Vasospasm in monkeys resolves because of loss of and encasement of subarachnoid blood clot

Lessons for the pathogenesis of vasospasm from a patient with sickle cell disease, moyamoya disease, subarachnoid hemorrhage, and 1 month of persistent vasospasm: illustrative case

BACKGROUND

The mechanism of vasospasm post–subarachnoid hemorrhage (post-SAH) is a poorly understood yet devastating complication that can result in delayed ischemic neurological damage. High concentrations of free hemoglobin present in hemolytic conditions reduce nitric oxide (NO) availability which may disrupt vascular dynamics and contribute to the extent of vasospasm.

OBSERVATIONS

The authors describe the clinical course of a sickle cell disease (SCD) patient with spontaneous SAH who suffered an abnormally long duration of vasospasm. The authors then present a focused review of the pathology of intravascular hemolysis and discuss the potential key role of intravascular hemolysis in the pathogenesis of cerebral vasospasm as illustrated in this case lesson.

LESSONS

Abnormally prolonged and severe vasospasm in SCD with SAH may provide clues regarding the mechanisms of vasospasm. Intravascular hemolysis limits NO availability and may contribute to the development of vasospasm following SAH.

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.

A Comparison of Pathophysiology in Humans and Rodent Models of Subarachnoid Hemorrhage

Non-traumatic subarachnoid hemorrhage (SAH) affects an estimated 30,000 people each year in the United States, with an overall mortality of ~30%. Most cases of SAH result from a ruptured intracranial aneurysm, require long hospital stays, and result in significant disability and high fatality. Early brain injury (EBI) and delayed cerebral vasospasm (CV) have been implicated as leading causes of morbidity and mortality in these patients, necessitating intense focus on developing preclinical animal models that replicate clinical SAH complete with delayed CV. Despite the variety of animal models currently available, translation of findings from rodent models to clinical trials has proven especially difficult. While the explanation for this lack of translation is unclear, possibilities include the lack of standardized practices and poor replication of human pathophysiology, such as delayed cerebral vasospasm and ischemia, in rodent models of SAH. In this review, we summarize the different approaches to simulating SAH in rodents, in particular elucidating the key pathophysiology of the various methods and models. Ultimately, we suggest the development of standardized model of rodent SAH that better replicates human pathophysiology for moving forward with translational research.

The supraorbital endoscopic approach for aneurysms

OBJECTIVE

To review our surgical experience in minimally invasive transcranial endoscope-assisted microsurgical treatment of intracranial aneurysms, using the supraorbital keyhole craniotomy.

METHODS

The supraorbital keyhole approach was performed through an eyebrow skin incision in 793 cases for treatment of 989 intracranial aneurysms. Of patients, 474 were operated on after subarachnoid hemorrhage, and 319 were operated on under elective conditions. After lateral frontobasal burr hole trephination, a limited subfrontal craniotomy was created. To achieve adequate intraoperative exposure through the limited approach, endoscopes were used routinely. Surgical outcome was assessed using the modified Rankin scale.

RESULTS

The transcranial endoscope-assisted microneurosurgery technique was used routinely via a supraorbital approach. In 152 operations (19.1%), the endoscope provided important visual information in the vicinity of the aneurysm, revealing subsequent clip repositioning. The results of incidental aneurysms were excellent with a modified Rankin scale score ≤2 in 96.52%. The overall outcome of ruptured aneurysms was good with a modified Rankin scale score ≤2 in 72.2% of patients. There were no approach-related intraoperative or postoperative complications.

CONCLUSIONS

The minimally invasive supraorbital keyhole approach allowed safe surgical treatment of intracranial aneurysms, including after subarachnoid hemorrhage. The markedly improved endoscopic visualization increased the assessment of clip placement with ideal control of surrounding vessels including perforators for identification of incorrect clip position.

Controversies and evolving new mechanisms in subarachnoid hemorrhage

Despite decades of study, subarachnoid hemorrhage (SAH) continues to be a serious and significant health problem in the United States and worldwide. The mechanisms contributing to brain injury after SAH remain unclear. Traditionally, most in vivo research has heavily emphasized the basic mechanisms of SAH over the pathophysiological or morphological changes of delayed cerebral vasospasm after SAH. Unfortunately, the results of clinical trials based on this premise have mostly been disappointing, implicating some other pathophysiological factors, independent of vasospasm, as contributors to poor clinical outcomes. Delayed cerebral vasospasm is no longer the only culprit. In this review, we summarize recent data from both experimental and clinical studies of SAH and discuss the vast array of physiological dysfunctions following SAH that ultimately lead to cell death. Based on the progress in neurobiological understanding of SAH, the terms "early brain injury" and "delayed brain injury" are used according to the temporal progression of SAH-induced brain injury. Additionally, a new concept of the vasculo-neuronal-glia triad model for SAH study is highlighted and presents the challenges and opportunities of this model for future SAH applications.

Mechanisms, treatment and prevention of cellular injury and death from delayed events after aneurysmal subarachnoid hemorrhage

INTRODUCTION

Subarachnoid hemorrhage (SAH) patients often develop brain injury as a result of a number of delayed complications, resulting in significant morbidity and mortality. Many of these complications arise due to delayed cerebral ischemia, which occurs secondary to the hemorrhage.

AREAS COVERED

The mechanisms of the delayed injury are reviewed, including angiographic vasospasm, cortical spreading ischemia, small arteriolar constriction, microthromboemboli, free radical injury and inflammation. Some current and prospective therapies for SAH are discussed, in the context of these complications. Statins have been particularly promising in experimental studies.

EXPERT OPINION

Multiple mechanisms are involved in the pathogenesis of the delayed insult after SAH. New drugs may need to target multiple pathways to injury. Trials aiming to treat complications after SAH could benefit from taking into account the multifactorial pathogenesis of delayed insults.

Treatment modality and vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Vasospasm is the leading source of neurological morbidity after aneurysmal subarachnoid hemorrhage. Our objective was to evaluate the impact of treatment modality on vasospasm, delayed cerebral infarction, and clinical deterioration caused by delayed cerebral ischemia (CD-DCI).

METHODS

We reviewed an institutional cohort, comparing rates of vasospasm, delayed cerebral infarction, and CD-DCI between patients managed with only microsurgical clipping and those treated with only endovascular coiling within 72 hours of rupture. Age, sex, smoking status, Hunt-Hess grade, and Fisher grade were adjusted for in a multivariate regression model.

RESULTS

Two hundred three patients were treated with clipping and 52 with coiling. There was no significant difference in patient age, sex, smoking status, aneurysm location, and presenting clinical (Hunt-Hess) and radiographic (Fisher) grade between these two groups. Sixty-percent of patients had moderate or severe vasospasm after clipping compared with 38% after coiling (Multivariate odds ratio [OR] 2.32, 95% confidence interval [95% CI] 1.21-4.47, P = 0.01). Clipping was associated with a greater number of territories with vasospasm (mean of 3.1 vs. 2.3, P = 0.03 after multivariate analysis). Delayed radiographic cerebral infarction was more common in the clipping group (17% vs. 6%, multivariate OR 3.66, 95% CI 1.06-12.71, P = 0.04). For CD-DCI, a trend was seen as 16% of patients treated with clipping had CD-DCI compared with 6% of patients treated with coiling (multivariate OR 3.11, 95% CI 0.89-10.86, P = 0.07).

CONCLUSION

We demonstrate significantly lower rates of vasospasm and delayed infarction after endovascular coiling of ruptured aneurysms.

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Method of Aneurysm Treatment Does Not Affect Clot Clearance After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Patients undergoing neurosurgical clipping or endovascular coiling of a ruptured aneurysm may differ in their risk of vasospasm.

OBJECTIVE

Because clot clearance affects vasospasm, we tested the hypothesis that clot clearance differs in patients depending on method of aneurysm treatment.

METHODS

Exploratory analysis was performed on 413 patients from CONSCIOUS-1, a prospective randomized trial of clazosentan for the prevention of angiographic vasospasm in patients with aneurysmal subarachnoid hemorrhage (SAH). Clot clearance was measured by change in Hijdra score between baseline computed tomography and one performed 24 to 48 hours after aneurysm treatment. Angiographic vasospasm was assessed by the use of catheter angiography 7 to 11 days after SAH, and delayed ischemic neurological deficit (DIND) was determined clinically. Extended Glasgow Outcome Score (GOSE) was assessed 3 months after SAH, and poor outcome was defined as death, vegetative state, or severe disability. Multivariable ordinal and binary logistic regression were used.

RESULTS

There was no significant difference in the rate of clot clearance between patients undergoing clipping or coiling (P = .56). Coiling was independently associated with decreased severity of angiographic vasospasm (odds ratio [OR] 0.53, 95% confidence interval [CI] 0.33-0.86), but not with DIND or GOSE. Greater clot clearance decreased the risk of severe angiographic vasospasm (OR 0.86, 95% CI 0.81-0.91), whereas higher baseline Hijdra score predicted increased angiographic vasospasm (OR 1.17, 95% CI 1.11-1.23) and poor GOSE (OR 1.09, 95% CI 1.04-1.14).

CONCLUSION

Aneurysm coiling and increased clot clearance were independently associated with decreased severity of angiographic vasospasm in multivariate analysis, although no differences in clot clearance were seen between coiled and clipped patients.

Role of CT perfusion imaging in the diagnosis and treatment of vasospasm

The current role of CT perfusion (CTP) imaging in the diagnosis and treatment of vasospasm in the setting of aneurysmal subarachnoid hemorrhage is discussed in this article, with specific attention directed towards defining the terminology of vasospasm and delayed cerebral ischemia. A commonly used CTP technique in clinical practice is described. A review of the literature regarding the usefulness of CTP for the diagnosis of vasospasm and its role in guiding treatment are discussed. Recent research advances in the utilization of CTP and associated ongoing challenges are also presented.

Sphenopalatine ganglion stimulation for vasospasm after experimental subarachnoid hemorrhage

Object

Sphenopalatine ganglion stimulation activates perivascular vasodilatory nerves in the ipsilateral anterior circle of Willis. This experiment tested whether stimulation of the ganglion could reverse vasospasm and improve cerebral perfusion after subarachnoid hemorrhage (SAH) in monkeys.

Methods

Thirteen cynomolgus monkeys underwent baseline angiography followed by creation of SAH by placement of autologous blood against the right intradural internal carotid artery, the middle cerebral artery (MCA), and the anterior cerebral artery. Seven days later, angiography was repeated, and the right sphenopalatine ganglion was exposed microsurgically. Angiography was repeated 15 minutes after exposure of the ganglion. The ganglion was stimulated electrically 3 times, and angiography was repeated during and 15 and 30 minutes after stimulation. Cerebral blood flow (CBF) was monitored using laser Doppler flowmetry, and intracranial pressure (ICP) was measured throughout. The protocol was repeated again. Evans blue was injected and the animals were killed. The brains were removed for analysis of water and Evans blue content and histology.

Results

Subarachnoid hemorrhage was associated with significant vasospasm of the ipsilateral major cerebral arteries (23% ± 10% to 39% ± 4%; p < 0.05, paired t-tests). Exposure of the ganglion and sham stimulation had no significant effects on arterial diameters, ICP, or CBF (4 monkeys, ANOVA and paired t-tests). Sphenopalatine ganglion stimulation dilated the ipsilateral extracranial and intracranial internal carotid artery, MCA, and anterior cerebral artery compared with the contralateral arteries (9 monkeys, 7% ± 9% to 15% ± 19%; p < 0.05, ANOVA). There was a significant increase in ipsilateral CBF. Stimulation had no effect on ICP or brain histology. Brain water content did not increase but Evans blue content was significantly elevated in the MCA territory of the stimulated hemisphere.

Conclusions

Sphenopalatine ganglion stimulation decreased vasospasm and increased CBF after SAH in monkeys. This was associated with opening of the blood-brain barrier.

Current perspective on the role of the thrombin receptor in cerebral vasospasm after subarachnoid hemorrhage

Cerebral vasospasm is a persistent arterial narrowing typically observed during the 3 - 14 days after subarachnoid hemorrhage (SAH). Vasospasm is frequently associated with ischemic neurological deficits or even death, resulting in a poor prognosis for patients with SAH. However, the mechanism underlying cerebral vasospasm remains elusive, and no effective therapeutic strategies have been established. A large amount of thrombin is produced during SAH. Recent investigations have uncovered a key role of the thrombin receptor in the pathogenesis of cerebral vasospasm. Thrombin has little contractile effect in the normal cerebral artery, but it induces an enhanced and prolonged contraction after SAH, owing to the up-regulation of thrombin receptor PAR(1) (proteinase-activated receptor 1) and the impairment of receptor desensitization in arterial smooth muscle. Thrombin-mediated activation of PAR(1) is an irreversible process, as it is initiated by the proteolytic removal of the N-terminal region. Since the mechanism of receptor desensitization is impaired after SAH, the thrombin-induced contraction irreversibly persists even after terminating thrombin stimulation. Intrathecal administration of a PAR(1) antagonist prevents the PAR(1) up-regulation and the increased reactivity to thrombin. PAR(1) is suggested to play a key role in cerebral vasospasm and may be useful as a therapeutic target for prevention and treatment of cerebral vasospasm.

Equal contribution of increased intracranial pressure and subarachnoid blood to cerebral blood flow reduction and receptor upregulation after subarachnoid hemorrhage. Laboratory investigation

OBJECT

Cerebral ischemia remains the key cause of disability and death in the late phase after subarachnoid hemorrhage (SAH), and its pathogenesis is still poorly understood. The purpose of this study was to examine whether the change in intracranial pressure or the extravasated blood causes the late cerebral ischemia and the upregulation of receptors or the cerebral vasoconstriction observed following SAH.

METHODS

Rats were allocated to 1 of 3 experimental conditions: 1) cisternal injection of 250 microl blood (SAH Group), 2) cisternal injection of 250 microl NaCl (Saline Group), or 3) the same procedure but without fluid injection (Sham Group). Two days after the procedure, the basilar and middle cerebral arteries were harvested, and contractile responses to endothelin (ET)-1 and 5-carboxamidotryptamine (5-CT) were investigated by means of myography. In addition, real-time polymerase chain reaction was used to determine the mRNA levels for ET(A), ET(B), and 5-HT(1) receptors. Regional and global cerebral blood flow (CBF) were quantified by means of an autoradiographic technique.

RESULTS

Compared with the sham condition, both SAH and saline injection resulted in significantly enhanced contraction of cerebral arteries in response to ET-1 and 5-CT. Regional and global CBF were reduced both in the Saline and SAH groups compared with the Sham Group. The mRNA levels for ET(B) and 5-HT(1B) receptors were upregulated after SAH and saline injection compared with the sham procedure. The effects in all parameters were more pronounced for SAH than for saline injection.

CONCLUSIONS

This study revealed that both the elevation of intracranial pressure and subarachnoid blood per se contribute approximately equally to the late CBF reductions and receptor upregulation following SAH.

Subarachnoid hemorrhage and the distribution of drugs delivered into the cerebrospinal fluid. Laboratory investigation

OBJECT

Investigators in experimental and clinical studies have used the intrathecal route to deliver drugs to prevent or treat vasospasm. However, a clot near an artery or arteries after subarachnoid hemorrhage (SAH) may hamper distribution and limit the effects of intrathecally delivered compounds. In a primate model of right middle cerebral artery (MCA) SAH, the authors examined the distribution of Isovue-M 300 and 3% Evans blue after infusion into the cisterna magna CSF.

METHODS

Ten cynomolgus monkeys were assigned to SAH and sham SAH surgery groups (5 in each group). Monkeys received CSF injections as long as 28 days after SAH and were killed 3 hours after the contrast/Evans blue injection. The authors assessed the distribution of contrast material on serial CT within 2 hours after contrast injection and during autopsy within 3 hours after Evans blue staining.

RESULTS

Computed tomography cisternographies showed no contrast in the vicinity of the right MCA (p < 0.05 compared with left); the distribution of contrast surrounding the entire right cerebral hemisphere was substantially reduced. Postmortem analysis demonstrated much less Evans blue staining of the right hemisphere surface compared with the left. Furthermore, the Evans blue dye did not penetrate into the right sylvian fissure, which occurred surrounding the left MCA. The authors observed the same pattern of changes and differences in contrast distribution between SAH and sham SAH animals and between the right and the left hemispheres on Days 1, 3, 7, 14, 21, and 28 after SAH.

CONCLUSIONS

Intrathecal drug distribution is substantially limited by SAH. Thus, when using intrathecal drug delivery after SAH, vasoactive drugs are unlikely to reach the arteries that are at the highest risk of delayed cerebral vasospasm.

Pathogenesis of cerebral vasospasm following aneurysmal subarachnoid hemorrhage: putative mechanisms and novel approaches

Cerebral vasospasm is a potentially incapacitating or lethal complication in patients with aneurysmal subarachnoid hemorrhage (SAH). The development of effective preventative and therapeutic interventions has been largely hindered by the fact that the underlying pathogenic mechanisms of cerebral vasospasm remain poorly understood. However, intensive research during the last 3 decades has identified certain mechanisms that possibly play a role in its development. Experimental data suggest that calcium-dependent and -independent vasoconstriction is taking place during vasospasm. It appears that the breakdown products of blood in the subarachnoid space are involved, through direct and/or indirect pathways, in the development of vasospasm after SAH. Free radicals reactions, an imbalance between vasoconstrictor and vasodilator substances (endothelium derived substances, e.g., nitric oxide, endothelin; arachidonic acid metabolites, e.g., prostaglandins, prostacyclin), inflammatory processes, an upheaval of neuronal mechanisms that regulate vascular tone, endothelial proliferation, and apoptosis have all been put forward as causative and/or pathogenic factors. Translational research in the field of vasospasm has traditionally aimed to identify agents/interventions in order to block the cascades initiated after SAH. The combination of novel approaches such as cerebral microdialysis, magnetic resonance spectroscopy, proteomics, and lipidomics could serve a dual purpose: elucidating the complex pathobiochemistry of vasospasm and providing clinicians with tools for early detection of this feared complication. The purpose of this Mini-Review is to provide an overview of the pathogenesis of cerebral vasospasm and of novel approaches used in basic and translational research.

Comparison between clipping and coiling on the incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis

Cerebral vasospasm is one of the most important complications of aneurysmal subarachnoid hemorrhage. The effect of aneurysm occlusion technique on incidence of vasospasm is not exactly known. The objective was to analyze surgical clipping versus endovascular coiling on the incidence of cerebral vasospasm and its consequences. Using the MEDLINE PubMed (1966-present) database, all English-language manuscripts comparing patients treated by surgical clipping with patients treated by endovascular coiling, regarding vasospasm incidence after aneurysmal subarachnoid hemorrhage, were analyzed. Data extracted from eligible studies included the following outcome measures: incidence of total vasospasm, symptomatic vasospasm, ischemic infarct vasospasm-induced and delayed ischemic neurological deficit (DIND). A pooled estimate of the effect size was computed and the test of heterogeneity between studies was carried out using The Cochrane Collaboration's Review Manager software, RevMan 4.2. Nine manuscripts that fulfilled the eligibility criteria were included and analyzed. The studies differed substantially with respect to design and methodological quality. The overall results showed no significant difference between clipping and coiling regarding to outcome measures. According to the available data, there is no significant difference between the types of technique used for aneurysm occlusion (clipping or coiling) on the risk of cerebral vasospasm development and its consequences.

Evidence-based cerebral vasospasm management

Cerebral vasospasm and delayed cerebral ischemia remain common complications of aneurysmal subarachnoid hemorrhage (SAH), and yet therapies for cerebral vasospasm are limited. Despite a large number of clinical trials, only calcium antagonists have strong evidence supporting their effectiveness. The purpose of this work was to perform a systematic review of the literature on the treatment of cerebral vasospasm. A literature search for randomized controlled trials of therapies used for prevention or treatment of cerebral vasospasm and/or delayed cerebral ischemia was conducted, and 41 articles meeting the review criteria were found. Study characteristics and primary results of these articles are reviewed. Key indicators of quality were poor when averaged across all studies, but have improved greatly over time. The only proven therapy for vasospasm is nimodipine. Tirilazad is not effective, and studies of hemodynamic maneuvers, magnesium, statin medications, endothelin antagonists, steroid drugs, anticoagulant/antiplatelet agents, and intrathecal fibrinolytic drugs have yielded inconclusive results. The following conclusions were made: nimodipine is indicated after SAH and tirilazad is not effective. More study of hemodynamic maneuvers, the effectiveness of other calcium channel antagonists such as nicardipine delivered by other routes (for example intrathecally), magnesium, statin drugs, endothelin antagonists, and intrathecal fibrinolytic therapy is warranted. There is less enthusiasm for the study of steroid drugs and anticoagulant/antiplatelet agents because they entail more risks and investigations so far have shown little evidence of efficacy. The study of rescue therapy such as balloon angioplasty and intraarterial vasodilating agents will be difficult. The quality of clinical trials should be improved.

Management of cerebral vasospasm

Cerebral vasospasm is delayed narrowing of the large arteries of the circle of Willis occurring 4 to 14 days after aneurysmal subarachnoid hemorrhage (SAH). It is but one cause of delayed deterioration after SAH but, in general, is the most important potentially treatable cause of morbidity and mortality after SAH. Development of vasospasm is best predicted by the volume, location, persistence and density of subarachnoid clot early after SAH. Diagnosis is made by catheter angiography or, with less accuracy, by computed tomographic angiography, transcranial Doppler ultrasound or other methods. Treatment remains problematic because it is expensive, time-consuming, associated with substantial risk and largely ineffective. Treatment includes optimization of factors that affect cerebral blood flow and metabolism, systemic administration of nimodipine, hemodynamic therapy and pharmacologic and mechanical angioplasty.

Molecular profile of vascular ion channels after experimental subarachnoid hemorrhage

Cerebral vasospasm is a transient, delayed constriction of cerebral arteries that occurs after subarachnoid hemorrhage (SAH). Smooth muscle cells show impaired relaxation after SAH, which may be caused by a defect in the ionic mechanisms regulating smooth muscle membrane potential and Ca(2+) permeability. We tested this hypothesis by examining changes in expression of mRNA and protein for ion channels in the basilar arteries of dogs after SAH using quantitative real-time polymerase chain reaction (PCR) and western blotting. SAH was associated with a significant reduction in basilar artery diameter to 41 +/- 8% of pre-SAH diameter (P < 0.001) after 7 days. There was significant downregulation of the voltage-gated K(+) channel K(v) 2.2 (65% reduction in mRNA, P < 0.001; 49% reduction in protein, P < 0.05) and the beta1 subunit of the large-conductance, Ca(2+) - activated K(+) (BK) channel (53% reduction in mRNA, P < 0.02). There was no change in BK beta1 subunit protein. Changes in mRNA levels of K(v) 2.2 and the BK-beta1 subunit correlated with the degree of vasospasm (r(2) = 0.490 and 0.529 respectively, P < 0.05). The inwardly rectifying K(+) (K(ir)) channel K(ir) 2.1 was upregulated (234% increase in mRNA, P < 0.001; 350% increase in protein, P < 0.001). There was no significant change in mRNA expression of L- type Ca(2+) channels and the BK-alpha subunit. These data suggest that K(+) channel dysfunction may contribute to the pathogenesis of cerebral vasospasm.

A murine model of subarachnoid hemorrhage-induced cerebral vasospasm

Cerebral vasospasm remains a major cause of morbidity and mortality after subarachnoid hemorrhage (SAH). The availability of a mouse model of SAH that is simple, replicable and has low mortality would provide a powerful approach for understanding cellular and molecular mechanisms contributing to post-SAH pathologies. The present study characterizes a mouse model of experimental SAH, which produces consistent constriction of large cerebral arteries. Adult mice received injections of autologous blood into the cisterna magna, and the diameters of large intracranial vessels were measured 1 h to 7 days post-SAH. A diffuse blood clot was evident in both the anterior and posterior circulations after SAH. Vascular wall thickening, lumenal narrowing and corrugation of the internal elastic lamina were observed. Both acute (6-12 h) and delayed (1-3 days) phases of vasoconstriction occurred after SAH. Overall mortality was only 3%. A reproducible, low mortality model of SAH-induced cerebral vasospasm in mice is described. This mouse model should facilitate the delineation of cellular and molecular mechanisms of SAH-induced pathologies because of the widespread availability of various technologies for this species (e.g. genetically-altered animals and gene expression arrays). This model also represents a replicable and inexpensive approach for screening therapeutic candidates.

Symptomatic vasospasm and outcomes following aneurysmal subarachnoid hemorrhage: a comparison between surgical repair and endovascular coil occlusion

OBJECT

The authors studied patients with aneurysmal subarachnoid hemorrhage (SAH) to determine whether the incidence of symptomatic vasospasm or overall clinical outcomes differed between patients treated with craniotomy and clip application and those treated by endovascular coil occlusion.

METHODS

The authors reviewed 415 consecutive patients with aneurysmal SAH who had been treated with either craniotomy and clip application or endovascular coil occlusion at a single institution between 1990 and 2000. Three hundred thirty-nine patients underwent surgical clip application procedures, whereas 76 patients underwent endovascular coil occlusion. Symptomatic vasospasm occurred in 39% of patients treated with clip application, 30% of patients treated with endovascular coil occlusion, and 37% of patients overall. Compared with patients treated with clip application, patients treated with endovascular coil occlusion were more likely to suffer acute hydrocephalus (50 compared with 34%, p = 0.008) and were more likely to harbor aneurysms in the posterior circulation (53 compared with 20%, p < 0.001). Logistic regression models controlling for patient age, admission World Federation of Neurosurgical Societies (WFNS) grade, acute hydrocephalus, aneurysm location, and day of treatment revealed that, among patients with an admission WFNS grade of I to III, endovascular coil occlusion carried a lower risk of symptomatic vasospasm (odds ratio [OR] 0.34, 95% confidence interval [CI] 0.14-0.8) and death or permanent neurological deficit due to vasospasm (OR 0.28, 95% CI 0.08-1) compared with craniotomy and clip application. Similar models revealed no difference in the likelihood of a Glasgow Outcome Scale score of 3 or less at the longest follow-up review (median 6 months) between treatment groups (OR 0.58, 95% CI 0.28-1.21).

CONCLUSIONS

Patients with better clinical grades (WFNS Grades I-III) at hospital admission were less likely to suffer symptomatic vasospasm when treated by endovascular coil occlusion, compared with craniotomy and clip application. Nevertheless, there was no significant difference in overall outcome at the longest follow-up examination between the two treatment groups.