Embolisation of cerebral arteriovenous malformations to assure successful subsequent radiosurgery

The role of procedural factors on the outcomes of embolization followed by radiosurgery for the treatment of brain arteriovenous malformations: systematic review and proportional meta-analyses

BACKGROUND

Multimodal therapy for brain arteriovenous malformations (bAVM) with embolization followed by stereotactic radiosurgery (E + SRS) has shown varying outcomes. Its benefits over other treatment modalities have been questioned. The goal of this systematic review was to determine the factors associated with cure and complication rates of this treatment strategy.

METHODS

A literature search in Medline and Global Index Medicus, from inception to October 2023, was performed. Studies reporting relevant outcome data from bAVM patients treated with E + SRS were included. Data on several patient, lesion and procedure-related factors were collected. Embolization intent was classified as Targeted (of high-risk features), Devascularizing (feeder embolization/flow reduction) and Occluding (intent-to-cure, nidus embolization). The primary outcome was obliteration rate. Secondary outcomes were post-SRS bleeding (PSB), post-embolization neurological complications (PENC) and post-SRS neurological complications (PSNC). Subgroup analyses included embolic agent, embolization intent and radiosurgery type. Proportional meta-analyses and meta-regressions were performed.

RESULTS

Forty-one studies were included in the review. The pooled obliteration rate was 56.45% (95% CI 50.94 to 61.88). Meta-regression analyses showed higher obliteration rates with Copolymers and lower obliteration rates with Devascularizing embolization. The pooled PSB, PENC and PSNC rates were 5.50%, 13.75% and 5.02%, respectively. Meta-regression analyses showed higher rates of PSB, PENC and PSNC with Devascularizing embolization, Liquid & Solid embolic agents and Targeted & Devascularizing intent, respectively.

CONCLUSION

Embolic agent and embolization intent were procedural factors associated with treatment outcomes of E + SRS in the management of bAVM patients. The efficacy and safety profiles favor copolymers as embolic agents and disfavor Devascularizing as embolization intent.

STUDY REGISTRATION

The protocol of the systematic review was registered in PROSPERO as CRD42023474171.

The Era of Onyx Embolization: A Systematic and Literature Review of Preoperative Embolization Before Stereotactic Radiosurgery for the Management of Cerebral Arteriovenous Malformations

INTRODUCTION

The current treatment paradigm for intracranial arteriovenous malformations (AVMs) focuses on reducing the risk of intracranial hemorrhage using various therapeutic means including embolization, stereotactic radiosurgery (SRS), and microsurgical resection. To improve AVM obliteration rates with SRS, pre-radiosurgical embolization has been trialed in a number of studies to reduce the volume of the AVM nidus prior to radiosurgery. This study aimed to review the efficacy of pre-radiosurgical embolization in the pre-Onyx era compared to the current Onyx era.

METHODS

A systematic review was performed using PubMed to identify studies with 20 or more AVM patients, embolization material, and obliteration rates for both embolization + stereotactic radiosurgery (E+SRS) and SRS-only groups.

RESULTS

Seventeen articles consisting of 1133 eligible patients were included in this study. A total of 914 (80.7%) patients underwent embolization prior to SRS. Onyx was used as the embolysate in 340 (37.2%) patients in the E+SRS cohorts. Mean obliteration rate for the embolized cohort was 46.9% versus 46.5% in the SRS-only cohort. When comparing obliteration rates based on embolysate material, obliteration rate was 42.1% with Onyx+SRS and 50.0% in the non-Onyx embolysate + SRS cohort.

CONCLUSIONS

Onyx (ethylene vinyl-alcohol copolymer dissolved in dimethyl sulfoxide and suspended in micronized tantalum powder) has been increasingly used for the embolization of intracranial AVMs with increased success regarding its ease of use from a technical standpoint and performs similarly to other embolysate materials.

State of the Art in the Role of Endovascular Embolization in the Management of Brain Arteriovenous Malformations-A Systematic Review

As a significant cause of intracerebral hemorrhages, seizures, and neurological decline, brain arteriovenous malformations (bAVMs) are a rare group of complex vascular lesions with devastating implications for patients' quality of life. Although the concerted effort of the scientific community has improved our understanding of bAVM biology, the exact mechanism continues to be elucidated. Furthermore, to this day, due to the high heterogeneity of bAVMs as well as the lack of objective data brought by the lack of evaluative and comparative studies, there is no clear consensus on the treatment of this life-threatening and dynamic disease. As a consequence, patients often fall short of obtaining the optimal treatment. Endovascular embolization is an inherent part of multidisciplinary bAVM management that can be used in various clinical scenarios, each with different objectives. Well-trained neuro-interventional centers are proficient at curing bAVMs that are smaller than 3 cm; are located superficially in noneloquent areas; and have fewer, larger, and less tortuous feeding arteries. The transvenous approach is an emerging effective and safe technique that potentially offers a chance to cure previously untreatable bAVMs. This review provides the state of the art in all aspects of endovascular embolization in the management of bAVMs.

Efficacy and Safety of Combined Endovascular Embolization and Stereotactic Radiosurgery for Patients with Intracranial Arteriovenous Malformations: A Systematic Review and Meta-Analysis

Whether the use of endovascular embolization could provide additional benefits in patients treated with stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (IAVMs) remains controversial. The current meta-analysis was conducted to assess the efficacy and safety of SRS with and without prior endovascular embolization in patients with IAVMs. The electronic databases of PubMed, EmBase, and Cochrane Library were systematically searched for eligible studies published from inception to August 12, 2020. The pooled results for obliteration rate, rehemorrhage rate, and permanent neurological deficits were calculated by odds ratios (ORs) with 95% confidence intervals (CIs) using the random-effects model. The sensitivity analysis, subgroup analysis, and publication bias for investigated outcomes were also evaluated. Nineteen studies (two prospective and 17 retrospective studies) involving a total of 3,454 patients with IAVMs were selected for the final meta-analysis. We noted that prior embolization and SRS were associated with a lower obliteration rate compared with SRS alone (OR, 0.57; 95% CI, 0.44–0.74; P < 0.001). However, prior embolization and SRS were not associated with the risk of rehemorrhage (OR, 1.05; 95% CI, 0.81–1.34; P = 0.729) and permanent neurological deficits (OR, 0.80; 95% CI, 0.48–1.33; P = 0.385) compared with SRS alone. The sensitivity analysis suggested that prior embolization might reduce the risk of permanent neurological deficits in patients with IAVMs treated with SRS. The treatment effects of prior embolization in patients with IAVMs could be affected by nidus volume, margin dose, intervention, and follow-up duration. This study found that prior embolization was associated with a reduced risk of obliteration in patients with IAVMs treated with SRS. Moreover, prior embolization might reduce the risk of permanent neurological deficits in patients with IAVMs.

Gamma Knife Radiosurgery For Brain Vascular Malformations: Current Evidence And Future Tasks

Gamma Knife radiosurgery (GKRS) has long been used for treating brain vascular malformations, including arteriovenous malformations (AVMs), dural arteriovenous fistulas (DAVFs), and cavernous malformations (CMs). Herein, current evidence and controversies regarding the role of stereotactic radiosurgery for vascular malformations are described. 1) It has already been established that GKRS achieves 70–85% obliteration rates after a 3–5-year latency period for small to medium-sized AVMs. However, late radiation-induced adverse events (RAEs) including cyst formation, encapsulated hematoma, and tumorigenesis have recently been recognized, and the associated risks, clinical courses, and outcomes are under investigation. SRS-based therapeutic strategies for relatively large AVMs, including staged GKRS and a combination of GKRS and embolization, continue to be developed, though their advantages and disadvantages warrant further investigation. The role of GKRS in managing unruptured AVMs remains controversial since a prospective trial showed no benefit of treatment, necessitating further consideration of this issue. 2) Regarding DAVFs, GKRS achieves 41–90% obliteration rates at the second post-GKRS year with a hemorrhage rate below 5%. Debate continues as to whether GKRS might serve as a first-line solo therapeutic modality given its latency period. Although the post-GKRS outcomes are thought to differ among lesion locations, further outcome analyses regarding DAVF locations are required. 3) GKRS is generally accepted as an alternative for small or medium-sized CMs in which surgery is considered to be too risky. The reported hemorrhage rates ranged from 0.5–5% after GKRS. Higher dose treatments (>15 Gy) were performed during the learning curve, while, with the current standard treatment, a dose range of 12–15 Gy is generally selected, and has resulted in acceptable complication rates (< 5%). Nevertheless, further elucidation of long-term outcomes is essential.

Effectiveness of Preradiosurgical Embolization with NBCA for Arteriovenous Malformations - Retrospective Outcome Analysis in a Japanese Registry of 73 Patients (J-REAL study)

Purpose

Recent reports have posed doubts about the effect of preradiosurgical embolization in brain arteriovenous malformation (AVM) because it makes the planning of stereotactic radiosurgery (SRS) difficult and has the risk of recanalization out of the target. We investigated whether the performance and quality of embolization may influence the success of SRS based on a retrospective case cohort study.

Materials and Methods

Seventy-three patients who underwent embolization followed by SRS between 2003 and 2012 in eight institutes with neurointerventionists were considered. They were divided into the following two groups at 3 years of follow up after the final SRS: “successful occlusion group” (S group), with radiologically complete occlusion of AVM; and “non-successful occlusion group” (N group) with persistent remnant nidus or abnormal vascular networks. Patient background, AVM profile, embolization performance grade and complications were compared in each group. The quality of embolization was evaluated with the new grading system: embolization performance grade (E grade), specializing the achievement of nidus embolization. E grade A was defined as sufficient nidus embolization with more than half of the total number of feeders achieving nidus penetration. E grade B was defined as less than half achievement of nidus embolization, and E grade C was defines as failure to perform nidus embolization.

Results

Forty-three patients were included in the S group, and 29 patients were included in the N group. The size and Spetzler-Martin grade of AVM and the rate of diffuse type was higher in the N group without statistical significance. The embolization performance level according to E grade indicated a significantly higher rate of successful embolization with more than 50% of nidus penetration in the S group (P<0.001). This difference was also confirmed in the subanalysis for limited cases, excluding smaller AVMs with complete occlusion with SRS alone (P=0.001).

Conclusion

The cause of the unsuccessful result of post-embolization SRS might be the large, diffuse angioarchitecture, but proper embolization with a high rate of nidus penetration to avoid recanalization is more important. Effective embolization is essential to contribute to and promote the effect of radiosurgery.

Stereotactic radiosurgery with and without embolization for intracranial arteriovenous malformations: a systematic review and meta-analysis

OBJECT

The effectiveness and risk of stereotactic radiosurgery (SRS) in the management of partially embolized intracranial arteriovenous malformations (AVMs) remain controversial. The aim of this analysis was to assess current evidence regarding the efficiency and safety of SRS for AVM patients with and without prior embolization.

METHODS

To compare SRS in patients with and without embolization, the authors conducted a meta-analysis of studies by searching the literature via PubMed and EMBASE for the period between January 2000 and December 2013, complemented by a hand search. Primary outcome was the rate of AVM obliteration on a 3-year follow-up angiogram. Secondary outcome was the rate of hemorrhage at 3 years after SRS. Tertiary outcome was permanent neurological deficits related to radiation-induced changes.

RESULTS

Ten studies eligible for analysis included 1988 patients: 593 had undergone embolization followed by SRS and 1395 had undergone SRS alone. The AVM obliteration rate was significantly lower in patients who had undergone embolization followed by SRS than in those who had undergone SRS alone (41.0% vs 59%, OR 0.46, 95% CI 0.37-0.56, p < 0.00001). However, the rates of hemorrhage (7.3% vs 5.6%, OR 1.17, 95% CI 0.74-1.83, p = 0.50) and permanent neurological deficits related to radiation-induced changes (3.3% vs 3.4%, OR 1.41, 95% CI 0.64-3.11, p = 0.39) were not significantly different between the two groups.

CONCLUSIONS

Embolization before SRS significantly decreases the AVM obliteration rate. However, there is no significant difference in the risk of hemorrhage and permanent neurological deficits after SRS alone and following embolization. Further validation by well-designed prospective or randomized cohort studies is still needed.

Guidelines for the use of NBCA in vascular embolization devised by the Committee of Practice Guidelines of the Japanese Society of Interventional Radiology (CGJSIR), 2012 edition

Cyanoacrylates are a group of fast-acting adhesives. They form low viscosity liquids in the monomer state and instantly polymerize to become adhesive upon contact with ionic substances. Since the 1950s, they have been used around the world for industrial and household purposes. N-butyl cyanoacrylate (NBCA) is a cyanoacrylate that is commonly used for medical care, and the closure of skin wounds with NBCA has been found to promote hemostasis. However, in Japan, the intravascular injection of NBCA is considered to be off-label use, except during the treatment of gastric varices under endoscopy. The use of NBCA in embolotherapy is considered when the target vessels cannot be cannulated superselectively, for vascular diseases that require long segments of the target vessel to be embolized, or for patients in a hypocoagulable state. NBCA-based embolotherapy can be used to treat vascular malformations, acute hemorrhaging, tumors, and venous disease. The complications associated with NBCA-based embolotherapy include tissue ischemia, hemorrhaging, systemic or local reactions, and catheter adhesion to blood vessels. NBCA is mixed with Lipiodol to make it radiopaque and to adjust its polymerization time. Since there are various technical aspects to performing NBCA-based embolotherapy safely, it should be carried out by, or with the assistance of, proficient interventional radiologists.

Long-term results of gamma knife surgery for partially embolized arteriovenous malformations

BACKGROUND

The effectiveness and risk of gamma knife surgery (GKS) in the management of partially embolized cerebral arteriovenous malformations (AVMs) remain to be elucidated.

OBJECTIVE

To evaluate the long-term imaging and clinical outcomes of GKS in AVM patients who had undergone previous partial embolization and compare the results with patients treated with GKS alone.

METHODS

A total of 215 embolized AVMs were analyzed. The mean patient age was 32.9 years. The mean volume of the nidus was 4.6 mL (range, 0.1-29.4 mL), and the mean prescription dose was 19.6 Gy (range, 4-28 Gy). This group was compared with 729 nonembolized AVMs.

RESULTS

After embolization and GKS, angiographically confirmed total obliteration of the AVMs was significantly lower (33%) compared with patients in whom GKS was used alone (60.9%; P < .001). However, the mean nidus size was larger and the Spetzler-Martin grade was higher for the embolized AVMs compared with the nonembolized AVMs. Radiation-induced changes occurred more often in the embolized (43.4%) than the nonembolized (33.4%) AVMs (P = .028). Permanent neurological deficits associated with radiation-induced changes occurred in 2.7% of the embolized compared with 1.3% of the nonembolized patients (P = .14).

CONCLUSION

In our retrospective and historical series, the long-term results suggest that the obliteration rate is significantly lower in embolized AVMs compared with nonembolized AVMs, also because of the fact that the combined treatment is applied to higher grade AVMs; the percentage of grade III-V AVMs was 58.6% and 48.8% for nonembolized AVMs.

Multimodality treatment of cerebral arteriovenous malformations

BACKGROUND

Many arteriovenous malformations (AVMs) can be treated with one modality, but with increasing complexity a combination of techniques, including surgical excision, embolization, and radiosurgery, may be beneficial. The 2 senior authors' experience in the multimodal management of AVMs from 1980-2008 is reported, including the results in all patients with rehemorrhage while awaiting treatment or after partial initial treatment has begun. The series contains a disproportionately high number of Spetzler-Martin grade IV and V lesions, owing to the nature of the referral practice.

METHODS

Data were collected prospectively. Only patients who were managed until treatment options were exhausted were included; this entailed either treatment to the point of AVM obliteration or inability to treat further using any or all modalities. Patients who presented with intracranial hemorrhage (ICH) in extremis in whom the AVM was excised during the first operation were also included.

RESULTS

Of the 290 patients, 265 underwent treatment, and 25 were managed conservatively. An unruptured AVM was present in 48% of patients. Cure was achieved in 233 (88%) of treated patients. Cure was achieved in 25 of 37 patients undergoing radiosurgery only, 56 of 57 undergoing surgery, 100 of 101 undergoing embolization and microsurgical excision, 20 of 34 undergoing embolization alone, 12 of 17 undergoing embolization and radiosurgery, 5 of 5 undergoing surgery and radiosurgery, and 14 of 14 patients undergoing all 3 modalities. Spetzler-Martin grade was found to correlate negatively with cure (P < 0.001). There was a good outcome in 210 patients (72%), moderate disability in 40 patients (14%), severe disability in 22 patients (8%), vegetative state in 1 patient, and 17 patients (6%) died. There was a favorable outcome (no or only moderate deficits) in 93% of patients with Spetzler-Martin grade I-III lesions. The outcome was favorable in 13 of 25 patients (52%) having no treatment, 32 of 37 (86%) having radiosurgery only, 30 of 34 (88%) having embolization only, 54 of 57 (95%) having surgery only, 87 of 101 (86%) having embolization and surgery, 16 of 17 (94%) having embolization and radiosurgery, 5 of 5 (100%) having surgery and radiosurgery, and 13 of 14 (93%) having all 3 modalities. These outcomes included morbidity from initial presenting symptoms, from treatment, and from rehemorrhage. Good recovery was more likely in patients who were treated with surgery as one of the treatments (P = .025). Considering only new deficits related to treatment, 9 patients (3%) incurred severe neurologic deficits, 11 patents died after treatment, 2 patients died of postoperative hematomas, and 6 died of rehemorrhage from residual AVM. Increasing age, Spetzler-Martin grade, and rehemorrhage were correlated with a poorer Glasgow Outcome Scale score (P < 0.05).

CONCLUSIONS

These data suggest a higher risk of hemorrhage after partial obliteration of AVM. One should ascertain an acceptably high likelihood of complete obliteration before embarking on treatment. Using a multimodality approach, the authors were able to cure 92% of treated Spetzler-Martin grade I-IV lesions but only 53% of treated Spetzler-Martin grade V lesions. A major neurologic deficit, disabling to the patient, was incurred in 3% of cases, and 11 patients died.

Embolization and radiosurgery for arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) requires a multidisciplinary management including microsurgery, endovascular embolization, and stereotactic radiosurgery (SRS). This article reviews the recent advancements in the multimodality treatment of patients with AVMs using endovascular neurosurgery and SRS. We describe the natural history of AVMs and the role of endovascular and radiosurgical treatment as well as their interplay in the management of these complex vascular lesions. Also, we present some representative cases treated at our institution.

Combined endovascular embolization and stereotactic radiosurgery in the treatment of large arteriovenous malformations

Object

Large cerebral arteriovenous malformations (AVMs) are often not amenable to direct resection or stereotactic radiosurgery (SRS) treatment. An alternative treatment strategy is staged endovascular embolization followed by SRS (Embo/SRS). The object of this study was to examine the experience at Washington University in St. Louis with Embo/SRS for large AVMs and review the results in earlier case series.

Methods

Twenty-one cases involving patients with large AVMs treated with Embo/SRS between 1994 and 2006 were retrospectively evaluated. The AVM size (before and after embolization), procedural complications, radiological outcome, and neurological outcome were examined. Radiological success was defined as AVM obliteration as demonstrated by catheter angiography, CT angiography, or MR angiography. Radiological failure was defined as residual AVM as demonstrated by catheter angiography, CT angiography, or MR angiography performed at least 3 years after SRS.

Results

The maximum diameter of all AVMs in this series was > 3 cm (mean 4.2 cm); 12 (57%) were Spetzler-Martin Grade IV or V. Clinical follow-up was available in 20 of 21 cases; radiological follow-up was available in 19 of 21 cases (mean duration of follow-up 3.6 years). Forty-three embolization procedures were performed; 8 embolization-related complications occurred, leading to transient neurological deficits in 5 patients (24%), minor permanent neurological deficits in 3 patients (14%), and major permanent neurological deficits in none (0%). Twenty-one SRS procedures were performed; 1 radiation-induced complication occurred (5%), leading to a permanent minor neurological deficit. Of the 20 patients with clinical follow-up, none experienced cerebral hemorrhage. In the 19 patients with radiological follow-up, AVM obliteration was confirmed by catheter angiography in 13, MR angiography in 2, and CT angiography in 1. Residual nidus was found in 3 patients. In patients with follow-up catheter angiography, the AVM obliteration rate was 81% (13 of 16 cases).

Conclusions

Staged endovascular embolization followed by SRS provides an effective means of treating large AVMs not amenable to standard surgical or SRS treatment. The outcomes and complication rates reported in this series compare favorably to the results of other reported therapeutic strategies for this very challenging patient population.

A prospective, multicenter, randomized trial of the Onyx liquid embolic system and N-butyl cyanoacrylate embolization of cerebral arteriovenous malformations

Object

The Onyx liquid embolic system (Onyx) was approved in the European Union in 1999 for embolization of lesions in the intracranial and peripheral vasculature, including brain arteriovenous malformations (AVMs) and hypervascular tumors. In 2001 a prospective, equivalence, multicenter, randomized controlled trial was initiated to support a submission for FDA approval. The objective of this study was to verify the safety and efficacy of Onyx compared with N-butyl cyanoacrylate (NBCA) for the presurgical treatment of brain AVMs.

Methods

One hundred seventeen patients with brain AVMs were treated with either Onyx (54 patients) or NBCA (63 patients) for presurgical endovascular embolization between May 2001 and April 2003. The primary end point was technical success in achieving ≥ 50% reduction in AVM volume. Secondary end points were operative blood loss and resection time. All adverse events (AEs) were reported and assigned a relationship to the Onyx or NBCA system, treatment, disease, surgery, or other/unknown. The Data Safety Monitoring Board adjudicated AEs, and a blinded, independent core lab assessed volume measurements. Patients were monitored through discharge after the final surgery or through a 3- and/or 12-month follow-up if resection had not been performed or was incomplete.

Results

The use of Onyx led to ≥ 50% AVM volume reduction in 96% of cases versus 85% for NBCA (p = not significant). The secondary end points of resection time and blood loss were similar. Serious AEs were also similar between the 2 treatment groups.

Conclusions

Onyx is equivalent to NBCA in safety and efficacy as a preoperative embolic agent in reducing brain AVM volume by at least 50%.

Operation for delayed symptomatic brain oedema after treatment of an arteriovenous malformation by embolization and radiosurgery

A patient with a Spetzler-Martin-grade-III AVM, initially embolized and then stereotactically irradiated, who - with a latency of several months - showed progressive neurological deterioration, is reported. Magnetic resonance imaging revealed enormous ipsilateral brain oedema, which did not respond to dexamethasone. Upon further neurological deterioration the former AVM nidus plus an adjacent rim of brain tissue were removed and the patient recovered considerably. It is concluded that embolization in conjunction with irradiation may impair the blood-brain-barrier with resulting long-term oedema in the surrounding brain, and that surgical treatment should be considered in selected cases.

Combined effects of embolization and hypofractionated conformal stereotactic radiotherapy in arteriovenous malformations of the brain

SUMMARY

There are three major treatment options for cerebral AVMs; surgery, embolization and radiosurgery. Embolization may be effective to reduce the size and density but completely obliterates AVMs only in a minority of cases. Radiosurgery may be an alternative to resection, especially in smaller AVMs. Large AVMs have been considered difficult to treat safely and effectively with single fraction radiosurgery. Hypofractionated conformal stereotactic radiotherapy (HCSRT) alone or in combination with embolization may be an alternative treatment. Embolization may reduce the volume and density of AVMs, followed by HCSRT, allowing a safe delivery of a higher total dose of radiation than possible with a single fraction. Sixteen patients with AVMs were treated with embolization and HCSRT. Embolization was performed in 1-6 (median 2) sessions. HCSRT was delivered in 5 fractions with 6-7 Gy each to the total dose of 30-35 Gy. Cerebral angiographies before and after embolization were digitally compared for calculation of volume reduction and luminescence as a measure of AVM density. The mean AVM volume in 15 patients was reduced from 11.9 +/- 2.1 (1-29, median 10.0) ml to 6.5 +/- 2.0 (0.5-28, median 3) ml by embolization. The luminescence for all AVMs was significantly higher after than before embolization, indicating that all AVMs were less dense after embolization. Thirteen out of 16 patients (13/16, 81%) treated with embolization and HCSRT have so far shown obliteration of their AVMs 2-9 (median 4) years after HCSRT. Three patients experienced neurological sequele after embolization, and three patients developed radionecrosis after HCSRT. Using a new method to compare cerebral angiographies in AVMs we report reduction in density and volume after embolization. The obliteration rate of a combined treatment with embolization and HCSRT seems comparable with single fraction radiosurgery although the AVMs in our series are larger than reported in most series treated with single fraction radiosurgery.

Surgical handling characteristics of an ethylene vinyl alcohol copolymer compared with N-butyl cyanoacrylate used for embolization of vessels in an arteriovenous malformation resection model in swine

OBJECT

There have been significant improvements in neurovascular technology and implants over the past decade. One such material, N-butyl cyanoacrylate (NBCA), is now commercially available for cerebral arteriovenous malformation (AVM) embolization in the US. An ethylene vinyl alcohol copolymer preparation, Onyx, which is currently being evaluated, is approved for use outside North America. Although reports indicate that Onyx may be superior to NBCA from an endovascular perspective, little information exists about its surgical handling characteristics. The purpose of this study was to compare the surgical handling characteristics of Onyx-treated vessels with those of NBCA-embolized vessels in an AVM resection model.

METHODS

Fourteen pigs (two groups of seven) were anesthetized. A femoral artery was cannulated, followed by selective catheterization of the ascending pharyngeal arteries. Nidal rete mirabile (RM) embolizations were performed using either 6% Onyx or 20% NBCA. After angiographically confirmed obliteration of flow in the right RM, microsurgical resection of this structure was performed. Surgical handling characteristics of the embolized RM were rated on a scale of 1 to 5 and blood loss was recorded. Different surgeons performed the embolizations and resections. The surgeon who performed resections was blinded to the embolization agent used, and the data analysis was also performed in a blinded fashion. The surgical handling scores were superior (p < 0.05) in the Onyx-treated group. Although there was also less blood loss in this group, the difference was not significant. Subjectively, the surgeon who performed the resections believed that Onyx was softer and handled better than NBCA.

CONCLUSIONS

Onyx, which may offer endovascular advantages, also seems to provide benefits for the surgeon.

Compartments in arteriovenous malformation nidi demonstrated with rotational three-dimensional digital subtraction angiography by using selective microcatheterization. Report of three cases

Although in several histological studies of arteriovenous malformation (AVM) nidi the presence of compartments has been documented, no clinical study has been published. The present study was conducted to determine the presence of nidus compartments in clinical cases by using a new radiographic method. Two patients with unruptured and one with a ruptured AVM (all Spetzler-Martin Grade III) were studied. A microcatheter was superselectively introduced into each of two or three feeding arteries of the AVMs under three-dimensional (3D) angiographic guidance to obtain 3D images of the nidus by using rotational digital subtraction angiography. On 3D images the different feeding arteries were found to be independent from one another, which allowed the authors to confirm the presence of compartments. On the other hand, separate feeding arteries often had a common draining vessel. Compartments in AVM nidi were demonstrated by a novel rotational 3D angiographic procedure by using superselective microcatheterization, which should be useful for designing treatment strategies for large and complex AVMs.

Arteriovenous malformations

Arteriovenous malformations of the brain are congenital vascular lesions that affect 0.01-0.50% of the population, and are generally present in patients aged 20-40 years. The usual clinical presentations are haemorrhage, seizures, progressive neurological deficit, or headache. Results of natural history studies have shown a yearly haemorrhage rate of 1-4%. Frequency of rebleeding has increased over the years, and several factors that increase risk of haemorrhage have been identified. Although substantial, the morbidity associated with haemorrhages could be less than previously thought. Over the past decade, great advances have been made in application of endovascular embolisation techniques, stereotactic radiosurgery, and microsurgery, allowing effective multidisciplinary treatment of arteriovenous malformations, including those previously deemed to be untreatable. Increasing attention has been paid to management of flow-related aneurysms associated with these malformations. Finally, many reports of recurrent arteriovenous malformations have coincided with new theories regarding the embryogenesis of these disorders and laboratory work suggesting their proliferative potential.

Embolization of arteriovenous malformations prior to radiosurgery

SUMMARY

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.