Value of computed tomography in the prediction of cerebral vasospasm after aneurysm rupture

Accuracy of high resolution computed tomography in direct diagnosis of cerebral aneurysms

With high resolution computed tomography (CT) of the skull, performing rapid series of 1.5 mm slices during an intravenous bolus injection of contrast medium, an angiography-like image (angio-CT) of the basal cerebral arteries can be obtained. From 76 consecutive angiographically or autopsy-verified cerebral aneurysms of various size down to 3 mm in diameter, 74 (97.4%) were shown up by the angio-CT. One ruptured and one incidental aneurysm escaped CT visualization. Besides the correct localization of the aneurysms, angio-CT provides information concerning the size and main direction of the aneurysms and yields, in addition, a coronal view of the aneurysms and their surrounding structures. Pitfalls for mis-diagnosis can be the following: Aneurysms of below 5 mm in diameter, located at the supraclinoid part of the carotid artery, multiple or non-ruptured aneurysms, bony or movement artefacts, poorly contrasted vessels due to wrong injection technique of contrast medium or vasospasm, and incorrect interpretation.

Evaluation of the calcium-antagonist nimodipine for the prevention of vasospasm after aneurysmal subarachnoid haemorrhage. A prospective transcranial Doppler ultrasound study

70 consecutive patients admitted within four days after the first aneurysmal subarachnoid haemorrhage (SAH) were evaluated by daily transcranial Doppler ultrasound (TCD) measurement of the blood flow velocities (BFVs) of both middle cerebral arteries (MCAs) and by daily recordings of their clinical grade (Hunt and Hess). Patients with no or only little subarachnoid blood in the first CT after admission were classified as low-risk for the development of symptomatic vasospasm (VSP), and patients with big subarachnoid clots or thick layers of subarachnoid blood were graded as high-risk patients for symptomatic VSP. The first series of 33 patients received no nimodipine whereas the second series of 37 patients were treated with nimodipine 2 mg/h intravenously, starting within 24 hours after the SAH in the majority of patients. 7-14 days postoperatively, the intravenous dose was changed to oral nimodipine 60 mg/q4h for one week and then discontinued. A mean BFV curve of the side with the higher flow velocities correlated with the mean clinical status (Hunt and Hess) was calculated by computer analysis for the patients treated without nimodipine and for those receiving nimodipine in each risk group. The mean BFV curves of the same risk groups were compared in order to evaluate the effect of nimodipine for the prevention of vasospasm following SAH. The delayed neurological deficits (DIND) and the functional outcome six months after the SAH were recorded in each group and compared. Nimodipine given within four days after the SAH did not prevent vasospasm evaluated by TCD, but it significantly reduced the severity of the vasoconstriction, especially in high-risk patients. It reduced significantly the incidence of DIND in high-risk patients and improved their functional outcome. Although nimodipine may have a reduced efficacy in preventing vasospasm after early operation of high-risk patients, it probably protects the brain by increasing its tolerance to focal ischaemia.

Management of ruptured intracranial aneurysm: a review

The discouraging history associated with management of aneurysmal subarachnoid haemorrhage (SAH) is reviewed along with improvements in outlook attributable to progress made within the past decade. Among the new developments is the introduction of microsurgical techniques that allow elective surgery in the acute stage thereby preventing repeat haemorrhages. Early operation also offers the possibility of a more aggressive pharmacological anti-ischaemic treatment. Notwithstanding the improved results of acute elective surgery and the fact that delayed ischaemic deterioration (symptomatic cerebral vasospasm) now may be almost eliminated, the overall outcome remains gloomy. Despite recent advances not more than one out of three individuals, who are struck by the rupture of an intracranial aneurysm, may be expected to make a good neurological and functional recovery. Hope for further improvements may depend on the development of techniques that can identify intracranial aneurysms before they rupture and increased knowledge of the aetiology of such arterial wall lesions.

Early management of the patient with recent aneurysmal subarachnoid hemorrhage

Despite its efficacy in preventing rebleeding, the anticipated strong trend in favor of early intracranial surgery has not been achieved. Early intracranial operation remains a useful choice in the management of recent SAH in good-risk patients, but patients must be carefully selected on an individual basis. Many patients will undoubtedly benefit from early surgery but it is not a panacea. Further investigation of surgical treatment in combination with improved preoperative and postoperative medical therapy will be required to ameliorate the outcome of SAH. In particular, the prevention and treatment of cerebral infarction deserves attention. The results of the antifibrinolytic and timing of intracranial surgery studies point to the need for an effective prevention treatment regimen for vasospasm. Further studies about the efficacy of calcium channel blocking drugs in prevention of ischemia after SAH are needed among patients given antifibrinolytic drugs or having early operation. All the advances in treatment are predicated on prompt diagnosis of SAH in good-condition patients. The medical community needs to maintain a high degree of vigilance for the diagnosis of SAH in all patients complaining of a new, unusual or severe headache. Early referral to properly equipped and staffed medical facilities remains a keystone to effective treatment of SAH.

Cerebral vasospasm evaluated by transcranial ultrasound correlated with clinical grade and CT-visualized subarachnoid hemorrhage

In 39 patients with a proven subarachnoid hemorrhage (SAH), the clinical status, the amount of subarachnoid blood on a computerized tomography scan obtained within 5 days after SAH, and the flow velocities (FV's) in both middle cerebral arteries (MCA's) measured by transcranial Doppler sonography were recorded daily and correlated. All patients had pathological FV's over 80 cm/sec between Day 4 and Day 10 after SAH. The side of the ruptured aneurysm showed higher FV's than did the unaffected side in cases of laterally localized aneurysms. Increase in FV preceded clinical manifestation of ischemia. A step early increase of FV's portended severe ischemia and impending infarction. Maximum FV's in the range of 120 to 140 cm/sec were not critical and in no case led to brain infarction. Maximum FV's over 200 cm/sec were associated with a tendency for ischemia, but the patients may remain clinically asymptomatic. In cases of no or only a little blood in the basal cisterns, mean FV's in both MCA's increased only moderately whereas, with thick clots of subarachnoid blood, there was a steeper and higher increase of mean FV's.

Enhanced cisternal drainage and cerebral vasospasm in early aneurysm surgery

Enhanced cisternal drainage was performed following early aneurysm surgery in patients with Hunt and Kosnik grades I-III, to effect continuous wash-out of subarachnoid blood clots and reduce symptomatic vasospasm. Following extensive evacuation of the cisternal blood clots, the Liliequist's membrane was opened extensively and a third ventriculostomy was effected by opening the lamina terminals. The drainage effect was considered as poor, moderate or fair, depending on the average amount of CSF drainage/day. SAH was graded into 0-III depending on the severity of cisternal haematoma in the pre-operative CT. No symptomatic vasospasm occurred in patients with SAH grade I. In SAH grade II + III patients symptomatic vasospasm occurred in 78, 60 and 42% of patients with a poor, moderate and fair drainage effect, respectively. Nine patients who developed symptomatic vasospasm were treated by hypertensive/hypervolemic therapy (HHT). The HHT was effective in 7 patients with fair and moderate CSF drainage and ineffective in 2 patients with poor a drainage effect. It seems, that enhanced post-operative cisternal drainage can reduce the incidence of symptomatic vasospasm and be of benefit to the outcome of early aneurysm surgery.

Outcome evaluation following subarachnoid hemorrhage

Seventy-eight individuals among a population of 1.46 million suffered aneurysmal subarachnoid hemorrhage (SAH) during 1983. Within 24 hours after the bleed, 32 of the 78 patients were in Hunt and Hess neurological Grades I to II, 13 were in Grade III, 21 were in Grades IV to V, and 12 were dead on admission to a hospital or forensic department. When the amount of blood visualized on computerized tomography (CT) scanning was integrated with the Hunt and Hess neurological classification in order to improve prediction of prognosis, only 16 patients were considered to have a good prognosis (CT-modified Grades I to II), 21 had a less favorable prognosis (CT-modified Grade III), and 29 had a poor prognosis (CT-modified Grades IV to V). Assessment at 1 year revealed that only 32 patients (41%) had a good physical recovery. The physical morbidity rate was 22%, and the overall mortality rate was 37%. Twenty-six individuals with a good neurological outcome and five with a fair outcome also underwent reexamination 1 year or more post-SAH, which included a comprehensive evaluation of the quality of life, assessment of cognitive dysfunction, and determination of general adjustment. Five of the patients with a good neurological outcome and all five with a fair outcome (four of whom had had a poor prognosis in the acute stage) showed severe psychosocial and cognitive incapacitation. When functional morbidity, based upon persistent severe cognitive and psychosocial impairment, was included in the outcome assessment, only 33% of the total series was considered to have a favorable outcome. Approximately 60% of the initially good-risk patients (Grades I and II) showed a good physical outcome without concomitant indications of severe cognitive dysfunction and/or psychosocial impairment. Among the good-risk patients with a CT-modified grade, the figure was 70%. It is suggested that in any outcome grading system, persistent cognitive and psychosocial disturbances be taken into account.

Intracranial aneurysms and subarachnoid hemorrhage in children and adolescents

Thirty-eight cases of symptomatic cerebral aneurysms or spontaneous subarachnoid hemorrhage in children and adolescents were observed from 1965 to 1984; 33 cases were treated from 1970 to date. This group represents 2.6% of the total number of patients with subarachnoid hemorrhage treated at our institute in the same period. The cause of subarachnoid hemorrhage was unknown in 7 cases; an intracranial aneurysm had ruptured in 29 cases, and was unruptured but symptomatic in 2 remaining cases. Three aneurysms were mycotic. The most frequent aneurysmal locations were the internal carotid bifurcation and the anterior communicating artery; peripheral branches of the middle cerebral artery were also a relatively common location. Four patients were 3 years of age or younger: each presented peculiar clinical features, and 3 of the 4 had middle cerebral artery aneurysms. The remaining 34 patients were all above 9 years of age. Two groups were identified: (a) in 14 patients between 10 and 15 years of age, the aneurysm was most commonly at the internal carotid bifurcation (37%), and an intracerebral hematoma was observed in 50% of these cases; (b) in 20 patients between 16 and 20 years of age, the most common aneurysmal location was the anterior communicating artery (35%), and intracerebral hematomas were rare (10% of cases). Among patients with aneurysms, 19 underwent surgical exclusion by clip, with 10% morbidity and 5% mortality; 5 patients in moribund conditions were not operated on; 5 patients were conservatively treated; in 2 patients the aneurysm had disappeared at a second angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage is one of the most important causes of cerebral ischemia, and is the leading cause of death and disability after aneurysm rupture. There are two definitions of cerebral vasospasm: angiographic and clinical. Care must be exercised to be certain that it is clear which entity is being addressed. The diagnosis of the clinical syndrome is one of exclusion and can rarely be made with absolute certainty. The pathogenesis of cerebral vasospasm is poorly understood. Most current theories focus on the release of factors from the subarachnoid clot. More attention must be given to the role of endothelial damage and alterations in the blood-arterial wall barrier. The application of modern techniques for studying vascular smooth muscle which have been developed as a result of research in the areas of hypertension and atherosclerosis must be applied to the problem of cerebral vasospasm. A stress test to select patients with angiographic arterial narrowing who have adequate cerebral vascular reserve to undergo surgery should be developed. The optimal treatment of vasospasm awaits development of agents for blocking or inactivating spasmogenic substances or blocking arterial smooth muscle contraction. Rheological or hemodynamic manipulations to prevent or reverse ischemic consequences of vasospasm are relatively effective, but complicated and hazardous, and should be viewed principally as interim measures awaiting development of more specific therapies for the arterial narrowing.

Incidence of delayed cerebral ischaemia following subarachnoid haemorrhage of unknown cause

A retrospective study was made of 50 consecutive patients with spontaneous subarachnoid haemorrhage for which no cause was found, looking for evidence of delayed cerebral ischaemia particularly during the first 2 weeks after the bleed. Twenty-three patients had blood visible on the CT scan but only 4-6% developed delayed ischaemia, all of whom made a good recovery. The low incidence of this complication in this group of patients suggests that subarachnoid blood is not a sufficient cause for delayed ischaemia.

Intimal proliferation of cerebral arteries after subarachnoid blood injection in pigs

A model of experimental subarachnoid hemorrhage in young pigs has been created using two subarachnoid blood injections. Cerebral arteries of the pig demonstrate intimal proliferation and medial necrosis 10 days after experimental blood injection; this appears to be a reaction to arterial injury. The similarity between the arterial reaction to subarachnoid blood and the general process of atherosclerosis is noted, and steps have been taken to insure that the vasculopathy described is truly a response to the injected blood. The authors conclude that the intimal proliferation observed between 1 and 2 weeks after experimental subarachnoid blood injection is an indicator of arterial injury and is, therefore, a good end point for further studies.

Cerebral vasospasm after subarachnoid hemorrhage

Chronic cerebral vasospasm remains the most important cause of subsequent morbidity in patients who survive the first 48 to 72 hours after a subarachnoid hemorrhage. Prolonged arterial narrowing compromises cerebral hemodynamics and results in cerebral ischemia. Among patients in whom symptomatic chronic cerebral vasospasm develops, almost half die or have a serious residual neurologic deficit. Present evidence indicates that sustained vessel narrowing results from structural changes within the arterial wall rather than from active contraction of vascular smooth muscle. The mechanism (or mechanisms) responsible for these changes is unknown, but damage from prolonged active arterial contraction, depression of vessel wall respiration, and an inflammatory response have all been proposed as explanations. Despite more than 30 years of intensive study, an effective treatment program for chronic cerebral vasospasm remains elusive. Recent therapeutic trials, however, based on efforts to interrupt the mechanisms responsible for these structural changes hold some promise.

Intracranial vessels lack vasa vasorum

A micro-corrosion technique was used to demonstrate an extensive vasa vasorum network in extracranial vessels but did not reveal this system in intracranial vessels of comparable size in three species of animals. The absence of a vasa vasorum network in cerebral vessels may result in a higher level of susceptibility to periarterial abnormalities, such as cerebral vasospasm secondary to subarachnoid hemorrhage.

Removal of subarachnoid blood clots after subarachnoid hemorrhage

The difficulty in removing subarachnoid blood clots was evaluated in terms of the interval after subarachnoid hemorrhage. Subarachnoid blood clots were removed from a total of 30 cisterns with a Hounsfield unit of more than 70. In 20 cisterns, removal was performed within 24 hours, and in 10 between 24 and 72 hours after subarachnoid hemorrhage. In 16 of the 20 cisterns (80%) and in 4 of the 10 cisterns (40%), the density was reduced to a Hounsfield unit of less than 60 after removal of subarachnoid blood clots. Two typical cases are presented.

Prediction of cerebral vasospasm value of fibrinogen degradation products (FDP) in the cerebro-spinal fluid (CSF) for prediction of vasospasm following subarachnoid haemorrhage due to a ruptured aneurysm

In a new treatment regimen with antifibrinolytic drugs in patients with aneurysmal subarachnoid haemorrhages, we have systematically controlled the level of fibrinogen degradation products (FDP) in the cerebrospinal fluid (CSF). The frequency of severe vasospasm with clinical ischaemia has been compared with the patient's initial level of FDP. Fifty patients have been included in this study. (All in Hunt and Hess's grades I or II on their arrival.) Patients with a secondary deterioration unrelated to vasospasm were excluded. The FDP levels were measured in the first three days following the bleeding and we were informed of them at the end of the study. The diagnosis of severe vasospasm was confirmed by arteriography and computed tomography (CT) and it was named "severe" when accompanied with signs of clinical ischaemia. Twenty patients developed a severe vasospasm with clinical ischaemia. In these patients, the mean value of the initial FDP level was between 80 and 320 mcg/ml compared with 20 to 80 mcg/ml for those who had not developed clinical ischaemia (p = 0.0009). Furthermore, two different groups may be discriminated by their initial FDP level: FDP greater than 80 mcg/ml; n = 23, 65% severe vasospasm; FDP less than 80 mcg/ml; n = 27.8% no severe vasospasm (p less than 0.001). These results do not imply a direct role of FDP in pathophysiological mechanisms of vasospasm, but they suggest a relationship between the clot lysis and the appearance of vasospasm with clinical ischaemia. To our knowledge this is the first time that such a predictive role can be attributed to the initial FDP level in the prognosis of vasospasm.

An experimental study of the influence of antifibrinolytic therapy on post-subarachnoid-hemorrhagic cerebral vasospasm and hydrocephalus

The incidence and severity of cerebral vasospasm and hydrocephalus following induced subarachnoid hemorrhage in an experimental group of animals that subsequently received epsilon-aminocaproic acid was compared to that seen in a control group that received no antifibrinolytic therapy. No augmentation of either vasospasm or hydrocephalus could be attributed to the epsilon-aminocaproic acid in the treated as compared to the control group.

Cerebral vasospasm after subarachnoid hemorrhage: an update

Symptomatic vasospasm, or delayed cerebral ischemia associated with arteriographic evidence of arterial constriction, is currently the most important cause of morbidity after acute subarachnoid hemorrhage. The development of vasospasm is directly correlated with the presence of thick blood clots in the basal subarachnoid cisterns, which can be detected by an early computed tomographic scan. Symptomatic vasospasm usually develops between 4 and 12 days after subarachnoid hemorrhage. The onset is gradual, occurring over hours or days. There is typically a gradual deterioration of the level of consciousness, accompanied by focal neurological deficits that are determined by the arterial territories involved. Hyponatremia frequently occurs and may exacerbate the symptoms. The patients are usually volume depleted, and therefore many authorities now treat them with replenishment and expansion of their intravascular volume with colloid and blood. Volume expansion, together with elevation of the systemic blood pressure and reduction of the intracranial pressure when elevated, constitute the only currently available effective therapy for symptomatic vasospasm. The cause of vasospasm remains obscure. Mechanisms of smooth muscle cell contraction and relaxation and experimental efforts to elucidate the nature of vasospasm are reviewed.

Pituitary apoplexy and vasospasm

Two cases of pituitary apoplexy complicated by cerebral vasospasm are described. They emphasize the importance of angiography in the investigation of a protracted clinical course after pituitary apoplexy. The pathophysiology of postapoplectic vasospasm is discussed.

Correlation between angiographic vasospasm, hematoma, and ischemic brain damage following SAH

The correlation between angiographic vasospasm, hematoma, and ischemic brain damage was studied in 29 patients who died as a result of subarachnoid hemorrhage following rupture of a saccular aneurysm. None of these patients was treated surgically. A comprehensive neuropathological examination was undertaken in each case. A significant relationship between the presence and degree of vasospasm and ischemic brain damage was found. Furthermore, even though intracerebral hematoma probably increased the risk of infarction associated with vasospasm, hematoma per se did not increase the incidence of ischemic brain damage.

Effect of early operation for ruptured aneurysms on prevention of delayed ischemic symptoms

The effect of removal of subarachnoid blood clots on the prevention of delayed ischemic deficit was evaluated in 239 consecutive patients with ruptured supratentorial non-giant aneurysms. All patients were hospitalized within 24 hours after subarachnoid hemorrhage (SAH) and were classified in Grades 1 to 4 according to the system of Hunt and Hess; classification was made immediately preoperatively in patients operated on within 48 hours after SAH, or 48 hours after SAH in patients for whom delayed operation was planned. Delayed ischemic deficit causing permanent disability or death occurred in 11 (25%) of 44 patients in whom surgery was planned to be delayed for 10 days or more, in 26 (27.7%) of 94 patients in whom the aneurysms were obliterated and blood clots adjacent to them were removed within 48 hours of SAH, and in 11 (10.9%) of 101 patients in whom the aneurysms were obliterated and extensive and aggressive removal of thick subarachnoid clots lying along the arteries (identified on computerized tomographic scan) was performed within 48 hours of SAH. Accordingly, early operation is an effective and reliable method to reduce the occurrence of severe delayed ischemic deficit only when subarachnoid blood clots are removed extensively and aggressively along the arteries within 48 hours of SAH.

Chronic cerebral vasospasm after large subarachnoid hemorrhage in monkeys

The authors have developed a model of chronic cerebral vasospasm analogous to the clinical situation, by inducing a large subarachnoid hemorrhage (SAH) in monkeys. With this model, the size of the SAH apparent on the first computerized tomography (CT) scan was correlated with the incidence and severity of cerebral vasospasm that developed. Indices monitored for up to 21 days after SAH included cranial CT scan, cerebral blood flow, vessel caliber, and neurological status. The 18 monkeys studied for 48 hours or more were divided into two groups according to the size of the SAH on CT scan. Vasospasm was more common in the group with large SAH. In this group, on Days 0, 7, and 14, the incidence of vasospasm was significantly higher than at other times (p less than 0.001, p less than 0.01, and p less than 0.05, respectively), and the percentage reduction in vessel caliber was significantly greater than in the group with small/medium SAH (Day 7, p less than 0.02; Days 0 and 14, p less than 0.05). Delayed neurological deficit developed in two monkeys with large SHA. Apathy was noted from Day 17 to Day 21 in one, and unsteadiness and drowsiness were noted on Days 4 and 5 in the other. Overall, the incidence, degree, and time course of vasospasm reflected the size of the hemorrhage.

Angiographic study of vasospasm following subarachnoid hemorrhage in monkeys

A model for producing chronic cerebral vasospasm in monkeys by injecting autologous blood into the basal cistern is described. Spasm/narrowing was observed by angiography one hour after SAH in 8 out of 10 monkeys and in 5 of these 8, spasm was observed both one and two weeks later. No narrowing of the vessels was observed in the control cases. In monkeys that showed spasm one week after SAH, narrowing of the extracranial vertebral arteries was also observed. Repeated injections of blood at intervals of one and two weeks caused intensification of spasm in the intracranial portion of vertebral arteries and the basilar arteries. It is suggested that cerebral vasospasm following SAH may in part be mediated by a central control mechanism acting through the sympathetic nervous system in that extracranial vessels remote from direct contact with blood showed reactive narrowing.

Mortality study of patients with subarachnoid haemorrhage at University hospitals and their affiliated hospitals in Japan

This study was undertaken to examine the differences in aneurysm statistics between University hospitals where subacute or chronic patients are primarily treated and University-affiliated hospitals where both acute and chronic cases are also admitted. In each hospital group, the transition of the statistics in the last decade was studied. The purpose of this study was also to see if any conclusion could be drawn regarding the surgical treatment of acute cases. The death rate for all aneurysm cases admitted is 8% at University hospitals, whilst that at affiliated hospitals is roughly 30% during the 1970s. The operative death rate at the University hospitals is 3%, whilst that at affiliated hospitals is 16% which improved at one affiliated hospital to 8% in the 1980-1981 period. Morbidity also improved in the latest series in the affiliated hospital. These improvements are considered to be de to the change of operative and postoperative policies for acute cases to: limited surgical indications for grade IV patients, extensive cisternal clot removal at the time of surgery, and oral administration of Ticlopidine, a new antiplatelet agent.

An analysis of vasospasm following early surgery for intracranial aneurysms

41 patients with ruptured intracranial aneurysms were all submitted to an early operation, (within 3 days from SAH), and evaluated with regard to the results of treatment. In this group, vasospasm has influenced the outcome more than other causes, accounting for 58% of morbidity and 64% of mortality. On the basis of our experience with 380 patients suffering from SAH and all submitted to a CT scan, the presence of consistent intracisternal blood in the CT scan at admission has shown to be the main risk factor resulting in vasospasm. Therefore, the group with early surgery has been compared, on the basis of the CT scan picture, to a group of 76 patients in which surgery had been delayed at least 10 days after SAH. Whilst the incidence of vasospasm has been very similar in the groups compared, the incidence of neurological deterioration brought about by spasm has been higher in patients waiting for surgery (55%, against 36% in the group with early surgery). Avoidance of clinical deterioration has not been always possible with early surgery, even after careful cleansing of the cisterns from clots, as was shown by 2 of our cases. It is concluded that vasospasm does not seem to influence the outcome of early surgery to a greater extent than it would during the natural course of subarachnoid haemorrhage.

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.