Large Artery Vasospasm Research Articles

Endovascular therapy for cerebral vasospasm after aneurysmal subarachnoid hemorrhage: Single-center experience in a high-volume neurovascular unit

IntroductionDespite targeted standard therapy, aneurysmal subarachnoid hemorrhage (aSAH) frequently leads to cerebral vasospasms (CVS) of large cerebral arteries, reduced oxygen supply of brain tissue, known as delayed cerebral ischemia (DCI), subsequent development of manifest cerebral infarction and poor neurological outcome. Research questionThe primary aim was to evaluate the efficacy of endovascular spasmolysis (eSL) as a rescue therapy for delayed ischemic neurological deficits (DIND) occurring despite maximum conservative treatment, with the potential benefit of preventing permanent ischemic deficits, and thus, improving overall neurological outcomes. Material and methodsIn our retrospective, monocentric study, we included 310 patients developing CVS during hospitalization and evaluated their clinical and radiographic outcomes. Severe vasospasm was defined by a mean velocity of >200 cm/s in transcranial Doppler ultrasound and/or occurrence of new neurological deficits, and/or decrease of at least 2 points on the Glasgow Coma Scale (GCS), respectively. Results92 patients (29.7%) underwent eSL due to persistent symptoms despite conservative therapy. Among endovascularly treated patients, 86% (n = 79) improved angiographically, 71% (n = 44) of 62 patients who underwent eSL due to symptomatic deterioration improved clinically. Clinical worsening due to progressive CVS occurred in 18% of cases (n = 11). Periprocedural complications were observed in 4% (n = 4). Discussion and conclusioneSL emerges as a safe and effective therapy for individuals experiencing DIND triggered by large-artery vasospasm following aSAH. The implementation of a standardized, multi-step process for detection and management, coupled with criteria for endovascular interventions, proves to be an efficient preventative approach to enhance neurological outcomes after aSAH.

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.

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.

Cisterna Magna Injection Mouse Model of Subarachnoid Hemorrhage (SAH): A Systematic Literature Review of Preclinical SAH Research

Objective: This review article describes the characteristics of published literature using the cisterna magna blood injection mouse model of subarachnoid hemorrhage (SAH) with the aim to define particular standards and identify moderators of mortality rate, SAH grade, and large artery vasospasm. Methods: We searched for English-original peer-reviewed studies which reported the induction of SAH in mice via single or multiple blood injections into the cisterna magna. The search included studies published until 13th February 2023 on PubMed, Embase and Web of Science. Furthermore, we investigated the reporting of mortality rate, vasospasms by measuring large arteries, and SAH grade in cisterna magna blood injection mouse model. Results: Seven articles out of 136 identified records matched our inclusion criteria and were therefore included in descriptive analysis. Four articles reported the mortality rate which varied between zero and 22 percent. Five articles displayed vasospasms of large cerebral arteries including basilar artery (BA), anterior cerebral artery (ACA), and middle cerebral artery (MCA). Interestingly, the diameters of the observed arteries started to decrease already within the first hour after blood injection and achieved the lowest values at different times, but mainly between six and twelve hours after SAH induction. The artery diameters reached nearly their pre-SAH (control group) diameters approximately after four to seven days after SAH. However, the SAH severity grade was reported in none of these publications. No uniform model characteristics were observed in current literature. Conclusion: A systemic overview of the cisterna magna blood injection mouse model of SAH is presented. An important heterogeneity was observed. Hence, standardized model features and study endpoints have to be defined in order to improve reporting frequency and quality to enhance the reproducibility of preclinical SAH research in the future.

Efficacy and safety of bridging therapy and direct mechanical thrombectomy in large vessel occlusions: a meta-analysis.

Efficacy and safety of bridging therapy and direct mechanical thrombectomy in large vessel occlusions: a meta-analysis.

Abstract WP214: Inhibition Of 12/15-Lipoxygenase Attenuates Delayed Vasospasm After Subarachnoid Hemorrhage In Mice

Approximately 30% of subarachnoid hemorrhage (SAH) patients who survive the initial ictus develop delayed cerebral ischemia (DCI) 4 to 10 days following SAH. Multiple clinical studies indicate the cause of DCI is multifactorial and includes vasospasm. 12/15-Lipoxygenase (LOX), enzymes that metabolize arachidonic acid into bioactive lipid metabolites, such as 12-HETE and 15-HETE, are expressed in several cell types of the brain including neurons, and microglia. Previous work has shown that 12/15-LOX has detrimental effects on brain vasculature and neurons, triggers inflammation, and thrombosis. In a previous study, inhibition of 12/15-LOX was beneficial in reducing early brain injury in mice after SAH. We hypothesize that inhibition of 12/15-LOX would attenuate delay vasospasm and reduce DCI in SAH mice. C57BL/6 mice of both sexes were randomized into Sham+Vehicle, SAH+Vehicle, SAH+ML351. Vehicle and ML351 (LOX inhibitor, 25mg/kg) were intravenously injected 15 minutes after SAH. 12/15-LOX -/- mice of both sexes were randomized into sham or SAH. Behavior was assessed daily until euthanasia on day 5 for analysis of vasospasm. Following SAH, there, there was an increased expression of 12/15-LOX in brain endothelial cells. Inhibition of 12/15-LOX in C57BL/6 males reduced large artery vasospasm and microvessel constriction, improved functional outcome, and lowered DCI incidence. In female C57BL/6 mice, inhibition of 12/15-LOX also reduced vasospasm and microvessel constriction, and ameliorated behavioral deficits. 12/15-LOX -/- displayed better behavior and have less delayed vasospasm. The findings of this study suggest that inhibition of 12/15-LOX is therapeutically beneficial for male and female mice after SAH via preventing delay vasospasm and DCI.

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

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

Sevoflurane and Desflurane Exposures Following Aneurysmal Subarachnoid Hemorrhage Confer Multifaceted Protection against Delayed Cerebral Ischemia.

Numerous studies have demonstrated the ability of isoflurane conditioning to provide multifaceted protection against aneurysmal subarachnoid hemorrhage (SAH)-associated delayed cerebral ischemia (DCI); however, preclinical studies have not yet examined whether other commonly used inhalational anesthetics in neurological patients such as sevoflurane or desflurane are also protective against SAH-induced neurovascular deficits. We therefore sought to identify the potential for sevoflurane and desflurane conditioning to protect against DCI in an endovascular perforation mouse model of SAH. Neurological function was assessed daily via neuroscore. Large artery vasospasm and microvessel thrombosis were assessed three days after SAH or sham surgery. Four groups were examined: Sham, SAH + room air, SAH + 2% Sevoflurane, and SAH + 6% Desflurane. For the SAH groups, one hour after surgery, mice received 2% sevoflurane, 6% desflurane, or room air for one hour. We found that conditioning with sevoflurane or desflurane attenuated large artery vasospasm, reduced microvessel thrombosis, and improved neurologic function. Given their frequent clinical use and strong safety profile in patients (including those with SAH), these data strongly support further studies to validate these findings in preclinical and clinical studies and to elucidate the mechanisms by which these agents might be acting.

Anesthetic and subanesthetic doses of isoflurane conditioning provides strong protection against delayed cerebral ischemia in a mouse model of subarachnoid hemorrhage

Delayed cerebral ischemia (DCI) is identified as one of the significant contributors to poor patient outcome after aneurysmal subarachnoid hemorrhage (SAH). We previously reported that a supratherapeutic dose of isoflurane conditioning (2%) provided robust protection against SAH-induced DCI. The aim of our current study is to compare the efficacy of the supratherapeutic dose of isoflurane to that typically used to establish general anesthesia or sedation. After IRB approval for animal studies, ten to fourteen-week-old wild-type male mice (C57BL/6) were divided into five groups – sham, SAH alone, or SAH with isoflurane conditioning (0.5%, 1%, and 2%). Conditioning was performed with one-hour of isoflurane initiated one-hour after induction of SAH via endovascular perforation technique. Vasospasm measurement in the middle cerebral artery was assessed 72 h after SAH. Neurological assessment was performed at baseline and for next three days after SAH. It was identified that all tested doses of isoflurane conditioning (0.5%, 1%, and 2%) significantly attenuated large artery vasospasm and markedly improved neurological deficits following SAH. No significant differences in neurovascular outcome were noted between the three doses of isoflurane conditioning. Our data show that isoflurane dosing typically used for general anesthesia (1%) or sedation (0.5%) provide similar levels of DCI protection in SAH as that provided by a supratherapeutic dose (2%). This result has important implications for future translational studies. Additional studies examining the therapeutic potential of anesthetic conditioning for SAH are therefore warranted.

Cerebrovascular pathophysiology of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

Aneurysmal subarachnoid hemorrhage (SAH) remains a serious cerebrovascular disease. Even if SAH patients survive the initial insults, delayed cerebral ischemia (DCI) may occur at 4 days or later post-SAH. DCI is characteristics of SAH, and is considered to develop by blood breakdown products and inflammatory reactions, or secondary to early brain injury, acute pathophysiological events that occur in the brain within the first 72 hours of aneurysmal SAH. The pathology underlying DCI may involve large artery vasospasm and/or microcirculatory disturbances by microvasospasm, microthrombosis, dysfunction of venous outflow and compression of microvasculature by vasogenic or cytotoxic tissue edema. Recent clinical evidence has shown that large artery vasospasm is not the only cause of DCI, and that both large artery vasospasm-dependent and -independent cerebral infarction causes poor outcome. Animal studies suggest that mechanisms of vasospasm may differ between large artery and arterioles or capillaries, and that many kinds of cells in the vascular wall and brain parenchyma may be involved in the pathogenesis of microcirculatory disturbances. The impairment of the paravascular and glymphatic systems also may play important roles in the development of DCI. As pathological mediators for DCI, glutamate and several matricellular proteins have been investigated in addition to inflammatory molecules. Glutamate is involved in excitotoxicity contributing to cortical spreading ischemia and epileptic activity-related events. Microvascular dysfunction is an attractive mechanism to explain the cause of poor outcomes independently of large cerebral artery vasospasm, but needs more studies to clarify the pathophysiologies or mechanisms and to develop a novel therapeutic strategy.

Delayed Cerebral Infarction is Systematically Associated with a Cerebral Vasospasm of Large Intracranial Arteries.

Whether delayed cerebral infarction (DCIn) after aneurysmal subarachnoid hemorrhage (aSAH) is driven by large artery vasospasm is still controversial. To study the association between DCIn and vasospasm by using quantitative assessment of vasospasm up to distal arteries with time and territorial-based correlation. Clinical and imaging data of 392 patients with aSAH treated at our center between 2012 and 2017 were reviewed. DCIn was defined as any cerebral infarction occurring within 3 to 21 d after ictus and not related to other specific cause. In patients with DCIn, vasospasm was assessed within 24 h around DCIn for each cerebral artery up to the end of the 2nd segments. DCIn and vasospasm analyses were blinded. DCIn was found in 11% of patients (inter-rater k=0.90, computed tomography (CT)-scan=100%, follow-up MRI=91%). Vasospasm was quantified in 258 artery territories including 66 with and 192 without DCIn (DSA=93%, computed tomography angiography =7%). Vasospasm was more severe in DCIn than in non-DCIn territories (60% [55-69] vs 20% [0-50], P<.001). Vasospasm was associated with DCIn in a "dose-dependent" manner (P for trend=.022). Every DCIn territory had a vasospasm≥50%, including 39% only of distal artery segments. Only 9% of non-DCIn territories had vasospasm≥vasospasm in DCIn territories. The necessary association between severe vasospasm and DCIn in our study brings additional arguments in favor of large artery vasospasm (especially of distal segments) as a major determinant of DCIn and a potential therapeutic target.

Longitudinal imaging and evaluation of SAH-associated cerebral large artery vasospasm in mice using micro-CT and angiography

Longitudinal in vivo imaging studies characterizing subarachnoid hemorrhage (SAH)-induced large artery vasospasm (LAV) in mice are lacking. We developed a SAH-scoring system to assess SAH severity in mice using micro CT and longitudinally analysed LAV by intravenous digital subtraction angiography (i.v. DSA). Thirty female C57Bl/6J-mice (7 sham, 23 SAH) were implanted with central venous ports for repetitive contrast agent administration. SAH was induced by filament perforation. LAV was assessed up to 14 days after induction of SAH by i.v. DSA. SAH-score and neuroscore showed a highly significant positive correlation (rsp = 0.803, p < 0.001). SAH-score and survival showed a negative significant correlation (rsp = −0.71, p < 0.001). LAV peaked between days 3–5 and normalized on days 7–15. Most severe LAV was observed in the internal carotid (Δmax = 30.5%, p < 0.001), anterior cerebral (Δmax = 21.2%, p = 0.014), middle cerebral (Δmax = 28.16%, p < 0.001) and basilar artery (Δmax = 23.49%, p < 0.001). Cerebral perfusion on day 5 correlated negatively with survival time (rPe = −0.54, p = 0.04). Arterial diameter of the left MCA correlated negatively with cerebral perfusion on day 3 (rPe = −0.72, p = 0.005). In addition, pseudoaneurysms arising from the filament perforation site were visualized in three mice using i.v. DSA. Thus, micro-CT and DSA are valuable tools to assess SAH severity and to longitudinally monitor LAV in living mice.

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

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. 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. 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. 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.

Reversal of Vasospasm with Clazosentan After Aneurysmal Subarachnoid Hemorrhage: A Pilot Study

Clazosentan, an endothelin-1 receptor antagonist, has been shown to prevent the development of large vessel angiographic vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). It has been hypothesized that clazosentan can also reverse established angiographic vasospasm. The REVERSE (resynchronization reverses remodeling in systolic left ventricular dysfunction) study was a prospective, multicenter, open-label, 2-stage pilot study of adult patients with aSAH who had received intravenous clazosentan (15 mg/hour) after developing moderate-to-severe angiographic vasospasm. The primary efficacy endpoint was the reversal of global cerebral vasospasm in large cerebral artery segments 3 hours after clazosentan initiation. The secondary endpoints included large artery vasospasm reversal at 24 hours and the maximum change in the angiographic cerebral circulation time. The change in vasospasm severity in the proximal and distal segments was investigated in an exploratory analysis. The primary efficacy endpoint was met in 3 of 11 evaluable patients (27.3%; 95% confidence interval, 6.0-61.0). However, recruitment was stopped after stage 1 in accordance with the predefined interim analysis criteria. In the exploratory analysis, 50.0% and 77.8% of the patients showed a significant reversal of vasospasm or improvement to the admission state in ≥2 distal segments at 3 and 24 hours and 28.6% and 77.8% in ≥2 proximal segments, respectively. Although the main analysis showed a reversal of large vessel vasospasm 3 hours after clazosentan initiation in a few patients, the exploratory analysis indicated a clear pharmacodynamic dilating effect on vasospastic cerebral vessels at 24 hours in most patients, in particular, in the distal arterial beds. This observation supported the inclusion of patients with established vasospasm in the ongoing REACT (prevention and treatment of vasospasm with clazosentan) trial.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need.

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish. Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits. We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility. To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Long-Lasting Cerebral Vasospasm, Microthrombosis, Apoptosis and Paravascular Alterations Associated with Neurological Deficits in a Mouse Model of Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality and morbidity. Long-term cognitive and sensorimotor deficits are serious complications following SAH but still not well explained and described in mouse preclinical models. The aim of our study is to characterize a well-mastered SAH murine model and to establish developing pathological mechanisms leading to cognitive and motor deficits, allowing identification of specific targets involved in these long-term troubles. We hereby demonstrate that the double blood injection model of SAH induced long-lasting large cerebral artery vasospasm (CVS), microthrombosis formation and cerebral brain damage including defect in potential paravascular diffusion. These neurobiological alterations appear to be associated with sensorimotor and cognitive dysfunctions mainly detected 10days after the bleeding episode. In conclusion, this characterized model of SAH in mice, stressing prolonged neurobiological pathological mechanisms and associated sensitivomotor deficits, will constitute a validated preclinical model to better decipher the link between CVS, long-term cerebral apoptosis and cognitive disorders occurring during SAH and to allow investigating novel therapeutic approaches in transgenic mice.

Prediction of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage Using Cerebral Blood Flow Velocities and Cerebral Autoregulation Assessment.

The risk of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) is associated with large cerebral artery vasospasm, but vasospasm is not a strong predictor for DCI. Assessment of cerebral autoregulation with transcranial Doppler (TCD) may improve the prediction of DCI. The aim of this prospective study was to assess the value of TCD-derived variables to be used alone or in combination for prediction of DCI. We included consecutive patients with low-grade aneurysmal SAH within 4 days of aneurysm rupture. Cerebral autoregulation was evaluated using the moving correlation coefficient Mx calculated from spontaneous fluctuations of cerebral blood flow velocities and arterial blood pressure. Transcranial color-coded sonography was performed to assess large artery vasospasm. Thirty patients (19 women and 11 men; mean age ± SD 44.7 ± 12.1 years) were included. Twenty (66.7%) patients had vasospasm. DCI occurred in six (20%) patients after a median delay of 10 days (range 8-13 days). Cerebral autoregulation was impaired at baseline and at day 7 and then returned to normal at day 14. Neither cerebral autoregulation impairment nor large artery vasospasm alone was associated with DCI. In contrast, the combination of large artery vasospasm with worsening impairment of cerebral autoregulation from baseline to day 7 was significantly correlated to subsequent DCI (p = 0.007). Early deterioration of cerebral autoregulation was strongly predictive of DCI in patients with large artery vasospasm after low-grade SAH. Our results suggest that consideration to both cerebral blood flow velocities and cerebral autoregulation may improve the prediction of DCI.

Mouse genetic background is associated with variation in secondary complications after subarachnoid hemorrhage.

Spontaneous subarachnoid hemorrhage (SAH) is a form of hemorrhagic stroke that accounts for approximately 7 % of all strokes worldwide and is associated with mortality in approximately 35 % of cases and morbidity in many of the survivors. Studies have suggested that genetic variations may affect the pathophysiology of SAH. The goal of this study was to investigate the effect of mouse genetic background on brain injury and large artery vasospasm after SAH. SAH was induced in seven inbred strains of mice, and the degree of large artery vasospasm and brain injury was assessed. After 48 h, SAH mice showed a significant reduction in middle cerebral artery diameter and increased neuronal injury in the cerebral cortex compared with sham-operated controls. Mouse strains also demonstrated variable degrees of vasospasm and brain injury. This data suggests that different genetic factors influence how much brain injury and vasospasm occur after SAH. Future investigations may provide insight into the causes of these differences between strains and into which genetic contributors may be responsible for vasospasm and brain injury after SAH.

Abstract WP262: Therapeutically Targeting TNFa-S1P Signaling Restores Microvascular Reactivity after Experimental Subarachnoid Hemorrhage

Background: Subarachnoid hemorrhage (SAH) is characterized by an initial hemorrhagic and ischemic brain injury followed by delayed macro- and microvascular constriction. Large-artery vasospasm and enhanced microcirculatory myogenic tone may contribute to delayed cerebral ischemia. Although this implies that therapeutic interventions must specifically correct the SAH-induced myogenic tone enhancement, current therapeutic approaches non-selectively interfere with vasoconstriction and risk disrupting cerebral autoregulation. This may explain why most interventions do not improve clinical outcome. This study identifies the molecular basis for exacerbated cerebrovascular constriction and validates new targets for SAH treatment. Methods: Wild-type, tumor necrosis factor α (TNFα) knockout, sphingosine-1-kinase (Sphk1) knockout and inducible, smooth muscle cell-targeted TNFα knockout mice were used. SAH was created by injection of 80 μl of arterial blood into the prechiasmatic cistern. Myogenic tone in the olfactory artery was assessed with a myograph system. Standard procedures for fluorescent immunolocalization, Western blotting and assessment of apoptosis were used. Results: SAH increased myogenic tone and vascular wall TNFα expression, without enhancing overall vascular contractility in response to phenylephrine. Knockout of TNFα globally or smooth muscle cell-specifically prevented SAH-induced increased myogenic tone. Inhibition of TNFα-shedding (TAPI, 50 μmol/L) or receptor-binding (etanercept, 10 mg/ml) eliminated SAH-mediated myogenic tone augmentation. Cystic fibrosis transmembrane regulator (CFTR) protein expression was down-regulated in cerebral arteries after SAH, which was abolished by antagonism of TNFα. Genetic mouse models confirmed that S1P signaling mediates the myogenic tone augmentation in SAH. Finally, disrupting TNFα signaling attenuated neuronal apoptosis in SAH animals. Conclusion: We identify a novel smooth muscle cell autocrine/paracrine signaling network that augments myogenic tone in SAH. It links TNFα, CFTR and sphingosine-1-phosphate (S1P) signaling. Targeting TNFα and the S1P 2 receptor subtype are potential therapeutic options to improve clinical outcome in SAH.