Nidus Volume Research Articles

Outcome Evaluation of Repeat Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations.

Repeat stereotactic radiosurgery (SRS) for persistent cerebral arteriovenous malformation (AVM) has generally favorable patient outcomes. However, reporting studies are limited by small patient numbers and single-institution biases. The purpose of this study was to provide the combined experience of multiple centers, in an effort to fully define the role of repeat SRS for patients with arteriovenous malformation. This multicenter, retrospective cohort study included patients treated with repeat, single-fraction SRS between 1987 and 2022. Follow-up began at repeat SRS. The primary outcome was a favorable patient outcome, defined as a composite of nidus obliteration in the absence of hemorrhage or radiation-induced neurological deterioration. Secondary outcomes were obliteration, hemorrhage risk, and symptomatic radiation-induced changes. Competing risk analysis was performed to compute yearly rates and identify predictors for each outcome. The cohort comprised 505 patients (254 [50.3%] males; median [interquartile range] age, 34 [15] years) from 14 centers. The median clinical and magnetic resonance imaging follow-up was 52 (interquartile range, 61) and 47 (interquartile range, 52) months, respectively. At last follow-up, favorable outcome was achieved by 268 (53.1%) patients (5-year probability, 50% [95% CI, 45%-55%]) and obliteration by 300 (59.4%) patients (5-year probability, 56% [95% CI, 51%-61%]). Twenty-eight patients (5.6%) experienced post-SRS hemorrhage with an annual incidence rate of 1.38 per 100 patient-years. Symptomatic radiation-induced changes were evident in 28 (5.6%) patients, with most occurring in the first 3 years. Larger nidus volumes (between 2 and 4 cm3, subdistribution hazard, 0.61 [95% CI, 0.44-0.86]; P=0.005; >4 cm3, subdistribution hazard, 0.47 [95% CI, 0.32-0.7]; P<0.001) and brainstem/basal ganglia involvement (subdistribution hazard, 0.6 [95% CI, 0.45-0.81]; P<0.001) were associated with reduced probability of favorable outcome. Repeat SRS confers reasonable obliteration rates with a low complication risk. With most complications occurring in the first 3 years, extending the latency period to 5 years generally increases the rate of favorable patient outcomes and reduces the necessity of a third intervention.

CyberKnife Radiosurgery for Spinal Intramedullary Arteriovenous Malformations: A Single-Center Experience

Intramedullary spinal arteriovenous malformation (ISAVM, glomus type) is a type of spinal cord arteriovenous malformation, which is a rare disease known often to have a complex vascular supply interfering with that of the spinal cord, and is in complex anatomical relations with cord structures and nerve roots. Though microsurgical and endovascular treatment has mainly been the standard options, in high-risk cases with these treatments, stereotactic radiotherapy (SRT) might be the option of choice. We retrospectively reviewed 10 consecutive patients with ISAVM who received SRT using CyberKnife at the Japanese Red Cross Medical Center (Tokyo, Japan) from January 2011 to March2022. No case in this series suffered from hemorrhage after applying SRT. One case experienced neurological impairment 10years after SRT, which we attributed to venous congestion due to the remaining lesion. No case of radiation myelopathy was observed in this series. In one case, the nidus volume reduction and loss of flow voids were obvious, though improvement in the neurological outcome was not apparent. No radiological changes were observed in the other 9 patients. Even in lesions without radiological changes, no hemorrhagic events were observed for an average period of 4years. SRT may be a feasible option in treating ISAVM, especially for lesions in which microsurgical resection and endovascular treatment are inapplicable. To ascertain the safety and efficacy of this approach, further studies with more patients and longer follow-up is required.

Gamma Knife Radiosurgery in Partially Embolised Arteriovenous Malformations: Management Dilemmas and Outcomes.

The role of Gamma Knife radiosurgery (GKRS) in partially embolized arteriovenous malformations (AVMs) has always remained a subject of debate. The aim of this study was to evaluate the efficacy of GKRS in partially embolized AVMs and to analyze factor that influence its obliteration. This was a retrospective study from a single institute performed over a period of 12 years (2005-2017). It included all patients who underwent GKRS for partially embolized AVMs. Demographic characteristics, treatment profiles, and clinical and radiological data were obtained during treatment and follow-up. Obliteration rates and factors affecting the same were sought and analyzed. A total of 46 patients with a mean age of 30 years (range: 9-60 years) were included in the study. Follow-up imaging was available for 35 patients either by digital subtraction angiography (DSA) or magnetic resonance imaging (MRI). We found complete AVM obliteration in 21 patients (60%): one had near total obliteration (>90% obliteration), 12 had subtotal obliteration (<90%), and one had no change in the volume following GKRS. Following embolization alone, an average of 67% of the AVM volume was obliterated which resulted in an average 79% final obliteration rate after Gamma Knife radiosurgery. Mean duration to complete obliteration was found to be 3.45 years (range: 1-10 years). There was a significant difference (P = 0.04) in the mean interval between embolization and GKRS among cases with complete obliteration (12 months) and those with incomplete obliteration (36 months). There was no significant difference (P = 0.49) in the average obliteration rate between the ARUBA-eligible unruptured AVMs (79.22%) and ruptured AVMs (79.04%). Bleeding after GKRS during the latency period had a negative impact on obliteration (P = 0.05). Other factors like age, sex, Spetzler-Martin (SM)-grade, Pollock Flickinger score (PF-score), nidus volume, radiation dose, or presentation before embolization had no significant influence on obliteration. Three patients had permanent neurological deficits after embolization and none after radiosurgery. Six out of nine patients (66%) presenting with seizures were seizure-free after the treatment. Hemorrhage was noted in three patients following combined treatment and were managed non-surgically. Obliteration rates in partially embolized AVM after Gamma Knife are inferior when compared to Gamma Knife alone; moreover with volume staging and/or dose staging being increasingly plausible due to the new ICON machine, embolization may be completely replaced. However we have shown that in complicated and carefully chosen AVMs, embolization followed by GKRS is a valid modality of management. This study represents a real-world picture of individualized AVM treatment depending on patient choices and resources available.

In‐Room Direct Nidal Flow Measurement by Digital Subtraction Angiography to Estimate Hemorrhage Risk in Brain Arteriovenous Malformations: A Pilot Study

Background Noninvasive direct flow measurement from digital subtraction angiography (DSA) is challenging in brain arteriovenous malformations (BAVMs). We devised a method to estimate the blood volume flow rate of BAVM nidus using DSA, and assessed its association with angioarchitecture features in hemorrhagic presentation. Methods A total of 24 patients with BAVMs (10 controls and 14 with hemorrhage) who underwent DSA and magnetic resonance (MR) were retrospectively recruited. Fifteen patients underwent additional phase contrast MR imaging. The nidus volume was contoured on the MR time‐of‐flight data set. From DSA, flow velocities and volume flow rate were estimated along calibrated vascular center lines. The BAVM nidus volume flow rate was computed by adding feeding volume flow rate of arteries confirmed on DSA and then normalizing them with nidus volume to yield the nidus flow index. The correspondent phase‐contrast MR‐estimated nidus flow index was evaluated in each BAVM for comparison. Comparisons of hemodynamic parameters of the control and hemorrhage groups were conducted using the Wilcoxon rank sum test. A support vector machine was used for classifying BAVM patients using angioarchitectures and the nidus flow index. Results For the DSA results, the nidus flow index was higher in the hemorrhagic group than in the control group ( P =0.0272). The flow index determined using phase‐contrast MR and nidus volume were not significant. The classification accuracy was higher when the DSA nidus flow index was added into angioarchitecture. Conclusion The BAVM nidus flow index can be directly estimated from DSA and may be associated with hemorrhagic BAVM. Peritherapeutic hemodynamic assessment of BAVMs inside the angio‐suite is feasible.

Susceptibility weighted imaging for qualitative grading of persistent arteriovenous shunting in deep-seated arteriovenous malformations after stereotactic radiation surgery.

To investigate Susceptibility Weighted Imaging (SWI) signal changes in the draining vein of deep-seated arterio-venous malformations (AVMs) following stereotactic radiosurgery (SRS). This is a retrospective study of 32 patients with deep-seated AVMs who were treated with SRS. Pre-SRS treatment and post-SRS treatment MRI were performed at 6, 12, and 24-month intervals. Deep-seated AVMs were classified based on their anatomical location and venous drainage pattern. AVM nidal volume (cm3) was estimated using the ABC/2 method. AV shunting of the AVM draining veins were graded according to its SWI signal intensity: hyperintense (grade III), mixed signal intensity (grade II), hypointense (grade I) and absent (grade 0). Conventional time-of-flight (TOF)-MRA and contrast enhanced (CE)-MRA sequences were performed to document the patency of the vein. Pre-SRS treatment AVM draining veins were either grade III 18/32 (56%) or grade II 14/32 (44%). Using mixed effects analysis, we demonstrate that each month following the SRS treatment nidal volumes decreased at the rate of 0.51cm3/per month (CI -0.61 to (-0.40)) p =.00. Following the treatment, there was a clinically significant relationship between the signal and nidal volume: signal 0 corresponded with average nidal volume of 1.81cm3 (CI 1.40-2.21), signal 1 with nidal volume of 2.06cm3 (CI 1.69-2.44), signal 2 with nidal volume 2.73cm3 (CI 2.35-3.11) and signal 3 with nidal volume 3.13cm3 (CI 2.70-3.56) p = .00. Post-SRS AVM draining veins shows a stepwise regression of the SWI signal grades which can be reliably used as a surrogate to monitor the reduction of AV shunting.

Preoperative flow analysis of arteriovenous malformations and obliteration response after stereotactic radiosurgery.

Morphological and angioarchitectural features of cerebral arteriovenous malformations (AVMs) have been widely described and associated with outcomes; however, few studies have conducted a quantitative analysis of AVM flow. The authors examined brain AVM flow and transit time on angiograms using direct visual analysis and a computer-based method and correlated these factors with the obliteration response after Gamma Knife radiosurgery. A retrospective analysis was conducted at a single institution using a prospective registry of patients managed from January 2013 to December 2019: 71 patients were analyzed using a visual method of flow determination and 38 were analyzed using a computer-based method. After comparison and validation of the two methods, obliteration response was correlated to flow analysis, demographic, angioarchitectural, and dosimetric data. The mean AVM volume was 3.84 cm3 (range 0.64-19.8 cm3), 32 AVMs (45%) were in critical functional locations, and the mean margin radiosurgical dose was 18.8 Gy (range 16-22 Gy). Twenty-seven AVMs (38%) were classified as high flow, 37 (52%) as moderate flow, and 7 (10%) as low flow. Complete obliteration was achieved in 44 patients (62%) at the time of the study; the mean time to obliteration was 28 months for low-flow, 34 months for moderate-flow, and 47 months for high-flow AVMs. Univariate and multivariate analyses of factors predicting obliteration included AVM nidus volume, age, and flow. Adverse radiation effects were identified in 5 patients (7%), and 67 patients (94%) remained free of any functional deterioration during follow-up. AVM flow analysis and categorization in terms of transit time are useful predictors of the probability of and the time to obliteration. The authors believe that a more quantitative understanding of flow can help to guide stereotactic radiosurgery treatment and set accurate outcome expectations.

300 Stereotactic Radiosurgery With Versus Without Embolization for Brain Arteriovenous Malformations

INTRODUCTION: Prior comparisons of brain arteriovenous malformations (AVMs) treated using stereotactic radiosurgery (SRS) with or without embolization were inherently flawed, due to differences in the pre-treatment nidus volumes. METHODS: We retrospectively reviewed International Radiosurgery Research Foundation AVM databases from 1987–2018. Patients were categorized into the embolization and SRS (E+SRS) or SRS alone (SRS-only) cohorts. The two cohorts were matched in a 1:1 ratio using propensity scores. Primary outcome was defined as AVM obliteration. Secondary outcomes were post-SRS hemorrhage, all-cause mortality, radiologic and symptomatic radiation-induced changes (RIC), and cyst formation. RESULTS: The matched cohorts each comprised 101 patients. Crude AVM obliteration rates were similar between the matched E+SRS versus SRS-only cohorts (48.5% vs. 54.5%; OR = 0.788, p = 0.399). Cumulative probabilities of obliteration at 3, 4, 5, and 6 years were also similar between the E+SRS (33.0%, 46.4%, 56.2%, and 60.8%, respectively) and SRS-only (32.9%, 46.2%, 56.0%, and 60.6%, respectively) cohorts (SHR = 1.005, p = 0.981). Cumulative probabilities of radiologic RIC at 3, 4, 5, and 6 years were lower in the E+SRS (25.0%, 25.7%, 26.7%, and 26.7%, respectively) versus SRS-only (45.3%, 46.2%, 47.8%, and 47.8%, respectively) cohort (SHR = 0.478, p = 0.004). Symptomatic and asymptomatic embolization-related complication rates were 8.3% and 18.6%, respectively. Rates of post-SRS hemorrhage, all-cause mortality, symptomatic RIC, and cyst formation were similar between the matched cohorts. CONCLUSION: This study refutes the prevalent notion that AVM embolization negatively affects the likelihood of obliteration after SRS.

Adverse radiation effects in volume-staged radiosurgery for large arteriovenous malformations: a multiinstitutional study.

The optimal treatment paradigm for large arteriovenous malformations (AVMs) is controversial. One approach is volume-staged stereotactic radiosurgery (VS-SRS). The authors previously reported efficacy of VS-SRS for large AVMs in a multiinstitutional cohort; here they focus on risk of symptomatic adverse radiation effects (AREs). This is a multicentered retrospective review of patients treated with a planned prospective volume staging approach to stereotactically treat the entire nidus of an AVM, with volume stages separated by intervals of 3-6 months. A total of 9 radiosurgical centers treated 257 patients with VS-SRS between 1991 and 2016. The authors evaluated permanent, transient, and total ARE events that were symptomatic. Patients received 2-4 total volume stages. The median age was 33 years at the time of the first SRS volume stage, and the median follow-up was 5.7 years after VS-SRS. The median total AVM nidus volume was 23.25 cm3 (range 7.7-94.4 cm3), with a median margin dose per stage of 17 Gy (range 12-20 Gy). A total of 64 patients (25%) experienced an ARE, of which 19 were permanent. Rather than volume, maximal linear dimension in the Z (craniocaudal) dimension was associated with toxicity; a threshold length of 3.28 cm was associated with an ARE, with a 72.5% sensitivity and a 58.3% specificity. In addition, parietal lobe involvement for superficial lesions and temporal lobe involvement for deep lesions were associated with an ARE. Size remains the dominant predictor of toxicity following SRS, but overall rates of AREs were lower than anticipated based on baseline features, suggesting that dose and size were relatively dissociated through volume staging. Further techniques need to be assessed to optimize outcomes.

A Unique Volumetric Modulated Arc Stereotactic Radiosurgery (SRS)Treatment Planning Approach for Volume Staged SRS to Large Arteriovenous Malformation

The management of large Arteriovenous Malformation AVMs (> 10cc) using volume staged Stereotactic Radiosurgery (VS SRS) usually requires more than 2 VS SRS procedures. VS SRS downsizes the treatment volume per stage allowing effective higher dose of SRS to relative smaller volumes of target to reduce risk of SRS induced brain necrosis. It is imperative to maintain the SRS treatment plan quality matrix of conformity and dose gradient at optimal values to minimize the adverse radiation effects to surrounding brain tissues. However, VS SRS plans can present a challenge at treatment planning given the angioarchitecture of staged volumes and total volume, delivery technique and modality limitations.A 37-year-old female patient has history of headaches, intraventricular hemorrhage, and cerebral arteriovenous malformation AVM in the right parietal lobe. This large AVM (16.5cc) scored 4 on Spetzler-Martin grading system. Patient was simulated with large board CT simulator using an SRS mask. 1 mm thickness of CT images with IV contrast per CTA protocol were obtained and imported into the TPS. MRA images data sets and Angio CBCT scans from arteriogram were registered to CT Simulation scans for contouring AMV nidus. The nidus was divided into 3 sub volumes of 8 cc, 4.5cc and 4 cc, respectively. The dose of 20 Gy was prescribed to entire volume of nidus and portions of total dose were delivered to sub volumes with interval of 2-4 weeks. The VMAT inverse treatment plans were generated for each volume/isocenter using non-coplanar arcs. to be delivered on HDMLC. Collimator and arc angles were configured geometrically to minimize dose spillage between staged volumes. Planning objectives including generalized uniform equivalent dose gEUD were assigned to planning volumes and OARs. Normal tissue objective was enabled, structure resolution was set to 1.25mm, and AAA calculation grid was set to 1mm. Individual and composite plans isodoses and DVHs were examined repetitively during the planning and optimization iterations to confirm meeting the acceptable VS SRS plan quality matrix or to adjust if needed. All three individual sub volume plans passed IMRT QA (> 90%, DTA 1mm, %DD 2%) RESULTS: The composite plan maximum dose was 33.3 Gy, minimum dose for total nidus volume was 94%, and 95.2%, 100%, 109% for three sub volumes of nidus, respectively. V95%was > 95% and D95% was > 95% for all three sub volumes and total volume in the composite plan. The mean dose was 27.7 Gy. CI was 0.63, PITV was 1.57, R50 was 4.36 while GI was 2.77, V12 was 52.9cc (3.9%).The proposed unique VMAT VS SRS for large AVM achieves adequate and comparable treatment planning quality parameters when evaluated with published literature covering VS SRS delivery with different treatment modalities such as robotic radiosurgery systems. Our preliminary results from previous treated patients using same planning technique showed good response rate and very low rate of brain necrosis.F. Wang: None. D. Soultan: None. H. Jiang: None. N. Demez: None.

Two-Fraction Proton Beam Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations

Stereotactic radiosurgery (SRS) is a well-established treatment option that can obliterate cerebral arteriovenous malformations (AVMs). However, larger AVMs are more challenging to manage, with lower rates of obliteration and higher risk of complications. In this study, we report the obliteration rate and associated adverse effects of planned two-fraction proton SRS (PSRS) used to treat patients with larger AVMs that were deemed inoperable.A retrospective analysis including 75 patients with cerebral AVMs who received two-fraction PSRS at our institution between 1991 and 2019 was conducted. The median AVM nidus volume was 21.5 cc (range 1.4-58.1 cc). AVMs were located in critical/deep locations (basal ganglia, thalamus, or brainstem) in 21.3%. The median total dose for PSRS was 16 Gy(RBE) delivered in two fractions at a median of 7 days apart (range 1-82 days). Factors associated with obliteration and hemorrhage were assessed via univariable and multivariable analyses.Median follow up was 90 months (range 0.9-223.4 months). Total (8 patients, 11%) or partial (28 patients, 37%) obliteration was achieved among 48% of AVMs at a median time of 85.4 months (range 12.2-222.7 months). Five-year cumulative incidence of total obliteration was 29%. Five-year cumulative incidence of hemorrhage post-PSRS was 33%. Lesions with higher AVM scores were more likely to hemorrhage (P = 0.042). The most common adverse effect was Grade 1 headache acutely (11%) and long-term (9%). One patient developed a Grade 2 generalized seizure disorder.Planned two-fraction PSRS may be an effective and safe treatment option for achieving obliteration in patients with larger cerebral AVMs that are inoperable. Post-treatment hemorrhage remains a potential adverse event.D.W. Kim: None. G. Lee: None. P.H. Chapman: None. M.R. Bussiere: Consultant; American College of Radiology. J. Daartz: None. J.S. Loeffler: None. H.A. Shih: Employee; Dartmouth Hitchcock. Research Grant; AbbVie, NIH. Honoraria; UpToDate. Consultant; Cleveland Clinic. Speaker's Bureau; prIME Oncology. advisory; The Radiosurgery Society. director of clinical operations; Massachusetts General Hospital. clinical operational leader; Massachusetts General Hospital.

Hemodynamic Analysis of Cerebral AVMs with 3D Phase-Contrast MR Imaging.

The hemodynamics associated with cerebral AVMs have a significant impact on their clinical presentation. This study aimed to evaluate the hemodynamic features of AVMs using 3D phase-contrast MR imaging with dual velocity-encodings. Thirty-two patients with supratentorial AVMs who had not received any previous treatment and had undergone 3D phase-contrast MR imaging were included in this study. The nidus diameter and volume were measured for classification of AVMs (small, medium, or large). Flow parameters measured included apparent AVM inflow, AVM inflow index, apparent AVM outflow, AVM outflow index, and the apparent AVM inflow-to-outflow ratio. Correlation coefficients between the nidus volume and each flow were calculated. The flow parameters between small and other AVMs as well as between nonhemorrhagic and hemorrhagic AVMs were compared. Patients were divided into hemorrhagic (n = 8) and nonhemorrhagic (n = 24) groups. The correlation coefficient between the nidus volume and the apparent AVM inflow and outflow was .83. The apparent AVM inflow and outflow in small AVMs were significantly smaller than in medium AVMs (P < .001 for both groups). The apparent AVM inflow-to-outflow ratio was significantly larger in the hemorrhagic AVMs than in the nonhemorrhagic AVMs (P = .02). The apparent AVM inflow-to-outflow ratio was the only significant parameter that differed between nonhemorrhagic and hemorrhagic AVMs, suggesting that a poor drainage system may increase AVM pressure, potentially causing cerebral hemorrhage.

Outcome of intracerebral cavernoma treated by Gamma Knife radiosurgery based on a double-blind assessment of treatment indication

BackgroundThe benefit and the risk profile of Gamma Knife radiosurgery (GKRS) for intracerebral cavernoma remains incompletely defined in part due to the natural history of low incidence of bleeding and spontaneous regression of this vascular malformation. In this study, we retrieved cases from a prospectively collected database to assess the outcome of intracerebral cavernoma treated with GKRS using a double blinded review process for treatment.MethodsFrom 2003 to 2018, there were 94 cases of cavernoma treated by GKRS in the doubly blinded assessments by two experienced neurological and approved for GKRS treatment. All the patients received GKRS with margin dose of 11–12 (Gray) Gy and afterwards were assessed for neurological outcome, radiologic response, and quality of life.ResultsThe median age of the patients was 48 (15–85) years with median follow up of 77 (26–180) months post SRS. The mean target volume was 1.93 ± 3.45 cc. In those who has pre-SRS epilepsy, 7 of 16 (43.7%) achieved seizure freedom (Engel I/II) and 9 of 16 (56.3%) achieved decreased seizures (Engel III) after SRS. Rebleeding occurred in 2 cases (2.1%) at 13 and 52 months post SRS. The radiologic assessment demonstrated 20 (21.3%) cases of decreased cavernoma volume, 69 (73.4%) were stable, and 5 (7.3%) increased size. Eighty-seven of 94 (92.5%) cases at the last follow up achieve improvement in their quality of life, but 7 cases (7.4%) showed a deterioration. In statistical analysis, the effective seizure control class (Engel I/II) was highly correlated with patient harboring a single lesion (p < 0.05) and deep seated location of the cavernoma (p < 0.01). New neurological deficits were highly correlated with decreased mental (p < 0.001) and physical (p < 0.05) components of quality of life testing, KPS (p < 0.001), deep seated location (p < 0.01), and increased nidus volume (p < 0.05). Quality of life deterioration either in physical component (p < 0.01), mental component (p < 0.01), and KPS (p < 0.05) was highly correlated with increased cavernoma volume.ConclusionLow margin dose GKRS for intracerebral cavernoma offers reasonable seizure control and improved quality of life while conferring a low risk of treatment complications including adverse radiation effect.

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.

Predictive Factors of Radiation-Induced Changes Following Single-Session Gamma Knife Radiosurgery for Arteriovenous Malformations.

We evaluated for possible predictors of radiation-induced changes (RICs) after gamma knife radiosurgery (GKRS) for arteriovenous malformations (AVMs). We identified the nidal component within AVMs to analyze the correlation between the volume of brain parenchyma within the 50% isodose line (IDL) and RICs. We retrospectively reviewed patients with AVMs who underwent a single-session of GKRS at our institution between 2007 and 2017 with at least a 2-year minimum follow-up. Follow-up magnetic resonance images were evaluated for newly developed T2 signal changes and the proportions of nidus and intervening parenchyma were quantified. A total of 180 AVM patients (98 males and 82 females) with a median age of 34 years were included in the present study. The overall obliteration rate was 67.8%. The median target volume was 3.65 cc. The median nidus and parenchyma volumes within the 50% IDL were 1.54 cc and 2.41 cc, respectively. RICs were identified in 79 of the 180 patients (43.9%). AVMs associated with previous hemorrhages showed a significant inverse correlation with RICs. In a multivariate analysis, RICs were associated with a higher proportion of brain parenchyma within the 50% IDL (hazard ratio (HR) 169.033; p < 0.001) and inversely correlated with the proportion of nidus volume within the 50% IDL (HR 0.006; p < 0.001). Our study identified that a greater proportion of brain tissue between the nidus within the 50% IDL was significantly correlated with RICs. Nidus angioarchitectural complexity and the absence of a prior hemorrhage were also associated with RICs. The identification of possible predictors of RICs could facilitate radiosurgical planning and treatment decisions as well as the planning of appropriate follow-up after GKRS; this could minimize the risk of RICs, which would be particularly beneficial for the treatment of incidentally found asymptomatic AVMs.

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

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

Possible Association Between Rupture and Intranidal Microhemodynamics in Arteriovenous Malformations: Phase-Contrast Magnetic Resonance Angiography-Based Flow Quantification

To examine a potential association between intranidal microhemodynamics and rupture using a phase-contrast magnetic resonance angiography (PCMRA)-based flow quantification technique in arteriovenous malformations (AVMs). We retrospectively collected data on 30 consecutive patients with AVMs (23 unruptured and 7 ruptured). Based on PCMRA data, maximal (Vmax) and mean (Vmean) intranidal velocities were calculated. Logistic regression analysis was performed to assess factors associated with previous AVM rupture. All ruptures occurred within 6 months before PCMRA. The mean nidus volume was 4.7 mL. Eleven patients (37%) had deep draining vein(s), and 6 patients (20%) had a deep-seated nidus. The mean ± standard deviation Vmean and Vmax were 9.6 ± 2.8 cm/second and 66.7 ± 26.2 cm/second, respectively. The logistic regression analyses revealed that higher Vmax (P= 0.075, unit odds ratio [OR]= 1.05, 95% confidence interval [95% CI]= 1.00-1.10) was significantly associated with prior hemorrhage. The receiver-operating curve analyses demonstrated that a Vmean of 10.8 cm/second (area under the curve= 0.671) and Vmax of 90.2 cm/second (area under the curve= 0.764) maximized the Youden Index. A Vmax > 90 cm/second was significantly associated with AVM rupture both in the univariate (P= 0.025, OR= 9.0, 95% CI=1.3-61.1) and multivariate (P= 0.008, OR= 51.7, 95% CI= 2.8-968.3) analyses. Presence of faster velocities in intranidal vessels may suggest aberrant microhemodynamics and thus be associated with AVM rupture. PCMRA-based velocimetry seems to be a promising tool to predict future AVM rupture.

Gamma Knife Radiosurgery for Incidental, Symptomatic Unruptured, and Ruptured Brain Arteriovenous Malformations

Background: This study was performed to investigate clinical characteristics and outcome after gamma knife radiosurgery (GKS) in patients with incidental, symptomatic unruptured, or ruptured arteriovenous malformations (AVMs). Methods: A total of 491 patients with brain AVMs treated with GKS from June 2002 to September 2017 were retrospectively reviewed. All patients were classified into the incidental (n = 105), symptomatic unruptured (n = 216), or ruptured AVM (n = 170) groups. Results: The mean age at diagnosis of incidental, symptomatic unruptured, and ruptured AVMs was 40.3, 36.7, and 27.6 years, respectively. The mean nidus volume was 3.9, 5.7, and 2.4 cm³, respectively. Deep venous drainage was identified in 34, 54, and 76% patients, respectively. There were no significant differences in obliteration rates after GKS between the 3 groups (64.8, 61.1, and 65.9%, respectively) after a mean follow-up period of 60.5 months; however, patients with incidental AVM had a significantly lower post-GKS hemorrhage rate than patients with symptomatic unruptured or ruptured AVMs (annual hemorrhage rate of 1.07, 2.87, and 2.69%; p = 0.028 and p = 0.049, respectively). Conclusions: There is a significant difference in clinical and anatomical characteristics between incidental, symptomatic unruptured, and ruptured AVMs. The obliteration rate after GKS is not significantly different between the 3 groups. Meanwhile, an older age at diagnosis and lower hemorrhage rate after GKS in incidental AVMs suggest that they have a more indolent natural course with a lower life-long risk of hemorrhage.

Does Endovascular Treatment with Curative Intention Have Benefits for Treating High-Grade Arteriovenous Malformation versus Radiosurgery? Efficacy, Safety, and Cost-Effectiveness Analysis

The treatment of high-grade arteriovenous malformations (AVMs) remains challenging. Microsurgery provides a rapid and complete occlusion compared with other options but is associated with undesirable morbidity and mortality. The aim of this study was to compare the occlusion rates, incidence of unfavorable outcomes, and cost-effectiveness of embolization and stereotactic radiosurgery (SRS) as a curative treatment for high-grade AVMs. A retrospective series of 57 consecutive patients with high-grade AVM treated with embolization or SRS, with the aim of achieving complete occlusion, was analyzed. Demographic, clinical, and angioarchitectonic variables were collected. Both treatments were compared for the occlusion rate and procedure-related complications. In addition, a cost-effectiveness analysis was performed. Thirty patients (52.6%) were men and 27 (47.4%) were women (mean age, 39 years). AVMs were unruptured in 43 patients (75.4%), and ruptured in 14 patients (24.6%). The presence of deep venous drainage, nidus volume, perforated arterial supply, and eloquent localization was more frequent in the SRS group. Complications such as hemorrhage or worsening of previous seizures were more frequent in the embolization group. No significant differences were observed in the occlusion rates or in the time necessary to achieve occlusion between the groups. The incremental cost-effectiveness ratio for endovascular treatment versus SRS was $53.279. Both techniques achieved similar occlusion rates, but SRS carried a lower risk of complications. Staged embolization may be associated with a greater risk of hemorrhage, whereas SRS was shown to have a better cost-effectiveness ratio. These results support SRS as a better treatment option for high-grade AVMs.

Type II Endoleak Nidus Volume on Arterial and Delayed Phases of Initial CT Angiography after Endovascular Abdominal Aortic Aneurysm Repair Predicts Persistent Endoleak and Aneurysm Sac Enlargement.

To evaluate type II endoleak nidus volume (ENV) in the arterial phase (ENVAP) and delayed phase (ENVDP) of the first postoperative CT angiography (CTA) as a predictor of persistent endoleak and aneurysm sac enlargement at follow-up CTA in patients with endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm. Ninety-three patients (mean age ± standard deviation, 72 years ± 8; range, 56-88 years) with EVAR and type II endoleak were included in a single-institution retrospective study conducted between March 1, 2005, and December 31, 2018. ENVAP, ENVDP, change of volume (ENVDP-AP), and percentage of ENVAP and ENVDP in aneurysm sac volume (ASV) (ENVAP/ASV%, ENVDP/ASV%, respectively) were measured on first postoperative CTA images. The mean follow-up was 31.6 months ± 26.6 (range, 6-163.8 months). Patients were divided into two groups (group A, spontaneous resolution of endoleak without intervention [n = 29] and group B, persistent endoleak at follow-up CTA [n = 64]) and compared by using the Mann-Whitney U, Wilcoxon signed rank, and Pearson χ2 tests. Receiver operating characteristic (ROC) analysis was used to compare accuracies of parameters at first postoperative CTA. The accuracy of ENVDP (area under the ROC curve [AUC], 0.78) was superior to the accuracy of ENVDP/ASV% (AUC, 0.76), ENVDP-AP (AUC, 0.74), ENVAP (AUC, 0.71), and ENVAP/ASV% (AUC, 0.69) in indicating persistent endoleak. In group B, 46 patients (72%) showed ASV enlargement and 44 patients (69%) underwent endoleak embolization. ENVAP (1.7 cm3 ± 2.9 vs 3.4 cm3 ± 4.2; P = .001), ENVDP (2.9 cm3 ± 3.8 vs 8.0 cm3 ± 9.6; P < .001), ENVDP-AP (1.1 cm3 ± 1.8 vs 4.5 cm3 ± 7.8; P < .001), ENVAP/ASV% (0.9% ± 1.5 vs 1.7% ± 2.2; P = .003), and ENVDP/ASV% (1.6% ± 2.2 vs 3.7% ± 3.6; P < .001) were smaller in group A than in group B. ENVDP of the first postoperative CTA is an accurate predictor of persistent endoleak compared with ENVAP, and persistent endoleak is associated with aneurysm sac enlargement, in which earlier intervention is recommended.© RSNA, 2021.

Stereotactic Radiosurgery With Versus Without Embolization for Brain Arteriovenous Malformations.

Prior comparisons of brain arteriovenous malformations (AVMs) treated using stereotactic radiosurgery (SRS) with or without embolization were inherently flawed, due to differences in the pretreatment nidus volumes. To compare the outcomes of embolization and SRS, vs SRS alone for AVMs using pre-embolization malformation features. We retrospectively reviewed International Radiosurgery Research Foundation AVM databases from 1987 to 2018. Patients were categorized into the embolization and SRS (E+SRS) or SRS alone (SRS-only) cohorts. The 2 cohorts were matched in a 1:1 ratio using propensity scores. Primary outcome was defined as AVM obliteration. Secondary outcomes were post-SRS hemorrhage, all-cause mortality, radiologic and symptomatic radiation-induced changes (RIC), and cyst formation. The matched cohorts each comprised 101 patients. Crude AVM obliteration rates were similar between the matched E+SRS vs SRS-only cohorts (48.5%vs 54.5%; odds ratio=0.788, P=.399). Cumulative probabilities of obliteration at 3, 4, 5, and 6 yr were also similar between the E+SRS (33.0%, 46.4%, 56.2%, and 60.8%, respectively) and SRS-only (32.9%, 46.2%, 56.0%, and 60.6%, respectively) cohorts (subhazard ratio (SHR)=1.005, P=.981). Cumulative probabilities of radiologic RIC at 3, 4, 5, and 6 yr were lower in the E+SRS (25.0%, 25.7%, 26.7%, and 26.7%, respectively) vs SRS-only (45.3%, 46.2%, 47.8%, and 47.8%, respectively) cohort (SHR=0.478, P=.004). Symptomatic and asymptomatic embolization-related complication rates were 8.3% and 18.6%, respectively. Rates of post-SRS hemorrhage, all-cause mortality, symptomatic RIC, and cyst formation were similar between the matched cohorts. This study refutes the prevalent notion that AVM embolization negatively affects the likelihood of obliteration after SRS.