Intranidal Aneurysms Research Articles

Cerebral vasospasm after subarachnoid hemorrhage from severe arteriovenous malformation

Dear Editor,We read with great interest the article entitled“Outcomeof severe arteriovenous malformation-related intracranialhemorrhage: the importance of cisternal subarachnoidhemorrhage and early seizures.” by Rahme et al. [4]Theauthors reviewed the records of 16 consecutive patientswho presented with severe arteriovenous malformation(AVM)-related intracranial hemorrhage. They reportedthat three patients, who had subarachnoid hemorrhage(SAH), died from extensive bihemispheric infarction andrefractory intracranial pressure. Statistical analysisrevealed that SAH and early seizures were significantlyassociated with death. We completely agree with theauthors’ findings and wish to provide further comment.Cerebral vasospasm after SAH from AVM has beenreported to occur in 8-31% of patients [1, 3]. We believethat cerebral vasospasms might be one of the attributablefactors for cerebral infarctions in the three patients whodied in the authors’ series. We consider that physiciansneed to be particularly aware of cerebral vasospasm inpatients with massive SAH from AVM, and that thethreshold of digital subtraction angiography, computedtomography angiography, or magnetic resonance angiographyshouldbeloweredforearlydetectionofcerebralvasospasminpatients with SAH from AVM. Additionally, nimodipine,nicardipine, intra-arterial papaverine, or angioplasty may beefficient for preventing or treating cerebral vasospasm afterSAH from AVM [2, 3, 5]. However, treatment of cerebralvasospasm may augment blood flow to an untreated AVMand promote early rebleeding, especially in cases withuntreated intranidal aneurysms [2, 3, 5]. Early AVM resectioncan prevent rebleeding and also enable treatment of cerebralvasospasm. We consider that early AVM resection andawareness of cerebral vasospasm are required in patientswith massive SAH from AVM.

Intraventricular Hemorrhage Secondary to Intranidal Aneurysm Rupture—Successful Management by Arteriovenous Malformation Embolization Followed by Intraventricular Tissue Plasminogen Activator: Case Report

Intraventricular hemorrhage related to arteriovenous malformation (AVM) rupture is associated with significant morbidity and mortality. Intraventricular tissue plasminogen activator (tPA) has been used to treat spontaneous intraventricular hemorrhage. We demonstrate the successful application of endovascular occlusion to seal the rupture site of an AVM followed by intraventricular tPA. A 32-year-old woman presented with a right frontoparietal parasagittal AVM abutting the motor cortex. The AVM was diagnosed when the patient was 13 years old, and she initially underwent conservative management. At the age of 30, the patient suffered an intracranial hemorrhage, leaving her with left hemiparesis. After rehabilitation, the patient regained ambulation; however, she remained spastic and hyperreflexic on the left side. Two years after her major hemorrhage, she presented for elective treatment of her AVM. The patient was advised to undergo staged embolization before surgical resection of her AVM. The initial embolization was uneventful. A second embolization was complicated by intraventricular hemorrhage and coma. The patient was treated with placement of an external ventricular drain followed by embolization of intranidal aneurysm. After embolization of the intranidal aneurysm the ruptured, the patient was treated with intraventricular tPA. The patient had rapid clearance of the intraventricular hemorrhage and significant improvement in her neurological examination, following commands 24 hours later and returning almost to baseline. This case demonstrates the feasibility of treating AVM-related intraventricular hemorrhage with tPA if the rupture source can be confidently sealed interventionally. This strategy can be lifesaving but needs further study to ensure its safety.

Radiologic Assessment of Brain Arteriovenous Malformations: What Clinicians Need to Know

Brain arteriovenous malformations (AVMs) are abnormal vascular connections within the brain that are presumably congenital in nature. There are several subgroups, the most common being glomerular type brain AVMs, with fistulous type AVMs being less common. A brain AVM may also be a part of more extensive disease (eg, cerebrofacial arteriovenous metameric syndrome). When intracranial pathologic vessels are encountered at cross-sectional imaging, other diagnoses must also be considered, including large developmental venous anomalies, malignant dural arteriovenous fistulas, and moyamoya disease, since these entities are known to have different natural histories and require different treatment options. Several imaging findings in brain AVMs have an impact on decision making with respect to clinical management; the most important are those known to be associated with risk of future hemorrhage, including evidence of previous hemorrhage, intranidal aneurysms, venous stenosis, deep venous drainage, and deep location of the nidus. Other imaging findings that should be included in the radiology report are secondary effects caused by brain AVMs that may lead to nonhemorrhagic neurologic deficits, such as venous congestion, gliosis, hydrocephalus, or arterial steal.

Variety of spinal vascular pathology seen in adult Cobb syndrome

Cobb syndrome is a rare clinical entity that includes the combination of a vascular skin nevus and an angioma in the spinal canal present at identical dermatomal level(s) (cutaneomeningospinal angiomatosis). To date, 38 cases have been reported, only 18 of which are in adults (> 18 years of age). The majority of these cases have been described in the era predating current neuroimaging techniques, and most authors have assumed that each case involves similar vascular pathology. This report highlights 2 patients presenting with similar thoracic cutaneous vascular nevi yet with markedly differing spinal vascular pathology. A 29-year-old man presented with cutaneous hemangioma and a progressive paraparesis and paresthesia of the lower extremities. A 20 x 20-cm port-wine stain over his right upper midback (T6-10) correlated precisely with MR imaging that demonstrated an enhancing epidural mass between T-6 and T-10 causing compression of the cord and cord edema. A 34-year-old man also presented with progressive myelopathy and a 15 x 20-cm port-wine stain within the same dermatomal region as a Type III spinal arteriovenous malformation. Workup for each patient included pre- and postoperative contrast-enhanced MR imaging with vascular sequencing and spinal angiography. The first patient was treated with bilateral laminectomy at the T6-10 levels, with significant postoperative improvement in motor strength. The second patient underwent coil embolization of an intranidal aneurysm, with follow-up embolization 8 years later. Cobb syndrome is an unusual entity in the adult population and should be considered when there is a constellation of cutaneous manifestation and underlying neurological deficit. The vascular skin nevus associated with Cobb syndrome is accompanied by a wide variety of vascular pathologies.

Target Embolization of AVMs: Identification of Sites and Results of Treatment

Although cure of cerebral arteriovenous malformations (AVMs) is the ideal goal it is often only possible with smaller sized lesions. This is certainly true if surgery or radiotherapy is used as the treatment strategy. Endovascular treatment, however, allows the possibility of partial treatment directed at specific areas of AVM architecture. With this in mind we retrospectively reviewed our cohort of AVMs to establish which morphological areas we had identified as targets and how the treatment of the AVM influenced the clinical picture. Over a 36-month period 42 AVMs were treated. In 22 of the patients who presented with a hemorrhage an intranidal aneurysm was identified as a target and treated in nine patients. Other patients presented with headaches (2), neurological deficit (4) and seizures (16) with two patients having their AVM picked up coincidentally. Targets identified included high flow fistulas (12), decreasing venous flow (17) and cure of the AVM (8). Results of targeted treatment showed a lower rehemorrhage rate than anticipated by the natural history. Patients cured did best and targeted embolization improved seizures in nine patients, neurological deficit in four patients and headache in 20 patients. Until safer methods exist to cure large AVMs the use of targeted embolization is acceptable as it protects patients against rehemorrhage and translates into an improvement in their clinical picture.

De novo aneurysm formation and regression after brain arteriovenous malformation embolization: case report

Background The formation of de novo aneurysms is a known complication of vessel occlusion (Wright RL, Sweet WH. Carotid or vertebral occlusion in the treatment of intracranial aneurysms: value of early and late readings of carotid and retinal pressures. Clin Neurosurg 1962:9;163-192). Aneurysms most commonly develop on newly formed primary collateral routes as a result of increased flow through these collaterals. Development of aneurysms is not commonly seen in vessels whose flow has been directly decreased by therapeutic or natural occlusion. Case Description A 53-year-old woman with an intracerebral hemorrhage underwent cerebral angiography which demonstrated a right parietal AVM. An enlarged right ACA gave rise to 3 direct feeding pedicles. Leptomeningeal collaterals from the right MCA as well as the right PCA also gave collateral supply to the AVM. The lesion had superficial drainage into the superior sagittal sinus and deep venous drainage into the right posterior pericallosal vein. No feeding artery aneurysms or intranidal aneurysms were present. Treatment plan included preoperative embolization followed by surgical resection. Conclusion To our knowledge, this is the first reported case of a de novo aneurysm forming and regressing in an artery hemodynamically related to an embolized AVM. The short timescale of its development (6 weeks) is also noteworthy. The spontaneous regression suggests that at least some aneurysms forming in vessels after abrupt decrease in distal runoff may have a self-limited course. Such lesions may do best if not subjected to direct endovascular or surgical treatment.

P.330 Total glossectomy reconstruction with perforator flaps from the lateral thigh

To evaluate the efficacy and safety of renal artery embolisation (RAE) for renal arteriovenous malformation (AVM) as well as its outcomes.The technical and clinical success rates, radiological and laboratory findings, and complications of RAE for 31 renal AVMs in 24 patients (M:F=9:15, mean age 46 years) at two separate medical institutions were retrospectively evaluated. Technical success was defined as complete occlusion of feeding arteries with no residual nidus seen on post-treatment angiography. Clinical failure was defined as recurrence of haematuria, presence of AVM on follow-up ultrasound or computed tomography, repeated RAE or surgery for the control of haematuria. Overall clinical success was defined as resolution haematuria or disappearance of AVM on follow-up imaging after single or multiple sessions of RAE.Types of renal AVM were AVM, arterio-venous fistula (AVF) with intranidal aneurysm, and acquired AVF in 19, 1, and 4 patients, respectively. 18 patients (75%) underwent a single session of RAE, while 6 patients (25%) had two or more sessions of RAE. The level of embolisation was feeder, segmental artery, and main renal artery in 28 (90%), 2 (6%), and 1 (4%) procedures, respectively. Coil, n-butyl 2-cyanoacrylate, and polyvinyl alcohol were the most frequently chosen embolic materials and were used in 19, 14, and 8 procedures, respectively. The clinical success rate after initial RAE was 67% (16/24). Overall clinical success rate, including multisession RAE, was 88% (21/24). The technical success rate of 31 procedures was 65% (20/31). Among 11 technical failures in 10 patients, 4 achieved clinical success without additional RAE, 3 underwent second session RAE to achieve clinical success, and 3 patients underwent nephrectomy due to recurrence.RAE is a safe and effective treatment for renal AVM. Technical failure of RAE does not always lead to clinical failure and multiple embolisation sessions may be effective for recurrent renal AVM.

1429 POSTER A new collimator insert system for stereotactic irradiation of intracranial lesions

Although vasculopathy and de novo aneurysm formation are known complications of traditional radiation therapy, their occurrence following AVM SRS is rare and thus infrequently addressed in the literature. We sought to evaluate these phenomena through a review of our institutional experience.Our review afforded 32 patients treated with LINAC-based SRS over an eight year period. We noted obliteration rates, complication rates and long-term outcomes, with particular attention paid to follow-up angiographic studies.After a mean follow-up of 4.3 years, the overall obliteration rate was 50%, increasing to 87% for AVMs less than 3 cm. Eight patients had nine hemorrhages following SRS (25%). One occurred in the context of a de novo arterial pseudoaneurysm and another in the context of a new venous varix. Two patients with post-SRS hemorrhage had intranidal aneurysms that were not as apparent on initial angiography. Two patients that did not suffer from latency period hemorrhage developed dysplastic changes of feeding arteries, and one patient suffered from early venous thrombosis with resultant permanent hemiparesis from infarction. After a mean follow-up of 4.3 years, 8 patients were clinically improved (25%), 19 were the same (59%), and 5 were worse (16%), including 2 that died as a result of latency period hemorrhage.While radiosurgery of AVMs is safe and successful in the vast majority of cases, vasculopathic complications including de novo aneurysm and varix development, early venous occlusion and stenotic vasculopathy, while infrequent, can occur. Closer long-term angiographic surveillance of these patients may thus be warranted.

脳動静脈奇形の治療における血管内治療の意義―付随動脈りゅうの処置について―

We reviewed 84 AVMs embolized over 7 years and studied the significance of the embolization for associated aneurysms. Out of 84 AVMs, 14 were preoperatively embolized and 66 were followed by radiosurgery. Ten intranidal aneurysms were found in 9 cases, all of which ruptured. Although 8 aneurysms were completely embolized, using glue, 2 incompletely treated aneurysms rebled. Out of 6 proximal feeder aneurysms, 3 ruptured ones were treated with detachable coils and have shown no rebleeding. The other 3 aneurysms that increased in size during the follow-up after the embolization of AVM were embolized without complications. Two flow-related aneurysms remained, and an AVM nidus was primarily treated. Both aneurysms disappeared after the embolization of AVM. The ruptured proximal feeder aneurysms located far from the nidus, which require another approach for the removal of AVM, should be embolized with coils to reduce surgical invasiveness. Embolization of intranidal aneurysms is very useful for the prevention of rebleeding, particularly in cases followed by radiosurgery. Among the flow-related aneurysm treatments, AVM may be the treatment of choice. As for the treatment strategy of AVM, it is important to detect and identify the associated aneurysms and treat them appropriately.

Bleeding after radiosurgery for cerebral arteriovenous malformations.

Obliteration is progressive after radiosurgery (RS) for cerebral arteriovenous malformation (AVM), and until it is complete, there is still a risk of hemorrhage. The aim of our study was to evaluate the severity of hemorrhage after RS, the actuarial risk of hemorrhage, and the parameters associated with hemorrhage. Of 756 patients treated by linear accelerator RS for AVM, 51 (6.5%) had one or more hemorrhages after the RS. We studied the clinical, anatomic, and dosimetric parameters and obliteration rate before hemorrhage and then calculated the actuarial risk per patient and per hemorrhage before and after RS. Correlations between parameters and risk were studied by univariate and multivariate analysis using Kaplan-Meier hemorrhage-free survival curves and the Cox model. Apart from one exclusively ventricular hemorrhage, which caused the death of the patient, only parenchymal hemorrhages were associated with morbidity and neurological deficits (64.5% of all cases of hemorrhage had neurological deficits, 45% had a permanent deficit). The overall mortality rate per hemorrhage was 7.14%. The overall morbidity rate was 47.6%, 26.2% with a permanent deficit. In all but one patient, the AVM was not cured before hemorrhage; thus, the mean obliteration rate before hemorrhage was 24%. The actuarial hemorrhage rates were 3.08% per year per patient and 3.31% per year per hemorrhage. The actuarial rate per patient increased from 1.66% the 1st year to 3.87% in the 5th year after RS but was not statistically different from the rate before radiosurgery. The parameters found to be correlated with hemorrhage risk after RS using multivariate analysis were intranidal or paranidal aneurysms, complete coverage, and minimum dose. The risk of hemorrhage after RS would seem to be the sum of hemorrhage risk factors of the AVM and factors predicting a poor level of obliteration. These factors can be predicted in some cases but rarely avoided.

The relationship of coexisting extranidal aneurysms to intracranial hemorrhage in patients harboring brain arteriovenous malformations.

We hypothesized that coexisting extranidal arterial aneurysms (EAs) would be associated with an increased risk of incident intracranial hemorrhage (ICH) from brain arteriovenous malformation (BAVM) rupture. To determine the presence of EAs and compare the sources and locations of ICH, we retrospectively reviewed the computed tomographic, magnetic resonance imaging, and angiographic studies of patients who presented between 1990 and 1999. EAs were defined as saccular luminal dilations of the parent feeding vessels that were proximally flow-related (i.e., at the circle of Willis), distally flow-related (i.e., distal to the circle of Willis), and unrelated (i.e., in circulation distant from the BAVM). Of 314 BAVM patients, 138 (44%) presented with ICH. In the ICH group, 22 patients (16%) had aneurysmal ICH, 100 (72%) had BAVM ICH, and 16 (12%) had ICH from an indeterminate source. There were 61 patients with 1 or more EAs (29 patients with 42 flow-related proximal aneurysms, 39 patients with 48 flow-related distal aneurysms, and 10 patients with 20 unrelated aneurysms). Multivariate regression analysis revealed that ICH patients were more likely than non-ICH patients to have a coexisting EA (35 versus 13%; odds ratio = 3.9; 95% confidence interval, 2.1-7.5; P < 0.001), but this effect was not present when only BAVM-related ICH was considered (odds ratio = 0.3; 95% confidence interval, 0.1-1.0; P = 0.052). Other independent predictors of ICH included small AVM size (<3 cm), exclusively deep venous drainage, and the presence of an intranidal aneurysm. Clinical presentation with ICH was associated with EA aneurysms, but the association was due to aneurysmal rather than BAVM rupture, suggesting that EAs and the BAVM ICH risks may be considered as separate entities in future studies.

Intention-to-treat analysis of Spetzler-Martin grades IV and V arteriovenous malformations: natural history and treatment paradigm.

In this study the authors quantified a subgroup of patients with Spetzler-Martin Grades IV and V arteriovenous malformations (AVMs) recommended for complete, partial, or no treatment, and calculated the retrospective hemorrhage rate for these lesions. Between July 1997 and May 2000, 73 consecutive patients with Grades IV and V AVMs were evaluated prospectively by the cerebrovascular team at Barrow Neurological Institute. Treatment recommendations given to the patients or referring physicians were classified as complete treatment, partial treatment, and no treatment. Retrospectively, the hemorrhage rates associated with these treatment groups were also calculated. In the prospective portion of the study (the intention-to-treat analysis), no treatment of the AVM, was recommended for 55 patients (75%) and partial treatment was recommended for seven patients (10%). Aneurysms associated with an AVM were obliterated by surgical or endovascular treatment in seven patients (10%), and complete surgical removal was recommended for four patients (5%). The overall hemorrhage rate for Grades IV and V AVMs was 1.5% per year. The annual risk of hemorrhage was 10.4% among patients who previously had received incomplete treatment, compared with patients without previous treatment. The hemorrhage risk of 1.5% per year, which was associated with Grades IV and V AVMs appears to be lower than that reported for Grades I through III AVMs. The authors recommend that no treatment be given for most Grades IV and V AVMs. No evidence indicates that partial treatment of an AVM reduces a patient's risk of hemorrhage. In fact, partial treatment may worsen the natural history of an AVM. The authors do not support palliative treatment of AVMs, except in the specific circumstances of arterial or intranidal aneurysms or progressive neurological deficits related to vascular steal. Complete treatment is warranted for patients with progressive neurological deficits caused by hemorrhage of the AVM. This selection process plays a significant role in the relatively low combined morbidity and mortality rates for Grade IV and Grade V AVMs (17 and 22%, respectively) reported by the cerebrovascular group in both retrospective and prospective studies.

Concurrent arterial aneurysms in brain arteriovenous malformations with haemorrhagic presentation

Objective: To assess the effect of concurrent arterial aneurysms on the risk of incident haemorrhage from brain arteriovenous malformations (AVMs). Methods: In a cross sectional study, 463 consecutive, prospectively enrolled...

脳動静脈奇形に対する治療適応 臨床判断分析による検討

To decide optimal treatment for various cerebral arteriovenous malformations (AVMs) is a highly complex issue. We retrospectively examined the clinical course of 24 cases of AVMs in reference to angiographic features, and performed clinical decision analysis to develop a logical therapeutic strategy. Annual bleeding rate was calculated in each group with specific angioarchitecture. The average bleeding rate was estimated at 3.2% per year. The rate was higher in the group with more hazardous angioarchitectures: 8.6% with intranidal aneurysm, and 5.5% with venous stenosis, respectively. Decision analysis demonstrated that Spetzler grade III AVM patients of 56 years or younger can expect better results from surgery than from conservative treatment. In grade IV, those of 48 years or younger can also expect better results from surgery. Because bleeding tends to develop more frequently in patients with intranidal aneurysm, older patients with this angioarchitecture (grade III: up to 70 years, grade IV: up to 60 years) can still expect better results from surgery. Clinical decision analysis is a helpful approach to plan a logical therapeutic strategy for AVMs.

The Effect of Concurrent Arterial Aneurysms on the Risk of Hemorrhagic Presentation in Brain Arteriovenous Malformations

119 Background and Purpose: To assess the effect of concurrent arterial aneurysms on the risk of hemorrhagic presentation in brain arteriovenous malformations (AVMs). Methods: The 463 consecutive, prospectively enrolled patients from the New York AVM Databank were analyzed. Concurrent arterial aneurysms on brain angiography were classified as (1) flow-related feeding artery aneurysms, (2) intranidal aneurysms, and (3) aneurysms unrelated to blood flow to the AVM. Clinical presentation (diagnostic event) was categorized as (1) intracranial hemorrhage proven by imaging or (2) non-hemorrhagic presentation. Univariate and multivariate statistical models were applied to test the effect of age, gender, AVM size, venous drainage pattern, and the three different types of aneurysms on the risk of AVM hemorrhage at initial presentation. Results: Arterial aneurysms were found in 117 (25%) AVM patients. In 93 cases, a single aneurysm type was found (54 had feeding artery aneurysms, 21showed intranidal aneurysms, 18 had unrelated aneurysms), 24 patients had more than one aneurysm type. Overall, 204 (44%) patients presented with hemorrhage. Concurrent arterial aneurysms were significantly more frequent in patients with incident AVM hemorrhage (34%) as compared to those without hemorrhage (18%, p=0.001). In the multivariate model an independent effect for flow-related aneurysms (OR 2.1 , 95% CI: 1.2 to 3.8) on hemorrhagic AVM presentation was found. No effect was seen for intranidal and unrelated aneurysms. The attributable risk of incident hemorrhage in AVM patients harbouring flow-related aneurysms is 0.059 (95% CI: 0.01 to 0.105). Conclusions: The findings suggest that flow-related arterial aneurysms are an independent determinant for increased risk of incident AVM hemorrhage.

The Effect of Concurrent Arterial Aneurysms on the Risk of Hemorrhagic Presentation in Brain Arteriovenous Malformations

119 Background and Purpose: To assess the effect of concurrent arterial aneurysms on the risk of hemorrhagic presentation in brain arteriovenous malformations (AVMs). Methods: The 463 consecutive, prospectively enrolled patients from the New York AVM Databank were analyzed. Concurrent arterial aneurysms on brain angiography were classified as (1) flow-related feeding artery aneurysms, (2) intranidal aneurysms, and (3) aneurysms unrelated to blood flow to the AVM. Clinical presentation (diagnostic event) was categorized as (1) intracranial hemorrhage proven by imaging or (2) non-hemorrhagic presentation. Univariate and multivariate statistical models were applied to test the effect of age, gender, AVM size, venous drainage pattern, and the three different types of aneurysms on the risk of AVM hemorrhage at initial presentation. Results: Arterial aneurysms were found in 117 (25%) AVM patients. In 93 cases, a single aneurysm type was found (54 had feeding artery aneurysms, 21showed intranidal aneurysms, 18 had unrelated aneurysms), 24 patients had more than one aneurysm type. Overall, 204 (44%) patients presented with hemorrhage. Concurrent arterial aneurysms were significantly more frequent in patients with incident AVM hemorrhage (34%) as compared to those without hemorrhage (18%, p=0.001). In the multivariate model an independent effect for flow-related aneurysms (OR 2.1 , 95% CI: 1.2 to 3.8) on hemorrhagic AVM presentation was found. No effect was seen for intranidal and unrelated aneurysms. The attributable risk of incident hemorrhage in AVM patients harbouring flow-related aneurysms is 0.059 (95% CI: 0.01 to 0.105). Conclusions: The findings suggest that flow-related arterial aneurysms are an independent determinant for increased risk of incident AVM hemorrhage.

脳動静脈奇形の塞栓術におけるｐｉｔｆａｌｌとその対策

As the embolization of AVMs is often an adjuvant therapy combined with surgical extirpation or radiosurgery, the goal is to optimize the outcome of the following procedure. As the natural history of AVMs predicts a relatively low rate of neurological injury, the combined therapeutic modalities should have a low complication rate. We report the perisurgical complications of 66 AVMs and discuss techniques to avoid complications. Of the 66 patients treated with endovascular embolization, 14 subsequently underwent surgical resection and 43 had radiosurgery. Four patients obtained total occlusion of their AVM by embolization alone and required no further treatment. In 48 patients, more than 70% of the nidus was occluded with embolization. We observed 3 permanent and 9 temporary complications. Four complications occurred immediately after embolization, due to overembolization or thromboembolism. Seven delayed complications occurred, possibly due to retrograde thrombosis or a chemical reaction to the glue. In 4 of the 14 cases without AVM obliteration following embolization and radiosurgery, meningeal feeders developed or recanalized after the treatment with absorbable particles. We recommend embolization prior to radiosurgery to treat all fistulous and meningeal feeders and packing of the nidus with non-absorbable embolic materials. In 10 cases, repeat embolization achieved further nidus reduction prior ro repeat radiosurgery. Intranidal aneurysms that pose a high risk of bleeding were also embolized. To avoid complications with embolization, the AVM angioarchitecture, hemodynamics and functional location should be well recognized. Complications can be reduced with preoperative functional imaging, superselective angiograms, appropriate selection of embolic materials, and appropriate selection of embolization targets. The priority of vessels to be embolized is dictated by the subsequent treatment. Agressive embolization of high-risk vessels or those that will cause abrupt hemodynamic changes should be avoided.

Embolization of Arteriovenous Malformations Prior to Radiosurgery

Embolization prior to radiosurgery is useful to reduce the AVM nidus for adequate planning for radiosurgery. In 37 cases we encountered, patients with the least radiosurgical effects had diffuse type nidus, where the feeders embolized with absorbable embolic materials had the possibility of recanalization. The main purpose of embolization is to prevent bleeding while the radiosurgical effects are being fully obtained. Thus, nidus embolization and the occlusion of fistulous feeders, meningeal feeders and intranidal aneurysms using permanent embolic materials are essential, since effective and successful embolization can increase the occlusion rate and shorten the period until complete occlusion following radiosurgery.

Cerebral arteriovenous malformations and associated aneurysms: analysis of 305 cases from a series of 662 patients.

Spontaneous intracranial hemorrhage is the primary danger for patients with cerebral arteriovenous malformations (AVMs). Associated aneurysms are considered weak points that increase the risk of intracranial hemorrhage. Aneurysms are classified as proximal aneurysms (PROXs) or intranidal aneurysms (INs). The present study was based on a series of 662 patients who presented with AVMs between 1985 and 1995. Its purpose was to evaluate prestated hypotheses using prospectively collected data. In 305 of these 662 patients, 372 INs and 313 PROXs were observed and analyzed with respect to their shapes, locations, and sizes. Partial targeted endovascular treatment with n-butylcyanoacrylate was performed for 450 of the 662 patients (68%) in this series, using a standard protocol. Of 450 treated patients, 181 (40%) had at least one IN and 138 (30.7%) had at least one PROX. Analysis of changes in the sizes of PROXs was based on the follow-up data for 83 treated patients, with a total of 149 PROXs. Changes in the sizes of PROXs in treated patients were analyzed with respect to PROX shapes, PROX locations, and treated AVM occlusion rates. Univariate and multivariate event data analyses were used to study factors influencing aneurysm shrinkage. False aneurysms were excluded from the series. Presentation with intracranial hemorrhage was not correlated with any type of aneurysm. However, INs demonstrated a higher rebleeding rate (P < 0.002) before treatment. Among 181 patients, 92.2% of INs were occluded, together with the related portions of the AVM nidi. In cases of PROXs, embolization of the cerebral AVM compartment fed by the artery with the aneurysm was a priority. During follow-up monitoring of 83 treated patients with 149 PROXs, 100% shrinkage was observed for 12 PROXs and more than 50% shrinkage was observed for 33 PROXs. The median time required for more than 50% shrinkage was 3.5 years. The shrinkage of PROXs was influenced by the degree of AVM occlusion (P = 0.027) and occurred faster for PROXs on midline structures, such as the anterior cerebral artery and the circle of Willis, compared with arteries distal to the circle of Willis (P = 0.004). No rupture of untreated PROXs was observed after partial targeted treatment of AVMs. PROXs are not primary treatment targets, compared with AVMs themselves. INs should be primary targets of endovascular therapy, because of their increased risk of rebleeding.

Effectiveness and Pitfall of Embolization of Cerebral Arteriovenous Malformations

We studied the course ofperisurgical complications of 66 AVMs and discussed the approapriate precautions. Of 66 patients with AVMs, 14 underwent postembolization surgical removal, and 43 underwent radiosurgery. Four patients were cured with total occlusion of their AVM by embolization alone. 48 patients achieved a more than 70% occlusion of the nidus. We observed 12 complications including 3 permanent and 9 temporary. Four complications occurred immediately after the embolization due to overembolization or thromboembolism, and 7 were observed several hours later which might have been caused by retrograde thrombosis or a chemical reaction to the glue. While presurgical embolization deepseated feeders must be embolized along with fistulous or high-flow feeders, 4 cases of 2nd embolization following radiosurgery showed that meningeal feeders developed or recanalized in cases embolized with absorbable particles. Thus, preradiosurgically, fistulous and meningeal feeders should be treated, and the nidus must be packed with embolic materials with no risk of recanalization. Successful nidus packing performed in 10 AVMs yielded a further nidus reduction before radiosurgery. The intranidal aneurysms which pose a high risk of rebleeding were also embolized. In order to avoid complications in the embolization of AVM, the angioarchitecture, hemodynamics and the relationship to brain function should be well recognized by preoperative functional imaging and superselective angiograms, and adequate embolic materials should be properly injected. As an embolization strategy, the priority of the target feeders should depend on the treatment to follow, and aggressive embolization of risky feeders or causing abrupt hemodynamic change should be avoided.