Prospective staged volume radiosurgery for large arteriovenous malformations: indications and outcomes in otherwise untreatable patients

Volume staging for arteriovenous malformation SRS treatment using VMAT

Volume staging involves dividing the target volume into smaller parts and treating each part separately. In this study, the feasibility of volume-staged stereotactic radiosurgery (VS-SRS) on a linear accelerator using volumetric modulated arc therapy (VMAT) and a frameless patient positioning system is investigated. Ten patients, previously treated with hypofractionated stereotactic radiotherapy with arteriovenous malformation (AVM) sized from 1.6 to 4.0 cm in diameter, were selected. VS-SRS plans were created with the VMAT technique on the Varian Eclipse treatment planning system (TPS) using the TrueBeam STx linear accelerator. For each patient, an AVM-VMAT set was planned with the AVM as the target and a PTV-VMAT set using the (PTV = AVM+1 mm) as the target. All targets were divided into two sub-volumes. The TPS data from the AVM-VMAT plans was compared to Gamma Knife (GK) VS-SRS plan data available in the literature. The AVM-VMAT and PTV-VMAT plans were compared to investigate the effect of a 1 mm PTV margin on normal brain (NB) dose. End-to-end testing was performed using a GaFchromic EBT3 film and point-dose measurements. Dosimetric effects of multiple setups were investigated through film-to-film comparisons. Median target dose coverage, NB V_12Gy , and conformity index for the AVM-VMAT plans were 97.5%, 17 cm³ , and 0.8, respectively. PTV-VMAT plans attained comparable target dose coverage, but the average NB V_12Gy increased by 48.9% when compared to the AVM-VMAT plans. Agreement of point-dose measurements with TPS calculations was -0.6% when averaged over all patients. Gamma analysis passing rates were above 90% for all film-to-film comparisons (2%/1 mm criteria), and for the film to TPS comparison (5%/1 mm). This work suggests that VMAT is capable of producing VS-SRS plans with similar dose falloff characteristics as GK plans. NB dose depends on PTV margin size, and two-stage treatment setups do not appear to contribute additional uncertainty to treatment delivery.

Stereotactic Radio Surgery, Embolization and Conservative Management for Cerebral Arteriovenous Malformation: A New Zealand Experience of Long-Term Outcomes

OBJECTIVE

Cerebral arteriovenous malformations (AVMs) can be treated by microsurgery, stereotactic radiosurgery (SRS) as a stand-alone procedure, or combining embolization and conservative management. This single-center, retrospective review explored the outcomes of patients treated with SRS alone, embolization before SRS (ESRS), or conservative management for cerebral AVMs.

METHODS

Demographic details, Spetzler-Martin grade, SRS dose, obliteration, time to obliteration, imaging modality, rebleed, disease-specific mortality, and post-SRS complications were collected. Chi-square tests of independence and 1-way analysis of variance/Kruskal-Wallis tests were performed.

RESULTS

Two-hundred and thirty-nine patients were treated with SRS alone, 37 were treated with ESRS, and 83 were conservatively managed. Obliteration rates were 78% (SRS alone) and 70% (ESRS). Rebleed rates were comparable among SRS alone (4%), ESRS (0%), and conservative management (8%). Disease-specific mortality rates were significantly lower for SRS alone (1%) and ESRS (0%) compared with conservative management (6%, X² [2, n = 358] = 7.50, P = 0.024). Post-SRS complications occurred with SRS alone only and included radiation necrosis (n = 5), cavernous malformations (n = 2), and stroke (n = 1). Obliteration, rebleed, and disease-specific mortality rates were comparable among pediatric (<18 years), nonelderly (18-59 years), and elderly (≥60 years) age groups.

CONCLUSIONS

Findings suggest that SRS and ESRS are safe and effective treatments for cerebral AVM (when quantified by obliteration, rebleed, and disease-specific mortality rates). With multinational, prospective, randomized controlled trials with long follow-up periods, the effectiveness and safety of SRS and ESRS compared with conservative management for AVM will be further clarified.

Seizure Outcomes After Interventional Treatment in Cerebral Arteriovenous Malformation-Associated Epilepsy: A Systematic Review and Meta-Analysis

BACKGROUND

Seizures are the second most common presenting symptom of cerebral arteriovenous malformations (AVMs). Evidence supporting different treatment modalities is continuously evolving and it remains unclear which modality offers better seizure outcomes.

OBJECTIVE

To compare various interventional treatment modalities (i.e., microsurgery, radiosurgery, endovascular embolization, or multimodality treatment), regarding outcomes in AVM-associated epilepsy.

METHODS

PubMed, Embase, and Web of Science were searched on December 31, 2020 for studies that evaluated outcomes in patients with AVM-associated epilepsy after undergoing different treatment modalities. Pooled analysis was performed using a random-effects model and stratified by different modalities.

RESULTS

Forty-nine studies including 2668 patients were included. Interventional management was associated with a 56.0% probability of seizure freedom and a 73.0% probability of seizure improvement. The probability of discontinuing antiepileptic drugs was estimated at 38.0%. The stratified analysis showed that microsurgery was associated with a higher probability of seizure freedom and seizure improvement than was radiosurgery, endovascular, or multimodality treatment. The probability of antiepileptic drug cessation was also higher after microsurgery compared with radiation therapy; however, only clinical but not statistical significance could be inferred because of the lack of comparative analyses.

CONCLUSIONS

Interventional management of AVM-related epilepsy was associated with seizure freedom and seizure improvement in 56% and 73% of cases. Microsurgery seemed to be associated with a higher incidence of seizure freedom and seizure improvement than did other modalities. Future well-designed comparative studies are needed to draw definitive conclusions regarding each modality.

The predictors of clinical outcomes in brainstem arteriovenous malformations after stereotactic radiosurgery

The brainstem arteriovenous malformations (BS-AVMs) have a high morbidity and mortality and stereotactic radiosurgery (SRS) has been widely used to treat BS-AVMs. However, no consensus is reached in the explicit predictors of obliteration for BS-AVMs after SRS.To identify the predictors of clinical outcomes for BS-AVMs treated by SRS, we performed a retrospective observational study of BS-AVMs patients treated by SRS at our institution from 2006 to 2016. The primary outcomes were obliteration of nidus and favorable outcomes (AVM nidus obliteration with mRS score ≤2). For getting the outcomes more accurate, we also pooled the results of previous studies as well as our study by meta-analysis.A total of 26 patients diagnosed with BS-AVMs, with mean volume of 2.6 ml, were treated with SRS. Hemorrhage presentation accounted for 69% of these patients. Overall obliteration rate was 42% with mean follow-up of more than five years and two patients (8%) had a post-SRS hemorrhage. Favorable outcomes were observed in 8 patients (31%). Higher margin dose (>15Gy) was associated with higher obliteration (P = .042) and small volume of nidus was associated with favorable outcomes (P = .036). After pooling the results of 7 studies and present study, non-prior embolization (P = .049) and higher margin dose (P = .04) were associated with higher obliteration rate, in addition, the lower Virginia Radiosurgery AVM Scale (VRAS) was associated with favorable outcomes (P = .02) of BS-AVMs after SRS.In the BS-AVMs patients treated by SRS, higher margin dose (19-24Gy) and non-prior embolization were the independent predictors of higher obliteration rate. In addition, smaller volume of nidus and lower VRAS were the potential predictors of long-term favorable outcomes for these patients.

Radiosurgery for Cerebral Arteriovenous Malformation (AVM) : Current Treatment Strategy and Radiosurgical Technique for Large Cerebral AVM

Arteriovenous malformations (AVMs) are congenital anomalies of the cerebrovascular system. AVM harbors 2.2% annual hemorrhage risk in unruptured cases and 4.5% annual hemorrhage risk of previously ruptured cases. Stereotactic radiosurgery (SRS) have been shown excellent treatment outcomes for patients with small- to moderated sized AVM which can be achieved in 80–90% complete obliteration rate with a 2–3 years latency period. The most important factors are associated with obliteration after SRS is the radiation dose to the AVM. In our institutional clinical practice, now 22 Gy (50% isodose line) dose of radiation has been used for treatment of cerebral AVM in single-session radiosurgery. However, dose-volume relationship can be unfavorable for large AVMs when treated in a single-session radiosurgery, resulting high complication rates for effective dose. Thus, various strategies should be considered to treat large AVM. The role of pre-SRS embolization is permanent volume reduction of the nidus and treat high-risk lesion such as AVM-related aneurysm and high-flow arteriovenous shunt. Various staging technique of radiosurgery including volume-staged radiosurgery, hypofractionated radiotherapy and dose-staged radiosurgery are possible option for large AVM. The incidence of post-radiosurgery complication is varied, the incidence rate of radiological post-radiosurgical complication has been reported 30–40% and symptomatic complication rate was reported from 8.1% to 11.8%. In the future, novel therapy which incorporate endovascular treatment using liquid embolic material and new radiosurgical technique such as gene or cytokine-targeted radio-sensitization should be needed.

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

How to improve obliteration rates during volume-staged stereotactic radiosurgery for large arteriovenous malformations

OBJECTIVE

The management of large-volume arteriovenous malformations (AVMs) with stereotactic radiosurgery (SRS) remains challenging. The authors retrospectively tested the hypothesis that AVM obliteration rates can be improved by increasing the percentage volume of an AVM that receives a minimal threshold dose of radiation.

METHODS

In 1992, the authors prospectively began to stage anatomical components in order to deliver higher single doses to AVMs > 15 cm3 in volume. Since that time 60 patients with large AVMs have undergone volume-staged SRS (VS-SRS). The median interval between the first stage and the second stage was 4.5 months (2.8-13.8 months). The median target volume was 11.6 cm3 (range 4.3-26 cm3) in the first-stage SRS and 10.6 cm3 (range 2.8-33.7 cm3) in the second-stage SRS. The median margin dose was 16 Gy (range 13-18 Gy) for both SRS stages.

RESULTS

AVM obliteration after the initial two staged volumetric SRS treatments was confirmed by MRI alone in 4 patients and by angiography in 11 patients at a median follow-up of 82 months (range 0.4-206 months) after VS-SRS. The post-VS-SRS obliteration rates on angiography were 4% at 3 years, 13% at 4 years, 23% at 5 years, and 27% at 10 years. In multivariate analysis, only ≥ 20-Gy volume coverage was significantly associated with higher total obliteration rates confirmed by angiography. When the margin dose is ≥ 17 Gy and the 20-Gy SRS volume included ≥ 63% of the total target volume, the angiographically confirmed obliteration rates increased to 61% at 5 years and 70% at 10 years.

CONCLUSIONS

The outcomes of prospective VS-SRS for large AVMs can be improved by prescribing an AVM margin dose of ≥ 17 Gy and adding additional isocenters so that ≥ 63% of the internal AVM dose receives more than 20 Gy.

Volume-staged versus dose-staged stereotactic radiosurgery outcomes for large brain arteriovenous malformations: a systematic review

OBJECTIVE

Several recent studies have improved our understanding of the outcomes of volume-staged (VS) and dose-staged (DS) stereotactic radiosurgery (SRS) for the treatment of large (volume > 10 cm3) brain arteriovenous malformations (AVMs). In light of these recent additions to the literature, the aim of this systematic review is to provide an updated comparison of VS-SRS and DS-SRS for large AVMs.

METHODS

A systematic review of the literature was performed using PubMed to identify cohorts of 5 or more patients with large AVMs who had been treated with VS-SRS or DS-SRS. Baseline data and post-SRS outcomes were extracted for analysis.

RESULTS

A total of 11 VS-SRS and 10 DS-SRS studies comprising 299 and 219 eligible patients, respectively, were included for analysis. The mean obliteration rates for VS-SRS and DS-SRS were 41.2% (95% CI 31.4%–50.9%) and 32.3% (95% CI 15.9%–48.8%), respectively. Based on pooled individual patient data, the outcomes for patients treated with VS-SRS were obliteration in 40.3% (110/273), symptomatic radiation-induced changes (RICs) in 13.7% (44/322), post-SRS hemorrhage in 19.5% (50/256), and death in 7.4% (24/323); whereas the outcomes for patients treated with DS-SRS were obliteration in 32.7% (72/220), symptomatic RICs in 12.2% (31/254), post-SRS hemorrhage in 10.6% (30/282), and death in 4.6% (13/281).

CONCLUSIONS

Volume-staged SRS appears to afford higher obliteration rates than those achieved with DS-SRS, although with a less favorable complication profile. Therefore, VS-SRS or DS-SRS may be a reasonable treatment approach for large AVMs, either as stand-alone therapy or as a component of a multimodality management strategy.

Volume-Staged Stereotactic Radiosurgery for Intracranial Arteriovenous Malformations: Outcomes Based on an 18-Year Experience

BACKGROUND

Radiation-based treatment options of large intracranial arteriovenous malformations (AVM) must balance the likelihood of obliteration with the risk of adverse radiation effects (ARE).

OBJECTIVE

To analyze the efficacy and risks of volume-staged stereotactic radiosurgery (VS-SRS) for AVM.

METHODS

Retrospective study of 34 AVM patients having VS-SRS between 1997 and 2012. A median of 2 stages (range, 2-4) was used to treat a median AVM volume of 22.2 cm 3 (range, 7.4-56.7). The median AVM margin dose was 16 Gy (range, 14-18); the median radiosurgery-based AVM score was 2.81 (range, 1.54-6.45). The median follow-up after VS-SRS was 8.2 years (range, 3-13.3).

RESULTS

Nidus obliteration was noted in 18 patients (53%) after VS-SRS. The rate of obliteration was 14% at 3 years, 54% at 5 years, and 75% at 7 years. Six patients (18%) had 11 bleeds after VS-SRS. Two patients (6%) remained neurologically stable, 2 (6%) patients had significant deficits, and 2 patients (6%) died. The actuarial risk of a first bleed after VS-SRS was 6% at 1 year, 12% at 3 years, and 19% at 7 years. Six patients (18%) underwent repeat SRS; all achieved nidus obliteration for an overall cure rate of 71%. Two patients (6%) had a permanent ARE after VS-SRS or repeat SRS.

CONCLUSION

VS-SRS permitted large volume intracranial AVM to be treated with a low rate of ARE. Further study is needed on dose escalation and decreasing the treatment volume per stage to determine if this will increase the rate of obliteration with this technique.

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.

Stereotactic radiosurgery for cerebellar arteriovenous malformations: an international multicenter study

OBJECTIVE

Cerebellar arteriovenous malformations (AVMs) represent the majority of infratentorial AVMs and frequently have a hemorrhagic presentation. In this multicenter study, the authors review outcomes of cerebellar AVMs after stereotactic radiosurgery (SRS).

METHODS

Eight medical centers contributed data from 162 patients with cerebellar AVMs managed with SRS. Of these patients, 65% presented with hemorrhage. The median maximal nidus diameter was 2 cm. Favorable outcome was defined as AVM obliteration and no posttreatment hemorrhage or permanent radiation-induced complications (RICs). Patients were followed clinically and radiographically, with a median follow-up of 60 months (range 7–325 months).

RESULTS

The overall actuarial rates of obliteration at 3, 5, 7, and 10 years were 38.3%, 74.2%, 81.4%, and 86.1%, respectively, after single-session SRS. Obliteration and a favorable outcome were more likely to be achieved in patients treated with a margin dose greater than 18 Gy (p < 0.001 for both), demonstrating significantly better rates (83.3% and 79%, respectively). The rate of latency preobliteration hemorrhage was 0.85%/year. Symptomatic post-SRS RICs developed in 4.5% of patients (n = 7). Predictors of a favorable outcome were a smaller nidus (p = 0.0001), no pre-SRS embolization (p = 0.003), no prior hemorrhage (p = 0.0001), a higher margin dose (p = 0.0001), and a higher maximal dose (p = 0.009). The Spetzler-Martin grade was not found to be predictive of outcome. The Virginia Radiosurgery AVM Scale score (p = 0.0001) and the Radiosurgery-Based AVM Scale score (p = 0.0001) were predictive of a favorable outcome.

CONCLUSIONS

SRS results in successful obliteration and a favorable outcome in the majority of patients with cerebellar AVMs. Most patients will require a nidus dose of higher than 18 Gy to achieve these goals. Radiosurgical and not microsurgical scales were predictive of clinical outcome after SRS.

Stereotactic Radiosurgery for Brainstem Arteriovenous Malformations: A Multicenter Study

BACKGROUND

The management of brainstem arteriovenous malformations (bAVMs) is a formidable challenge. bAVMs harbor higher morbidity and mortality compared to other locations.

OBJECTIVE

To review the outcomes following stereotactic radiosurgery (SRS) of bAVMs in a multicenter study.

METHODS

Six medical centers contributed data from 205 patients through the International Gamma Knife Research Foundation. Median age was 32 yr (6-81). Median nidus volume was 1.4 mL (0.1-69 mL). Favorable outcome (FO) was defined as AVM obliteration and no post-treatment hemorrhage or permanent symptomatic radiation-induced complications.

RESULTS

Overall obliteration was reported in 65.4% (n = 134) at a mean follow-up of 69 mo. Obliteration was angiographically proven in 53.2% (n = 109) and on MRA in 12.2% (n = 25). Actuarial rate of obliteration at 2, 3, 5, 7, and 10 yr after SRS was 24.5%, 43.3%, 62.3%, 73%, and 81.8% respectively. Patients treated with a margin dose &gt;20 Gy were more likely to achieve obliteration (P = .001). Obliteration occurred earlier in patients who received a higher prescribed margin dose (P = .05) and maximum dose (P = .041). Post-SRS hemorrhage occurred in 8.8% (n = 18). Annual postgamma knife latency period hemorrhage was 1.5%. Radiation-induced complications were radiologically evident in 35.6% (n = 73), symptomatic in 14.6% (n = 30), and permanent in 14.6% (n = 30, which included long-tract signs and new cranial nerve deficits). FO was achieved in 64.4% (n = 132). Predictors of an FO were a higher Virginia radiosurgery AVM scale score (P = .003), prior hemorrhage (P = .045), and a lower prescribed maximum dose (P = .006).

CONCLUSION

SRS for bAVMs results in obliteration and avoids permanent complications in the majority of patients.

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

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

Staged-Volume Radiosurgery of Large Arteriovenous Malformations Improves Outcome by Reducing the Rate of Adverse Radiation Effects

BACKGROUND: The treatment of large arteriovenous malformations (AVMs) remains challenging. Recently, staged-volume radiosurgery (SVRS) has become an option.

OBJECTIVE: To compare the outcome of SVRS on large AVMs with our historical, single-stage radiosurgery (SSRS) series.

METHODS: We have been prospectively collecting data of patients treated by SVRS since 2007. There were 84 patients who had a median age of 37 years (range, 9-62 years) who were treated until July 2013. The outcomes of 76 of those who had follow-ups available were analyzed and compared with the outcomes of 122 patients treated with the best SSRS technique.

RESULTS: There were 21.5% of AVMs that were deep seated, and 44% presented with hemorrhage resulting in 45% fixed neurological deficit. There were 14% of patients who had undergone embolization before radiosurgery. The median nidus treatment volume was 19.7 cm3 (6.65-68.7) and 17.5 Gy (13-22.5) prescription isodose was given. Of the 44 lesions having radiological follow-up at 4 years, 61.4% were completely obliterated. Previous embolization (50% with and 63% without) and higher Spetzler-Martin grades appeared to be the negative factors in successful obliteration, but treatment volume was not. Within 3 years after radiosurgery, the annual bleed rates of unruptured and previously ruptured AVMs were 3.2% and 5.6%, respectively. Three bleeds were fatal and 2 resulted in significant modified Rankin scale 3 morbidity. These rates differ little from SSRS. Temporary adverse radiation effects (AREs) did not change significantly, but permanent AREs dropped from 15% to 6.5% (P = .03) compared with SSRS.

CONCLUSION: Obliteration and hemorrhage rates of large AVMs treated by SVRS are similar to historical SSRS. However, SVRS offers a lower rate of AREs.

Time-Staged Gamma Knife Stereotactic Radiosurgery for Large Cerebral Arteriovenous Malformations: A Preliminary Report

OBJECTIVE

We retrospectively analyzed our experience with time-staged gamma knife stereotactic radiosurgery (GKS) in treating large arteriovenous malformation(AVM)s;≥ 10 cm3).

METHODS

Forty-five patients who underwent time-staged GKS (2-stage, n = 37;3-stage,n = 8) between March 1998 and December 2011 were included. The mean volume treated was 20.42±6.29 cm3 (range, 10.20-38.50 cm3). Obliteration rates of AVMs and the associated complications after GKS were evaluated.

RESULTS

Mean AVM volume (and median marginal dose) at each GKS session in the 37 patients who underwent 2-stage GKS was 19.67±6.08 cm3 (13 Gy) at session 1 and 6.97±6.92 cm3 (17 Gy) at session 2. The median interval period was 39 months. After follow-up period of 37 months, the complete obliteration rate was 64.9%. The mean AVM volume (and median marginal dose) at each GKS session in the 8 patients who underwent 3-stage GKS was 23.90±6.50 cm3 (12.25 Gy), 19.43±7.46 cm3 (13.5 Gy), 7.48±6.86 cm3 (15.5 Gy) at session 1, 2, and 3, respectively. The median interval duration between each GKS session was 37.5 and 38 months, respectively. After a median follow-up period of 47.5 months, 5 patients (62.5%) achieved complete obliteration. Postradiosurgical hemorrhage developed in 5 patients (11.1%) including one case of major bleeding and 4 cases of minor bleeding. No patient suffered from clinically symptomatic radiation necrosis following radiation.

CONCLUSION

Time-staged GKS could be an effective and safe treatment option in the management of large AVMs.

Volume-staged radiosurgery for large arteriovenous malformations: an evolving paradigm

OBJECT

Large arteriovenous malformations (AVMs) remain difficult to treat, and ideal treatment parameters for volume-staged stereotactic radiosurgery (VS-SRS) are still unknown. The object of this study was to compare VS-SRS treatment outcomes for AVMs larger than 10 ml during 2 eras; Era 1 was 1992-March 2004, and Era 2 was May 2004–2008. In Era 2 the authors prospectively decreased the AVM treatment volume, increased the radiation dose per stage, and shortened the interval between stages.

METHODS

All cases of VS-SRS treatment for AVM performed at a single institution were retrospectively reviewed.

RESULTS

Of 69 patients intended for VS-SRS, 63 completed all stages. The median patient age at the first stage of VS-SRS was 34 years (range 9–68 years). The median modified radiosurgery-based AVM score (mRBAS), total AVM volume, and volume per stage in Era 1 versus Era 2 were 3.6 versus 2.7, 27.3 ml versus 18.9 ml, and 15.0 ml versus 6.8 ml, respectively. The median radiation dose per stage was 15.5 Gy in Era 1 and 17.0 Gy in Era 2, and the median clinical follow-up period in living patients was 8.6 years in Era 1 and 4.8 years in Era 2. All outcomes were measured from the first stage of VS-SRS. Near or complete obliteration was more common in Era 2 (log-rank test, p = 0.0003), with 3- and 5-year probabilities of 5% and 21%, respectively, in Era 1 compared with 24% and 68% in Era 2. Radiosurgical dose, AVM volume per stage, total AVM volume, era, compact nidus, Spetzler-Martin grade, and mRBAS were significantly associated with near or complete obliteration on univariate analysis. Dose was a strong predictor of response (Cox proportional hazards, p < 0.001, HR 6.99), with 3- and 5-year probabilities of near or complete obliteration of 5% and 16%, respectively, at a dose < 17 Gy versus 23% and 74% at a dose ≥ 17 Gy. Dose per stage, compact nidus, and total AVM volume remained significant predictors of near or complete obliteration on multivariate analysis. Seventeen patients (25%) had salvage surgery, SRS, and/or embolization. Allowing for salvage therapy, the probability of cure was more common in Era 2 (log-rank test, p = 0.0007) with 5-year probabilities of 0% in Era 1 versus 41% in Era 2. The strong trend toward improved cure in Era 2 persisted on multivariate analysis even when considering mRBAS (Cox proportional hazards, p = 0.055, HR 4.01, 95% CI 0.97–16.59). The complication rate was 29% in Era 1 compared with 13% in Era 2 (Cox proportional hazards, not significant).

CONCLUSIONS

VS-SRS is an option to obliterate or downsize large AVMs. Decreasing the AVM treatment volume per stage to ≤ 8 ml with this technique allowed a higher dose per fraction and decreased time to response, as well as improved rates of near obliteration and cure without increasing complications. Reducing the volume of these very large lesions can facilitate a surgical approach for cure.

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.

Volume-staged versus dose-staged radiosurgery outcomes for large intracranial arteriovenous malformations

OBJECT

The aim in this paper was to compare the outcomes of dose-staged and volume-staged stereotactic radio-surgery (SRS) in the treatment of large (> 10 cm(3)) arteriovenous malformations (AVMs).

METHODS

A systematic literature review was performed using PubMed. Studies written in the English language with at least 5 patients harboring large (> 10 cm(3)) AVMs treated with dose- or volume-staged SRS that reported post-treatment outcomes data were selected for review. Demographic information, radiosurgical treatment parameters, and post-SRS outcomes and complications were analyzed for each of these studies.

RESULTS

The mean complete obliteration rates for the dose- and volume-staged groups were 22.8% and 47.5%, respectively. Complete obliteration was demonstrated in 30 of 161 (18.6%) and 59 of 120 (49.2%) patients in the dose- and volume-staged groups, respectively. The mean rates of symptomatic radiation-induced changes were 13.5% and 13.6% in dose- and volume-staged groups, respectively. The mean rates of cumulative post-SRS latency period hemorrhage were 12.3% and 17.8% in the dose- and volume-staged groups, respectively. The mean rates of post-SRS mortality were 3.2% and 4.6% in dose- and volume-staged groups, respectively.

CONCLUSIONS

Volume-staged SRS affords higher obliteration rates and similar complication rates compared with dose-staged SRS. Thus, volume-staged SRS may be a superior approach for large AVMs that are not amenable to single-session SRS. Staged radiosurgery should be considered as an efficacious component of multimodality AVM management.

Diagnosis and evaluation of intracranial arteriovenous malformations

BACKGROUND

Ideal management of intracranial arteriovenous malformations (AVMs) remains poorly defined. Decisions regarding management of AVMs are based on the expected natural history of the lesion and risk prediction for peritreatment morbidity. Microsurgical resection, stereotactic radiosurgery, and endovascular embolization alone or in combination are all viable treatment options, each with different risks. The authors attempt to clarify the existing literature's understanding of the natural history of intracranial AVMs, and risk-assessment grading scales for each of the three treatment modalities.

METHODS

The authors conducted a literature review of the existing AVM natural history studies and studies that clarify the utility of existing grading scales available for the assessment of peritreatment risk for all three treatment modalities.

RESULTS

The authors systematically outline the diagnosis and evaluation of patients with intracranial AVMs and clarify estimation of the expected natural history and predicted risk of treatment for intracranial AVMs.

CONCLUSION

AVMs are a heterogenous pathology with three different options for treatment. Accurate assessment of risk of observation and risk of treatment is essential for achieving the best outcome for each patient.

A treatment paradigm for high-grade brain arteriovenous malformations: volume-staged radiosurgical downgrading followed by microsurgical resection

OBJECT

The surgical treatment of many large arteriovenous malformations (AVMs) is associated with substantial risks, and many are considered inoperable. Furthermore, AVMs larger than 3 cm in diameter are not usually treated with conventional single-session radiosurgery encompassing the entire AVM volume. Volume-staged stereotactic radiosurgery (VS-SRS) is an option for large AVMs, but it has mixed results. The authors report on a series of patients with high-grade AVMs who underwent multiple VS-SRS sessions with resultant downgrading of the AVMs, followed by resection.

METHODS

A cohort of patients was retrieved from a single-institution AVM patient registry consisting of prospectively collected data. VS-SRS was performed as a planned intentional treatment. Surgery was considered as salvage therapy in select patients.

RESULTS

Sixteen AVMs underwent VS-SRS followed by surgery. Four AVMs presented with rupture. The mean patient age was 25.3 years (range 13–54 years). The average initial Spetzler-Martin grade before any treatment was 4, while the average supplemented Spetzler-Martin grade (Spetzler-Martin plus Lawton-Young) was 7.1. The average AVM size in maximum dimension was 5.9 cm (range 3.3–10 cm). All AVMs were supratentorial in location and all except one were in eloquent areas of the brain, with 7 involving primary motor cortex. The mean number of VS-SRS sessions was 2.7 (range 2–5 sessions). The mean interval between first VS-SRS session and resection was 5.7 years. There were 4 hemorrhages that occurred after VS-SRS. The average Spetzler-Martin grade was reduced to 2.5 (downgrade, −1.5) and the average supplemented Spetzler-Martin grade was reduced to 5.6 (downgrade, −1.5). The maximum AVM size was reduced to an average of 3.0 cm (downsize = −2.9 cm). The mean modified Rankin Scale (mRS) scores were 1.2, 2.3, and 2.2 before VS-SRS, before surgery, and at last follow-up, respectively (mean follow-up, 6.9 years). Fifteen AVMs were cured after surgery. Ten patients had good outcomes at last follow-up (7 with mRS Score 0 or 1, and 3 with mRS Score 2). There were 2 deaths (both mRS Score 1 before treatment) and 4 patients with mRS Score 3 outcome (from mRS Scores 0, 1, and 2 [n = 2]).

CONCLUSIONS

Volume-staged SRS can downgrade AVMs, transforming high-grade AVMs (initially considered inoperable) into operable AVMs with acceptable surgical risks. This treatment paradigm offers an alternative to conservative observation for young patients with unruptured AVMs and long life expectancy, where the risk of hemorrhage is substantial. Difficult AVMs were cured in 15 patients. Surgical morbidity associated with downgraded AVMs is reduced to that of postradiosurgical/preoperative supplemented Spetzler-Martin grades, not their initial AVM grades.

Factors Determining the Clinical Complications of Radiosurgery for AVM

Purpose:

To identify the predictors of symptomatic post-radiation T2 signal change in patients with arteriovenous malformations (AVM) treated with radiosurgery.

Materials and Methods:

The charts of 211 consecutive patients with arteriovenous malformations treated with either gamma knife radisurgery or linear accelerator radiosurgery between 2000-2009 were retrospectively reviewed. 168 patients had a minimum of 12 months of clinical and radiologic follow-up following the procedure and complete dosage data. Pretreatment characteristics and dosimetric variables were analyzed to identify predictors of adverse radiation effects.

Results:

141 patients had no clinical symptomatic complications. 21 patients had global or focal neurological deficits attributed to symptomatic edema. Variables associated with development of symptomatic edema included a non-hemorrhagic symptomatic presentation compared to presentation with hemorrhage, p=0.001; OR (95%CI) = 6.26 (1.99, 19.69); the presence of venous rerouting compared to the lack of venous rerouting, p=0.031; OR (95% CI) = 3.25 (1.20, 8.80); radiosurgery with GKS compared to linear accelerator radiosurgery p = 0.012; OR (95% CI) = 4.58 (1.28, 16.32); and the presence of more than one draining vein compared to a single draining vein p = 0.032; OR (95% CI) = 2.82 (1.06, 7.50).

Conclusions:

We postulated that the higher maximal doses used with gamma knife radiosurgery may be responsible for the greater number of adverse radiation effects with this modality compared to linear accelerator radiosurgery. We found that AVMs with greater venous complexity and therefore instability resulted in more adverse treatment outcomes, suggesting that AVM angioarchitecture should be considered when making treatment decisions.

Radiosurgery for primary motor and sensory cortex arteriovenous malformations: outcomes and the effect of eloquent location

BACKGROUND

Eloquent intracranial arteriovenous malformations (AVMs) located in the primary motor or somatosensory cortex (PMSC) carry a high risk of microsurgical morbidity.

OBJECTIVE

To evaluate the outcomes of radiosurgery on PMSC AVMs and compare them with radiosurgery outcomes in a matched cohort of noneloquent lobar AVMs.

METHODS

Between 1989 and 2009, 134 patients with PMSC AVMs underwent Gamma Knife radiosurgery with a median radiographic and clinical follow-up of 64 and 80 months, respectively. Seizure (40.3%) and hemorrhage (28.4%) were the most common presenting symptoms. Pre-radiosurgery embolization was performed in 33.6% of AVMs. Median AVM volume was 4.1 mL (range, 0.1-22.6 mL), and prescription dose was 20 Gy (range, 7-30 Gy). Cox regression analysis was performed to identify factors associated with obliteration.

RESULTS

The overall obliteration rate, including magnetic resonance imaging and angiography, after radiosurgery was 63%. Obliteration was achieved in 80% of AVMs with a volume less than 3 mL compared with 55% for AVMs larger than 3 mL. No previous embolization (P = .002) and a single draining vein (P = .001) were independent predictors of obliteration on multivariate analysis. The annual post-radiosurgery hemorrhage risk was 2.5%. Radiosurgery-related morbidity was temporary and permanent in 14% and 6% of patients, respectively. Comparing PMSC AVMs with matched noneloquent lobar AVMs, the obliteration rates and clinical outcomes after radiosurgery were not statistically different.

CONCLUSION

For patients harboring PMSC AVMs, radiosurgery offers a reasonable chance of obliteration with a relatively low complication rate. Eloquent location does not appear to confer the same negative prognostic value for radiosurgery that it does for microsurgery.

Advances in Radiosurgery for Arteriovenous Malformations of the Brain

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

Stereotactic radiosurgery with neoadjuvant embolization of larger arteriovenous malformations: an institutional experience

OBJECTIVE

This study investigates the safety and efficacy of a multimodality approach combining staged endovascular embolizations with subsequent SRS for the management of larger AVMs.

METHODS

Ninety-five patients with larger AVMs were treated with staged endovascular embolization followed by SRS between 1996 and 2011.

RESULTS

The median volume of AVM in this series was 28 cm(3) and 47 patients (48%) were Spetzler-Martin grade IV or V. Twenty-seven patients initially presented with hemorrhage. Sixty-one patients underwent multiple embolizations while a single SRS session was performed in 64 patients. The median follow-up after SRS session was 32 months (range 9-136 months). Overall procedural complications occurred in 14 patients. There were 13 minor neurologic complications and 1 major complication (due to embolization) while four patients had posttreatment hemorrhage. Thirty-eight patients (40%) were cured radiographically. The postradiosurgery actuarial rate of obliteration was 45% at 5 years, 56% at 7 years, and 63% at 10 years. In multivariate analysis, larger AVM size, deep venous drainage, and the increasing number of embolization/SRS sessions were negative predictors of obliteration. The number of embolizations correlated positively with the number of stereotactic radiosurgeries (P < 0.005).

CONCLUSIONS

Multimodality endovascular and radiosurgical approach is an efficacious treatment strategy for large AVM.

Stereotactic radiosurgery of intracranial arteriovenous malformations

Stereotactic radiosurgery for intracranial arteriovenous malformations (AVMs) has been performed since the 1970s. When an AVM is treated with radiosurgery, radiation injury to the vascular endothelium induces the proliferation of smooth muscle cells and the elaboration of extracellular collagen, which leads to progressive stenosis and obliteration of the AVM nidus. Obliteration after AVM radiosurgery ranges from 60% to 80%, and relates to the size of the AVM and the prescribed radiation dose. The major drawback of radiosurgical AVM treatment is the risk of bleeding during the latent period (typically 2 years) between treatment and AVM thrombosis.

Radiosurgery for patients with unruptured intracranial arteriovenous malformations

Object

The appropriate management of unruptured intracranial arteriovenous malformations (AVMs) remains controversial. In the present study, the authors evaluate the radiographic and clinical outcomes of radiosurgery for a large cohort of patients with unruptured AVMs.

Methods

From a prospective database of 1204 cases of AVMs involving patients treated with radiosurgery at their institution, the authors identified 444 patients without evidence of rupture prior to radiosurgery. The patients' mean age was 36.9 years, and 50% were male. The mean AVM nidus volume was 4.2 cm3, 13.5% of the AVMs were in a deep location, and 44.4% were at least Spetzler-Martin Grade III. The median radiosurgical prescription dose was 20 Gy. Univariate and multivariate Cox regression analyses were used to determine risk factors associated with obliteration, postradiosurgery hemorrhage, radiation-induced changes, and postradiosurgery cyst formation. The mean duration of radiological and clinical follow-up was 76 months and 86 months, respectively.

Results

The cumulative AVM obliteration rate was 62%, and the postradiosurgery annual hemorrhage rate was 1.6%. Radiation-induced changes were symptomatic in 13.7% and permanent in 2.0% of patients. The statistically significant independent positive predictors of obliteration were no preradiosurgery embolization (p < 0.001), increased prescription dose (p < 0.001), single draining vein (p < 0.001), radiological presence of radiation-induced changes (p = 0.004), and lower Spetzler-Martin grade (p = 0.016). Increased volume and higher Pittsburgh radiosurgery-based AVM score were predictors of postradiosurgery hemorrhage in the univariate analysis only. Clinical deterioration occurred in 30 patients (6.8%), more commonly in patients with postradiosurgery hemorrhage (p = 0.018).

Conclusions

Radiosurgery afforded a reasonable chance of obliteration of unruptured AVMs with relatively low rates of clinical and radiological complications.

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

PURPOSE

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

RESULTS

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

CONCLUSIONS

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

Multimodality treatment for cerebral arteriovenous malformations: complementary role of proton beam radiotherapy

A total of 29 cerebral arteriovenous malformations (AVMs) treated at the University of Tsukuba with multimodality treatment including proton beam (PB) radiotherapy for cerebral AVMs between 2005 and 2011 were retrospectively evaluated. Eleven AVMs were classified as Spetzler-Martin grades I and II, 10 as grade III, and 8 as grades IV and V. For AVMs smaller than 2.5 cm and located on superficial and non-eloquent areas, surgical removal with/without embolization was offered as a first-line treatment. For some small AVMs located in deep or eloquent lesions, gamma knife (GK) radiosurgery was offered. Some AVMs were treated with only embolization. AVMs larger than 2.5 cm were embolized to achieve reduction in size, to enhance the safety of the surgery, and to render the AVM amenable to GK radiosurgery. For larger AVMs located in deep or eloquent areas, PB radiotherapy was offered with/without embolization. Immediately after the treatment, 24 patients exhibited no neurological worsening. Four patients had moderate disability, and 1 patient had severe disability. Three patients suffered brain damage after surgical resection, and 2 patients suffered embolization complications. However, no neurological worsening was observed after either GK radiosurgery or PB radiotherapy, but 3 patients treated by PB radiotherapy suffered delayed hemorrhage. Fractionated PB radiotherapy for cerebral AVMs seems to be useful for the treatment of large AVMs, but careful long-term follow up is required to establish the efficacy and safety.

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

Object

In this paper the authors' goal was to define the long-term benefits and risks of stereotactic radiosurgery (SRS) for patients with arteriovenous malformations (AVMs) who underwent prior embolization.

Methods

Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs; 120 patients underwent embolization followed by SRS. In this series, 64 patients (53%) had at least one prior hemorrhage. The median number of embolizations varied from 1 to 5. The median target volume was 6.6 cm3 (range 0.2–26.3 cm3). The median margin dose was 18 Gy (range 13.5–25 Gy).

Results

After embolization, 25 patients (21%) developed symptomatic neurological deficits. The overall rates of total obliteration documented by either angiography or MRI were 35%, 53%, 55%, and 59% at 3, 4, 5, and 10 years, respectively. Factors associated with a higher rate of AVM obliteration were smaller target volume, smaller maximum diameter, higher margin dose, timing of embolization during the most recent 10-year period (1997–2006), and lower Pollock-Flickinger score. Nine patients (8%) had a hemorrhage during the latency period, and 7 patients died of hemorrhage. The actuarial rates of AVM hemorrhage after SRS were 0.8%, 3.5%, 5.4%, 7.7%, and 7.7% at 1, 2, 3, 5, and 10 years, respectively. The overall annual hemorrhage rate was 2.7%. Factors associated with a higher risk of hemorrhage after SRS were a larger target volume and a larger number of prior hemorrhages. Permanent neurological deficits due to adverse radiation effects (AREs) developed in 3 patients (2.5%) after SRS, and 1 patient had delayed cyst formation 210 months after SRS. No patient died of AREs. A larger 12-Gy volume was associated with higher risk of symptomatic AREs. Using a case-control matched approach, the authors found that patients who underwent embolization prior to SRS had a lower rate of total obliteration (p = 0.028) than patients who had not undergone embolization.

Conclusions

In this 20-year experience, the authors found that prior embolization reduced the rate of total obliteration after SRS, and that the risks of hemorrhage during the latency period were not affected by prior embolization. For patients who underwent embolization to volumes smaller than 8 cm3, success was significantly improved. A margin dose of 18 Gy or more also improved success. In the future, the role of embolization after SRS should be explored.

Long-term Outcomes After Staged-Volume Stereotactic Radiosurgery for Large Arteriovenous Malformations

BACKGROUND:

Stereotactic radiosurgery is an effective treatment modality for small arteriovenous malformations (AVMs) of the brain. For larger AVMs, the treatment dose is often lowered to reduce potential complications, but this decreases the likelihood of cure. One strategy is to divide large AVMs into smaller anatomic volumes and treat each volume separately.

OBJECTIVE:

To prospectively assess the long-term efficacy and complications associated with staged-volume radiosurgical treatment of large, symptomatic AVMs.

METHODS:

Eighteen patients with AVMs larger than 15 mL underwent prospective staged-volume radiosurgery over a 13-year period. The median AVM volume was 22.9 mL (range, 15.7-50 mL). Separate anatomic volumes were irradiated at 3- to 9-month intervals (median volume, 10.9 mL; range, 5.3-13.4 mL; median marginal dose, 15 Gy; range, 15-17 Gy). The AVM was divided into 2 volumes in 10 patients, 3 volumes in 5 patients, and 4 volumes in 3 patients. Seven patients underwent retreatment for residual disease.

RESULTS:

Actuarial rates of complete angiographic occlusion were 29% and 89% at 5 and 10 years. Five patients (27.8%) had a hemorrhage after radiosurgery. Kaplan-Meier analysis of cumulative hemorrhage rates after treatment were 12%, 18%, 31%, and 31% at 2, 3, 5, and 10 years, respectively. One patient died after a hemorrhage (5.6%).

CONCLUSION:

Staged-volume radiosurgery for AVMs larger than 15 mL is a viable treatment strategy. The long-term occlusion rate is high, whereas the radiation-related complication rate is low. Hemorrhage during the lag period remains the greatest source of morbidity and mortality.

Embolization and radiosurgery for arteriovenous malformations

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

Stereotactic radiosurgery of cranial arteriovenous malformations and dural arteriovenous fistulas

Cranial arteriovenous malformations (AVM) and cranial dural arteriovenous fistulas (AVF) carry a significant risk of morbidity and mortality when they hemorrhage. Current treatment options include surgery, embolization, radiosurgery, or a combination of these treatments. Radiosurgery is thought to reduce the risk hemorrhage in AVMs and AVFs by obliterating of the nidus of abnormal vasculature over the course of 2 to 3 years. Success in treating AVMs is variable depending on the volume of the lesion, the radiation dose, and the pattern of vascular supply and drainage. This article discusses the considerations for selecting radiosurgery as a treatment modality in patients who present with AVMs and AVFs.