Clinical practice. Arteriovenous malformations of the brain

Systematic screening in hereditary hemorrhagic telangiectasia: a review

PURPOSE OF REVIEW

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant inherited disease characterized by telangiectasia and arteriovenous malformations (AVMs). To date, five genetic types of HHT and one combined juvenile polyposis syndrome and HHT are known. Clinical and genetic screening of patients suspected with HHT is recommended to confirm the diagnosis and to prevent complications associated with HHT. The aim of this article is to give an overview of the evidence and to formulate a recommendation for clinicians concerning screening for HHT.

RECENT FINDINGS

Complications of HHT such as stroke, brain abscess and intracranial hemorrhage are caused by pulmonary and cerebral AVMs (CAVMs) and can often be prevented by screening and treatment when possible. Screening and treatment of these AVMs will result in an increased life expectancy comparable with that of the general population as opposed to unscreened and untreated HHT patients.

SUMMARY

Screening of HHT patients and their first-degree relatives is recommended to prevent severe complications including stroke, brain abscess and intracranial hemorrhage.

Single-stage planning for total cure of grade III-V brain arteriovenous malformations by embolization alone or in combination with microsurgical resection

PURPOSE

There are no established guidelines for treatment of Spetzler-Martin grade III-V brain arteriovenous malformations (bAVMs). The purpose of this study is to report our institutional experience in total obliteration/eradication of grade III-V bAVMs by single-stage planning of embolization combined with microsurgical resection when necessary.

METHODS

All patients harboring Spetzler-Martin (S-M) grade III-V bAVMs treated with single-stage planning between January 2006 and January 2018 were retrospectively reviewed. This treatment paradigm is applicable only to surgically accessible bAVMs and does not include deep-seated bAVMs. Indications for treatment, clinical presentation, imaging characteristics, and treatment outcomes were analyzed. Outcomes were assessed based on modified Rankin Scale.

RESULTS

A total of 31 patients were identified. Seventeen patients (54.8%) presented with hemorrhage, 10 (32.3%) with seizures, 3 (9.7%) with headaches, and 1 (3.2%) with progressive neurological deficit. Based on S-M grading system, 25 patients (80.6%) harbored grade III bAVM, 5 patients had grade IV bAVMs (16.1%), and 1 patient (3.2%) had a grade V bAVM. There were no treatment-related complications in 24/31 (77.4%) patients. Of the total of seven patients with complications, four patients had clinical deterioration. The long-term (> 6-month), non-disabling morbidity (mRS ≤ 2) rate was 6.5%. The long-term, disabling morbidity rate was 3.2% with a mortality of 3.2%. Complete angiographic obliteration was achieved in 30/31 (96.8%) patients.

CONCLUSION

Single-stage treatment strategy can be considered as an alternative to multistage embolization prior to surgery in grade III-V bAVMs. In this study, a high rate of total obliteration with relatively low rates of permanent morbidity and mortality was achieved.

Microsurgical resection of brain arteriovenous malformations in the elderly: outcomes analysis and risk stratification

As the population ages, the question of how to manage brain arteriovenous malformations in the elderly becomes increasingly relevant. Is resection a reasonable option for these patients? In this study, the authors examined the outcomes of surgical patients 60 years or older and found that favorable outcomes were achieved with careful patient selection. Preoperative grading scales were more predictive of outcomes in patients older than 65 years than in those 60-65 years of age.

Cerebral Arteriovenous Malformation Associated with a Cyst

An 11-year-old child presented with chronic occipital headache and vomiting. Computed tomography (CT) scan revealed a cystic mass lesion in the right occipital region. Magnetic resonance imaging brain revealed a cystic mass lesion which was hypointense on T1-weighted images and hyperintense on T2-weighted images. A mural nodule was noted in the inferolateral wall of the lesion. CT angiography revealed small arteriovenous malformations (AVM) related to the lesion. The AVM associated with the cyst was excised. The patient recovered well. Cystic AVM is a rare vascular lesion, and only five such cases have been reported in the past. AVMs should be considered in the differential diagnosis of cystic lesions of the brain, especially when associated with a mural nodule.

Recurrent periventricular hemorrhage in cerebral proliferative angiopathy: Case report

Cerebral proliferative angiopathy (CPA) is a rare vascular lesion. Bleeding from CPA is uncommon, but the risk of rebleeding is high once it bleeds. We describe a case of CPA with multiple intra- and periventricular hemorrhages during 30-year follow-up. Recurrent bleeding in these areas are common in moyamoya disease. These lesions may share the cause of bleeding: proliferation of the periventricular vessels functioning as collateral pathways. Revascularization surgery for CPA may attenuate the vascular proliferation in the vicinity of the ventricle, which may prevent rebleeding.

Imaging artifacts of Onyx and PHIL on conventional CT, cone-beam CT and MRI in an animal model

BACKGROUND AND PURPOSE

A frequently reported drawback of ethylene vinyl alcohol copolymer-based liquid embolic agents is the production of artifacts in diagnostic imaging. New embolic agents, such as Precipitating hydrophobic injectable liquid (PHIL; MicroVention, Tustin, CA, USA), are supposed to induce significantly fewer artifacts. The purpose of this study is to assess the degree of artifacts induced by the liquid embolic agents Onyx (Medtronic Neurovascular, Irvine, CA, USA) and PHIL in conventional computed tomography (CT), cone-beam CT and magnetic resonance imaging (MRI) in an experimental in vivo model.

MATERIALS AND METHODS

In 10 pigs the rete mirabile was embolized with Onyx ( n = 5) or PHIL ( n = 5). After embolization, conventional CT, cone-beam CT and MRI were performed. The degree of artifacts was graded qualitatively (five-point scale; for CT and MRI) and quantitatively (HUs of well-defined regions of interest (ROIs); for CT only).

RESULTS

Artifacts were significantly more severe for Onyx both in the qualitative (e.g. conventional CT: 2 versus 5 (medians); p = 0.008) and in the quantitative image analysis (e.g. cone-beam CT: standard deviation of a ROI near to the embolic agent cast, 94 HU versus 38 HU (medians); p = 0.008). Neither Onyx nor PHIL produced any apparent artifacts in MRI.

CONCLUSION

PHIL produces fewer artifacts than Onyx in conventional CT and cone-beam CT in an experimental in vivo model.

Modern robot-assisted radiosurgery of cerebral angiomas-own experiences, system comparisons, and comprehensive literature overview

Cerebral arteriovenous malformations (AVMs) are rare vascular lesions potentially responsible for substantial neurological morbidity and mortality. Over the past four decades, radiosurgery has become a valid therapeutic option for many patients with small intracranial AVMs, but reports describing the use of robotic stereotactic radiosurgery (SRS) are rare. The purposes of this study are to describe the efficacy and toxicity of robotic SRS for AVMs and to review the literature. The reports of 48 consecutive patients treated with SRS were reviewed. A total dose of 18 Gy in a single fraction was prescribed to the 70% isodose line. Efficacy (i.e., total obliteration of the AVM) and toxicity were analyzed. Literature search was performed on Embase and PubMed for the terms "Radiosurgery and AVMs", "Cyberknife and AVMs" and "Radiation therapy and AVMs." The median follow-up was 41 months. The median AVM volume was 2.62 cm³. The incidence of obliteration was 59% at 3 years. Regarding toxicity, 92% of patients remained symptom-free, 66% developed radiogenic edema on MRI, and none developed radionecrosis. Forty-one patients (85%) had embolization prior to SRS. Our study was incorporated in an exhaustive review of 25 trials categorized by SRS technique. In this review, the median follow-up was 60 months. The median nidus volume was 2 cm³. The median overall obliteration rate for SRS was 68% (range 36 to 92). The median embolization rate prior to SRS was 31% (range 8.23 to 90). Compared to other studies, tolerability was excellent and the obliteration rate was acceptable but probably affected by the high embolization rate prior to radiosurgery. Our study suggests that a higher dose is feasible. A larger cohort with a longer follow-up period will be needed to confirm the safety and effectiveness, and subsequently validate different prognosis and predictive scores with this treatment modality to maximize the benefits of this technology for selected patients in the long term.

A novel non-contrast-enhanced MRA using silent scan for evaluation of brain arteriovenous malformation: A case report and review of literature

RATIONALE

Brain arteriovenous malformations (AVMs) are congenital vascular abnormalities involving abnormal connections between arteries and veins. In clinical practice, imaging studies help evaluate feeding arteries, niduses, draining venous systems, and coexisting complications in patients with brain AVM. They also have an impact on decision-making regarding clinical management. We applied a novel non-contrast-enhanced MR angiography (MRA) technique, termed "silent MRA," for evaluating an incidental brain AVM. Here, we describe the clinical case with radiological review and highlight the technical background and clinical usefulness of silent MRA.

PATIENT CONCERNS

A 60-year-old woman underwent neuroimaging study including MRA to evaluate intracranial cause of headache.

DIAGNOSES

The brain AVM, including its nidus and draining veins, was conspicuously delineated on silent MRA images; these findings correlated well with conventional angiographic findings.

INTERVENTIONS

The patient did not receive interventional or surgical treatment.

OUTCOMES

The patient is being followed up regularly at the outpatient department.

LESSONS

The silent MRA can be a suitable imaging modality for repeated follow-up evaluation for not only brain AVMs but also various intracranial vascular diseases without the use of contrast materials.

Linking Brain Arteriovenous Malformations With Anorectal Hemorrhoids: A Clinical and Anatomical Review

Patients who harbor brain arteriovenous malformations are at risk for intracranial hemorrhage. These malformations are often seen in inherited vascular diseases such as hereditary hemorrhagic telangiectasia. However, malformations within the brain also sporadically occur without a hereditary-coding component. Here, we review recent insights into the pathophysiology of arteriovenous malformations, in particular, certain signaling pathways that might underlie endothelial cell pathology. To better interpret the origins, determinants and consequences of brain arteriovenous malformations, we present a clinical case to illustrate the phenotypic landscape of the disease. We also propose that brain arteriovenous malformations might share certain signaling dimensions with those of anorectal hemorrhoids. This working hypothesis provides casual anchors from which to understand vascular diseases characterized by arteriovenous lesions with a hemorrhagic- or bleeding-risk component. Anat Rec, 2017. © The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists. Anat Rec, 300:1973-1980, 2017. © 2017 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Extravasation of contrast (Spot Sign) predicts in-hospital mortality in ruptured arteriovenous malformation

BACKGROUND AND PURPOSE

The spot sign is a highly specific and sensitive predictor of hematoma expansion in following primary intracerebral hemorrhage (ICH). Rare cases of the spot sign have been documented in patients with intracranial hemorrhage secondary to arteriovenous malformation (AVM). The purpose of this retrospective study is to assess the accuracy of spot sign in predicting clinical outcomes in patients with ruptured AVM.

MATERIALS AND METHODS

A retrospective analysis of a prospectively maintained database was performed for patients who presented to West China Hospital with ICH secondary to AVM in the period between January 2009 and September 2016. Two radiologists blinded to the clinical data independently assessed the imaging data, including the presence of spot sign. Statistical analysis using univariate testing, multivariate logistic regression testing, and receiver operating characteristic curve (AUC) analysis was performed.

RESULTS

A total of 116 patients were included. Overall, 18.9% (22/116) of subjects had at least 1 spot sign detected by CT angiography, 7% (8/116) died in hospital, and 27% (31/116) of the patients had a poor outcome after 90 days. The spot sign had a sensitivity of 62.5% and specificity of 84.3% for predicting in-hospital mortality (p = .02, AUC 0.734). No correlation detected between the spot sign and 90-day outcomes under multiple logistic regression (p = .19).

CONCLUSIONS

The spot sign is an independent predictor for in-hospital mortality. The presence of spot sign did not correlate with the 90 day outcomes in this patient cohort. The results of this report suggest that patients with ruptured AVM with demonstrated the spot sign on imaging must receive aggressive treatment early on due to the high risk of mortality.

Relative risk of hemorrhage during pregnancy in patients with brain arteriovenous malformations

Background It is unclear whether the risk of bleeding from brain arteriovenous malformations is higher during pregnancy, delivery, or puerperium. We compared occurrence of brain arteriovenous malformation hemorrhage in women during this period with occurrence of hemorrhage outside this period during their fertile years. Methods We included all women with ruptured brain arteriovenous malformations (16-41 years) from a retrospective database of patients with brain arteriovenous malformations in four Dutch university hospitals (n = 95) and from the population-based Scottish Audit of Intracranial Vascular Malformations (n = 44). We estimated the relative rate of brain arteriovenous malformation rupture (before any treatment) during exposed time (pregnancy, delivery, puerperium) versus non-exposed time during fertile years, using the case-crossover design as primary analysis, and the self-controlled case-series design as secondary analysis. Results In 17 of 95 Dutch women and in 3 of 44 Scottish women, hemorrhages occurred while pregnant; none occurred during delivery or puerperium. In Dutch women, the relative rate of brain arteriovenous malformation rupture during pregnancy, delivery, or puerperium was 6.8 (95% confidence interval 3.6-13) according to the case-crossover method and 7.1 (95% confidence interval 3.4-13) using the self-controlled case-series method. In Scottish women, the relative rate was 1.3 (95% confidence interval 0.39-4.1) using the case-crossover method and 1.7 (95% confidence interval 0.0-4.4) according to the self-controlled case-series method. Because of limited overlap of confidence intervals, we refrained from pooling the cohorts. Conclusions Case-crossover and self-controlled case series analyses reveal an increase in relative rate of brain arteriovenous malformation rupture during pregnancy in the Dutch cohort but not in the Scottish cohort. Since point estimates varied between both cohorts and numbers are relatively small, the clinical implications of our findings are uncertain.

Clinical Outcomes and Prognostic Factors for Spontaneous Intracerebral Hemorrhage in Pediatric ICU: A 12-Year Experience

BACKGROUND

In the pediatric population, spontaneous intracerebral hemorrhage (sICH) is as common as ischemic stroke and accounts for significant mortality and morbidity. Differently from the ischemic stroke, there are few guidelines for directing management of sICH. This article aims to analyze both clinical outcomes and prognostic factors in order to produce tools for the design of prospective randomized studies addressed to implement treatment of pediatric sICH.

METHODS

Twelve-year retrospective review of a single-center consecutivesICH pediatric cases admitted to the pediatric intensive care unit (PICU). Selected end points were survival, PICU stay, and dichotomized Glasgow Outcome Score (GOS), with recovery and moderate disability (GOS 4-5) classified as favorable outcome and vegetative state or severe disability (GOS 2-3) classified as unfavorable.

RESULTS

Data of 107 children younger than 14 years admitted to our PICU due to sICH were analyzed. Overall PICU mortality was 24.2%. On multivariate analysis, the single factor markedly influencing survival was the presence of midline shift (P = .002). In PICU survivors, there were 42 GOS 2-3 and 39 GOS 4-5. A low Glasgow Coma Scale (GCS) on PICU admission was predictive of severe neurological impairment in survivors (P = .003). Intraventricular hemorrhage and infratentorial origin did not influence outcome in this series.

CONCLUSION

The severity of presentation of sICH expressed by the midline shift and the GCS at PICU admission are significant prognostic factors for survival and neurological outcome. Some prognostic factors of the adult population have not been confirmed.

Evaluation of a novel liquid embolic agent (precipitating hydrophobic injectable liquid (PHIL)) in an animal endovascular embolization model

BACKGROUND

The choice of the embolic agent and the embolization technique can have a significant impact on the success of endovascular embolization.

OBJECTIVE

To evaluate a novel iodinated copolymer-based liquid embolic agent (precipitating hydrophobic injectable liquid (PHIL)) in the porcine rete mirabile (RM), serving as an endovascular embolization model. Onyx, as an established liquid embolic agent, served as comparator.

MATERIALS AND METHODS

Sixteen embolization procedures were performed using PHIL (n=8) or Onyx (n=8) as liquid embolic agent. Waiting time between injections was set to 30 or 60 s (n=4 per study group). Survival time after intervention was 2 hours or 7 days. Embolization characteristics (eg, procedure times, number of injections and volume of embolic agent) and embolization extent (percentage of embolized RM in post-interventional x-ray) were assessed. Post-interventional CT and histopathological analyses were performed.

RESULTS

Embolization characteristics and embolization extent were not significantly different for PHIL and Onyx, including subgroups (eg, embolization extent 44% vs 69% (medians); p=0.101). For PHIL, extension of the waiting time from 30 to 60 s led to a significantly higher embolization extent (24% vs 72% (medians); p=0.035). Moderate disintegration and mild inflammation of the embolized blood vessels were present for both embolic agents.

CONCLUSION

PHIL is feasible for transarterial embolization in an acute and subacute endovascular embolization model. In this preliminary experimental in vivo study, embolization characteristics, embolization extent, and biocompatibility seem to be similar to those of Onyx.

Delayed treatment of ruptured brain AVMs: is it ok to wait?

OBJECTIVE Despite a hemorrhagic presentation, many patients with arteriovenous malformations (AVMs) do not require emergency resection. The timing of definitive management is not standardized in the cerebrovascular community. This study was designed to evaluate the safety of delaying AVM treatment in clinically stable patients with a new hemorrhagic presentation. The authors examined the rate of rehemorrhage or neurological decline in a cohort of patients with ruptured brain AVMs during a period of time posthemorrhage. METHODS Patients presenting to the authors' institution from January 2000 to December 2015 with ruptured brain AVMs treated at least 4 weeks posthemorrhage were included in this analysis. Exclusion criteria were ruptured AVMs that required emergency surgery involving resection of the AVM, prior treatment of AVM at another institution, or treatment of lesions within 4 weeks for other reasons (subacute surgery). The primary outcome measure was time from initial hemorrhage to treatment failure (defined as rehemorrhage or neurological decline as a direct result of the AVM). Patient-days were calculated from the day of initial rupture until the day AVM treatment was initiated or treatment failed. RESULTS Of 102 ruptured AVMs in 102 patients meeting inclusion criteria, 7 (6.9%) failed the treatment paradigm. Six patients (5.8%) had a new hemorrhage within a median of 248 days (interquartile range 33-1364 days). The total "at risk" period was 18,740 patient-days, yielding a rehemorrhage rate of 11.5% per patient-year, or 0.96% per patient-month. Twelve (11.8%) of 102 patients were found to have an associated aneurysm. In this group there was a single (8.3%) new hemorrhage during a total at-risk period of 263 patient-days until the aneurysm was secured, yielding a rehemorrhage risk of 11.4% per patient-month. CONCLUSIONS It is the authors' practice to rehabilitate patients after brain AVM rupture with a plan for elective treatment of the AVM. The present data are useful in that the findings quantify the risk of the authors' treatment strategy. These findings indicate that delaying intervention for at least 4 weeks after the initial hemorrhage subjects the patient to a low (< 1%) risk of rehemorrhage. The authors modified the treatment paradigm when a high-risk feature, such as an associated intracranial aneurysm, was identified.

Liquid Embolic Agents for Endovascular Embolization: Evaluation of an Established (Onyx) and a Novel (PHIL) Embolic Agent in an In Vitro AVM Model

BACKGROUND AND PURPOSE

Embolization plays a key role in the treatment of arteriovenous malformations. The aim of this study was to evaluate an established (Onyx) and a novel (precipitating hydrophobic injectable liquid [PHIL]) liquid embolic agent in an in vitro AVM model.

MATERIALS AND METHODS

An AVM model was integrated into a circuit system. The artificial nidus (subdivided into 28 honeycomb-like sections) was embolized with Onyx 18 (group Onyx; n = 8) or PHIL 25 (group PHIL; n = 8) with different pause times between the injections (30 and 60 seconds, n = 4 per study group) by using a 1.3F microcatheter. Procedure times, number of injections, embolization success (defined as the number of filled sections of the artificial nidus), volume of embolic agent, and frequency and extent of reflux and draining vein embolization were assessed.

RESULTS

Embolization success was comparable between Onyx and PHIL. Shorter pause times resulted in a significantly higher embolization success for PHIL (median embolization score, 28 versus 18; P = .011). Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization (median volume per section of the artificial nidus, 15.5 versus 3.6 μL; P < .001).

CONCLUSIONS

While the embolization success was comparable for Onyx and PHIL, pause time had a considerable effect on the embolization success in an in vitro AVM model. Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization.

Identification of protein targets in cerebral endothelial cells for brain arteriovenous malformation (AVMs) molecular therapies

Background

To develop a new molecular targeted treatment for brain (AVMs), identification of membrane proteins that are localised on the AVM endothelium is crucial. Current treatment methods are surgery and radiosurgery. However, complete occlusion post radiosurgery are achieved within 3 years, while patient remain at risk of haemorrhage. This study aims to identify potential protein targets in AVM endothelial cells that discriminate these vessels from normal vessels; these proteins targets will be investigated for the molecular therapy of brain AVMs to promote rapid thrombosis after radiosurgery.

Methods

We employed in vitro biotinylation that we developed, and mass spectrometry to detect cell surface-exposed proteins in cultures of murine cerebral endothelial cells (bEnd.3). Two forms of mass spectrometry were applied (iTRAQ-MS and MS^E) to identify and quantify membrane protein expression at various time-points following irradiation which simulates a radiosurgical treatment approach. Immunocytochemistry was used to confirm the expression of selected membrane proteins. ProteinPilot V4.0 software was used to analyse the iTRAQ-MS data and the MS^E data was analysed using ProteinLynx Global Server version 2.5 software.

Results

The proteomics data revealed several differentially expressed membrane proteins between irradiated and non-irradiated cells at specific time points, e.g. PECAM-1, cadherin-5, PDI, EPCR and integrins. Immunocytochemistry data confirmed the expression of these proteins.

Conclusion

Cell surface protein biotinylation and proteomics analysis successfully identified membrane proteins from murine brain endothelial cells in response to irradiation. This work suggests potential target protein molecules for evaluation in animal models of brain-AVM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-017-9151-3) contains supplementary material, which is available to authorized users.

Imaging of Intracranial Hemorrhage

Intracranial hemorrhage is common and is caused by diverse pathology, including trauma, hypertension, cerebral amyloid angiopathy, hemorrhagic conversion of ischemic infarction, cerebral aneurysms, cerebral arteriovenous malformations, dural arteriovenous fistula, vasculitis, and venous sinus thrombosis, among other causes. Neuroimaging is essential for the treating physician to identify the cause of hemorrhage and to understand the location and severity of hemorrhage, the risk of impending cerebral injury, and to guide often emergent patient treatment. We review CT and MRI evaluation of intracranial hemorrhage with the goal of providing a broad overview of the diverse causes and varied appearances of intracranial hemorrhage.

Subsequent haemorrhage in children with untreated brain arteriovenous malformation: Higher risk with unbalanced inflow and outflow angioarchitecture

OBJECTIVES

Children with brain arteriovenous malformations (bAVMs) are at risk of life-threatening haemorrhage in their early lives. Our aim was to analyse various angioarchitectural features of bAVM to predict the risk of subsequent haemorrhage during follow-up in children.

METHODS

We identified all consecutive children admitted to our institution for bAVMs between July 2009 and September 2015. Children with at least 1 month of treatment-free follow-up after diagnosis were included in further analysis. Annual rates of AVM rupture as well as several potential risk factors for subsequent haemorrhage were analysed using Kaplan-Meier analyses and Cox proportional hazards regression models.

RESULTS

We identified 110 paediatric patients with a mean follow-up period of 2.1 years (range, 1 month-15.4 years). The average annual risk of haemorrhage from untreated AVMs was 4.3 % in children. No generalised venous ectasia in conjunction with fast arteriovenous shunt was predictive of subsequent haemorrhage (RR, 7.55; 95 % CI 1.96-29.06). The annual rupture risk was 11.1 % in bAVMs without generalised venous ectasia but with fast arteriovenous shunt.

CONCLUSIONS

bAVM angiographic features suggesting unbalanced inflow and outflow might be helpful to identify children at higher risk for future haemorrhage.

KEY POINTS

• Haemorrhage risk stratification is important for children with untreated brain AVM. • Angiographic features suggesting unbalanced inflow and outflow predict paediatric brain AVM haemorrhage. • Identifying AVMs with high rupture risk help patient selection and tailoring treatment.

Integrin β8 Deletion Enhances Vascular Dysplasia and Hemorrhage in the Brain of Adult Alk1 Heterozygous Mice

Brain arteriovenous malformation (bAVM), characterized by tangled dysplastic vessels, is an important cause of intracranial hemorrhage in young adults, and its pathogenesis and progression are not fully understood. Patients with haploinsufficiency of transforming growth factor-β (TGF-β) receptors, activin receptor-like kinase 1 (ALK1) or endoglin (ENG) have a higher incidence of bAVM than the general population. However, bAVM does not develop effectively in mice with the same haploinsufficiency. The expression of integrin β8 subunit (ITGB8), another member in the TGF-β superfamily, is reduced in sporadic human bAVM. Brain angiogenic stimulation results at the capillary level of vascular malformation in adult Alk1 haploinsufficient (Alk1 ^+/- ) mice. We hypothesized that deletion of Itgb8 enhances bAVM development in adult Alk1 ^+/- mice. An adenoviral vector expressing Cre recombinase (Ad-Cre) was co-injected with an adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF) into the brain of Alk1 ^+/-;Itgb8-floxed mice to induce focal Itgb8 gene deletion and angiogenesis. We showed that compared with Alk ^+/- mice (4.75 ± 1.38/mm²), the Alk1 ^+/-;Itgb8-deficient mice had more dysplastic vessels in the angiogenic foci (7.14 ± 0.68/mm², P = 0.003). More severe hemorrhage was associated with dysplastic vessels in the brain of Itgb8-deleted Alk1 ^+/- , as evidenced by larger Prussian blue-positive areas (1278 ± 373 pixels/mm² vs. Alk1 ^+/-  : 320 ± 104 pixels/mm²; P = 0.028). These data indicate that both Itgb8 and Alk1 are important in maintaining normal cerebral angiogenesis in response to VEGF. Itgb8 deficiency enhances the formation of dysplastic vessels and hemorrhage in Alk1 ^+/- mice.

Endothelial fluid shear stress sensing in vascular health and disease

Endothelial cells transduce the frictional force from blood flow (fluid shear stress) into biochemical signals that regulate gene expression and cell behavior via specialized mechanisms and pathways. These pathways shape the vascular system during development and during postnatal and adult life to optimize flow to tissues. The same pathways also contribute to atherosclerosis and vascular malformations. This Review covers recent advances in basic mechanisms of flow signaling and the involvement of these mechanisms in vascular physiology, remodeling, and these diseases. We propose that flow sensing pathways that govern normal morphogenesis can contribute to disease under pathological conditions or can be altered to induce disease. Viewing atherosclerosis and vascular malformations as instances of pathological morphogenesis provides a unifying perspective that may aid in developing new therapies.

Cerebrovascular disease

With 16.9 million people who suffered a first-ever stroke in 2010 worldwide, stroke is a very common vascular disease. Epidemiologic studies have played an essential role in assessing this burden and in detecting the risk factors for stroke. Primary prevention of these risk factors, primarily hypertension, smoking, diabetes, and atrial fibrillation, has reduced the incidence in high-income countries. However, stroke remains a major cause of death and disability, and therefore research should be continued. Subarachnoid hemorrhages are less prevalent than strokes but have an even higher risk of death. Similar to stroke, epidemiologic studies identified smoking and hypertension as its most important risk factors, together with excessive alcohol intake. Although rare, arterial dissections, CADASIL, arteriovenous malformations, venous sinus thrombosis, moyamoya disease, and vasculitis can lead to serious symptoms. The burden and risk factors of those rare diseases are more challenging to assess. Whenever possible, they should be recognized in a timely manner for their increased risk of stroke, but most often they are diagnosed only at the time of stroke. Some cerebrovascular abnormalities do not result in immediate symptoms. This subclinical cerebrovascular disease includes silent infarcts, white-matter lesions, and microbleeds, and is incidentally found by neuroimaging. These lesions are not innocent, as several epidemiologic studies have associated subclinical cerebrovascular disease with an increased risk of stroke, cognitive decline, dementia, and death.

Headway Duo microcatheter for cerebral arteriovenous malformation embolization with n-BCA

Background

Cerebral arteriovenous malformations (AVMs) are uncommon vascular lesions, and hemorrhage secondary to AVM rupture results in significant morbidity and mortality. AVMs may be treated by endovascular embolization, and technical advances in microcatheter design are likely to improve the success and safety of endovascular embolization of cerebral AVMs.

Objective

To describe our early experience with the Headway Duo microcatheter for embolization of cerebral AVMs with n-butyl-cyanoacrylate (n-BCA).

Methods

Consecutive patients treated by endovascular embolization of a cerebral AVM with n-BCA delivered intra-arterially through the Headway Duo microcatheter (167 cm length) were identified. Patient demographic information, procedural details, and patient outcome were determined from electronic medical records.

Results

Ten consecutive patients undergoing cerebral AVM embolization using n-BCA injected through the Headway Duo microcatheter were identified. Presenting symptoms included headache, hemorrhage, seizures, and weakness. Spetzler Martin grades ranged from 1 to 5, and AVMs were located in the basal ganglia (2 patients), parietal lobe (4 patients), frontal lobe (1 patient), temporal lobe (1 patient), an entire hemisphere (1 patient), and posterior fossa (1 patient). 50 arterial pedicles were embolized, and all procedures were technically successful. There was one post-procedural hemorrhage that was well tolerated by the patient, and no other complications occurred. Additional AVM treatment was performed by surgery and radiation therapy.

Conclusions

The Headway Duo microcatheter is safe and effective for embolization of cerebral AVMs using n-BCA. The trackability and high burst pressure of the Headway Duo make it an important and useful tool for the neurointerventionalist during cerebral AVM embolization.

Case Report: Microsurgical excision of grade 5 cerebral AVM

In this case report, we discuss the microsurgical management of a Spetzler-Martin grade 5 arteriovenous malformation (AVM) in a young boy who presented with a hemorrhagic episode and had a high calculated risk of rebleeding. We also outline the rationale for choosing the management option.

Role of embolization for cerebral arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are complex high-flow lesions that can result in devastating neurological injury when they hemorrhage. Embolization is a critical component in the management of many patients with cerebral AVMs. Embolization may be used as an independent curative therapy or more commonly in an adjuvant fashion prior to either micro- or radiosurgery. Although the treatment-related morbidity and mortality for AVMs--including that due to microsurgery, embolization, and radiosurgery--can be substantial, its natural history offers little solace. Fortunately, care by a multidisciplinary team experienced in the comprehensive management of AVMs can offer excellent results in most cases.

Increased expression of angiogenic factors in cultured human brain arteriovenous malformation endothelial cells

To compare the mRNA level of angiogenic factor vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMP)-2, and MMP-9 in cultured human brain arteriovenous malformation (AVM) endothelial cells (ECs) and normal brain endothelial cells (BECs). Tissue explants both from deformed vessels of AVM and normal microvessel were put into culture for endothelial cells. After the monolayer adherent ECs reached confluence, they were tested with endothelial specific marker CD34 and von Willebrand factor (vWF) by immunochemical assay. mRNA levels of VEGF-A, MMP-2, and MMP-9 in AVM endothelial cells (AVMECs) and BECs were measured by PCR. Immunostaining confirmed that more than 95 % of the cultured cells were CD34 (Fig. 1b) and/or vWF positive. Expression levels of VEGF-A and MMP-2 mRNAs were significantly higher in AVMECs than in BECs. The MMP-9 level was also increased in AVMECs, but the difference was not statistically significant. Vascular tissue explants adherent method is a better approach for isolation and culture of AVMECs. Cultured AVMECs expressed higher angiogenic factors (VEGF, MMP-2) than the controlled BECs, implicating angiogenesis plays an important role in the pathogenesis of AVM.

Overall outcomes following early interventions for intracranial arteriovenous malformations with hematomas

We evaluated the timing and predictors of surgical intervention for intracranial arteriovenous malformations (AVM) with hematoma. A ruptured intracranial AVM with hematoma is an emergency condition, and the optimal timing for surgical intervention is not well understood. In addition, the outcome predictors of surgical intervention have rarely been reported. We identified and analyzed 78 patients treated with microsurgical resection for pathologically proven AVM at Louisiana State University Health in Shreveport from February 1992 to December 2004. All 78 patients were diagnosed with ruptured AVM before surgery. The independent variables, including patient demographics, timing of surgery, location of the AVM and comorbidities were analyzed to assess outcome. The results of this series revealed that surgical intervention after 48hours resulted in poor outcomes for patients with hematoma, following a ruptured AVM. Several other prognostic factors, including younger age (11-40years), Spetzler-Martin Grade I and II, and AVM in a supratentorial location, had significant positive effects on outcomes. However, hypertension, smoking, and a prior embolization showed significant negative effects on outcomes after surgery. The multiple logistic regression analyses also revealed that the timing of surgical intervention had a significant effect on outcomes in patients with hematoma following ruptured AVM. Early intervention is the key to success in these patients.

The Role of Macrophage in the Pathogenesis of Brain Arteriovenous Malformation

Brain arteriovenous malformation (BAVM) is an important risk factor for intracranial hemorrhage, especially in children and young adults. Inflammation has been implicated in BAVM lesion progression. Among various inflammatory components, macrophage is one of the major inflammatory cells present in human ruptured and unruptured BAVM and in the BAVM lesions of animal models. The role of macrophage in BAVM pathogenesis is not fully understood. In this review, we summarize recent studies on macrophages and introduce a non-invasive imaging protocol as a potential tool for detecting macrophage in BAVM and predicting the risk of BAVM rupture.

Surgical Resection of a Progressive Giant Arteriovenous Malformation After 13-year Follow-Up

Giant arteriovenous malformation (AVM) is a complex and relatively rare congenital lesion with high morbidity and mortality. Its optimal treatment, however, remains controversial. Normal perfusion pressure breakthrough (NPPB) is a potentially devastating complication following surgical resection. Generally, strict blood pressure control is particularly recommended for preventing this phenomenon. Here we present a case of a 21-year-old patient with a progressive giant AVM who developed frequent seizures and subsequently underwent microsurgical total resection after 13-year follow-up, complicated by NPPB. Hypertensive hypervolemic treatment rather than strict blood pressure control was administrated postoperatively; however thalamic infarction occurred. During the 1 year of follow-up, the patient remained seizure-free with only mild right-sided hemiparesis.This case highlights that, in view of potential growth of the lesion, early intervention is necessary when possible. Microsurgical resection is challenging but remains to be an effective option for eliminating such giant AVM, and it is vital to keep risks associated with surgery in mind, such as NPPB. Moreover, whether blood pressure control is needed or not should be individualized.

Experimental Animal Models of Arteriovenous Malformation: A Review

Arteriovenous malformations (AVMs) are congenital lesions that cause brain haemorrhage in children and young adults. Current treatment modalities include surgery, radiosurgery and embolization. These treatments are generally effective only for small AVMs. Over one third of AVMs cannot be treated safely and effectively with existing options. Several animal models have been developed with the aims of understanding AVM pathophysiology and improving treatment. No animal model perfectly mimics a human AVM. Each model has limitations and advantages. Models contribute to the understanding of AVMs and hopefully to the development of improved therapies. This paper reviews animal models of AVMs and their advantages and disadvantages.

Notch receptor expression in human brain arteriovenous malformations

The roles of the Notch pathway proteins in normal adult vascular physiology and the pathogenesis of brain arteriovenous malformations are not well-understood. Notch 1 and 4 have been detected in human and mutant mice vascular malformations respectively. Although mutations in the human Notch 3 gene caused a genetic form of vascular stroke and dementia, its role in arteriovenous malformations development has been unknown. In this study, we performed immunohistochemistry screening on tissue microarrays containing eight surgically resected human brain arteriovenous malformations and 10 control surgical epilepsy samples. The tissue microarrays were evaluated for Notch 1–4 expression. We have found that compared to normal brain vascular tissue Notch-3 was dramatically increased in brain arteriovenous malformations. Similarly, Notch 4 labelling was also increased in vascular malformations and was confirmed by western blot analysis. Notch 2 was not detectable in any of the human vessels analysed. Using both immunohistochemistry on microarrays and western blot analysis, we have found that Notch-1 expression was detectable in control vessels, and discovered a significant decrease of Notch 1 expression in vascular malformations. We have demonstrated that Notch 3 and 4, and not Notch 1, were highly increased in human arteriovenous malformations. Our findings suggested that Notch 4, and more importantly, Notch 3, may play a role in the development and pathobiology of human arteriovenous malformations.

4D DSA a new technique for arteriovenous malformation evaluation: a feasibility study

BACKGROUND

The angioarchitectural features of an arteriovenous malformation (AVM) provide key information regarding natural history and treatment planning. Because of rapid filling and vascular overlap, two-dimensional (2D) and three-dimensional (3D) digital subtraction angiography (DSA) are often suboptimal for evaluation of these features. We have developed an algorithm that derives a series of fully time-resolved 3D DSA volumes (four-dimensional (4D) DSA) at up to 30 frames/s from a conventional 3D DSA. The temporal/spatial resolution of 4D reconstructions is significantly higher than that provided by current MR angiography and CT angiography techniques. 4D reconstruction allows viewing of an AVM from any angle at any time during its opacification. This feasibility study investigated the potential of 4D DSA to improve the ability to analyze angioarchitectural features compared with conventional 2D and 3D DSA.

METHODS

2D, 3D, and 4D DSA reconstructions of angiographic studies of six AVMs were evaluated by three cerebrovascular neurosurgeons and one interventional neuroradiologist. These observers evaluated the ability of each modality to visualize the angioarchitectural features of the AVMs. They also compared the information provided using the combination of 2D and 3D DSA with that provided by a 4D DSA reconstruction.

RESULTS

By consensus, 4D DSA provided the best ability to visualize the internal features of the AVM including intranidal aneurysms, fistulae, venous obstructions, and sequence of filling and draining. 2D and 3D images in comparison were limited because of overlap of the vasculature.

CONCLUSIONS

In this small series, 4D DSA provided better ability to visualize the angioarchitecture of an AVM than conventional methods. Further experience is required to determine the ultimate utility of this technique.

Factors Predictive of Obliteration After Arteriovenous Malformation Radiosurgery

Objective:

To investigate predictive factors of complete obliteration following treatment with linac-based stereotactic radiosurgery for intracerebral arteriovenous malformations.

Methods:

Archived plans for 48 patients treated at the British Columbia Cancer Agency and who underwent post-treatment digital subtraction angiography to assess obliteration were studied. Actuarial estimates of obliteration were calculated using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazards models were used for analysis of incidence of obliteration. Log-rank test was used to search for parameters associated with obliteration.

Results:

Complete nidus obliteration was achieved in 38/48 patients (79.2%). Actuarial rate of obliteration was 75.9% at 4 years (95% confidence interval 63.1%-88.6%). On univariate analysis, prescribed dose to the margin (p=0.002) and dose to isocentre (p=0.022) showed statistical significance. No parameters were significant in a multivariate model. According to the log-rank test, prescribed dose to the margin of >20 Gy (p=0.004) and dose to the isocentre of >25 Gy (p=0.004) were associated with obliteration.

Conclusion:

Reported series in the literature suggest a number of different factors are predictive of complete obliteration of arteriovenous malformations following radiosurgery. However, differing definitions of volume and complete obliteration makes direct comparison between series difficult. This study demonstrates that complete obliteration of the nidus following linear accelerator-based stereotactic radiosurgery for arteriovenous malformations appears to be most closely related to the prescribed marginal dose. In particular, a marginal dose of >20Gy is strongly associated with obtaining complete obliteration of the nidus.

Constitutively active Notch4 receptor elicits brain arteriovenous malformations through enlargement of capillary-like vessels

Arteriovenous (AV) malformation (AVM) is a devastating condition characterized by focal lesions of enlarged, tangled vessels that shunt blood from arteries directly to veins. AVMs can form anywhere in the body and can cause debilitating ischemia and life-threatening hemorrhagic stroke. The mechanisms that underlie AVM formation remain poorly understood. Here, we examined the cellular and hemodynamic changes at the earliest stages of brain AVM formation by time-lapse two-photon imaging through cranial windows of mice expressing constitutively active Notch4 (Notch4*). AVMs arose from enlargement of preexisting microvessels with capillary diameter and blood flow and no smooth muscle cell coverage. AV shunting began promptly after Notch4* expression in endothelial cells (ECs), accompanied by increased individual EC areas, rather than increased EC number or proliferation. Alterations in Notch signaling in ECs of all vessels, but not arteries alone, affected AVM formation, suggesting that Notch functions in the microvasculature and/or veins to induce AVM. Increased Notch signaling interfered with the normal biological control of hemodynamics, permitting a positive feedback loop of increasing blood flow and vessel diameter and driving focal AVM growth from AV connections with higher blood velocity at the expense of adjacent AV connections with lower velocity. Endothelial expression of constitutively active Notch1 also led to brain AVMs in mice. Our data shed light on cellular and hemodynamic mechanisms underlying AVM pathogenesis elicited by increased Notch signaling in the endothelium.

Intracranial arteriovenous malformation in a college football player and return-to-play considerations

: The reported prevalence rates of arteriovenous malformations (AVMs) in the general population range from 0.001% to 0.50%. The following case describes the initial presentation of hemorrhage from an intracranial AVM in an 18-year-old college football player. It also discusses treatment of the AVM with stereotactic radiosurgery and successful return to football 17 months after radiosurgery (18.5 months after initial presentation). It is the first published description of return to contact sports after stereotactic radiosurgery for intracranial AVM.

Brain AVMs: an endovascular, surgical, and radiosurgical update

Brain arteriovenous malformations (bAVMs) are complex vascular lesions. Despite multiple studies, several classifications, and a great interest of the scientific community, case selection in AVM patients remains challenging. During the last few years, tremendous advancements widened therapeutic options and improved outcomes spreading indications for patients harboring lesions deemed inoperable in the past. Anatomical and biological case specific features, and natural history with a focus on presenting symptoms should be evaluated case by case and always kept in mind while planning a therapeutic management for a bAVMs. A multidisciplinary approach is strongly recommended when dealing with bAVMs and should involve physicians expertise in this kind of challenging lesions. The goal of this paper is to provide a focused review of the most recent acquisitions and therapeutic strategies regarding surgical, endovascular, and radiosurgical treatment.