Arteriovenous Malformations Nidus Research Articles

350 A Comparison of Incidental and Symptomatic Unruptured Brain Arteriovenous Malformations in Children

INTRODUCTION: Unruptured brain arteriovenous malformations (AVMs) may present with headaches, seizures, and/or neurologic deficits. A smaller number of cases may be discovered incidentally. These lesions remain incompletely understood due to their sparse reporting. METHODS: We performed a retrospective analysis of patients presenting with brain AVMs from 1998 to 2021 at the University of California, San Francisco. Inclusion criteria included age ≤18 at time of presentation with angiographically-proven unruptured AVM diagnosed postnatally. RESULTS: Of 76 children with unruptured AVMs, 66 (86.8%) presented with headaches, seizures, and/or neurologic deficit. Ten (13.1%) were incidentally discovered through unrelated disease workup (50%), cranial trauma (40%), or research study participation (10%). Compared to symptomatic unruptured AVMs, incidental unruptured AVMs possessed smaller mean nidus maximum diameter (2.82 ± 1.1 vs. 3.98 ± 1.52 cm, p = 0.025) and deep venous drainage proportion (20% vs. 61%, p = 0.036). They also presented at earlier ages (10 ± 5.2 vs. 13.5 ± 4 years, p = 0.043) with longer durations to first treatment (541 ± 922 vs. 196 ± 448 days, p = 0.005). During the period of observation, one patient developed recurring headaches and demonstrated AVM nidus growth. Four AVMs greater than 3 centimeters or in deep location were treated with radiosurgery. Six other AVMs were treated with surgical resection with 2 receiving preoperative embolization. Seven AVMs (70%) were obliterated on last follow-up. Postprocedural complications included 2 transient neurologic deficits following resection and 1 delayed seizure development following radiosurgery. The mean follow-up period was 5.1 ± 5.8 years without any hemorrhage episodes. CONCLUSIONS: A substantial proportion of pediatric patients with unruptured AVMs are discovered incidentally. With earlier presentation and more elementary angioarchitecture than symptomatic unruptured AVMs, these incidental lesions provide a snapshot into AVM natural history before symptom development or rupture.

303 Frameless Angiography-Based Gamma Knife Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations

INTRODUCTION: Traditional GammaKnife radiosurgery (GKRS) of brain arteriovenous malformations (AVMs) using digital subtraction angiography requires head immobilization using a stereotactic frame. METHODS: This is a retrospective review of unruptured AVM patients who underwent frameless GKRS. Thin-cut magnetic resonance imaging and 3-dimensional DSA were obtained without a stereotactic frame for all patients. The imaging studies were merged for contouring of the AVM nidus. During GKRS treatment, patients were immobilized using an individually molded thermoplastic mask. RESULTS: Thirty-one patients were included in the analysis. The median age is 45.0 years (IQR 28.0-55.0). The median nidus size is 3.0 cm (IQR 2.0-3.4). One patient had a Spetzler-Martin grade I, 11 had a grade II, 11 had a grade III, 6 had a grade IV, and 2 had a grade IV AVM. Eleven patients underwent pre-radiosurgical embolization, two patients had previous microsurgical resection, and one patient had prior radiosurgery. The median administered dose was 20 Gy (IQR 18.0-21.0). Twenty-three patients were treated in a single fraction, 6 in 3 fractions, and two patients received 5 fractions. All patients completed their treatment with the planned radiation dose without complications. CONCLUSIONS: This is the first study that integrates digital subtraction angiography in the treatment planning of brain AVMs using GKRS without utilizing a stereotactic head frame. Frameless GKRS provides numerous advantages over frame-based techniques including improved patient experience, the capability of fractionation, thus, expanding the eligibility of more AVMs for radiosurgery, while maintaining high spatial resolution of the AVM using angiography data.

Rupture-related quantitative hemodynamics of the supratentorial arteriovenous malformation nidus.

The hemodynamics of a brain arteriovenous malformation (AVM) nidus may be closely related to clinical presentation. The authors of this study aimed to explore the hemorrhagic quantitative hemodynamic indicators of the nidus through quantitative digital subtraction angiography (QDSA). The quantitative hemodynamic parameters were generated from QDSA. Three data sets were used to explore independent quantitative hemodynamic indicators associated with AVM rupture. The training data set was exploited to discover independent quantitative hemodynamic indicators of AVM rupture by performing univariate and multivariate logistic regression analyses. The authors plotted receiver operating characteristic curves to validate the diagnostic performance of the hemorrhagic hemodynamic indicators using the training and two external validation data sets. Kaplan-Meier survival analysis was adopted to verify the predictive power of these risk indicators of future hemorrhage in the external prospective validation data set. A total of 151 patients were included in this study, 91 in the training set and 30 in each of the two validation sets. A higher stasis index and slower transnidal relative velocity (TRV) of the nidus were significantly correlated with AVM rupture. The areas under the curve (AUCs) of the stasis index (nidus) were 0.765 and 0.815 and those of the TRV (nidus) were 0.735 and 0.796, respectively, in the training and retrospective external validation sets. Kaplan-Meier survival analysis confirmed the validity of the stasis index and TRV in predicting future rupture risk in the prospective validation data set (p = 0.008 and 0.041, respectively, log-rank test). A higher stasis index (nidus) and slower TRV (nidus) in QDSA were associated with AVM rupture and were effective indicators of future hemorrhage, suggesting that the core mechanisms underlying AVM rupture could be intravascular blood stasis and occlusive hyperemia of the nidus.

Letter: Risk for Hemorrhage the First 2 Years After Gamma Knife Surgery for Arteriovenous Malformations: An Update.

To the Editor: We have read with great interest the article by Karlsson et al1 titled “Risk for Hemorrhage the First 2 Years After Gamma Knife Surgery for Arteriovenous Malformations: An Update.” The premise of this study was based on the findings of a 2001 study that demonstrated the risk of hemorrhage after gamma knife surgery (GKS) for arteriovenous malformations (AVMs) to be strongly correlated with large AVM size, older age, and lower therapeutic dose.2 However, contradictory data collected 17 years later revealed the risk of hemorrhage was not related to AVM size or patient age.3 To clearly define predictors of hemorrhage, the authors retrospectively reviewed the outcome of 5037 patients treated with GKS for AVM.1 The average rate of hemorrhage was determined to be 2.4%, where larger AVM size, older age, and lower therapeutic dose served as significant (P < .01) risk factors, consistent with findings from the original study.1,2 AVM location (P = .16), embolization (P = .27), and history of pre-GKS hemorrhage (P = .20) were found to be nonsignificant predictors for post-GKS hemorrhage.1 The identification of clear hemorrhage risk factors after GKS for AVM in this large, heterogeneous cohort provides clinicians with more concrete guidelines for AVM management.1 The clinical management of cerebral AVMs remains challenging due to AVM heterogeneity in size, biological composition, anatomic location, and associated symptoms.4 Thus, the treatment of AVMs to reduce hemorrhage risk must be conducted in an individualized manner specific to patient presentation and AVM profile. Although no formal guidelines exist regarding treatment of unruptured AVMs, a landmark randomized trial of unruptured brain arteriovenous malformations (trial) revealed the superiority of medical management compared with interventional therapy.5 Interventional therapy was associated with an increased risk of stroke or death as compared with medical management alone (P < .0001; hazard ratio 3.70; 95% CI 1.85–7.14).5 Five-year follow-up data confirmed these findings.6 With this understanding, along with identifying general risk factors and prevalence rates of AVM hemorrhage after GKS, it would be valuable to investigate the impact of hemorrhage on mortality and morbidity in this cohort of patients undergoing interventional therapy. Doing so, while controlling for confounding variables, such as the Spetzler-Martin grade, AVM nidus morphology or location, would be clinically significant and aid in deciding which patients would truly benefit from GKS. Hemorrhage is the leading cause of morbidity and mortality associated with AVMs.7 Consequently, common symptoms of AVM-related hemorrhage such as seizures and headaches severely impair quality of life (QOL).8,9 While it can be hypothesized that post-GKS AVM hemorrhage would have profound implications for QOL outcomes, there are no reports in the literature detailing this relationship. Future studies should investigate the impact of post-GKS hemorrhage on QOL metrics, especially as GKS continues to improve and be used for more complex disease. This study by Karlsson et al1 provides a strong foundation for the future investigation of invaluable QOL metrics to guide medical decision-making in a manner that targets patient-specific QOL discrepancies while bridging this apparent gap in the literature.

Microsurgical resection of a ruptured right peri-ventricular brain arteriovenous malformation with preoperative embolization.

A 41-year-old female presented with a headache and left inferior quadrantanopia. Imaging demonstrated a clot spanning the atrium of the ventricle to the superior parietal lobule (SPL), with a small arteriovenous malformation (AVM) nidus outside the atrium of the ventricle. The nidus was supplied by parieto-occipital arterial (P4) feeders with a single atrial draining vein. Pre-operative embolization of a pedicle with Onyx provided a surgical marker. A parietal craniotomy was performed with a trans-cortical SPL approach. During AVM resection, the draining vein was injured, which was stabilized using a temporary clip to "spot weld" the defect and continue nidus dissection with patent venous outflow. After careful dissection, coagulation, and division of all the arterial feeders, the AVM was mobilized and the draining vein was clipped, coagulated, and divided. Follow-up indocyanine green angiography and cerebral angiography both confirmed complete resection of the AVM. The patient consented to the procedure and to publication.

A comparison of incidental and symptomatic unruptured brain arteriovenous malformations in children.

Patients with unruptured brain arteriovenous malformations (AVMs) may present with headaches, seizures, and/or neurological deficits. A smaller number of cases may be discovered incidentally. These lesions remain incompletely understood due to their sparse reporting. Herein, the authors describe the largest series to date comparing the presentation, angioarchitecture, and management of incidental versus symptomatic unruptured AVMs in children. The authors performed a retrospective analysis of patients who presented with brain AVMs from 1998 to 2022 at the University of California, San Francisco. Inclusion criteria were age ≤ 18 years at the time of presentation and an angiographically proven unruptured AVM that had been diagnosed postnatally. Of 76 children with unruptured AVMs, 66 (86.8%) presented with headaches, seizures, and/or neurological deficit. Ten AVMs (13.1%) were incidentally discovered through unrelated disease workup (50%), cranial trauma (40%), or research study participation (10%). Compared with patients with symptomatic unruptured AVMs, patients with incidental unruptured AVMs had a smaller mean ± SD maximum nidus diameter (2.82 ± 1.1 vs 3.98 ± 1.52 cm, p = 0.025) and fewer had deep venous drainage (20% of patients vs 61%, p = 0.036). They also presented at an earlier age (10 ± 5.2 vs 13.5 ± 4 years, p = 0.043) and with longer duration to first treatment (541 ± 922 vs 196 ± 448 days, p = 0.005). During the observation period, 1 patient developed recurring headaches and demonstrated AVM nidus growth. Four AVMs greater than 3 cm in size or in a deep location were treated with radiosurgery. Six other AVMs were treated with resection, with 2 receiving preoperative embolization. Eight AVMs (80%) were obliterated on last follow-up. Postprocedural complications included 2 transient neurological deficits after resection and 1 case of delayed seizure development after radiosurgery. The mean follow-up period was 5.7 ± 5.7 years without any hemorrhage episodes. A substantial proportion of pediatric patients with unruptured AVMs are discovered incidentally. With earlier presentation and more elementary angioarchitecture than symptomatic unruptured AVMs, these incidental lesions provide a snapshot into the natural history of AVM before symptom development or rupture.

Ethanol Embolization of Chest Wall Arteriovenous Malformations: Four-Year Findings

Objectives: To summarize the clinical characteristics and investigate the efficacy of ethanol embolotherapy in the treatment of chest well arteriovenous malformation (AVM). Treatment-associated complications were also explored. Materials and Methods: Between March 2017 and August 2021, 32 consecutive patients (mean age, 23.7 years; age range, 5–54 years) who underwent ethanol embolotherapy for chest well AVMs under general anesthesia were included in this study. Embolization was performed through a direct puncture, transarterial catheterization, or a combination of the 2 procedures. The mean follow-up duration after the last treatment was 18.0 months (range, 3–42 months). The degree of devascularization on follow-up (assessed using angiography or computed tomography), and the clinical signs and symptoms of AVMs were evaluated as the therapeutic outcomes. The major and minor complications associated with the procedures were recorded. Results: A total of 103 embolization procedures (mean, 3.2; range, 2–7) comprising 101 ethanol embolization and 2 coil embolizations were performed on 32 patients with chest wall AVMs. The AVM nidus was accessed through the transarterial approach alone in 4 patients, by direct puncture in 11, and a combined procedure in 17 patients. Overall, more than 80% of the procedures were performed using the combined approach. Complete AVM devascularization was achieved in 12 (37.5%) patients. Moreover, 76% to 99% AVM was achieved in 18 patients (56.3%), and 50% to 75% in 2 patients (6.3%). Bleeding, pain, heart failure, and cosmetic deformities were the indications for treatment. For 3 patients (3/32, 9.4%) who had bleeding, the treatment stopped the hemorrhage. Complete pain relief was reported in 8 patients (8/32, 25.0%), whereas complete relief from congestive heart failure post-embolization was observed in 5 of the 6 patients with congestive heart failure (5/6, 83.3%). Complete correction of cosmesis deformities after embolization was achieved in 10 patients (10/32, 31.3%). Two patients who underwent surgery to correct persistent deformity after embolization only showed insignificant improvement. In addition, 6 (18.8%) patients developed 13 complications including blister, necrosis, hemothorax, transient hemoglobinuria, and transient pulmonary artery hypertension. Conclusions: Ethanol embolotherapy is a safe and effective procedure for chest well AVMs. Surgery is required for some patients with residual cosmesis deformity. Clinical Impact Currently, there is no standard treatment for chest well AVMs due to their rarity and high heterogeneity. The present study shows that thanol embolotherapy is a safe and clinically effective treatment procedure for the chest well AVMs. Transarterial embolization in combination with direct puncture embolization can reach the AVM nidus. Ethanol embolotherapy can achieve complete obliteration of the AVM nidus in the majority of patients. Surgery may still be needed to correct cosmetic deformity after embolization. The present study provides valuable evidence to inform clinical decision-making.

Transvenous embolization of conus spinal arteriovenous malformation: illustrative case

Spinal arteriovenous malformations (AVMs) are the most challenging spinal vascular malformations. Endovascular transarterial embolization of spinal AVM has been well described. However, transvenous embolization has not been previously reported. In this case report, the authors describe transvenous embolization of a recurrent intramedullary/conus spinal AVM that was previously deemed unamenable to endovascular therapy. A 30-year-old female presented with debilitating lumbar back pain and was found to have an intramedullary spinal AVM at the level of the conus medullaris. Initially, the AVM was treated with endovascular arterial embolization and subsequently with microsurgical resection. However, on follow-up angiography, the AVM had recurred. Further arterial embolization was deemed not possible because of anatomical challenges. After careful consideration, endovascular transvenous embolization was performed with successful occlusion of the AVM nidus. Transvenous embolization is an alternative route for endovascular treatment of spinal AVMs that have an accessible single draining vein.

Hemifacial Spasm Caused by Cerebellar Arteriovenous Malformation and Spasm-Relief after Nidus Removal

Secondary hemifacial spasm (HFS) occurs by a conflict between the facial nerve and intracranial pathology, such as cerebellopontine angle tumor or vascular abnormality like arteriovenous malformation (AVM) or aneurysm. HFS caused by AVM is rare, and optimal combination of treatment options has not been established. AVM treatment with or without microvascular decompression (MVD) of the facial nerve was provided in the previous studies, and the outcomes in terms of spasm relief have been successful. Here, we report a case of HFS caused by cerebellar AVM. HFS symptom disappeared after AVM nidus removal without MVD of the facial nerve.

Detection and Segmentation of Arteriovenous Malformation Lesions Using a Two-Stage Deep Learning Strategy

<h3>Purpose/Objective(s)</h3> Identifying and accurately delineating malformed vascular lesions is critical in radiosurgery for arteriovenous malformations (AVMs). Applying deep learning to automatic detection and segmentation of AVM lesions may help the treatment planning be more efficient. This study aims to develop an artificial intelligence model to recognize and contour the AVM nidus using deep learning methods. <h3>Materials/Methods</h3> We retrospectively collected two hundred twenty-three AVM patients treated by radiosurgery from 2003 to 2020. Among the 233 cases, 179 were in the training set, and 44 were in the testing set. The contrasted magnetic resonance image of time-of-flight was the sequence for image acquisition. The targeted area depicted in the previous treatment planning was the ground truth. We utilized a two-stage deep learning strategy. The first stage is the yolov5 model to detect the bounding box of the AVM lesions. Then we used the U-Net++ for the auto-segmentation based on the bounding box generated from the first stage in the second stage. We trained and evaluated the first and second stage models separately for 100 epochs, and the model with the lowest error was chosen as the optimal model. <h3>Results</h3> In the first stage, the recall and precision of the yolov5 model were 0.93 and 0.91 for the training data set and 0.88 and 0.93 for the testing data set, respectively. The second U-Net++ segmentation model achieved a Dice score of 0.98 for both the training and testing data sets. The segmentation results demonstrated the statistically significant difference between the Dice score calculated from the predicted segmentation and reference bounding box (p<0.0001). Besides, we observed that segmentation accuracy gradually decreased as the bounding box expanded. <h3>Conclusion</h3> Our two-stage model exhibits satisfactory accuracy in the images' auto-detection and auto-delineation of AVM lesions. The model needs to be further verified by more data before clinical use. It is expected that such an AI model will improve the clinical process and reduce interobserver variation.

DNA methylation signatures on vascular differentiation genes are aberrant in vessels of human cerebral arteriovenous malformation nidus

Arteriovenous malformation (AVM) is a tangle of arteries and veins, rupture of which can result in catastrophic hemorrhage in vulnerable sites such as the brain. Cerebral AVM is associated with a high mortality rate in humans. The causative factor or the stimulus at the artery-venous junction and the molecular basis of the development and progression of cerebral AVM remain unknown. While it is known that aberrant hemodynamic forces in the artery-vein junction contribute to the development of AVMs, the mechanistic pathways are unclear. Given that various environmental stimuli modulate epigenetic modifications on the chromatin of cells, we speculated that misregulated DNA methylome could lead to cerebral AVM development. To identify the aberrant epigenetic signatures, we used AVM nidus tissues and analyzed the global DNA methylome using the Infinium DNA methylome array. We observed significant alterations of DNA methylation in the genes associated with the vascular developmental pathway. Further, we validated the DNA hypermethylation by DNA bisulfite sequencing analysis of selected genes from human cerebral AVM nidus. Taken together, we provide the first experimental evidence for aberrant epigenetic signatures on the genes of vascular development pathway, in human cerebral AVM nidus.

S3041 Hepatic Artery Dissection – A Case Report

Introduction: Visceral artery aneurysms are rare pathologies with reported incidence rates between 0.01% to 0.2%; even rarer are hepatic artery dissections (HAD). Most aneurysms rupture or are incidentally found on autopsy, but imaging advancements has enabled earlier identification of aneurysms; in this case, a HAD. Case Description/Methods: A 77-year-old female with medical history pertinent for sickle cell trait, acquired factor VIII inhibitor coagulopathy, history of type 2 thoracic aortic dissection, and hypertension presented to the emergency room with a week of mild fatigue, postprandial epigastric burning pain, and intermittent stabbing right upper quadrant pain. Right upper quadrant ultrasound demonstrated a hypervascularized right hepatic lobe mass with large tortuous internal vessels. CT abdomen & pelvis without contrast showed a large hypodensity in the right liver with curvilinear density. MRI demonstrated large arteriovenous malformation (AVM) within the right hepatic lobe and focal hepatic parenchymal hemorrhage centered within AVM nidus. Gastroenterology was consulted and CT angiogram findings were suspicious for common HAD, proper hepatic & intrahepatic pseudoaneurysms, and intrahepatic rupture. Interventional radiology was consulted. Hepatic angiogram showed a large defect in the proximal hepatic artery with brisk opacification, thought to represent a pseudoaneurysm. This prompted framing coil placement across the large defect and coils extending from the proper hepatic artery to the common hepatic artery with significant reduction in forward flow & pseudoaneurysm opacification. Per hepatobiliary & vascular surgery, no need for additional surgical intervention. Postoperative course was complicated by fever & leukocytosis, worsening kidney injury, and anemia; attributed to the procedure and resolved with supportive care. Patient discharged on postoperative day 8 with outpatient follow-up. (Figure) Discussion: This case highlights the importance of imaging for earlier detection of hepatic artery aneurysms (HAA) in minimizing risk of catastrophic hemorrhage. HAA are rare but clinically important given they are associated with high incidence of rupture and mortality up to 20%. Although surgery is preferred for extrahepatic findings, endovascular interventions are favored for intrahepatic findings depending on size and presence of pseudoaneurysms, such as this case. They have led to more favorable short & longer-term outcomes and lower mortality & morbidity rates, particularly in poor surgical candidates.Figure 1.: Hepatic angiography and embolization was performed. A large defect with brisk opacification of the proper and common hepatic arteries were seen (A), prompting deploy of a framing coil. (B) Embolization was then performed on the hepatic artery with three coils (5mm, 6mm, & 8mm). Coils were examined from proper hepatic artery to the common hepatic artery. (C) Following placement of the coils, significant reduction in flow and opacification of the pseudoaneurysm was seen.

Spontaneous occlusion of the cerebral arteriovenous malformations

Spontaneous occlusion of arteriovenous malformations (AVM), characterized by complete disappearance of the AVM nidus and early venous drainage, and is a rare. The frequency of this phenomenon varied from 0.1 to 1.3 %.We analyzed two cases of spontaneous occlusion of cerebral AVMs with a non-hemorrhagic debut after 3 and 13 years in women aged 28 and 40 years, respectively. In both cases AVM was diagnosed during routine neuroimaging because of headache. Both patients had superficial small malformations. After discussing the risks of surgical treatment, both patients refused to perform any intervention. Scheduled angiography was performed 3 years after the diagnosis to follow-up the course of the disease and revealed complete disappearance of the AVM. Another patient noted persistent regression of headache after 3 years. Follow-up angiography was performed 13 years after diagnosis and confirmed spontaneous occlusion of the AVM. Given the data on the recurrence of the disease after spontaneous occlusion, such patients require long-term follow-up.When an AVM ruptures, hemodynamic changes may explain the thrombosis of the malformation, but the mechanisms of spontaneous occlusion in non-ruptured AVM remain unclear.

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.

Transvenous embolization of hemorrhagic brain arteriovenous malformations: Case reports and literature review.

IntroductionTransvenous embolization (TVE) has been proven to be safe and feasible as an alternative management of brain arteriovenous malformations (AVMs). We presented four patients with a hemorrhagic brain AVM who underwent TVE and reviewed the relevant literature.MethodsFour patients underwent TVE of a hemorrhagic brain AVM in our center between July 2019 and July 2020. We retrospectively collected and analyzed the clinical and imaging data of these patients and those reported in previously published studies.ResultsFour patients with a hemorrhagic brain AVM were included. Nidus sizes ranged from 0.79 to 2.56 cm. Spetzler-Martin grade ranged from grade II to grade III. The AVM nidus was located in a deep brain region in three patients. One patient underwent TVE alone and three underwent combined transarterial and transvenous approaches. Digital subtraction angiography (DSA) demonstrated complete obliteration of the vascular malformation after embolization in all four patients. Three patients were independent [modified Rankin Scale (mRS) score ≤ 2] at discharge. All four patients were independent at the last follow-up. AVM obliteration was confirmed in all four patients at the last angiographic follow-up.ConclusionTransvenous embolization can be used as an alternative treatment for contemporary management of brain AVMs, appropriate patient selection is essential to achieve a good clinical outcome.

Robot-Assisted Radiofrequency Ablation Combined with Thermodynamic Simulation for Epilepsy Reoperations.

Repeat craniotomies to treat recurrent seizures may be difficult, and minimally invasive radiofrequency ablation is an alternative therapy. On the basis of this procedure, we aimed to develop a more reliable methodology which is helpful for institutions where real-time image monitoring or electrophysiologic guidance during ablation are not available. We used simulation combined with a robot-assisted radiofrequency ablation (S-RARFA) protocol to plan and execute brain epileptic tissue lesioning. Trajectories of electrodes were planned on the robot system, and time-dependent thermodynamics was simulated with radiofrequency parameters. Thermal gradient and margin were displayed on a computer to calculate ablation volume with a mathematic equation. Actual volume was measured on images after the ablation. This small series included one pediatric and two adult patients. The remnant hippocampus, corpus callosum, and irritative zone around arteriovenous malformation nidus were all treated with S-RARFA. The mean error percentage of the volume ablated between preoperative simulation and postoperative measurement was 2.4 ± 0.7%. No complications or newly developed neurologic deficits presented postoperatively, and the patients had little postoperative pain and short hospital stays. In this pilot study, we preliminarily verified the feasibility and safety of this novel protocol. As an alternative to traditional surgeries or real-time monitoring, S-RARFA served as successful seizure reoperation with high accuracy, minimal collateral damage, and good seizure control.

Ischemia-induced inflammation in arteriovenous malformations.

The pathophysiology of development, growth, and rupture of arteriovenous malformations (AVMs) is only partially understood. However, inflammation is known to play an essential role in many vascular diseases. This feasibility study was conducted to investigate the expression of enzymes (cyclooxygenase 2 [COX-2] and NLRP3 [NOD-, LRR-, and pyrin domain-containing protein 3]) in the AVM nidus that are essential in their inflammatory pathways and to explore how these influence the pathophysiology of AVMs. The study group comprised 21 patients with partially thrombosed AVMs. The cohort included 8 ruptured and 13 unruptured AVMs, which had all been treated microsurgically. The formaldehyde-fixed and paraffin-embedded samples were immunohistochemically stained with a monoclonal antibody against COX-2 and NLRP3 (COX-2 clone: CX-294; NLRP3: ab214185). The authors correlated MRI and clinical data with immunohistochemistry, using the Trainable Weka Segmentation algorithm for analysis. The median AVM volume was 2240 mm3. The proportion of NLRP3-positive cells was significantly higher (26.23%-83.95%), compared to COX-2 positive cells (0.25%-14.94%, p < 0.0001). Ruptured AVMs had no higher expression of NLRP3 (p = 0.39) or COX-2 (p = 0.44), compared to nonruptured AVMs. Moreover, no patient characteristics could be reported that showed significant correlations to the enzyme expression. NLRP3 consistently showed an approximately 10-fold higher expression level than COX-2, making the inflammatory process in AVMs appear to be mainly associated with ischemic (NLRP3)-driven rather than with mechanical (COX-2)-driven inflammatory pathways. No direct associations between NLRP3 and COX-2 expression and radiological, standard histopathological, or patient characteristics were found in this cohort.

Frameless Angiography–Based Gamma Knife Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations: A Proof-of-Concept Study

Traditional Gamma Knife radiosurgery (GKRS) of brain arteriovenous malformations (AVMs) using digital subtraction angiography (DSA) requires head immobilization using a stereotactic frame. We describe our protocol of frameless GKRS using DSA while maintaining high spatial resolution for precision. This study is a retrospective review of patients with unruptured AVMs who underwent frameless GKRS. Magnetic resonance imaging and 3-dimensional DSA were obtained without a stereotactic frame for all patients. The imaging studies were merged for contouring of the AVM nidus. During GKRS treatment, patients were immobilized using an individually molded thermoplastic mask. Thirty-one patients were included in the analysis. The median age is 45.0years (interquartile range [IQR]: 28.0-55.0). The median nidus size is 3.0cm (IQR: 2.0-3.4). One patient had a Spetzler-Martin grade I, 11 had a grade II, 11 had a grade III, 6 had a grade IV, and 2 had a grade V AVM. Eleven patients underwent preradiosurgical embolization, 3 patients had previous microsurgical resection and/or embolization, and 1 patient had prior radiosurgery. The median administered dose was 20Gy (IQR: 18.0-21.0). All patients completed their treatment with the planned radiation dose without complications. This is the first study that integrates DSA in the treatment planning of brain AVMs using GKRS without utilizing a stereotactic head frame. Frameless GKRS provides numerous advantages over frame-based techniques including improved patient experience and the capability of fractionation and thus expanding the eligibility of more AVMs for radiosurgery, while maintaining high spatial resolution of the AVM using angiography data.

Impact of Pre-operative Embolization With Onyx for Brain Arteriovenous Malformation Surgery.

ObjectiveTo clarify the safety and efficacy of pre-operative embolization using Onyx liquid embolic agent (Onyx; ev3) compared with N-butyl cyanoacrylate (NBCA; Cordis Neurovascular, Inc.) or coils in cerebral arteriovenous malformation (AVM) surgery.MethodsThis was a retrospective review of a prospectively collected clinical database of brain AVMs treated at our institute from January 2005 to March 2021. A total of 38 consecutive patients who underwent AVM resection after pre-operative embolization were included. Based on pre-operative embolization materials, the patients were divided into the pre-Onyx group (n = 16), in which NBCA or coils were used for embolization, and the Onyx group (n = 22). Patient characteristics and treatment results were compared between the two groups.ResultsPatient characteristics were comparable between the two groups in terms of age, sex, and rupture status. While the Spetzler–Martin grade was also similar between the two groups, the location of the AVM nidus in the eloquent area was slightly higher in patients in the Onyx group (72.7%) than in patients in the pre-Onyx group (43.8%) (P = 0.09). The embolization rate was higher in the pre-Onyx group (mean: 63.0%; range: 12.7–100%) than in the Onyx group (mean: 50.0%; range: 15.8–100%), but the difference was not statistically significant (P = 0.06). The time needed for surgical removal was shorter in the Onyx group (mean: 354.8 min; range: 144–884 min) than in the pre-Onyx group (mean: 457.9 min; range: 240–1,294 min); however, this difference was not statistically significant (P = 0.13). The amount of intraoperative bleeding was significantly lower in the Onyx group (mean: 129.8 ml; range: 20–540 mL) than in the pre-Onyx group (mean: 448.8 mL; range: 120–1,550 ml) (P = 0.0008). The surgical complication rates were comparable between the two groups (pre-Onyx group, 18.8%; Onyx group, 4.5%; P = 0.29).ConclusionsPre-operative embolization with Onyx can significantly reduce the amount of intraoperative bleeding in AVM resection and may contribute to safe AVM surgery.

Role of i-CT, i-US, and Neuromonitoring in Surgical Management of Brain Cavernous Malformations and Arteriovenous Malformations: A Case Series

We retrospectively reviewed the institutional experience in patients who underwent microsurgical resection of cavernous malformations (CMs) or arteriovenous malformations (AVMs) using a multimodal intraoperative protocol including neuronavigation, intraoperative ultrasound (i-US), computed tomography (i-CT), and neuromonitoring. Twenty-four patients (14 male), with a mean age of 47.5 years (range 27-73), have been included: 20 of them suffered from CMs and 4 suffered from AVMs. Neuromonitoring was used in 18 cases, when lesions were located in eloquent areas; 2 patients underwent awake craniotomy. First, an i-CT scan with and without contrast was acquired after patient positioning. Navigated B-mode ultrasound acquisition was carried out after dural opening to identify the lesion (CMs or AVMs nidus). Following identification and resection of vascular lesions, postcontrast i-CT (or CT-angio) was performed to detect and localize any small or calcified remnant (in cases of CMs) or residual vessels feeding the nidus (in cases of AVMs). In 5 cases of CMs and in 1 case of AVM, i-CT identified small residual lesions. In these cases, new i-CT images were uploaded into the navigation system and used for further resection. i-US was useful before starting transsulcal or transcortical approach to identify the lesions and guide the trajectory of the approach. However, several artifacts were observed during subsequent steps of dissection, making image interpretation difficult. The combination of different intraoperative real-time imaging modalities (i-CT and i-US), coupled with neuromonitoring, in the surgical management of vascular lesions, particularly if located in eloquent areas, has a positive impact on clinical outcome.