Residual Arteriovenous Malformations Research Articles

Angiographic Evolution of Brain Arteriovenous Malformation Angioarchitecture After Partial Endovascular Treatment.

Endovascular embolization of brain arteriovenous malformations (AVMs) is sometimes intentionally partial, in the case of staged treatment for instance. Residual AVMs may be prone to angioarchitectural modification during follow-up. The objective of this work is to evaluate the nature and extent of these modifications. We performed a retrospective monocentric study on a cohort of adult patients treated by incomplete endovascular embolization for ruptured and unruptured AVMs with an available angiographic follow-up, without any intervening confounding event between the 2 angiographic examinations. AVM angioarchitectural modifications (arterial, nidal, and venous) were analyzed. Clinical and radiological data were tested in univariate analyses for association with the occurrence of AVM regression or progression. Eighty-two partial embolization sessions in 57 patients were included in the study. A 40% (33/82) rate of modification was found on follow-up, with 23/82 (28%) controls showing at least one angioarchitectural regression feature and 15/82 (18.3%) showing at least one angioarchitectural progression item. Nidal growth was the most frequent modification occurring after 12/82 (14.6%) embolizations. The only factor associated with nidal volume growth was a longer time interval between embolization and follow-up (median [IQR]: 190 [250] days vs 89.5[133] days in the subgroup without nidal growth; P = .02). Specific modifications of arterial supply, nidal anatomy, and venous drainage were identified and documented. Angioarchitectural modifications (both progression and regression) of brain AVMs are frequent findings after partial embolization. Nidal volume growth is associated with longer time intervals between embolization and follow-up.

Intraoperative selective cerebral angiography for microsurgical treatment of cerebral arteriovenous malformations in a hybrid operating room

Arteriovenous malformations (AVMs) of the brain are a congenital anomaly of the development of cerebral vessels, when instead of a normal capillary bed, a «network» of pathologically altered vessels is formed, through which arterial blood is shunted into the drainage venous system. Due to the thinned wall of the pathological vessels and high pressure in them, patients with AVMs are at risk of intracerebral hemorrhage up to 4 % annually, which determines the vital need for their treatment. Microsurgical removal of brain AVMs is considered the most radical and effective treatment method, the main goal of which is to completely disable the body of the malformation, since the remaining part can lead to the risk of postoperative bleeding. To ensure effective control over the completeness of AVM removal intraoperatively, two methods have been developed: selective cerebral angiography (SCAG) and indocyanine green video angiography (ICG-VA). According to the literature, SCAG provides a number of advantages in the intraoperative diagnosis of residual AVM parts compared to ICG-VA. The article analyzes our own experience in using intraoperative SCAG in the surgical treatment of AVM in a hybrid operating room and examines the literature data on the topic of the paper. Our study highlights the importance of using the method of intraoperative control through SCAG in order to improve the effectiveness of surgical treatment of cerebral AVMs.

Third Stereotactic Radiosurgery for Residual Arteriovenous Malformations: A Retrospective Multicenter Study

BACKGROUND AND OBJECTIVES: There are no studies evaluating the efficacy and safety of more than 2 stereotactic radiosurgery (SRS) procedures for cerebral arteriovenous malformations (AVM). The aim of this study was to provide evidence on the role of third single-session SRS for AVM residual. METHODS: This multicenter, retrospective study included patients managed with a third single-session SRS procedure for an AVM residual. The primary study outcome was defined as AVM nidus obliteration without AVM bleeding or symptomatic radiation-induced changes (RIC). Secondary outcomes evaluated were AVM obliteration, AVM hemorrhage, asymptomatic, and symptomatic RIC. RESULTS: Thirty-eight patients (20/38 [52.6%] females, median age at third SRS 34.5 [IQR 20] years) were included. The median clinical follow-up was 46 (IQR 14.8) months, and 17/38 (44.7%) patients achieved favorable outcome. The 3-year and 5-year cumulative probability rates of favorable outcome were 23% (95% CI = 10%-38%) and 53% (95% CI = 29%-73%), respectively. The cumulative probability of AVM obliteration at 3 and 5 years after the third SRS was 23% (95% CI = 10%-37%) and 54% (95% CI = 29%-74%), respectively. AVM bleeding occurred in 2 patients, and 1 of them underwent subsequent resection. The cumulative probability rate of post-SRS AVM hemorrhage remained constant at 5.3% (95% CI = 1%-16%) during the first 5 years of follow-up. Transient symptomatic RIC managed conservatively occurred in 5/38 patients (13.2%) at a median time of 12.5 (IQR 22.5) months from third SRS. Radiation-induced cyst formation was noted in 1 patient (4.2%) 19 months post-SRS. No mortality, radiation-associated malignancy, or permanent symptomatic RIC was noted during follow-up. CONCLUSION: A third single-session SRS to treat a residual intracranial AVM offers obliteration in most patients. The risk of RIC was low, and these effects were transient. While not often required, a third SRS can be performed in patients with persistent residual AVMs.

Partial Onyx embolization triggers spontaneous regression of cerebral AVM: A case report

Spontaneous regression of a cerebral arteriovenous malformations (AVMs) is a rare and poorly understood phenomenon. We present a case of unruptured cerebral AVM in a patient presenting with intermittent headache. In order to reduce hemorrhagic risk, the patient underwent partial embolization of the AVM with Onyx glue. Follow-up digital subtraction angiography (DSA) showed complete obliteration of the residual AVM three months after the treatment. In conclusion, partial Onyx embolization of cerebral AVM may be an etiological factor of spontaneous regression. In order to reduce hemorrhagic risk, targeted partial embolization of the AVM may be an alternative treatment for some cases.

Choroid plexus arteriovenous malformations: A systematic review.

To systematically review the reported outcomes and complications of different treatment options for choroid plexus arteriovenous malformations (AVMs), specifically focusing on surgical resection and endovascular embolization. A systematic literature review was performed using a PubMed query for studies published between January 1975 and July 2021. All studies describing the clinical presentation, management, and outcome of confirmed choroid plexus AVM cases were included. A total of 20 studies were included in the final analysis. Of these, 18 were singlepatient case reports, one article contained two patients, and a single study was a cohort of 24 patients. Patient age ranged from one day to 61 years, with a mean of 31.8±20.4 years. Most choroid plexus AVMs were located in the lateral ventricles (14 patients, 70.0%), while there were four (20.0%) located in the third ventricle, and two in the fourth ventricle (10.0%). Almost all patients were treated with surgical resection (18 patients, 90%). In 14 patients (77.8%), complete resection of the AVM was achieved. A residual AVM was reported in one case (5.6%). Most patients were reported to have improved from their presentation status over time (14 patients, 70.0%). Presence or absence of long-term sequelae (e.g., neurologic deficits) were reported for 14 patients (70%). Eleven of these patients (78.6%) were reported to have no neurological sequelae. While data on choroid plexus AVMs remains limited, the available evidence suggests gross total resection of lesions in this location can be safely achieved with subsequent reduction in preoperative symptoms.

Value of contrast-enhanced MR angiography for the follow-up of treated brain arteriovenous malformations: systematic review and meta-analysis.

To estimate the diagnostic value of contrast-enhanced MR angiography (CE-MRA) in identifying residual brain arteriovenous malformations (AVMs) after treatment. We retrieved appropriate references from the electronic databases of PubMed, Web of Science, Embase, and Cochrane Library, and then evaluated the methodology quality of included references using the QUADAS-2 tool. We calculated the pooled sensitivity and specificity by applying a bivariate mixed-effects model and detected the publication bias using Deeks' funnel plot. The values of I2 were used to test heterogeneity and meta-regression analyses were performed to search for the causes of heterogeneity. We included 7 eligible studies containing 223 participants. Compared with a gold standard, the overall sensitivity and specificity of CE-MRA in detecting residual brain AVMs were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00), respectively. Based on the summary ROC curve, the AUC was 0.89 (95% CI 0.86-0.92). Heterogeneity could be observed in our study, especially for the specificity (I2 = 74.23%). Furthermore, there was no evidence of publication bias. Our study provides evidence that CE-MRA has good diagnostic value and specificity for the follow-up of treated brain AVMs. Nevertheless, considering the smallsamplesize, heterogeneity, and many factors that may affect the diagnostic accuracy, future large-sample, prospective studies are necessary to validate the results. • The pooled sensitivity and specificity of contrast-enhanced MR angiography (CE-MRA) in detecting residual arteriovenous malformations (AVMs) were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00). • The four-dimensional CE-MRA showed less sensitivity than the three-dimensional CE-MRA for treated AVMs. • CE-MRA is helpful to identify residual AVMs and reduce excessive DSA during follow-up.

Surgical treatment of arteriovenous malformations of the buttock

For symptomatic buttock arteriovenous malformations (AVMs), embolization techniques and surgical resection have been suggested as treatment options. Our aim was to evaluate the feasibility and long-term results after a single surgical resection. Twelve patients had undergone surgical resection without preoperative embolization. Of the 12 patients, 11 had had incomplete procedures, 9 of whom had undergone arterial embolization 1 to 3years previously. All the patients were symptomatic. Computed tomography scans showed AVMs located in the cellular spaces with preservation of the gluteal muscle. The median follow-up time was 80months. On the last follow-up computed tomography scan, 67% had had no residual AVM. The use of preoperative embolization, especially with nonresorbable embolic material (Onyx; Medtronic, Dublin, Ireland), makes AVM resection and imaging follow-up more difficult because of artifacts and should be avoided.

New aneurysm formation and regrowth associated with rebleeding of residual pediatric ruptured arteriovenous malformation: patient series.

If complete obliteration of ruptured pediatric arteriovenous malformation (AVM) cannot be achieved, the appropriate follow-up duration and predictors of rebleeding remain unknown. Pediatric patients with ruptured AVMs admitted to the authors' hospital within the past 30 years were evaluated. Rebleeding was confirmed in two patients. The first patient was a 5-year-old boy who experienced right thalamic hemorrhage. AVM was found in the bilateral thalamus and treated with stereotactic radiosurgery (SRS). New aneurysm formation and residual AVM regrowth were confirmed 21 years after the SRS. Eight months later, rebleeding occurred. The second patient was a 5-year-old boy who underwent removal of a left cerebellar hemorrhage and AVM. The residual AVM was treated with SRS. Residual AVM regrowth was detected at 6 years 7 months after SRS. Five months later, new aneurysm formation was confirmed. Two additional days later, rebleeding occurred. New aneurysm formation and residual AVM regrowth may predict rebleeding and can occur >20 years after the initial rupture and treatment. If AVM obliteration is not achieved, long-term follow-up is needed, even in adulthood, with attention to new aneurysm formation and residual AVM regrowth. Further treatment is recommended if these findings are confirmed.

Arteriovenous Malformation Associated with Intravenous Leiomyomatosis of the Uterus: Characteristic CT Findings and Treatment by Embolization and Surgery

Seven consecutive female patients with pathologically confirmed arteriovenous malformation (AVM) with intravenous leiomyomatosis (IVL) of the uterus (age range, 32–61 years; mean age, 43 years) treated between 2005 and 2021 from a single institution were reviewed. Computed tomography (CT) findings of congenital pelvic AVM of 10 female patients were compared with those of AVM with IVL. Characteristic CT findings of AVM with IVL revealed a focal soft tissue mass inside a dilated venous structure of the AVM. Multiple sessions of transvenous coil embolization of the AVM with or without the injection of ethanol were performed. After complete (6/7, 86%) or partial (1/7, 14%) embolization of the AVM, complete surgical resection of the IVL and embolized AVM mass was performed in 4 patients. Patients with lung metastasis or residual embolized AVM masses are under follow-up with antiestrogen hormonal therapy.

Repeat stereotactic radiosurgery for cerebral arteriovenous malformations.

The purpose of this retrospective, single-institution study was to evaluate radiological and clinical outcomes of patients managed with repeat stereotactic radiosurgery (SRS) for residual cerebral arteriovenous malformation (AVM) after prior SRS. The authors evaluated the clinical and radiological outcomes of consecutive patients treated with repeat single-session SRS for a residual brain AVM from 1989 to 2021. In total, 170 patients underwent repeat SRS for AVM (90 [52.9%] females; median [interquartile range] age at the first SRS procedure 28 [21.5] years; median [interquartile range] age at the second SRS procedure 32 [22.5] years). After repeat SRS, the actuarial 3-, 5-, and 10-year AVM obliteration rates were 37.6%, 57.3%, and 80.9%, respectively. Higher obliteration rates were associated with margin dose ≥ 19 Gy (p = 0.001). After the second SRS procedure, hemorrhage occurred in 8.2% of patients and was lethal in 1 patient. The risk factors of intracranial hemorrhage were age < 18 years (p = 0.03) and residual AVM diameter > 20 mm (p = 0.004). Lower obliteration rates were noted in patients with residual AVM diameter > 20 mm (p = 0.04) and those < 18 years of age (p = 0.04). Asymptomatic, symptomatic, and permanent radiation-induced changes (RICs) after the second SRS procedure occurred in 25.9%, 8.8%, and 5.3% of patients, respectively, and were associated with RIC after the first SRS procedure (p = 0.006). There was 1 case of a radiation-induced meningioma 12 years after SRS. Repeat SRS is a reasonable therapeutic option, in particular for patients with residual AVM. Repeat SRS was associated with more favorable outcomes in adult patients and those with residual AVM smaller than 20 mm in maximum diameter. To increase the rate of residual AVM obliteration, a prescription dose ≥ 19 Gy should ideally be used for repeat SRS.

Role of Indocyanine Green with FLOW 800 in Removal of Hidden Arteriovenous Malformations

Indocyanine green videoangiography (ICG-VA) with FLOW 800 (Carl Zeiss AG) has been used as a visualization tool to guide arteriovenous malformation (AVM) surgery since 2011. We performed a systematic review and evaluated the quality of evidence available on this topic. In addition, we present a series of our own cases demonstrating the unique use of ICG-VA in the localization and removal of deeper seated AVMs. Using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines for systematic reviews, we identified studies related to ICG-VA with FLOW 800 in AVM surgeries using search terms. The studies were screened and reviewed, and the quality of evidence was analyzed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) criteria. We performed a retrospective review of our own cases of AVM removal with ICG-VA and FLOW800. Our search revealed 27 relevant studies, 17 of which met our inclusion criteria. The quality of the body of evidence was determined to be "very low" using the GRADE criteria. We used ICG-VA with FLOW 800 analysis for 14 cases of microsurgical AVM removal. This technique provided unique insights into the localization of deep seated AVMs in 8 cases (57%). No residual AVM was found when assessed by the 6-month follow-up angiogram. We present cases highlighting the usefulness of this technique for the localization of certain AVMs. We believe the use of ICG-VA can guide the removal of deeper seated AVMs, because it can reveal surface feeders and draining veins that can be followed to a hidden nidus. Larger, registry-based studies are needed to confirm these findings and improve the overall quality of evidence.

A Machine Learning Model Predicts the Outcome of SRS for Residual Arteriovenous Malformations after Partial Embolization: A Real-World Clinical Obstacle

To propose a machine learning (ML) model predicting the favorable outcome of stereotactic radiosurgery (SRS) for residual brain arteriovenous malformation (bAVM) after partial embolization. One hundred and thirty bAVM patients who underwent partial embolization followed by SRS were reviewed retrospectively. Patients were split at random split into training datasets (n= 100) and testing datasets (n= 30). Radiomics and dosimetric features were extracted from pre-SRS treatment images. Feature selection was performed to select appropriate radiomics and dosimetric features. Three ML algorithms were applied to construct models using selected features respectively. A total of 9 models were trained to predict favorable outcomes (obliteration without complication) of bAVMs. The efficacy of these models was evaluated on the testing dataset using mean accuracy (ACC) and area under the receiver operating characteristic curve (AUC). The obliteration rate of this cohort was 70.77% (92 of 130) with a mean follow-up of 43.8 months (range, 12-108 months). Favorable outcomes were achieved in 89 patients (68.46%). Four radiomics features and 7 dosimetric features were selected for ML model construction. The dosimetric support vector machines (SVM) model showed the best performance on the training dataset, with an ACC of 0.74 and AUC of 0.78. The dosimetric SVM model also showed the best performance on the testing dataset, with an ACC of 0.83 and AUC of 0.77. Dosimetric features are good predictors of prognosis for patients with partially embolized bAVM followed by SRS therapy. The use of ML models is an innovative method for predicting favorable outcomes of partially embolized bAVM followed by SRS therapy.

"Craniotomy Within Craniotomy" Technique for Safe Resection of an Intracranial Arteriovenous Malformation With Frontal Bony Erosion: 2-Dimensional Operative Video.

Surgical resection is one option in the treatment of large high-grade brain arteriovenous malformations (AVMs). Resection of AVMs with skull-eroding components can be challenging due to the risk of excessive bleeding from these components during craniotomy and bone flap removal. We present a case of a 25-yr-old woman who presented with an acute onset right-sided frontal headache. She was found to have a large, frontal Spetzler-Martin grade IV AVM with an associated dural AVM. The AVM had caused focal erosions of the right frontal bone by a venous varix traversing the region of the calvarial defect. An elective staged endovascular embolization followed by surgical resection was recommended considering the patient's young age and the large size of the AVM located in a noneloquent area. Given the high risk of intraoperative hemorrhage during the craniotomy portion of the procedure, a "craniotomy within craniotomy" approach was planned. During this approach, a small rectangle of bone, including the portion eroded by the venous varix, was left in place, while the larger bone flap surrounding it was removed for an initial approach to the AVM. The small bony piece was safely removed at later stages of resection once the arterial feeders had been reasonably obliterated. Immediate postoperative catheter angiogram demonstrated good filling of the intracranial vascular territories with no residual AVM. The patient developed mild left facial and left hand weakness postoperatively, which resolved after 2 wk of follow-up. The patient remained neurologically intact on further follow-up.

840 Obstructive to Central: A switch in sleep apnea type after arteriovenous malformation rupture

Abstract Introduction Sleep apnea and stroke have long been shown to be linked, with sleep apnea increasing the risk for stroke and stroke leading to sleep apnea. When the latter occurs, it can present as central sleep apnea (CSA), often in the form of Cheyne-Stokes breathing (CSB), and has been shown to resolve over time. We present a patient with persistent CSA after severe hemorrhagic stroke secondary to rupture of a temporal/thalamic arteriovenous malformation (AVM). Report of case(s) A 33-year-old man with a history of obstructive sleep apnea (OSA) presented to our clinic for re-evaluation of his disease. He was diagnosed with OSA in 2006 at which time he was 270 pounds with a body mass index (BMI) of 36.7, thus the OSA was thought to be secondary to obesity. When he presented to our clinic 10 years later, he had lost approximately 80 pounds after suffering multiple strokes. In 2014, he had a left temporal lobe hemorrhage due to rupture of a left temporal/thalamic AVM and required decompressive hemicraniectomy. In 2015, he had a re-bleed of this AVM, with new hemorrhage extending inferiorly into the left cerebral peduncle and pons, and superiorly into the left parietal periventricular white matter anteriorly along the optic tract. Ultimately, he was treated with stereotactic radiotherapy to the AVM nidus with no residual AVM. However, he has chronic encephalomalacia of the left basal ganglia, thalamus, temporal, parietal, and occipital lobes with extension into the left cerebral peduncle and changes consistent with radiation necrosis. His residual symptoms are aphasia and right-sided hemiplegia and although his snoring resolved with weight loss, his mother noticed pauses in his breathing overnight. A repeat sleep study done in 2016 showed 27 central apneas and 0 obstructive apneas with an AHI of 5.4 events/hour. He was subsequently studied on ASV with residual AHI of 0.4 events/hour. Conclusion Although patients with OSA may be at higher risk for stroke, it is important to re-evaluate their sleep apnea after such an event to ensure appropriate diagnosis and treatment going forward. Support (if any):

Anesthetic Management of Awake Craniotomy for Resection of the Language and Motor Cortex Vascular Malformations

Although the safety and feasibility of awake craniotomy are well established for epilepsy and brain tumor surgery, its application for resection of vascular lesions, including arteriovenous malformations (AVMs) and cavernomas, is still limited. Apart from the usual challenges of awake craniotomy, vascular lesions pose several additional problems. Our goal is to determine the safety and practicality of awake craniotomy in patients with cerebral vascular malformations located near the eloquent areas, using a refined anesthetic protocol. A retrospective case series was performed on 7 patients who underwent awake craniotomy for resection of AVMs or cavernomas located in the eloquent language and motor areas. Our protocol consisted of achieving deep sedation, without a definitive airway, using a combination of propofol, dexmedetomidine, and remifentanil/fentanyl during scalp block placement and surgical exposure, then transitioning to a wakeful state during the resection. Six patients had intracranial AVMs, and 1 patient had a cavernoma. Six patients had complete resection; however, 1 patient underwent repeat awake craniotomy for residual AVM nidus. The patients tolerated the resection under continuous awake neurologic and neurophysiologic testing without significant perioperative complications or the need to convert to general anesthesia with a definitive airway. Awake craniotomy for excision of intracranial vascular malformations located near the eloquent areas, in carefully selected patients, can facilitate resection by allowing close neuromonitoring and direct functional assessment. A balanced combination of sedative and analgesic medications can provide both adequate sedation and rapid wakeup, facilitating the necessary patient interaction and tolerance of the procedure.

MRI-Guided Laser Interstitial Thermal Therapy for Radiation Necrosis in Previously Irradiated Brain Arteriovenous Malformations

Radiation necrosis (RN) is a well-described complication after radiosurgery (SRS) for intracranial pathologies. It has been reported most frequently after SRS for brain metastases but has also been reported in up to 33% of patients with SRS-treated brain arteriovenous malformations (AVM).1 Treatment with chronic steroids has remained first-line therapy for several reasons: (1) many cases of RN can resolve spontaneously over time; and (2) most cases were treated initially with SRS owing to concerns for surgical morbidity of AVM resection, and in some cases, residual live AVM may coexist with RN.

Abstract TMP118: Clinical Outcomes of Surgical Resection After Stereotactic Radiosurgery Among Patients With Cerebral Arteriovenous Malformations

Introduction: Surgical treatment of arteriovenous malformations (AVMs), particularly higher grade lesions, can be aided by staged treatment consisting of stereotactic radiosurgery (SRS) followed by surgical resection in a delayed fashion. This strategy can be used to downgrade the AVM S-M grade, reduce blood flow through the AVM and often results in histopathological changes making AVMs more amenable to microsurgical resection. We present our 28-year clinical experience in managing AVMs with pre-operative SRS as a surgical adjunct. Methods: We retrospectively reviewed and analyzed records of all patients treated for cerebral AVMs between February 1991 and July 2019 at our institution. All patients that underwent SRS, with and without embolization, followed by microsurgery were included in the study. Of the 1245 cerebral AVM patients treated at our institution, 62 patients met eligibility criteria. Univariate and multivariate regression analysis was performed where appropriate to examine relationships between key variables and outcomes. Results: The majority of lesions (50%) were high grade (SM 4-5), 28.6% were intermediate (SM 3), while 21.4% were low grade (SM 1-2). Hemorrhage was the presenting sign among 22.6% of patients. Complete resection was achieved among 64.5%, 79% and 82% of patients after first, second and third surgical stages respectively; 16.1% of patients had partial resection requiring further treatment. Radiographic cure was achieved among 53 patients (85.5%), while 8 (12.9%) patients had residual AVM at last follow up. Six of 8 patients without radiographic cure received post-operative SRS. Thirty-seven patients (63.8%) had improved (26, 44.8%) or stable mRS scores (11, 19%), while 21 (36.2%) had a decline in mRS at final follow up compared to mRS at presentation; this includes 4 (6.9%) deaths due to hemorrhage, outside of the perioperative period, but occurring during follow up prior to AVM obliteration. Conclusion: SRS is a useful adjunct in the surgical management of cerebral AVMs. Multimodal therapy allowed for high obliteration rates with acceptable morbidity in this series of patients with predominantly high grade AVMs.

Pediatric intracranial arteriovenous malformations: a single-center experience

OBJECTIVEIntracranial arteriovenous malformations (AVMs) are a common cause of intracranial hemorrhage in children. Exploring outcomes of treatment and factors that predict recurrence may help guide the management of pediatric AVMs. In this study, the authors review a single-center experience with pediatric AVMs, aiming to identify factors contributing to recurrence and areas for improvement in treatment.METHODSA single-center retrospective review of patients ages 0–18 years with AVMs in the period from 2005 to 2018 was conducted. Demographic, clinical, and radiographic data were collected and examined to compare the clinical and functional outcomes of patients managed with and those managed without open microsurgical resection.RESULTSOne hundred five patients were diagnosed and treated during the study period. Fifty (47.6%) had been treated surgically and 35 (33.3%) nonsurgically, and 20 (19%) had been treated primarily at an outside institution and thus were excluded from further analysis. Of the 50 treated surgically, 92% had complete obliteration on postoperative imaging, with the remaining patients having residual AVM and undergoing re-resection or SRS, ultimately resulting in a 96% radiographic cure rate. The surgically treated patients were followed up for an average of 3.34 years. Eighty-two percent had a modified Rankin Scale (mRS) score of 0–2. There was a recurrence rate of 12%, with the time to recurrence averaging 327.86 days (range 85–596 days). Of the 35 patients managed without open surgery, 77% underwent serial imaging surveillance, 20% underwent endovascular embolization, and 3% underwent stereotactic radiosurgery. Radiographic cure was seen in 6% of those treated nonsurgically, and all had undergone endovascular treatment alone. The nonsurgically treated patients were followed up for an average of 2.14 years. Eighty percent had an mRS score of 0–2.CONCLUSIONSThe data revealed that patients with lower-grade AVMs treated surgically and those with higher-grade AVMs managed without surgery have good functional and clinical outcomes. A high rate of recurrence was noted, and the possible contributing factors were explored. The authors encourage further study into mechanisms to reduce AVM recurrence in pediatric patients and look forward to advances in the medical management of lesions that are considered unresectable.

Abstract TP491: Hypofractionated Stereotactic Radiosurgery for Brain AVM Post Aruba: Obliteration, Complication, and Hemorrhage Rates

Introduction: Patients harboring brain AVMs associated with moderate-high surgical morbidity (large lesions, deep location and eloquent cortex) are increasingly undergoing hypofractionated stereotactic radiosurgery (SRS) at our institution. Most published literature is based on a single fraction SRS technique. In this review we sought to evaluate/present our hypofractionated SRS experience using the Accuray Cyberknife device. Hypothesis: Cyberknife Stereotactic Radiosurgery (C-SRS) can be used for a high risk brain arteriovenous malformations (AVMs) with high rates of successful complete obliteration and low rates of hemorrhagic, death and major disability. Methods: We performed a retrospective analysis of all patients having undergone Cyberknife SRS for brain AVMs between 2013-2019 at a large community based tertiary care health system and identified 33 patients. Of these patients 12 had a minimum of 2 year follow-up. We divided the patients into hemorrhagic and non-hemorrhagic presentations, prior endovascular treatment with embolization and based on Spetzler Martin grades. Results: 58% males with median age of 44 and 9% presenting with hemorrhage. Median planning target volume (PTV) was 7.2 cc (range 1.25-15.56 cc) and median HFSRT dose was three fractions (range 3-5) of 10.25 Gy (range 8.5-11 Gy) each. Complete obliteration was achieved in 100% of patients after salvage SRS 21 Gy x1 fraction to a residual AVM volume in 2 patients. The median time to obliteration was 747 days. 3 of 12 patients suffered radiation necrosis1 patient with a large AVM (maximum diameter of 4 cm and PTV of 12.6 cc) suffered re-hemorrhage and radiation necrosis, but ultimately completely obliterated after 402 days and was left with mRS ≤2). Conclusion: Although we have a small sample size, fractionated SRS with Cyberknife resulted in 100% obliteration, low rates recurrent hemorrhage and low morbidity (no mortality). These outcomes are superior to published single fraction radiosurgery results in high risk patients. Further study with a prospective multicenter registry or as part of a larger RCT is warranted.

Interventional Management of Arteriovenous Malformations

Arteriovenous malformations (AVMs) are fast flow malformations characterized by the presence of arteriovenous shunting. These congenital lesions can be evolutive, leading to serious complications such as bleeding, skin ulceration, and cardiac failure. The interventional radiologist plays an important role in the management of these patients. He should be involved in the clinical evaluation to make the proper diagnosis, evaluate the symptoms and potential indication for endovascular treatment. This evaluation should be done in a multidisciplinary clinic with access to plastic surgeons, internal medicine and dermatologist, as well as specific specialists that might need to be implicated (ENT surgeon in the face and neck area, for example). The Schobinger clinical classification is important to assess patient evolution and indicate intervention. We recommend to treat symptomatic or evolutive AVMs. Doppler ultrasound is the first imaging examination that should be performed. Then, MR angiography or computed tomography angiography (CTA) can be proposed depending on the anatomic area involved. Embolization is currently the first line of treatment for these patients. There is currently promising research in the identification of genetic markers and molecular target(s) but there is no recognized pharmacologic treatment for AVM available yet. Digital substraction angiography (DSA) is usually performed for guidance during the embolization session but is also essential to properly classify a specific lesion, according to its anatomy. The anatomic classifications proposed by Cho and Yakes are both useful to choose the best therapeutic approach: Endovascular, direct puncture, retrograde venous approach or a combination of these techniques. Ethanol is the most efficient agent but is at higher risk of skin necrosis and nerve injury and should therefore be used with caution in dangerous territories. Glue and Onyx are liquid agents that are also well suited to occlude the nidus; they can be used in association with ethanol. On the venous side, mechanical occlusion with coils or Amplatzer plugs is mostly used. Again, they can be used in association with a liquid agent (Ethanol, glue or Onyx) to reflux in the nidus. Surgery can be indicated to resect residual AVM following embolization if residual symptoms are present and the planned surgery is feasible, with relative safety.