) and a significant reduction in hematocrit. Median global cortical CBF for the DCI group increased from 29.5 (IQR 24.6–33.9) to 38.4 (IQR 27.0–41.2) ml/100 g/min (P = 0.001). There was a concomitant increase in regional CBF of the worst vascular territories, and the proportion of area with blood flow below 20 ml/100 g/min was significantly reduced. Non-DCI patients showed higher CBF at baseline, and no significant change over time.

Conclusions

HHH-therapy appeared to increase global and regional CBF in DCI patients. The increase in SBP was small, while the decrease in hematocrit was more pronounced, which may suggest that intravascular volume status and rheological effects are of importance. XeCT may be potentially helpful in managing poor-grade SAH patients.

Induced Hypertension in Preventing Cerebral Infarction in Delayed Cerebral Ischemia After Subarachnoid Hemorrhage

Background and Purpose- Delayed cerebral ischemia (DCI) is an important cause of poor outcome after aneurysmal subarachnoid hemorrhage. If clinical signs of DCI occur, induced hypertension is a plausible but unproven therapeutic intervention. There is clinical equipoise if the use of hypertension induction is useful or not with the consequence that this strategy is irregularly used. We explored the effect of blood pressure augmentation in preventing cerebral infarction in patients with clinical signs of DCI. Methods- We performed a retrospective observational study, totaling 1647 patients with aneurysmal subarachnoid hemorrhage admitted at 3 academic hospitals in the Netherlands between 2006 and 2015. To study the primary outcome DCI related cerebral infarcts, we only included patients with no cerebral infarct at the time of onset of clinical signs of DCI. Cox regression was used to test the association between induced hypertension after onset of clinical signs of DCI and the occurrence of DCI related cerebral infarcts. Logistic regression was used to relate hypertension induction with poor outcome after 3 months, defined as a modified Rankin score >3. Results were adjusted for treatment center and baseline characteristics. Results- Clinical signs of DCI occurred in 479 (29%) patients of whom 300 without cerebral infarction on computed tomography scan at that time. Of these 300 patients, 201 (67%) were treated with hypertension induction and 99 were not. Of the patients treated with hypertension induction, 41 (20%) developed a DCI related cerebral infarct compared with 33 (33%) with no induced hypertension: adjusted hazard ratio, 0.59; 95% CI, 0.35 to 0.99. Hypertension induction also prevented poor outcome: adjusted odds ratio, 0.27; 95% CI, 0.14 to 0.55. Conclusions- Hypertension induction seems an effective strategy for preventing DCI related cerebral infarcts if not already present at the time of onset of clinical signs of DCI. This may lead to a reduction in poor clinical outcome.

Haemoglobin scavenging in intracranial bleeding: biology and clinical implications

Haemoglobin is released into the CNS during the breakdown of red blood cells after intracranial bleeding. Extracellular free haemoglobin is directly neurotoxic. Haemoglobin scavenging mechanisms clear haemoglobin and reduce toxicity; these mechanisms include erythrophagocytosis, haptoglobin binding of haemoglobin, haemopexin binding of haem and haem oxygenase breakdown of haem. However, the capacity of these mechanisms is limited in the CNS, and they easily become overwhelmed. Targeting of haemoglobin toxicity and scavenging is, therefore, a rational therapeutic strategy. In this Review, we summarize the neurotoxic mechanisms of extracellular haemoglobin and the peculiarities of haemoglobin scavenging pathways in the brain. Evidence for a role of haemoglobin toxicity in neurological disorders is discussed, with a focus on subarachnoid haemorrhage and intracerebral haemorrhage, and emerging treatment strategies based on the molecular pathways involved are considered. By focusing on a fundamental biological commonality between diverse neurological conditions, we aim to encourage the application of knowledge of haemoglobin toxicity and scavenging across various conditions. We also hope that the principles highlighted will stimulate research to explore the potential of the pathways discussed. Finally, we present a consensus opinion on the research priorities that will help to bring about clinical benefits.

Pre-clinical effects of highly potent MEK1/2 inhibitors on rat cerebral vasculature after organ culture and subarachnoid haemorrhage

Background: Aneurysmal subarachnoid haemorrhage (SAH) is a variant of haemorrhagic stroke with a striking 50% mortality rate. In addition to the initial insult, secondary delayed brain injury may occur days after the initial ischemic insult and is associated with vasospasms leading to delayed cerebral ischemia. We have previously shown that the MEK1/2 inhibitor U0126 improves neurological assessment after SAH in rats. Aim: The purpose of the present study was to analyse the impact of a broad selection of high potency MEK1/2 inhibitors in an organ culture model and use the IC50 values obtained from the organ culture to select highly potent inhibitors for pre-clinical in vivo studies. Results: Nine highly potent mitogen activated protein kinase kinase (MEK1/2) inhibitors were screened and the two most potent inhibitors from the organ culture screening, trametinib and PD0325901, were tested in an in vivo experimental rat SAH model with intrathecal injections. Subsequently, the successful inhibitor trametinib was administered intraperitoneally in a second in vivo study. In both regimens, trametinib treatment caused significant reductions in the endothelin-1 induced contractility after SAH, which is believed to be associated with endothelin B receptor up-regulation. Trametinib treated rats showed improved neurological scores, evaluated by the ability to traverse a rotating pole, after induced SAH. Conclusion: The PD0325901 treatment did not improve the neurological score after SAH, nor showed any beneficial therapeutic effect on the contractility, contrasting with the reduction in neurological deficits seen after trametinib treatment. These data show that trametinib might be a potential candidate for treatment of SAH.

MEK1/2 inhibitor U0126, but not nimodipine, reduces upregulation of cerebrovascular contractile receptors after subarachnoid haemorrhage in rats

Vascular pathophysiological changes after haemorrhagic stroke, such as phenotypic modulation of the cerebral arteries and cerebral vasospasms, are associated with delayed cerebral ischemia (DCI) and poor outcome. The only currently approved drug treatment shown to reduce the risk of DCI and improve neurologic outcome after aneurysmal subarachnoid haemorrhage (SAH) is nimodipine, a dihydropyridine L-type voltage-gated Ca2+ channel blocker. MEK1/2 mediated transcriptional upregulation of contractile receptors, including endothelin-1 (ET-1) receptors, has previously been shown to be a factor in the pathology of SAH. The aim of the study was to compare intrathecal and subcutaneous treatment regimens of nimodipine and intrathecal treatment regimens of U0126, a MEK1/2 inhibitor, in a single injection experimental rat SAH model with post 48 h endpoints consisting of wire myography of cerebral arteries, flow cytometry of cerebral arterial tissue and behavioural evaluation. Following ET-1 concentration-response curves, U0126 exposed arteries had a significantly lower ET-1max than vehicle arteries. Arteries from both the intrathecal- and subcutaneous nimodipine treated animals had significantly higher ET-1max contractions than the U0126 arteries. Furthermore, Ca2+ concentration response curves (precontracted with ET-1 and in the presence of nimodipine) showed that nimodipine treatment could result in larger nimodipine insensitive contractions compared to U0126. Flow cytometry showed decreased protein expression of the ETB receptor in U0126 treated cerebral vascular smooth muscle cells compared to vehicle. Only U0126 treatment lowered ET-1max contractions and ETB receptor levels, as well as decreased the contractions involving nimodipine-insensitive Ca2+ channels, when compared to both intrathecal and subcutaneous nimodipine treatment. This indicate that targeting gene expression might be a better strategy than blocking specific receptors or ion channels in future treatments of SAH.

Delayed Ischemic Neurologic Deficit after Aneurysmal Subarachnoid Hemorrhage

Delayed ischemic neurologic deficit (DIND) is the main preventable cause of poor outcomes in aneurysmal subarachnoid hemorrhage (SAH) patients. Of 50% of survivors from a SAH, approximately 30% of patients will present clinical vasospasm (VS). The cornerstone of the DIND management comprises prevention and early identification. Several diagnostic methods have been proposed differing in efficacy, invasiveness, and costs. Serial neurological examination is the most reliable method to detect a new neurological deficit. On the other hand, comatose patients require advanced monitoring methods which identify changes in the microcirculatory environment, brain autoregulation, and spreading depolarization. Multimodality monitoring with continuous electroencephalography, microdialysis, and intracranial pressure monitoring represents altogether the current state-of-art technology for the intensive care of SAH patients. Moreover, advances in genetic biomarkers to predict clinical VS have shown consistent accuracy which may in the near future allow the early prediction of DIND through a simple blood test. Several clinical trials have tested drugs with theoretical effects on DIND prevention or treatment. Nevertheless, nimodipine remains the Holy Grail in the prevention of clinical VS. Among rescue therapies, the endovascular treatment through intra-arterial vasodilator (verapamil or nicardipine) infusion is the most employed method for DIND reversal; however, there is no good quality evidence comparing results of intra-arterial infusion of vasodilators versus balloon angioplasty. Although we have addressed the most refined technology in the management of SAH and DIND, the clinical experience and strict follow-up in neurointensive care will be determinant for favorable long-term outcomes.

Association of copeptin, a surrogate marker of arginine vasopressin, with cerebral vasospasm and delayed ischemic neurologic deficit after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Delayed ischemic neurological deficit (DIND) is a leading cause of mortality and morbidity after aneurysmal subarachnoid hemorrhage (aSAH). Arginine vasopressin (AVP) is a hormone released by the posterior pituitary. It is known to cause cerebral vasoconstriction and has been implicated in hyponatremia secondary to the syndrome of inappropriate antidiuretic hormone secretion. Direct measurement of AVP is limited by its short half-life. Copeptin, a cleavage product of the AVP precursor protein, was therefore used as a surrogate marker for AVP. This study aimed to investigate the temporal relationship between changes in copeptin concentrations and episodes of DIND and hyponatremia.

METHODS

Copeptin concentrations in cerebrospinal fluid were quantified using enzyme-linked immunosorbent assay in 19 patients: 10 patients with DIND, 6 patients without DIND (no-DIND), and 3 controls.

RESULTS

Copeptin concentrations were higher in DIND and no-DIND patients than in controls. In hyponatremic DIND patients, copeptin concentrations were higher compared with hyponatremic no-DIND patients. DIND was associated with a combination of decreasing sodium levels and increasing copeptin concentrations.

CONCLUSIONS

Increased AVP may be the unifying factor explaining the co-occurrence of hyponatremia and DIND. Future studies are indicated to investigate this relationship and the therapeutic utility of AVP antagonists in the clinical setting.

Tumor necrosis factor receptor-associated factor 6 participates in early brain injury after subarachnoid hemorrhage in rats through inhibiting autophagy and promoting oxidative stress

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a member of the TRAF family and an important multifunctional intracellular adaptin of the tumor necrosis factor superfamily and toll/IL-1 receptor (TIR) superfamily. TRAF6 has been studied in several central nervous system diseases, including ischemic stroke, traumatic brain injury, and neurodegenerative diseases, but its role in subarachnoid hemorrhage (SAH) has not been fully illustrated. This study was designed to explore changes of expression level and potential roles and mechanisms of TRAF6 in early brain injury (EBI) after SAH using a Sprague-Dawley rat model of SAH induced in 0.3 mL non-heparinized autologous arterial blood injected into the pre-chiasmatic cistern. First, compared with the sham group, we found that the expression levels of TRAF6 increased gradually and peaked at 24 h after SAH. Second, the results showed that application of TRAF6 over-expression plasmid and genetic silencing siRNA could increase or decrease expression of TRAF6, respectively, and severely exacerbate or relieve EBI after SAH, including neuronal death, brain edema, and blood-brain barrier injury. Meanwhile, the levels of autophagy and oxidative stress were reduced and increased separately. Finally, GFP-TRAF6-C70A, which is a TRAF6 mutant that lacks E3 ubiquitin ligase activity, was used to explore the mechanism of TRAF6 in SAH, and the results showed that EBI and oxidative stress were reduced, but the levels of autophagy were increased under this condition. Collectively, these results indicated that TRAF6 affected the degree of EBI after SAH by inhibiting autophagy and promoting oxidative stress.

Monitoring the Neuroinflammatory Response Following Acute Brain Injury

Traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) are major contributors to morbidity and mortality. Following the initial insult, patients may deteriorate due to secondary brain damage. The underlying molecular and cellular cascades incorporate components of the innate immune system. There are different approaches to assess and monitor cerebral inflammation in the neuro intensive care unit. The aim of this narrative review is to describe techniques to monitor inflammatory activity in patients with TBI and SAH in the acute setting. The analysis of pro- and anti-inflammatory cytokines in compartments of the central nervous system (CNS), including the cerebrospinal fluid and the extracellular fluid, represent the most common approaches to monitor surrogate markers of cerebral inflammatory activity. Each of these compartments has a distinct biology that reflects local processes and the cross-talk between systemic and CNS inflammation. Cytokines have been correlated to outcomes as well as ongoing, secondary injury progression. Alongside the dynamic, focal assay of humoral mediators, imaging, through positron emission tomography, can provide a global in vivo measurement of inflammatory cell activity, which reveals long-lasting processes following the initial injury. Compared to the innate immune system activated acutely after brain injury, the adaptive immune system is likely to play a greater role in the chronic phase as evidenced by T-cell-mediated autoreactivity toward brain-specific proteins. The most difficult aspect of assessing neuroinflammation is to determine whether the processes monitored are harmful or beneficial to the brain as accumulating data indicate a dual role for these inflammatory cascades following injury. In summary, the inflammatory component of the complex injury cascade following brain injury may be monitored using different modalities. Using a multimodal monitoring approach can potentially aid in the development of therapeutics targeting different aspects of the inflammatory cascade and improve the outcome following TBI and SAH.

Functional Outcomes and Delayed Cerebral Ischemia Following Nonperimesencephalic Angiogram-Negative Subarachnoid Hemorrhage Similar to Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The angiogram-negative subarachnoid hemorrhage (SAH) literature includes patients with perimesencephalic hemorrhage, which is recognized to have a much better outcome than aneurysmal SAH.

OBJECTIVE

To evaluate the clinical outcomes of Nonperimesencephalic Angiogram-Negative SAH (NPAN-SAH).

METHODS

A prospective, spontaneous SAH database of 1311 patients that accrued between April 2006 and December 2014 was screened. All patients with NPAN-SAH and 2 consecutive negative cerebral angiograms were included.

RESULTS

We identified 191 (11%) from a total of 1311 patients with spontaneous SAH. Amongst angiogram-negative patients, 83 (4.9%) were adjudicated to have NPAN-SAH. Patient characteristics were similar across the groups, except NPAN-SAH patients were more likely to be men and had higher rates of diabetes. In a multivariable logistic regression model, NPAN-SAH patients were less likely to develop vasospasm, after adjusting for Fisher grade, sex, and diabetes (odds ratio [OR]: 0.197, 95% confidence interval [CI; 0.07-0.55], P = .002). In another adjusted model accounting for Hunt and Hess clinical grade, NPAN-SAH patients were also less likely to develop vasospasm (OR: 0.2, 95% CI [0.07-0.57], P = .002). We found no statistical significance between 2 groups for rebleed, developing hydrocephalus, seizures, or delayed cerebral ischemia. NPAN-SAH patients were equally associated with poor functional outcome (modified Rankin scale ≥3; OR: 1.16, 95% CI [0.615-2.20], P = .6420), and death (OR: 1.22, 95% CI [0.362-4.132], P = .7455) compared to aneurysmal SAH.

CONCLUSION

Although the risk of vasospasm may be lower, patients with NPAN-SAH are equally associated with delayed cerebral ischemia, poor outcome, and death as compared to patients with aneurysmal SAH. Furthers studies may be necessary to further clarify these findings

Increase of Soluble RAGE in Cerebrospinal Fluid following Subarachnoid Haemorrhage

Receptors for advanced glycation end-products (RAGE) mediate the inflammatory reaction that follows aneurysmal subarachnoid haemorrhage. Soluble RAGE (sRAGE) may function as a decoy receptor. The significance of this endogenous anti-inflammatory mechanism in subarachnoid haemorrhage (SAH) remains unknown. The present study aims to analyse sRAGE levels in the cerebrospinal fluid (CSF) of SAH patients. sRAGE levels were assayed by ELISA kit in 47 CSF samples collected on post-SAH days 0–3, 5–7, and 10–14 from 27 SAH patients with acute hydrocephalus. CSF levels of sRAGE were compared with a control group and correlated with other monitored parameters. In the control group, the CSF contained only a trace amount of sRAGE. By contrast, the CSF of 20 SAH patients collected on post-SAH days 0–3 was found to contain statistically significant higher levels of sRAGE (mean concentration 3.91 pg/mL, p < 0.001). The most pronounced difference in CSF sRAGE levels between good and poor outcome patients was found on days 0–3 post-SAH but did not reach the significance threshold (p = 0.234). CSF sRAGE levels did not change significantly during hospitalisation (p = 0.868) and correlated poorly with treatment outcome, systemic inflammatory markers, and other monitored parameters. Our study revealed an early and constant increase of sRAGE level in the CSF of SAH patients.

Current Treatment Strategies for Intracranial Aneurysms: An Overview

Intracranial aneurysm is a leading cause of stroke. Its treatment has evolved over the past 2 decades. This review summarizes the treatment strategies for intracranial aneurysms from 3 different perspectives: open surgery approach, transluminal treatment approach, and new technologies being used or trialed. We introduce most of the available treatment techniques in detail, including contralateral clipping, wrapping and clipping, double catheters assisting coiling and waffle-cone technique, and so on. Data from major trials such as Analysis of Treatment by Endovascular approach of Non-ruptured Aneurysms (ATENA), Internal Subarachnoid Trial (ISAT), Clinical and Anatomical Results in the Treatment of Ruptured Intracranial Aneurysms (CLARITY), and Barrow Ruptured Aneurysm Trial (BRAT) as well as information from other clinical reports and local experience are reviewed to suggest a clinical pathway for treating different types of intracranial aneurysms. It will be a valuable supplement to the current existing guidelines. We hope it could help assisting real-time decision-making in clinical practices and also encourage advancements in managing the disease.

An introduction to the pathophysiology of aneurysmal subarachnoid hemorrhage

Pathophysiological processes following subarachnoid hemorrhage (SAH) present survivors of the initial bleeding with a high risk of morbidity and mortality during the course of the disease. As angiographic vasospasm is strongly associated with delayed cerebral ischemia (DCI) and clinical outcome, clinical trials in the last few decades focused on prevention of these angiographic spasms. Despite all efforts, no new pharmacological agents have shown to improve patient outcome. As such, it has become clear that our understanding of the pathophysiology of SAH is incomplete and we need to reevaluate our concepts on the complex pathophysiological process following SAH. Angiographic vasospasm is probably important. However, a unifying theory for the pathophysiological changes following SAH has yet not been described. Some of these changes may be causally connected or present themselves as an epiphenomenon of an associated process. A causal connection between DCI and early brain injury (EBI) would mean that future therapies should address EBI more specifically. If the mechanisms following SAH display no causal pathophysiological connection but are rather evoked by the subarachnoid blood and its degradation production, multiple treatment strategies addressing the different pathophysiological mechanisms are required. The discrepancy between experimental and clinical SAH could be one reason for unsuccessful translational results.

The Pathophysiology of Delayed Cerebral Ischemia

Subarachnoid hemorrhage (SAH) affects 30,000 people in the Unites States alone each year. Delayed cerebral ischemia occurs days after subarachnoid hemorrhage and represents a potentially treatable cause of morbidity for approximately one-third of those who survive the initial hemorrhage. While vasospasm has been traditionally linked to the development of cerebral ischemia several days after subarachnoid hemorrhage, emerging evidence reveals that delayed cerebral ischemia is part of a much more complicated post-subarachnoid hemorrhage syndrome. The development of delayed cerebral ischemia involves early arteriolar vasospasm with microthrombosis, perfusion mismatch and neurovascular uncoupling, spreading depolarizations, and inflammatory responses that begin at the time of the hemorrhage and evolve over time, culminating in cortical infarction. Large-vessel vasospasm is likely a late contributor to ongoing injury, and effective treatment for delayed cerebral ischemia will require improved detection of critical early pathophysiologic changes as well as therapeutic options that target multiple related pathways.