The novel 5-lipoxygenase inhibitor ABT-761 attenuates cerebral vasospasm in a rabbit model of subarachnoid hemorrhage

OBJECTIVE

Eicosanoids have been implicated in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). Leukotrienes, 5-hydroxyperoxyeicosatetraenoic acid, and 5-hydroxyeicosatetraenoic acid are part of this group of substances, resulting from the 5-lipoxygenase activity on arachidonic acid metabolism. This study examined the effects of ABT-761, a new 5-lipoxygenase inhibitor, on cerebral vasospasm in an in vivo rabbit model of SAH.

METHODS

A total of 48 rabbits were assigned to one of six groups: SAH + placebo (n = 8), SAH + ABT-761 20 mg/kg (n = 8), SAH + ABT-761 30 mg/kg (n = 8), control + placebo (n = 8), control + ABT-761 20 mg/kg (n = 8), and control + ABT-761 30 mg/kg (n = 8). Drug administration was initiated 30 minutes after induction of SAH and repeated 24 hours later. The animals were killed 48 hours after SAH, using the perfusion-fixation method. The cross sectional areas of basilar artery histological sections were measured by an investigator blinded to the treatment groups of the individual samples.

RESULTS

In placebo-treated animals, the average luminal cross sectional area of the basilar artery was reduced by 68% after SAH as compared with controls (P < 0.0001). After SAH, the vasospastic response was attenuated in animals treated with 20 or 30 mg/kg representing a 28 or 35% reduction, respectively (P = 0.0011 and P = 0.0038).

CONCLUSION

The results demonstrated that ABT-761 is effective in attenuating experimental cerebral vasospasm, indicating that this new drug represents a potential therapeutic agent for the treatment of vasospasm after SAH.

Improvement of endothelial function in insulin-resistant carotid arteries treated with pravastatin

OBJECT

Insulin resistance and hypertension are independent risk factors for stroke. Endothelial dysfunction in response to risk factors and carotid artery (CA) disease are important in the pathogenesis of stroke. Pravastatin may have cholesterol-independent pleiotropic effects. In the present study the authors examined the effects of short-course pravastatin treatment on endothelial function in CAs obtained in control and insulin-resistant rats with fructose-induced hypertension.

METHODS

Thirty rats were divided into two experimental groups, in which 14 were fed a regular diet and 16 were fed a fructose-enriched diet for 3 weeks. The rats were then divided into four groups: control, pravastatin-treated control, fructose-fed, and pravastatin-treated fructose-fed. Pravastatin was administered (20 mg/kg/day) for 2 weeks. Excretion of the urinary nitric oxide (NO) metabolite nitrite (NO2-) was also assayed. The CAs from all rats were subsequently removed and assessed for endothelium-dependent and -independent vascular reactivity in vitro. The rats in the fructose-fed group were insulin resistant, hyperinsulinemic, and hypertensive relative to the rats in the control and pravastatin-treated control groups and exhibited diminished endothelium-dependent vasomotion and urinary NO2- excretion (p < 0.05), with preserved endothelium-independent vasomotion. Strikingly, pravastatin treatment restored endothelium-dependent vasomotion and urinary NO2- excretion in rats in the fructose-fed pravastatin-treated relative to the fructose-fed group (p < 0.05).

CONCLUSIONS

The authors report, for the first time, that pravastatin restores endothelial function in CAs from insulin-resistant rats with fructose-induced hypertension. These beneficial effects were ascribed to direct, cholesterol-independent vascular effects of pravastatin and are likely the result of augmentation of NO production. These data provide impetus for further investigation of nonlipid-lowering indications for pravastatin therapy in the prevention and treatment of CA disease.

Radiosurgery-induced microvascular alterations precede necrosis of the brain neuropil

OBJECTIVE

Radiosurgery is used as a therapeutic modality for a wide range of cerebral disorders. It is important to understand the underlying causes of deleterious side effects that may accompany gamma-irradiation of brain tissue. In this study, structural alterations in rat cerebral vessels subjected to gamma knife irradiation in vivo were examined, for elucidation of their potential role in necrosis formation.

METHODS

A maximal center dose of 75 Gy was delivered to the rat parietal cortex with a 4-mm collimator, and changes occurring before necrosis formation were assessed 3.5 months after irradiation. Transmission electron microscopy, using horseradish peroxidase as a tracer, and scanning electron microscopy with vascular casting were performed.

RESULTS

The capillary network in the irradiated area exhibited thickening and vacuolation of the basement membrane. The capillary density in the irradiated area was lower and the average capillary diameter was larger, compared with the nonirradiated side. These results indicate that substantial changes in the neuropil do not occur 2 weeks before the time of definite necrosis formation, whereas changes in the basement membrane are prominent.

CONCLUSION

The necrotic response to intermediate doses of focused-beam irradiation appears after a considerable latency period and then progresses rapidly. This contrasts with previously reported responses to fractionated whole-brain irradiation, in which damage occurs slowly and gradually. Alterations in the microvascular basement membrane precede overt cellular changes in neuronal and vascular cells and provide an early index of cerebrovascular dysfunction in regions destined to undergo necrosis.

Telepresence in neurosurgery: the integrated remote neurosurgical system

This paper describes the Integrated Remote Neurosurgical System (IRNS), a remotely-operated neurosurgical microscope with high-speed communications and a surgeon-accessible user interface. The IRNS will allow high quality bidirectional mentoring in the neurosurgical suite. The research goals of this effort are twofold: to develop a clinical system allowing a remote neurosurgeon to lend expertise to the OR-based neurosurgical team and to provide an integrated training environment. The IRNS incorporates a generic microscope/transport model, Called SuMIT (Surgical Manipulator Interface Translator). Our system is currently under test using the Zeiss MKM surgical transport. A SuMIT interface is also being constructed for the Robotics Research 1607. The IRNS Remote Planning and Navigation Workstation incorporates surgical planning capabilities, real-time, 30 fps video from the microscope and overhead video camera. The remote workstation includes a force reflecting handcontroller which gives the remote surgeon an intuitive way to position the microscope head. Bidirectional audio, video whiteboarding, and image archiving are also supported by the remote workstation. A simulation mode permits pre-surgical simulation, post-surgical critique, and training for surgeons without access to an actual microscope transport system. The components of the IRNS are integrated using ATM switching to provide low latency data transfer. The research, along with the more sophisticated systems that will follow, will serve as a foundation and test-bed for extending the surgeon's skills without regard to time zone or geographic boundaries.

Systemic administration of mexiletine for attenuation of cerebral vasospasm following experimental subarachnoid haemorrhage

Mexiletine is a class Ib drug that is widely used to treat ventricular arrhythmias. This compound is mainly known as a sodium channel blocker, but studies have demonstrated that it can also activate ATP-sensitive K+ channels and block Ca2+ channels. Recent in vitro data from experiments on liposomes indicate that mexiletine is also a potent antioxidant. The unique activity profile of this drug raised the possibility that it might be of benefit in limiting cerebral vasospasm. Our first series of experiments assessed the effects of mexiletine on transclivally exposed rabbit basilar arteries. The arteries were treated with 50-mM KCl, 20-nM endothelin-1 (ET-1), or 100-microM lysophosphatidic acid (LPA) in the presence or absence of 400-mM mexiletine. Vasoconstriction caused by KCl, ET-1, and LPA was inhibited by mexiletine. In a second series of experiments, subarachnoid haemorrhage (SAH) was induced in rabbits by injecting 3-ml of autologous arterial blood into the cisterna magna. Forty-eight hours after SAH induction, transclivally exposed basilar arteries exhibited a spastic constriction that was partially reversed by topical application of 400-microM mexiletine. In a third set of experiments, mexiletine was administered orally at dosages of 80-, 20, and 5-mg/kg/day t.i.d., beginning 3 hours before SAH to study the prevention of vasospasm. In a separate group of animals, 80- and 20-mg/kg/day t.i.d. of mexiletine was administered 21 hours post-SAH induction, to study the reversal of vasoconstriction. Microscopic analysis of vessels from controls (no SAH), SAH-only, and SAH + mexiletine groups indicated there was 71.43% vascular constriction in the SAH-only group compared with controls. Considerable vasorelaxation was seen in the prevention study, in which average arterial cross-sectional areas were reduced by only 17.86% and 39.29% in the mexiletine 80- and 20-mg/kg/day groups, respectively, compared with controls (p < 0.001). Compared with controls, average arterial cross-sectional areas were reduced by 53.58% and 64.29% in the mexiletine 80- and 20-mg/kg/day reversal groups, respectively. Our findings indicate that mexiletine induces potent relaxation in cerebrovascular arteries contracted with various agents, and that it prevents and partially reverses SAH-induced vasoconstriction.

Anticonvulsant effects of gamma surgery in a model of chronic spontaneous limbic epilepsy in rats

OBJECT

The management of intractable epilepsy remains a challenge, despite advances in its surgical and nonsurgical treatment. The identification of low-risk, low-cost therapeutic strategies that lead to improved outcome is therefore an important ongoing goal of basic and clinical research. Single-dose focal ionizing beam radiation delivered at necrosis-inducing and subnecrotic levels was investigated for its effects on seizure activity by using an established model of chronic recurrent spontaneous limbic seizures in rats.

METHODS

A single 90-minute period of repetitive electrical stimulation (inducing stimulus) of the hippocampus in rats elicited a single episode of status epilepticus, followed by a 2- to 4-week seizure-free period. Spontaneous recurrent seizures developed subsequently and persisted for the duration of monitoring (2-10 months). Simultaneous computerized electroencephalography and video recording were used to monitor the animals. After the establishment of spontaneous recurrent seizures, bilateral radiation centered in the ventral hippocampal formation was administered with the Leksell gamma knife, aided by a stereotactic device custom made for small animals. A center dose of 10, 20, or 40 Gy was administered using a 4-mm collimator. Control animals were subjected to the same seizure-inducing stimulus but underwent a sham treatment instead of gamma irradiation. In a second experiment, the authors examined the effects of gamma irradiation on the proclivity of hippocampal neurons to display epileptiform discharges. Naive animals were irradiated with a single 40-Gy dose, as already described. Slices of the hippocampus were prepared from animals killed between 1 and 178 days postirradiation. Sensitivity to penicillin-induced epileptiform spiking was examined in vitro in slices prepared from control and irradiated rat brains.

CONCLUSIONS

In the first experiment, single doses of 20 or 40 Gy (but not 10 Gy) reduced substantially, and in some cases eliminated, behaviorally and electrographically recognized seizures. Significant reductions in both the frequency and duration of spontaneous seizures were observed during a follow-up period of up to 10 months postradiation. Histological examination of the targeted region did not reveal signs of necrosis. These findings indicate that single-dose focal ionizing beam irradiation at subnecrotic dosages reduces or eliminates repetitive spontaneous seizures in a rat model of temporal lobe epilepsy. In the second experiment, synaptically driven neuronal firing was shown to be intact in hippocampal neurons subjected to 40-Gy doses. However, the susceptibility to penicillin-induced epileptiform activity was reduced in the brain slices of animals receiving 40-Gy doses, compared with those from control rats that were not irradiated. The results provide rational support for the utility of subnecrotic gamma irradiation as a therapeutic strategy for treating epilepsy. These findings also provide evidence that a functional increase in the seizure threshold of hippocampal neurons contributes to the anticonvulsant influence of subnecrotic gamma irradiation.

New developments in cerebrovascular surgery

Major changes in the treatment of various cerebrovascular disorders have occurred with improvement and maturation of endovascular techniques. Embolization of intracranial aneurysms, angioplasty and stenting of extracranial and intracranial stenosis, as well as local intra-arterial delivery of thrombolytic agents in patients with acute stroke, are therapeutic modalities that are now widely available, with encouraging preliminary results. Pooling and analysis of the immense amount of data generated by the major carotid endarterectomy trials are defining particular subgroups of patients with carotid stenosis who are at higher risk of stroke who might particularly benefit from the operation. Unfortunately, no significant improvements have occurred in the treatment of some other conditions, such as parenchymal arteriovenous malformations and intracerebral hemorrhage.

Subarachnoid haemorrhage: epidemiology, risk factors, and treatment options

The present review focuses on subarachnoid haemorrhage (SAH) secondary to the rupture of an intracranial aneurysm, a condition with a high case fatality rate. Additionally, many of the surviving patients are left with significant disabilities. Risk factors for aneurysmal SAH include both genetic and acquired conditions. The most common presenting symptom is sudden onset of severe headache. Since headache is very common in the general population, it is not unusual that SAH is misdiagnosed at its onset with often catastrophic consequences. Unlike other acute neurological disorders such as brain injury, in which patient outcome is closely related to the extent of the injury occurring at the time of the trauma, patients with aneurysmal SAH are at risk of subsequent deterioration from 'avoidable' complications such as rebleed, vasospasm, hydrocephalus, and several other non-neurological general medical complications. Thus, the critical care management of the patient with SAH is of utmost importance in order to maximise the chances of satisfactory recovery. Although surgical clipping of the ruptured aneurysm remains the gold standard therapy, with the continuing refinement of endovascular techniques, a new, 'less invasive' option is now available, especially for patients considered poor surgical candidates.

Delayed administration of the K+ channel activator cromakalim attenuates cerebral vasospasm after experimental subarachnoid hemorrhage

BACKGROUND

Delayed cerebral vasospasm remains an unpredictable and inadequately treated complication of aneurysmal subarachnoid hemorrhage (SAH). Recent evidence indicates that the potassium channel activator cromakalim is capable of limiting cerebral vasospasm in rabbits when administered immediately after experimental SAH (i.e. before spastic constriction has been initiated). However, the ultimate clinical value of cromakalim for treating vasospasm will depend in part on its effectiveness when administered after SAH-induced constriction has already been initiated. The present study examined the effects of cromakalim on vasospasm when treatment was initiated after SAH-induced constriction was underway.

METHODS

New Zealand white rabbits were subjected to experimental SAH by injecting autologous blood into the cisterna magna. Cromakalim (0.03, 0.1 or 0.3 mg/kg) or vehicle was injected intravenously at 8 hour intervals beginning 24 hours post-SAH. Animals were killed by perfusion fixation 48 hours after SAH. Basilar arteries were removed and sectioned, and cross-sectional area was measured.

FINDINGS

The average cross sectional areas of basilar arteries were reduced by 64% and 68% in the SAH-only and SAH + vehicle groups, respectively. Treatment with cromakalim dose-dependently attenuated SAH-induced constriction. The groups treated with 0.03, 0. 1, and 0.3 mg/kg cromakalim exhibited average decreases in cross-sectional area of 57%, 42%, and 19%, respectively.

INTERPRETATION

These findings indicate that cromakalim dose-dependently attenuates cerebral vasospasm when administered 24 hours after experimental SAH in the rabbit. The results suggest K(ATP) channel activators, such as cromakalim. could be of benefit for reversing cerebral vasospasm after aneurysmal SAH.

Induction of tolerance against ischemia/reperfusion injury in the rat brain by preconditioning with the endotoxin analog diphosphoryl lipid A

OBJECT

Inflammatory responses and oxygen free radicals have increasingly been implicated in the development of ischemic brain injury. In some cases, an attenuation of inflammation or free-radical injury can provide tissue protection. Diphosphoryl lipid A (DPL) is a detoxified derivative of a lipopolysaccharide (endotoxin) of Salmonella minnesota strain R595, which is capable of stimulating the immune system without eliciting direct toxic effects. In this study the authors examined the influence of preconditioning with DPL on ischemia/reperfusion injury in rats.

METHODS

Sprague-Dawley rats were injected intravenously with either DPL or vehicle. Twenty-four hours later, some animals were tested for superoxide dismutase (SOD) activity. Others were subjected to a 3-hour period of focal cerebral ischemia and, after a reperfusion period of 24 hours, were killed. Infarction volume, SOD activity, and myeloperoxidase (MPO) activity were assayed in the postischemic animals. Pretreatment with DPL produced significant reductions in cerebral infarction and MPO activity in the ischemic penumbra. A significant enhancement of basal SOD activity was observed 24 hours after DPL treatment (that is, before ischemia), and a further enhancement of SOD activity was seen in the ischemic penumbra 24 hours after reperfusion.

CONCLUSIONS

These data provide the first evidence of a neuroprotective effect of preconditioning with DPL in an in vivo model of cerebral ischemia. Although the precise mechanisms through which DPL exerts its neuroprotective influence remain to be established, an inhibition of the complex inflammatory response to ischemia and an enhancement of endogenous antioxidant activity are leading candidates.

Cerebral ischemia-reperfusion injury: a novel therapeutic approach with TAK-218

The goal of the present study was to evaluate the potential neuroprotective effect of TAK-218 in an in vivo rat focal cerebral ischemia/reperfusion model. TAK-218 is a novel compound with multiple antiischemic properties, including suppression of aberrant dopamine release, modulation of sodium channels, and inhibition of lipid peroxidation. The study was a blinded, randomized, placebo-controlled study of TAK-218 in a three-vessel focal ischemic rat model. A total of 22 rats were randomly assigned to the treatment or placebo group. Animals were injected intrapertoneally with either a 2 mg/kg dose of drug or saline at 2 hours after reperfusion. Infarction volume was measured with use of 2,3,5-triphenyltetrazolium chloride. Total adjusted infarction volume in treated animals decreased by 10%. With use of a statistical analysis requiring 80% power with a 20% reduction desired effect, there was no statistically significant difference in the end-point of infarction volume between drug and placebo treatment groups. In light of the proven efficacy of thrombolytic therapy for acute stroke, it is now desirable to test neuroprotective agents during the 3-hour therapeutic window after ischemia. Further research is necessary to discern if a therapeutic agent with multiple antiischemic properties may provide a more robust neuroprotective effect than an agent with a single neuroprotective action.

Efficacy of transluminal angioplasty for the management of symptomatic cerebral vasospasm following aneurysmal subarachnoid hemorrhage

OBJECT

Transluminal angioplasty has become a widely used adjunct therapy to medical management of symptomatic cerebral vasospasm following subarachnoid hemorrhage (SAH). Despite anecdotal reports of universal, angiographically confirmed reversal of vasospasm and high rates of clinical improvement, no rigorous examination of the efficacy of this procedure has been conducted. In this study the authors assess the efficacy of the aforementioned procedure.

METHODS

Thirty-eight patients enrolled as part of the North American trial of tirilazad in aneurysmal SAH underwent transluminal angioplasty for symptomatic cerebral vasospasm. Fifty-three percent of these patients showed good recovery or moderate disability based on their 3-month Glasgow Outcome Scale score. Among the 38 patients who underwent angioplasty, the severity and type of vasospasm, use of papaverine in addition to balloon angioplasty, timing of treatment, and dose of study drug did not have an effect on the outcome. The results of their neurological examinations improved in only four of the 38 patients immediately after the procedure. A conditional logistic regression analysis was performed in which these patients were compared with individuals matched for age, sex, dose of study drug, admission neurological grade, and modified Glasgow Coma Scale score at the time of angioplasty. No effect on favorable outcomes was found for this procedure.

CONCLUSIONS

Transluminal cerebral angioplasty is very effective in reversing angiographically confirmed vasospasm, and anecdotal reports of its clinical utility are numerous. However, in this report the authors conclude that its superiority to medical management for symptomatic cerebral vasospasm is questionable.

Factors associated with hydrocephalus after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Associations among various factors and the occurrence of hydrocephalus after aneurysmal subarachnoid hemorrhage (SAH) were evaluated retrospectively in 897 patients enrolled in the North American study of tirilazad mesylate.

METHODS

Patients were assessed for hydrocephalus in a blinded fashion. Assessment of hydrocephalus was made on the basis of 3-month follow-up computed tomographic studies or, for those without a 3-month follow-up scan, on the basis of the latest computed tomographic studies obtained at least 10 days after SAH. Criteria indicating the occurrence of hydrocephalus were the presence of significantly enlarged temporal horns or prior placement of a ventricular shunt. Univariate analysis was performed to assess relationships among various factors and hydrocephalus. Factors statistically associated with the occurrence of hydrocephalus were analyzed further using logistic regression analysis.

RESULTS

Overall, 25.9% of the 897 patients developed hydrocephalus. Statistically significant associations among the following factors and hydrocephalus were observed (P value; risk coefficient): 1) severity of 3-month post-SAH Glasgow Outcome Scale (0.0001; 2.00); 2) increased ventricular size at admission (0.0001; 2.78); 3) neurological grade severity at admission (0.0274; 1.26); 4) preexisting hypertension (0.0284; 1.66); 5) alcoholism (0.0066; 2.30); 6) female sex (0.0056; 0.49); 7) increased aneurysm size (0.0239; 0.56); 8) pneumonia (0.0299; 1.78); 9) meningitis (0.0290; 5.86); and 10) intraventricular hemorrhage at admission (0.0414; 1.64).

CONCLUSION

Hydrocephalus seems to have a multifactorial etiology. Knowledge of risk factors related to the occurrence of hydrocephalus may help guide neurosurgeons in the long-term care of patients who have experienced aneurysmal SAH.

Double-blind, randomized, vehicle-controlled study of high-dose tirilazad mesylate in women with aneurysmal subarachnoid hemorrhage. Part I. A cooperative study in Europe, Australia, New Zealand, and South Africa

OBJECT

Findings from previous multicenter clinical trials have suggested that tirilazad mesylate, a synthetic nonhormonal 21-aminosteroid, might be effective in preventing delayed cerebral ischemia following subarachnoid hemorrhage (SAH). This beneficial effect, however, was greater in males than females, possibly because of gender-related pharmacokinetic differences. The authors sought to assess the effects of administering a larger dose of tirilazad in women with SAH.

METHODS

To test the efficacy of a higher tirilazad mesylate dose in female patients, a prospective randomized, double-blind, vehicle-controlled trial was conducted at 56 neurosurgical centers in Europe, Australia, New Zealand, and South Africa. Eight hundred nineteen patients were randomly assigned to receive either 15 mg/kg/day of tirilazad mesylate or a placebo containing the citrate vehicle. The two groups were similar in prognostic factors for delayed cerebral ischemia and overall outcome. High-dose tirilazad appeared to be well tolerated because no differences in the incidence of untoward medical events were noted between the two groups. Medical and surgical interventions were no different in the two treatment groups except for hyperdynamic therapy (intentional hypervolemia, induced hypertension, and/or hemodilution), which was more often used in the placebo-treated group to counteract symptomatic vasospasm (24% of patients given placebo compared with 18% of patients given tirilazad, p = 0.02). Mortality rates and overall outcome, assessed using the Glasgow Outcome Scale at 3 months post-SAH, were not different between the two groups, despite a significantly lower incidence of delayed cerebral ischemia in patients given tirilazad. Post hoc subgroup analysis by neurological grade also did not reveal significant differences in outcome, although a trend toward a lower mortality rate favoring the study drug was present in patients with neurological Grade IV and V at admission (32% compared with 37%). Symptomatic vasospasm occurred in 33.7% of the placebo-treated patients as opposed to 24.8% of the patients who were given tirilazad (p = 0.005). The severity of symptomatic vasospasm was also attenuated by administration of the study drug (severe symptomatic vasospasm was reported in 11% of the placebo-treated patients compared with 6% of patients in the tirilazad-treated group (p = 0.008). Clinical cerebral infarction from vasospasm was also reduced from 13% in the vehicle-treated group to 8% in the tirilazad-treated group (p < 0.04).

CONCLUSIONS

The authors conclude that high-dose tirilazad mesylate is well tolerated in women with aneurysmal SAH. Although a significant reduction in the incidence of symptomatic vasospasm was observed in the treatment group, the primary end point (mortality rate at 3 months post-SAH) was not affected by the study drug. The use of other potentially effective rescue therapies (that is, hypervolemia, hemodilution, and induced hypertension) to counteract vasospasm may have been responsible for these contrasting observations between the two groups.

Double-blind, randomized, vehicle-controlled study of high-dose tirilazad mesylate in women with aneurysmal subarachnoid hemorrhage. Part II. A cooperative study in North America

OBJECT

To test the safety and efficacy of high-dose (15 mg/kg/day) tirilazad mesylate in women suffering from aneurysmal subarachnoid hemorrhage (SAH), a prospective randomized, double-blind, vehicle-controlled trial (parallel to the one conducted in Europe, Australia, New Zealand, and South Africa) was performed at 65 North American neurosurgical centers.

METHODS

Of the 832 patients who were randomized, 823 received at least one dose of tirilazad (410 patients) or placebo vehicle containing citrate (413 patients). The two groups were similar with respect to their prognostic factors for overall outcome and delayed cerebral ischemia. There were no differences in medical and surgical interventions including hyperdynamic therapy (intentional hypervolemia, induced hypertension, and/or hemodilution) between the two treatment groups. In contrast to the accompanying study, the protocol for the North American study was formally amended, in that a sequential analysis of the primary efficacy end point, mortality rate at 91 days postdosing, was performed. This analysis revealed a statistically significant difference in mortality rates, favoring the study drug, among patients who were neurological Grade IV or V at admission (24.6% compared with 43.4% in the placebo-treated group, p = 0.016). No significant differences, however. were found when the entire patient population was considered (15.6% in the placebo-treated group and 13% in the tirilazad-treated group). Other major and secondary end points, which included rate of favorable outcome (74% in the placebo-treated group and 71% in the tirilazad-treated group); symptomatic vasospasm (38% in the placebo-treated group and 35% in the tirilazad-treated group); and vasospasm severity (severe symptomatic vasospasm in 14% of patients in both groups), were also not significantly different between the two groups. In patients with neurological Grades I through III, rates of favorable outcome advantageous to the vehicle-treated group were observed (83.3% compared with 76.7%, p = 0.04).

CONCLUSIONS

High-dose tirilazad mesylate is well tolerated in women with aneurysmal SAH. Sequential analysis revealed a significant reduction in mortality rates among patients with neurological Grades IV and V, favoring the study drug and confirming the same effect observed in male patients in previous large studies. No beneficial effect was observed in patients who were in a good neurological grade at admission.

Posterior inferior cerebellar artery aneurysms associated with posterior fossa arteriovenous malformation: report of five cases and literature review

BACKGROUND

The association of posterior inferior cerebellar artery (PICA) aneurysms with posterior fossa arteriovenous malformation (AVM) is uncommon. Over the past 3 years, five patients with this condition were treated at this institution. A review of the clinical history of these and other reported cases has illuminated common threads in the presentation, treatment, and outcome of these lesions.

METHODS

The findings of 27 patients (5 from our institution and 22 from the medical literature) with PICA aneurysms associated with AVMs were reviewed.

RESULTS

Eighty-four percent of individuals presented with sub-arachnoid hemorrhage (SAH); 89% of these episodes resulted from aneurysm rupture documented by either intraoperative inspection or autopsy. All aneurysms were located on a feeding artery to the AVM, and 81% originated from distal portions of PICA. The majority of patients presented with Hunt & Hess grade I SAH; all patients who presented with hemorrhage were treated surgically. Surgical strategy was directed both to secure the aneurysm and to resect the AVM during the course of a single procedure. Although four individuals either died on admission or in the perioperative period, overall outcome was excellent or good in 82% of patients.

CONCLUSIONS

PICA aneurysms associated with AVMs most often involve the distal segments of the artery. Patients usually present with SAH secondary to aneurysmal rupture. Surgical clipping of the aneurysm and excision of the AVM is possible in a single procedure with minimal morbidity. Overall prognosis is favorable in 80% of the cases.