The combined management of cerebral arteriovenous malformations. Experience with 100 cases and review of the literature

The 100 most cited articles in the endovascular treatment of brain arteriovenous malformations

BACKGROUND:

The literature base for endovascular treatment of brain arteriovenous malformations (BAVMs) has grown exponentially in recent decades. Bibliometric analysis has been used to identify impactful articles in other medical specialties. The aim of this citation analysis was to identify and characterize the top 100 most cited articles in the field of endovascular BAVM treatment.

METHODS:

The top-cited papers were identified by searching selected keywords (“endovascular treatment,” “interventional treatment,” “brain arteriovenous malformation,” “emboliz(s)ation”) on the Web of Science platform. The top 100 articles were ranked according to their number of citations. Each article was further evaluated to obtain predefined characteristics including citation(s) per year, year of publication, authorship, journal-title and impact factor, article topics, article type, and level of evidence.

RESULTS:

The top 100 most cited articles for endovascular BAVM treatment were published between 1960 and 2014. The total number of citations for these articles ranged from 56 to 471 (median 85.5). Most articles (76%) were published between 1990 and 2009 in three journals (56%), originated in the USA (52%) followed by France (16%). The most common topic related to embolization agents and the majority of articles constituted level IV or V evidence.

CONCLUSIONS:

This study provides a comprehensive overview of the most cited articles in the field of endovascular BAVM treatment. Our analysis recognizes key contributions from authors and institutions in the field and leads to a better understanding of the evidentiary framework for BAVM treatment.

The Role of Preradiosurgical Embolization in the Management of Grades III, IV, and V Arteriovenous Malformations

Objective

To evaluate the role of preradiosurgical embolization on obliteration rate, reduction of size, irradiation dose, and neurological outcome, in 90 patients presenting large arteriovenous malformations (AVMs).

Methods

Between October 1993 and October 2006, 90 radiosurgical procedures were performed to treat brain AVMs Spetzler–Martin (SM) grades III, IV, and V at the Department of Radiosurgery and Radiology of the Real e Benemérita Associação Portuguesa de Beneficência de São Paulo, São Paulo, Brazil. Fifty-nine patients had embolization before radiosurgery and complete clinical and radiologic follow-up for at least 3 years. Inclusion criteria were as follow: SM grades III, IV, and V AVMs, no previous treatment, and clinical and radiological (angiogram and MRI) follow-up for at least 3 years. Obliteration rate, reduction of size, irradiation dose, and neurological outcome were compared in these two cohorts of patients. Mann–Whitney test, “Student’s t-test,” and χ² tests were used for statistical analysis, as appropriate. The level of significance was determined at p < 0.05.

Results

The mean size of the AVMs that underwent embolization was significantly greater when compared with non-embolized group (p < 0.05). Embolization significantly reduced the AVM diameter. Irradiation dose was significantly smaller in the embolized group (p < 0.05). No significant differences in final clinical outcomes, postprocedural radiological findings, rate of occlusion, and need for additional procedures were observed between the two groups (p < 0.05).

Conclusion

Preradiosurgical embolization of large AVMs does not result in impaired obliteration rate compared with cases treated with radiosurgery alone. It did not add further morbidity and presented benefits of reducing size of the AVMs. Preradiosurgical embolization may facilitate the coverage of the AVM with the effective irradiation dose. Combined management may be effective for selected large lesions considered unsuitable for radiosurgery and otherwise untreatable.

Comparative surgical outcome associated with the management of brain arteriovenous malformation in a regional neurosurgical centre

OBJECTIVES

Microsurgical resection of brain arteriovenous malformation (AVMs) is challenging, however, expert surgical series from large volume centres, have reported over 95% occlusion rates with 2 to 8% risk of morbidity & mortality. Data from a regional neurosurgical unit was analysed and compared with published series for the purposes of quality control. We also compared our surgical result with other treatment modalities from the whole AVM cohort managed over the same study period.

DESIGN

Retrospective analysis of a locally held AVM database.

SUBJECTS

Of the 141 AVM patients, 54 (35M, 19F, age range 9-68 years) underwent microsurgical removal of AVM by the senior author, from 2006 to 2012. 27 (19%), 18 (13%), 20 (14%), 22 (16%) had endovascular therapy only, radiosurgery only, combination therapy (endovascular and radiosurgery) and conservative management, respectively.

METHODS

Case notes were reviewed to determine clinical and radiological outcomes. Statistical analysis performed using SPSS with p < 0.05 defined as statistical significance.

RESULTS

In the surgical series, the Spetzler-Martin (SM) grade distribution was as follows: 17 grade I (32%), 31 grade II (57%), and 6 grade III (11%). 31 patients (57%) presented with intracranial haemorrhage, 12 patients (22%) with seizures. Of the 54 patients, 51 (94%) had angiographically confirmed obliteration of their AVM. Median follow-up for the entire cohort was 7 years. 83% of surgical patients have mRS 0-1, compared to 78%, 67%, 45%, 18% of patients managed by endovascular therapy, radiosurgery, combination therapy, conservative surveillance, respectively (p < 0.0001). However, the groups were not comparable in terms of SM grade or clinical presentation and the numbers in each group were relatively small. Seizure presentations were encountered in 23% (32/141) of the overall patients, and all the surviving patients were on anticonvulsants, except in the surgical arm, 7/12 (58%) patients were off their antiepileptic medications at last follow-up.

CONCLUSIONS

The results demonstrate a 94% surgical obliteration rate and 11% long-term neurological deficits for brain AVM patients managed surgically and were comparable to expert series. Achieving acceptable results is possible in lower volume settings, however, patient selection is important and the role of an experienced neurovascular team cannot be overstated.

Radiosurgery following Embolisation and/or Surgery of Brain AVM's

A series of 45 patients who have undergone combined treatment for cerebral arteriovenous malformations (AVM's) is presented. All patients underwent additional radiosurgery after endovascular and/or surgical treatment. Stereotactic radiosurgical treatment using the Gamma knife has been available in our institution since 1992.

The treatment strategy for brain AVM's has changed since that time. The possibility for total cure of partially embolised AVM's, where other treatment options had been exhausted, increased with adjunctive radiosurgery. Complex or giant AVM's in eloquent areas can now be treated using radiosurgery after embolisation and/or microsurgery, with minor risk of neurological deficit.

In all 45 patients treated since September 1992 at the University of Vienna, embolisation was performed to reduce the size of the nidus in order to facilitate surgical resection or radiosurgical treatment.

In 37 patients radiosurgery was performed after endovascular treatment only, and in 8 patients radiosurgery was performed after embolisation and surgery. All AVM's were classified according to Spetzler's Grading System. 31 patients (68.9%) were classified as Grade 3 or 4. Two patients (4.5%) were classified as Grade 5.

In a mean follow up time of 16 months (range 2–40), there were 15 complete obliterations and 2 patients with unexpected residual AVM after two years.

Of patients who required staged radiosurgical therapy, 12 have been followed for less than two years after their final procedure. In an additional 12 patients the follow-up period is less than 12 months. 4 patients were lost to follow up. There is a morbidity of 8.8% and no mortality in this patient group.

Efficacy of Diluted NBCA Mixture for Embolization of Arteriovenous Malformations

The purpose of this study is to evaluate the efficacy and problems of the embolization for cerebral arteriovenous malformations (AVMs) with diluted cyanoacrylate adhesives.

Twelve consecutive AVM cases were treated with N-butyl-2-cyanoacrylate (NBCA) glues between January 1997 and July 1998. The mean age of the patients was 37 years old. Intracerebral hemorrhage was the presenting symptom in seven cases, seizure in three, headache in one and mental deterioration in one. According to the classification of Spetzler and Martin, seven were Grade 11, five were Grade III. We used a mixture of NBCA (normally 25% Histoacryl, 75% Ethidol) for embolization. Microcatheter was navigated into the nidus and the tip of the catheter was set in a wedged position. Then the glue was injected using complete column technique.

Nineteen sessions of embolization were performed in 12 patients. The mean volume of each nidus was reduced from 22.5 ml to 3.4 ml (85%) after embolization. Four cases were cured by embolization alone. Surgical resection was performed after embolization without any residual nidus in three cases. Five were treated with stereotactic radiosurgery following embolization. One was completely cured in 18 months after and the other four have been decreasing their sizes of nidus. One case was suffered from delayed intracerebral hemorrhage three days after embolization, and resulted in mild hemiparesis and memory disturbance. The others had no complications and were clinically improved or unchanged after embolization.

It is possible to embolize the nidus of AVMs more accurately and safely with diluted mixture of NBCA, compared with the method using relatively higher concentration of NBCA glues. This technique is useful and effective method for the treatment of AVMs.

Brain arteriovenous malformations

An arteriovenous malformation is a tangle of dysplastic vessels (nidus) fed by arteries and drained by veins without intervening capillaries, forming a high-flow, low-resistance shunt between the arterial and venous systems. Arteriovenous malformations in the brain have a low estimated prevalence but are an important cause of intracerebral haemorrhage in young adults. For previously unruptured malformations, bleeding rates are approximately 1% per year. Once ruptured, the subsequent risk increases fivefold, depending on associated aneurysms, deep locations, deep drainage and increasing age. Recent findings from novel animal models and genetic studies suggest that arteriovenous malformations, which were long considered congenital, arise from aberrant vasculogenesis, genetic mutations and/or angiogenesis after injury. The phenotypical characteristics of arteriovenous malformations differ among age groups, with fistulous lesions in children and nidal lesions in adults. Diagnosis mainly involves imaging techniques, including CT, MRI and angiography. Management includes observation, microsurgical resection, endovascular embolization and stereotactic radiosurgery, alone or in any combination. There is little consensus on how to manage patients with unruptured malformations; recent studies have shown that patients managed medically fared better than those with intervention at short-term follow-up. By contrast, interventional treatment is preferred following a ruptured malformation to prevent rehaemorrhage. Management continues to evolve as new mechanistic discoveries and reliable animal models raise the possibility of developing drugs that might prevent the formation of arteriovenous malformations, induce obliteration and/or stabilize vessels to reduce rupture risk. For an illustrated summary of this Primer, visit: http://go.nature.com/TMoAdn.

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.

Endovascular management of arteriovenous malformations of the brain

Arteriovenous malformations (AVMs) of the brain are rare, complex, vascular lesions that can result in significant morbidity and mortality. Modern treatment of brain AVMs is a multimodality endeavor, requiring a multidisciplinary team with expertise in cerebrovascular neurosurgery, endovascular intervention, and radiation therapy in order to provide all therapeutic options and determine the most appropriate treatment regimen depending on patient characteristics and AVM morphology. Current therapeutic options include microsurgical resection, radiosurgery (focused radiation), and endovascular embolization. Endovascular embolization is primarily used as a preoperative adjuvant before microsurgery or radiosurgery. Palliative embolization has been used successfully to reduce the risk of hemorrhage, alleviate clinical symptoms, and preserve or improve neurological function in inoperable or nonradiosurgical AVMs. Less frequently, embolization is used as 'primary therapy' particularly for smaller, surgically difficult lesions. Current embolic agents used to treat brain AVMs include both solid and liquid agents. Liquid agents including N-butyl cyanoacrylate and Onyx are the most commonly used agents. As newer embolic agents become available and as microcatheter technology improves, the role of endovascular treatment for brain AVMs will likely expand.

Predictors of total obliteration in endovascular treatment of cerebral arteriovenous malformations

Endovascular therapy is a therapeutic option that can achieve total obliteration of cerebral arteriovenous malformations (AVMs). The objective of this study was to determine the predictive factors of total obliteration in the endovascular treatment of AVMs. A prospective study was carried out in 71 patients with cerebral AVMs having undergone 147 embolization sessions with n-BCA, performed between 2006 and 2011. A univariate analysis was carried out, followed by a logistic regression analysis to determine the predictive factors of total obliteration. Total obliteration was achieved in 18.3% of the patients and angiographic control after 12 months showed the permanency of total occlusion in 100% of the AVMs with initial total obliteration. Angiographic characteristics found favorable for total eradication were: AVM size under 3 cm and the presence of a single arterial pedicle. Predictive factors of total obliteration were an AVM diameter smaller than 3 cm (OR: 50.9; IC: 7.41 - 349, 0; P = 0.000), and opposing factors, a 3-6 cm diameter (OR: 11.7; IC: 2.49 - 55, 4; P = 0.002) and afferences of more than two vessels of the Willis polygon (OR: 7.0; IC: 1.12-43.9; P = 0.038). An AVM diameter smaller than 3 cm is a predictive factor of total obliteration. Total postembolization obliteration persisted in 100% of the cases after 12 months.

Advances in Radiosurgery for Arteriovenous Malformations of the Brain

Arteriovenous malformations of the brain are a considerable source of morbidity and mortality for patients who harbor them. Although our understanding of this disease has improved, it remains in evolution. Advances in our ability to treat these malformations and the modes by which we address them have also improved substantially. However, the variety of patient clinical and disease scenarios often leads us into challenging and complex management algorithms as we balance the risks of treatment against the natural history of the disease. The goal of this article is to provide a focused review of the natural history of cerebral arteriovenous malformations, to examine the role of stereotactic radiosurgery, to discuss the role of endovascular therapy as it relates to stereotactic radiosurgery, and to look toward future advances.

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.

Treatment for brain arteriovenous malformation in the 1998-2011 period and review of the literature

PURPOSE

The results of the treatment of pial AVM provided at our neurosurgical centre are presented. Based on these results and on an overview of literary data on the efficacy and complications of each therapeutic modality, the algorithm of indications, as used at our institution, is presented. COHORT OF PATIENTS: The series comprises 195 patients, aged 9 to 87 years and treated in the years 1998-2011. The surgical group consists of 76 patients; of these, 49 patients solely received endovascular treatment, 25 were consulted and referred directly to the radiosurgical unit, and the remaining 45 were recommended to abide by the strategy of "watch and wait".

RESULTS

In the surgical group, serious complications were 3.9 %, at a 96.1 % therapeutic efficacy. As for AVM treated with purely endovascular methods, serious procedural complications were seen in 4.1 % of patients, with efficacy totalling 32.7 %. One observed patient suffered bleeding, resulting in death. For comparison with literary data for each modality, a survival analysis without haemorrhage following monotherapy for AVM with each particular modality was carried out.

CONCLUSIONS

Based on our analysis, we have devised the following algorithm of treatment: 1. We regard surgical treatment as the treatment of choice for AVM of Spetzler-Martin (S-M) grades I and II, and only for those grade III cases that are surgically accessible. 2. Endovascular intervention should mainly be used for preoperative embolisation, as a curative procedure for lower-grade AVM in patients with comorbidities, and as palliation only for higher-grade cases. 3. Stereotactic irradiation with Leksell Gamma Knife (LGK) is advisable, mainly for poorly accessible, deep-seated grade-III AV malformations. In the case of lower grades, the final decision is left to the properly informed patient. 4. Observation should be used as the method of choice in AVM of grades IV and V, where active therapy carries greater risk than the natural course of the disease.

Surgical and radiosurgical results of the treatment of cerebral arteriovenous malformations

Microsurgical resection of a cerebral arteriovenous malformation (AVM) allows for an immediate therapeutic cure. Stereotactic radiosurgery (SRS) is a reasonable alternative for inoperable or high-risk lesions requiring treatment. Few series evaluate overall results that include data from both modalities as they more often focus on their treatment method of choice. In this study, we evaluated our AVM database of 129 patients seen over the past eight years at our institution: 73 were treated with microsurgery (57%) while 37 (29%) were treated with SRS. We reviewed angiographic obliteration rates, complication rates, and outcome data, excluding seven patients treated with SRS as they did not have at least two years of angiographic follow-up. Patients undergoing microsurgery had smaller AVM (mean 2.2 cm compared to 3.5 cm for SRS), a smaller proportion of eloquent AVM (53% compared to 83% for SRS), a greater proportion of AVM with superficial drainage only (75% compared to 40% for SRS), and more grade 1 and 2 AVM (78% compared to 17% for SRS). The overall obliteration rate was 80%: 92% for microsurgery and 50% for SRS. The latter increased to 92% for AVM <3 cm, but the obliteration rate was 18% for those AVM >3 cm. Transient complications, including post-SRS hemorrhage, were seen in 11% of patients overall (8% after microsurgery, 17% after SRS). At follow-up, 53% of patients had improved, 37% remained the same, 7% had become worse and 3% had died. As a result of post-SRS hemorrhage, a greater proportion of patients was worse or had died after SRS (20%) compared to those who had been treated with microsurgery (5%).

Gamma Knife surgery for basal ganglia and thalamic arteriovenous malformations

Object

Gamma Knife surgery (GKS) has emerged as the treatment of choice for small- to medium-sized cerebral arteriovenous malformations (AVMs) in deep locations. The present study aims to investigate the outcomes of GKS for AVMs in the basal ganglia and thalamus.

Methods

Between 1989 and 2007, 85 patients with AVMs in the basal ganglia and 97 in the thalamus underwent GKS and were followed up for more than 2 years. The nidus volumes ranged from 0.1 to 29.4 cm3 (mean 3.4 cm3). The mean margin dose at the initial GKS was 21.3 Gy (range 10–28 Gy). Thirty-six patients underwent repeat GKS for residual AVMs at a median 4 years after initial GKS. The mean margin dose at repeat GKS was 21.1 Gy (range 7.5–27 Gy).

Results

Following a single GKS, total obliteration of the nidus was confirmed on angiograms in 91 patients (50%). In 12 patients (6.6%) a subtotal obliteration was achieved. No flow voids were observed on MR imaging in 14 patients (7.7%). Following single or repeat GKS, total obliteration was angiographically confirmed in 106 patients (58.2%) and subtotal obliteration in 8 patients (4.4%). No flow voids on MR imaging were observed in 18 patients (9.9%). The overall obliteration rates following one or multiple GKSs based on MR imaging or angiography was 68%. A small nidus volume, high margin dose, low number of isocenters, and no history of embolization were significantly associated with an increased rate of obliteration. Twenty-one patients experienced 25 episodes of hemorrhage in 850 risk-years following GKS, yielding an annual hemorrhage rate of 2.9%. Four patients died in this series: 2 due to complications of hemorrhage and 2 due to unrelated diseases. Permanent neurological deficits caused by radiation were noted in 9 patients (4.9%).

Conclusions

Gamma Knife surgery offers a reasonable chance of obliterating basal ganglia and thalamic AVMs and does so with a low risk of complications. It is an optimal treatment option in patients for whom the anticipated risk of microsurgery is too high.

The place for surgical treatment for AVM involving the temporal lobe

OBJECTIVE

The objective of this study was to analyze preoperative symptoms and late clinical outcomes in patients who underwent surgical treatment of arterio-venous malformations (AVMs) of the temporal lobe, including those involving the Sylvian fissure (SF) and the lateral wall of the inferior ventricular horns-with special respect to postoperative hemiparesis and visual field defects (VFD).

METHODS

Between 1990 and 2007, 44 patients (n = 22 women, n = 22 men) with a mean age of 41 (12-67) years were operated on an AVM of the temporal lobe. All data had been collected prospectively. Patients' charts, as well as surgical reports and outpatient files, were analyzed. Thirteen patients showed an involvement of the SF, and six were localized partially in the lateral wall of the temporal horn. Eight AVMs were located in the temporo-mesial region. Fourteen patients had an AVM located mainly within the visual pathway. In 24 cases, the AVM was located in the dominant hemisphere. The AVMs were classified by the Spetzler-Martin grading system (SM). Visual fields were assessed in all patients pre- and postoperatively by independent ophthalmological examiners.

RESULTS

The initial symptoms leading to the diagnosis of the AVM were seizures in 20 cases (45%), headache without hemorrhage in six cases (14%), incidental finding in five cases (11%), and tinnitus in two cases (5%). Hemorrhage had occurred in 15 cases (34%). Based on SM, 7 AVMs were grade I, 17 grade II, 17 grade III, and 3 grade IV. Preoperatively, seven patients presented with a VFD and two with a hemiparesis. Postoperatively, 8 of 44 (18%) patients presented with a new hemiparesis, remaining permanent in 3 of 44 (7%). In two of these patients, the AVMs were localized temporo-mesially (n = 2/8, 25%). Seven patients (19%) showed a new significant postoperative VFD, and in addition, three patients had worsening of their preexisting VFD (3/7, 43%). Postoperative angiography verified complete AVM occlusion in 43 of 44 (98%) cases. One patient needed reoperation for residual AVM; hence, in all patients, complete occlusion before discharge was achieved.

CONCLUSION

Treatment of temporal lobe AVMs is demanding due to their close spatio-anatomical relationship with important neurovascular structures and the optic radiation. In this surgically treated series, morbidity for a new permanent hemiparesis was 7% and preservation of the visual field could be achieved in almost 90% of all cases. This is a calculable risk for most patients that renders microsurgical resection a justifiable option, even in light of other treatment modalities. The risk for new permanent motor deficits is elevated in temporo-mesial AVMs, and these patients have to be advised accordingly for surgical treatment.

Multimodality treatment of cerebral AVMs in children: a single-centre 20 years experience

PURPOSE

The purpose of this study was to review our experience with a multimodality treatment approach in the management of cerebral arteriovenous malformation (AVM) in children.

METHODS

We retrospectively analysed a consecutive series of 56 children who harboured a cerebral AVM and were treated at our institution between 1988 and 2008. During the whole treatment period, a combined treatment strategy, including microsurgery, endovascular treatment and gamma knife radiosurgery, was used.

RESULTS

Of the 56 patients (median age, 14.0; range, 3 months-18 years) reported, 36 (64.3%) were admitted after AVM rupture; of these, only one AVM (1.8%) was considered untreatable. In 30.9% (17/55) of the treated patients, a single treatment measure was sufficient to attain angiographic cure of the AVM. Among these, six patients (10.9%) had microsurgical AVM resection, four patients (7.3%) underwent endovascular treatment, and another seven patients (12.7%) underwent radiosurgical management of the AVM. The majority of the population (38/55; 69.1%) underwent combined treatment: 21 patients (38.2%) received embolisation followed by radiosurgery of the remnant nidus, ten patients (18.2%) underwent embolisation with subsequent surgical resection of the residual AVM, three patients (5.5%) had radiosurgery after incomplete surgical AVM nidus resection and another four patients (7.3%) required a combination of all three treatment modalities to achieve permanent angiographic cure of the AVM. We observed good clinical outcomes (Glasgow Outcome Scale 5 and 4) in 94.6% of the children. Complete angiographic obliteration was achieved in 93.3% of the patients treated.

CONCLUSION

A multimodality treatment approach in children harbouring cerebral AVMs leads to excellent angiographic and clinical outcomes.

Adjuvant embolization with N-butyl cyanoacrylate in the treatment of cerebral arteriovenous malformations: outcomes, complications, and predictors of neurologic deficits

BACKGROUND AND PURPOSE

The purpose of this study was to assess the frequency, severity, and predictors of neurological deficits after adjuvant embolization for cerebral arteriovenous malformations.

METHODS

From 1997 to 2006, 202 of 275 patients with arteriovenous malformation received embolization before microsurgery (n=176) or radiosurgery (n=26). Patients were examined before and after endovascular embolization and at clinical follow-up (mean, 43.4+/-34.6 months). Outcome was classified according to the modified Rankin Scale. New neurological deficits after embolization were defined as minimal (no change in overall modified Rankin Scale), moderate (modified Rankin Scale < or =2), or significant (modified Rankin Scale >2).

RESULTS

Two hundred two patients were treated in 377 embolization procedures. There were a total of 29 new clinical deficits after embolization (8% of procedures; 14% of patients), of which 19 were moderate or significant. Postembolization deficits resolved in a significant number of patients over time (P<0.0001). Five patients had persistent neurological deficits due to embolization (1.3% of procedures; 2.5% of patients). In multivariate analysis, the following variables significantly predicted new neurological deficit after embolization: complex arteriovenous malformation with treatment plan specifying more than one embolization procedure (OR, 2.7; 95% CI, 1.4 to 8.6), diameter <3 cm (OR, 3.2; 95% CI, 1.2 to 9.1), diameter >6 cm (OR, 6.2; 95% CI, 1.0 to 57.0), deep venous drainage (OR, 2.7; 95% CI, 1.1 to 6.9), or eloquent location (OR, 2.4; 95% CI, 1.0 to 5.7). These variables were weighted and used to compute an arteriovenous malformation Embolization Prognostic Risk Score for each patient. A score of 0 predicted no new deficits, a score of 1 predicted a new deficit rate of 6%, a score of 2 predicted a new deficit rate of 15%, a score of 3 predicted a new deficit rate of 21%, and a score of 4 predicted a new deficit rate of 50% (P<0.0001).

CONCLUSIONS

Small and large size, eloquent location, deep venous drainage, and complex vascular anatomy requiring multiple embolization procedures are risk factors for the development of immediate postembolization neurological deficits. Nevertheless, a significant number of patients with treatment-related neurological deficits improve over time. The low incidence of permanent neurological deficits underscores the usefulness of this technique in carefully selected patients.

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.

Embolization of intracranial arteriovenous malformations with ethylene-vinyl alcohol copolymer (Onyx)

BACKGROUND AND PURPOSE

Endovascular therapy of intracranial arteriovenous malformations (AVMs) is increasingly used. However, it is still under discussion which embolic material is optimal. We report our experience in the treatment of AVMs with ethylene-vinyl alcohol copolymer (Onyx).

MATERIALS AND METHODS

Between July 2002 and January 2008, brain AVMs were embolized with Onyx in 82 consecutive patients in our department. There were 41 females and 41 males with a mean age of 44.2 years (range, 15-85 years). Clinical presentation included symptoms due to intracerebral hemorrhage (n = 37), seizures (n = 18), nonhemorrhagic neurologic deficits (n = 8), headaches (n = 9), or incidental symptoms (n = 10). According to the Spetzler-Martin scale, 59 AVMs were grades I-II, 16 were grade III, and 7 were grades IV-V.

RESULTS

Complete obliteration at the end of all endovascular procedures was achieved in 20/82 patients (24.4%), with an average of 75% (range, 30%-100%) volume reduction. A mean of 2.9 (range, 1-10) feeding pedicles was embolized per patient, whereas an average of 2.6-mL Onyx was used per patient. Procedure-related permanent disabling morbidity was 3.8%, whereas mortality was 2.4%.

CONCLUSIONS

The overall initial complete obliteration rate of intracranial AVMs with Onyx embolization is relatively high, compared with other embolic agents, with evidence of stability with time. Morbidomortality rates due to AVM embolization as a single treatment method or as a part of a multimodality treatment should be further assessed regarding the natural course of the disease.

A nonadhesive liquid embolic agent of ethylene vinyl alcohol copolymer and ethanol mixture for cerebral arteriovenous malformations. Clinical experience

SUMMARY

We report our experience using our new nonadhesive liquid embolic agent, an ethylene vinyl alcohol copolymer (EVAL)/Ethanol mixture, to treat human arteriovenous malformations (AVM). Between June 1995 and April 2001, 57 patients with confirmed AVM underwent embolization with the EVAL/Ethanol mixture. Using 87 procedures consisting of one to three stages, we embolized 185 feeding arteries to occlude as much of the AVM as possible. Repeated injections under fluoroscopic control could be performed smoothly without encountering cementing of the catheter in the vessel wall. Among 87 procedures undertaken in 57 patients, seven (8.0%) procedures in six patients produced new postembolization symptoms. Resolution of these symptoms occurred within hours or days following four of the seven procedures; permanent neurological deficits remained after three embolization procedures (3.4%). Of the 57 patients, three underwent postembolization radiosurgery, 54 were radically treated with microsurgical extirpation. Histopathological examinations of the 54 specimens disclosed mild inflammation within the embolized lumen without inflammatory reactions in the media or adventitia. Follow-up angiograms obtained three years after they underwent radiosurgery showed that in all three patients the nidus had completely disappeared. The EVAL/Ethanol mixture is handled easily and appears to be an effective and safe embolic agent for the preoperative embolization of AVM.

A case of iatrogenic cerebral infarction demonstrated by postmortem cerebral angiography

A 37-year-old man with a meningioma compressing the right frontal lobe underwent preoperative embolization of the feeding vessels from the right meningeal artery. Although the first challenge was apparently successful, an excess amount of embolization agent was accidentally injected during the next procedure. X-ray monitoring demonstrated flow of contrast medium into the right internal carotid, anterior and middle cerebral arteries, and then the patient suddenly developed left hemiparesis, nausea, and deep coma. He died 48 days after the embolization treatment without improvement of the coma. A medicolegal autopsy was performed to determine whether malpractice had occurred during the embolization procedure. An internal examination demonstrated massive necrosis of the cerebral hemispheres and lobar pneumonia with abscess in the lungs. Due to the extensive brain necrosis, it was impossible to carry out ordinary macroscopic examination to identify the precise site of the craniocerebral vessel occlusion. Postmortem angiography was therefore performed, and this successfully revealed occlusion of the right internal carotid artery. In this case, postmortem angiography played a key role in identification of the intracranial vascular lesion that was responsible for the iatrogenic cerebral infarction.

Microsurgery or Radiosurgery for Cerebral Arteriovenous Malformations? A Study of Two Paired Series

OBJECTIVE

To detect parameters that may augment the therapeutic strategy in patients with a cerebral arteriovenous malformation (AVM) that is considered equally suitable for treatment by neurosurgery or radiosurgery, we compared the efficacy and risks of these two methods in a paired series with similar patient and AVM characteristics.

PATIENTS AND METHODS

Two series of patients with AVM were studied, including a series of 39 patients treated using microsurgery (MS) and another series of 39 patients treated via radiosurgery (RS). These series were paired for age and sex, initial symptoms, size, location and Spetzler-Martin grade, and presence of embolization preceding treatment. We compared the posttreatment outcome in the two groups with respect to obliteration rate, neurological status, mortality rate, and recurrent bleeding. Statistical analysis was performed using paired Student's t test.

RESULTS

The Glasgow Outcome Scale values and Modified Rankin Scores measured at discharge and 12 to 24 months were significantly better in the RS series than in the MS series. The obliteration rate tended to be higher in the MS series (91% versus 81%; P = 0.10, not significant), whereas the rate of neurological deficit was higher in the MS series than in the RS series(P &lt; 0.001). The mortality rate was not significantly different in the two series, but the rate of recurrent bleeding was higher in the RS group (10% versus 0%; P = 0.04).

CONCLUSIONS

Although the rate of cure was similar for patients treated with MS and RS, neurological morbidity was higher after MS and recurrent bleeding was more frequent after RS.

ROLE OF RADIOSURGERY IN THE MANAGEMENT OF CEREBRAL ARTERIOVENOUS MALFORMATIONS IN THE PEDIATRIC AGE GROUP

OBJECTIVE

To assess the safety and efficacy of radiosurgery for the management of arteriovenous malformations (AVMs) in the pediatric age group.

METHODS

We reviewed data from 100 children (44 girls and 56 boys) presenting a total of 103 AVMs treated by linear accelerator radiosurgery between December 1988 and May 2002. The median patient age was 12 years (range, 2–16 yr). Sixty-seven AVMs (65%) were in functional locations and 30% were inoperable. The mean AVM volume was 2.8 cm3 (range, 0.9–21.3 cm3). The mean marginal dose was 23 Gy (range, 15–25 Gy) and required between one and four isocenters. Fifty patients received multimodal treatments with embolization and/or surgery before and/or after radiosurgery. Given that 16 patients underwent two sessions of radiosurgery and one patient received three sessions, a total of 119 radiosurgical treatments were delivered. We maintained our clinical and angiographic follow-up for at least 36 months after irradiation or until the complete obliteration of the AVM was confirmed by angiography (our sole end point for judging clinical efficacy). Univariate and multivariate analysis were performed to determine predictive factors for obliteration.

RESULTS

Complete obliteration was achieved for 72 AVMs (70%). The permanent neurological deficit rate was 5%. One patient died because of rebleeding. None of our patients presented bleeding after an angiographically verified AVM obliteration. The main predictive factors for obliteration were low AVM volume and no previous embolization. Moreover, the younger the patient, the more effective the radiosurgery seemed to be.

CONCLUSION

Radiosurgery is a safe and effective treatment for AVMs in the pediatric age group. One criterion for success was the use of a prescription dose similar to that used with adult populations.

Complications of Cerebral Arteriovenous Malformation Embolization: Multivariate Analysis of Predictive Factors

OBJECTIVE:

Embolization is an important therapeutic modality in the multidisciplinary management of arteriovenous malformations (AVM); however, prior series have reported a wide variability in overall complication rates caused by embolization (10–50% neurological deficit, 1–4% mortality). In this study, we reviewed our experience with AVM embolization and analyzed factors that might predict complications and clinical outcomes after AVM embolization.

METHODS:

We analyzed our combined neurovascular unit's results with AVM embolization from 1993 to 2004 for the following outcomes measures: 1) clinically significant complications, 2) technical complications without clinical sequelae, 3) discharge Glasgow Outcome Scale score, and 4) death. To determine embolization efficacy, we analyzed perioperative blood transfusion and rate of AVM obliteration. Univariate and multivariate analyses were performed for patient age, sex, history of rupture, history of seizure, associated aneurysms, AVM size, deep venous drainage, eloquent location, Spetzler-Martin grade, number of embolization stages, number of pedicles embolized, and primary treatment modality.

RESULTS:

Over an 11 year period, 295 embolization procedures (761 pedicles embolized) were performed in 168 patients with embolization as the primary treatment modality (n = 16) or as an adjunct to surgery (n = 124) or radiosurgery (n = 28). There were a total of 27 complications in this series, of which 11 were clinically significant (6.5% of patients, 3.7% per procedure), and 16 were technical complications (9.5% of patients, 5.4% per procedure). Excellent or good outcomes (Glasgow Outcome Scale ≥ 4) were observed in 152 (90.5%) patients. Unfavorable outcomes (Glasgow Outcome Scale 1–3) as a direct result of embolization were both 3.0% at discharge and at follow-up, with a 1.2% embolization-related mortality. In the 124 surgical patients, 96.8% had complete AVM obliteration after initial resection, and 31% received perioperative transfusion (mean 1.4 units packed red blood cells per surgical patient). Predictors of unfavorable outcome caused by embolization by univariate analysis were deep venous drainage (P &lt; 0.05), Spetzler-Martin Grade III to V (P &lt; 0.05), and periprocedural hemorrhage (P &lt; 0.0001) and by multivariate analysis were Spetzler-Martin III to V (odds ratio 10.6, P = 0.03) and periprocedural hemorrhage (odds ratio 17, P = 0.004).

CONCLUSION:

In a single-center, retrospective, nonrandomized study, 90.5% of patients had excellent or good outcomes after AVM embolization, with a complication rate lower than previously reported. Spetzler-Martin grade III to V and periprocedural hemorrhage were the most important predictive factors in determining outcome after embolization.

Application of the liquid coil as an embolic material for arteriovenous malformations

SUMMARY

The purpose of this paper is to clarify advantages and disadvantages of platinum liquid coils as an embolic material for AVMs. During the last eight years, 50 endovascular procedures using liquid coils were conducted in our institute for 19 cases with AVMs, 15 of which were located in the eloquent area. All but one presented with haemorrhage, the exception demonstrating repeated ischemic symptoms. Only liquid coils were used as the embolic material to obliterate the nidus and feeders. In ten of the 15 patients with AVMs located in the eloquent area and one case rejecting surgery, liquid coil embolization was applied one to 11 times (average 3.5 times) to achieve decrease in size and this was then followed by radiosurgery. The remaining eight AVM patients underwent total removal after liquid coil embolization. No complications were encountered during the peri-embolization period. In all cases, the purpose of embolization was to diminish the size to facilitate radiosurgery and decrease bleeding during surgery. The liquid coil has advantages as a material for embolization of AVMs; it is non-toxic and bioinart material; it seldom occludes normal minute vascular channels; when it used in a nidus, it seldom to migrates in the venous direction, and it has good radio-opacity and offers good marking for surgery. Appropriate applications include preoperative embolization or pre-radiosurgical embolization of AVMs, especially when staged embolizations are performed to reduce risk of perfusion pressure breakthrough in patients which are large or located in the eloquent area.

Ventricular/paraventricular small arteriovenous malformations: role of embolisation with cyanoacrylate

Arteriovenous malformations (AVMs) located in or near to ventricles have proven difficult to treat. We report the safety and efficacy of embolisation of these deep central lesions and describe the contribution of embolisation to multimodality treatment. Fourteen consecutive patients with small (less than 3 cm) ventricular/paraventricular AVMs arranged for possible embolisation to their nidi. All patients presented with intracranial haemorrhage. The AVMs ranged in size from 10 to 30 mm (average, 17 mm). Embolisations were performed using liquid adhesive (cyanoacrylate and iodised oil mixture at a ratio of less than 1:4) delivered by flow-guided microcatheters with the patient under general anaesthesia. One patient (7.1%) was considered unsuitable for embolisation, and another (7.1%) was not able to undergo embolisation because of the morphological features of the AVM feeders, while the remaining 12 could be embolised successfully. Six of 12 patients who underwent embolisation achieved complete occlusion of their AVMs (overall occlusion rate, 42.9%), while the remaining 6 were embolised partially with a 60-95% (mean = 80%) size reduction. One (8%) permanent neurological deficit resulted from embolisation. Endovascular therapy seems to make a significant contribution to the multimodality treatment of small AVMs located in the ventricle or paraventricular deep area. Embolisation alone permits complete cure in a large number of patients. It results in obliteration of a significant volume of the nidus in most of the remaining patients, which makes those nidi more vulnerable to subsequent multimodal therapy.

Deep arteriovenous malformations of the basal ganglia and thalamus: natural history

OBJECT

Patients with arteriovenous malformations (AVMs) in a deep location and with deep venous drainage are thought to be at higher risk for hemorrhage than those with AVMs in other locations. Despite this, the natural history of AVMs of the basal ganglia and thalamus has not been well studied.

METHODS

The authors retrospectively evaluated a cohort of 96 patients with AVMs in the basal ganglia and thalamus with respect to the tendency of these lesions to hemorrhage between the time of detection and their eventual successful management. The 96 patients studied had a mean age of 22.7 years at diagnosis, and 51% were male. Intracranial hemorrhage (ICH) was the event leading to clinical detection in 69 patients (71.9%), and 85.5% of these patients were left with hemiparesis. After diagnosis, 25 patients bled a total of 49 times. The cumulative clinical follow up after detection but before surgical management was 500.2 patient-years. The risk of hemorrhage after detection of an AVM of the basal ganglia or thalamus was 9.8% per patient-year.

CONCLUSIONS

The rate of ICH in patients with AVMs of the basal ganglia or thalamus (9.8%/year) is much higher than the rate in patients with AVMs in other locations (2-4%/year). The risk of incurring a neurological deficit with each hemorrhagic event is high. Treatment of these patients at specialized centers is recommended to prevent neurological injury from a spontaneous ICH.

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

OBJECT

The authors report their clinical experience with their new nonadhesive liquid embolic agent, an ethylene vinyl alcohol copolymer (EVAL)/ethanol mixture, to treat arteriovenous malformations (AVMs).

METHODS

Between June 1995 and April 2001, 57 patients with confirmed AVMs underwent embolization of their lesions with the EVAL/ethanol mixture. In 87 procedures consisting of one to three stages, the authors embolized 185 feeding arteries to occlude as much of the AVM as possible. Repeated injections under fluoroscopic control could be performed smoothly without encountering cementing of the catheter to the vessel wall. Among the 87 embolizations undertaken in 57 patients, seven procedures (8%) in six patients produced new postembolization symptoms. Resolution of these symptoms occurred within hours or days after four of the seven procedures; permanent neurological deficits remained after the other three procedures (3.4%). Of the 57 patients, three underwent postembolization radiosurgery, and 54 underwent radical treatment with microsurgical extirpation. Histopathological examination of the 54 specimens disclosed mild inflammation within the embolized lumen without inflammatory reactions in the media or adventitia. Follow-up angiograms obtained 3 years after radiosurgery was administered showed that in all three patients treated in this fashion the nidus had completely disappeared.

CONCLUSIONS

The EVAL/ethanol mixture is handled easily and appears to be an effective and safe agent for preoperative embolization of AVMs.

Combined embolization and microsurgery for cerebral arteriovenous malformation

Thirty-seven of 396 patients with arteriovenous malformations (AVMs) were treated by preoperative embolization and surgical excision in our medical center between 1991 and 1997. The AVMs were Spetzler-Martin grade I in six, grade II in 11, grade III in 12, grade IV in four, and Grade V in four. A total of 69 embolization procedures were performed using estrogen alcohol and polyvinyl acetate as liquid embolization materials. AVM grades improved following embolization in 10 patients. Three hemorrhages occurred several days after the final embolization, probably due to hemodynamic stress on the unoccluded perforating feeders or drainer occlusion. Surgical resection was performed under guidance of intraoperative digital subtraction angiography. Although the AVMs were excised totally in one stage with no major neurological deficits, normal perfusion pressure breakthrough occurred in a patient with prominent collateral circulation of the AVM which developed after the main feeder embolization. Preoperative staged embolization with estrogen alcohol and polyvinyl acetate is effective to expand the surgical indication and to achieve complete resection of difficult AVMs. Direct surgery should be performed as soon as possible if hemodynamic changes are observed following embolization.

[Arteriovenous malformation of the middle and posterior third section of the corpus callosum treated with embolization and surgery]

We are presenting the case of a 58 year-old woman with an arteriovenous malformation (AVM) of the middle and posterior thirds of the corpus callosum which had produced two episodes of bleeding before admission to our Department, when the patient was neurologically intact. The nidus was fed by the anterior and posterior pericallosal arteries draining through the left medial atrial vein to the vein of Galen, by parasagittal cortical veins to the superior sagittal sinus and by right temporal veins to the sphenoparietal sinus. The patient underwent embolization of the anterior and posterior feeders in two sessions separated by a week interval, and then the AVM was removed through a left paramedial parietooccipital craniotomy in a single stage. The patient showed transient mild short term memory deficit, but the final outcome was excellent.

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.

[Parasplenial arteriovenous malformations. Report of 15 surgically treated cases]

INTRODUCTION

Yasargil called paraesplenial those AVMs located at the confluence of the hippocampus, the isthmus of the cingulate girus and the girus occipitotemporalis medialis. Large AVMs at this location are among the most difficult to delineate and to treat.

OBJECTIVE

Analyze the clinical presentation, the findings in the imaging studies, the surgical management and the final outcome in 15 patients with paraesplenial AVMs treated with embolization (the last 4 cases), and microsurgical removal.

RESULTS

Nine patients (60%) were female and 6 males of ages between 15 and 39 years (mean = 24 yrs). Eleven (75%) presented with hemorrhage, (intraventricular in most cases) and the remaining with epilepsy. The Spetzler-Martin grade was II in one Case, III in 5 cases, IV in 8 cases and V in one case. Preoperative embolization clearly improved surgical management. All the patients had complete resection of the lesion, 13 in a single stage and 2 in two stages. The final outcome was good but four patients developed defects of the visual field not seen preoperatively.

CONCLUSIONS

The authors comment the peculiarities of paraesplenial AVMs which can be safely and completely removed with microsurgery and the aid of preoperative embolization.

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.

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.

Embolization of cerebral arteriovenous malformations to enhance the success of subsequent radiosurgery

SUMMARY

We studied angiographic changes in embolized arteriovenous malformations (AVMs) by comparing pre- and postembolization angiograms and angiograms preceding radiosurgery. This study sought factors determining the usefulness of embolization as a pretreatment to enhance the success of subsequent radiosurgery. Thirty patients with cerebral AVMs treated in this manner over 4 years were studied. In these cases AVMs were embolized with cyanoacrylate and were treated with Gamma-knife radiosurgery. The mean size of the AVM nidus was reduced by a fraction of seven following embolization. The subsequent angiogram for planning radiosurgery showed further nidus reduction in 10 AVMs, no change in 12, and regrowth in 8. In all size-reduction cases the nidus was sufficiently packed, and 2 AVMs had thrombosed completely before radiosurgery. All the regrowing AVMs were of diffuse type; 6 were associated with already-developed leptomeningeal channels, and the remaining 3 were fed by newly sprouted meningeal feeders. Five AVMs disappeared following radiosurgery, all representing size-reduction or nochange cases. Analysis of cases with regrowth showed increased risk of that event with feeder occlusion of a multi-axially supplied AVM, lack of reduction of shunt flow, or remaining meningeal feeders. On the other hand, when embolization as pretreatment prior to radiosurgery succeeds in producing a small, compacted, plexiform nidus with slow shunt flow, it furthers the likelihood of successful radiosurgery. Nidus embolization and occlusion of fistulous and meningeal feeders are mandatory, while proximal feeder occlusion and use of embolic materials which risk recanalization should be avoided to prevent nidus regrowth.

Embolization of Arteriovenous Malformation with Diluted Mixture of NBCA

SUMMARY

The technique of nidus embolization with N-butyl- 2-cyanoacrylate (NBCA) glue is presented. The microcatheter is navigated into the nidus and the tip is set in a wedged position. A diluted mixture of NBCA in ethiodized oil (a 25% mixture is mainly used) is injected very slowly, using complete column technique. Using this technique, the progression of glues in the nidus can be seen easily, which leads to improve accuracy and effectiveness of embolization. The mean blood pressure is maintained 15% to 20% below baseline for several days after the embolization to prevent hemorrhage caused by normal pressure breakthrough. We believe this technique is very useful and effective method for the treatment of arteriovenous malformations. However, considerable experience in this technique should be required.

Embolization of arteriovenous malformations with Onyx: clinicopathological experience in 23 patients

OBJECTIVE

To report our experience in treatment of arteriovenous malformations (AVMs) using a new liquid embolic agent, Onyx (Micro Therapeutics, Inc., Irvine, CA).

METHODS

Between January 1998 and May 1999, 23 patients (8 men and 15 women) were treated. The patients' average age was 40 years, with seizure being the most common presenting symptom (39%). The average Spetzler-Martin grade on presentation was 3. The average AVM volume before embolization was 14.5 cm3.

RESULTS

We observed an average 63% reduction in AVM volume after 129 arterial feeders were embolized. There were four adverse events. Two patients experienced ischemia because of inadvertent occlusion of an arterial feeder. One of these patients made a full recovery, but the other patient had a permanent deficit. Two other patients experienced transient neurological deficits that resolved within 1 week of embolization. Permanent morbidity was thus 4% (1 of 23 patients). There were no deaths. Twelve patients underwent subsequent radiosurgery, and 11 patients had surgery that resulted in complete resection of their AVMs. Histopathological examinations showed mild acute inflammation in specimens resected 1 day after embolization. Chronic inflammatory changes were observed in specimens resected more than 4 days after embolization. In two patients, angionecrosis of the embolized vessels was noted. No evidence of parenchymal hemorrhage was observed in these patients, and vessel wall integrity was maintained as well.

CONCLUSION

Onyx is a new nonadhesive liquid embolic agent that has been used to treat 23 patients at our institution with good results. Its nonadhesive nature and ease of use make it a promising agent in the future treatment of AVMs.

Embolisation of cerebral arteriovenous malformations to assure successful subsequent radiosurgery

This study investigated the angiographic changes in embolised arteriovenous malformations (AVMs) pre- and post-embolisation and preradiosurgery to clarify the usefulness of embolisation as a pretreatment for radiosurgery and the strategy of embolisation for the radiosurgical success. A total of 37 patients with cerebral AVMs treated over a period of 4 years was investigated. All the AVMs were embolised with N-butyl cyanoacrylate and 2 months later they were treated by radiosurgery. The size of AVM nidus reduced just following the embolisation (mean 21.9 ml to 3.9 ml). The angiogram taken in preparation for radiosurgery showed a further size reduction in the nidus of 16 AVMs, no change in 10 and regrowth in 11. In all the cases where size was reduced, the nidus was densely packed, while all the regrown AVMs were of the diffuse type. Five AVMs disappeared following radiosurgery, all of which were size-reduction or no-change cases. In conclusion, to achieve success in subsequent radiosurgery, nidus embolisation and the occlusion of fistulous and meningeal feeders are mandatory. Imprudent proximal feeder occlusion and the use of embolic materials with a risk of recanalisation should be avoided to prevent regrowth of the nidus, which may lead to errors in planning the radiosurgery to follow.

Multimodality treatment of nongalenic arteriovenous malformations in pediatric patients

OBJECTIVE

Previously reported series of arteriovenous malformations (AVMs) in pediatric patients have primarily used a single-modality treatment approach of either surgery, radiosurgery, or embolization, with significant treatment-related morbidity and mortality. At our institution, we have used a combined multidisciplinary team approach of all three treatment modalities, alone or in combination, to minimize complications and to maximize efficacy in the management of these lesions.

METHODS

We retrospectively reviewed 40 consecutive pediatric patients with AVMs seen at our institution from 1991 to 1999. A multidisciplinary team planned the treatment for each AVM. The treatment modality consisted of the following approaches: surgery alone in 14 patients, a combination of endovascular embolization and surgery in 6 patients, radiosurgery alone in 11 patients, a combination of endovascular embolization and radiosurgery in 2 patients, and a combination of radiosurgery and surgery in 2 patients. Four patients are receiving ongoing multistaged treatment for reduction of the nidus size for eventual surgical resection or radiosurgical obliteration of large, complex lesions. In one patient, no treatment was recommended.

RESULTS

The clinical outcomes for the overall series were 95.0% excellent or good (Glasgow Outcome Scale score 5 or 4), 2.5% fair (Glasgow Outcome Scale score 3), and 2.5% dead. Radiographic efficacy in the patients who have completed treatment was 92.9% complete obliteration of their AVMs and 7.1% incomplete obliteration. Of the 10 patients who had seizures, 9 are seizure-free.

CONCLUSION

A combined multimodality approach of surgery, radiosurgery, and embolization in managing AVMs in pediatric patients can improve outcomes and minimize morbidity and mortality.