CSF smooth-muscle constrictor activity associated with cerebral vasospasm and mortality in SAH patients

Subarachnoid Hemorrhage Depletes Calcitonin Gene-Related Peptide Levels of Trigeminal Neurons in Rat Dura Mater

Subarachnoid hemorrhage (SAH) remains a major cause of cerebrovascular morbidity, eliciting severe headaches and vasospasms that have been shown to inversely correlate with vasodilator calcitonin gene-related peptide (CGRP) levels. Although dura mater trigeminal afferents are an important source of intracranial CGRP, little is known about the effects of SAH on these neurons in preclinical models. The present study evaluated changes in CGRP levels and expression in trigeminal primary afferents innervating the dura mater 72 h after experimentally induced SAH in adult rats. SAH, eliciting marked damage revealed by neurological examination, significantly reduced the density of CGRP-immunoreactive nerve fibers both in the dura mater and the trigeminal caudal nucleus in the medulla but did not affect the total dural nerve fiber density. SAH attenuated ex vivo dural CGRP release by ~40% and in the trigeminal ganglion, reduced both CGRP mRNA levels and the number of highly CGRP-immunoreactive cell bodies. In summary, we provide novel complementary evidence that SAH negatively affects the integrity of the CGRP-expressing rat trigeminal neurons. Reduced CGRP levels suggest likely impaired meningeal neurovascular functions contributing to SAH complications. Further studies are to be performed to reveal the importance of impaired CGRP synthesis and its consequences in central sensory processing.

Management of non-vestibular schwannomas in adult patients: a systematic review and consensus statement on behalf of the EANS skull base section Part III: Lower cranial nerve schwannomas, jugular foramen (CN IX, X, XI) and hypoglossal schwannoma (XII)

BACKGROUND

Non-vestibular schwannomas are relatively rare, with trigeminal and jugular foramen schwannomas being the most common. This is a heterogenous group which requires detailed investigation and careful consideration to management strategy. The optimal management for these tumours remains unclear, and there are several controversies. The aim of this paper is to provide insight into the main principles defining management and surgical strategy, in order to formulate a series of recommendations.

METHODS

A task force was created by the EANS skull base section committee along with its members and other renowned experts in the field to generate recommendations for the surgical management of these tumours on a European perspective. To achieve this, the task force performed an extensive systematic review in this field and had discussions within the group. This article is the third of a three-part series describing non-vestibular schwannomas (IX, X, XI, XII).

RESULTS

A summary of literature evidence was proposed after discussion within the EANS skull base section. The constituted task force dealt with the practice patterns that exist with respect to preoperative radiological investigations, ophthalmological assessments, optimal surgical and radiotherapy strategies and follow-up management.

CONCLUSION

This article represents the consensually derived opinion of the task force with respect to the treatment of non-vestibular schwannomas. For each of these tumours, the management paradigm is shifting towards the compromise between function preservation and progression free survival.

Bilirubin oxidation products (BOXes) and their role in cerebral vasospasm after subarachnoid hemorrhage

Many factors have been postulated to cause delayed subarachnoid hemorrhage (SAH)-induced vasospasm, including hemoglobin, nitric oxide, endothelin, and free radicals. We propose that free radicals (because of the high levels that are produced in the blood clots surrounding blood vessels after SAH) act on bilirubin, biliverdin, and possibly heme to produce BOXes (Bilirubin OXidized Products). Bilirubin oxidation products act on vascular smooth muscle cells to produce chronic vasoconstriction and vasospasm combined with a vasculopathy because of smooth muscle cell injury. This review summarizes recent evidence that BOXes play a role in SAH-induced vasospasm. The data supporting a role for BOXes includes (1) identification of molecules in cerebrospinal fluid (CSF) of patients with vasospasm after SAH that have structures consistent with BOXes; (2) BOXes are vasoactive in vitro and mimic the biochemical actions of CSF of patients with vasospasm; (3) BOXes are vasoactive in vivo, constricting rat cerebral vessels; and (4) there is a correlation between clinical occurrence of vasospasm and BOXes concentration in our preliminary study of patients with SAH. Since oxidation of bilirubin, biliverdin, and perhaps heme is proposed to produce BOXes that contribute to vasospasm, either blocking bilirubin formation, inactivating bilirubin or BOXes, or removing all of the blood clot before vasospasm are potential treatment targets.

Inhibitory effects of verapamil and nitroglycerin on contraction and cytosolic Ca2+ levels in cerebrovascular smooth muscle during chronic cerebral vasospasm

The mechanisms of the inhibitory effects of verapamil and nitroglycerin on vasospasm were investigated by measuring cytosolic Ca2+ level ([Ca2+]i) and muscle tension in 28 normal specimens and 28 spastic vascular specimens of smooth muscle. Experimental vasospasm was produced by the two-hemorrhage method in the canine basilar artery. [Ca2+]i and tension were recorded simultaneously with a fluorimeter using fura-2. High K+ concentration (72.4 mM) and U-46619 (thromboxane A2 analogue, 10(-8) M) were used as stimulants, and the inhibitory effects of verapamil or nitroglycerin on muscle contraction and increased [Ca2+]i were examined. Verapamil inhibited [Ca2+]i and contraction in high K+ concentration-stimulated arteries. Verapamil inhibited [Ca2+]i more strongly than contraction in U-46619-stimulated arteries. There were no significant differences in the effects of verapamil in the control and vasospasm groups. Nitroglycerin inhibited contraction with little effect on [Ca2+]i in high K+ concentration-stimulated arteries in both the control and vasospasm groups. Nitroglycerin inhibited contraction with little effect on [Ca2+]i in U-46619-stimulated arteries and the inhibitory effect was weaker in the vasospasm group than in the control group. The inhibitory effects of verapamil on muscle tension and [Ca2+]i in vasospastic vessels were as strong as those in normal vessels. In contrast, the inhibitory effects of nitroglycerin were reduced in vasospastic vessels. Increased Ca2+ sensitivity in vasospastic vessels may have reduced the inhibitory effects of nitroglycerin.

Role of adenosine 5'-triphosphate in vasospasm after subarachnoid hemorrhage: human investigations

OBJECTIVE

Adenosine 5'-triphosphate (ATP) is a vasoactive compound found in high concentrations inside erythrocytes. This compound may contribute to vasospasm after subarachnoid hemorrhage (SAH). We assessed the hypothesis that ATP contributes to vasospasm in humans.

METHODS

ATP and hemoglobin concentrations were measured in cerebrospinal fluid (CSF) from humans with SAH and in blood incubated in vitro. The vasoactivity of the human CSF samples and of fractionated (fractions with molecular weight greater than or less than 10 kDa) and unfractionated blood incubated in vitro was assessed by application of samples to canine basilar artery segments under isometric tension.

RESULTS

ATP in human CSF declined within 72 hours of SAH to concentrations too low to contract cerebral arteries. Vasoactivity of human CSF correlated with the concentration of hemoglobin. The vasoactivity of incubated erythrocyte hemolysates remained high despite a decline in ATP concentrations. Fractionation of incubated erythrocyte hemolysates showed that for incubation periods up to 7 days, all vasoactivity was in a fraction of molecular weight greater than 10 kDa.

CONCLUSION

ATP is unlikely to contribute to vasospasm because the concentrations in CSF after SAH in humans are not high enough to cause vasospasm after 72 hours. The vasoactivity of erythrocyte hemolysate is not related to the ATP or ferrous hemoglobin content but may be related to the total hemoglobin content. Therefore, ATP is unlikely to be a major cause of clinically significant delayed vasospasm.

Calcium channels in cerebral arteries

Electrophysiological evidence shows the existence of voltage-operated Ca2+ channels of the L- and, in some cases, T- and B-, type in the smooth muscle cells of major cerebral arteries and arterioles. Current intensity through L-type Ca2+ channels is higher in cerebral than in peripheral arteries, which points to a greater dependence on extracellular Ca2+ of contractile responses in cerebral arteries. The increase in cytosolic Ca2+ concentration is the key event leading both to maintenance of basal cerebrovascular tone and to contraction of cerebral arteries in response to depolarization and agonist-receptor interaction. Such an increase results from increased transmembrane influx of Ca2+ through L-type Ca2+ channels, as well as from the release of Ca2+ from intracellular Ca2+ stores. Ca2+ entry modulators (dihydropyridines, phenylalkylamines, benzothiazepines, and diphenylpiperazines) bind to allosterically coupled sites in the Ca2+ channel, thus inhibiting (Ca2+ entry blockers) or stimulating (Ca2+ entry activators) Ca2+ influx and, therefore, contractile responses of the cerebral arteries. In vivo, Ca2+ entry blockers increase pial vascular caliber and cerebral blood flow by their direct action on the cerebroarterial wall. However, such an action also takes place on several peripheral vascular beds, which leads to hypotension. Therefore, the brain cannot be considered a "privileged" organ when the vasodilatatory action of Ca2+ entry blockers is considered. Since increased cytosolic Ca2+ concentration (and, therefore, activation of Ca2+ channels) plays a crucial role in the pathogenesis of ischemic brain damage (e.g., acute stroke and subarachnoid hemorrhage), Ca2+ entry blockers could be useful cytoprotective drugs. However, with the exception of nimodipine in the management of subarachnoid hemorrhage, clinical trials have yielded results that are not so promising as one could expect from those obtained in experimental research.

Role of prostaglandins in delayed cerebral ischemia after subarachnoid hemorrhage

Prostaglandin E2, thromboxane B2, and 6-oxo-prostaglandin F1 alpha were assayed in blood and cerebrospinal fluid samples from patients after subarachnoid hemorrhage (SAH) and from a control population. The levels found in samples obtained from patients after SAH were compared with those found in controls and were also correlated with a number of clinical and radiological variables, many of which are either significantly associated with or represent evidence of cerebral ischemia. The levels of prostaglandin E2, thromboxane B2, and 6-oxo-prostaglandin F1 alpha in blood samples from patients after SAH and from controls were below the level of sensitivity of the assays. Levels of prostaglandin E2, thromboxane B2, and 6-oxo-prostaglandin F1 alpha in cerebrospinal fluid from patients after SAH were significantly elevated when compared with those found in control samples. There was no significant correlation, however, between the level of each prostaglandin measured and the following variables: clinical grade on admission as assessed by the Glasgow Coma Score and the World Federation of Neurological Surgeons grading system; the amount of subarachnoid blood seen on computed tomographic scan; the occurrence of ischemic deterioration; the occurrence of low density change on computed tomographic scan; the presence of vasospasm on angiography; clinical outcome as assessed by the Glasgow Coma Score 3 months after the ictus; and the incidence of ischemia as a cause of death or disability as assessed 3 months after the ictus. A primary role for prostaglandins in the etiology of delayed cerebral ischemia after SAH is not therefore confirmed.

A review of hemoglobin and the pathogenesis of cerebral vasospasm

We believe that current experimental and clinical evidence can be most satisfactorily interpreted by assuming that oxyhemoglobin is the cause of cerebral vasospasm that follows subarachnoid hemorrhage. We review the pathogenetic mechanisms by which oxyhemoglobin affects cerebral arteries. The relative importance of each of these mechanisms in the genesis of vasospasm, the biochemical pathways of oxyhemoglobin-induced smooth muscle contraction, and the intracellular actions of oxyhemoglobin on smooth muscle and on other cells in arteries are still not definitely established.

Alterations in serotonin and neuropeptide Y content of cerebrovascular sympathetic nerves following experimental subarachnoid hemorrhage

The effect of an experimental subarachnoid hemorrhage (SAH) upon neurotransmitter content in sympathetic nerves supplying the major cerebral arteries of the rat has been examined by immunohistochemical analysis and high performance liquid chromatography with electrochemical detection (HPLC-ECD). In particular, changes that occur in sympathetic nerve content of the vasoconstrictor agents serotonin (5-HT) and neuropeptide Y (NPY), which are colocalized with noradrenaline, were assessed. Subarachnoid hemorrhage was induced by a single injection of autologous arterial blood into the cerebrospinal fluid (CSF) space of the cisterna magna. The density of 5-HT-containing and NPY-containing perivascular nerve fibers per unit area of vessels was measured at defined intervals from 15 min to 5 days post-SAH. In addition, an HPLC study was performed to quantify the actual amounts of 5-HT and noradrenaline present in circle of Willis vessels at 3 h post-SAH. Comparison was made with sham-operated animals and animals that received a cisternal injection of buffered saline in place of blood. Our results reveal a major increase in cerebrovascular sympathetic nerve content of serotonin, arising by uptake, presumably from subarachnoid blood clot, within the first 3 h post-SAH. Neuropeptide Y content, however, decreased from 3 up to 48 h posthemorrhage. By 3 days post-SAH, when the majority of subarachnoid clot had resorbed, the sympathetic nerve content of both NPY and 5-HT was restored to normal. This pattern of change was not observed in either sham-operated or saline-injected controls.

Cisternal and lumbar CSF levels of arachidonate metabolites after subarachnoid haemorrhage: an assessment of the biochemical hypothesis of vasospasm

Several naturally occurring compounds have been identified in human cerebrospinal fluid (CSF) after subarachnoid haemorrhage (SAH) as possible vasoactive agents involved in the biochemical mechanism of vasospasm. The authors have measured, in 30 patients admitted for SAH, CSF concentrations of two arachidonic acid metabolites. Prostacyclin and Prostaglandin D2, as representative of vasodilator and vasoconstrictor compounds. CSF samples were made available by lumbar punctures and intraoperative cisternal punctures. Nine patients presented with symptomatic vasospasm: lumbar CSF Prostaglandin D2 levels are significantly higher than in patients without vasospasm. The Cisternal Prostaglandin D2 level is significantly higher than the lumbar CSF concentration; CSF Prostacyclin levels do not significantly differ in the two groups of patients. These data suggest the presence of an imbalanced biochemical situation responsible for promoting vasospasm. The evaluation of cisternal levels of arachidonate metabolites support the hypothesis of the clotting phenomenon around the ruptured aneurysm wall as an important predictive pattern of vasospasm onset after SAH, as shown in computed tomography.

The effect of intravenous lidoflazine on whole blood-induced basilar artery contraction. An in vivo study

Lidoflazine, a piperazine derivative of known selectivity for vascular smooth muscle, was evaluated as a possible agent for prophylaxis of cerebral vascular contraction induced by subarachnoid perfusion with whole blood. Previous studies from this laboratory have indicated its efficacy in preventing basilar artery contraction induced by serotonin. The animals treated with a subarachnoid perfusion of whole blood had a mean 30% reduction in vessel diameter over the control value. Groups that were treated with 0.5 mg/kg of lidoflazine and 1.0 mg/kg of lidoflazine and then perfused with whole blood in the subarachnoid space had reductions in control diameter of 2.8% and 6.8%, respectively. One group treated with 2.0 mg/kg of lidoflazine and then perfused with whole blood actually had an increase in diameter of 6.8% over the control value. Lidoflazine, when administered intravenously at a slow rate, will not adversely lower systemic blood pressure and can prevent the contraction of cerebral vessels when the stimulus for contraction is whole blood within the subarachnoid space.

Evaluation of the role hemoglobin in cerebrospinal fluid plays in producing contractions of cerebral arteries

Many investigators have concluded that hemoglobin is the spasmogen responsible for cerebral vasospasm. The present study was designed to ascertain whether the contractile responses of isolated canine basilar arteries to xanthochromic cerebrospinal fluid from subarachnoid hemorrhage patients was associated with hemoglobin concentration as measured spectrophotometrically. The results clearly showed that spasmogenicity and hemoglobin content were not correlated. The magnitude and duration of the arterial responses varied greatly, further indicating that more than a single factor was responsible. The potent antagonistic, vasodilator effect of such proteins as antithrombin III may account for some of the variation, but the results directly complement clinical findings of others indicating that hemoglobin is not the singular cause of cerebral vasospasm.

Functional arterial changes in chronic cerebrovasospasm in monkeys: an in vitro assessment of the contribution to arterial narrowing

Cerebral arteries from monkeys with chronic cerebral vasospasm arising from experimental subarachnoid hemorrhage produced 5-6 days previously were examined for changes in their functional properties in an attempt to understand the basis of the narrowing. Hemorrhage was caused by puncture of the internal carotid artery just proximal to the circle of Willis. Segments taken close to the origins of the anterior and middle cerebral arteries consistently showed decreased distensibility. In addition, they exhibited large, prolonged, spontaneous increases in muscle tone. Other alterations observed include a marked reduction in the capacity of the vessel wall to contract, reduction in constrictor and dilator nerve influences on vascular tone, and some increased sensitivity to serotonin. Small pial arteries (150-200 micron o.d.) from the side of the injury showed large spontaneous irregular increases in tone. It is proposed that 5-6 days after experimental subarachnoid hemorrhage in monkeys the change most responsible for persistent narrowing in the larger arteries is an increased rigidity of the vessel wall. This is probably caused by an inflammatory response. In the smaller arteries, abnormal spontaneous contractile activity is a major factor in narrowing. This activity is not stretch-dependent. We suggest that the initial cause of the arterial narrowing after hemorrhage is the action of vasoactive substances released in the close vicinity of the arterial wall, which lead to tissue damage, abnormal tone, and an inflammatory response with fibrosis.

The effect of intravenous lidoflazine on serotonin-induced cerebral vascular contraction--an in vivo study

Lidoflazine, a piperazine derivative with known selectivity for vascular smooth muscle, was evaluated as a possible agent for prophylaxis of cerebral vascular contraction induced by subarachnoid perfusion with serotonin. The animals treated with serotonin (5 X 10(-6) M), had a 60% reduction in the diameter of basilar artery but when pretreated with Lidoflazine (1 mg/kg) intravenously, only had a 20% reduction in diameter (p less than 0.01). Lidoflazine, when administered intravenously at a slow rate will not adversely lower systemic blood pressure and can prevent the contraction of cerebral vessels when the stimulus for contraction is in the subarachnoid space.

Prostaglandin D2 monitoring in human CSF after subarachnoid hemorrhage: the possible role of prostaglandin D2 in the genesis of cerebral vasospasm

Experimental and clinical studies indicate that cerebral vasospasm following subarachnoid hemorrhage (SAH) may be caused by changed biochemical properties of the endothelium and vascular smooth muscle cell exposed to vasoactive substances synthetized by cerebral arteries and released in clotted blood. Many compounds have been identified in CSF from SAH patients: Thromboxanes A2 and B2, Prostaglandins F2 alpha, E2 and D2 are the major prostanoids incriminated in the causation of cerebral arterial spasm. We have monitored the CSF PGD2 concentrations with serial lumbar punctures at different intervals from the hemorrhage in 16 patients admitted for SAH: PGD2 was measured with radioimmunoassay as its 9-methoxy derivative. The lumbar CSF PGD2 concentration ranges from 0.11 to 1.53 ng/ml. In 7 cases vasospasm was angiographically demonstrated. 9 patients presented no clinical or radiological evidence of vasospasm. In 5 cases cisternal CSF samples were available at the operation by cisternal punctures. There was no correlation between CSF PGD2 concentration and clinical course. In the 7 cases with evidence of vasospasm a significant increase of CSF PGD2 corresponded to neurological deterioration. In all 9 cases without evidence of vasospasm CSF PGD2 concentration trend was in a steady-state. The cisternal CSF PGD2 concentration was higher than lumbar CSF concentration in cases with arterial spasm. This suggests the importance of the clotting phenomenon in vasospasm onset after SAH. PGD2 is one of the most important spasmogens in clotted blood. Although its role in the genesis of vasospasm onset remains to be defined, its vasospastic action, in addition to that of other analogous compounds, seems to be relevant.

Prostacyclin and vasospasm in subarachnoid hemorrhage from ruptured intracranial aneurysm. A preliminary clinical study

Experimental and clinical observations suggest the importance of arachidonate metabolites in the genesis of symptomatic cerebral vasospasm after subarachnoid hemorrhage. Prostacyclin (PG12) has a well demonstrated vasodilator action. The authors monitored CSF prostacyclin concentration in 12 consecutive cases of subarachnoid hemorrhage with the purpose of correlating the prostacyclin concentration trend with the clinical course and the risk for vasospasm. In three cases patients presented with clinical and radiological signs of vasospasm. CSF prostacyclin concentration showed a typical decreasing trend, which amounted to a minor form of protection from vasospastic agents. The nine cases which did not develop vasospasm demonstrated no significant changes in the prostacyclin CSF concentration trend. The authors also presented four cases in which cisternal CSF samples were available. In one case of developing vasospasm, the cisternal prostacyclin concentration was seven times lower than the highest lumbar CSF concentration. In three cases without evidence of vasospasm cisternal CSF demonstrated a balanced biochemical situation and a minor risk of vasospasm.

Cisternal and lumbar CSF concentration of arachidonate metabolites in vasospasm following subarachnoid hemorrhage from ruptured aneurysm: biochemical and clinical considerations

Two representative cases of subarachnoid hemorrhage in which prostaglandin D2 (PGD2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), stable metabolite of prostacyclin (PGI2), were monitored with serial lumbar punctures and detected in cisternal CSF during operations for aneurysm, are reported. In the case with demonstrated arterial vasospasm, prostaglandin D2 has a concentration trend with characteristic peak related to vasospasm; the synthesis of prostacyclin appears inhibited after the hemorrhage. In the patient without radiologic evidence of vasospasm, arachidonate metabolite concentration trend appears in a steady-state. Cisternal prostaglandin D2 concentration in the patient with demonstrated vasospasm is two times the highest lumbar CSF concentration, while 6-keto-prostaglandin F1 alpha concentration is very low. This suggests the role of the clotting phenomenon and likely confirms the importance of arachidonate metabolites in the genesis of cerebral arterial spasm following subarachnoid hemorrhage.