The diagnosis and management of brain arteriovenous malformations

State of the Art in the Role of Endovascular Embolization in the Management of Brain Arteriovenous Malformations-A Systematic Review

As a significant cause of intracerebral hemorrhages, seizures, and neurological decline, brain arteriovenous malformations (bAVMs) are a rare group of complex vascular lesions with devastating implications for patients' quality of life. Although the concerted effort of the scientific community has improved our understanding of bAVM biology, the exact mechanism continues to be elucidated. Furthermore, to this day, due to the high heterogeneity of bAVMs as well as the lack of objective data brought by the lack of evaluative and comparative studies, there is no clear consensus on the treatment of this life-threatening and dynamic disease. As a consequence, patients often fall short of obtaining the optimal treatment. Endovascular embolization is an inherent part of multidisciplinary bAVM management that can be used in various clinical scenarios, each with different objectives. Well-trained neuro-interventional centers are proficient at curing bAVMs that are smaller than 3 cm; are located superficially in noneloquent areas; and have fewer, larger, and less tortuous feeding arteries. The transvenous approach is an emerging effective and safe technique that potentially offers a chance to cure previously untreatable bAVMs. This review provides the state of the art in all aspects of endovascular embolization in the management of bAVMs.

Brain AVMs-Related microRNAs: Machine Learning Algorithm for Expression Profiles of Target Genes

INTRODUCTION

microRNAs (miRNAs) are a class of non-coding RNAs playing a myriad of important roles in regulating gene expression. Of note, recent work demonstrated a critical role of miRNAs in the genesis and progression of brain arteriovenous malformations (bAVMs). Accordingly, here we examine miRNA signatures related to bAVMs and associated gene expression. In so doing we expound on the potential prognostic, diagnostic, and therapeutic significance of miRNAs in the clinical management of bAVMs.

METHODS

A PRISMA-based literature review was performed using PubMed/Medline database with the following search terms: "brain arteriovenous malformations", "cerebral arteriovenous malformations", "microRNA", and "miRNA". All preclinical and clinical studies written in English, regardless of date, were selected. For our bioinformatic analyses, miRWalk and miRTarBase machine learning algorithms were employed; the Kyoto Encyclopedia of Genes and Genomes (KEGG) database was quired for associated pathways/functions.

RESULTS

four studies were ultimately included in the final analyses. Sequencing data consistently revealed the decreased expression of miR-18a in bAVM-endothelial cells, resulting in increased levels of vascular endodermal growth factor (VEGF), Id-1, matrix metalloproteinase, and growth signals. Our analyses also suggest that the downregulation of miR-137 and miR-195* within vascular smooth muscle cells (VSMCs) may foster the activation of inflammation, aberrant angiogenesis, and phenotypic switching. In the peripheral blood, the overexpression of miR-7-5p, miR-629-5p, miR-199a-5p, miR-200b-3p, and let-7b-5p may contribute to endothelial proliferation and nidus development. The machine learning algorithms employed confirmed associations between miRNA-related target networks, vascular rearrangement, and bAVM progression.

CONCLUSION

miRNAs expression appears to be critical in managing bAVMs' post-transcriptional signals. Targets of microRNAs regulate canonical vascular proliferation and reshaping. Although additional scientific evidence is needed, the identification of bAVM miRNA signatures may facilitate the development of novel prognostic/diagnostic tools and molecular therapies for bAVMs.

Intra- and post-operative acute hemorrhagic complications of Onyx embolization of brain arteriovenous malformations: A single-center experience

Background

The intra- and post-operative acute (within 72 h) hemorrhagic complications of endovascular treatment (EVT) for a brain arteriovenous malformation (BAVM) are disastrous. Thus, further experiential summaries are required to fully understand them.

Materials and methods

This was a retrospective study of 25 patients with consecutive BAVM who were treated via EVT with Onyx embolization and suffered intra- and post-operative acute hemorrhage. The clinical and imaging data of the patients were recorded, analyzed, and discussed.

Result

Twenty-five patients were aged 11-70 years (mean, 37.2 ± 16.1 years), of whom 12 were female (48%, 12/25). Of the 25 hemorrhagic complications, 17 (68%, 17/25) were intraoperative, and 8 (32%, 8/25) were post-operative and occurred between 1 and 12 h after EVT. Of 17 intraoperative hemorrhages, 13 (76.5%, 13/17) were due to high-pressure Onyx casting. Of eight post-operative hemorrhages, six (75%, 6/8) were attributed to normal perfusion pressure breakthrough. The degree of nidus Onyx embolization was more than 2/3 or complete in seven (87.5%, 7/8) BAVMs. Draining vein occlusion was observed in eight (32%, 8/25) of 25 BAVMs. After hemorrhage, conservative treatment was administered in 12 (48%, 12/25) cases, and surgical management was performed in other cases. There were eight cases of mortality; the remaining 17 patients had follow-up data. Among them, 15 patients had good outcomes, with Glasgow Outcome Scale scores of 5 and 4, accounting for 60% (15/25).

Conclusion

In EVT for BAVMs, intra- and post-operative acute hemorrhagic complications are disastrous; only 60% of patients have a good outcome. Therefore, high-pressure Onyx casting or casting too much Onyx at one time to pursue a high degree of nidus embolization should be performed cautiously, and primary draining vein occlusion should be avoided. In short, EVT needs to be performed carefully.

Paediatric Cerebral Arteriovenous Malformation: Outcomes from a Singapore Children's Hospital

OBJECTIVES

Paediatric brain arteriovenous malformation (bAVM) is a rare and distinct clinical entity. There is a growing body of literature that support the success of multimodality approaches for this difficult condition. The authors aim to firstly, describe our institutional experience with a consecutive series of patients and next, corroborate our results with current literature.

MATERIAL AND METHODS

This is a single institution, retrospective study conducted over a 20-year period. Patients less than 19 years old with bAVM were included. Variables of interest included patient demographics, clinical presentation, neuroimaging features, bAVM characteristics and treatment modality. Functional outcomes were measured with modified Rankin scale (mRS).

RESULTS

There were 58 paediatric bAVMs, presenting at a mean age of 8.7 ± 4.2 years, and followed up for a mean duration of 7.7 years. Thirty-six patients (62.1%) underwent microsurgical resection, 10 patients had stereotactic radiosurgery (17.2%) and 2 patients had endovascular treatment (3.4%). 50 patients (86.2%) had a favourable outcome at 1-year follow up. Microsurgical resection and SRS had similar obliteration rates (resection 83.3%; SRS 80.0%) and recurrence (resection 10.0%; SRS 12.5%). There were 6 cases of bAVM recurrence (12.8%). This subgroup was noted to be less than 7.5 years old at presentation (OR 15.0, 95% CI 1.56 - 144), and less likely to present with bAVM rupture (OR 0.11, 95% CI 0.01 - 0.96).

CONCLUSION

This study describes our experience in managing paediatric bAVM, whereby monomodal therapy can still be effective. Of note, we also demonstrate the role of extended surveillance to detect recurrence.

Endovascular embolization for cases of 'hidden' pediatric cerebral arteriovenous malformations: A diagnostic & therapeutic challenge

BACKGROUND

Ruptured arteriovenous malformations (AVM) hold a larger proportion as the cause of spontaneous intracranial hemorrhage in children compared to those in adults. Although surgical excision still remains as the gold standard therapy for arteriovenous malformations, some smaller ones are reported to resolve from embolization alone. However, difficulty arises when small arteriovenous malformations are not detected on certain diagnostic modalities such as Computed Tomography Angiography (CTA), giving rise to false negatives, which may compromise appropriate management of patients. Endovascular embolization can be used as alternative options as diagnostic and therapy for invisible arteriovenous malformation in children. We report two cases of ruptured paediatrics arteriovenous malformations with a complication of hydrocephalus, managed with endovascular embolization and a cerebrospinal fluid diversionary procedure.

CASE DESCRIPTION

We report 2 case in from Dr. Soetomo academic general hospital in 2021, the first case was a fully conscious 6-year-old-female child with sudden left-sided weakness and severe headache in January, and the second case a 9-year-old female came with decreased consciousness in May. Both had evidence of intracerebral hemorrhage, intraventricular hemorrhage, and hydrocephalus on head radiological examination, but no visible vascular malformations on Computed Tomography Angiography. The first patient was treated with extra ventricular drainage initially, while the second case was not. Transfemoral cerebral angiography revealed small arteriovenous malformations in both patients, and both had successful endovascular embolization afterwards. The first case was shunt-free, while the second case had her drainage switched to ventriculoperitoneal shunt right after the embolization procedure. Both patients recovered fully without complications and sequelae, and were discharged afterwards.

DISCUSSION

Both patients did not undergo surgical resection of the arteriovenous malformations; the first case only underwent endovascular embolization, while the second case underwent embolization and ventriculoperitoneal shunting. The cases described here help highlight the irreplaceable role of Transfemoral Cerebral Angiography as a gold standard for cases for arteriovenous malformations compared to other modalities, such as Computed Tomography Angiography (CTA). Smaller arteriovenous malformations in paediatrics are reported to achieve complete radiological resolution, and cerebrospinal fluid diversion in hydrocephalic cases are not always performed. Several factors to be considered include initial consciousness and severity of neurological deficit, which were taken into account in the management of our patients.

CONCLUSION

Embolization procedures may be beneficial in some pediatric arteriovenous malformations, preferably in smaller ones that undetectable by angiography. Several factors such as the consciousness and neurological deficit upon initial presentation may help in the decision making of these cases.

Temporal-Spatial Feature Extraction of DSA Video and Its Application in AVM Diagnosis

Objectives: Brain arteriovenous malformation (AVM) is one of the most common causes of intracranial hemorrhage in young adults, and its expeditious diagnosis on digital subtraction angiography (DSA) is essential for clinical decision-making. This paper firstly proposed a deep learning network to extract vascular time-domain features from DSA videos. Then, the temporal features were combined with spatial radiomics features to build an AVM-assisted diagnosis model. Materials and method: Anteroposterior position (AP) DSA videos from 305 patients, 153 normal and 152 with AVM, were analyzed. A deep learning network based on Faster-RCNN was proposed to track important vascular features in DSA. Then the appearance order of important vascular structures was quantified as the temporal features. The structure distribution and morphological features of vessels were quantified as 1,750 radiomics features. Temporal features and radiomics features were fused in a classifier based on sparse representation and support vector machine. An AVM diagnosis and grading system that combined the temporal and spatial radiomics features of DSA was finally proposed. Accuracy (ACC), sensitivity (SENS), specificity (SPEC), and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of the radiomics model. Results: For cerebrovascular structure detection, the average precision (AP) was 0.922, 0.991, 0.769, 0.899, and 0.929 for internal carotid artery, Willis circle, vessels, large veins, and venous sinuses, respectively. The mean average precision (mAP) of five time phases was 0.902. For AVM diagnosis, the models based on temporal features, radiomics features, and combined features achieved AUC of 0.916, 0.918, and 0.942, respectively. In the AVM grading task, the proposed combined model also achieved AUC of 0.871 in the independent testing set. Conclusion: DSA videos provide rich temporal and spatial distribution characteristics of cerebral blood vessels. Clinicians often interpret these features based on subjective experience. This paper proposes a scheme based on deep learning and traditional machine learning, which effectively integrates the complex spatiotemporal features in DSA, and verifies the value of this scheme in the diagnosis of AVM.

Is smoking a risk factor for bleeding in adult men with cerebral arteriovenous malformations? A single-center regression study from China

OBJECTIVE

To assess whether smoking increases the risk of bleeding in patients with cerebral arteriovenous malformations (CAVM).

MATERIAL AND METHODS

According to our research plan, 385 CAVM patients admitted to Beijing Tiantan Hospital from December 2015 to January 2018 were included in this study, including 210 bleeding patients and 175 non-bleeding patients. We divided patients into three subgroups of current smokers, ex-smokers (those who quit smoking for one year or more) and non-smokers. The relationship between smoking and the risk of CAVM rupture was assessed by univariate and multivariate regression analysis.

RESULTS

Multivariate regression analysis showed that there was a statistically significant difference between current smoker and non-smoker (OR = 1.87, p = 0.019). Among the covariates of the multivariate regression analysis, the location, combined with blood flow-related intracranial aneurysms and size were related to the risk of CAVM bleeding.

CONCLUSION

Current smoking may increase the risk of CAVM bleeding; however, there was no significant correlation between ex-smoking and CAVM bleeding.

Pediatric intracranial arteriovenous malformations: a single-center experience

OBJECTIVE

Intracranial 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.

METHODS

A 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.

RESULTS

One 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.

CONCLUSIONS

The 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.

[Molecular mechanisms of growth and relapse of cerebral arteriovenous malformations]

Cerebral AVMs are not static congenital formations, they may grow, recur, and even appear de novo after complete resection, embolization, or radiosurgery. The author analyzes modern literature on the molecular mechanisms of AVM growth. The AVM intranidal vessels are exposed to abnormally high blood flows, which leads to the activation of molecular pathways in endothelial cells, causing proliferation and remodeling of AVM vessels. The existence of cerebral AVM is determined by more than 860 genes, the most important among them are the genetic mutations (SNPs) of VEGF, TGF-β, IL-6, MMP, ANG, ENG. The possible causes of AVM relapse after removal or total embolization are described, as well as the mechanisms of stimulation of angiogenesis after partial embolization: hemodynamic changes in AVM, aseptic inflammation in response to embolizate and the local regional hypoxia inside the AVM. In response to this, growth factors are expressed in the endothelium that further stimulate angiogenesis in AVM. Understanding the complex molecular biology of AVMs is critical to identifying and predicting their behavior, developing new treatments that improve the results of endovascular and surgical treatment.

Intradural spinal cord arteriovenous shunts in the pediatric population: natural history, endovascular management, and follow-up

BACKGROUND

Intradural spinal cord arteriovenous shunts represent a rare entity, particularly in the pediatric population, and clinical diagnosis can be challenging.

METHODS

We report the analysis of clinical, angioarchitectural, procedural, and follow-up data in a population of 36 children managed by our team between 2002 and 2017.

RESULTS

Hemorrhage occurred in 26 children (72%). Age at onset was 9.22 ± 3.65 years. Lesions were located at the thoracic level in 16 cases, at the cervical level in 15 cases, and the thoraco-lumbar region in 5 cases. A genetic or metameric syndrome was associated in 18 children (50%). Glue embolization provided complete occlusion in 5 children, subtotal in 7, and extensive in 14 without intraprocedural complications. We observed clinical normalization in 11 children, improvement in 11 cases, and stability in 3. Four children worsened during the follow-up, and one child died.

CONCLUSIONS

Endovascular staged glue embolization performed in experienced centers is safe in the treatment of pediatric intradural spinal cord arteriovenous shunts. Clinical and neuroradiological follow-up is mandatory, especially for pediatric patients.

Susceptibility-Weighted Angiography for the Follow-Up of Brain Arteriovenous Malformations Treated with Stereotactic Radiosurgery

The criterion standard for assessing brain AVM obliteration postradiosurgery is DSA. To explore the value of susceptibility-weighted angiography, we followed 26 patients with brain AVMs treated by radiosurgery using susceptibility-weighted angiography and DSA. Studies were evaluated by 2 independent readers for residual nidi. Susceptibility-weighted angiography demonstrated good intermodality (κ = 0.71) and interobserver (κ = 0.64) agreement, and good sensitivity (85.7%) and specificity (85.7%). Susceptibility-weighted angiography is a useful radiation- and contrast material-free technique to follow-up brain AVM obliteration postradiosurgery.

ACR Appropriateness Criteria® Cerebrovascular Disease

Diseases of the cerebral vasculature represent a heterogeneous group of ischemic and hemorrhagic etiologies, which often manifest clinically as an acute neurologic deficit also known as stroke or less commonly with symptoms such as headache or seizures. Stroke is the fourth leading cause of death and is a leading cause of serious long-term disability in the United States. Eighty-seven percent of strokes are ischemic, 10% are due to intracerebral hemorrhage, and 3% are secondary to subarachnoid hemorrhage. The past two decades have seen significant developments in the screening, diagnosis, and treatment of ischemic and hemorrhagic causes of stroke with advancements in CT and MRI technology and novel treatment devices and techniques. Multiple different imaging modalities can be used in the evaluation of cerebrovascular disease. The different imaging modalities all have their own niches and their own advantages and disadvantages in the evaluation of cerebrovascular disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Procedure for the Isolation of Endothelial Cells from Human Cerebral Arteriovenous Malformation (cAVM) Tissues

In this study, we successfully established a stable method for the isolation of endothelial cells (ECs) from human cerebral arteriovenous malformation (cAVM) tissues. Despite human cAVM tissues having a minor population of ECs, they play an important role in the manifestation and development of cAVM as well as in hemorrhagic stroke and thrombogenesis. To characterize and understand the biology of ECs in human cAVM (cAVM-ECs), methods for the isolation and purification of these cells are necessary. We have developed this method to reliably obtain pure populations of ECs from cAVMs. To obtain pure cell populations, cAVM tissues were mechanically and enzymatically digested and the resulting single cAVM-ECs suspensions were then labeled with antibodies of specific cell antigens and selected by flow cytometry. Purified ECs were detected using specific makers of ECs by immunostaining and used to study different cellular mechanisms. Compared to the different methods of isolating ECs from tissues, we could isolate ECs from cAVMs confidently, and the numbers of cAVM-ECs harvested were almost similar to the amounts present in vessel components. In addition to optimizing the protocol for isolation of ECs from human cAVM tissues, the protocol could also be applied to isolate ECs from other human neurovascular-diseased tissues. Depending on the tissues, the whole procedure could be completed in about 20 days.

Assessing the Role of Preoperative Embolization in the Surgical Management of Cerebral Arteriovenous Malformations

BACKGROUND

Preoperative embolization is established as an advantageous adjunct in multimodality treatment of cerebral arteriovenous malformations (AVMs). However, the benefit of preoperative embolization in AVMs with favorable surgical risk profile is debatable, because it has yet to be supported by evidence in comparative studies. In this study, we assessed outcome of surgically treated patients in a comparative setting.

METHODS

Our institutional AVM database of retrospectively and prospectively collected data between 1990 and 2015 was reviewed. Patients with complete clinical data who underwent surgical resection for AVMs were included. We performed a 1:1 ratio propensity score match for baseline variables that differed between patients with or without preoperative embolization. Differences in surgical risk and outcomes were evaluated between these 2 groups.

RESULTS

AVM size, eloquence, deep drainage, middle cerebral artery feeder, and ruptured presentation differed significantly between the 2 groups. Forty-eight patients without preoperative embolization were matched to 48 with embolization, with no significant differences in baseline variables or AVM characteristics between the 2 groups. We found no significant differences in AVM obliteration and postoperative modified Rankin Scale (mRS) score between embolized and nonembolized patients, respectively. Change in mRS score from preoperative score was also not significant, although more embolized patients had a decline in mRS score. Secondary outcome measures including duration of surgery (P = 0.172), intraoperative bleeding (P = 0.280), duration of hospitalization (P = 0.368), and postoperative symptoms were also similar between both groups.

CONCLUSIONS

Our data do not support substantial benefit of preoperative embolization for patients with a favorable surgical risk profile. Because of risks and costs with this intervention, the prudent use of preoperative embolization should be individually considered.

Biological relevance of tissue factor and IL-6 in arteriovenous malformations

Arteriovenous malformations (AVMs) are congenital abnormal vessels that shunt blood directly from the arterial to the venous system without a capillary bed. The underlying pathology of AVMs is not fully understood. The objective of the study was to determine the association between the expression patterns of tissue factor (TF) and interleukin-6 (IL-6) in AVMs with clinical and pathological findings. Eighteen cases of sporadic AVM with operative specimens were included in this study. The expression of messenger RNA (mRNA) of TF and IL-6 was assayed, and association with clinical factors was investigated. The distribution of TF and IL-6 was examined with immunofluorescence. The mRNA expression of TF was significantly higher in AVM specimens than in control tissues (P = 0.002) and significantly higher in the symptomatic group than in the asymptomatic group (P = 0.037). The mRNA expression of IL-6 was likewise significantly higher in AVM specimens than in control tissues (P = 0.038). Examination of immunostained sections indicated that TF⁺ cells were also positive for IL-6 and were distributed around normal endothelial cells and pericytes. Moreover, TF⁺/IL-6⁺ cells also expressed CD31, vascular endothelial growth factor receptor 2 (VEGFR2), and platelet-derived growth factor receptor beta (PDGFR-beta). These results suggest that TF is elevated in AVMs and that it mediates symptomatic events. IL-6 is associated with the angiogenic activity of TF, and both are present in the same abnormal endothelial cells and pericytes. These factors may have interactive effects and may serve in a prognostic role for AVMs.

Moyamoya disease associated with arteriovenous malformation and anterior communicating artery aneurysm: A case report and literature review

Moyamoya disease (MMD) can be associated with an aneurysm or arteriovenous malformation (AVM). However, no case of MMD simultaneously associated with both intracranial aneurysm and AVM has been previously reported. The present study reports the case of a patient with MMD simultaneously associated with both aneurysm and AVM. The patient was a 46-year-old woman presenting with a subarachnoid hemorrhage whose imaging diagnosis of MMD was associated with an aneurysm and AVM. The aneurysm was located in the anterior communicating artery, which was similar to a berry aneurysm caused by hemodynamics. The AVM was located in the posterior circulation. Beyond the presentation of the posterior cerebral artery, the appearance of an artery supplying blood from the middle cerebral artery supported the view that the AVM was congenital and unruptured. Conservative treatment was provided and examination of the patient at follow-up showed good recovery. In addition to the case report, the present study also reviewed the relevant literature in order to compile information on MMD associated with both an aneurysm and AVM.

Hemorrhage Risk in Pediatric Patients with Multiple Intracranial Arteriovenous Malformations

BACKGROUND/AIMS

This study aims to characterize the clinical features, treatment strategies, and annual hemorrhage incidence rate of pediatric patients with multiple arteriovenous malformations (MAVM).

METHODS

The PubMed and EMBASE databases and the arteriovenous malformations (AVM) database at the Johns Hopkins Hospital were searched for reports of pediatric patients (under 21 years of age) with MAVM. Data related to demographics, clinical features, management, and treatment outcomes were analyzed using descriptive statistics. Twenty-four pediatric patients met the inclusion criteria.

RESULTS

The annual hemorrhage incidence rate was 2.1%. The most common presenting features were neurological deficit (38%) and hemorrhage (21%). Treatment with embolization has become the most frequently used modality. In patients undergoing staged treatment of MAVM, hemorrhage of an untreated nidus (n = 1), visualization of a new nidus (n = 2), or disappearance of a draining vein (n = 1) occurred.

CONCLUSION

The annual hemorrhage incidence rate for pediatric patients with MAVM approaches the upper range of previously reported hemorrhage rates for solitary AVM. A staged approach to treating MAVM requires close follow-up as changes to the remaining nidi may occur during the latency period. Limitations of this study include its small sample size and reporting bias.

Endovascular treatment of arteriovenous malformations

Cerebral arteriovenous malformations (AVM) are tangles of blood vessels that permit shunting of blood from the arterial to venous phase without intervening capillaries. The malformation's arterialization of a low-pressure system creates a risk of rupture that is substantially higher when associated with an aneurysm. The annual hemorrhage rate is 2.2% per year as reported in the randomized trial of unruptured brain AVMs (ARUBA; rupture risk is increased after the first event. Ruptured AVMs have a 10% mortality rate and 20%-30% morbidity rate. The treatment of choice for AVMs is microvascular resection with or without preoperative embolization. Surgical risk can be stratified based on the Spetzler-Martin grading system. Liquid embolic material and coils may be used for the treatment of AVM associated aneurysms, especially in the setting of acute rupture as a bridge to delayed surgical resection. There is some limited reported success in total endovascular treatment of AVMs, but this is not considered standard therapy at this time. Stereotactic radiosurgery (SRS) has been recently described but mainly limited to AMVs deemed too risky to approach in an open fashion and limited to 2.5cm-3cm in size. The delayed protection from hemorrhage (approximately 2-3 years) and high marginal failure/recurrence rate are the greatest concerns.

Animal Models in Studying Cerebral Arteriovenous Malformation

Brain arteriovenous malformation (AVM) is an important cause of hemorrhagic stroke. The etiology is largely unknown and the therapeutics are controversial. A review of AVM-associated animal models may be helpful in order to understand the up-to-date knowledge and promote further research about the disease. We searched PubMed till December 31, 2014, with the term “arteriovenous malformation,” limiting results to animals and English language. Publications that described creations of AVM animal models or investigated AVM-related mechanisms and treatments using these models were reviewed. More than 100 articles fulfilling our inclusion criteria were identified, and from them eight different types of the original models were summarized. The backgrounds and procedures of these models, their applications, and research findings were demonstrated. Animal models are useful in studying the pathogenesis of AVM formation, growth, and rupture, as well as in developing and testing new treatments. Creations of preferable models are expected.

Hemorrhage risk and clinical features of multiple intracranial arteriovenous malformations

The aim of this report is to examine clinical characteristics, treatment strategies, and annual hemorrhage incidence rate for patients with multiple arteriovenous malformations (MAVM). The PubMed and EMBASE databases and the arteriovenous malformations (AVM) database at The Johns Hopkins Hospital were searched to identify patients with MAVM. Data related to demographics, clinical features, management, and treatment outcomes were analyzed with descriptive statistics. Thirty-eight patients met the inclusion criteria. The annual hemorrhage incidence rate was 6.7%. Surgical intervention remained the most common single-modality treatment from 1949-2011. Between 1990 and 2011, multiple-modality treatment strategies (36% of cases) were employed more frequently. The most common presenting features were neurological deficit (74%) and hemorrhage (63%). In patients undergoing staged treatment of MAVM, hemorrhage of an untreated nidus (n=5), visualization of a new nidus (n=9), and disappearance of an untreated nidus (n=2) were observed. Limitations of this study include small sample size and reporting bias. The annual hemorrhage incidence rate for MAVM patients was approximately two- to three-fold greater than the reported annual hemorrhage rates for solitary AVM. Combining different treatment modalities has become the most common management strategy. The potential instability of remaining nidi with staged or incomplete treatment necessitates close follow-up in these cases.

Molecular and cellular biology of cerebral arteriovenous malformations: a review of current concepts and future trends in treatment

OBJECT

Arteriovenous malformations (AVMs) are classically described as congenital static lesions. However, in addition to rupturing, AVMs can undergo growth, remodeling, and regression. These phenomena are directly related to cellular, molecular, and physiological processes. Understanding these relationships is essential to direct future diagnostic and therapeutic strategies. The authors performed a search of the contemporary literature to review current information regarding the molecular and cellular biology of AVMs and how this biology will impact their potential future management.

METHODS

A PubMed search was performed using the key words "genetic," "molecular," "brain," "cerebral," "arteriovenous," "malformation," "rupture," "management," "embolization," and "radiosurgery." Only English-language papers were considered. The reference lists of all papers selected for full-text assessment were reviewed.

RESULTS

Current concepts in genetic polymorphisms, growth factors, angiopoietins, apoptosis, endothelial cells, pathophysiology, clinical syndromes, medical treatment (including tetracycline and microRNA-18a), radiation therapy, endovascular embolization, and surgical treatment as they apply to AVMs are discussed.

CONCLUSIONS

Understanding the complex cellular biology, physiology, hemodynamics, and flow-related phenomena of AVMs is critical for defining and predicting their behavior, developing novel drug treatments, and improving endovascular and surgical therapies.

Intraoperative Ultrasonography Combined with Indocyanine Green Video-Angiography in Patients with Cerebral Arteriovenous Malformations

BACKGROUND AND PURPOSE

During the operation, accurately identifying the boundary of cerebral arteriovenous malformation (AVM) and discriminating between feeding arteries and draining veins is the key to successful surgical treatment of cerebral AVM. We evaluated the application of intraoperative ultrasonography (IOU) combined with intraoperative indocyanine green video-angiography (IOICGA) in the patients with cerebral AVM.

METHODS

The effects of IOU combined with IOICGA on AVM surgery were observed in 12 patients with cerebral AVM.

RESULTS

The lesions of cerebral AVM were completely removed in the 12 patients. IOU could clearly visualize the boundary of AVM, so no patients had massive hemorrhage caused by rupture of malformed vessels. IOU also could detect the location of deep vessels and a total of 11 deep vessels were identified in the 12 patients. IOICGA was performed 41 times altogether in the 12 patients, and 31 feeding arteries and 10 draining veins were identified, so there was no massive hemorrhage caused by misjudgment of feeding arteries or draining veins.

CONCLUSIONS

IOU combined with IOICGA can identify the boundary of AVM, detect deep vessels, and discriminate between feeding arteries and draining veins, reducing operation difficulty, decreasing mortality and disability rate, and increasing the rate of complete excision.

Biology of cerebral arteriovenous malformations with a focus on inflammation

Cerebral arteriovenous malformations (AVMs) entail a significant risk of intracerebral hemorrhage owing to the direct shunting of arterial blood into the venous vasculature without the dissipation of the arterial blood pressure. The mechanisms involved in the growth, progression and rupture of AVMs are not clearly understood, but a number of studies point to inflammation as a major contributor to their pathogenesis. The upregulation of proinflammatory cytokines induces the overexpression of cell adhesion molecules in AVM endothelial cells, resulting in enhanced recruitment of leukocytes. The increased leukocyte-derived release of metalloproteinase-9 is known to damage AVM walls and lead to rupture. Inflammation is also involved in altering the AVM angioarchitecture via the upregulation of angiogenic factors that affect endothelial cell proliferation, migration and apoptosis. The effects of inflammation on AVM pathogenesis are potentiated by certain single-nucleotide polymorphisms in the genes of proinflammatory cytokines, increasing their protein levels in the AVM tissue. Furthermore, studies on metalloproteinase-9 inhibitors and on the involvement of Notch signaling in AVMs provide promising data for a potential basis for pharmacological treatment of AVMs. Potential therapeutic targets and areas requiring further investigation are highlighted.

Value of 4D MR angiography at 3T compared with DSA for the follow-up of treated brain arteriovenous malformation

BACKGROUND AND PURPOSE

Four-dimensional, contrast-enhanced MRA is a useful technique for the diagnosis and classification of brain AVM. The purpose of this study was to evaluate its usefulness in the follow-up of treated brain AVM.

MATERIALS AND METHODS

Patients with treated brain AVM (embolization, radiosurgery, and/or surgery) were investigated with both DSA (the "gold standard") and 4D MRA. Four-dimensional MRA was performed at 3T using a 4D sequence, combining contrast-enhanced timing-robust angiography, keyhole, and sensitivity encoding techniques. Examinations were evaluated by 2 independent readers and disagreements were resolved by a third reader. Interobserver and intermodality agreement with respect to residual nidus, residual venous drainage, and brain AVM patency were determined.

RESULTS

Between May 2008 and February 2013, 37 patients with a median age of 45 years (interquartile range = 26-55) were prospectively included. Examinations were acquired 36 months (IQR = 10-45.5) after the last treatment. Interobserver agreement for brain AVM patency was very good for both 4D MRA (κ 0.82, 95% CI .67-.98) and DSA (κ 0.84, 95% CI .69-.98). After consensus reading, intermodality agreement for the evaluation of brain AVM patency was good (κ 0.73, 95% CI .55-.90). Diagnostic accuracy of 4D MRA for residual brain AVM compared with DSA, reached a sensitivity of 73.7%, specificity 100%, positive predictive value 100%, and negative predictive value 78.3%. Agreements by technique of treatment are also detailed.

CONCLUSIONS

Four-dimensional MRA is a useful radiation-free technique for the follow-up of patients with treated brain AVM, especially patients treated by radiosurgery. However, given its actual limitations it is not sufficient to assert the cure; DSA remains mandatory for this purpose.