Factors predictive of obliteration after arteriovenous malformation radiosurgery.

OBJECTIVE: To investigate predictive factors of complete obliteration following treatment with linac-based stereotactic radiosurgery for intracerebral arteriovenous malformations. METHODS: Archived plans for 48 patients treated at the British Columbia Cancer Agency and who underwent post-treatment digital subtraction angiography to assess obliteration were studied. Actuarial estimates of obliteration were calculated using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazards models were used for analysis of incidence of obliteration. Log-rank test was used to search for parameters associated with obliteration. RESULTS: Complete nidus obliteration was achieved in 38/48 patients (79.2%). Actuarial rate of obliteration was 75.9% at 4 years (95% confidence interval 63.1%-88.6%). On univariate analysis, prescribed dose to the margin (p=0.002) and dose to isocentre (p=0.022) showed statistical significance. No parameters were significant in a multivariate model. According to the log-rank test, prescribed dose to the margin of >20 Gy (p=0.004) and dose to the isocentre of >25 Gy (p=0.004) were associated with obliteration. CONCLUSION: Reported series in the literature suggest a number of different factors are predictive of complete obliteration of arteriovenous malformations following radiosurgery. However, differing definitions of volume and complete obliteration makes direct comparison between series difficult. This study demonstrates that complete obliteration of the nidus following linear accelerator-based stereotactic radiosurgery for arteriovenous malformations appears to be most closely related to the prescribed marginal dose. In particular, a marginal dose of >20 Gy is strongly associated with obtaining complete obliteration of the nidus.

Treatment of traumatic aneurysms and arteriovenous fistulas of the skull base by using endovascular stents.

OBJECT: The authors describe their preliminary clinical experience with the use of endovascular stents in the treatment of traumatic vascular lesions of the skull base region. Because adequate distal exposure and direct surgical repair of these lesions are not often possible, conventional treatment has been deliberate arterial occlusion. The purpose of this report is to demonstrate the safety and efficacy as well as limitations of endovascular stent placement in the management of craniocervical arterial injuries. METHODS: Six patients with vascular injuries were treated using endovascular stents. There were two arteriovenous fistulas and two pseudoaneurysms of the distal extracranial internal carotid or vertebral arteries resulting from penetrating trauma, and two petrous carotid pseudoaneurysms associated with basal skull fractures. In one patient a porous stent placement procedure was undertaken as well as coil occlusion of an aneurysm, whereas in the remaining five patients covered stent grafts were used as definitive treatment. There were no procedural complications. One patient in whom there was extensive traumatic arterial dissection was found to have asymptomatic stent thrombosis when angiography was repeated 1 week postoperatively. This was the only patient whose associated injuries precluded routine antithrombotic or antiplatelet therapy. Follow-up examinations in the remaining five patients included standard angiography (four patients) or computerized tomography angiography (one patient), which were performed 3 to 6 months postoperatively, and clinical assessments ranging from 3 months to 1 year in duration (mean 9 months). In all five cases the vascular injury was successfully treated and the parent artery remained widely patent. No patient experienced aneurysm recurrence or hemorrhage, and there were no thromboembolic complications. CONCLUSIONS: The authors' experience demonstrates that endovascular treatment of traumatic vascular lesions of the skull base region is both feasible and safe. The advantages of minimally invasive stent placement and parent artery preservation make this procedure for repair of neurovascular injuries a potentially important addition to existing methods.

Importance of the over the wire occlusion balloon catheter designed for intracranial use. Two illustrative cases.

SUMMARY: The over the wire occlusion balloon catheter is a new interventional neuroradiology tool. We present two cases where this system was crucial for the management. In the first case it allowed us to perform an occlusion test before closing in safe conditions a M2 fusiform aneurysm. In the second case, it allowed us to control a subarachnoid bleeding after endovascular perforation of a normal left P1 segment. We believe that all interventional neuroradiologists should be familiar and comfortable with the systems available.

Subarachnoid hemorrhage from vertebrobasilar dissecting aneurysm treated with staged bilateral vertebral artery occlusion: the importance of early follow-up angiography: technical case report.

OBJECTIVE AND IMPORTANCE: Vertebrobasilar dissecting aneurysms are an uncommon but increasingly recognized cause of subarachnoid hemorrhage (SAH). We describe a patient with SAH caused by a dissecting aneurysm involving both vertebral arteries as well as the basilar trunk. The patient was treated successfully with proximal occlusion of the vertebral arteries using endovascular balloon occlusion in two stages. The importance of early follow-up angiography to document progression or resolution of untreated dissections is emphasized. This approach is suggested as definitive treatment for vertebrobasilar dissection in appropriate circumstances. CLINICAL PRESENTATION: A 41-year-old man presented with SAH from spontaneous vertebrobasilar dissection. Angiography revealed aneurysmal dilation of the right vertebral artery and basilar trunk and occlusion of the left vertebral artery. INTERVENTION: The dissecting aneurysm was treated with balloon occlusion of the right vertebral artery. Repeat angiography 2 weeks later demonstrated resolution of the left vertebral occlusion, with restoration of antegrade flow in the basilar trunk and increased filling of the right vertebral and basilar dissecting aneurysms. Balloon occlusion of the left vertebral artery led to aneurysm thrombosis and excellent clinical outcome. CONCLUSION: Bilateral vertebrobasilar dissecting aneurysms are an uncommon cause of SAH. If unilateral proximal vertebral artery occlusion is chosen as the initial treatment, it is essential to document the status of the contralateral vessel using follow-up angiography. Staged bilateral vertebral artery occlusion should be considered in the event of recurrent or progressive aneurysm enlargement. Endovascular balloon occlusion has advantages over proximal clipping of the parent vessel: cranial nerve manipulation is avoided, test occlusion in the awake patient can be performed at the site of permanent occlusion, and therapeutic levels of anticoagulation can be maintained throughout and after the procedure, thus diminishing the likelihood of thromboembolic complications.

Endovascular occlusion of basilar bifurcation aneurysms with electrolytically detachable coils.

OBJECT: To describe the clinical and angiographic results of endovascular occlusion of basilar bifurcation aneurysms with electrolytically detachable coils, and to identify factors which should be considered in deciding upon surgical or endovascular treatment. METHODS: We report our experience with 40 patients in whom occlusion of basilar bifurcation aneurysms with electrolytically detachable coils was attempted. All patients underwent superselective angiography and attempted embolization with Guglielmi detachable coils (GDCs). Angiographic and clinical results were prospectively recorded. Twenty-eight aneurysms presented with subarachnoid hemorrhage (SAH), 2 were symptomatic and 10 were incidental. RESULTS: Coils were not placed in 10 patients (25%) because of unfavorable anatomy. Complete aneurysm occlusion was achieved at the time of the initial procedure in 13 (32.5%), small neck remnants were present in 13 (32.5%), and in 4 (10.0%) there was obvious residual contrast filling of the aneurysm body. Of 23 patients successfully coiled after SAH, 20 were Grade 1 to 3 and 3 were grade 4 or 5 at the time of treatment. Eighteen (78%) made a good recovery. Procedural mortality was 2.5% and permanent morbidity was 7.5%. There were no permanent complications in patients with unruptured aneurysms. Complete aneurysm occlusion was possible in 10 (56%) of 18 aneurysms with small necks and 3 (14%) of 22 with large necks. Follow-up angiography in 25 of 28 surviving patients (mean, 12 months) demonstrated stability of all completely occluded aneurysms. Incompletely coiled aneurysms had variable results on follow-up angiograms: 15.4% improved, 69.2% worsened, and 15.4% were stable. No aneurysm bled after treatment during clinical follow-up averaging 22 months. CONCLUSIONS: Endovascular treatment of basilar bifurcation aneurysms appears to prevent early aneurysm rebleeding with acceptable rates of morbidity and mortality, but long-term follow-up is required.

Arterial aneurysms associated with cerebral arteriovenous malformations: classification, incidence, and risk of hemorrhage.

OBJECT: The goal of this study was to develop a classification system for aneurysms associated with arteriovenous malformations (AVMs) based on their anatomical and pathophysiological relationships and to determine the incidence and bleeding rates for these aneurysms as well as the effects of AVM treatment on their natural history. METHODS: Of 632 patients with AVMs, intranidal aneurysms were found in 35 (5.5%) and flow-related aneurysms in 71 (11.2%). Patients with intranidal aneurysms presented more frequently with hemorrhage (72% compared with 40%, p < 0.001) and had a 9.8% per year risk rate of bleeding during follow-up review. Twelve (17%) of the patients with flow-related aneurysms associated with an AVM presented with hemorrhage from an aneurysm, whereas 15 (21%) bled from their AVM. Seventeen patients underwent angiography after AVM treatment (mean 2.25 years). Of 23 proximal aneurysms, 18 (78.3%) were unchanged, four (17.4%) were smaller, and one (4.3%) had disappeared, whereas four (80%) of five distal aneurysms regressed completely and one was unchanged. Sixteen patients underwent angiography after partial AVM treatment (mean 3.8 years). In cases with less than a 50% reduction in the AVM, no aneurysms regressed, although two enlarged and bled. In cases with greater than a 50% reduction in the AVM, two of three distal aneurysms disappeared and five proximal aneurysms were unchanged. CONCLUSIONS: Arterial aneurysms associated with cerebral AVMs may be classified as intranidal, flow-related, or unrelated to the AVM nidus. Intranidal aneurysms have a high correlation with hemorrhagic clinical presentation and a risk of bleeding during the follow-up period that considerably exceeds that which would be expected in their absence. Patients with flow-related aneurysms in association with an AVM may present with hemorrhage from either lesion. Aneurysms that arise on distal feeding arteries near the nidus have a high probability of regressing with substantial or curative AVM therapy.

Unusual aneurysms of the distal internal carotid artery.

BACKGROUND: Supraclinoid carotid aneurysms have traditionally been classified according to their relation to the major carotid branches, but considerable variation exists with respect to site of origin, projection, and relationship to the skull base. Distal internal carotid aneurysms with a superior or medial projection are uncommon vascular lesions, with an unusually high incidence of operative complications. METHODS: Surgical experience with five patients suffering from subarachnoid hemorrhage due to ruptured aneurysms of the dorsomedial wall of the distal internal carotid artery is presented, with emphasis on their angiographic appearance, anatomical features, and operative management. RESULTS: All five patients underwent surgical clipping. Intra-operative rupture occurred in two cases, with avulsion of the aneurysm from the internal carotid artery in both. A third patient experienced recurrent subarachnoid hemorrhage three days after uneventful surgery, due to the clip shearing off of the parent vessel. CONCLUSIONS: Distal internal carotid aneurysms do not conform to the usual principles of aneurysm formation and are unique in their dorsomedial location unrelated to an arterial bifurcation. Although their anatomy is straightforward and exposure is not restricted by bone or dural structures of the skull base, they possess extremely fragile necks which make surgical management particularly hazardous.

Management-related morbidity in unselected aneurysms of the upper basilar artery.

A series of 49 consecutively treated patients with 52 aneurysms of the upper basilar artery (BA) is presented. Thirty-nine aneurysms arose at the BA bifurcation, 11 at the origin of the superior cerebellar artery (SCA), and two from the upper BA trunk just below the SCA. The patient population consisted of 36 women and 13 men, with a mean age of 50 years (range 23-74 years). Of the 35 patients presenting with subarachnoid hemorrhage, 10 were Grade I, 10 were Grade II, 11 were Grade III, and four were Grade IV according to the Hunt and Hess scale. Treatment consisted of aneurysm neck clipping in 28, proximal occlusion of the BA in three, and endovascular therapy with coils in four patients. The remaining 14 patients with unruptured aneurysms underwent direct neck clipping. Postoperatively, 38 patients developed diplopia in at least one direction of gaze but this had resolved in 31 of them at the last follow-up evaluation. There were four deaths (8.2%): two as a result of rebleeding following coil compaction at 8 days and 9 months posttreatment, respectively; one as a result of vasospasm; and one as a result of brainstem infarction after proximal occlusion of the BA in a giant bifurcation aneurysm. Of the surviving patients, 33 (67.3%) made an excellent recovery, seven (14.3%) made a good recovery, and five (10.2%) were in poor condition at the last follow-up review. Direct microsurgical clipping of most aneurysms of the BA apex region can be performed with acceptable rates of morbidity. These data from an unselected series of patients in a general hospital provide a basis for comparison with developing alternative techniques.

Toxicity studies in thymidine kinase-deficient herpes simplex virus therapy for malignant astrocytoma.

Previous studies have shown that genetically engineered thymidine kinase (tk)-defective herpes simplex virus type 1 (HSV-1) can effectively and selectively destroy gliomas in animal models. The consequences of viral infection and tumor regression must be characterized before this therapy can be applied in human trials. To study the potential for long-term toxicity, immunocompetent rats harboring 9L gliosarcomas were injected intratumorally with a tk-defective HSV-1, KOS-SB, at titers that previously have been demonstrated to cause tumor regression. In animals surviving 3 months or longer following viral treatment, there was no evidence of persistent infection or inflammation in peritumoral brain tissue or in remote systemic organs studied with routine histological and immunocytochemical analyses. Polymerase chain reaction using primers specific for HSV-1 detected HSV-1 DNA in peritumoral tissue only in animals sacrificed within 3 months of viral injection. There was no evidence of HSV-1 DNA in systemic tissues at any time after treatment. We conclude that stereotactic intratumoral injection of tk-deficient HSV can be attempted for the treatment of brain tumors without risk of systemic infection or significant toxicity to normal brain or remote proliferating tissues.

Transfection with bFGF sense and antisense cDNA resulting in modification of malignant glioma growth.

Aberrant autocrine control by peptide growth factors is a possible mechanism by which disordered regulation of cell proliferation may occur. The authors used the C6 glioma cell line as a model to study the role of basic fibroblast growth factor (bFGF) in tumor growth by transfection with bFGF complementary deoxyribonucleic acid in both the sense and antisense orientation. Clones with high messenger ribonucleic acid expression of the sense construct have increased proliferation in cell culture and increased levels of intracellular and extracellular bFGF. Clones with high expression of the antisense construct show decreased proliferation in culture and reduced levels of immunologically detectable bFGF.

Neuropathology of intracranial arteriovenous malformations following conventional radiation therapy.

Conventional fractionated radiation therapy was used in 15 patients to treat arteriovenous malformations (AVMs) of the brain deemed inoperable or incompletely obliterated using endovascular or surgical techniques. The AVMs measured from 0.8 to 85 cm3 (mean 28.2 cm3; median 24 cm3). Angiography in 12 patients 1-21 years following radiation therapy demonstrated no significant change in 7, slight reduction in 2, near complete obliteration in 1, and complete obliteration in 2. Magnetic resonance imaging further demonstrated apparent obliteration in one other case. Three irradiated AVMs were available for pathological examination following fatal recurrent hemorrhage after 21 years in case 1 and following surgery after 5 years in cases 2 and 3. Doses of 20 and 45 Gy were delivered to the area of the AVM in 10 and 15 fractions with a 6-MV linear accelerator in case 1 and in cases 2 and 3, respectively. A blinded histopathological comparison was made of the latter cases and three AVMs removed at surgery that were not previously irradiated and that were comparable in size, number of arterial feeders, and location within the brain. Segmental hyalinization of some blood vessels was seen in both irradiated and nonirradiated cases. The single postmortem specimen showed extensive thrombosis but a patent nidus. The findings are in keeping with the clinical impression that conventional fractionated radiation therapy fails to alter the natural history of cerebral AVMs. The favorable outcome of radiosurgery on small- to medium-sized AVMs appears attributable to the shorter duration of therapy using relatively high-dose prescriptions to the nidus.

Conventional radiation therapy of intracranial arteriovenous malformations: long-term results.

Conventional radiation therapy has been used in the treatment of arteriovenous malformations (AVM's) for many years, but there are limited data pertaining to specific treatment parameters, long-term results, and complications. Between 1955 and 1985, 15 patients with AVM's deemed inoperable or incompletely obliterated using surgical or endovascular techniques were treated at the University of Western Ontario. There were nine males and six females, aged 15 to 48 years (mean 29 years). Presenting symptoms included hemorrhage in nine patients, seizures in four, and focal neurological deficits in two. There were three infratentorial and 12 supratentorial AVM's, ranging in size from 1.5 to 6.5 cm. Therapy prior to irradiation consisted of incomplete surgical removal in four cases and subtotal embolization in four. One patient received 2000 cGy of irradiation, while 4000 to 5000 cGy were delivered in the remaining patients to fields ranging in size from 4 x 4 to 14 x 14 cm in 15 to 28 fractions. The 15 patients have been followed for 1 1/2 to 21 years since undergoing radiotherapy (mean 8.1 years). Angiography in 12 patients at 1 to 21 years following irradiation demonstrated no significant change in seven patients, a slight reduction in AVM size in two, near-complete obliteration in one, and complete obliteration in two. One patient with an AVM measuring 6.5 cm refused angiography but underwent magnetic resonance imaging at 5 years which showed no evidence of residual AVM. There were four hemorrhages in 122 patient-years of follow-up study, indicating a hemorrhage rate of 3.3% per year. The authors conclude that conventional irradiation is successful in obliterating AVM's in only about 20% of cases.

Vertebral hemangioma causing spinal cord compression during pregnancy.

Hemangiomas of bone are extremely common vascular tumors that are most commonly discovered as incidental findings in the vertebral column. Infrequently, these benign lesions may cause local or radicular pain and neurologic deficits, from myeloradiculopathy to paralysis. This report describes the occurrence of a symptomatic vertebral hemangioma during pregnancy, in order to illustrate current methods for diagnosis and treatment of these lesions when associated with spinal cord compression. The possible mechanisms by which they may become symptomatic during pregnancy are reviewed.

Diagnosis and management of spinal epidural abscess.

Twenty-five patients with spinal epidural abscess were treated at the University of Western Ontario hospitals between July 1980 and July 1990. There were eighteen males (72%) and seven females (28%), with a median age of 60 years. Concurrent illness resulting in immunocompromise was present in 60%. Eleven presented with complete myelopathy, thirteen had limb weakness, and one had no neurological deficit. In twenty cases the abscess consisted of frankly purulent material, while in five the epidural collection consisted of chronic granulation tissue. Staphylococcus aureus was isolated in 64% of the abscesses. Twenty-seven surgical procedures were performed on 21 patients. Ten cases occurred in the cervical spine (40%), seven in the thoracic spine (28%), three in both the cervical and thoracic spine (12%) and five in the lumbosacral spine (20%). Fourteen patients (56%) retained or recovered ambulation and there were five deaths (20%). The progression from back and radicular pain to weakness and eventual paralysis continues to be characteristic of spinal epidural infection. Morbidity and mortality remain unacceptably high because of delay in diagnosis and treatment. Magnetic resonance imaging is the radiological investigation of choice for the diagnosis of spinal epidural abscess. Prompt intervention, before the development of severe neurological deficits, can improve outcome. Immediate surgical drainage combined with antibiotics remains the treatment of choice.

Correlation of contralateral stenosis and intraoperative electroencephalogram change with risk of stroke during carotid endarterectomy.

Two hundred ninety-three carotid endarterectomies were performed with electroencephalogram (EEG) monitoring and without the use of a shunt. Two hundred sixteen patients had contralateral carotid stenosis of less than 70%; 45 had contralateral stenosis of 70 to 99%; and 32 had contralateral occlusion. There were six perioperative strokes (2.0%) and two deaths (0.7%). Major EEG changes were seen in 11 of the 77 patients (14.3%) with significant contralateral stenosis or occlusion versus 11 of the 216 patients (5.1%) in those without (P less than 0.025). The risk of immediate postoperative deficit was significantly higher in the subgroup with major EEG changes (4 of 22, 18.2%) than in those without such changes (5 of 271, 1.8%) (P less than 0.005). The risk in patients with less than 70% contralateral stenosis (7 of 216, 3.2%) was not significantly different from those with greater contralateral stenosis or occlusion (2 of 77, 2.6%). Carotid endarterectomy can be safely performed without a temporary shunt. Contralateral stenosis or occlusion alone does not confer increased risk. Major EEG changes are infrequent, but they identify a subgroup with significantly higher risk of intraoperative stroke.

The fastigial pressor response. Case report.

A distinct vasomotor and cardioregulatory response first identified experimentally was elicited intraoperatively in a 6-year-old girl by local mechanical stimulation in the vicinity of the fastigial nucleus of the cerebellum. These findings are discussed in the light of current experimental knowledge of the anatomy and physiology of the fastigial pressor response.

Fourth ventricular schwannoma. Case report.

A schwannoma arising from the dorsum of the pontomedullary junction and presenting as an exophytic mass in the fourth ventricle is described. A ventricular schwannoma has not previously been reported in the literature. The presenting clinical and radiographic features and the pathology of this tumor are summarized, and an explanation is sought for its unusual location.