Radiosurgery For Arteriovenous Malformations Research Articles

Hyperbaric oxygen therapy in the treatment of malign edema complication after arteriovenous malformation radiosurgery

A 16-year-old female patient with headache was admitted to our hospital. Radiological examination showed a Spetzler-Martin Grade III arteriovenous malformation (AVM) located at the left frontal lobe. Volume-staged stereotactic radiosurgery (SRS) treatment performed in two fractions at three-month intervals and post-procedural period were uneventful. Eight months later the patient was admitted to our hospital with headache, vomiting, right-sided facial palsy and right upper extremity paresthesia. Radiological examination demonstrated severe vasogenic edema in the left centrum semiovale and temporal region. Due to severe and steroid-resistant malign edema, hyperbaric oxygen (HBO2) therapy was performed as an alternative treatment option. Neurological symptoms resolved completely after HBO2. Radiological examination demonstrated serious improvement of brain edema and mass effect.

136 Outcomes of Stereotactic Radiosurgery for Brain Arteriovenous Malformations: A Single Centre Experience

136 Outcomes of Stereotactic Radiosurgery for Brain Arteriovenous Malformations: A Single Centre Experience

Clinical Outcomes of Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations in Pediatric Patients: Systematic Review and Meta-Analysis

Arteriovenous malformations (AVMs) in pediatric patients exhibit remarkable differences in terms of management and outcomes. Owing to a paucity of relevant data pertaining to AVMs in pediatric patients, special interest and investigation are required for an improved understanding of the available evidence by clinicians. To determine the clinical outcomes of single-session stereotactic radiosurgery (SRS) for AVMs in pediatric patients. A systematic literature review was performed to identify studies that reported the outcomes of SRS for AVMs in pediatric patients. Data pertaining to variables such as obliteration rate, post-SRS new hemorrhage rate, post-SRS new neurological deficit rate, and mortality rate were extracted and analyzed using meta-analysis techniques. Based on pooled data from 20 studies with 1212 patients, single-session SRS resulted in complete obliteration in 65.9% (95% confidence interval [CI], 60.5%-71.1%; I2=66.5%) patients. Overall complication rate (including new hemorrhage, new neurodeficit, and mortality) was 8.0% (95% CI, 5.1%-11.5%; I2=66.4%). Post-SRS new neurological deficit rate was 3.1% (95% CI, 1.3%-5.4%; I2=59.7%), and post-SRS hemorrhage rate was 4.2% (95% CI, 2.5%-6.3%; I2=42.7%). There was no significant difference between studies disaggregated by treatment method (Gamma Knife [Elekta AB] vs other), treatment year (before year 2000 vs after year 2000), median AVM volume reported (≥3 vs<3 cm3), median dose reported (≥20 vs<20 Gy), or follow-up period (≥36 vs<36 mo). Single-SRS is a safe treatment alternative that achieves high obliteration rates and acceptable complication rates for AVMs in pediatric patients.

Evaluation of the radiosurgical treatment of cerebral arteriovenous malformations: a retrospective single-center analysis of three decades

BackgroundGamma Knife radiosurgery (GKRS) in the treatment of arteriovenous malformations (AVMs) is still controversially discussed.ObjectiveTo present long-term follow-up data on patients after Gamma Knife radiosurgery for cerebral AVMs.MethodsOverall, 516 patients...

Is Biological Effective Dose (BED) Predictive of Outcomes After Radiosurgery for Cerebral Arteriovenous Malformations?

Abstract INTRODUCTION Reports have shown that radiation dose directly correlates with the chance of nidus obliteration after stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs). However, recent studies have shown that the rate of obliteration was greater in patients having SRS before 2000. As the effect of radiation on cell viability is both dose- and time-dependent, one explanation may be that contemporary SRS, which utilizes more isocenters of radiation to improve dose conformality, takes longer to deliver the same radiation dose, thereby reducing its effectiveness. Biological effective dose (BED) is a metric that incorporates both dose and treatment time and has been shown to correlate with enhanced cell kill in Vitro, as well as normal tissue toxicity in animal models. METHODS A retrospective study of patients having single-session AVM SRS between 1990 and 2009 with a minimum of 2 yr follow-up. Excluded were patients having prior radiation or embolization, as well as patients having volume-staged SRS. BED was calculated using the mono-exponential model described by Jones and Hopewell. The primary outcomes of the study were time to obliteration and chance of excellent outcome (nidus obliteration with no new deficits). RESULTS Three hundred twenty-one patients (328 AVMs) met inclusion criteria (median follow-up, 6.7 yr). BED was associated with both decreased time to obliteration and excellent outcome in univariate Cox regression analyses, both when treated as a dichotomous (P = .002, HR = 1.51 for obliteration; P = .001, HR = 1.61 for outcome) or continuous variable (P = .049, HR = 1.002 for obliteration; P = .01, HR = 1.00 for outcome). In multivariable analyses including dichotomized BED and modified Radiosurgery-Based Arteriovenous Malformation Score as covariates, BED remained significantly associated with both time to obliteration (P = .01, HR = 1.46) and excellent outcome (P = .04, HR = 1.40). CONCLUSION BED was predictive of outcomes after AVM SRS. Further study is warranted to determine whether BED optimization should be considered as well as a prescribed treatment dose for SRS treatment planning.

Stereotactic Radiosurgery for Pediatric Brain Arteriovenous Malformations: Long-Term Outcomes

Abstract INTRODUCTION Contrary to the better described obliteration and hemorrhage data after stereotactic radiosurgery (SRS) treatment of brain arteriovenous malformations (AVMs) in pediatric patients, estimates of the rarer complications including cyst and tumor formation are limited in the literature. The aim of the study was to assess the long-term outcomes and risks of SRS for AVMs in pediatric (age &lt; 18 yr) patients. METHODS We retrospectively analyzed the International Radiosurgery Research Foundation pediatric AVM database from 1987 to 2018. AVM obliteration, post-SRS hemorrhage, cyst formation, and tumor formation were assessed. Cumulative probabilities, adjusted for competing risk of death, were calculated. RESULTS The study cohort comprised 539 pediatric AVM patients (mean follow-up: 85.8 mo). AVM obliteration was observed in 64.3% of patients, with cumulative probabilities of 63.6% (95% CI: 58.8%-68.0%), 77.1% (95% CI: 72.1%-81.3%), and 88.1% (95% CI: 82.5%-92.0%) over 5, 10, and 15 yr, respectively. Post-SRS hemorrhage was observed in 8.4% of patients, with cumulative probabilities of 4.9% (95% CI: 3.1%-7.2%), 9.7% (95% CI: 6.4%-13.7%), and 14.5% (95% CI: 9.5%-20.5%) over 5, 10, and 15 yr, respectively. Cyst formation was observed in 2.1% of patients, with cumulative probabilities of 5.5% (95% CI: 2.3%-10.7%) and 6.9% (95% CI: 3.1%-12.9%) over 10 and 15 yr, respectively. Meningioma was observed in 2 patients (0.4%) at 10 and 12 yr after SRS, with cumulative probability of 3.1% (95% CI: 0.6%-9.7%) over 15 yr. CONCLUSION AVM obliteration can be expected after SRS in the majority of the pediatric population, with a relatively low risk of hemorrhage during the latency period. Cyst and benign tumor formation after SRS can be observed in 7% and 3% of patients over 15 yr, respectively. Longitudinal surveillance for delayed neoplasia is prudent despite its low incidence.

Seizure Presentation in Patients With Brain Arteriovenous Malformations Treated With Stereotactic Radiosurgery: A Multicenter Study

Abstract INTRODUCTION Seizures are the second most common clinical presentation in patients with brain arteriovenous malformations (AVMs), and they are the most common presentation of unruptured AVMs. The aim of this multicenter, retrospective cohort study was to identify predictors of seizure presentation in AVM patients treated with stereotactic radiosurgery (SRS). METHODS We performed a retrospective review of AVM patients treated with SRS at 8 participating International Radiosurgery Research Foundation sites. Patient and AVM characteristics were compared between those with versus without a seizure presentation in univariable and multivariable models. Subgroup analysis of patients with cortical AVMs was performed. RESULTS The study cohort comprised 2333 AVM patients, including 419 (18%) with and 1914 (82%) without a seizure presentation. Prior AVM resection (OR = 7.65, P = .001), lack of prior AVM hemorrhage (OR = 0.004, P &lt; .001), cortical AVM location (OR = 1559.42, P &lt; .001), lower Spetzler-Martin (SM) grade (OR = 0.51, P = .007), and higher Virginia Radiosurgery AVM Score (VRAS; OR = 1.46, P = .008) were independent predictors of seizure presentation. The rate of seizure presentation in patients with cortical AVMs was 27%. Prior AVM resection (OR = 8.36, P &lt; .001), lack of prior AVM hemorrhage (OR = 0.004, P &lt; .001), and temporal AVM location (OR = 4.15, P &lt; .001) were independent predictors of seizure presentation for cortical AVMs. CONCLUSION We identified multiple factors associated with seizure presentation in AVM patients selected to undergo SRS. Prior AVM resection, cortical AVM location, and lack of prior AVM hemorrhage were the strongest predictors of pre-SRS seizures. SM grade and VRAS may have a role in seizure risk stratification. Among cortical AVMs, temporal lobe localization was predictive of seizure presentation.

Left Transsylvian-Transinsular Approach for Radiation-Induced Cavernous Malformation: 3-Dimensional Operative Video.

De novo cavernous malformation (CM) formation after radiation therapy for brain tumors is well known, but CM formation adjacent to a radiosurgically treated arteriovenous malformation (AVM) is rare.1 This video demonstrates the microsurgical resection of a de novo CM adjacent to a previously treated high-grade AVM and clipping of a middle cerebral artery (MCA) aneurysm. A 70-yr-old male with history of radiosurgery for AVM presented with aphasia and confusion. Preoperative angiography showed complete occlusion of the AVM. MRI showed multiple cystic lesions suspicious for radiation-induced necrosis and CM. IRB approval and patient consent was obtained. A pterional craniotomy was performed with transsylvian exposure of the insula. The radiated feeding arteries were followed to the occluded AVM nidus. A CM was noted deep to this candelabra of the MCA vessels, which were mobilized to access and resect the CM. A small incision was made in this insular cortex underneath the malformation circumferentially freeing it of adhesions. The sclerotic AVM nidus was circumferentially dissected and removed en bloc. Thorough exploration of the resection cavity revealed no residual CM or AVM nidus. Attention was then turned to the M2-MCA bifurcation aneurysm, which was occluded with a straight clip. Postoperative imaging confirmed complete CM resection. The patient recovered from his aphasia. This case demonstrates the management of a radiation-induced de novo CM following treatment of a high-grade AVM. Radiographic follow-up for radiosurgically treated AVM is needed to rule out long-term complications. Bleeding from a de novo CM mimics bleeding from residual AVM nidus, requiring careful angiographic evaluation.

Correlation of Appearance of MRI Perinidal T2 Hyperintensity Signal and Eventual Nidus Obliteration Following Photon Radiosurgery of Brain AVMs: Combined Results of LINAC and Gamma Knife Centers

A wide variety of radiologic changes occur within and adjacent to the nidus of arteriovenous malformations (AVMs) after stereotactic radiosurgery (SRS). Our objective was to study the magnetic resonance imaging(MRI)-defined changes following photon radiosurgery of AVMs and specifically to correlate the appearance of a perinidal T2 hyperintensity signal with the eventual angiographic obliteration of an AVM nidus in response to SRS treatment. This retrospective study was conducted on 62 patients with brain AVMs who received photon SRS treatments between 2004 and 2017, using either a technique based on a linear accelerator at the Alexandria LINAC Radiosurgery Center in Egypt (21 patients/AVMs) or a technique based on a gamma unit at the Koto Memorial Gamma Knife Center in Japan (41 patients/AVMs). All patients included in the study had serial clinical and radiologic follow-ups for ≥ 2 years after SRS treatments. In the combined study series of 62 patients/AVMs treated with photon SRS, the follow-up MRIs revealed that 50 AVMs (80.6%) showed nonvisualized nidus and 12 AVMs (19.4%) showed decreased nidus size. Radiation-induced changes, defined as appearance of perinidal T2 hyperintensities in post-SRS MRIs, occurred in 34 patients (54.8%). Of the 35 patients with available follow-up angiographic studies, 30 AVMs (85.7%) demonstrated complete nidus obliteration at a mean of 36 months (range: 8-66 months) after SRS. Of the 30 AVMs with both MRI evidence of a nonvisualized nidus and angiographic verification of complete nidus obliteration, 20 AVMs (66.7%) were associated with prior MRI evidence of the appearance of a perinidal T2 hyperintensity signal at an average of 12 months (range: 6-45 months) after SRS. Of the five AVMs with both MRI evidence of decreased nidus size and angiographic verification of partial nidus obliteration, four AVMs (80%) showed perinidal T2 hyperintensity signal on post-SRS follow-up MRIs. Lower Spetzler-Martin grade (p = 0.013), smaller AVM volume (p = 0.017), and appearance of post-SRS perinidal T2 hyperintensity signal (p = 0.007) were the statistically significant independent predictors of AVM obliteration. The appearance of perinidal T2 hyperintensity signal in the post-SRS MRIs had a sensitivity of 66.7%, a specificity of 20%, and an overall accuracy of 60% in predicting the eventual obliteration of the AVM nidus. The present study may help improve our current understanding of the mechanisms behind the radiation-induced tissue changes following AVM SRS. Because the SRS-induced hemodynamic changes within the AVM nidus initiate the cascade of the subsequent formation of perinidal vasogenic brain edema, the appearance of perinidal high T2 signal in the follow-up MRIs after SRS would be a valuable indicator of the AVM response to SRS. The development of perinidal hyperintensity was the strongest predictive factor of AVM obliteration (p = 0.007), with relatively high sensitivity (66.7%) and accuracy (60%) and fairly low specificity (20%), as a prognostic sign of eventual complete angiographic obliteration of the AVM nidus following SRS.

Seizure Presentation in Patients with Brain Arteriovenous Malformations Treated with Stereotactic Radiosurgery: A Multicenter Study

Seizures are the second most common clinical presentation in patients with brain arteriovenous malformations (AVMs) and the most common presentation of unruptured AVMs. The aim of the present multicenter, retrospective cohort study was to identify the predictors of seizure presentation in patients with AVM who had undergone stereotactic radiosurgery (SRS). We performed a retrospective review of patients with AVM who had been treated with SRS at 8 participating International Radiosurgery Research Foundation sites. The patient and AVM characteristics were compared between those with and without seizure presentation in univariable and multivariable models. A subgroup analysis of patients with cortical AVMs was performed. The study cohort included 2333 patients with AVM, including 419 (18%) with and 1914 (82%) without a seizure presentation. Previous AVM resection (odds ratio [OR], 7.65; P= 0.001), a lack of previous AVM hemorrhage (OR, 0.004; P < 0.001), a cortical AVM location (OR, 1559.42; P < 0.001), a lower Spetzler-Martin grade (OR, 0.51; P= 0.007), and a higher Virginia radiosurgery AVM score (OR, 1.46; P= 0.008) were independent predictors of seizure presentation. The rate of seizure presentation in patients with cortical AVMs was 27%. Previous AVM resection (OR, 8.36; P < 0.001), a lack of previous AVM hemorrhage (OR, 0.004; P < 0.001), and temporal AVM location (OR, 4.15; P<0.001) were independent predictors of seizure presentation for cortical AVMs. We identified multiple factors associated with seizure presentation in patients with AVM to undergo SRS. Previous AVM resection, a cortical AVM location, and a lack of previous AVM hemorrhage were the strongest predictors of pre-SRS seizures. The Spetzler-Martin grade and Virginia radiosurgery AVM score might have a role in seizure risk stratification. For cortical AVMs, a temporal lobe location was predictive of seizure presentation.

Multimodality Imaging for Radiosurgical Management of Arteriovenous Malformations

Background: Cerebral arteriovenous malformations (AVMs) are rarely seen congenital vascular anomalies. AVMs may lead to intracranial hemorrages due to disorganized tangle of vessels. Lifetime risk of bleeding from AVMs may be significant given the diagnosis at typically earlier ages of the lifespan, and complications associated with hemorrhage may lead to substantial morbidity or mortality. Management of AVMs aims at eliminating or reducing the risk of subsequent bleeding. In this context, microvascular surgical resection, endovascular embolization and radiosurgical treatment may be used for management of AVMs.Objective: In this study, we assessed the incorporation of Magnetic Resonance Imaging (MRI) in treatment planning for AVM radiosurgery. Methods: We identified 25 patients receiving radiosurgery for AVMs at our institution. Radiosurgery target volumes generated by using CT-only based imaging and CT-MR fusion based imaging for each patient were evaluated.Results: Twenty five patients undergoing SRS for AVMs were evaluated for target volume determination in this study. Mean target volume was 4.9 cc (range: 1.3-15.9 cc) on CT-only imaging, 5.7 cc (range: 1.4-16.7 cc) on CT-MR fusion based imaging, and 5.9 cc (range: 1.4-16.9 cc) on consensus decision of all treating physicians with colleague peer review. Target definition based on CT-MR fusion based imaging was identical to the consensus decision of all treating physicians in majority of patients.Conclusions: Treatment planning for AVM radiosurgery may be improved by incorporating CT-MR fusion based imaging, which clearly should be supplemented with additional data from angiography. There is need for additional studies to establish a consensus on optimal target definition by multimodality imaging for SRS of AVMs.

Abstract 65: Risk of Intracerebral Hemorrhage Associated With Pregnancy in Women With Cerebral Arteriovenous Malformations: A Large-Scale Controlled Cohort Study

Introduction: Prior single-center reports have suggested an increased incidence of intracerebral hemorrhage (ICH) from cerebral arteriovenous malformation (AVM) rupture during pregnancy. Unfortunately, data on this topic are limited due to small sample size as well as the aggregation of all patients with AVMs, failing to account for the well-described variability in ICH risk based on AVM size, location and morphology. Methods: Using administrative data on all discharges from hospitals in New York (2005-2014) and Florida (2005-2015), we identified patients with first time pregnancy and delivery. The primary endpoint was first time ICH. We used a case-crossover design in which each woman and her unique AVM served as her own control, by matching the pregnancy period with an equal duration of time 1 year prior. Women were excluded for any treatment (embolization, surgery or radiosurgery) for AVM or first time ICH prior to the control period. Results are presented as OR [95% CI] or median [IQR]. Results: Among 6,273,562 women with first time pregnancy, median age was 28 [23 – 33], 49% were white, 19% were black, and 19% were Hispanic. Of these patients, 1,024 (0.02%) had an AVM and 79 were excluded for ICH or treatment prior to the control period. Women with AVMs were more likely to undergo Caesarian section than those without (58% vs. 36%, p&lt;0.001). There were no major differences in vascular risk factors between the women without an AVM versus those with AVM. In unmatched analysis, the incidence of first time ICH in women with AVMs was greater than those without in the control (0.8% vs. 0.001%, p&lt;0.0001), pregnancy/delivery (5.1% vs. 0.01%, p&lt;0.0001), and 12-week post-partum (1.2% vs 0.01%, p&lt;0.0001) periods. In matched case-crossover analysis in women with AVMs, pregnancy was associated with an increased risk (OR 3.4 [1.4 – 8.6]) relative to the control non-pregnant period. Conclusion: In this large-scale cohort study in which women with AVMs served as their own controls, we account for the variability in ICH risk based on AVM morphology and identify a nearly 350% increased risk of ICH associated with first time pregnancy and delivery. These findings support the need for further work on mechanistic underpinnings as well as a major need for improved methods to abrogate ICH risk.

Intervening Nidal Brain Parenchyma and Risk of Radiation-Induced Changes After Radiosurgery for Brain Arteriovenous Malformation: A Study Using an Unsupervised Machine Learning Algorithm

To assess the sensitivity and specificity of arteriovenous malformation (AVM) nidal component identification and quantification using an unsupervised machine learning algorithm and to evaluate the association between intervening nidal brain parenchyma and radiation-induced changes (RICs) after stereotactic radiosurgery. Fully automated segmentation via unsupervised classification with fuzzy c-means clustering was used to analyze the AVM nidus on T2-weighted magnetic resonance imaging studies. The proportions of vasculature, brain parenchyma, and cerebrospinal fluid were quantified. These were compared with the results from manual segmentation. The association between the brain parenchyma component and RIC development was assessed. The proposed algorithm was applied to 39 unruptured AVMs in 39 patients (17 female and 22 male patients), with a median age of 27 years. The median proportion of the constituents was as follows: vasculature, 31.3%; brain parenchyma, 48.4%; and cerebrospinal fluid, 16.8%. RICs were identified in 17 of the 39 patients (43.6%). Compared with manual segmentation, the automated algorithm was able to achieve a Dice similarity index of 79.5% (sensitivity, 73.5%; specificity, 85.5%). RICs were associated with a greater proportion of intervening nidal brain parenchyma (52.0% vs. 45.3%; P= 0.015). Obliteration was not associated with greater proportions of nidal vasculature (36.0% vs. 31.2%; P= 0.152). The automated segmentation algorithm was able to achieve classification of the AVM nidus components with relative accuracy. Greater proportions of intervening nidal brain parenchyma were associated with RICs.

Stereotactic radiosurgery and fractionated radiotherapy for spinal arteriovenous malformations – A systematic review of the literature

Spinal arteriovenous malformations (AVMs) comprise a group of complex vascular lesions whose treatment with microsurgery or transarterial embolization can be challenging. Stereotactic radiosurgery is a well-established treatment for intracranial AVMs, and spinal radiosurgery and fractionated radiotherapy are common treatments for spinal tumors of both primary and metastatic origin. The use of radiosurgery and fractionated radiotherapy for the treatment of spinal arteriovenous malformations, however, has been infrequently reported. Spinal stereotactic radiosurgery is emerging as a promising option for the treatment of these lesions. We conducted a systematic review of English language articles reporting one or more cases of spinal radiosurgery or fractionated radiotherapy for the treatment of spinal arteriovenous fistulas (AVFs) or arteriovenous malformations. Eight unique studies comprising 64 patients were identified. All treated lesions consisted primarily of spinal AVMs, either intramedullary or metameric. Most were treated with CyberKnife technology. Marginal doses in the most current studies ranged from 18 to 21 Gy given over 2–4 fractions. In aggregate, good outcomes were reported in 92.2% with no instances of post-treatment hemorrhage over a mean follow-up time of 46.8 months. Angiographic follow-up showed the nidus to be obliterated in 16%, decreased in 44.6%, and unchanged in 39.3%. Stereotactic radiosurgery for spinal arteriovenous malformations holds promise as a safe and potentially effective option in the treatment of these rare but complex lesions.

Re-Evaluating Clinical Outcomes for AVM Stereotactic Radiosurgery.

Traditional outcome measures after stereotactic radiosurgery (SRS) for cerebral arteriovenous malformations (AVMs) have focused predominantly on angiographic obliteration and general neurologic complications. Several grading scales attempting to predict the outcome for specific patients have previously been proposed and validated, and are outlined here. These have largely been based on both AVM and patient characteristics and attempt to predict obliteration. However, the most practical and clinically oriented goal in the management of AVMs is the prospective avoidance of neurological sequelae manifesting in the form of stroke or death, regardless of AVM obliteration. Long-term outcomes following SRS have demonstrated stroke or death rates of 1.5-2.0% per year for the first 5 years after SRS, followed by 0.2-0.4% annual risk thereafter. This focus on the avoidance of stroke or death is additionally crucial for direct comparisons to non-interventional natural history data. Here, we discuss the history of outcomes data on radiosurgery for AVMs and propose a re-evaluation of clinical outcome that is of most utility to the patient.

Gamma Knife Radiosurgery of Arteriovenous Malformations: Long-Term Outcomes and Late Effects.

Gamma Knife radiosurgery (GKRS) of cerebral arteriovenous malformations (AVM) is an accepted treatment option that has been performed for more than 40 years. The goal of AVM GKRS is nidus obliteration to eliminate the risk of intracranial hemorrhage while minimizing the risk of short- and long-term adverse radiation effects (ARE). Nidus obliteration typically occurs between 1 and 5 years after GKRS. The most important factor associated with nidus obliteration is the prescribed radiation dose. The chance of obliteration ranges from 60 to 70% for margin doses of 15-16 Gy to 90% or more for margin doses of 20-25 Gy. Neurologic decline after GKRS can occur from either hemorrhage or ARE. Numerous studies have shown that the risk of AVM bleeding is either unchanged or decreased following GKRS. Advances in neuroimaging and dose-planning software have reduced the incidence of early ARE to <4%. Volume-staged procedures can be safely performed for large-volume AVM that were previously considered too large for GKRS. Late ARE (generally cyst formation) are common in patients who develop early MRI imaging changes (areas of high T2 signal) after GKRS, but most cases can be managed with either observation or resection of the thrombosed AVM.

Arteriovenous Malformation (AVM) Treated with Robotic Radiosurgery: Impact of Beam Reduction in 12 Gy Normal Brain Volume and It’s Clinical Implication

Purpose: Dosimetric study to evaluate impact of “beam” reduction in AVM radiosurgery on normal brain dose parameters and it’s clinical implications. Materials and Methods: Five small volume AVMs (nidus volume 0.31 - 1.94 cc) planned for single fraction SRS with robotic radiosurgery system. Planning scans done with CT scan brain, CT & MR angiography, then nidus volume and organ at risk (OARs) were contoured. Planning was done with multiplan planning system. Plan evaluated as per Flickenger model parameters of 12 Gy nomal brain vol & marginal dose. 7.5 mm and 10 mm cons used, optimization done with seqential algorithm. 20 Gy was prescribed to isodose with appropriate nidus coverage (>98%). Total beams of five plans were 85 - 250, monitor unit 17,259 - 24,602 MU. 12 Gy normal brain volume is 0.9 - 7.6 cc. Then beam reduction is done by reducing beams with minimum MU in steps of 50, 100, 150, 200, 250 MU and after beam reduction, re-optimization done. Prescription isodose was changed to keep the nidus coverage > 98%. Impacts of beam reduction on 12 Gy normal brain vol and conformity/homogeniety index were analyzed. Results: Optimal plans of five patients with 20 Gy prescribed to 88% - 90% isodose, nidus coverage more than 98%. In dosimetric parameters, mean CI was 1.36 - 1.51, nCI 1.41 - 1.51, HI 1.1 - 1.4 and mean 12 Gy normal brain volume 0.17, 1.44, 5.3, 5.5 and 7.6cc respectively. After beam reduction of less than 50 MU contribution (in case#1), prescibing at suitable isodose (85%) beam reduces to 79 and 12 Gy volume marginally increases to 26.4 cc. Beam reduction of less than 100 MU reduces to 53 - 92 beamlets. Reduction of beams with less than 150 MU contribution did not significantly change the 12Gy normal brain volume. However, reduction of beamlets with more than 200 MU, 250 MU, 300 MU, 450 MU and 550 MU significantly affects the 12 Gy normal brain volume. Prescription-isodose modified from 83% to 50% to have >98% coverage. CI and HI increased from 1.36 - 1.51 to 2.51 - 2.63 and 1.1 - 1.4 to 1.52 - 1.54 respectively. There was exponential increase in 12 Gy volume with reduction of beams with higher proportion in larger nidus. Conclusions: In robotic radiosurgery system, beam reduction even after re-optimization impairs the conformity index and increase 12 Gy normal brain volume, hence long-term toxicity. Optimal beam numbers are required for optimal plan generation.

Coil-Protected Technique for Liquid Embolization in Neurovascular Malformations.

ObjectiveTo evaluate the safety and efficacy of the coil-protected technique for liquid embolization in neurovascular malformations.Materials and MethodsTwenty-two patients who underwent coil-protected liquid embolization for symptomatic cranial (n = 13) and spinal (n = 9) arteriovenous fistula (AVF) or arteriovenous malformations (AVMs) were identified. A total of 36 target feeder vessels were embolized with N-butyl cyanoacrylate and/or Onyx (Medtronic). This technique was used to promote delivery of a sufficient amount of liquid embolic agent into the target shunt or nidus in cases where tortuous feeding arteries preclude a microcatheter wedging techniqu and/or to prevent reflux of the liquid embolic agent in cases with a short safety margin. The procedure was considered technically successful if the target lesion was sufficiently filled with liquid embolic agent without unintentional reflux. Angiographic and clinical outcomes were retrospectively evaluated.ResultsTechnical success was achieved for all 36 target feeders. Post-embolization angiographies revealed complete occlusion in 16 patients and near-complete and partial occlusion in three patients each. There were no treatment-related complications. Of the six patients who showed near-complete or partial occlusion, five received additional treatments: two received stereotactic radiosurgery for cerebral AVM, two underwent surgical removal of cerebral AVM, and one underwent additional embolization by direct puncture for a mandibular AVM. Finally, all patients showed complete (n = 19) or near-complete (n = 3) occlusion of the target AVF or AVM on follow-up angiographies. The presenting neurological symptoms improved completely in 15 patients (68.2%) and partially in seven patients (31.8%).ConclusionThe coil-protected technique is a safe and effective method for liquid embolization, especially in patients with various neurovascular shunts or malformations who could not be successfully treated with conventional techniques.

When hoofbeats are zebras: Late onset niemann-pick disease type C overlapping with frontotemporal dementia

Stereotactic radiosurgery is widely used to treat brain arteriovenous malformation; however, detailed information on late radiation-induced complications (LRICs) is scarce. The goal of the present study was to characterize the incidence, risk factors, and clinical outcomes of LRICs based on our long-term follow-up data.The outcomes of consecutive patients who underwent stereotactic radiosurgery for arteriovenous malformations at our institution in 1990–2010 were analyzed. Cyst formation/encapsulated hematoma (CF/EH) and radiation-induced tumor were defined as LRICs. Cumulative incidence rates were calculated using the Kaplan-Meier method. Risk factors for CF/EH were analyzed using a Cox proportional hazard model.A total of 581 patients with mean and median follow-up periods of 11.8 and 10.1 years, respectively (range, 2.0–26.7 years), were analyzed. CF/EH was observed in 30 patients (5.2%). The median time to progression was 11.8 years (range, 1.9–23.9 years). Cumulative incidence rates were 0.8%, 2.8%, 7.6%, and 9.7% at 5, 10, 15, and 20 years, respectively. A multivariate analysis showed that lobar location and maximal diameter ≥22 mm were significant risk factors for CF/EH. Overall, the functional outcomes were mild, moderate, and severe/fatal in 26 (87%), 1 (3%), and 3 (10%) patients, respectively. Radiation-induced tumor was confirmed in only 1 patient (0.17%).An increased nidus size and lobar location are risk factors for CF/EH. Although the CF/EH incidence is low, some LRICs develop after long periods. Extended follow-up is warranted, particularly of patients with risk factors.

Integration of rotational angiography enables better dose planning in Gamma Knife radiosurgery for brain arteriovenous malformations.

OBJECTIVEIn Gamma Knife radiosurgery (GKS) for arteriovenous malformations (AVMs), CT angiography (CTA), MRI, and digital subtraction angiography (DSA) are generally used to define the nidus. Although the AVM angioarchitecture can be visualized with superior resolution using rotational angiography (RA), the efficacy of integrating RA into the GKS treatment planning process has not been elucidated.METHODSUsing data collected from 25 consecutive patients with AVMs who were treated with GKS at the authors' institution, two neurosurgeons independently created treatment plans for each patient before and after RA integration. For all patients, MR angiography, contrasted T1 imaging, CTA, DSA, and RA were performed before treatment. The prescription isodose volume before (PIVB) and after (PIVA) RA integration was measured. For reference purposes, a reference target volume (RTV) for each nidus was determined by two other physicians independent of the planning surgeons, and the RTV covered by the PIV (RTVPIV) was established. The undertreated volume ratio (UVR), overtreated volume ratio (OVR), and Paddick's conformal index (CI), which were calculated as RTVPIV/RTV, RTVPIV/PIV, and (RTVPIV)2/(RTV × PIV), respectively, were measured by each neurosurgeon before and after RA integration, and the surgeons' values at each point were averaged. Wilcoxon signed-rank tests were used to compare the values obtained before and after RA integration. The percentage change from before to after RA integration was calculated for the average UVR (%ΔUVRave), OVR (%ΔOVRave), and CI (%ΔCIave) in each patient, as ([value after RA integration]/[value before RA integration] - 1) × 100. The relationships between prior histories and these percentage change values were examined using Wilcoxon signed-rank tests.RESULTSThe average values obtained by the two surgeons for the median UVR, OVR, and CI were 0.854, 0.445, and 0.367 before RA integration and 0.882, 0.478, and 0.463 after RA integration, respectively. All variables significantly improved after compared with before RA integration (UVR, p = 0.009; OVR, p < 0.001; CI, p < 0.001). Prior hemorrhage was significantly associated with larger %ΔOVRave (median 20.8% vs 7.2%; p = 0.023) and %ΔCIave (median 33.9% vs 13.8%; p = 0.014), but not %ΔUVRave (median 4.7% vs 4.0%; p = 0.449).CONCLUSIONSIntegrating RA into GKS treatment planning may permit better dose planning owing to clearer visualization of the nidus and, as such, may reduce undertreatment and waste irradiation. Further studies examining whether the observed RA-related improvement in dose planning also improves the radiosurgical outcome are needed.