Perfusion MRI before and after acetazolamide administration for assessment of cerebrovascular reserve capacity in patients with symptomatic internal carotid artery (ICA) occlusion: comparison with 99mTc-ECD SPECT

INTRODUCTION

Impaired cerebral vascular reserve (CVR) in patients with symptomatic internal carotid artery (ICA) occlusion is regarded as a possible indication for performing extra-/intracranial (EC/IC) bypass surgery. As perfusion MR imaging (MRI) can demonstrate cerebral haemodynamics at capillary level, our hypothesis was that perfusion MRI could be used in these patients for the evaluation of CVR following acetazolamide challenge in a similar way to single photon emission CT (SPECT) and might provide additional information.

METHODS

Enrolled in the study were 12 patients (mean age 61.3 years; 11 male, 1 female) with symptomatic unilateral ICA occlusion proven by angiography. Both perfusion MRI and 99m-technetium-ethyl-cysteinate dimer ((99m)Tc-ECD) SPECT were performed before and after injection of acetazolamide (Diamox ,1000 mg i.v.). CVR parameters including regional cerebral blood flow (rCBF) and volume (rCBV), and mean transit times (MTT) were measured by perfusion MRI.

RESULTS

The patients with impaired CVR proven by SPECT (n = 9) had a negative mean rCBF increment (-46.52%), negative rCBV increment (-13.5%) and delayed MTT (mean +2.98 s), respectively, on the occluded side (Student's t-test all P < 0.05). The patients with sufficient CVR (n = 3) had a mean rCBF increment of 1.2%, a decrement of rCBV of 10.46%, and a mean MTT shortening of 0.27 s following the acetazolamide injection.

CONCLUSIONS

Perfusion MRI before and after acetazolamide administration compares favourably with (99m)Tc-ECD SPECT for the detection of impaired CVR. The impact that perfusion MRI studies (before and after acetazolamide administration) might have on the treatment decision in patients with ICA occlusion has yet to be determined by a prospective study.

Intraprocedural thrombus formation during coil placement in ruptured intracranial aneurysms: treatment with systemic application of the glycoprotein IIb/IIIa antagonist tirofiban

BACKGROUND AND PURPOSE

When using detachable coils to treat intracranial aneurysms, thromboembolism is the most feared and frequently reported complication during or after endovascular therapy. The purpose of this study was to document the therapeutic effect of tirofiban on patency of the parent vessel, rate of rebleedings, and outcome of the patients in the setting of acute subarachnoidal hemorrhage.

METHODS

A patient data base was retrospectively reviewed to identify patients in whom thrombus occurred during endovascular treatment of ruptured cerebral aneurysms within a 34-month period and who were treated with tirofiban. All patients underwent anticoagulation with heparin during endovascular treatment procedures. Sixteen patients (age range, 52.9 +/- 10.7 years; 10 women, 6 men) were identified with intraprocedural thrombus formation. The patency of the parent vessel was assessed in a retrospective analysis blinded to outcome. Eight patients received ventriculostomy and had a follow-up CT.

RESULTS

Local nonocclusive thrombus at the coil surface was detected in 5 patients, in all of whom the thrombus was dissolved. In 10 patients, partial or total occlusion of the parent vessel occurred during the intervention; in 8 of these, the vessel was recanalized completely and in 2 drug administration was assisted by mechanical means. In 1 patient, however, the occlusion persisted. No periprocedural rebleedings of the ruptured aneurysm occurred; 3 of 8 ventriculostomies had clinically silent small local bleedings.

CONCLUSION

The use of tirofiban in the setting of endovascular treatment of ruptured intracranial aneurysms to dissolve platelet aggregation seems relatively safe and effective.

Neuroprotective effects of a postischemic treatment with a bradykinin B2 receptor antagonist in a rat model of temporary focal cerebral ischemia

Bradykinin, an endogenous nonapeptide produced by activation of the kallikrein-kinin system, promotes neuronal tissue damage as well as disturbances in blood-brain barrier function through activation of B2 receptors. In a rat model of focal cerebral ischemia, blockade of B2 receptors before initiation of ischemia with the B2 receptor antagonist, LF 16-0687 Ms, afforded substantial neuroprotection. In order to assess the potential clinical value of this approach, we evaluated the effect of LF 16-0687 Ms given at reperfusion following focal cerebral ischemia on local cerebral blood flow (LCBF), neurological outcome, and infarct size. Sprague-Dawley rats were subjected to MCA occlusion for 90 min by an intraluminal filament. Animals were assigned to one of four treatment arms (n = 7 each): (1) vehicle, (2) LF 16-0687 Ms (1.0 mg/kg/day), (3) LF 16-0687 Ms (3.0 mg/kg/day), or (4) LF 16-0687 Ms (10.0 mg/kg/day) given at reperfusion and repetitively over 2 days. Neurological recovery was examined daily, and infarct volume was assessed histologically on day 7 after ischemia. Physiological parameters and local CBF were not influenced by the treatment. Significant improvement of neurological outcome was observed on postischemic day 3 in animals receiving 1.0 and 3.0 mg/kg/day of LF 16-0687 Ms (P < 0.05). Inhibition of B2 receptors significantly reduced infarct volume in all treated animals predominantly in the cortex. B2 receptor blockade with LF 16-0687 Ms showed neuroprotective effectiveness even when therapy was initiated upon reperfusion, i.e. 90 min after induction of ischemia. Therefore, blockade of B2 receptors seems to be a promising therapeutic approach after focal cerebral ischemia, which deserves further experimental and clinical evaluation.

Dose finding study of intravenous magnesium sulphate in transient focal cerebral ischemia in rats

BACKGROUND

During many neurovascular procedures temporary occlusion of cerebral arteries is inevitable. Neuroprotective drugs may reduce the risk of cerebral infarction in this situation. Increasing evidence indicates neuroprotective properties of magnesium in cerebral ischemia. Previous experimental studies on the neuroprotective efficacy of magnesium-treatment in transient focal ischemia provide widely differing results using different magnesium doses and treatment-regimens. The present study was conducted to find the maximum protective dose of intravenous magnesium sulphate in a rat model of transient focal ischemia.

METHODS

45 male Sprague-Dawley rats were subjected to 90 minutes of middle cerebral artery occlusion (MCAO) by an intraluminal thread. Animals were randomly assigned to one of 4 treatment arms: (1) vehicle (2) MgSO(4) 1x0.75 mmol/kg (3) MgSO(4) 2x1 mmol/kg (4) MgSO(4) 1 mmol/kg+0.5 mmol/kg/h. Local cortical blood flow (LCBF) was continuously measured by laser-Doppler flowmetry. Functional deficits were quantified daily, infarct volumes were assessed histologically after 7 days.

RESULTS

Magnesium serum levels below 3 mmol/l were well tolerated by the animals. Above 3 mmol/l cardiodepressive effects limited neuroprotection. Total infarct volumes in groups 3 and 4 were significantly reduced by 32% and 42%, respectively, compared to controls. Postoperative neurological recovery was significantly improved in magnesium-treated groups.

CONCLUSION

Continuous magnesium-administration with stable serum concentrations between 2 and 3 mmol/l offered the best protection and was well tolerated. Serum concentrations above 3 mmol/l should not be exceeded. An elevation of magnesium serum levels could be useful for brain tissue protection during procedures which are prone to the risk of temporary vessel occlusion.

Cranial and spinal dural arteriovenous malformations and fistulas: an update

Awareness of a potential arteriovenous fistula is critical for diagnosis of cranial as well as spinal fistulas. The natural history of cranial and spinal dural arteriovenous fistulas has been clarified during the last decade and interdisciplinary therapies have experienced a substantial development recently. The classification of Cognard & Merland is now the most widely accepted one for cranial dural AVF. It is based on the degree of flow reversal in the sinuses and cortical veins and reflects well the natural history of the different lesions and serves as basis for therapeutic indications. Several studies have defined the annual bleeding risk of cranial dural fistulas between 1.8 and 15%, depending on the pattern of venous drainage and initial symptomatology. Surgical, endovascular and radiosurgical methods must be selectively chosen for the treatment. The risk associated with surgical or endovascular treatment of benign fistulas is higher than the risk of eliminating fistulas that have already led to cortical venous reflux. Transvenous endovascular occlusion or surgical disconnection of draining veins is the treatment of first choice for cranial and spinal dAVF with venous flow reversal. Benign cranial dural arteriovenous fistulas are a developing indication for radiosurgery.

Congested residual nidus after preoperative intranidal embolization in midsize cerebral arteriovenous malformations of 3-6 cm in diameter

BACKGROUND

Modern delicate microcatheters allow intranidal embolization of cerebral arteriovenous malformations (AVM). The aim of the current analysis was to assess effects of preoperative intranidal deployment of embolic material on surgical time and blood loss in cerebral arteriovenous malformations of 3-6 cm in diameter.

METHODS

The case records of 38 cerebral AVM between 3 and 6 cm in maximum diameter were reviewed, that had been embolized intranidally with N-butyl 2-cyanoacrylate (Histacryl) and subsequently operated on. Surgical time and blood loss as well as particular intraoperative findings such as a congested nidus and thrombosis of draining veins were registered and correlated with the extent of embolization and the time interval between embolization and surgery.

FINDINGS

Preoperative embolization occluded an estimated range of 10 to 90% of the nidus. Minor embolization related bleeding without clinical relevance occurred in 5 patients. Significant embolization related bleeding resulting in earlier than planned surgery occurred in another 5 patients. All embolization related haemorrhages occurred within 24 hours. Average total operating time was 343+/-106 min and average blood loss was 684+/-858 ml. Unequivocal bleeding difficulty from the nidus and a total blood loss of more than 1000 ml were encountered in 7 instances and dissection was tedious due to a bleeding AVM core in 5 other cases. A congested AVM core was the source of bleeding in 11 patients and paraventricular neovascularization in one. 6 of the 11 cases with a congested AVM core had suffered minor or substantial haemorrhage after a preoperative endovascular procedure. Intraoperative nidus congestion was noted in this series after an interval as long as 2 weeks after the last embolization. Combined management resulted in permanent morbidity in 6 of the 38 cases. In 4 of them the neurological deficit was associated with an intraoperative bleeding problem, in all due to congested nidus. Morbidity had to be correlated with major haemorrhage resulting from preoperative embolization in 2 instances.

CONCLUSIONS

Intranidal embolization prior to surgical removal of AVM can lead to a congested residual nidus and intraoperative bleeding. Minor leakage after preoperative embolization is an inconsistent warning sign of nidus congestion. Nidus outflow after intranidal embolization appears to require a few weeks for normalization. Delay of surgery after embolization should be considered in cases of suspected congested residual nidus. The danger of major haemorrhage or arterial revascularization during this waiting period appears small.

Ruptured intracranial dissecting aneurysms: management considerations with a focus on surgical and endovascular techniques to preserve arterial continuity

BACKGROUND

The present retrospective analysis was undertaken to review an institutional experience with 13 intracranial dissecting aneurysms as source of subarachnoid haemorrhage (SAH) among a total of 585 ruptured intracranial aneurysms.

METHODS AND RESULTS

In 6 patients the vertebral artery (VA) was affected, in 2 patients the basilar artery (BA), in 3 the internal carotid (ICA), in 1 the middle cerebral (MCA) and in 1 the postcommunicating (A2) segment of the anterior cerebral artery (ACA). Maintaining arterial patency was aimed at in all patients. Tangential clipping or circumferential wrapping were used as surgical methods. Endovascular stenting and/or coiling was applied in 2 instances. Four of the 6 VA dissecting aneurysms underwent surgical exploration between 1 and 22 days after haemorrhage. Two patients were in WFNS grade V and died subsequently with the aneurysms untreated, one after rehaemorrhage. In the patients with secured VA aneurysms the postoperative course was uncomplicated with the exception of additional caudal cranial nerve injury in 1 instance. Both BA aneurysms were initially treated by endovascular methods. In the first patient incomplete packing with Gugliemi detachable (GDC) coils was achieved. Follow-up angiography 6 months later showed growth and coil compaction and subsequent wrapping with Teflon fibres resulting in angiographic stabilization. The other BA aneurysm was treated by a combination of a coronary stent and GDC coils. The 3 dissecting ICA aneurysms were all explored surgically. In only 1 instance ICA continuity could be preserved by wrapping, in the other 2 cases a major portion of the vessel wall disintegrated upon removal of the surrounding clot. The only ACA dissecting aneurysm, on A2, was successfully treated with a Dacron cuff. In the single patient with a MCA aneurysm, a decision for conservative management was taken, because neither a surgical nor an endovascular solution was seen as a possibility that did not risk occlusion of lenticulostriate branches. The patient suffered a fatal rehaemorrhage 4 weeks later at her home.

CONCLUSIONS

The reported experience suggests that in Western countries also dissecting aneurysms are an occasional source of SAH. The outcome in our conservatively managed patients confirms the poor prognosis of conservative management. Wrapping and endovascular stent based methods can achieve stabilization of the dissected artery without sacrificing the artery. Results of treatment appear to depend largely on the location of the dissecting aneurysm.

Neuronavigation Based on CT Angiography for Surgery of Intracranial Aneurysms: Primary Experience with Unruptured Aneurysms

Several reports have demonstrated the use of three-dimensional (3D) computed tomographic angiography (CTA) for preoperative planning in patients with intracranial aneurysms. Until now, there are no reports on the potential role of navigation systems in combination with CTA in aneurysm surgery. In the present study we report our experience with neuronavigation based on CTA in 16 patients with unruptured anterior circulation aneurysms for 1) planning craniotomy; 2) guided approach to the aneurysm; and 3) 3D presentation of the aneurysm and adjacent arteries in correct orientation. The reconstructed CTA images were analyzed preoperatively with regard to diameter of aneurysm neck and dome as well as projection and possible daughter aneurysms, and these parameters were compared with the intraoperative findings. In addition the accuracy of the navigator to locate the aneurysm neck was measured intraoperatively. Navigated approach planning resulted in variable keyhole craniotomies for the 7 middle cerebral artery aneurysms, but did not result in deviation from small standard craniotomies for the internal carotid and anterior communicating artery aneurysms. Precision of the indication of the navigator with regard to the aneurysm neck ranged from < 1 mm to 4 mm. Intraoperative assessment confirmed the CTA data with regard to aneurysm size and projection in all, and definition of daughter aneurysms and adjacent arteries in most cases. The computer assisted approach allowed a smaller, exactly placed craniotomy primarily in MCA aneurysms. 3D presentation of the aneurysms and the adjacent arteries in correct orientation facilitated identification and dissection the aneurysms. Current navigation systems are not precise enough to allow "blind" aneurysm clipping by placing a real clip on the virtual aneurysm neck.

Neuroprotective efficacy of intra-arterial and intravenous magnesium sulfate in a rat model of transient focal cerebral ischemia

BACKGROUND

Many neurovascular procedures necessitate temporary occlusion of cerebral arteries. In this situation neuroprotective drugs may increase the safety of the procedures. Magnesium may inhibit ischemic damage by anti-excitotoxic, calcium channel blocking and vasodilatory action. Some evidence suggests that intra-arterial administration might provide a much higher degree of protection than intravenous treatment. In this study the neuroprotective efficacy of intra-arterial and intravenous magnesium administration was examined in a rat model of transient focal ischemia.

METHODS

34 male Sprague-Dawley rats were subjected to 90 minutes of middle cerebral artery occlusion (MCAO) by an intraluminal thread. Before ischemia, animals received an infusion of either (1) vehicle (0.9% NaCl) (2) MgSO4 intra-arterially or (3) MgSO4 intravenously. Local cortical blood flow (LCBF) was continuously measured by laser-Doppler flowmetry. Functional deficits were quantified daily, infarct volumes were assessed histologically after 7 days.

FINDINGS

There was no difference between the treatment groups concerning LCBF. Magnesium serum levels increased from approximately 1 mmol/l to approximately 1.8 mmol/l by either route of administration. Both intra-arterial and intravenous treatment improved neurological recovery and equally reduced total infarct volume by approximately 25%.

INTERPRETATION

The results indicate that there is no advantage of intra-arterial over intravenous magnesium administration. A comparison with previous studies suggests that even within the normal range of serum magnesium concentrations, low-normal levels may be hazardous and high-normal levels may be protective in transient focal ischemia.

Therapeutical efficacy of a novel non-peptide bradykinin B2 receptor antagonist on brain edema formation and ischemic tissue damage in focal cerebral ischemia

OBJECTIVE

Bradykinin has been identified as a mediator of secondary brain damage in acute insults. We currently studied neuroprotective properties of a bradykinin B2 receptor antagonist (LF16-0687 Ms) in transitory focal cerebral ischemia to assess infarct formation and the development of brain edema.

MATERIAL AND METHODS

55 Rats were subjected to 90 min of MCA-occlusion. The receptor antagonist was administered at two dose levels, given from 30 min prior to ischemia over two days after ischemia. Ischemic tissue damage was quantified at day 7 after MCA-occlusion together with assessment of brain edema in separate experiments. Neurological recovery was studied daily.

RESULTS

Animals receiving treatment (low dose) had a better functional recovery, particularly at days 3 and 4 (P < 0.05). Infarct formation was significantly attenuated in these animals in both total and cortical brain tissue by 50, or 80%, respectively. Postischemic brain swelling was significantly lowered, i.e. by 62%.

CONCLUSIONS

Our findings provide further support for a mediator role of bradykinin in ischemic brain damage including edema formation, obviously by ligand binding to the bradykinin B2 receptor. The availability of a receptor antagonist may afford opportunity for translation of this experimental treatment into stroke patients.

Effects of LF 16-0687 Ms, a bradykinin B(2) receptor antagonist, on brain edema formation and tissue damage in a rat model of temporary focal cerebral ischemia

Bradykinin, an endogenous nonapeptide produced by activation of the kallikrein-kinin system, promotes neuronal tissue damage as well as disturbances in blood-brain barrier function through activation of B(2) receptors. LF 16-0687 Ms, a non-peptide competitive bradykinin B(2) receptor antagonist, was recently found to decrease brain swelling in various models of traumatic brain injury. We have investigated the influence of LF 16-0687 Ms on the edema formation, neurological outcome, and infarct size in temporary focal cerebral ischemia in rats. Sprague-Dawley rats were subjected to MCA occlusion for 90 min by an intraluminal filament. Local CBF was bilaterally recorded by laser Doppler flowmetry. Study I: animals were assigned to one of three treatment arms (n=11 each): (a) vehicle, (b) LF 16-0687 Ms (12.0 mg/kg per day), or (c) LF 16-0687 Ms (36.0 mg/kg per day) given repetitively s.c. over 3 days. The neurological recovery was examined daily. The infarct volume was assessed histologically 7 days after ischemia. Study II: brain swelling and bilateral hemispheric water content were determined at 48 h post ischemia in eight rats, subjected to the low dose regimen as described above, and in eight vehicle-treated control animals. All treated animals showed tendency to exhibit improved neurological recovery throughout the observation period as compared to the vehicle-treated controls, while this improvement was only significant within the low dose group from postischemic days 3 to 4. Low dose LF 16-0687 Ms significantly attenuated the total and cortical infarct volume by 50 and 80%, respectively. Furthermore, postischemic swelling (-62%) and increase in water content of the infarcted brain hemisphere (-60.5%) was significantly inhibited. The present findings provide strong evidence for an involvement of bradykinin-mediated secondary brain damage following from focal cerebral ischemia. Accordingly, specific inhibition of bradykinin B(2) receptors by LF 16-0687 Ms attenuated postischemic brain swelling, improved the functional neurological recovery, and limited ischemic tissue damage, raising its potential for clinical evaluation in patients with acute stroke.

Anesthetic methods in rats determine outcome after experimental focal cerebral ischemia: mechanical ventilation is required to obtain controlled experimental conditions

OBJECTIVE

Anesthetic agents, pH, blood gases and blood pressure have all been found to influence the pathophysiology of experimental stroke. In experimental research, rats are predominantly used to investigate the effects of focal cerebral ischemia. Chloral hydrate, applied intraperitoneally (i.p.), and halothane, applied via face-mask in spontaneously breathing animals or via endotracheal tube in mechanically ventilated animals are popular methods of anesthesia. We investigated the potential of these anesthetic methods to maintain physiologic conditions during focal cerebral ischemia and their influence on postischemic mortality and histological outcome.

METHODS

Thirty male Sprague-Dawley rats were subjected to 90 min of middle cerebral artery occlusion by insertion of an intraluminal thread and assigned to one of three groups (n=10 each): (A) chloral hydrate i.p./spontaneously breathing; (B) halothane in 70:30 (%) N2O/O2 via face-mask/spontaneously breathing; and (C) halothane in 70:30 (%) N2O/O2 via endotracheal tube/mechanically ventilated. Physiologic parameters were measured before, during, and after ischemia. Infarct volume was histologically assessed after 7 days.

RESULTS

All anesthetic techniques except mechanical ventilation via an endotracheal tube resulted in considerably fluctuating blood gases levels, hypercapnia, acidosis and low blood pressure. All spontaneously breathing animals (groups A and B) exhibited a higher postischemic mortality and significantly larger infarct volumes than group C with intubated and ventilated animals.

CONCLUSIONS

Intra- and postischemic physiologic parameters such as blood pressure, pH, and blood gases critically determine outcome after focal cerebral ischemia. Although anesthesia by halothane via face-mask allowed better control of depth of anesthesia than chloral hydrate, we have found this method to be unsatisfactory due to insufficient control of ventilation and waste of anesthetic gases. Experiments with rats requiring normal physiologic parameters should be performed under conditions of controlled mechanical ventilation and sufficient analgesia.

[Proper diagnosis and treatment of carotid stenoses. Recommending surgery, when is it too risky?]

A number of multicentric randomized studies have been able to demonstrate a benefit from surgery in high-grade asymptomatic and symptomatic carotid artery stenosis. The benefits of carotid artery endarterectomy are greater in symptomatic than in asymptomatic patients. This means that, in the case of the latter, the benefits and risks of surgery must be considered with special care. The gold standard of the preoperative diagnostic work-up is selective angiography. Since this examination modality is associated with a complication rate of > 1% in this group of patients, there is an increasing tendency to content oneself with such noninvasive procedures as duplex sonography used in combination with cranial and cervical MRI. The life expectancy of patients undergoing carotid artery end-arterectomy is determined mainly by their concomitant cardiac problems. Constant surveillance and optimal treatment of vascular risk factors is therefore essential in these patients.

Thalamic astrocytomas: surgical anatomy and results of a pilot series using maximum microsurgical removal

Deep-seated astrocytomas within the basal ganglia and the thalamus are considered unfavourable for microsurgical removal since the circumferential neighbourhood of critical structures limits radical resection. On closer assessment, the thalamus has a unique configuration within the basal ganglia. Its tetrahedric shape has 3 free surfaces and only the ventrolateral border is in contact with vital and critical functional structures, e.g. the subthalamic nuclei and the internal capsule. The purpose of the present study was to investigate the feasibility of maximum microsurgical removal in a series of intrinsic thalamic astrocytomas. 14 patients with intrathalamic astrocytomas grades I to 4 as diagnosed by previous stereotactic biopsy or intra-operative frozen section were selected for maximum microsurgical removal. The infratentorial supracerebellar approach from the contralateral side was used for 4 limited neoplasms of the pulvinar. For the other 10 larger and more extensive processes a parieto-occipital transventricular approach was chosen. Final histology gave the result of astrocytoma grade 1 or 2 in 4 patients, and of astrocytoma grade 3 or 4 in 10 patients. Postoperative MRI confirmed reduction of the tumor mass by 80 to 100% in 11 of 14 cases. Regional ancillary radiotherapy with 60 Gy was administered postoperatively for astrocytomas grades 3 and 4. Two patients operated on via the posterior transventricular approach had new postoperative partial hemianopia. Five of the 14 patients finally needed a ventriculo-peritoneal shunt. During the follow-up time of 6 to 52 months, tumor progression/recurrence was observed in 6 of the 10 high grade and none of the low grade neoplasms. The present pilot series demonstrates the feasibility of the microsurgical concept. Comparison with other treatment modalities, such as brachytherapy, requires future consideration.

Reconstructive surgery of the extracranial arteries

The first carotid endarterectomy (CEA) is usually accredited to Eastcott who reported in 1954 the successful incision of a diseased carotid bulb with end-to-end anastomosis of the internal carotid artery (ICA) to the common carotid artery (CCA). During the following years surgeons were quick to adopt and improve the intuitively attractive procedure. But by the early to mid 1980s several leading neurologists began to question the growing number of CEAs performed at that time. Six major CEA trials were then designed which are now completed or nearing completion. Most conclusive data are available from the North American Symptomatic Carotid Endarterectomy Trial (NASCET) for symptomatic carotid disease, and from the Asymptomatic Carotid Atherosclerosis Study (ACAS) for asymptomatic carotid disease. The key result of these studies is that CEA is beneficial to high grade symptomatic and asymptomatic carotid stenosis. While the benefit in symptomatic disease is clear, it may be negligible in asymptomatic patients suffering from other medical conditions, the most important being coronary artery disease. Since the conclusions from the different studies vary significantly, guidelines and recommendations with regard to CEA have been issued by a number of interest groups, so-called consensus conferences. The best known guidelines are published by the American Heart Association (AHA). However, the practice of interest groups to issue guidelines is currently being criticized, the main reason being that interest groups have different ideas and all claim the right to issue guidelines. At present we recommend CEA for symptomatic high-grade stenosis in patients without significant coincident disease. With regard to asymptomatic stenosis we suggest surgery to otherwise healthy patients if the stenosis is very narrow or progressive. Preoperative evaluation has changed over the years. Currently we recommend duplex sonography in combination with intra- and extracranial magnetic resonance angiography (MRA). Concurrent coronary artery disease is a major consideration in the perioperative management, and the use of a specific algorithm is recommended. Surgery is performed under general anaesthesia with intraoperative monitoring such as electroencephalography (EEG) and transcranial Doppler (TCD). A temporary intraluminal shunt is used selectively if after cross-clamping the flow velocity in the middle cerebral artery (MCA) falls to below 30 to 40% of baseline. For years we employed routine barbiturate neuroprotection during cross-clamping. At the present time we use barbiturate selectively, if the flow velocity in the MCA falls to below 30 to 40% of baseline and if the use of a temporary intraluminal shunt is not possible due to difficult anatomic conditions. The reason to abandon systematic barbiturate protection was to accelerate recovery from anaesthesia. Our patients are monitored overnight on the ICU or a surveillance unit. Routine hospitalization after surgery is 5 to 7 days with a control duplex sonography being performed prior to discharge. A number of details with regard to surgical technique and perioperative management are a matter of discussion. Our surgical routine is described here step by step. Such management resulted in 6 major complications among the 402 cases with 4 of cardiopulmonary and 2 of cerebrovascular origin. For the future we can expect the development of percutaneous transluminal techniques competing with standard carotid endarterectomy. At the present time several comparative studies are under way. Irrespective of the technical approach to treat carotid stenosis, several other issues have to be clarified before long. One of the major unresolved items is the timing of treatment after completed stroke. In this regard prospective trials need to be performed. Although numerically not as important as carotid stenosis, vertebral artery (VA) and subclavian artery (SA) stenoses are more and more accepted as indication for surgical

Transorbital keyhole approach to anterior communicating artery aneurysms

OBJECTIVE

The transorbital keyhole approach to anterior communicating artery aneurysms was developed as a minimally invasive method for safe control of the anterior communicating artery complex. This approach does not necessitate resection of the gyrus rectus.

METHODS

The technique is described in detail. The transorbital keyhole approach provides more ventral access than the supraorbital approaches, and the anterior communicating artery complex can be controlled by splitting the basal aspect of the interhemispheric fissure.

RESULTS

Since late 1998, the authors have used the transorbital keyhole approach routinely. During the initial experience with 33 patients, the only observed complication specific to this approach was transient diplopia in one patient. At follow-up examinations 2 to 15 months after surgery, the cosmetic results were favorable as compared with those of standard pterional craniotomy.

CONCLUSION

We have designed a small, custom-tailored approach to the anterior communicating artery complex for routine use. The small orbitocranial approach is a step toward the ideal of purely extra-axial safe control of anterior communicating artery aneurysms. The orbitocranial keyhole approach seems to be substantially better than the craniotomy, although it requires additional effort and time.

No additional neuroprotection provided by barbiturate-induced burst suppression under mild hypothermic conditions in rats subjected to reversible focal ischemia

OBJECT

Mild-to-moderate hypothermia is increasingly used for neuroprotection in humans. However, it is unknown whether administration of barbiturate medications in burst-suppressive doses-the gold standard of neuroprotection during neurovascular procedures-provides an additional protective effect under hypothermic conditions. The authors conducted the present study to answer this question.

METHODS

Thirty-two Sprague-Dawley rats were subjected to 90 minutes of middle cerebral artery occlusion and randomly assigned to one of four treatment groups: 1) normothermic controls; 2) methohexital treatment (burst suppression); 3) induction of mild hypothermia (33 degrees C); and 4) induction of mild hypothermia plus methohexital treatment (burst suppression). Local cerebral blood flow was continuously monitored using bilateral laser Doppler flowmetry and electroencephalography. Functional deficits were quantified and recorded during daily neurological examinations. Infarct volumes were assessed histologically after 7 days. Methohexital treatment, mild hypothermia, and mild hypothermia plus methohexital treatment reduced infarct volumes by 32%, 71%, and 66%, respectively, compared with normothermic controls. Furthermore, mild hypothermia therapy provided the best functional outcome, which was not improved by additional barbiturate therapy.

CONCLUSIONS

The results of this study indicate that barbiturate-induced burst suppression is not required to achieve maximum neuroprotection under mild hypothermic conditions. The magnitude of protection afforded by barbiturates alone appears to be modest compared with that provided by mild hypothermia.

[Therapy of subarachnoid hemorrhage. First aid already on site!]

The age peak for spontaneous subarachnoidal bleeding from an aneurysm is 55-60 years, and two-thirds of the cases are women. The prognosis continues to be poor (50% early mortality rate). Early admission to a neurosurgical department/institution may be life-saving. Already in the out-of-hospital situation, lowering of the frequently elevated blood pressure needs to be achieved (e.g. with Adalat (nifedipine) 10 mg, sublingual). Depending on the stage presenting, either early surgery is indicated, or elective surgery when the patient has been stabilized. Here, two different schools of thought continue to exist. A new method is endovascular coiling involving the microcatheter placement of tiny platinum spirals in the aneurysm to effect local thrombosis. As a prophylactic measure, vasospasm may be prevented by the administration of Nimotop (nimodipine). But its treatment continues to be problematic.

Neurological impairment in rats after transient middle cerebral artery occlusion: a comparative study under various treatment paradigms

The assessment of the functional outcome - in addition to the conventional endpoints as histomorphometry of the ischemic brain damage - for the evaluation of cerebroprotective therapies is increasingly recommended, although there is little consensus on appropriate procedures. We evaluated a battery of sensorimotor tasks in rats after transient middle cerebral artery occlusion (MCAO) to select those with the highest potential to discriminate between various degrees of neuronal damage. A total of 40 Sprague-Dawley rats were subjected to 90 min of MCAO and assigned to one of four treatment arms: (1) sham-operated controls, (2) vehicle-treated controls, (3) moderately effective neuroprotection by 2x100 mg/kg alpha-phenyl-N-tert-butyl nitrone (PBN), (4) highly effective neuroprotection by mild hypothermia (33 degrees C). Functional deficits were daily quantified using the beam balance task (1.5 cm, 2.5 cm diameter rectangular and 2.5 cm diameter cylindrical beam), the prehensile traction task, the rotarod, and a six-point neuro-score. Infarction of cerebral cortex and basal ganglia was assessed one week after ischemia. Treatment with PBN significantly reduced cortical infarction (-31%), while treatment with hypothermia resulted in a significantly smaller infarct volume of cortex (-94%) and basal ganglia (-27%). Beam balance, prehensile traction and rotarod failed to demonstrate any difference in motor performance. The six-point neuro-score showed a significant correlation with cortical infarction from day 2 and with total infarct volume from day 3. The smaller the reduction of infarct volume, the later the corresponding difference in neuro-score became apparent. Functional outcome after MCAO in rats can be assessed by a relatively simple measurement of neurological deficit. The slope of functional recovery is closely related with the degree of the morphological, particularly cortical damage. If expected treatment effects are small, an observation period of at least 3 days should be planned for the study design. The functional impairment from focal brain ischemia and its subsequent recovery could provide valuable information for future studies evaluating the neuroprotective potential of novel agents and procedures.

Neuroprotective effects of the novel brain-penetrating antioxidant U-101033E and the spin-trapping agent alpha-phenyl-N-tert-butyl nitrone (PBN)

Literature on the therapeutic efficacy of free radical scavengers suggests that drugs that are able to cross the blood-brain barrier are more effective in protecting the brain from ischemic damage. However, the exact mechanisms by which brain-penetrating antioxidants act have yet not been delineated. We compared the neuroprotective potential of the newly discovered pyrrolopyrimidine U-101033E with that of alpha-phenyl-N-tert-butyl nitrone (PBN) and investigated their influence on cerebral blood flow. Thirty male Sprague-Dawley rats were subjected to 90 min of middle cerebral artery (MCA) occlusion by an intraluminal filament. Local cerebral blood flow (LCBF) was bilaterally recorded by laser Doppler flowmetry. Neurological deficits were quantified daily. Infarct volume was assessed after 7 days. MCA occlusion reduced ipsilateral LCBF to 20-30% of baseline. After reperfusion, postischemic hyperemia was followed by a decrease in LCBF to about 70% of baseline. There was no difference in LCBF among groups. U-101033E improved neurological function and reduced infarct volume by 52% (P < 0.05). Improvement of neurological function and reduction of infarct volume (-25%) in animals treated with PBN was not significant. We conclude that U-101033E has superior neuroprotective properties compared with PBN. Neither drug improves blood flow during ischemia and 1 h of reperfusion. The mechanisms by which these brain-penetrating antioxidants act remain to be clarified.

Combination drug therapy and mild hypothermia: a promising treatment strategy for reversible, focal cerebral ischemia

BACKGROUND AND PURPOSE

Hypothermia has been suggested to be the most potent therapeutic approach to reduce experimental ischemic brain injury identified to date, and mild hypothermia is increasingly used for neuroprotection during neurovascular surgery. We have recently demonstrated that combined administration of tirilazad mesylate and magnesium provides for an overall enhanced neuroprotective effect. The present study was designed to determine whether the efficacy of mild hypothermia (33 degrees C) can be increased by combination pharmacotherapy with tirilazad and magnesium (MgCl(2)).

METHODS

Forty Sprague-Dawley rats were subjected to transient, middle cerebral artery occlusion and were randomly assigned to 1 of 4 treatment arms (n=10 each): (1) normothermia+vehicle, (2) normothermia+tirilazad+MgCl(2), (3) hypothermia+vehicle, or (4) hypothermia+tirilazad+MgCl(2). Cortical blood flow was monitored by a bilateral laser-Doppler flowmeter, and the electroencephalogram was continuously recorded. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed after 7 days.

RESULTS

Tirilazad+MgCl(2), hypothermia, and hypothermia+tirilazad+MgCl(2) reduced total infarct volume by 56%, 63%, and 77%, respectively, relative to controls. In animals treated with both hypothermia and combination pharmacotherapy, cortical infarction was almost completely abolished (-99%), and infarct volume in the basal ganglia was significantly reduced by 55%. In addition, this treatment provided for the best electrophysiological recovery and functional outcome.

CONCLUSIONS

The neuroprotective efficacy of hypothermia can be increased by pharmacological antagonism of excitatory amino acids and free radicals by using clinically available drugs. This treatment strategy could be of great benefit when applied during temporary artery occlusion in cerebrovascular surgery.

Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter

OBJECT

The aim of this retrospective study was to compare treatment results of surgery plus whole-brain radiation therapy (WBRT) with gamma knife radiosurgery alone as the primary treatment for solitary cerebral metastases suitable for radiosurgical treatment.

METHODS

Patients who had a single circumscribed tumor that was 3.5 cm or smaller in diameter were included. Treatment results were compared between microsurgery plus WBRT (52 patients, median tumor dose 50 Gy) and radiosurgery alone (56 patients, median prescribed tumor dose 22 Gy). In case of local/distant tumor recurrence in the radiosurgery group, additional radiosurgical treatment was administered in patients with stable systemic disease. Survival time was analyzed using the Kaplan-Meier method, and prognostic factors were obtained from the Cox model. The patient groups did not differ in terms of age, gender, pretreatment Karnofsky Performance Scale (KPS) score, duration of symptoms, tumor location, histological findings, status of the primary tumor, time to metastasis, and cause of death. Patients who suffered from larger lesions underwent surgery (p < 0.01). The 1-year survival rate (median survival) was 53% (68 weeks) in the surgical group and 43% (35 weeks) in the radiosurgical group (p = 0.19). The 1-year local tumor control rates after surgery and radiosurgery were 75% and 83%, respectively (p = 0.49), and the 1-year neurological death rates in these groups were 37% and 39% (p = 0.8). Shorter overall survival time in the radiosurgery group was related to higher systemic death rates. A pretreatment KPS score of less than 70 was a predictor of unfavorable survival. Perioperative morbidity and mortality rates were 7.7% and 1.6% in the resection group, and 8.9% and 1.2% in the radiosurgery group, respectively. Four patients presented with transient radiogenic complications after radiosurgery.

CONCLUSIONS

Radiosurgery alone can result in local tumor control rates as good as those for surgery plus WBRT in selected patients. Radiosurgery should not be routinely combined with radiotherapy.

Neuroprotective efficacy of combination therapy with two different antioxidants in rats subjected to transient focal ischemia

The vascular endothelium and parenchyma of the brain have both potential pathways to generate free radicals under pathological conditions. We evaluated the neuroprotective efficacy of two different antioxidants, a microvascularly acting 21-aminosteroid (U-74389G) and a brain-penetrating pyrrolopyrimidine (U-101033E) alone and in combination. Forty Sprague-Dawley rats were randomly assigned to one of four treatment groups: (1) vehicle-treated controls, (2) U-74389G, (3) U-101033E, (4) U-74389G+U-101033E. Drugs were administered in a dosage of 3x3 mg/kg i.v. before, during, and after ischemia. All animals were subjected to 90 min of middle cerebral artery occlusion. Local cortical blood flow (LCBF) was continuously recorded by bilateral laser Doppler flowmetry. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed after 7 days. There were no significant differences in LCBF among groups. U-101033E improved neurological function from postoperative day 4 to 7, while U-74389G did not improve neurological recovery. Animals treated with both drugs showed significantly less deficits from postoperative day 1 to 7. U-101033E and combination therapy reduced total infarct volume by 53% and 54% (P<0.05). U-74389G non-significantly reduced total infarct volume by 25%. Cortical infarct volume was significantly reduced in all treatment groups but only U-101033E and combination therapy protected the basal ganglia from infarction. In conclusion, brain-penetrating antioxidants have superior neuroprotective properties compared to microvascularly acting agents. Combination therapy, affording antioxidation plus radical scavenging in blood vessels and brain parenchyma, might yield the highest degree of neuronal protection from peroxidative damage. The neuroprotective efficacy seems to be independent of CBF.

Neuroprotective effects of combination therapy with tirilazad and magnesium in rats subjected to reversible focal cerebral ischemia

OBJECTIVE

Cell death after cerebral ischemia is mediated by release of excitatory amino acids, calcium influx into cells, and generation of free radicals. We examined the hypothesis that concurrent administration of tirilazad, a well-known antioxidant, and magnesium, an antagonist of calcium and excitatory amino acids, would result in a synergistic neuroprotective effect.

METHODS

Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion and assigned to one of four treatment arms (n = 10 in each): 1) vehicle, 2) tirilazad, 3) MgCl2, or 4) tirilazad and MgCl2. Cortical blood flow was recorded using laser Doppler flowmetry. Functional deficits were quantified by performing daily neurological examinations. Infarct volume was assessed after 7 days.

RESULTS

There was no difference in cortical blood flow among groups. Animals that received tirilazad or MgCl2 monotherapy had significantly better neurological function compared with control animals only on postoperative Days 3 and 4, whereas animals treated with both drugs had significantly better neurological function than did control animals from postoperative Days 2 through 7. Magnesium reduced total infarct volume by 25% (nonsignificant), tirilazad by 48% (P<0.05), and combination therapy by 59% (P<0.05) compared with control data.

CONCLUSION

Combined therapy with antagonists of excitatory amino acids and free radicals provides better neuroprotection from the effects of transient focal ischemia than does therapy with either antagonist alone. In contrast to many experimental agents, tirilazad and magnesium offer the advantage of being licensed for clinical use. This drug combination could be of great benefit when administered before temporary artery occlusion in patients undergoing cerebrovascular surgery.

EEG burst suppression is not necessary for maximum barbiturate protection in transient focal cerebral ischemia in the rat

Barbiturates have been demonstrated to reduce the cerebral metabolic rate (CMR) in a dose-dependent manner but investigations of a dose-response relationship for their neuroprotective efficacy are scant. It has been suggested that barbiturates possess other mechanism of action that may be critical to their protective effect. If so, it is conceivable that the peak effect of such mechanisms does not parallel the reduction in CMR. Thus, maximal neuroprotection may be achieved with a substantially lower dose of the drug. Thirty Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion while either anesthetized with (1) halothane (control) or (2) intravenous thiopental titrated to cause mild EEG suppression or (3) thiopental titrated to maintain EEG burst suppression. Cortical blood flow was recorded by continuous bilateral laser Doppler flowmetry (LDF). Infarct volume was assessed after 3 h of reperfusion. Low-dose thiopental decreased blood flow to 80% of baseline and high-dose thiopental to 70% of baseline. LDF did not indicate improvement of blood flow by thiopental in the ischemic area. Compared to controls, low-dose thiopental significantly decreased infarct volume by 28% and high-dose thiopental by 29%. The results of this study and a review of literature indicate that barbiturates provide cerebral protection but that the magnitude of this effect has been overestimated. Other mechanisms than CMR reduction seem to contribute to their beneficial effects, and high doses administered to the point of burst suppression may not be required to obtain maximal protection.

A critical reevaluation of the intraluminal thread model of focal cerebral ischemia: evidence of inadvertent premature reperfusion and subarachnoid hemorrhage in rats by laser-Doppler flowmetry

BACKGROUND AND PURPOSE

The intraluminal thread model for middle cerebral artery occlusion (MCAO) has gained increasing acceptance. Numerous modifications have been reported in the literature, indicating that the technique has not been standardized. The present study was performed to evaluate and optimize the reliability of this model.

METHODS

One hundred Sprague-Dawley rats were subjected to MCAO by 2 different intraluminal filaments. Cortical blood flow was continuously monitored over both hemispheres by laser-Doppler flowmetry (LDF). In part I (3-0 filament), we evaluated the incidence of adequate MCAO, subarachnoid hemorrhage (SAH), intraluminal thrombus formation, and the effects of heparinization. In part II (silicone-coated 4-0 filament), we also determined the influence of insufficient MCAO on morphological and functional outcome and the incidence of postischemic hyperthermia.

RESULTS

In part I, SAH occurred in 30% and premature reperfusion in 24%. All animals with a decrease in contralateral flow had suffered SAH. Thrombus formation was not observed in any group. In part II, SAH occurred in 8% and premature reperfusion in 26%. There was no difference in outcome between rats with primary MCAO and rats with filament correction. Animals with uncorrected premature reperfusion had significantly smaller infarct volumes and fewer neurological deficits.

CONCLUSIONS

SAH and insufficient MCAO may be more common in the intraluminal thread model than previously reported. Inadvertent premature reperfusion contributes to the interanimal variability associated with this model. The incidence of valid experiments increases with the use of a silicone-coated 4-0 filament. Continuous bilateral LDF is indispensable to monitor adequate MCAO and is highly sensitive to recognize SAH.

Monotherapy with dextromethorphan or tirilazad--but not a combination of both--improves outcome after transient focal cerebral ischemia in rats

Cell death after cerebral ischemia is mediated by a massive release of excitatory amino acids, generation of free radicals, and - a crucial step - calcium influx into cells. We examined the hypothesis that concurrent administration of drugs ameliorating brain damage via different mechanisms would result in a synergistic neuroprotective effect. The neuroprotective efficacy of two clinically available drugs - the N-methyl-D-aspartate and calcium-channel antagonist dextromethorphan (DM) and the antioxidant tirilazad - were studied in monotherapy and in combination in a rat model of transient focal ischemia. Male Sprague-Dawley rats were subjected to 90 min of middle-cerebral-artery occlusion by an intraluminal filament technique. The animals were randomly assigned to one of four treatments (n=10 each): (1) vehicle-treated controls, (2) DM, (3) tirilazad, (4) DM+tirilazad. Drugs or vehicles were administered 15 min before ischemia and at reperfusion. Local cerebral blood flow (LCBF) was bilaterally recorded by continuous laser Doppler flowmetry. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed planimetrically after 7 days. DM prevented post-ischemic hypoperfusion. Tirilazad did not influence LCBF. Monotherapy with DM or tirilazad improved neurological function and reduced infarct volume by 45% and 48%, respectively. Combination therapy failed to influence neurological recovery and infarct volume. Although, from pharmacological point of view, a synergistic neuroprotective effect is expected, combination of dextromethorphan and tirilazad may lead to mutual inhibition or potentiate adverse effects.

Neuroprotective properties of a novel antioxidant (U-101033E) with improved blood-brain barrier permeability in focal cerebral ischemia

Many efforts have been undertaken to develop antioxidants against free radical induced brain damage, 21-aminosteroids, although accumulating in the cell membrane, thus protecting vascular endothelium from peroxidative damage hardly penetrate the blood-brain barrier. A novel group of antioxidants, the pyrrolopyrimidines, has a markedly improved ability to enter the brain parenchyma. In our current study the neuroprotective potential of the 21-aminosteroid U-74389G was compared with that of the pyrrolopyrimidine U-101033E in a rat model of reversible focal cerebral ischemia. Sprague-Dawley rats were subjected to unilateral occlusion of the middle cerebral artery with assignment to one of three treatment arms (n = 10 each), receiving either vehicle, U-74389G, or U-101033E. Regional CBF was recorded bilaterally by laser Doppler flowmetry. In addition, neurological examination was performed daily, with assessment of infarct volume at day seven. U-101033E reduced the infarct volume significantly by 51%, whereas U-74389G afforded non-significant attenuation only. U-101033E was found to improve neurological recovery promptly; animals with U-74389G began to recover only at the end of the experimental observation period. Differences in the regional CBF were not found in the contralateral hemispheres for either treatment group. We conclude that antioxidative compounds which cross the blood-brain barrier are more effective in focal cerebral ischemia than agents which predominantly act on the endothelium of cerebral microvessels.

Radical resection of meningiomas and arteriovenous fistulas involving critical dural sinus segments: experience with intraoperative sinus pressure monitoring and elective sinus reconstruction in 10 patients

OBJECTIVE

Radical resection of meningiomas and dural arteriovenous fistulas involving functional major dural sinuses entails the risk of intracranial hypertension and venous infarction. Surgical reconstruction of dural sinuses and bridging veins increases the spectrum of dural sinus conditions that can be treated by complete resection, but indications for venous reconstructions and associated risks are still not well defined. We report our experience with sinus reconstruction based on the intraoperative assessment of collateral venous flow.

METHODS

Radical resection of meningiomas (n = 5) or dural arteriovenous fistulas (n = 5) involving critical segments of dural sinuses was performed in 10 patients. All but two patients were suffering from recurrent disease after incomplete treatment. Tolerance of sinus occlusion was assessed intraoperatively by measuring stump pressure in the superior sagittal sinus during test clamping of the involved sinus segment.

RESULTS

In five patients, the results of pressure monitoring suggested that occlusion of the sinus might not be tolerated. In two other patients, major bridging veins entered the diseased segment. In these patients, the resected sinus segment was reconstructed and bridging veins were reinserted as far as possible. Postoperative graft occlusion occurred in two patients. One patient who was managed without reconstruction sustained a transient postoperative neurological deficit resulting from venous congestion in the vein of Labbé. Postoperative imaging confirmed total elimination of the pathological process in all 10 patients. There was no recurrence of disease during follow-up periods of up to 8 years.

CONCLUSION

The monitoring of sinus pressure, together with the possible reconstruction of the diseased sinus, allows complete surgical treatment of dural sinus abnormalities and involves acceptable risk.

Superior neuroprotective efficacy of a novel antioxidant (U-101033E) with improved blood-brain barrier permeability in focal cerebral ischemia

BACKGROUND AND PURPOSE

The vascular endothelium and parenchyma of the brain have the potential to generate free radicals under pathological conditions, but it is unclear which of these two sites prevails in the production of free radicals and should be the primary target of therapeutic intervention. To clarify this issue, we compared the neuroprotective properties of a 21-aminosteroid (U-74389G) that acts on the microvasculature and a pyrrolopyrimidine (U-101033E), a novel antioxidant compound that has significantly improved potential to enter the brain parenchyma.

METHODS

In Sprague-Dawley rats the middle cerebral artery was occluded for 90 minutes by an intraluminal filament. Local cortical blood flow was recorded by bilateral laser Doppler flowmetry throughout ischemia and 1 hour of reperfusion. Three groups of rats were studied: controls that received vehicle only and animals that received either U-74389G or U-101033E. Neurological examinations were performed daily, and infarct size was assessed histologically 7 days after ischemia.

RESULTS

U-101033E reduced infarct volume significantly by 51%, whereas U-74389G led to a nonsignificant decrease in infarct volume. U-101033E improved neurological function immediately after ischemia, whereas U-74389G led to improvement only at the end of the observation period. Laser Doppler measurements showed no significant difference in local cortical blood flow among the treatment groups.

CONCLUSIONS

We conclude that for treatment of transient focal ischemia, an antioxidant that crosses the blood-brain barrier might be superior to agents that predominantly act on the endothelium of the cerebral microvasculature.