Molecular biological considerations in cerebral vasospasm following aneurysmal subarachnoid hemorrhage

Endothelial nitric oxide synthase tagging single nucleotide polymorphisms and recovery from aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a hemorrhagic stroke subtype with a poor recovery profile. Cerebral vasospasm (CV), a narrowing of the cerebral vasculature, significantly contributes to the poor recovery profile. Variation in the endothelial nitric oxide (NO) synthase (eNOS) gene has been implicated in CV and outcome after SAH. The purpose of this project was to explore the potential association between three eNOS tagging single nucleotide polymorphisms (SNPs) and recovery from SAH. We included 195 participants with a diagnosis of SAH and DNA and 6-month outcome data available but without preexisting neurologic disease/deficit. Genotyping was performed using an ABI Prism 7000 Sequence Detection System and TaqMan assays. CV was verified by cerebral angiogram independently read by a neurosurgeon on 118 participants. Modified Rankin Scores (MRS) and Glasgow Outcome Scale (GOS) scores were collected 6 months posthemorrhage. Data were analyzed using descriptive statistics, analysis of variance (ANOVA) and chi-square analysis as appropriate. The sample was primarily female (n=147; 75.4%) and White (n=178; 91.3%) with a mean age of 54.6 years. Of the participants with CV data, 56 (47.5%) developed CV within 14 days of SAH. None of the SNPs individually were associated with CV presence; however, a combination of the three variant SNPs was significantly associated with CV (p=.017). Only one SNP (rs1799983, variant allele) was associated with worse 6-month GOS scores (p<.001) and MRS (p<.001). These data indicate that the eNOS gene plays a role in the response to SAH, which may be explained by an influence on CV.

The role of nitric oxide in resolution of vasospasam corresponding with cerebral vasospasms after subarachnoid haemorrhage: animal model

Intracranial aneurysmal rupture is the common cause of spontaneous subarachnoid haemorrhage (SAH). This haemorrhage is typically diffuse and located in extracerebral subarachnoid space in which main cerebral arterial branches are situated. The intimate and long-term contact of arterial wall and blood products in the closed space causes the cerebral vasospasm as a serious and frequent complication of SAH. It is connected with significant morbidity and mortality due to developing of focal cerebral ischaemia and subsequently cerebral infarction. The aim of our experimental research was to create the animal model of vasospasm using the femoral artery due to examination of reduced basic dilator activity cause in arterial wall after SAH. The important characteristic of major cerebral arteries is their localization in the closed subarachnoid space which enables their to have long-term contact with blood products after haemorrhage. Thirty six femoral arteries (FA) of eighteen female rats weighing about 300 g were used. In vivo, femoral arteries are microsurgically prepared in both inguinal regions in all rats. Eighteen arteries were encompassed by polytetrafluoroethylene (PTFE) material forming closed tube and autologous blood was injected in the tube around the arterial wall. Additional eighteen arteries, as a control group, were also put in PTFE tube but without exposing to the blood. All rats are left to live for eight days. Afterwards, rats were sacrificed and their arteries were in vitro examined including an isometric tension measurement and histological changes analysis. The tension was measured during application of vasoconstrictors and vasodilatators (nitric oxide, NO). FA exposed to periadventitial blood exhibit hyper reactivity to constrictors (KCl, phenylephrine, acetylcholine) compared to control group. It was also found that NO donor (sodium nitroprusside) diminished arterial spasm induced by blood and vasoconstrictors. In conclusion, FA can be used as a model for vasospasm correlating with cerebral vasospasm after SAH and therefore this model can be utilized in future experiments assessing cerebral vasospasm. The reduced basic dilator activity of spastic femoral artery is caused by an absence of gaseous messenger NO next to the arteries but not by diminished response vasculature to NO. Absence of NO after SAH probably causes the reduced basic dilator activity of cerebral arteries as well. The guanylate-cyclase level in the arterial wall is consequently reduced after SAH primary due to absence of NO but not due to direct reduction of enzyme activities caused by process of blood degradation inside of subarachnoid space.

Safety of intrathecal sodium nitroprusside for the treatment and prevention of refractory cerebral vasospasm and ischemia in humans

BACKGROUND AND PURPOSE

The delayed type of cerebral vasoconstriction known as cerebral vasospasm (DCV) remains an important cause of permanent neurological injury and death following aneurysmal subarachnoid hemorrhage despite best current medical therapy. The mechanism of DCV remains unknown. A new treatment for refractory DCV using intrathecally delivered sodium nitroprusside and results in 21 patients is reported.

METHODS

Candidates for treatment were patients with secured cerebral aneurysms presenting with clinical or radiographic SAH of grade 3 or higher. Patients with and without established DCV were treated. In 57% (12/21 patients) the diagnosis of severe DCV refractory to conventional treatment (HHH therapy and nimodipine) was established before treatment. Ten patients received ITSNP prophylactically. All patients with established DCV were in grave neurological condition before treatment. Procedures for vasospasm reversal were performed under simultaneous angiographic control with extensive hemodynamic and neurophysiologic monitoring. ITSNP was delivered by intraventricular or subdural catheter or by direct intraoperative suffusion. End points of intervention for established DCV were (1) durable angiographic reversal of vasoconstriction, (2) failure to effect reversal within 30 minutes, and (3) adverse effect. End points for DCV prevention were (1) post-SAH day 10 without evidence of vasoconstriction and (2) adverse effect. Cerebral angioplasty was used concomitantly in 9 treatments. The total number of treatments recorded was 171.

RESULTS

The overall neurological outcome was good or excellent in 76% of patients (16/21) overall and in 88.9% of patients (16/18) having at least a 1-month follow-up. Of the 5 patients with less-than-good outcome, 4 had presented initially with severe neurological injury (clinical SAH grade 4). Angiography demonstrated reversal or amelioration of vasoconstriction in 83% (5/6 cases) of established DCV treated by ITSNP alone. Among patients treated prophylactically, none developed clinical DCV.

CONCLUSIONS

These results suggest that ITSNP is a safe and potentially effective treatment for established DCV and cerebral ischemia refractory to conventional treatment. The preliminary results of prophylactic treatment are also favorable with regard to safety.

Reversal of severe cerebral vasospasm in three patients after aneurysmal subarachnoid hemorrhage: initial observations regarding the use of intraventricular sodium nitroprusside in humans

OBJECTIVE AND IMPORTANCE

The chronic delayed type of cerebral vasoconstriction that occurs after aneurysmal subarachnoid hemorrhage (SAH) is now the most important cause of mortality and neurological morbidity for patients who initially survive the rupture of cerebral aneurysms. Although intravascular volume expansion and cardiac performance enhancement have had a profound impact on the treatment of the chronic delayed type of cerebral vasoconstriction, this form of treatment is not tolerated by all patients and is unhelpful in some. A more specific and more reliable treatment for this condition has not been previously reported. Previous work in an animal model has demonstrated the efficacy of nitric oxide-donating compounds in reversing severe cerebral vasoconstriction when delivered to the adventitial side of the blood vessel. A clinical study was initiated after receiving approval from the United States Food and Drug Administration and the institutional review board.

CLINICAL PRESENTATION

Three cases of prompt and substantial reversal of medically refractory vasospasm occurring after aneurysmal SAH in humans using an intrathecally administered nitric oxide donor and clinical, angiographic, and ultrasonographic documentation are presented. All patients developed severe vasospasm refractory to medical treatment 5 to 12 days after sustaining aneurysmal SAH. All patients manifested stupor of new onset (Glasgow Coma Scale score of 7) and new focal neurological deficit (hemiplegia). The condition was angiographically demonstrated in all cases.

INTERVENTION

The patients were treated with intrathecally administered sodium nitroprusside, which caused the reversal of vasospasm, which was documented by angiography and transcranial Doppler ultrasonography up to 54 hours later and also by dramatic clinical improvement. Complications related to intracranial pressure elevation, changes in vital signs, and hemodynamic parameters were not observed during or after the procedures. Radiographic evidence of the reversal of vasospasm and brain ischemia was obtained. The clinical outcomes of the treated patients were excellent. All patients presented with hemiplegia and stupor that resolved or markedly improved (within several days, two patients; within 12 hours, one patient). All three patients were discharged and were living at home at the time of manuscript submission.

CONCLUSION

These preliminary observations suggest that sodium nitroprusside delivered by an intrathecal route of administration may be a useful treatment for severe vasospasm complicating SAH in humans.