The endovascular treatment of brain arteriovenous malformations

Outcomes of arteriovenous malformation patients with multiple versus single feeders: A multicenter retrospective study with propensity-score matching

INTRODUCTION

The impact of multiple feeding arteries on clinical outcomes of cerebral arteriovenous malformations (AVMs) is not well understood. This study aims to compare outcomes between AVMs with multiple versus single feeding arteries.

PATIENTS AND METHODS

Data from the Multicenter International Study for Treatment of Brain AVMs (MISTA) consortium were analyzed. Propensity score matching (PSM) was used to balance cohorts. Subgroup analysis was conducted for ruptured and unruptured AVMs and different treatment options, and multivariable logistic regression was applied to assess the impact of feeding artery origin.

RESULTS

Among 953 patients, 661(69.4%) had multiple feeding arteries, and 292 (30.6%) had a single feeding artery. After PSM, which included 422 matched patients (211 in each group), the differences in obliteration rates (68.7% vs 74.8%, OR 0.73, 95% CI: 0.48-1.12, p = 0.16) and symptomatic complications (15.6% vs 11.8%, OR 1.37, 95% CI: 0.78-2.41, p = 0.25) were not significant. Subgroup analysis comparing ruptured and unruptured AVMs and different treatment options showed no significant differences across all subgroups. Multivariable analysis identified PICA feeders as significantly associated with increased odds of all complications (OR 7.33, 95% CI: 2.14-25.1, p = 0.002).

DISCUSSION AND CONCLUSION

AVMs with a single feeding artery were more likely to present with rupture, but no significant differences in obliteration rates or complications were observed between the groups after PSM. These findings suggest that while the number of feeding arteries may influence the initial presentation, it does not appear to impact overall treatment success or patient prognosis. Further prospective studies are needed to confirm these findings.

Comparing stand-alone endovascular embolization versus stereotactic radiosurgery in the treatment of arteriovenous malformations with Spetzler-Martin grades I-III: a propensity score matched study

BACKGROUND

Arteriovenous malformations (AVMs) are uncommon cerebral lesions that can cause significant neurological complications. Surgical resection is the gold standard for treatment, but endovascular embolization and stereotactic radiosurgery (SRS) are viable alternatives.

OBJECTIVE

To compare the outcomes of endovascular embolization versus SRS in the treatment of AVMs with Spetzler-Martin grades I-III.

METHODS

This study combined retrospective data from 10 academic institutions in North America and Europe. Patients aged 1 to 90 years who underwent endovascular embolization or SRS for AVMs with Spetzler-Martin grades I-III between January 2010 and December 2023 were included.

RESULTS

The study included 244 patients, including 84 who had endovascular embolization and 160 who had SRS. Before propensity score matching (PSM), complete obliteration at the last follow-up was achieved in 74.5% of the SRS group compared with 57.8% of the embolization group (OR=0.47; 95% CI 0.26 to 0.48; P=0.01). After propensity score matching, SRS still achieved significantly higher occlusion rates at last follow-up (78.9% vs 55.3%; OR=0.32; 95% CI 0.12 to 0.90; P=0.03).Hemorrhagic complications were higher in the embolization group than in the SRS group, although this difference did not reach statistical significance after PSM (13.2% vs 2.6%; OR=5.6; 95% CI 0.62 to 50.47; P=0.12). Similarly, re-treatment rate was higher in the embolization group (10.5% vs 5.3%; OR=2.11; 95% CI 0.36 to 12.31; P=0.40) compared with the SRS group.

CONCLUSION

Our findings indicate that SRS has a significantly higher obliteration rate at last follow-up compared with endovascular embolization. Also, SRS has a higher tendency for fewer hemorrhagic complications and lower re-treatment rate. Further prospective studies are needed.

Analysis of the role of perfusion parameters in predicting rupture of brain arteriovenous malformations: a multi-center study

This study aimed to investigate the potential correlation between the perfusion parameters of brain arteriovenous malformations (bAVMs) as determined by multiphase CT angiography and bAVM rupture. Based on the occurrence of bAVM-related hemorrhage, 480 diagnosed bAVM patients were divided into hemorrhage (n = 220) and non-hemorrhage (n = 260) groups in this retrospective multi-center study spanning 2010 to 2020. On initial rupture CT images, the bAVM nidus and major draining vein were segmented, and time-density curves were extracted to compute perfusion parameters including mean transit time (MTT), time to peak (TTP), blood volume (BV), and blood flow (BF). To examine the potential correlation between these parameters and bAVM rupture, logistic regression was utilized to analyze multifactorial data and compare differences between the two groups. The ruptured group demonstrated a bAVM nidus characterized by an increased BF, a shorter TTP and MTT, and a higher peak density. The veins that were draining exhibited a reduced TTP, MTT, and peak density. A nidus TTP of less than 4s was identified by the multifactorial analysis as a critical risk factor for bAVM rupture. The statistical results highlight the noteworthy correlation between nidus TTP and bAVM rupture, presenting an original framework for assessing the risk of rupture.

Basic Knowledge and Overview of Brain AVMs

Brain arteriovenous malformations (AVMs) are intricate networks of blood vessels in which arteries connect directly to veins, bypassing the capillary system. This aberration can lead to serious neurological manifestations, including seizures, headaches, and hemorrhagic strokes. The embryonic development of AVMs implicates possible disruptions in arteriovenous differentiation during angiogenesis, improper regression of the primary capillary plexus, or the retention of fetal vasculature as contributing factors. Additionally, genetic mutations and environmental influences during pregnancy may facilitate AVM formation, with identified mutations in genes such as endoglin, activin receptor-like kinase 1, SMAD family member 4, and RAS p21 protein activator 1 disrupting vascular development. Such mutations are associated with conditions like hereditary hemorrhagic telangiectasia and capillary malformation-arteriovenous malformation syndrome, thus highlighting the essential role of genetic counseling in AVM management. This review underscores the importance of a deep comprehension of the embryological and genetic foundations of AVMs to refine diagnostic, therapeutic, and prognostic approaches. The paper advocates for advanced research on intervention strategies and emphasizes the significance of a genetics-focused approach in the clinical management of AVMs.

Sustaining consistent cobalt-60 dose rate enhances radiosurgical outcomes in brain arteriovenous malformation management

BACKGROUND AND PURPOSE

The impact of cobalt-60 dose rate (Co-60 DR) on outcomes of stereotactic radiosurgery (SRS) for brain arteriovenous malformations (AVMs) remains fully elucidated. This study explored the association between Co-60 DR and SRS outcomes in AVM treatment.

MATERIALS AND METHODS

772 AVM patients from 1990 to 2020 were included. High DR was defined as ≥ 2.4 Gy/min. AVM patients were categorized into 3 cohorts based on the nidus volume: small (<5 mL), medium (≥5 mL and < 10 mL), and large (≥10 mL). The primary endpoint was AVM obliteration; secondary endpoints included post-SRS hemorrhage.

RESULTS

Cumulative obliteration rates of the large AVM were significantly increased in the high DR group than those in the low DR group (84 % vs. 45 % at 5 years, log-rank test; p = 0.011). Multivariable analysis showed that the obliteration rate was significantly elevated for the high DR group in the large AVM cohort with an adjusted hazard ratio (HR) of 1.78 (95 % confidence interval [CI]: 1.00-3.17, p = 0.049). Post-SRS hemorrhage rates of the entire cohort were significantly decreased in the high DR group than in the low DR group (2.5 % vs. 5.3 % at 5 years, log-rank test; p = 0.035). Multivariable analysis revealed post-SRS hemorrhage was reduced in the high DR group with an adjusted HR of 0.47 (95 % CI: 0.24-0.92, p = 0.026).

CONCLUSION

High DR may lead to increased efficiency for large AVMs and decreased post-SRS hemorrhage in all AVM cases. Sustaining a higher Co-60 DR could potentially yield favorable outcomes for SRS for AVMs.

Treatment of Brain Arteriovenous Malformations

Brain arteriovenous malformations (AVMs) are a rare entity of vascular anomalies, characteristic of anatomical shunting where arterial blood directly flows into the venous circulation. The main aim of the active treatment policy of brain AVMs is the prevention of haemorrhage. There are well-established treatment strategies that continually improve in their safety and efficacy, primarily due to the advances in imaging modalities, targeted and novel techniques, the development of alternative treatment approaches, and even better experience with the disease itself. There are interesting imaging novelties that may be prospectively applicable in the decision-making and planning of the most effective treatment approach for individual patients with intracranial AVM. Surgery is often considered the first-line treatment; however, each patient should be evaluated individually, and the risks of the active treatment policy should not overcome the benefits of the spontaneous natural history of the disease. All treatment modalities, i.e., surgery, radiosurgery, endovascular embolization, and observation, are justified but need to be meticulously selected for each individual patient in order to deliver the best treatment outcome. This chapter deals with historical and currently applied dogmas, followed by introductions of advances in each available treatment modality of AVM management.

Geometrical Characteristics of Grade III Arteriovenous Malformations That Contribute to Better Outcomes in Endovascular Treatment

BACKGROUND

Grade III brain arteriovenous malformation (AVM) is a distinct subgroup of AVMs that encompasses multiple subtypes according to the Spetzler-Martin classification.

METHODS

This retrospective study included 61 patients with grade III AVM who underwent embolization between 2010 and 2022. The study analyzed the angioarchitecture of the AVM nidus and evaluated the outcomes of the embolization procedures.

RESULTS

There were 29 patients (47.5%) with subtype S1E1V1, 20 patients (32.8%) with subtype S2E1V0, and 12 patients (19.7%) with subtype S2E0V1. The rate of complete occlusion in all patients was 47.5% (29 patients). The rate of complete occlusion was higher in cases with a compact nidus (P < 0.001). Several parameters were associated with occlusion of the AVM nidus, including ≤3 arterial feeders (P = 0.017) and presentation with hemorrhage (P = 0.007), with the majority of patients with a compact nidus presenting with hemorrhage. Other factors associated with compact geometry were the presence of a single deep vein, ≤3 arterial feeders, ≤2 superficial draining veins, and an AVM nidus size ≤3 cm.

CONCLUSIONS

The compact nature of grade III AVM is a crucial predictor for the success of embolization. Several characteristics associated with a compact nidus, such as presentation with hemorrhage and a lower number of arterial feeders, have a significantly higher closure rate. Other factors, such as a single deep draining vein, reduced superficial venous drainage, and small size, show a strong association with complete obliteration.

Multi-Stage Treatment for Spetzler-Martin Grades III, IV, and V Arteriovenous Malformations: Preoperative Embolization and Microsurgical Resection in a Consecutive Series of 250 Patients

PURPOSE

The treatment of high-grade brain AVMs is challenging and has no guidelines available to date. This study was aimed at reporting the experience of two centers in treating these AVMs through a multi-stage approach consisting of preoperative embolization and microsurgical resection.

METHODS

A retrospective review was performed for 250 consecutive patients with a diagnosis of high-grade brain AVM (Spetzler-Martin grades III, IV, and V) treated in two centers in Germany between January 1989 and February 2023. The analyzed data included demographic, clinical, morphological, and neurological data.

RESULTS

A total of 150 cases (60%) were classified as Spetzler-Martin grade III, 82 cases (32.8%) were classified as grade IV, and 18 cases (7.2%) were classified as grade V. Eighty-seven cases (34.8%) presented with hemorrhage. The devascularization percentages achieved were <50% in 24 (9.6%), 50-80% in 55 (22%), and >80% in 171 (68.4%) cases. The average number of sessions was 5.65 ± 5.50 and 1.11 ± 0.32 endovascular and surgical procedures, respectively, and did not significantly differ by rupture status. Death or dependency (mRS score ≥ 3) after the last follow-up was observed in 18.8% of patients and was significantly associated with age > 80 years and poor baseline neurological condition. The complete resection rate was 82.3% and was significantly associated with age > 80 years, large nidus, and deep venous drainage. Permanent disabling neurological deficit after at least 3 months of follow-up was diagnosed in 13.2% of patients and was significantly associated with age > 80 years and infratentorial locations.

CONCLUSION

A multi-stage treatment for high-grade AVMs is feasible for selected cases but comes at a functional cost. The devascularization percentage was not associated with the investigated outcomes. Age > 80 years was associated with poor safety and effectiveness outcomes; consequently, this treatment should be offered only in exceptional circumstances.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

Pharmacologic Provocative Testing in Combination With Intraoperative Neurophysiologic Monitoring During Arteriovenous Malformation Embolization

OBJECTIVE

To review our use of pharmacologic provocative testing (PT) and intraoperative neurophysiologic monitoring (IONM) during endovascular embolization for eloquent arteriovenous malformations (AVMs), and better define their clinical utility.

METHODS

This is a prospective study between 1 June 2018 and 1 June 2020. Prior to endovascular embolization, superselective PTs with propofol injection were performed. The PT results were assessed by IONM. The impact of different doses of propofol on PT results was compared.

RESULTS

Under general anesthesia, 111 PTs and 48 endovascular embolizations were performed in 22 patients. For the initial 48 PTs before planned embolization, 38 PTs with 5 mg propofol were negative and repeat PTs with 7 mg propofol were also negative. For the remaining 10 positive PTs, the microcatheter tip was adjusted to an alternative site until repeat PTs were negative to ensure a subsequent safe embolization. In comparison, 5-mg-propofol PT results were consistent with 7-mg-propofol PTs in larger-sized feeders, whereas for smaller-sized vessels, 3-mg-propofol PT results were consistent with 5-mg-propofol PTs. The negative predictive value of PTs was 97.9% (47 of 48), as only 1 of the 48 embolizations with negative PTs resulted in postoperative hemorrhage and none of the other 47 embolizations led to a postoperative neurologic deficit.

CONCLUSIONS

PTs and IONM are valuable techniques to predict neurologic deficits and improve procedure decision-making during AVM embolization under general anesthesia. A 5-mg dose of propofol may be sufficient for PTs in larger-sized feeders and a 3-mg dose may be sufficient in smaller-sized feeding branches.

Chinese Cerebrovascular Neurosurgery Society and Chinese Interventional & Hybrid Operation Society, of Chinese Stroke Association Clinical Practice Guidelines for Management of Brain Arteriovenous Malformations in Eloquent Areas

Aim: The aim of this guideline is to present current and comprehensive recommendations for the management of brain arteriovenous malformations (bAVMs) located in eloquent areas. Methods: An extended literature search on MEDLINE was performed between Jan 1970 and May 2020. Eloquence-related literature was further screened and interpreted in different subcategories of this guideline. The writing group discussed narrative text and recommendations through group meetings and online video conferences. Recommendations followed the Applying Classification of Recommendations and Level of Evidence proposed by the American Heart Association/American Stroke Association. Prerelease review of the draft guideline was performed by four expert peer reviewers and by the members of Chinese Stroke Association. Results: In total, 809 out of 2,493 publications were identified to be related to eloquent structure or neurological functions of bAVMs. Three-hundred and forty-one publications were comprehensively interpreted and cited by this guideline. Evidence-based guidelines were presented for the clinical evaluation and treatment of bAVMs with eloquence involved. Topics focused on neuroanatomy of activated eloquent structure, functional neuroimaging, neurological assessment, indication, and recommendations of different therapeutic managements. Fifty-nine recommendations were summarized, including 20 in Class I, 30 in Class IIa, 9 in Class IIb, and 2 in Class III. Conclusions: The management of eloquent bAVMs remains challenging. With the evolutionary understanding of eloquent areas, the guideline highlights the assessment of eloquent bAVMs, and a strategy for decision-making in the management of eloquent bAVMs.

Comparison of cerebral AVMs in patients undergoing surgical resection with and without prior endovascular embolization

AIM

Brain arteriovenous malformations (AVMs) are congenital anomalies that present as intracranial hemorrhage or epilepsy. AVMs often remain clinically silent for extended periods. Although AVM treatment methods are controversial, three treatment strategies are usually combined or applied alone: surgical removal, embolization and stereotactic radiosurgery. We compared clinical and radiological outcomes in intracranial AVM patients treated via surgical resection with and without prior embolization.

MATERIALS AND METHODS

Patients who did (30 patients) and did not (30 patients) undergo endovascular embolization before surgical resection at the İzmir Katip Çelebi University Atatürk Training and Research Hospital Neurosurgery Clinic from 2011 to 2019 were included in this retrospective, cohort study. Symptoms at diagnosis, comorbidities and clinical (AVM and Spetzler-Martin grade) and morphological characteristics were assessed.

RESULTS

A mean one-year follow-up assessed outcomes using the modified Rankin score, and imaging studies assessed AVM obliteration post-procedure. Mean operation times for surgical resection with and without embolization were 166.50 ± 32.02 and 204.47 ± 26.66 min, respectively. Mean patient hospitalization periods for surgical resection with and without embolization were 8.43 ± 3.60 and 12.00 ± 5.51 days, respectively.

CONCLUSION

Among patients who underwent surgical resection, significant operation time and hospitalization time differences were observed in favor of patients who underwent embolization, indicating that preoperative embolization is a safe and beneficial method for treating ruptured and non-ruptured AVMs.

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

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

The use of dual-lumen balloon for embolization of peripheral arteriovenous malformations

PURPOSE

We aimed to evaluate the safety and feasibility of the embolization of peripheral arteriovenous malformation (AVM) with non-adhesive liquid agents (NALA) injected by dual-lumen balloons (DLB).

METHODS

We conducted a multicenter retrospective study between January 2017 and June 2019, including patients with peripheral AVM embolized with NALA by DLB. Fourteen patients were included. The AVM classification, technical and clinical success were evaluated, as were nidus size, liquid agent used, volume and time of injection in DLB, complications, follow-up and need of surgical intervention.

RESULTS

The mean age of the patients was 37±22.5 years (range, 6-82 years). The mean nidus size was 5.2±2.4 cm (range, 3.0-12.0 cm). By Schobinger classification, 11 AVMs were classified in stage 3 and 3 AVMs were classified in stage 2. By Cho's classification, 2 AVMs were in stage II, 4 AVMs were in stage I, 4 AVMs were in stage IIIa and 4 AVMs were in stage IIIb. Onyx was used in 11 patients (78.6%), while Squid, PHIL, and both Onyx and Squid were used in one patient each (7.1%). Seven patients (50%) required one session of embolization, 4 patients (28.6%) required two, 2 patients (14.3%) required three and 1 patient (7.1%) required four sessions. Complete nidus exclusion was achieved in 11 patients (78.6%), optimal clinical response in 12 patients (85.7%). Four patients (28.6%) exhibited minor complications, all controlled. No major complications were seen. Four patients underwent surgical intervention (28.6%).

CONCLUSION

The embolization of peripheral AVM with NALA in DLB appears to be safe and feasible, achieving high rates of technical and clinical success.

Perinidal Angiogenesis Is a Predictor for Neurovascular Uncoupling in the Periphery of Brain Arteriovenous Malformations: A Task-Based and Resting-State fMRI Study

BACKGROUND

Potential neurovascular uncoupling (NVU) related to perinidal angiogenesis (PA) of brain arteriovenous malformations (AVMs) may cause inappropriate presurgical mapping using functional magnetic resonance imaging (fMRI), resulting in overconfident resection and postoperative morbidity.

PURPOSE

To evaluate the potential impact of PA upon fMRI blood oxygen level-dependent signal in the periphery of AVMs.

STUDY TYPE

Prospective.

POPULATION

Twenty-one patients with AVMs located in the primary sensorimotor cortex (SM1) undergoing task-based fMRI (hand motor), and 19 patients with supratentorial AVMs undergoing resting-state fMRI.

FIELD STRENGTH/SEQUENCE

3.0T, echo-planar, time-of-flight, and magnetization-prepared rapid gradient-echo.

ASSESSMENT

The presence of PA was determined by three observers (Y.C., J.W., and X.C.) according to digital subtraction angiography and MR angiography. Interhemispheric asymmetry of fMRI activations contralateral to hand movements was evaluated with the interhemispheric ratio of the average t-value within ipsilesional SM1 to contralesional SM1. Regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuations (fALFF) were extracted from ring-shaped perinidal regions and contralateral homologous regions, and the corresponding interhemispheric ratios were calculated. The effect of PA on the interhemispheric asymmetry of motor activations, ReHo, and fALFF was estimated.

STATISTICAL TESTS

Pearson analysis, paired and independent t-test, multiple linear regression, Friedman test, and factorial analysis of variance were used.

RESULTS

Motor activations were significantly reduced in ipsilesional SM1 compared to contralesional SM1 (P < 0.05). The presence of PA was the independent predictor of activation loss in ipsilateral SM1(P < 0.05). Furthermore, perinidal regions exhibited reduced ReHo compared to the homologous regions (P < 0.05). PA was significantly associated with the decline of ReHo and fALFF in perinidal regions (P < 0.05, for both).

DATA CONCLUSION

The presence of PA can predict perinidal NVU that may confound the interpretation of both task-based and resting-state fMRI, highlighting the importance of alternative approaches of brain functional localization in improving treatment of AVMs.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.

Morbidity and mortality associated with sequential flow reduction embolization technique of cerebral arteriovenous malformations using n-butyl cyanoacrylate

BACKGROUND

Endovascular embolization of cerebral arteriovenous malformations (AVM) with liquid n-butyl cyanoacrylate (n-BCA) serves multiple purposes including AVM occlusion and flow reduction in preparation for other treatment modalities. The objective was to study the clinical, structural, and angiographic factors affecting complications associated with AVM treatment by sequential n-BCA embolizations for nidal occlusion versus quantitative flow reduction in preparation for surgical resection or radiosurgery.

METHODS

We performed a retrospective review of all patients who underwent endovascular embolization of cerebral AVM at our institution between 1998 and 2019, during which time the technique of traditional embolization evolved to a strategy of targeted sequential flow reduction guided by serial flow imaging based on quantitative magnetic resonance angiography, in conjunction with a shift away from nidal penetration.

RESULTS

Among 251 patients, 47.8% of patients presented with ruptured AVM. On average, each patient underwent 2.4 embolizations, for a total of 613 sessions. Major morbidity related to embolization occurred in 18 (7.2%) patients, but this occurred disproportionately in the traditional embolization strategy (n=16, 8%) in contrast with the flow-targeting strategy (n=2, 3.8%). Four patients (1.6%) died in the overall group, and these all occurred with the traditional embolization strategy (2% of 199 patients); no deaths occurred in the flow-targeting strategy (n=52).

CONCLUSION

Embolization with n-BCA targeted to sequential flow reduction and feeder occlusion with limited nidal penetration prior to definitive surgical or radiosurgical treatment can be safely performed with low overall morbidity and mortality.

N-Butyl Cyanoacrylate Transvenous Arteriovenous Malformation Embolization with Arterial Balloon Assistance: Defining Parameters for a Transvenous Approach as a Potential Upfront Treatment Option in Managing Cerebral Arteriovenous Malformations

Complete obliteration of arteriovenous malformations (AVMs) using a transvenous approach as the primary and stand-alone treatment modality has been increasingly considered as a useful endovascular approach in the treatment of AVMs. AVMs are typically treated with microsurgery, stereotactic radiosurgery, endovascular embolization, or some combination of the three methods. Preservation of the draining vein is a key requisite common to all treatment modalities. Transvenous embolization (TVE) is conventionally not recommended as a stand-alone treatment for the vast majority of AVMs and has been thought to be best indicated when traditional approaches are considered less safe and when specific evaluation criteria are met. We report a case of a 35-year-old asymptomatic male diagnosed with a small intracranial AVM adjacent to the right motor strip which was managed utilizing this approach. We employed endovascular embolization via a transvenous approach with arterial balloon assistance due to the small size of the nidus, eloquent location, en passage arterial supply proximal to the venous varix, and a single draining vein from the fistula. This case illustrates the selective indications and technical nuances of TVE approach in managing AVMs as a potential upfront treatment option. When patients harbor AVMs with specific angio-architectural findings as outlined, TVE utilizing Onyx or N-butyl cyanoacrylate can be safely performed as a primary treatment modality.

Impact of flow and angioarchitecture on brain arteriovenous malformation outcome after gamma knife radiosurgery: the role of hemodynamics and morphology in obliteration

BACKGROUND

Few studies have evaluated the relationship between brain arteriovenous malformations (bAVMs) angioarchitecture and the response to Gamma Knife Stereotactic Radiosurgery (GKSR).

METHODS

A prospectively enrolled single-center cohort of patients with bAVMs treated by GKSR has been studied to define independent predictors of obliteration with particular attention to angioarchitectural variables. Only patients older than 18 years old (y.o.), who underwent baseline digital subtraction angiography (DSA) and clinico-radiological follow-up of at least 36 months, were included in the study.

RESULTS

Data of 191 patients were evaluated. After a mean follow-up of 80 months (range 37-173), total obliteration rate after first GKSR treatment was 66%. Mean dose higher than 22 Gy (P = .019, OR = 2.39, 95% CI 1.15-4.97) and flow rate dichotomized into high vs non-high (P < .001, OR = 0.23, 95% CI 0.11-0.51) resulted to be independent predictors of obliteration. Flow-surrogate angioarchitectural features did not emerge as independent outcome predictors.

CONCLUSIONS

Flow rate seems to be associated in predicting outcome after GKSR conferring high-flow AVM a lower occlusion rate. Its role should be considered when planning radiosurgical treatment of bAVM, and it could be added to other parameters used in GKRS outcome predicting scales.

Complications of Endovascular Treatments for Brain Arteriovenous Malformations: A Nationwide Surveillance

BACKGROUND AND PURPOSE

Embolization is widely performed to treat brain arteriovenous malformations, but little has been reported on factors contributing to complications. We retrospectively reviewed a nationwide surveillance to identify risk factors contributing to complications and short-term clinical outcomes in the endovascular treatment of brain arteriovenous malformations.

MATERIALS AND METHODS

Data for endovascular treatment of brain arteriovenous malformations were extracted from the Japanese nationwide surveillance. Patient characteristics, brain arteriovenous malformation features, procedures, angiographic results, complications, and clinical outcomes at 30 days postprocedure were analyzed.

RESULTS

A total of 1042 endovascular procedures (788 patients; mean, 1.43 ± 0.85 procedures per patient) performed in 111 institutions from 2010 to 2014 were reviewed. Liquid materials were used in 976 procedures (93.7%): to perform presurgical embolization in 638 procedures (61.2%), preradiosurgical embolization in 160 (15.4%), and as sole endovascular treatment in 231 (22.2%). Complete or near-complete obliteration of brain arteriovenous malformations was obtained in 386 procedures (37.0%). Procedure-related complications occurred in 136 procedures (13.1%), including hemorrhagic complications in 59 (5.7%) and ischemic complications in 57 (5.5%). Univariate analysis identified deep venous drainage, associated aneurysms, infratentorial location, and preradiosurgical embolization as statistically significant risk factors for complications. Multivariate analysis showed that embolization of brain arteriovenous malformations in the infratentorial location was significantly associated with complications. Patients with complications due to endovascular procedures had worse clinical outcomes 30 days after the procedures than those without complications.

CONCLUSIONS

Complications arising after endovascular treatment of brain arteriovenous malformations are not negligible even though they may play a role in adjunctive therapy, especially in the management of infratentorial brain arteriovenous malformations.

Overview of the current concepts in the management of arteriovenous malformations of the brain

Background

There is a lack of consensus in the management of arteriovenous malformations (AVMs) of the brain since ARUBA (A Randomised trial of Unruptured Brain Arteriovenous malformations) trial showed that medical management is superior to interventional therapy in patients with unruptured brain AVMs. The treatment of brain AVM is associated with significant morbidity.

Objectives and methods

A review was done to determine the behaviour of brain AVMs and analyse the risks and benefits of the available treatment options. A search was done in the literature for studies on brain AVMs. Descriptive analysis was also done.

Results

The angiogenic factors such as vascular endothelial growth factor and inflammatory cytokines are involved in the growth of AVMs. Proteinases such as matrix metalloproteinase-9 contribute to the weakening and rupture of the nidus. The risk factors for haemorrhage are prior haemorrhage, deep and infratentorial AVM location, exclusive deep venous drainage and associated aneurysms. The advancements in operating microscope and surgical techniques have facilitated microsurgery. Stereotactic radiosurgery causes progressive vessel obliteration over 2–3 years. Endovascular embolisation can be done prior to microsurgery or radiosurgery and for palliation.

Conclusions

Spetzler-Martin grades I and II have low surgical risks. The AVMs located in the cerebellum, subarachnoid cisterns and pial surfaces of the brainstem can be treated surgically. Radiosurgery is preferable for deep-seated AVMs. A combination of microsurgery, embolisation and radiosurgery is recommended for deep-seated and Spetzler-Martin grade III AVMs. Observation is recommended for grades IV and V.

Brain functional organization and structure in patients with arteriovenous malformations

PURPOSE

Developmental in nature, brain arteriovenous malformations (AVM) have the potential to affect whole brain organization. Here we investigated the impact of AVM on functional and structural brain organization using resting-state functional MRI (rsfMRI) and cortical thickness measures.

METHODS

We investigated brain functional organization and structure using rsfMRI in conjunction with cortical thickness analyses in 23 patients with cerebral arteriovenous malformations (AVMs) and 20 healthy control subjects.

RESULTS

Healthy controls showed the expected anti-correlation between activity in the default mode network (DMN) and frontal areas that are part of the attentional control network. By contrast, patients demonstrated a disruption of this anti-correlation. Disruptions to this anti-correlation were even observed in a subgroup of patients with lesions remote from the main nodes of the DMN and were unrelated to differences in perfusion. Functional connectivity differences were accompanied by reduced cortical thickness in frontal attentional areas in patients compared to the controls.

CONCLUSIONS

These results contribute to the discussion that AVMs affect whole brain networks and not simply the area surrounding the lesion.

Radiosurgical treatment of arteriovenous malformations in a retrospective study group of 33 children: the importance of radiobiological scores

PURPOSE

Arteriovenous malformations' (AVMs) obliteration depends on several factors; among the many factors that must be considered to obtain a high rate of obliteration and a low rate of complications, Flickinger-Pollock Score (FPS) seems to have an important role but still have to be validated in the pediatric population while Paddick-Conformity Index (PCI) still has no demonstration of its utility on the outcome and is considered only as a treatment quality marker.

METHODS

We retrospectively analyzed 33 consecutive children (2-18 years) with an AVM, treated with stereotactic radiosurgery Gamma Knife (SRS-GK) from 2001 to 2014 in our institution. We assess angiographic (DSA) Obliteration Rate (OR) as well FPS and PCI to draw conclusions.

RESULTS

DSA-OR was 60.6% with a rate of hemorrhage of 0%. median target volume (TV) was 3.60 cc (mean 4.32 ± 3.63; range 0.15-14.2), median PD was 22 Gy (mean 21.4 ± 2.6; range 16.5-25). Median percentage of coverage was 98% (mean 97 ± 3; range 84-100). The median modified FPS was 0.78 (mean 0.89 ± 0.52; range 0.21-2.1) and highly correlate with OR (p = 0.01). The median PCI was 0.65 (mean 0.65 ± 0.14; range 0.34-0.95) A PCI lower than 0.57 highly correlates with final OR (p = 0.02).

CONCLUSION

SRS-GK was safe and gradually effective in children. A prescription dose-like that used in adult population (i.e. > 18 and between 20 and 25 Gy) is essential to achieve obliteration. A PD of 23 Gy and 22 Gy did impact OR, respectively (p = 0.02) and (p = 0.05). FPS and PCI are valuable scores that seem to correlate with the OR also in the pediatric population although further prospective studies are needed to confirm these observations.

Endovascular Therapy for Brainstem Arteriovenous Malformations

Brainstem arteriovenous malformations (AVMs) represent ∼5% of all intracranial AVMs and carry a higher risk of hemorrhage than their supratentorial counterparts. There is a high and near-uniform mortality with initial and recurrent episodes of hemorrhage. Brainstem AVMs may also present symptomatically with focal neurologic deficits or hydrocephalus. Treatment is indicated for ruptured and symptomatic brainstem AVMs, as well as those possessing high-risk angioarchitectural features. Microsurgical resection and stereotactic radiosurgery are ideal therapeutic options when feasible. Embolization is most commonly used as adjunctive treatment before surgery or stereotactic radiosurgical irradiation. Preoperative embolization facilitates microsurgical resection and reduces intraoperative and postoperative hemorrhage rates. Use of embolization preradiosurgically helps to reduce nidal size, transforming a large lesion to a size amenable to radiosurgical intervention, increasing the probability of obliteration, decreasing procedural hemorrhage risk, stabilizing the lesion until radiotherapeutic effect achieves obliteration, and providing interval symptomatic resolution. Embolization may also be used effectively as stand-alone monotherapy for small lesions with 1 or 2 arterial feeders not supplying eloquent parenchyma. Although an extensive evidence base exists for clinical usefulness of stereotactic radiosurgery as monotherapy or in combination with other therapeutic modalities, only a few studies have reported specifically on obliteration and complication rates with monotherapeutic embolization in the treatment of brainstem AVMs. The potential role of embolization as monotherapy for brainstem AVMs is reviewed and discussed.

Results of volume-staged fractionated Gamma Knife radiosurgery for large complex arteriovenous malformations: obliteration rates and clinical outcomes of an evolving treatment paradigm

OBJECTIVE There are few reported series regarding volume-staged Gamma Knife radiosurgery (GKRS) for the treatment of large, complex, cerebral arteriovenous malformations (AVMs). The object of this study was to report the results of using volume-staged Gamma Knife radiosurgery for patients affected by large and complex AVMs. METHODS Data from 20 patients with large AVMs were prospectively included in the authors' AVM database between 2004 and 2012. A staging strategy was used when treating lesion volumes larger than 10 cm³. Hemorrhage and seizures were the presenting clinical feature for 6 (30%) and 8 (40%) patients, respectively. The median AVM volume was 15.9 cm³ (range 10.1-34.3 cm³). The mean interval between stages (± standard deviation) was 15 months (± 9 months). The median margin dose for each stage was 20 Gy (range 18-25 Gy). RESULTS Obliteration was confirmed in 8 (42%) patients after a mean follow-up of 45 months (range 19-87 months). A significant reduction (> 75%) of the original nidal volume was achieved in 4 (20%) patients. Engel Class I-II seizure status was reported by 75% of patients presenting with seizures (50% Engel Class I and 25% Engel Class II) after radiosurgery. After radiosurgery, 71.5% (5/7) of patients who had presented with a worsening neurological deficit reported a complete resolution or amelioration. None of the patients who presented acutely because of hemorrhage experienced a new bleeding episode during follow-up. One (5%) patient developed radionecrosis that caused sensorimotor hemisyndrome. Two (10%) patients sustained a bleeding episode after GKRS, although only 1 (5%) was symptomatic. High nidal flow rate and a time interval between stages of less than 11.7 months were factors significantly associated with AVM obliteration (p = 0.021 and p = 0.041, respectively). Patient age younger than 44 years was significantly associated with a greater than 75% reduction in AVM volume but not with AVM obliteration (p = 0.024). CONCLUSIONS According to the results of this study, volume-staged GKRS is an effective and safe treatment strategy for large, complex, cerebral AVMs for which microsurgery or endovascular approaches could carry substantially higher risks to the patient. Radiation doses up to 20 Gy can be safely administered. The time interval between stages should be shorter than 11.7 months to increase the chance of obliteration. High nidal flow and a patient age younger than 44 years were factors associated with nidus obliteration and significant nidus reduction, respectively.

Cerebral arteriovenous malformations in the era of embolization for angiographic cure: a single-center experience in Egypt

Background

Embolization for cerebral arteriovenous malformations (AVMs) has evolved in the last decade with evolution in both equipment and material. Embolization targets have expanded to include angiographic cure.

Methods

To discuss the technical and management outcomes of our first cerebral AVM case series treated with embolization. The clinical, angiographic, treatment, and outcome variables of consecutive cerebral arteriovenous malformation cases, treated with curative embolization, between January 2011 and June 2017 in one regional center, were retrospectively analyzed.

Results

In 21 patients, 21 AVMs were identified, and 13 patients (61.9%) were males. The mean of the age was 34.24 ± 12.99. Fifteen patients (71.4%) had a history of intracranial hemorrhage, and 10 (47.6%) patients had seizures. Sixteen patients (76.2%) were at grade 1 of modified Rankin Scale (mRS) at admission. The median for modal Spetzler-Martin grade was 2. The average number of arterial feeders was 3. Direct arteriovenous fistulas were found in 4 cases (19.0%). Venous aneurysms were found in 4 cases (19.0%). Seventeen AVMs (80.9%) were considered high bleeding risk lesions. Forty-three embolization sessions were done. Early hemorrhage occurred in 3 sessions (7.0%). Vessel perforation occurred 1 session (2.3%). Poor outcome occurred in 1 patient that was discharged at grade 3 mRS. Angiographic cure was achieved in 9 patients (42.9%). The average size reduction was 65%.

Conclusions

Onyx embolization could serve as a curative option for AVM treatment with accepted morbidity and mortality.

Assessment of periprocedural hemodynamic changes in arteriovenous malformation vessels by endovascular dual-sensor guidewire

Endovascular embolization is an important modality in the treatment of brain AVMs. Nowadays staged embolization is the method of choice for the prevention of perioperative hemorrhagic complications. Current theory suggests that simultaneous occlusion of more than 60% of AVM volume induces significant redistribution local blood flow. That, in turn, may lead to hemorrhage due to AVM rupture. Aside from angiographic findings, there is still no method that predicts the degree of safe partial embolization. Intraluminal measurement of flow velocity and pressure in the vicinity of the AVM nidus might allow detecting the changes in local hemodynamics. That can provide a valuable data and shed the light on the origin of vascular catastrophes. Ten patients underwent 12 embolization sessions with intraluminal flow velocity and pressure monitoring. The measurements were performed by dual-sensor guidewire. The "Combomap" (Volcano) system with Combowire microguidewires was chosen for measurements, as there is a documented experience of safe use of said guidewires in the cerebral vasculature. The findings observed during the study matched empirical data as well as the current physiological hypothesis of AVM hemorrhage. In conjunction with DSA runs, intraluminal flow velocity and pressure monitoring has the potential to become a valuable tool in AVM treatment.

UniversitätsSpital Zürich: 80 years of neurosurgical patient care in Switzerland

Background

The predecessor of today’s Department of Neurosurgery, UniversitätsSpital Zürich (USZ), was founded 80 years ago as the first independent Swiss clinic dedicated to neurosurgical patient care. On the occasion of this anniversary, we aimed to highlight the history of neurosurgery as a specialty at the USZ, and to put it into the historical context of Swiss and European Neurosurgery.

Method

A literature review was conducted and we searched the archives of the USZ and the city of Zurich, as well as those of Swiss journals to extract relevant published articles, books, historical reports and pictures. The USZ Department of Medical History, the Museum of Medical History and the Swiss National Library were contacted to provide source material. To further verify the content, (emeritus) faculty from the USZ and external experts on the history of Swiss neurosurgery reviewed the manuscript.

Results

Surgeries of the head and spine had occasionally been conducted in Zurich by the general surgeons, Rudolf Ulrich Krönlein and Paul Clairmont, before an independent neurosurgical clinic was founded by Hugo Krayenbühl on 6 July 1937. This was the first Swiss department dedicated to neurosurgical patient care. Besides providing high-quality medicine for both the local and wider population, the department was chaired by eminent leaders of neurosurgery, who influenced the scientific and clinical neurosurgery of their time. As such, it has long been regarded as one of the top teaching and research hospitals in Switzerland and in Europe.

Conclusions

On the occasion of its 80th anniversary, we have performed an in-depth review of its development, successes and challenges, with a special focus on the early decades. Reflecting on the past, we have identified common denominators of success in neurosurgery that remain valid today.

Electronic supplementary material

The online version of this article (10.1007/s00701-017-3357-z) contains supplementary material, which is available to authorised users.

Treatment Outcomes of A Randomized Trial of Unruptured Brain Arteriovenous Malformation-Eligible Unruptured Brain Arteriovenous Malformation Patients

BACKGROUND

The guideline for treating unruptured brain arteriovenous malformations (ubAVMs) remains controversial. A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) reported lower risk of stroke or death with conservative management compared to interventional treatment. There were numerous limitations to the study, including short follow-up period and disproportionate number of patients treated with surgery and embolization.

OBJECTIVE

To evaluate whether treatment of ARUBA-eligible patients have acceptable outcomes at our institution.

METHODS

Retrospective analysis was performed on 673 patients with brain AVMs treated at our institution between 2001 and 2014. One hundred five patients were ARUBA eligible and included in the study. Patients were divided into the microsurgery or Gamma Knife Radiosurgery (GKS; Elekta, Stockholm, Sweden) arm depending on their final treatment. Mean follow-up period was 43 mo (range 4-136 mo). Primary outcome was stroke or death.

RESULTS

A total of 8 (7.6%) patients had a stroke or died. The overall risk of stroke or death was 11.4% (5 of 44 patients) for the microsurgery arm and 4.9% (3 of 61 patients) for the GKS arm. The annual rates of stroke or death were 2.1%, 4.0%, and 1.2% for the entire patient cohort, microsurgery arm, and GKS arm, respectively. AVM obliteration rates at the end of the follow-up period were 95.5% and 47.5% for the microsurgery and GKS arms, respectively.

CONCLUSION

We report a lower overall risk of stroke or death in our ARUBA-eligible patients following treatment than ARUBA. Our results suggest that microsurgery and GKS may be appropriate treatments for patients with ubAVM.

Pial-Dural Intracranial Arteriovenous Fistula with Flow-Associated Aneurysmal Rupture-Case Report with Review of Literature and Proposal on the Mechanism of Hemorrhage and Treatment Options

BACKGROUND

Vascular anomalies in the form of dural arteriovenous fistulas (DAVFs), arteriovenous malformations, and aneurysms are well described in the literature. Pial arteriovenous fistulas (PAVFs) are described to a lesser extent in the literature. When these anomalies are combined, diagnosis and treatment become complex.

CASE DESCRIPTION

A 55-year-old man presented with PAVF/DAVF with a ruptured flow-related aneurysm in the distal left posterior inferior cerebellar artery, which required surgical clipping and disconnection. We performed a PubMed search of all identifiable cases of PAVFs in adults. We then identified which cases had components of DAVFs and flow-related aneurysms. We identified 51 PAVF cases and identified which patients presented with hemorrhage and the treatment modalities of all cases. Of 51 cases identified, 4 were a DAVF/FRA, and 5 were a PAVF/DAVF. One case of PAVF/DAVF/FRA was identified.

CONCLUSIONS

The exact mechanism of PAVF/DAVF formation is unknown. Hemorrhage predilection of PAVF/DAVF is more difficult to predict than a sole fistula, likely secondary to the complex flow dynamics. To our knowledge, this literature review is the largest review to date regarding PAVFs in adult patients and can provide insight into decision making when evaluating treatment options.

Isolated giant cerebral varix - A diagnostic and therapeutic challenge: A case report

Background:

Isolated giant cerebral varix (IGV) is an uncommon vascular lesion that represents a diagnostic challenge and requires dynamic vascular studies for its characterization. The IGV is considered a benign, low-flow venous lesion with very low risk of bleeding that might cause secondary symptoms mainly due to compression of the adjacent parenchyma.

Case Description:

A 12-year-old female patient with non-contributory medical history presented with headache for the last 2 months. Upon admission, her neurological examination was unremarkable. Magnetic resonance imaging (MRI) and computed tomography angiography (CTA) images demonstrated a large varicose dilation of the superficial Sylvian vein, located anterior to the left temporal pole, with no evidence of abnormal arteriovenous connections or tumoral lesions. This finding was considered incidental and unrelated to her symptoms. In this case, we considered that the combination of CTA and MRIs was enough to establish an accurate diagnosis, excluding the need to perform invasive imaging studies. Taking into account these considerations, the patient was managed with conservative treatment and has been followed up for 1 year, remaining asymptomatic.

Conclusion:

Cerebral IGVs are rare vascular lesions that are treated conservatively when asymptomatic and surgically in the case of rupture or compression of adjacent structures. Given our observation of a high unlikelihood of vascular connections to arteries, and the information obtained with non-invasive imaging techniques such as CTA and MRI was enough to make a clinical decision and avoid the evaluation with invasive procedures.

Role of embolization for cerebral arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are complex high-flow lesions that can result in devastating neurological injury when they hemorrhage. Embolization is a critical component in the management of many patients with cerebral AVMs. Embolization may be used as an independent curative therapy or more commonly in an adjuvant fashion prior to either micro- or radiosurgery. Although the treatment-related morbidity and mortality for AVMs--including that due to microsurgery, embolization, and radiosurgery--can be substantial, its natural history offers little solace. Fortunately, care by a multidisciplinary team experienced in the comprehensive management of AVMs can offer excellent results in most cases.

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.

[The outcomes of stereotactic radiotherapy in patients with cerebral arteriovenous malformations]

INTRODUCTION

Cerebral arteriovenous malformations (AVMs) are the congenital anomalies of development of cerebral vessels during the embryonic period. The conventional therapy for AVMs currently includes endovascular management, microneurosurgical resection, and stereotactic irradiation.

MATERIAL AND METHODS

A total of 315 patients with brain AVMs were subjected to stereotactic radiotherapy in 2005-2011. 238 (76%) patients had previous subarachnoid hemorrhage (SAH) within different time (6 months to 5 years) before the therapy; 214 (68%) patients had headaches; 113 (36%) patients had focal neurological symptoms caused by localization; and 82 (26%) patients had seizures. Twenty-three patients were subjected to surgical resection of an intracerebral hematoma prior to radiotherapy and 119 (36%) patients received endovascular treatment including partial embolization of the stroma of AVM. 267 patients received single-fraction radiosurgical irradiation. In patients with large AVMs, we used the hypofractionation technique consisting in target irradiation with several (usually 2-7) fractions; the radiation dose per fraction exceeds 2 Gy. Forty-six patients were irradiated in the hypofractionation mode; two patients had a course of stereotactic radiotherapy in the standard fractionation mode. The marginal dose of radiosurgical irradiation was 13-30 Gy (the average dose was 24 Gy). The main group of patients (38 individuals) with large AVMs was treated using hypofractionation of 35 Gy per 5 fractions.

RESULTS

Control angiography was carried out in 225 patients who had been followed up for at least 2 years after therapy showed that complete obliteration was achieved in 83% of cases. The rate of symptomatic radiation reactions was less than 10%. The higher risk of developing obliteration was observed for AVMs less than 2 cm3 in size at marginal doses more than 24 Gy. In the hypofractionation group consisting of 27 patients with complete follow-up data, obliteration was observed in 10 (37%) patients. The rate of symptomatic reactions was less than 35%.

CONCLUSIONS

The radiosurgical method is a minimally invasive choice of treatment for patients with brain AVM, which allows one to achieve sufficiently high degree of obliteration with the minimum complication rate. The hypofractionation procedure is the method of choice for treating large AVMs. Stereotactic irradiation using the Novalis linear accelerator makes it possible to treat patients with AVMs of virtually any location and volume.

Stereotactic radiosurgery for arteriovenous malformations after Onyx embolization: a case-control study

OBJECT

Onyx, an ethylene-vinyl alcohol copolymer mixed in a dimethyl sulfoxide solvent, is currently one of the most widely used liquid materials for embolization of intracranial arteriovenous malformations (AVMs). The goal of this study was to define the risks and benefits of stereotactic radiosurgery (SRS) for patients who have previously undergone partial AVM embolization with Onyx.

METHODS

Among a consecutive series of 199 patients who underwent SRS between January 2007 and December 2012 at the University of Virginia, 25 patients had Onyx embolization prior to SRS (the embolization group). To analyze the obliteration rates and complications, 50 patients who underwent SRS without prior embolization (the no-embolization group) were matched by propensity score method. The matched variables included age, sex, nidus volume before SRS, margin dose, Spetzler-Martin grade, Virginia Radiosurgery AVM Scale score, and median imaging follow-up period.

RESULTS

After Onyx embolization, 18 AVMs were reduced in size. Total obliteration was achieved in 6 cases (24%) at a median of 27.5 months after SRS. In the no-embolization group, total obliteration was achieved in 20 patients (40%) at a median of 22.4 months after SRS. Kaplan-Meier analysis demonstrated obliteration rates of 17.7% and 34.1% in the embolization group at 2 and 4 years, respectively. In the no-embolization group, the corresponding obliteration rates were 27.0% and 55.9%. The between-groups difference in obliteration rates after SRS did not achieve statistical significance. The difference in complications, including adverse radiation effects, hemorrhage episodes, seizure control, and patient mortality also did not reach statistical significance.

CONCLUSIONS

Onyx embolization can effectively reduce the size of many AVMs. This case-control study did not show any statistically significant difference in the rates of embolization or complications after SRS in patients who had previously undergone Onyx embolization and those who had not.

Targeted embolization reduces hemorrhage complications in partially embolized cerebral AVM combined with gamma knife surgery

This study investigated the effect and safety of targeted embolization in partially embolized cerebral arteriovenous malformation (AVM) followed by gamma knife surgery (GKS). We retrospectively analyzed 86 AVM patients who were targeted embolized by Onyx followed by GKS for residual nidus. Embolization-related complications were collected and the clinical effect was evaluated. During targeted embolization, intranidus or hemodynamic aneurysms and AVM-related fistula were evaluated and targeted embolized. Patients with AVM-related aneurysms and fistula were divided into a targeted embolization group and non-targeted embolization group based on the retrospectively determined treatment strategy. The effect of targeted embolization on hemorrhage risk was evaluated. The overall annual hemorrhage rate was 1.66% with 2.26% for ruptured AVMs and 1.08% for unruptured lesions. The annual mortality rate was 0.4%. Only one in 16 patients with embolization-related complications had permanent neurologic deficit. Twenty-four of 29 cases with intranidus aneurysms were targeted embolized, four of five cases with hemodynamic aneurysms were targeted embolized and eight of nine cases with arteriovenous fistula were targeted embolized. Chi square results showed the hemorrhage complications in the target embolization group were significantly lower than those in the non-target embolization group (p < 0.01). Targeted embolization combined with GKS treatment decreased the annual hemorrhage rate and improved clinical outcome with low permanent complications in partially embolized AVMs. This method could be proposed for the treatment of large brain AVMs when a single-technique treatment is not feasible.

Long-term plasticity in adult somatosensory cortex: functional reorganization after surgical removal of an arteriovenous malformation

The temporal scale of neuroplasticity following acute alterations in brain structure due to neurosurgical intervention is still under debate. We conducted a longitudinal study with the objective of investigating the postoperative changes in a patient who underwent cerebrovascular surgery and who subsequently lost proprioception in the fingers of her right hand. The results show increased activation in contralesional somatosensory areas, additional recruitment of premotor and posterior parietal areas, and changes in functional connectivity with left postcentral gyrus. These findings demonstrate long-term modifications of cortical organization and as such have important implications for treatment strategies for patients with brain injury.

Selective and superselective angiography of pediatric moyamoya disease angioarchitecture: the anterior circulation

The angioarchitecture of the so-called moyamoya vessels in children has not been explicitly analyzed. We aimed to investigate the precise anatomy of the vascular anastomotic networks in patients with childhood moyamoya disease. Six children diagnosed with moyamoya disease for the first time underwent an angiographic investigation with selective and superselective injections. We recorded the arterial branches feeding the moyamoya anastomotic networks, their connections and the recipient vessels. Depending on the level of the steno-occlusive lesion, the feeding vessels included the medial striate arteries, the perforators of the choroidal segment of the carotid, the uncal artery, the medial and lateral branches of the intraventricular segment of the anterior choroidal artery, perforators of the communicating segment, the superior hypophyseal arteries, the prechiasmal branches of the ophthalmic artery, the ethmoidal arteries and the dural branches of the cavernous carotid. Through connections, which are described, the recipient vessels were the lateral striate arteries and the middle cerebral, the medial striate arteries and the anterior cerebral, medullary arteries around the ventricular system, anterior temporal branches of the middle cerebral, orbitofrontal and frontopolar branches of the anterior cerebral, as well as other cortical branches of the anterior and middle cerebral territories. The use of high quality selective and superselective angiography enabled us to clearly demonstrate for the first time aspects of the microangiographic anatomy of the moyamoya anastomotic network previously only vaguely or incompletely described.

Endovascular advances for brain arteriovenous malformations

Arteriovenous malformations (AVMs) of the brain represent unique challenges for treating physicians. Although these lesions have traditionally been treated with surgical resection alone, advancements in endovascular and radiosurgical therapies have greatly expanded the treatment options for patients harboring brain AVMs. Perhaps no subspecialty within neurosurgery has seen as many advancements over a relatively short period of time as the endovascular field. A number of these endovascular innovations have been designed primarily for cerebral AVMs, and even those advancements that are not particular to AVMs have resulted in substantial changes to the way cerebral AVMs are treated. These advancements have enabled the embolization of cerebral AVMs to be performed either as a stand-alone treatment, or in conjunction with surgery or radiosurgery. Perhaps nothing has impacted the treatment of brain AVMs as substantially as the development of liquid embolics, most notably Onyx and n-butyl cyanoacrylate. However, of near-equal impact has been the innovations seen in the catheters that help deliver the liquid embolics to the AVMs. These developments include flow-directed catheters, balloon-tipped catheters, detachable-tipped catheters, and distal access catheters. This article aims to review some of the more substantial advancements in the endovascular treatment of brain AVMs and to discuss the literature surrounding the expanding indications for endovascular treatment of these lesions.

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.

Curing arteriovenous malformations using embolization

Endovascular embolization is typically reserved as an adjuvant therapy in the management of cerebral arteriovenous malformations (AVMs), either for preoperative devascularization or preradiosurgical volume reduction. Curative embolization plays a limited role in AVM treatment but several studies have shown that it is possible, especially with later-generation liquid embolic agents. Given the complexity of AVM anatomy and the recent controversies over the role of any intervention in AVM management, it is critical that the cerebrovascular community better define the indications of each treatment modality to provide quality AVM management. In this review, the authors evaluate the role of curative AVM embolization. Important considerations in the feasibility of curative AVM embolization include whether it can be performed reliably and safely, and whether it is a durable cure. Studies over the past 20 years have begun to define the anatomical factors that are amenable to complete endovascular occlusion, including size, feeding artery anatomy, AVM morphology, and endovascular accessibility. More recent studies have shown that highly selected patients with AVMs can be treated with curative intent, leading to occlusion rates as high as 100% of such prospectively identified lesions with minimal morbidity. Advances in endovascular technology and techniques that support the efficacy and safety of curative embolization are discussed, as is the importance of superselective diagnostic angiography. Finally, the durability of curative embolization is analyzed. Overall, while still unproven, endovascular embolization has the potential to be a safe, effective, and durable curative treatment for select AVMs, broadening the armamentarium with which one can treat this disease.