A mixture of ethylene vinyl alcohol copolymer and ethanol yielding a nonadhesive liquid embolic agent to treat cerebral arteriovenous malformations: initial clinical experience

Combination of Alcohol and EVOH as a New Embolic Agent: Midterm Tissue and Inflammatory Effects in a Swine Model

Objective

To evaluate the vascular occlusion and midterm tissue toxicity properties of a combination of ethylene-vinyl alcohol (EVOH) (Squid 18®) (75%) and alcohol (25%)—Alco-Squid 18—in a swine model.

Materials and Methods

Alco-Squid 18 (75% Squid 18® mixed with 25% alcohol) (AS18) was compared to embolization with 96% alcohol alone and to embolization with Squid 18® (S18®) alone. An arteriovenous malformation (AVM) model was created in group 1 (n = 2). Each AVM model was then embolized with AS18 or S18® alone with evaluation of a ratio between the volume of embolic agent divided by the volume of the AVM (evaluated by CT). For group 2 (n = 5), each agent was tested on three different kidneys (upper pole kidney artery). Pre- and postinterventional CTs, angiographies, blood alcohol content dosages, and histological studies (3 months postintervention) were performed.

Results

AS18 has better distal distribution than S18® alone, both in the kidneys (mean capsule-S18® distance: 3.9 mm (±0.23) and mean capsule-AS18 distance: 2.3 mm (±0.11) (p=0.029) and in the AVM model. Histological exploration found a higher rate of tubular necrosis with AS18 compared with S18® alone and alcohol alone (3.78 ± 0.44 compared to 2.33 ± 1.22 (p = 0.012) and 1.22 ± 0.67 (p  < 0 .0001)). The blood alcohol content was negligible in all cases.

Conclusion

AS18 can suggest a better distal sclerotic and embolic character as compared with S18® alone without systemic toxicity.

The impact of preradiosurgery embolization on intracranial arteriovenous malformations: a matched cohort analysis based on de novo lesion volume

OBJECTIVE

The benefits and risks of pre-stereotactic radiosurgery (SRS) embolization have been reported in different studies. The goal of this study was to compare the long-term outcome of arteriovenous malformations (AVMs) treated with and without pre-SRS embolization.

METHODS

A database including 1159 patients with AVMs who underwent SRS was reviewed. The embolized group was selected by including AVMs with pre-SRS embolization, maximal diameter > 30 mm, and estimated volume > 8 ml. The nonembolized group was defined as AVMs treated by SRS alone with matched de novo nidus volume. Outcomes including incidences of favorable clinical outcome (obliteration without hemorrhage, cyst formation, worsening, or new seizures), obliteration, adverse effects, and angioarchitectural complexity were evaluated.

RESULTS

The study cohort comprised 17 patients in the embolized group (median AVM volume 17.0 ml) and 35 patients in the nonembolized group (median AVM volume 13.1 ml). The rates of obliteration (embolized cohort: 33%, 44%, and 56%; nonembolized cohort: 32%, 47%, and 47% at 4, 6, and 10 years, respectively) and favorable outcome were comparable between the 2 groups. However, the embolized group had a significantly higher incidence of repeat SRS (41% vs 23%, p = 0.012) and total procedures (median number of procedures 4 vs 1, p < 0.001), even with a significantly higher margin dose delivered at the first SRS (23 Gy vs 17 Gy, p < 0.001). The median angioarchitectural complexity score was reduced from 7 to 5 after embolization. Collateral flow and neovascularization were more frequently observed in the embolized nonobliterated AVMs.

CONCLUSIONS

Both embolization plus SRS and SRS alone were effective therapies for moderately large (8-39 ml) AVMs. Even with a significantly higher prescription dose at the time of initial SRS, the embolized group still required more procedures to reach final obliteration. The presence of collateral flow and neovascularization could be risk factors for a failure to obliterate following treatment.

Highlights on Cerebral Arteriovenous Malformation Treatment Using Combined Embolization and Stereotactic Radiosurgery: Why Outcomes are Controversial?

Cerebral arteriovenous malformations (AVMs) are abnormal tangling between brain arteries and veins causing an arteriovenous shunt called nidus with an intervening network of vessels from the region of formation and spans through the brain. AVM effect is debilitating to the affected individual due to associated persistent intracerebral hemorrhage, resulting in significant occurrences of seizures and neurological damage. Recent innovative treatments involve a combination of embolization (Embo) procedures followed by stereotactic radiosurgery (SRS), designed to optimize less-invasive practice for the obliteration of the AVMs. Three groups of investigators reported different outcomes based on obliteration rates and adverse events, making the effectiveness of options for therapy, controversial. We have taken the case-oriented-approach to highlight on varying outcomes from various studies and provide insights as to why findings from different operation settings could be so conflicting. We chose 18 articles for systematic analysis based on initial electronic database selection of 40 key papers already identified for inclusion, followed by independent blinding assessment by two co-authors. Our evaluation was based first on our specific inclusion criteria, examining method quality, obliteration rates, serious adverse events (SAEs) and mortality rates. Second, we made a comparison between SRS or embo alone treatments versus combined embo/SRS procedures, relative to AVM sizes, following Spetzler-Martin (SM) method. Third, we considered publications which had concrete statistics with well-defined P-values and clarified outcomes for accurate evaluation. We found that patients with small to medium-sized AVM were susceptible to either embo alone or SRS alone treatments, yielding obliteration rates from 71%-100%. Except for one report, giant sizes AVMs were not amenable to these single treatments, subjecting patients to embo/SRS procedures, which yielded mixed results: One group reported 52%-65% obliteration rates, compared to 23%-28% embo alone treatment. A second group contradicted this apparent beneficial outcome, obtaining obliteration rates of 53% with combined treatment compared to 71% with SRS alone, four-year postoperative. A third group reported there was no difference between single and combined treatments and obtained complete obliteration of 70%-82%, ranging from three-five-years postoperative follow-up. In all the cases analyzed, obliteration rates improved with time. SAEs, such as persistent hemorrhage and permanent neurologic deficits (P-NDs), as well as mortality, were minimal during intraoperative and postoperative follow-ups. The problem of conflicting outcomes in combined treatments of AVM by EMBO/SRS exists. Previous investigators, however, have overlooked to address this issue satisfactorily. Our analysis found that the reported inconsistencies in AVM treatment outcomes are attributable to key factors making therapy unpredictable, which includes: the size of the AVM, nidus localization and accessibility of either Embo or radiation dose applied, certain Embo materials lowering obliteration rates by masking radioactive effect on the nidus during SRS and follow-up timing for obtaining obliteration rates determine the extent of obliteration. We have indicated critical factors which require consideration when planning strategies for treatment of AVM patients and have made suggestions of how to overcome such hurdles.

Forcible intraarterial injection of a nonadhesive liquid embolic agent under microballoon occlusion: experimental study in swine liver

PURPOSE

To evaluate the feasibility and effectiveness of transcatheter embolization by forcible intraarterial injection of a mixture of ethylene vinyl alcohol copolymer (EVAL) and ethanol under microballoon occlusion compared with conventional transcatheter arterial embolization methods in nontumoral swine liver.

MATERIALS AND METHODS

Nine swine were divided into three groups: embolization with EVAL/ethanol mixture (EVAL group, n = 5), with ethiodized oil (ethiodized oil group, n = 2), and with microspheres (microspheres group, n = 2). Embolization was performed at the subsegmental hepatic artery. The EVAL/ethanol mixture was injected forcibly through a microcatheter with a balloon, which was inflated to prevent backflow of the mixture during the injection. Ethiodized oil or microspheres were injected into the artery using a microcatheter without balloon occlusion. Two animals of the EVAL group were euthanized immediately after embolization, and the distribution of EVAL was assessed microscopically. The remaining seven animals were euthanized 4 weeks after embolization, and the histopathologic changes were assessed.

RESULTS

All procedures were technically successful. EVAL occupied > 80% of the hepatic arterial, portal venous, and sinusoidal lumens after embolization. Ischemic coagulation necrosis was observed 4 weeks after embolization in the EVAL group. Parenchymal necrosis was not observed in the ethiodized oil and microspheres groups.

CONCLUSIONS

Transcatheter embolization by forcible intraarterial injection of an EVAL/ethanol mixture under microballoon occlusion was feasible and achieved the simultaneous embolization of hepatic artery, portal vein, and sinusoids in swine liver, resulting in complete necrosis of the segment that received embolization.

Onyx®: a unique neuroembolic agent

Rupture of a cerebral arteriovenous malformation can result in devastating hemorrhage with a possibility of serious neurological injury or death. Endovascular embolization is an important adjunct in the treatment of cerebral arteriovenous malformations, and in a small number of cases may provide definitive treatment. Currently available embolic agents have several shortcomings, including the possibility of recanalization, adhesiveness to the endovascular microcatheter and suboptimal handling at the time of surgical resection. Onyx is an ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide that was approved by the US FDA in July 2005 as an embolic agent for brain arteriovenous malformations. Although long-term follow-up is limited, this agent appears to offer several advantages over the other available embolic agents for the endovascular management of arteriovenous malformations and other vascular lesions.

The failure of preoperative ethylene-vinyl alcohol copolymer embolization to improve outcomes in arteriovenous malformation management: case series

OBJECT

Ethylene-vinyl alcohol copolymer embolization is increasingly used preoperatively in the resection of brain arteriovenous malformations (AVMs). However, the case for embolization improving the outcome of resection has not been evaluated. In this paper the authors set out to compare outcomes after surgery for brain AVMs in 2 consecutive periods of practice. In the first period, selective embolization was used without the use of ethylene-vinyl alcohol copolymer. In the second period, selective embolization with ethylene-vinyl alcohol copolymer was performed.

METHODS

A consecutive case series (prospectively collected data) was retrospectively analyzed. Adverse outcomes were considered to be an outcome modified Rankin Scale score greater than 2 due to embolization or surgery.

RESULTS

A total of 538 surgical cases were included. The percentages of adverse outcomes were as follows: 0.34% for Spetzler-Martin AVMs less than Grade III (1 of 297 cases); 5.23% (95% CI 2.64%-9.78%) for Grade III AVMs (9 of 172 cases); and 17% (95% CI 10%-28%) for AVMs greater than Grade III (12 of 69 cases). There was no improvement in outcomes from the first period to the second period. The adverse outcome for Grade III brain AVMs in the first period was 5.2% (7 of 135 cases) and in the second period (after ethylene-vinyl alcohol copolymer was introduced) it was 5.4% (2 of 37 cases). For AVMs greater than Grade III, the adverse outcome was 12% (6 of 49 cases) in the first period and 30% (6 of 20 cases) in the second period.

CONCLUSIONS

Outcomes for brain AVM surgery were not improved by ethylene-vinyl alcohol copolymer embolization. Preoperative embolization of high-grade AVMs with an ethylene-vinyl alcohol copolymer did not prevent those hemorrhagic complications which embolization is hypothesized to prevent based on theoretical speculations but not demonstrated in practice.

Double Arterial Catheterization Technique for Embolization of Brain Arteriovenous Malformations With Onyx

BACKGROUND:

Arteriovenous malformation (AVM) treatment is multidisciplinary, and the patient may undergo embolization, neurosurgery, or radiosurgery combined. Great improvement in endovascular techniques was provided by the introduction of Onyx with different kinds of approach.

OBJECTIVE:

To evaluate the efficacy and the safety of Onyx embolization of brain AVMs with the double arterial catheterization technique (DACT).

METHODS:

This was a retrospective study. From January 2006 until June 2011, 61 AVMs eligible for the DACT were treated. Forty-one of the 61 AVMs were treated with single arterial catheterization technique and 20 of 61 with DACT; patient age and Spetzler-Martin AVM grade were similar in the 2 groups.

RESULTS:

In the DACT group, we obtained complete occlusion of the nidus in all small AVMs, whereas in the single arterial catheterization technique group, we obtained complete occlusion in only 1 of the 36% of the cases. Among the medium-size AVMs, there were no significant differences in the 2 groups, but we performed fewer procedures per patient when we used the DACT (1.4 vs 2.2). In the DACT group, we observed fewer hemorrhagic complications (3.4% vs 12.5% per procedure) and lower morbidity (5% vs 7% per patient) and mortality (0% vs 2.4%) rates.

CONCLUSION:

The DACT in multifeeder AVMs may lead to a higher occlusion rate of the nidus for small AVMs and reduce the number of procedures, ensuring a higher standard of safety because of the possibility of managing the progression of Onyx into venous drainage.

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.

The use of Onyx for embolization of central nervous system arteriovenous lesions in pediatric patients

BACKGROUND AND PURPOSE

The safety and efficacy of Onyx for the embolization of central nervous system (CNS) arteriovenous (AV) lesions have been widely reported in adults. However, data describing the use of this agent in children are limited. This study presents our experience with Onyx in the treatment of CNS AV lesions in pediatric patients.

MATERIALS AND METHODS

We retrospectively analyzed clinical and imaging records of 15 pediatric patients who underwent 36 transarterial embolizations by using Onyx for CNS AV lesions, from March 2007 through April 2009 at our institution. Underlying pathologies included brain AV malformations (AVMs) (n = 7), vein of Galen malformations (n = 4), dural AV fistulas (n = 2), and spinal AVMs (n = 2). For 7 procedures in very high-flow lesions, detachable coils were deployed before Onyx embolization, whereas in 29 procedures, Onyx was the sole embolic agent. The efficacy of embolization was judged by the residuum of AV shunting within the target region.

RESULTS

Embolization was complete in 2 patients, nearly complete in 9 patients, and partial (and ongoing) in 4 patients. Following staged embolization, 7 patients underwent surgical resection without significant blood loss and with good functional outcome in all cases. Clinically silent non-target embolization was encountered in 2 of 36 procedures. After 3 of the 36 embolizations, patients developed transient neurologic symptoms, all of which resolved to baseline within 24 hours. There were no non-neurologic adverse events. There was no imaging evidence of infarct or hemorrhage.

CONCLUSIONS

Onyx embolization of pediatric CNS AV lesions can be an efficacious treatment technique, with extremely low associated morbidity.

Histopathological changes in brain arteriovenous malformations after embolization using Onyx or N-butyl cyanoacrylate

Object

The aim of this study was to analyze the histopathological changes in a consecutive series of 32 patients with brain arteriovenous malformations that were resected after undergoing endovascular embolization (22 using Onyx and 10 using N-butyl cyanoacrylate [NBCA]).

Methods

Selections from fixed paraffin-embedded specimens were stained for histological examination with H & E and Verhoeff-van Gieson stain. Lipid dye Oil Red O was used to stain vessel specimens that were embolized using NBCA. Specimens were evaluated for the presence of embolic agent, inflammation, angionecrosis, and evidence of recanalization. These results were correlated with the time interval between the bleeding, embolization, and resection.

Results

The smallest vessel occluded by the embolic agent was 5 μm in the Onyx group and 20 μm in the NBCA group. There was evidence of vascular or perivascular inflammation in 20 (90.9%) of 22 and 9 (90%) of 10 specimens after Onyx and NBCA embolization, respectively. Chronic foreign-body giant cells were observed in 12 (54.5%) of 22 specimens after Onyx embolization, but were absent in specimens after NBCA embolization. Angionecrosis of the embolized vessel was observed in 13 (59.1%) of 22 specimens and in 4 (40%) of 10 specimens after Onyx and NBCA embolization, respectively. There was evidence of recanalization in Onyx embolized vessels in 4 (18.2%) of 22 specimens, and there was no evidence of recanalization after NBCA embolization.

Conclusions

Onyx penetrates much smaller vessels than NBCA. Inflammation occurs with both embolic agents at equal frequency. Evidence of chronic foreign-body giant cells and recanalization after Onyx embolization shows a long-standing reaction to Onyx and raises questions about the permanence of occlusion after Onyx embolization.

Challenging traditional beliefs: microsurgery for arteriovenous malformations of the basal ganglia and thalamus

OBJECTIVE

Arteriovenous malformations of the basal ganglia and thalamus are often managed with radiosurgery or observation, without consideration of microsurgery. Given the devastating effects of hemorrhage from these lesions, the accumulating evidence that they bleed more frequently than their lobar counterparts should prompt more creative thinking regarding their management.

METHODS

A review of the endovascular, microsurgical, and radiosurgical literature for arteriovenous malformations of the basal ganglia and thalamus was performed, with close attention to surgical approaches, obliteration rates, and procedure-related complications.

RESULTS

A complete resection rate of 91% and a mortality rate of 2.4% were found across surgical series of these lesions. These contrast with a 69% rate of complete obliteration and a 5.3% mortality rate (from latency-period hemorrhage) found when compiling results across the radiosurgical literature.

CONCLUSION

Given an appropriate surgical corridor of access, often afforded by incident hemorrhage, arteriovenous malformations of the basal ganglia and thalamus should be considered for microsurgical extirpation with preoperative embolization. In experienced hands, this approach presents an expeditious and definitive opportunity to eliminate the risk of subsequent hemorrhage and resultant morbidity and mortality.

Preoperative embolization of cerebral arteriovenous malformations with onyx

BACKGROUND AND PURPOSE

Preoperative embolization facilitates the surgical management of complex cerebral arteriovenous malformations (cAVMs). This analysis aims to investigate the risks for preoperative cAVM embolization with Onyx.

MATERIALS AND METHODS

We retrospectively analyzed clinical data of all patients who underwent embolization with Onyx as a preoperative treatment of cAVMs at our institution since 2005 (US Food and Drug Administration [FDA] approval). Patients with arteriovenous fistulas were excluded. A total of 107 patients were treated for cAVMs during the study period. Of those patients, 41 underwent cAVM embolizations with Onyx in 82 procedures.

RESULTS

After the embolization, the cAVM diameter was reduced from 3.71 +/- 1.55 cm to 3.06 +/- 1.89 cm (P < .05). Median volume reduction was 75%. Complete occlusion with embolization alone was achieved in 4 (10%) cAVMs. The recurrence rate for completely occluded cAVMs was 50% (2 patients). A total of 71% of the 41 patients treated with Onyx underwent surgery, and 15% underwent radiosurgery. There were 9% who have not yet received definitive treatment of their residual cAVMs. A new permanent neurologic deficit occurred in 5 patients (6.1% per procedure or 12.2% per patient).

CONCLUSIONS

A considerable risk for a permanent neurologic deficit remains for cAVM embolization with Onyx. The risk has to be carefully weighted against the benefit of volume reduction in the treatment of cAVMs.

[Transarterial embolization of intracranial dural arteriovenous malformations with ethylene vinyl alcohol copolymer (Onyx18): report of three cases]

BACKGROUND

This is a report of the endovascular treatment of three intracranial dural arteriovenous malformations (DAVM) using Onyx.

PATIENTS AND METHODS

We analyzed the clinical and angiographic results in three patients with intracranial DAVM, revealed by a hemorrhagic event and treated by endovascular way by the use Onyx. Angiographic investigation showed the DAVM to be located in the lateral sinus in two cases and in the tentorium region in the third.

RESULTS

In all three cases, embolization was performed by selective catheterization of the meningeal arterial feeder of the DAVM. The injection of Onyx resulted in complete anatomical exclusion of the DAVM, as demonstrated by posttreatment angiography. Clinically, the patients recovered partially or completely their neurological deficit.

CONCLUSION

Onyx is a liquid embolization agent recently introduced for the treatment of DAVM. When used under optimal conditions, it offers a feasible alternative option in the treatment of such vascular malformations.

Comparison of N-Butyl Cyanoacrylate and Onyx for the Embolization of Intracranial Arteriovenous Malformations: Analysis of Fluoroscopy and Procedure Times

Objective:

Intracranial arteriovenous malformations (AVM) may be managed through staged preoperative embolization and resection. Two commonly used liquid embolics are N-butyl cyanoacrylate (nBCA; Cordis Microvascular, Inc., New Brunswick, NJ) and Onyx (ev3, Inc., Irvine, CA). We sought to compare the utility of these agents in terms of fluoroscopy and procedure times.

Methods:

All intracranial AVMs embolized from 2002 to 2006 at the University of Florida were included in this study. Patients were stratified into three treatment groups: nBCA, Onyx, and patients who received both nBCA and Onyx during separate embolizations. Cohorts were compared by sex, age, Spetzler-Martin grade, AVM volume, fluoroscopy time, procedure time, surgical blood loss, and complications.

Results:

A total of 182 embolizations were performed on 88 patients (nBCA, 60 patients and 106 procedures; Onyx, 20 patients and 43 procedures; and nBCA/Onyx, eight patients and 16 nBCA and 17 Onyx procedures). There were no significant differences in patient demographics, AVM volumes, and Spetzler-Martin grades. Mean fluoroscopy and procedure times were increased for Onyx (57 min; 2.6 h) compared with nBCA (37 min; 2.1 h) embolizations (P &lt; 0.0001 and P = 0.001, respectively). Cumulative mean fluoroscopy time was increased for Onyx (135 min) and nBCA/Onyx (180 min) cohorts relative to nBCA (64 min; P &lt; 0.0001). Cumulative mean procedure time was increased in the nBCA/Onyx group (10.4 h) compared with nBCA (3.7 h) and Onyx (5.4 h; P&lt; 0.0001). Seventy patients (80%) underwent AVM resection. No significant differences in surgical blood loss or complication rates were observed among the cohorts.

Conclusion:

Onyx AVM embolization requires increased fluoroscopy and procedure times compared with nBCA. Further investigation is necessary to justify increased radiation exposure and procedure time associated with Onyx.

PREOPERATIVE EMBOLIZATION OF INTRACRANIAL ARTERIOVENOUS MALFORMATIONS WITH ONYX

OBJECTIVE

Preoperative embolization in accordance with multimodal therapies for cerebral arteriovenous malformations (AVMs) is generally the first step in treatment and may result in complete obliteration. The Onyx liquid embolic system (Micro Therapeutics, Inc., Irvine, CA) may offer advantages for intranidal targeted embolization and microsurgical resection. We present our experience in the combined treatment of intracranial AVMs using Onyx embolization and neurosurgical resection.

METHODS

We treated a total of 47 patients for compact intracranial AVMs that were located in the frontal or frontoparietal area (16 patients); temporal, temporoparietal, or temporo-occipital regions (12 patients); parietal or parieto-occipital areas (8 patients); occipital regions (8 patients); had basal ganglia involvement (2 patients); and was cerebellar (1 patient). The Spetzler-Martin grading scale values were as follows: 25 patients were Grades I or II, 10 patients were Grade III, and 12 patients were Grades IV or V. Twenty-three AVMs were located in eloquent brain regions.

RESULTS

After we performed final embolizations, the mean nidus reduction was 84%. Seven patients had new, nondisabling neurological deficits, and four patients had new, disabling neurological deficits after embolization. Periprocedurally, five vessel perforations and four stuck microcatheters were encountered without clinical deficits. In two patients, delayed hemorrhage after embolization occurred with good clinical outcome. We completely resected 46 AVMs; in one patient, we detected an AVM on postoperative angiography. The mean operative time was 4.7 hours, and the mean blood loss was 455 mL. Clinical status worsened postoperatively in 14 patients. Angiographic and clinical follow-up examinations were available for 42 patients (89%); the average follow-up period was 13 months. We found no relapse of arteriovenous shunt. Fourteen patients improved clinically after discharge. Of the 42 patients followed up, 23 individuals had no neurological deficit, 16 had a nondisabling deficit, and three had a disabling deficit.

CONCLUSION

Preoperative use of the Onyx liquid embolic system in cerebral AVM treatment allows profound occlusion by targeted embolization and provides a basis for safe neurosurgical resection.

[Transarterial embolisation of intracranial dural arteriovenous malformations with ethylene vinyl alcohol copolymer (Onyx18)]

OBJECTIVE

To report our recent experience in transarterial embolisation of dural arteriovenous malformations (DAVM) using a new liquid embolic agent, Onyx18.

PATIENTS AND METHODS

6 patients were enrolled in this series. Clinical presentation was separated into 2 groups: aggressive (n=2), non aggressive (n=4). The DAVM was located at the superior sagittal sinus (n=1), at the transverse sinus (n=2), at the condylian canal (n=1), in the lesser sphenoid wing region (n=1), and in the tentorium region (n=1). The DAVM drained directly into a condylian or a cortical vein for three patients and into a venous sinus with cortical venous reflux for the three others. In this latter situation, the sinus was anatomically excluded from the normal brain venous drainage.

RESULTS

A full brain angiogram including both internal carotid arteries, both external carotid arteries and ipsilateral vertebral artery, was performed before and after each treatment. The feeder chosen after a selective catheterisation for Onyx18 injection was always meningeal. Each treatment consisted of a single Onyx injection after one unique feeder catheterisation. Complete anatomical exclusion of the DAVM was achieved and demonstrated by the post treatment angiogram in all cases. There was no clinical complication after the treatment.

CONCLUSION

Onyx18 used is a safe treatment for DAVMs. When its injection is performed in optimal conditions, it fills the total DAVM and its drainage vein or sinus after a single arterial feeder catheterisation.

Endovascular Treatment of Cerebral Arteriovenous Malformations

The modern management of cerebral arteriovenous malformations (AVMs) is based on three therapeutic modalities: microneurosurgery, endovascular embolization, and stereotactic radiosurgery. Embolization facilitates subsequent radiosurgery by reducing the volume of the nidus, prepares the resection of surgically accessible AVMs, and immediately addresses the risks related to associated intra/extranidal aneurysms and arteriovenous fistulas. We discuss in this article the current state of AVM endovascular therapy.

Biomaterials Used in Injectable Implants (Liquid Embolics) for Percutaneous Filling of Vascular Spaces

The biomaterials currently used in injectable implants (liquid embolics) for minimally invasive image-guided treatment of vascular lesions undergo, once injected in situ, a phase transition based on a variety of physicochemical principles. The mechanisms leading to the formation of a solid implant include polymerization, precipitation and cross-linking through ionic or thermal process. The biomaterial characteristics have to meet the requirements of a variety of treatment conditions. The viscosity of the liquid is adapted to the access instrument, which can range from 0.2 mm to 3 mm in diameter and from a few centimeters up to 200 cm in length. Once such liquid embolics reach the vascular space, they are designed to become occlusive by inducing thrombosis or directly blocking the lesion when hardening of the embolics occurs. The safe delivery of such implants critically depends on their visibility and their hardening mechanism. Once delivered, the safety and effectiveness issues are related to implant functions such as biocompatibility, biodegradability or biomechanical properties. We review here the available and the experimental products with respect to the nature of the polymer, the mechanism of gel cast formation and the key characteristics that govern the choice of effective injectable implants.

A nonadhesive liquid embolic agent composed of ethylene vinyl alcohol copolymer and ethanol mixture for the treatment of cerebral arteriovenous malformations: experimental study

OBJECT

The authors have developed a mixture of ethylene vinyl alcohol copolymer (EVAL) and iopamidol, which is dissolved in ethanol, as an alternative solvent to provide a safe means of embolizing arteriovenous malformations (AVMs).

METHODS

A two-stage delivery technique is required to prevent premature precipitation in the catheter when using this material: the catheter is first infused with 30% ethanol and this is followed by the delivery of the EVAL-ethanol mixture. Acute angiographic changes were analyzed after superselective delivery of dimethyl sulfoxide (DMSO) and 30% ethanol into the renal artery of rabbits. Histological changes following the embolization of the renal artery achieved using the EVAL-ethanol mixture were recorded at 1 hour and at 2 and 16 weeks after the procedure. Although DMSO always produced severe, rapidly progressive vasospasm in the renal artery during a 1- to 60-minute postinfusion, 30% ethanol did not. Microscopically, the lumens of embolized vessels examined 1 hour after embolization with EVAL-ethanol appeared to be filled with EVAL sponges, leaving almost no open spaces. The space between the EVAL sponges and the inner surface of the vessels was filled with fresh thrombus. In the vessel walls of specimens examined 2 weeks after embolization there was no or a slight inflammatory reaction. Scattered in the EVAL sponges were almost equal numbers of neutrophilic granulocytes and mononuclear cells, indicative of a mild inflammatory response. In specimens examined 16 weeks postembolization, the changes noted at 2 weeks were intensified. There was no definite histopathological evidence of mural hemorrhage, perivascular extravasation of the mixture, or perivascular hemorrhage in any specimen that was examined.

CONCLUSIONS

Although the degree of permanence of this embolization material is yet unknown, the mixture was easy to handle, and appeared safe and effective for AVM embolization. Its nonadhesive characteristic and its ability to be infused by repeated injections make it an attractive alternative to currently available materials. The good results obtained in this study led us to undertake a clinical trial, the results of which are contained in a companion article in this issue of the Journal of Neurosurgery.