Experimental cerebral vasospasm after subarachnoid hemorrhage: development and degree of vasospasm

Brain Magnetic Resonance Imaging for Traumatic Brain Injury: Why, When, and How?

Conventional magnetic resonance imaging (MRI) and angiography (MRA) provide invaluable information in the evaluation of patients with all stages and grades of traumatic brain injury (TBI). The information obtained with MRI provides a more complete assessment of the patient's brain injury and possible long-term sequelae.

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.

Lactate Contents From Cerebrospinal Fluid in Experimental Subarachnoid Hemorrhage, Well Correlate With Vasospasm

The role of lactate composition of cerebrospinal fluid (CSF) with vasospasm severity and rabbit neurologic status in subarachnoid hemorrhage was determined. The neurologic status of 20 New Zealand rabbits were graded initially and then, anesthetized and basal angiograms were performed. Then 1.0 mL of CSF was withdrawn through cisterna magna and then 1 mL autologous arterial blood was injected in all rabbits over 1 minute. After 5 days, neurologic severity score (NSS) and vertebrobasilar angiograms of all rabbits were repeated. Rabbits without radiologic vasospasm or spasm under 50% (n=7) were termed as group 1. Rabbits whose cerebral vasospasm were 50% or over 50% (n=7) and NSS is lesser than 3 were termed as groups 2, and rabbits whose cerebral vasospasm were 50% or above 50% (n=7) and NSS is greater than 3 were termed groups 3. On day 7, the CSF lactate values of each group were significantly different (P<0.05) with each other. But when compared with only CSF baseline lactate values groups 2 and 3 were significantly different (P<0.05). However, the NSSs were similar in groups 1 and 2, but group 3 significantly differed from groups 1 and 2 (P<0.05). All groups significantly differed from baseline NSSs (P<0.05). The data showed clearly that the degree of vasospasm correlates not only with neurologic status but also with CSF lactate levels. We suggest that CSF lactate level may be useful as a surrogate marker of cerebral vasospasm degree after subarachnoid hemorrhage in clinics where invasive cerebral angiography could not be assessed for whatever reasons.

Cisternal talc injection in dog can induce delayed and prolonged arterial constriction resembling cerebral vasospasm morphologically and pharmacologically

BACKGROUND

The possible role of inflammation in the pathogenesis of cerebral vasospasm has been noted in recent studies. In order to examine the role of inflammation, we examined the vasocontractile activity of talc, which is known to cause severe inflammation, using a canine cisternal talc injection model.

METHODS

Under general anesthesia, a sterile talc powder suspended in saline was injected into the cisterna magna of the dog. Serial vertebral angiography and postmortem histologic changes of the harvested basilar artery were examined. The morphologic and pharmacologic features of talc-induced vessel spasm were compared with the usual autologous blood-induced artery spasm.

RESULTS

Cisternal injection of sterile talc powder caused no early spasm, but induced definite basilar arterial constriction 2 days after injection. This vascular constriction was observed to continue up to 7 days after injection. Ultrastructural study of the constricted vessel revealed several morphologic changes, such as corrugation of the elastic lamina, subintimal proliferation, migration of smooth muscle cells, detachment of endothelial cells, etc.; findings that are compatible with the changes observed in vasospasm. Pharmacologic study showed a moderate decrease in the maximal contraction to KCl and UTP. Endothelium-dependent relaxation was markedly disturbed, while endothelium-independent relaxation was preserved. These pharmacologic properties were also similar to those reported in vasospasm.

CONCLUSIONS

Our present study indicates that the several changes of vascular properties, which had been considered to be specific to cerebral vasospasm, can be regarded as a nonspecific biologic defense reaction against the foreign body. The analysis of the common pathway from talc and autologous blood to vasospasm may lead to the pathogenesis of cerebral vasospasm.

Evidence of the role of hemolysis in experimental cerebral vasospasm

The short-term (less than or equal to 72-hour) reaction to subarachnoid injections of various blood components was determined in a canine model of cerebral vasospasm. Platelet-rich plasma (PRP) formed durable clots in the basal cistern surrounding the basilar artery and provoked no vascular reaction in 72 hours or more. Freshly isolated autologous erythrocytes resuspended in PRP likewise provoked no vasoconstriction in 72 hours although a second injection of fresh erythrocytes in PRP induced significant reaction, as in the conventional "double subarachnoid hemorrhage (SAH)" canine model. Hemolysate of fresh erythrocytes led to a severe immediate vascular reaction after introduction into the basal cistern using PRP as the carrier/clotting medium, as did the injection of intact erythrocytes incubated ex vivo for 72 hours. Resolution of the initial reaction was rapid for hemolysate, but slow and (depending on hematocrit) incomplete for intact "aged" erythrocytes. In vitro measurements of erythrocyte lysis in these media and histological examination indicate that the production of erythrocyte lysate was responsible for the vascular reaction observed, suggesting that the rate of lysis of erythrocytes in the subarachnoid clot is a major factor in the genesis of vasospasm after SAH.

Transcranial Doppler sonography within 12 hours after subarachnoid hemorrhage

Twenty-one patients were subjected to repeated assessment of cerebral blood flow velocities by means of transcranial Doppler sonography (TCDS) during the first 12 hours after subarachnoid hemorrhage (SAH). In 19 patients the study was performed following the first SAH, and in two after early rebleeds. Flow velocities did not indicate an early phase of arterial narrowing in any case. Following the first TCDS assessment, flows were evaluated repeatedly in the 19 survivors. Increased flow velocities suggesting arterial narrowing or vasospasm occurred only after a delay of at least 4 days. The results of this study favor the restoration of normal velocity patterns in surviving patients and do not indicate that an acute phase of vasospasm exists either immediately after or in the first 12 hours after SAH.

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.

Bifrontal interhemispheric approach to aneurysms of the anterior communicating artery

The authors review their experience with the bifrontal interhemispheric approach in 603 cases of single anterior communicating artery (ACoA) aneurysms and describe the operative technique. With this approach, the olfactory tracts are dissected, and both A1 segments of the anterior cerebral arteries are identified subfrontally. The interhemispheric fissure is then dissected and A2 segments are followed from the distal portion toward the ACoA complex. Following the administration of a combination of mannitol, vitamin E, and dexamethasone, a temporary clip is placed on at least the dominant A1 segment prior to dissection of the aneurysm itself. Once the aneurysm has been completely freed from the surrounding structures, the neck is ligated and clipped. If the aneurysm ruptures during surgery, temporary clips are placed on both A1 and A2 segments bilaterally and the operation proceeds in a completely dry field. With this method, it is possible to occlude any of the intracranial vessels for up to 40 minutes within 100 minutes of drug administration. To prevent the possibility of rerupture and the development of vasospasm in the period before aneurysm surgery, the authors have adopted a policy of performing ultra-early operations within 48 hours of the onset of symptoms. Among the 257 cases operated on during the 9 years since 1975, one-fifth have been operated on within 48 hours of rupture, and the in-hospital mortality rate has been only 4.3% (11 cases). Follow-up studies have shown that 87% of the 246 surviving patients have returned to useful lives.

Surgical treatment of middle cerebral artery aneurysms

The authors report their experience with the surgical therapy of middle cerebral artery (MCA) aneurysms in 413 cases, and describe their technique. After the M1 portion of the MCA is identified, the Sylvian fissure is opened. During the administration of 20% mannitol, temporary occluding clips are applied to the feeding and draining vessels of the aneurysm. The aneurysm is freed from all surrounding tissue, and the aneurysm neck is treated by ligation, clipping, or wrapping. Analysis of surgical results in 91 cases operated on after the surgical approach had become standardized indicates that more than 94% of patients have returned to useful social lives by the time of follow-up evaluation. Twenty-four percent of these patients were operated on within 48 hours after subarachnoid hemorrhage.

In vivo characterization of vasocontractile activities in erythrocytes

Partially purified protein from washed and artificially hemolyzed erythrocytes, known to cause significant contractions of isolated canine cerebral vessels in vitro, was injected into the cisterna magna of intact anesthetized dogs. Cerebral blood flow, measured by the xenon-133 washout technique, decreased from a control value of 49.5 +/- 1.17 ml/100 gm/min to an experimental value of 34.1 +/- 1.65 ml/100 gm/min at 2 hours. Cerebral vascular resistance rose from a control value of 2.05 +/- 0.17 PRU (peripheral resistance units) to an experimental value of 2.91 +/- 0.25 PRU at 2 hours. Mean arterial blood pressure, heart rate, intracranial pressure, and cerebral perfusion pressure remained stable. Cardiac output also fell significantly (in 2-hour control animals it was 2.89 +/- 0.37 liter/min, and in 2-hour experimental animals 1.43 +/- 0.13 liter/min) and peripheral vascular resistance rose. These changes were evident by 10 minutes after the cisternal injection of the hemolysate protein, and remained for the duration of the 2-hour monitoring period. Serial vertebrobasilar angiograms demonstrated marked narrowing of the intracranial basilar artery when compared to control values. The narrowing persisted for several days in most animals, and tended to increase with time. Relaxation occurred by the 10th through the 14th day. The authors conclude that this experimental preparation may be a useful model for both in vitro and in vivo investigation of chronic cerebral vasospasm.

The effect of prostacyclin on cerebral vasospasm. An experimental study

Prostacyclin (PGI2), a strong vasodilator of cerebral vessels and potent inhibitor of platelet aggregation, was infused intravenously into seven cats after induction of prolonged vasospasm by hourly application of oxyhaemoglobin solution into the subarachnoid space round the basilar artery. PGI2, at a concentration of 50 ng/kg/min, was effective in releasing the vasospasm in the seven cats. It did not produce significant hypotension. This report gives our results and the probable mechanism of action of PGI2 in cerebral vasospasm.

Relation of cerebral vasospasm to operative findings of subarachnoid blood around ruptured aneurysms

An investigation was carried out in 28 patients in order to evaluate the relationship between angiographically documented vasospasm, amount of subarachnoid blood found at surgery around ruptured intracranial aneurysms, and delayed ischaemic deficits. Angiography was performed at time intervals ranging between 5 and 17 days, and surgery not later than 21 days following subarachnoid haemorrhage. The absence of subarachnoid clots was associated in ten patients, with no or minor vasospasm and no or mild neurological deficits. Thin clots were found in eight patients; one of them had no vasospasm, six had minor vasospasm, and one showed severe vessel narrowing. Major clinical signs were absent in these cases. All ten patients with thick clots developed severe vasospasm, and eight of them severe neurological signs. The important aetiological role of local subarachnoid clots developed severe vasospasm, and eight of them severe neurological signs. The important aetiological role of local subarachnoid clots in determining vasospasm in emphasized in view of surgical timing.

Correlation between CT findings and subsequent development of cerebral infarction due to vasospasm in subarachnoid haemorrhage

We have studied the correlations between computed tomograms (CT), clinical severity at the time of onset, and subsequent development of cerebral infarction due to vasospasm in 32 cases with subarachnoid haemorrhage secondary to rupture of cerebral aneurysms. It was found that the clinical severity could be judged by CT as shown by the amount of blood in subarachnoid space. Furthermore, it was possible to predict the subsequent occurrence of cerebral infarction by sequential findings of CT. A Hounsfield number of the high density area over 60 showed good correlation with the development of cerebral infarction.

Preliminary characterization of vasocontractile activities in erythrocytes

The vasocontractile activities of washed red cell preparations hemolyzed by various methods were studied in vitro using isolated canine basilar arteries. Significant contractions were induced by each preparation. The maximum strength of contraction attained by the various preparations was similar. The contractile activity appeared to be dose-related, and molecular exclusion chromatography demonstrated that the activity migrated with the fraction of approximately 40,000 to 45,000 molecular weight. The vasocontractile effect of the active fraction was sustained in vitro when tested against basilar artery, but was inactive in peripheral arterial preparations. Preliminary biochemical characterization indicates that the contractile activity resides in a protein. Enzymatic digestion of the crude fraction appears to enhance the contractile activity significantly, and this observation suggests a possible mechanism for the delayed onset of ischemic symptoms encountered in the clinical situation.

The effect of intracarotid perfusion of cerebrospinal fluid from patients with subarachnoid hemorrhage on cerebrovascular reactivity in rats

Cerebrovascular resistance was measured in 10 rats with increasing dosages of 5-Hydroxytryptamine (5-HT). The internal carotid artery was perfused at constant flow with cerebrospinal fluid (CSF) from patients with ruptured intracranial aneurysms, and dose-response curves to 10 mu 1 boluses of 5-HT were compared with similar dose-response curves obtained during perfusion with Krebs' solution and with normal CSF (CSF-N). CSF from patients with subarachnoid hemorrhage (CSF-SAH) produced increased sensitivity to 5-HT.

Possible role of the erythrocyte in causing prolonged cerebral vasospasm

Contractile activity of the various fractions of fresh and incubated blood was studied in vitro using the isolated canine basilar artery. Of the various fractions of fresh blood, significant contraction was induced by serum, but moderate contraction was induced by platelet-rich plasma and lysed red cells, while intact red cells and platelet-poor plasma had no significant activity. The contractions induced by serum and platelet-rich plasma were blocked by phenoxybenzamine, while those induced by lysed red cells were not. Whereas serum and platelet-rich plasma lost their contractile activity after 24 hours of incubation, lysed red cells retained activity up to 7 days after incubation. Biochemical analysis of the hemolysate by means of Sephadex column chromatography revealed that the contractile substance(s) possessed a molecular weight above 5000. These results suggest the possibility that the above substance(s) may play a role in prolonged cerebral vasospasm.

Vasoconstriction of external carotid arteries after rupture of intracranial aneurysms

Vasoconstriction of the external carotid arteries, which has not been previously reported, was investigated angiographically in 23 patients who had intracranial vasospasm after aneurysm rupture. In about 50% of these patients vasoconstrictive change in the external carotid arteries was also found. These changes were not seen in control cases without intracranial vasospasm. Pathogenesis of the vasoconstriction of the external carotid arteries was discussed with particular emphasis on the relationship with sympathetic nerves.

An analysis of follow-up results of 1000 intracranial saccular aneurysms with definitive surgical treatment

The authors report a follow-up review of 1000 cases of intracranial definitive surgery for saccular aneurysms. The prognosis for such surgical cases is discussed. Postoperative results at least 6 months after discharge from the hospital were analyzed in 876 (93.3%) of the 939 surviving patients. The longest follow-up period was 14 years and 5 months, with an average of 3 years and 7 months. At the time of discharge, there were 543 excellent results, 186 good, 117 fair, 93 poor, and 61 deaths. The chief findings were as follows: 1) Most of the patients determined as "excellent" or "good" at discharge were able to return to normal life; most of the deaths or instances of worsened condition found in the follow-up study were due to new lesions. 2) Fully 62% of the cases determined as "fair" at discharge were found in an improved state at the follow-up study, having returned to normal life. 3) Only 19% of cases determined as "poor" at discharge had improved to the point where a return to normal life was possible, the majority having died or remaining in poor condition.