Modern radiosurgical and endovascular classification schemes for brain arteriovenous malformations.

Stereotactic radiosurgery (SRS) and endovascular techniques are commonly used for treating brain arteriovenous malformations (bAVMs). They are usually used as ancillary techniques to microsurgery but may also be used as solitary treatment options. Careful patient selection requires a clear estimate of the treatment efficacy and complication rates for the individual patient. As such, classification schemes are an essential part of patient selection paradigm for each treatment modality. While the Spetzler-Martin grading system and its subsequent modifications are commonly used for microsurgical outcome prediction for bAVMs, the same system(s) may not be easily applicable to SRS and endovascular therapy. Several radiosurgical- and endovascular-based grading scales have been proposed for bAVMs. However, a comprehensive review of these systems including a discussion on their relative advantages and disadvantages is missing. This paper is dedicated to modern classification schemes designed for SRS and endovascular techniques.

Arterial aneurysms associated with arteriovenous malformations of the brain: classification, incidence, risk of hemorrhage, and treatment-a systematic review.

BACKGROUND: Aneurysms associated with brain arteriovenous malformations (bAVMs) influence the natural history of these lesions and pose important therapeutic challenges. However, the epidemiology, natural history, and appropriate management of the aneurysms associated with bAVMs are not completely understood due to the paucity of large and uniform studies. We performed a systematic review of published series examining the association between aneurysms and bAVMs with the purpose of clarifying the prevalence, risk of hemorrhage, and appropriate management of these lesions. METHOD: PRISMA/MOOSE guidelines were followed. We conducted a comprehensive literature search of three databases (PubMed, Ovid MEDLINE, and Ovid EMBASE) on aneurysms associated with bAVMs. Only studies examining consecutive case series of aneurysms associated with bAVMs were included. From the collected studies, we extracted data regarding prevalence of bAVM-associated aneurysms, risk of aneurysm rupture in relation to bAVM location and aneurysm characteristics, and treatment-related outcomes. RESULTS: Our systematic review included 44 articles with a total of 10,093 bAVMs. The proportion of bAVMs with an associated aneurysm was 20.2 % (95 % CI = 19.4-20.9 %). Among ruptured bAVMs with associated aneurysms, the aneurysm was the source of hemorrhage in 49.2 % (95 % CI = 43.7-54.7 %) of cases. Flow-related aneurysms were the most common source of aneurysm rupture (78.5 %, 95 % CI = 70.6-84.9 %). Infratentorial bAVM-associated aneurysms presented a higher risk of rupture (60 %, 95 % CI = 47.4-71.9 %) when compared with supratentorial lesions (29 %, 95 % CI = 21.4-38.5 %). Endovascular treatment of aneurysms associated with bAVMs had a cure rate of 80.0 % (95 % CI = 73.3-85.3 %), complication rate of 8.7 % (95 % CI = 5.5-13.1 %), and a good neurological outcome rate of 78.8 % (95 % CI = 72.5-83.9 %). CONCLUSIONS: Twenty percent of bAVMs harbored arterial aneurysms. The presence of aneurysm increases the risk of bleeding of the bAVM, especially when flow-related or infratentorially located. Aneurysms associated with bAVMs should be treated promptly. Selective endovascular treatment of bAVM-associated aneurysms appears safe and effective.

Features predictive of brain arteriovenous malformation hemorrhage: extrapolation to a physiologic model.

BACKGROUND AND PURPOSE: Although there is generally thought to be a 2% to 4% per annum rupture risk for brain arteriovenous malformations (bAVMs), there is no way to estimate risk for an individual patient. METHODS: In this retrospective study, patients were eligible who had nidiform bAVMs and underwent detailed pretreatment diagnostic cerebral angiography at our medical center from 1996 to 2006. All patients had superselective microcatheter angiography, and films were reviewed for the purpose of this project. Patient demographics, clinical presentation, and angioarchitectural characteristics were analyzed. A univariate analysis was performed, and angioarchitectural features with potential physiological significance that showed at least a trend toward significance were added to a multivariate logistic regression model. RESULTS: One hundred twenty-two bAVMs met criteria for study entry. bAVMs with single venous drainage anatomy were more likely to present with hemorrhage. In addition, patients with multiple draining veins and a venous stenosis reverted to a risk similar to those with 1 draining vein, whereas those with multiple draining veins and without stenosis had diminished association with hemorrhage presentation. Those bAVMs with associated aneurysms were more likely to present with hemorrhage. These findings were robust in both univariate and multivariate models. CONCLUSIONS: The results of this article lead to the first physiological, internally consistent model of individual bAVM hemorrhage risk, where 1 draining vein, venous stenosis, and associated aneurysms increase risk.

An approach to the symbolic representation of brain arteriovenous malformations for management and treatment planning.

INTRODUCTION: There is currently no standardised approach to arteriovenous malformation (AVM) reporting. Existing AVM classification systems focuses on angioarchitectural features and omit haemodynamic, anatomical and topological parameters intuitively used by therapists. METHODS: We introduce a symbolic vocabulary to represent the state of an AVM of the brain at different stages of treatment. The vocabulary encompasses the main anatomic and haemodynamic features of interest in treatment planning and provides shorthand symbols to represent the interventions themselves in a schematic representation. RESULTS: The method was presented to 50 neuroradiologists from 14 countries during a workshop and graded 7.34 ± 1.92 out of ten for its usefulness as means of standardising and facilitating communication between clinicians and allowing comparisons between AVM cases. Feedback from the survey was used to revise the method and improve its completeness. For an AVM test case, participants were asked to produce a conventional written report and subsequently a diagrammatic report. The two required, on average, 6.19 ± 2.05 and 5.09 ± 3.01 min, respectively. Eighteen participants said that producing the diagram changed the way they thought about the AVM test case. CONCLUSION: Introduced into routine practice, the diagrams would represent a step towards a standardised approach to AVM reporting with consequent benefits for comparative analysis and communication as well as for identifying best treatment strategies.

Pediatric intracranial arteriovenous shunts: a global overview.

INTRODUCTION: Cerebral arteriovenous shunts (CAVS) in the pediatric population cannot be compared to those in adults as they present different anatomical, physiological, and pathological characteristics concerning the arterial and venous vasculature and the cerebrospinal fluid physiology. These lesions develop in a maturing brain, of which expression is difficult to assess, with a potential for recovery different from that in adults. DISCUSSION: Their impact on the brain will be different in the antenatal period, in neonates, in infants, and in children, with variable symptoms according to each age group. We review different classifications of pediatric CAVS (according to the anatomical space in which they develop, their type and architecture, and the age at which they reveal), describe their evolution, and discuss the current role of endovascular treatment in the management of these vascular lesions.

Evaluation of prognostic factors as predictor of AVMS obliteration after Gamma Knife radiosurgery.

BACKGROUND: The reported AVMs obliteration rate after Gamma Knife radiosurgery (GKS) ranges from 70 to 94 %. The objective of the present study was to assess prognostic factors predictive for cerebral AVMs obliteration in 127 patients who underwent GKS. METHODS: The AVMs were classified according to the Spetzler-Martin classification. Twenty-one cases (16.5 %) were classified as grade I, 46 cases (36.2 %) as grade II, 51 cases (40.1 %) as grade III, and nine cases (7.1 %) as grade IV-V. The AVMs were deeply located in 16.5 % of patients. The peripheral prescription dose ranged from 16 to 30 Gy (mean 22.3 Gy). The AVMs volume ranged from 0.1 to 13 cc (mean 2.7 cc). RESULTS: In 72 patients out of the 104 (69.2 %) with a radiological follow-up, MRI showed the AVM obliteration; in 54 cases (60 %) out of the 90 that performed a DSA, a complete AVM obliteration was achieved (average closure time 48.5 months). The volume of the nidus (p = 0.001), the prescription dose (p = 0.004), the 2002 Pollock-Flickinger classification (p = 0.031), and their 2008 revised classification (p = 0.025) were found to be statistically significant in predicting the probability of AVM closure. In the multivariate analysis, only the prescription dose was found to be an independent prognostic factor (p = 0.009) for AVM obliteration. CONCLUSIONS: The volume of the nidus and the prescription dose significantly influence the outcome of radiosurgical treatment. The Pollock-Flickinger classification was found to be a reliable scoring system in predicting the AVM closure and an important tool for selection of patients candidate for GKS.

Vascular malformations of the brain.

Vascular malformations of the brain are a heterogeneous group of disorders involving the blood vessels of the brain. These entities are relatively rare; therefore, most primary care physicians are somewhat unfamiliar with their clinical implications and management. Vascular malformations of the brain range from the completely benign capillary telangiectasia to the potentially fatal arterio-venous malformation. This article reviews the distinct natural histories, etiologies and treatments of four major types of malformations: capillary telangiectasia, developmental venous anomaly, cavernous malformation and arteriovenous malformation.

Intermediate-grade brain arteriovenous malformations and the boundary of operability using the supplemented Spetzler-Martin grading system.

OBJECTIVE: Supplemented Spetzler-Martin grading (Supp-SM), which is the combination of Spetzler-Martin and Lawton-Young grades, was validated as being more accurate than stand-alone Spetzler-Martin grading, but an operability cutoff was not established. In this study, the authors surgically treated intermediate-grade AVMs to provide prognostic factors for neurological outcomes and to define AVMs at the boundary of operability. METHODS: Surgically treated Supp-SM intermediate-grade (5, 6, and 7) AVMs were analyzed from 2011 to 2018 at two medical centers. Worsened neurological outcomes were defined as increased modified Rankin Scale (mRS) scores on postoperative examinations. A second analysis of 2000-2011 data for Supp-SM grade 6 and 7 AVMs was performed to determine the subtypes with improved or unchanged outcomes. Patients were separated into three groups based on nidus size (S1: < 3 cm, S2: 3-6 cm, S3: > 6 cm) and age (A1: < 20 years, A2: 20-40 years, A3: > 40 years), followed by any combination of the combined supplemented grade: low risk (S1A1, S1A2, S2A1), intermediate risk (S2A2, S1A3, S3A1, or high risk (S3A3, S3A2, S2A3). RESULTS: Two hundred forty-six patients had intermediate Supp-SM grade AVMs. Of these patients, 102 had Supp-SM grade 5 (41.5%), 99 had Supp-SM grade 6 (40.2%), and 45 had Supp-SM grade 7 (18.3%). Significant differences in the proportions of patients with worse mRS scores at follow-up were found between the groups, with 24.5% (25/102) of patients in Supp-SM grade 5, 29.3% (29/99) in Supp-SM grade 6, and 57.8% (26/45) in Supp-SM grade 7 (p < 0.001). Patients with Supp-SM grade 7 AVMs had significantly increased odds of worse postoperative mRS scores (p < 0.001; OR 3.7, 95% CI 1.9-7.3). In the expanded cohort of 349 Supp-SM grade 6 AVM patients, a significantly higher proportion of older patients with larger Supp-SM grade 6 AVMs (grade 6+, 38.6%) had neurological deterioration than the others with Supp-SM grade 6 AVMs (22.9%, p = 0.02). Conversely, in an expanded cohort of 197 Supp-SM grade 7 AVM patients, a significantly lower proportion of younger patients with smaller Supp-SM grade 7 AVMs (grade 7-, 19%) had neurological deterioration than the others with Supp-SM grade 7 AVMs (44.9%, p = 0.01). CONCLUSIONS: Patients with Supp-SM grade 7 AVMs are at increased risk of worse postoperative neurological outcomes, making Supp-SM grade 6 an appropriate operability cutoff. However, young patients with small niduses in the low-risk Supp-SM grade 7 group (grade 7-) have favorable postoperative outcomes. Outcomes in Supp-SM grade 7 patients did not improve with surgeon experience, indicating that the operability boundary is a hard limit reflecting the complexity of high-grade AVMs.

Spetzler-Martin Grade III Arteriovenous Malformations: A Comparison of Modified and Supplemented Spetzler-Martin Grading Systems.

BACKGROUND: The modified Spetzler-Martin (SM) grading system proposes that grade III arteriovenous malformation (AVM) subtypes are associated with variable microsurgical risks, with small AVMs (III-) having lower risk and medium/eloquent AVMs (III+) having higher risk. Adding patient age and AVM bleeding status and compactness to the SM grade produces a score - the supplemented SM (Supp-SM) grade - to more accurately assess preoperative risk. OBJECTIVE: To compare the predictive power of the modified SM and Supp-SM grades for risk assessment in patients with grade III AVMs. METHODS: Patients with SM grade III AVMs treated between 2011 and 2018 were retrospectively reviewed. Good outcomes were defined as modified Rankin Scale (mRS) scores ≤ 2 or unchanged/improved mRS scores (pre- vs postsurgery). RESULTS: Of 102 patients with SM grade III AVMs, 59% had grade III- and 24% had grade III+ AVMs. Supp SM grade 6 and grade 7 AVMs accounted for 44% and 24%, respectively. Overall, 33% of patients worsened but outcomes did not significantly differ by SM III subtype. Neurological outcomes were associated with Supp-SM grade, with proportions of patients with worsening increasing from 0% with Supp-SM grade 4 AVMs to 54% with Supp-SM grade 7 AVMs. Analyses of factors associated with neurological worsening identified age > 60 yr and Supp-SM grade 7 as significant. CONCLUSION: Supp-SM grades were more predictive of microsurgical outcomes than modified SM grades for grade III AVMs, with a hard cutoff for acceptable surgical risk at Supp-SM grade 6. Supp-SM grading is a better decision-making tool than subtyping with the modified SM scale.

A proposal for a new arteriovenous malformation grading scale for neuroendovascular procedures and literature review.

BACKGROUND: Traditionally, decisions regarding treatment and outcomes for patients with cerebral arteriovenous malformations (AVM) have made use of the Spetzler-Martin grading scale. The latter has withstood the test of time in clinical practice for AVM patients managed surgically and even when comparing studies involving other modalities of treatment. Recent awareness on the applicability of the grading system for risk assessment and outcome determination in cases of treatment by neuroendovascular means has emerged. We propose a preliminary grading system for neuroendovascular procedures based on a revision of the available literature. METHODS: A literature search using the keywords 'arteriovenous malformation', 'embolization' and 'outcome' was done. Articles studying the factors involved in complications and outcome determination for endovascular cerebral AVM patients were reviewed. These were tabulated and those dealing with anatomical, radiological and hemodynamic descriptions that were noted as significant determinants of risk or clinical outcome were used for development of a preliminary grading system to be used in a follow-up validation study. RESULTS: A grading system similar to the Spetzler-Martin grading scale was developed using factors deemed in the literature as significant determinants of outcome. The classification includes the number of feeding vessels into the AVM, the eloquence of adjacent areas, and the presence of fistulous components. Follow-up study is underway at our institution to validate our proposal. Yet, significant evidence exists in the literature validating those factors as stand alone determinants of outcome and risk, suggesting that this grading scale may well be applicable to endovascular embolization procedures. CONCLUSIONS: A grading scale similar to the Spetzler-Martin grading system for use in risk assessment and outcome determination in brain AVM patients treated by endovascular techniques seems adequate and clinically feasible. Studies on applicability and validation are underway.

Cerebral proliferative angiopathy: clinical and angiographic description of an entity different from cerebral AVMs.

BACKGROUND AND PURPOSE: The purpose of this article is to describe "cerebral proliferative angiopathy" (CPA) as a clinical entity, which may be regarded as separate from "classical" brain AVMs in angioarchitecture, natural history, clinical presentation, and, therefore, treatment and which can be discerned from other cerebral AVMs by characteristic imaging features. METHODS: In a prospectively entered databank encompassing 1434 patients with brain AVMs, a subgroup of 49 patients harboring specific angiographic characteristics were identified. Their charts and imaging films were retrospectively reviewed. RESULTS: We found a preponderance of CPA in young (mean age: 22) females (67%). Clinical symptoms were seizures, disabling headaches, and stroke-like symptoms; hemorrhagic presentations were exceptional. On cross-sectional imaging, CPA demonstrated as a diffuse network of densely enhancing vascular spaces with intermingled normal brain parenchyma. The discrepancy between the large size of the nidus and the small shunting volume, the absence of flow-related aneurysms, the presence of diffuse angiogenesis (eg, transdural supply, progressive arterial occlusion), and the small calibre of a multitude of feeding arteries and draining veins were the angiographic hallmarks of this disease. CONCLUSIONS: The diffuse angiogenetic activity is presumably related to reduced perinidal perfusion and subsequent chronic cortical ischemia. Natural history demonstrates a low risk of hemorrhage. CPA may be regarded as a separate clinical entity different to "classical" cerebral AVMs, because normal brain is interspersed with the abnormal vascular channels increasing the risk of neurological deficit in aggressive treatments, which in the light of the natural history does not seem to be indicated.

Cerebral arteriovenous malformation: Spetzler-Martin classification at subsecond-temporal-resolution four-dimensional MR angiography compared with that at DSA.

PURPOSE: To prospectively test the hypothesis that subsecond-temporal-resolution four-dimensional (4D) contrast material-enhanced magnetic resonance (MR) angiography at 3.0 T enables the same Spetzler-Martin classification (nidus size, venous drainage, eloquence) of cerebral arteriovenous malformation (AVM) as that at digital subtraction angiography (DSA). MATERIALS AND METHODS: Institutional ethics committee approval and written informed consent were obtained. In a prospective intraindividual comparative study, 18 consecutive patients with cerebral AVM (nine men, nine women; mean age, 41.9 years +/- 14.0 [standard deviation]; range, 23-69 years) were examined with 4D contrast-enhanced MR angiography and DSA. Four-dimensional contrast-enhanced MR angiography combined randomly segmented central k-space ordering, keyhole imaging, sensitivity encoding, and half-Fourier imaging, which yielded a total acceleration factor of 60. Fifty dynamic scans were obtained every 608 msec at an acquired spatial resolution of 1.1 x 1.4 x 1.1 mm. Four-dimensional contrast-enhanced MR angiograms were independently reviewed by one neuroradiologist and one neurosurgeon according to Spetzler-Martin classification, overall diagnostic quality, and level of confidence. Kendall W coefficients of concordance (K) were computed to compare reader assessment of image quality, level of confidence, and Spetzler-Martin classification by using 4D contrast-enhanced MR angiography and to compare Spetzler-Martin classification as determined with DSA with that at 4D contrast-enhanced MR angiography. RESULTS: Spetzler-Martin classification of cerebral AVM at 4D contrast-enhanced MR angiography and at DSA matched in 18 of 18 patients for both readers, which yielded 100% interobserver agreement (K = 1). Image quality of 4D contrast-enhanced MR angiography was judged to be at least adequate for diagnosis in all patients by both readers. In three of 18 patients, DSA depicted additional arterial feeders of cerebral AVM. CONCLUSION: Subsecond-temporal-resolution 4D contrast-enhanced MR angiography at 3.0 T had 100% agreement with DSA with regard to Spetzler-Martin classification of cerebral AVM. SUPPLEMENTAL MATERIAL: radiology.rsnajnls.org/cgi/content/full/2453061684/DC1.

Venous-predominant parenchymal arteriovenous malformation: a rare subtype with a venous drainage pattern mimicking developmental venous anomaly.

OBJECT: Considerable confusion exists in the literature regarding the classification of cerebrovascular malformations and their clinical significance. One example is provided by the atypical developmental venous anomaly (DVA) with arteriovenous shunt, because it remains controversial whether these lesions should be classified as DVAs or as atypical cases of other subtypes of cerebrovascular malformations. The purpose of this study was to clarify the classification of these challenging vascular lesions in an effort to suggest an appropriate diagnosis and management strategy. METHODS: The authors present a series of 15 patients with intracranial vascular malformations that were angiographically classified as atypical DVAs with arteriovenous shunts. This type of vascular malformation shows a fine arterial blush without a distinct nidus and early filling of dilated medullary veins that drain these arterial components during the arterial phase on angiography. Those prominent medullary veins converge toward an enlarged main draining vein, which together form the caput medusae appearance of a typical DVA. RESULTS: Based on clinical, angiographic, surgical, and histological findings, the authors propose classifying these vascular malformations as a subtype of an arteriovenous malformation (AVM), rather than as a variant of DVA or as a combined vascular malformation. CONCLUSIONS: Correct recognition of this AVM subtype is required for its proper management, and its clinical behavior appears to follow that of a typical AVM. Gamma Knife radiosurgery appears to be a good alternative to resection, although long-term follow-up results require verification.

Multimodality treatment of posterior fossa arteriovenous malformations.

OBJECT: Posterior fossa arteriovenous malformations (AVMs) are relatively uncommon and often difficult to treat. The authors present their experience with multimodality treatment of 76 posterior fossa AVMs, with an emphasis on Spetzler-Martin Grades III-V AVMs. METHODS: Seventy-six patients with posterior fossa AVMs treated with radiosurgery, surgery, and endovascular techniques were analyzed. RESULTS: Between 1982 and 2006, 36 patients with cerebellar AVMs, 33 with brainstem AVMs, and 7 with combined cerebellar-brainstem AVMs were treated. Natural history data were calculated for all 76 patients. The risk of hemorrhage from presentation until initial treatment was 8.4% per year, and it was 9.6% per year after treatment and before obliteration. Forty-eight patients had Grades III-V AVMs with a mean follow-up of 4.8 years (range 0.1-18.4 years, median 3.1 years). Fifty-two percent of patients with Grades III-V AVMs had complete obliteration at the last follow-up visit. Three (21.4%) of 14 patients were cured with a single radiosurgery treatment, and 4 (28.6%) of 14 with 1 or 2 radiosurgery treatments. Twenty-one (61.8%) of 34 patients were cured with multimodality treatment. The mean Glasgow Outcome Scale (GOS) score after treatment was 3.8. Multivariate analysis performed in the 48 patients with Grades III-V AVMs showed radiosurgery alone to be a negative predictor of cure (p = 0.0047). Radiosurgery treatment alone was not a positive predictor of excellent clinical outcome (GOS Score 5; p > 0.05). Nine (18.8%) of 48 patients had major neurological complications related to treatment. CONCLUSIONS: Single-treatment radiosurgery has a low cure rate for posterior fossa Spetzler-Martin Grades III-V AVMs. Multimodality therapy nearly tripled this cure rate, with an acceptable risk of complications and excellent or good clinical outcomes in 81% of patients. Radiosurgery alone should be used for intrinsic brainstem AVMs, and multimodality treatment should be considered for all other posterior fossa AVMs.

A comprehensive review of radiosurgery for cerebral arteriovenous malformations: outcomes, predictive factors, and grading scales.

The management of cerebral arteriovenous malformations (AVMs) continues to present a challenge to neurosurgeons. The natural history of this condition, as well as the morbidity and mortality of therapeutic interventions, remains incompletely elucidated. Predictive factors and grading scales in AVM management allow risk-benefit analysis of treatment options and comparison of outcomes. Stereotactic radiosurgery is one of the established treatment modalities for AVMs and is generally used to treat lesions that are high risk for surgical resection. Radiosurgery aims to obliterate AVMs and thus prevent hemorrhage or seizure without any new or worsening of existing symptoms. Lesion characteristics and postsurgical complications differ markedly in patientstreated by radiosurgery versus microsurgery. Radiosurgery-based grading systems account for factors that have been associated with various aspects of radiosurgical outcomes including obliteration, hemorrhage, and postoperative complications, particularly those induced by radiation. The purpose of this paper is to describe the most current predictive factors and grading systems for radiosurgical treatment of cerebral AVMs.

Intracranial dural arterio-venous fistula.

Intracranial dural arteriovenous fistulae are rare, acquired lesions that may present with intracranial haemorrhage or progressive neurological deficits. Their cause is uncertain, although they are often associated with intracranial venous thrombosis. Their importance lies in the fact that they are potentially curable by endovascular or neurosurgical procedures, but easily missed on routine brain imaging. In addition, clinical presentation is variable, with no easily recognisable "syndrome". A high index of suspicion is therefore required, as well as familiarity with the characteristic radiological abnormalities seen on appropriate imaging.

Transdural Blood Supply in Cerebral Arteriovenous Malformations: A Systematic Evaluation of Angioarchitecture.

BACKGROUND AND PURPOSE: Arterial transdural blood supply is a rare angiographic phenomenon in cerebral AVMs. This study aimed to evaluate angiographic transdural blood supply characteristics and to describe the clinical peculiarities of these lesions. MATERIALS AND METHODS: A prospective AVM data base of 535 patients, enrolled from 1990 to 2016, was analyzed retrospectively. Clinical information was reviewed through patients' medical charts and radiologic studies. Patients with previous AVM treatment were excluded (n = 28). RESULTS: Patients with (n = 32, male/female ratio = 10:22; mean age, 46 ± 15 years; range, 13-75 years) and without transdural blood supply (n = 475, male/female ratio = 260:215; mean age, 40 ± 18 years; range, 2-87 years) did not show significant differences in clinical presentation (age, hemorrhage, seizures, chronic headache). The predominant nidus size in patients with transdural blood supply was ≥30 mm, with significantly more patients with large AVMs (>60 mm, P = .001). To describe the transdural blood supply, we used 3 grades based on the angiographic transdural blood supply proportion and intensity of AVM nidus perfusion (I-III). Fifty-seven percent of patients with chronic headache had a strong and substantial transdural nidus perfusion (III) and a high-flow transdural blood supply. CONCLUSIONS: Cerebral AVMs with transdural blood supply represent a rare and heterogeneous subgroup. Lesions can be graded by quantifying the transdural blood supply of the nidus and by capturing hemodynamic characteristics. The broad spread of angiographic features and comparable clinical patterns of patients with or without transdural blood supply raises questions about the relevance of the transdural blood supply to the natural history risk of an AVM and the intention for treatment.

Stereotactic radiosurgery for Spetzler-Martin Grade IV and V arteriovenous malformations: an international multicenter study.

OBJECTIVE Due to the complexity of Spetzler-Martin (SM) Grade IV-V arteriovenous malformations (AVMs), the management of these lesions remains controversial. The aims of this multicenter, retrospective cohort study were to evaluate the outcomes after single-session stereotactic radiosurgery (SRS) for SM Grade IV-V AVMs and determine predictive factors. METHODS The authors retrospectively pooled data from 233 patients (mean age 33 years) with SM Grade IV (94.4%) or V AVMs (5.6%) treated with single-session SRS at 8 participating centers in the International Gamma Knife Research Foundation. Pre-SRS embolization was performed in 71 AVMs (30.5%). The mean nidus volume, SRS margin dose, and follow-up duration were 9.7 cm3, 17.3 Gy, and 84.5 months, respectively. Statistical analyses were performed to identify factors associated with post-SRS outcomes. RESULTS At a mean follow-up interval of 84.5 months, favorable outcome was defined as AVM obliteration, no post-SRS hemorrhage, and no permanently symptomatic radiation-induced changes (RIC) and was achieved in 26.2% of patients. The actuarial obliteration rates at 3, 7, 10, and 12 years were 15%, 34%, 37%, and 42%, respectively. The annual post-SRS hemorrhage rate was 3.0%. Symptomatic and permanent RIC occurred in 10.7% and 4% of the patients, respectively. Only larger AVM diameter (p = 0.04) was found to be an independent predictor of unfavorable outcome in the multivariate logistic regression analysis. The rate of favorable outcome was significantly lower for unruptured SM Grade IV-V AVMs compared with ruptured ones (p = 0.042). Prior embolization was a negative independent predictor of AVM obliteration (p = 0.024) and radiologically evident RIC (p = 0.05) in the respective multivariate analyses. CONCLUSIONS In this multi-institutional study, single-session SRS had limited efficacy in the management of SM Grade IV-V AVMs. Favorable outcome was only achieved in a minority of unruptured SM Grade IV-V AVMs, which supports less frequent utilization of SRS for the management of these lesions. A volume-staged SRS approach for large AVMs represents an alternative approach for high-grade AVMs, but it requires further investigation.

Modern classification and outcome predictors of surgery in patients with brain arteriovenous malformations.

Brain arteriovenous malformations (bAVM) are challenging lesions. Part of this challenge stems from the infinite diversity of these lesions regarding shape, location, anatomy, and physiology. This diversity has called on a variety of treatment modalities for these lesions, of which microsurgical resection prevails as the mainstay of treatment. As such, outcome prediction and managing strategy mainly rely on unraveling the nature of these complex tangles and ways each lesion responds to various therapeutic modalities. This strategy needs the ability to decipher each lesion through accurate and efficient categorization. Therefore, classification schemes are essential parts of treatment planning and outcome prediction. This article summarizes different surgical classification schemes and outcome predictors proposed for bAVMs.

Gamma knife radiosurgery for arteriovenous malformations: general principles and preliminary results in a Swiss cohort.

INTRODUCTION: Arteriovenous malformations (AVMs) are a type of vascular malformation characterised by an abnormal connection between arteries and veins, bypassing the capillary system. This absence of capillaries generates an elevated pressure (hyperdebit), in both the AVM and the venous drainage, increasing the risk of rupture. Management modalities are: observation, microsurgical clipping, endovascular treatment and radiosurgery. The former can be used alone or in the frame of a multidisciplinary approach. We review our single-institution experience with gamma knife radiosurgery (GKR) over a period of 5 years. MATERIALS AND METHODS: The study was open-label, prospective and nonrandomised. Fifty-seven consecutive patients, benefitting from 64 GKR treatments, were included. All were treated with Leksell Gamma Knife Perfexion (Elekta Instruments, AB, Sweden) between July 2010 and August 2015. All underwent stereotactic multimodal imaging: standard digital subtraction angiography, magnetic resonance imaging and computed tomography angiography. We report obliteration rates, radiation-induced complications and haemorrhages during follow-up course. RESULTS: The mean age was 46 years (range 13-79 years). The mean follow-up period was 36.4 months (median 38, range 12-75 months). Most common pretherapeutic clinical presentation was haemorrhage (50%). The most common Pollock-Flickinger score was between 1.01 and 1.5 (46%) and Spetzler-Martin grade III (46%). In 39 (60.1%) of cases, GKR was performed as upfront therapeutic option. The mean gross target volume (GTV) was 2.3 ml (median 1.2, range 0.03-11.3 ml). Mean marginal dose was 22.4 Gy (median 24, range 18-24 Gy). The mean prescription isodose volume (PIV) was 2.9 ml (median 1.8, range 0.065-14.6 ml). The overall obliteration rates (all treatments combined) at 12, 24, 36, 48 and 60 months were 4.8, 16.9%, 37.4, 63.6 and 78.4%, respectively. The main predictive factors for complete obliteration were: higher mean marginal dose (23.3 vs 21.0 Gy), lower GTV (mean 1.5 vs 3.5 ml) and absence of previous embolisation (at 60 months 61.8% prior embolisation compared with 82.4% without prior embolisation) (for all p <0.05). Eight (14%) patients experienced complications after GKR. Overall definitive morbidity rate was 3.1%. No patient died from causes related to GKR. However, during the obliteration period, one case of extremely rare fatal haemorrhage occurred. CONCLUSION: Radiosurgery is a safe and effective treatment modality for intracranial AVMs in selected cases. It can be used as upfront therapy or in the frame of a combined management. Obliteration rates are high, with minimal morbidity. The treatment effect is progressive and subsequent and regular clinical and radiological follow-up is needed to evaluate this effect.