Correlation of the Angioarchitectural Features of Cerebral Arteriovenous Malformations with Clinical Presentation of Hemorrhage:

Long-term hemorrhagic risk in pediatric patients with arteriovenous malformations

OBJECTIVE Compared with the general population, the specific natural history of arteriovenous malformations (AVMs) in pediatric patients is less well understood. Furthermore, few pediatric studies have compared posttreatment hemorrhagic risk and functional outcome across different treatment modalities. The objective of this study was to elucidate these points. METHODS The authors retrospectively reviewed all pediatric patients with AVMs evaluated at their institution between 1990 and 2013. The AVM natural history was represented by hemorrhagic risk during the observation period. For treated patients, the observation period was defined as the interval between diagnosis and treatment. Posttreatment hemorrhagic risk and functional outcomes were also assessed. RESULTS A total of 124 pediatric patients with AVMs were evaluated, and 90 patients (72.6%) were retained through follow-up. The average patient age was 13.3 ± 3.8 years, with a mean follow-up period of 9.95 years. The overall AVM obliteration rate was 59.7%. Radiosurgery had an obliteration rate of 49.0%. Thirteen patients were managed conservatively. Four patients under observation hemorrhaged during a total interval of 429.4 patient-years, translating to an annual risk of 0.9%. Posttreatment hemorrhagic risk by treatment modalities were categorized as follows: surgery ± embolization (0.0%), radiosurgery ± embolization (0.8%), embolization alone (2.8%), surgery + radiosurgery ± embolization (3.5%), and observation (0.8%). A significantly higher risk of posttreatment hemorrhage was observed for patients with hemorrhagic presentation (p = 0.043) in multivariate analysis. Seizure presentation, frontal lobe location, nonheadache presentation, and treatment modality were significantly associated with increased risk of poor functional outcomes. CONCLUSIONS In this study of pediatric patients with AVMs, the natural history of hemorrhage was relatively low at 0.9%. Resection remained the optimal management for hemorrhage control and functional outcome perseverance in these pediatric patients with AVMs. AVM obliteration is a valid treatment goal, especially for patients with ruptured presentation, to prevent further hemorrhages later in life.

Natural history of brain arteriovenous malformations: a systematic review

OBJECT

The authors aimed to systematically review the literature to clarify the natural history of brain arteriovenous malformations (BAVMs).

METHODS

The authors searched PubMed for one or more of the following terms: natural history, brain arteriovenous malformations, cerebral arteriovenous malformations, and risk of rupture. They included studies that reported annual rates of hemorrhage and that included either 100 patients or 5 years of treatment-free follow-up.

RESULTS

The incidence of BAVMs is 1.12-1.42 cases per 100,000 person-years; 38%-68% of new cases are first-ever hemorrhage. The overall annual rates of hemorrhage for patients with untreated BAVMs range from 2.10% to 4.12%. Consistently implicated in subsequent hemorrhage are initial hemorrhagic presentation, exclusively deep venous drainage, and deep and infrantentorial brain location. The risk for rupture seems to be increased by large nidus size and concurrent arterial aneurysms, although these factors have not been studied as thoroughly. Venous stenosis has not been implicated in increased risk for rupture.

CONCLUSIONS

For patients with BAVMs, although the overall risk for hemorrhage seems to be 2.10%-4.12% per year, calculating an accurate risk profile for decision making involves clinical attention and accounting for specific features of the malformation.

Number and location of draining veins in pediatric arteriovenous malformations: association with hemorrhage

OBJECT

The significance of draining vein anatomy is poorly defined in pediatric arteriovenous malformations (AVMs). In adult cohorts, the presence of fewer veins has been shown to lead to an increased rate of hemorrhage, but this phenomenon has not yet been studied in pediatric AVMs. This report analyzes the impact of draining vein anatomy on presentation and outcome in a large series of pediatric AVMs.

METHODS

Eighty-five pediatric patients with AVMs were treated at the Columbia University Medical Center between 1991 and 2012. Charts were retrospectively reviewed for patient characteristics, clinical course, neurological outcome, and AVM angioarchitectural features identified on the angiogram performed at presentation. Univariate analyses were performed using chi-square test and ANOVA when appropriate; multivariate analysis was performed using logistic regression.

RESULTS

Four patients were excluded due to incomplete records. Twenty-seven patients had 2 or 3 draining veins; 12 (44.4%) of these patients suffered from hemorrhage prior to surgery. Fifty-four patients had 1 draining vein; 39 (72.2%) of these 54 suffered from hemorrhage. Independent predictors of hemorrhage included the presence of a single draining vein (p = 0.04) and deep venous drainage (p = 0.02). Good outcome (modified Rankin Scale [mRS] score < 3) on discharge was found to be associated with higher admission Glasgow Coma Scale (GCS) scores (p = 0.0001, OR 0.638, 95% CI 0.40-0.93). Poor outcome (mRS score > 2) on discharge was found to be associated with deep venous drainage (p = 0.04, OR 4.68, 95% CI 1.1-19.98). A higher admission GCS score was associated with a lower discharge mRS score (p = 0.0003, OR 0.6, 95% CI 0.46-0.79), and the presence of a single draining vein was associated with a lower mRS score on long-term follow-up (p = 0.04, OR 0.18, 95% CI 0.032-0.99).

CONCLUSIONS

The authors' data suggest that the presence of a single draining vein or deep venous drainage plays a role in hemorrhage risk and ultimate outcome in pediatric AVMs. Small AVMs with a single or deep draining vein may have the highest risk of hemorrhage.

Curing arteriovenous malformations using embolization

Endovascular embolization is typically reserved as an adjuvant therapy in the management of cerebral arteriovenous malformations (AVMs), either for preoperative devascularization or preradiosurgical volume reduction. Curative embolization plays a limited role in AVM treatment but several studies have shown that it is possible, especially with later-generation liquid embolic agents. Given the complexity of AVM anatomy and the recent controversies over the role of any intervention in AVM management, it is critical that the cerebrovascular community better define the indications of each treatment modality to provide quality AVM management. In this review, the authors evaluate the role of curative AVM embolization. Important considerations in the feasibility of curative AVM embolization include whether it can be performed reliably and safely, and whether it is a durable cure. Studies over the past 20 years have begun to define the anatomical factors that are amenable to complete endovascular occlusion, including size, feeding artery anatomy, AVM morphology, and endovascular accessibility. More recent studies have shown that highly selected patients with AVMs can be treated with curative intent, leading to occlusion rates as high as 100% of such prospectively identified lesions with minimal morbidity. Advances in endovascular technology and techniques that support the efficacy and safety of curative embolization are discussed, as is the importance of superselective diagnostic angiography. Finally, the durability of curative embolization is analyzed. Overall, while still unproven, endovascular embolization has the potential to be a safe, effective, and durable curative treatment for select AVMs, broadening the armamentarium with which one can treat this disease.

Association between posterior fossa arteriovenous malformations and prenidal aneurysm rupture: potential impact on management

Object

In patients with posterior fossa arteriovenous malformations (AVMs) who present with hemorrhage, feeding artery aneurysms are often the source of bleeding. The aim of this study was to evaluate the relative proportions of cases of infra- and supratentorial AVMs in which patients presented with prenidal aneurysm rupture. The management and outcome of 9 cases of posterior fossa AVMs associated with prenidal aneurysm rupture are presented.

Methods

The authors retrospectively reviewed 233 consecutive AVM cases involving patients treated at their institution between April 2001 and August 2012. Patients with a prenidal aneurysm as the cause of the hemorrhage were identified. The frequencies of prenidal aneurysm-related ruptures were compared in cases of supra- and infratentorial AVMs. Management and clinical outcome (modified Rankin Scale [mRS] score) of patients with posterior fossa AVMs treated for ruptured prenidal aneurysms were recorded.

Results

Of 233 AVMs, 25 (11%) were in the posterior fossa, and in 22 (88%) of these cases, the patients presented with hemorrhage, including 9 patients (41%) who presented with hemorrhage due to prenidal aneurysm rupture. Of 208 patients with supratentorial AVMs, 107 (51%) presented with hemorrhage, including 5 patients (4.7%) in whom the hemorrhage was associated with a prenidal aneurysm (p < 0.01). All 9 patients with posterior fossa AVMs and prenidal aneurysm rupture were treated with early embolization of the offending aneurysm. There was no early rebleeding or clinical complication related to this approach. At the end of follow-up (mean 46.8 months), 2 patients had an mRS score of 0, 1 had a score of 1, 3 had a score of 2, 2 patients were dead (mRS score of 6), and 1 patient was lost to follow-up.

Conclusions

Posterior fossa AVM hemorrhages are frequently associated with prenidal arterial aneurysms. Urgent endovascular treatment of the aneurysm was effective in this case series.

Natural history of cerebral arteriovenous malformations: a meta-analysis

Object

The purpose of this report was to provide overall arteriovenous malformation (AVM) hemorrhage rates and, with enhanced statistical power, to elucidate significant risk factors for hemorrhage.

Methods

The authors performed a meta-analysis via the PubMed database through January 2012 using the terms “AVM,” “arteriovenous malformation,” “natural history,” “bleed,” and “hemorrhage.” Additional studies were identified through reference searches in each reviewed article. English language studies providing annual hemorrhage rates for AVMs were included. Data extraction, performed independently by the authors, included demographic data, hemorrhage rates, and hazard ratios for hemorrhage risk factors. The analysis was performed using a random effects model.

Results

Nine natural history studies with 3923 patients and 18,423 patient-years of follow-up were identified for analysis. The overall annual hemorrhage rate was 3.0% (95% CI 2.7%–3.4%). The rate of hemorrhage was 2.2% (95% CI 1.7%–2.7%) for unruptured AVMs and 4.5% (95% CI 3.7%–5.5%) for ruptured AVMs. Prior hemorrhage (HR 3.2, 95% CI 2.1–4.3), deep AVM location (HR 2.4, 95% CI 1.4–3.4), exclusively deep venous drainage (HR 2.4, 95% CI 1.1–3.8), and associated aneurysms (HR 1.8, 95% CI 1.6–2.0) were statistically significant risk factors for hemorrhage. Any deep venous drainage (HR 1.3, 95% CI 0.9–1.75) and female sex (HR 1.4, 95% CI 0.6–2.1) demonstrated a trend toward an increased risk of hemorrhage that was not statistically significant. Small AVM size and older patient age were not significant risk factors for hemorrhage.

Conclusions

Arteriovenous malformations with prior hemorrhage, deep location, exclusively deep venous drainage, and associated aneurysms have greater annual hemorrhage rates than their counterparts, influencing surgical decision making and the selection of radiosurgery for these lesions.

Cerebral dural arteriovenous fistulas and aneurysms

Object

The association of aneurysms and cerebral arteriovenous malformations is well established in the literature. Aside from a small number of case reports and small patient series, this association has not been well explored with cerebral dural arteriovenous fistulas (DAVFs). This study was designed to elucidate this relationship in the authors' own patient cohort with DAVFs.

Methods

Cerebral angiograms of 56 patients with 70 DAVFs were reviewed for the presence of cerebral aneurysms. Background patient demographics, mode of presentation, and DAVF and aneurysm angiographic characteristics were noted.

Results

Twelve patients (21%) had aneurysms in addition to their DAVF. Three patients had multiple aneurysms. Of a total of 15 aneurysms, 5 (33%) occurred on DAVF feeding arteries and 10 (67%) were in remote locations. These patients more commonly presented with hemorrhage (58% vs 20% for those without aneurysms). Aneurysms were associated with DAVFs in any location (feeding artery or remote), but flow-related feeding artery aneurysms were more likely to be associated with Borden Type III DAVFs.

Conclusions

Twenty-one percent of patients with cerebral DAVFs also had aneurysms in this patient cohort. It is thus prudent to perform 6-vessel digital subtraction angiography on patients with DAVFs to rule out potential feeding artery and remote aneurysms. This association may be explained by flow-related phenomena, the initial inciting event leading to DAVF formation, as well as a potential genetic component or predisposition to develop these lesions.

Nidal embolization of brain arteriovenous malformations: rates of cure, partial embolization, and clinical outcome

OBJECT

Nidal embolization of brain arteriovenous malformations (bAVMs) has become an increasingly important component of bAVM treatment. However, controversy exists as to the relative efficacy and safety of single-stage versus multistage approaches to bAVM embolization, with recent literature favoring multistage strategies. The authors present a series of consecutive bAVMs embolized at their institution, demonstrating the safety and efficacy of a predominantly single-stage embolization strategy. The safety and efficacy of embolization are reported in the context of predetermined treatment strategies to provide more generalizable insight into treatment outcome.

METHODS

One hundred thirty consecutive patients with 131 bAVMs underwent endovascular embolization at a single center. Diagnostic angiography with superselective microcatheterizations was performed in all patients. Postembolization angiograms were reviewed by 3 neuroradiologists for degree of occlusion and angiographic evidence of procedural complications. Patients were divided into cohorts based on the prospectively determined treatment strategy, which included the following: global devascularization of the bAVM (Devasc); targeting of a focal angioarchitectural weakness (Target), typically as an adjunct to surgery or Gamma Knife treatment; and primary occlusion of the bAVM by embolization alone (Occlude). Safety and efficacy were evaluated in the context of these treatment groups.

RESULTS

The 131 bAVMs were treated over an average of 1.28 embolization sessions per bAVM; 105 bAVMs (80%) were treated in a single stage. The average percentage devascularization in the Devasc arm was 85.3%, which was statistically significantly greater than the 72% aggregate devascularization reported in 8 modern N-butyl cyanoacrylate and Onyx papers based on 1-sample Wilcoxon rank-sum testing (p<0.001). Focal angioarchitectural weaknesses were successfully embolized for all 24 bAVMs in the Target group, directly with the embolic agent in 23 bAVMs and indirectly in 1 bAVM with a venous aneurysm/pseudoaneurysm by reducing arterial inflow and inducing venous thrombosis. Lesions in all patients in the Occlude arm were 100% occluded with embolization alone. Overall, the bAVMs in the Occlude arm were significantly smaller and required embolization of fewer pedicles than those in the Devasc group. One patient (0.8%) experienced significant morbidity following embolization, and 1 patient in the cohort died (0.8%).

CONCLUSIONS

This research communicates the authors' experience in developing a largely single-stage strategy for embolization of bAVMs. The results suggest that an aggressive, single-stage embolization may be implemented with a margin of safety and effectiveness similar to the multistage approaches more commonly reported in the literature. This work additionally introduces the importance of prospective assignment to a treatment strategy in assessing procedural outcome in bAVM embolization, thereby improving generalizability of the results and allowing for more rigorous interpretation of efficacy and safety.

Arteriovenous malformation-associated aneurysms in the pediatric population

OBJECT

Conventional cerebral angiography and treatment for ruptured arteriovenous malformations (AVMs) in children are often performed in a delayed fashion. In adults, current literature suggests that AVM-associated aneurysms may be more likely to hemorrhage than isolated AVMs, which often leads to earlier angiography and endovascular treatment of associated aneurysms. The nature of AVM-associated aneurysms in the pediatric population is virtually unknown. In this report, the authors investigate the relationship of associated aneurysms in a large group of children with AVMs.

METHODS

Seventy-seven pediatric patients (≤ 21 years old) with AVMs were treated at the Columbia University Medical Center between 1991 and 2010. Medical records and imaging studies were retrospectively reviewed, and associated aneurysms were classified as arterial, intranidal, or venous in location. Clinical presentation and outcome variables were compared between children with and without AVM-associated aneurysms.

RESULTS

A total of 30 AVM-associated aneurysms were found in 22 children (29% incidence). Eleven were arterial, 9 intranidal, and 10 were venous in location. There was no significant difference in the rate of hemorrhage (p = 0.91) between children with isolated AVMs (35 of 55 [64%]) and children with AVM-associated aneurysms (13 of 22 [59%]). However, of the 11 children with AVM-associated aneurysms in an arterial location, 10 presented with hemorrhage (91%). An association with hemorrhage was significant in univariate analysis (p = 0.045) but not in multivariate analysis (p = 0.37).

CONCLUSIONS

Associated aneurysms are present in nearly a third of children with AVMs, and when arterially located, are more likely to present with hemorrhage. These data suggest that early angiography with endovascular treatment of arterial-based aneurysms in children with AVMs may be indicated.

Posterior fossa arteriovenous malformations

Arteriovenous malformations (AVMs) of the posterior fossa are complex neurovascular lesions that are less common than their supratentorial counterparts, accounting for < 15% of all AVMs. The majority of patients with these lesions present with intracranial hemorrhage, a factor that has been consistently shown to increase one's risk for subsequent bleeding. Studies have additionally shown a posterior fossa or deep AVM location to portend a more aggressive natural history. The authors reviewed the literature on posterior fossa AVMs, finding their annual rupture rates to be as high as 11.6%, an important factor that underscores the importance of aggressive treatment of lesions amenable to intervention as therapeutic options and results continue to improve.

Thrombosis and hemorrhage in the acute period following Gamma Knife surgery for arteriovenous malformation

Bleeding of an arteriovenous malformation (AVM) following stereotactic radiosurgery (SRS) is a known risk during the latency interval, but hemorrhage in the 30-day period following radiosurgery rarely has been reported in the literature. The authors present the case of a 57-year-old man who underwent Gamma Knife surgery for a large AVM, and they provide radiographic documentation of a thrombus in the primary draining vein immediately preceding an AVM hemorrhage within 9 days after radiosurgery. They postulate that the pathophysiology of an AVM hemorrhage in the acute period following SRS is related to an association among tissue irradiation, acute inflammatory response, and vessel thrombosis.

The authors also review the literature on risk factors for hemorrhage due to untreated and radiosurgically treated AVMs. Recent evidence on the role of inflammation in the pathogenesis of AVMs and the pathophysiology of AVM rupture is presented. Inflammatory markers have been demonstrated in brain AVM tissue, and the association between inflammation and AVM hemorrhage has been established. There is an acute inflammatory response following tissue irradiation, resulting in structural and functional vascular changes that can lead to vessel thrombosis. Early hemorrhage following radiosurgical treatment of AVMs may be related to the acute inflammatory response and associated vascular changes that occur in irradiated tissue. In the first stage of a planned 2-stage Gamma Knife treatment for a large AVM in the featured case, the superior posteromedial portion of the primary draining vein was included in the treatment field. The authors present the planning images and subsequent CT scans demonstrating a new venous thrombus in the primary draining vein. An acute inflammatory response following radiosurgery with resultant acute venous thrombus formation and venous obstruction is proposed as one mechanism of an AVM hemorrhage in this patient. Radiographic evidence of the time course of thrombosis and hemorrhage supports the hypothesis that acute venous obstruction is a cause of intracranial hemorrhage.

Gamma Knife surgery for intracranial arteriovenous malformations in children: a retrospective study in 103 patients

OBJECT

This retrospective study was designed to study the outcome in children with intracranial arteriovenous malformations (AVMs) treated with Gamma Knife surgery (GKS).

METHODS

One hundred and forty-two children were treated with GKS at the authors' institution between April 1997 and March 2006; of these, 103 patients with a mean follow-up of 26.4 months (range 6-96 months) were included. The mean age at presentation was 13.9 years (range 3-18 years). Eighty-six (83%) patients presented with hemorrhage. In 57 children the AVMs were Spetzler-Martin Grade I or II, and in 46 the AVMs were Grades III, IV, or V. The mean volume of the AVMs was 2.4 ml (range 0.04-23.3 ml). The mean marginal dose administered was 24.4 Gy (range 15-27 Gy). Follow-up angiography was advised at 2 years after GKS and yearly thereafter. In patients with residual AVMs, follow-up angiography was advised yearly until 4 years after GKS. If residual AVM was present, even on a follow-up angiogram obtained 4 years postsurgery, the GKS was considered a failure.

RESULTS

Complete obliteration of the AVM was documented in 34 (87%) of the 39 patients with complete angiographic follow-up. The 3- and 4-year actuarial rates of nidus obliteration were 66 and 86% respectively. Three patients (2.9%) experienced bleeding during the latency period, and symptomatic radiation-induced edema was noted in four patients (3.8%). A significantly higher incidence of radiation edema was noted in patients with AVM volumes greater than 3 ml and in patients with Spetzler-Martin Grade IV and V AVMs.

CONCLUSIONS

Gamma Knife radiosurgery is an effective modality for the treatment of intracranial AVMs in children, yielding high obliteration rates and low complication rates.

Risk factors for subsequent hemorrhage in patients with cerebral arteriovenous malformations

Object

The aim of this study was to identify the natural history of untreated cerebral arteriovenous malformations (AVMs) and the risk factors for subsequent hemorrhage after an initial AVM diagnosis.

Methods

The authors studied 305 consecutive patients with AVMs at the Kyoto University Hospital between 1983 and 2005. These patients were followed up until the first subsequent hemorrhage, the start of any treatment, or the end of 2005. Possible risk factors that were investigated included age at initial diagnosis, sex, type of initial presentation, size and location of the AVM nidus, and the venous drainage pattern. Subsequent hemorrhage occurred in 26 patients from the hemorrhagic group during 380 patient–years, and in 16 patients from the nonhemorrhagic group during 512 patient–years.

Results

The annual bleeding rate in the hemorrhagic group was 6.84% after the initial hemorrhage; however, that rate decreased in the first 5 years (15.42% in the first year, 5.32% in the subsequent 4 years, and 1.72% in more than 5 years). In the nonhemorrhagic group (annual bleeding rate of 3.12%), the patients initially presenting with headaches (annual bleeding rate of 6.48%) or asymptomatic presentations (annual bleeding rate of 6.44%) had a higher risk for subsequent hemorrhage. Conversely, those patients presenting with seizures (annual bleeding rate of 2.20%) or neurological deficits (annual bleeding rate of 1.73%) had a lower risk. A significantly increased risk (p < 0.05) of rebleeding was found among children (hazard ratio [HR] = 2.69), females (HR = 2.93), or patients with deep-seated AVMs (HR = 3.07).

Conclusions

Children, females, and patients with deep-seated AVMs had a threefold increased risk of rebleeding after an initial cerebral AVM. This increased risk was highest in the first year after the initial hemorrhage, and thereafter gradually decreased.

Gamma knife surgery for arteriovenous malformations in the brain: integration of time-resolved contrast-enhanced magnetic resonance angiography into dosimetry planning

Object

The aim of this study was to develop an algorithm for the integration of time-resolved contrast-enhanced magnetic resonance (MR) angiography into dosimetry planning for Gamma Knife surgery (GKS) of arteriovenous malformations (AVMs) in the brain.

Methods

Twelve patients harboring brain AVMs referred for GKS underwent intraarterial digital subtraction (DS) angiography and time-resolved MR angiography while wearing an externally applied cranial stereotactic frame. Time-resolved MR angiography was performed on a 1.5-tesla MR unit (Achieva, Philips Medical Systems) using contrast-enhanced 3D fast field echo sequencing with stochastic central k-space ordering. Postprocessing with interactive data language (Research Systems, Inc.) produced hybrid data sets containing dynamic angiographic information and the MR markers necessary for stereotactic transformation. Image files were sent to the Leksell GammaPlan system (Elekta) for dosimetry planning.

Results

Stereotactic transformation of the hybrid data sets containing the time-resolved MR angiography information with automatic detection of the MR markers was possible in all 12 cases. The stereotactic coordinates of vascular structures predefined from time-resolved MR angiography matched with DS angiography data in all cases. In 10 patients dosimetry planning could be performed based on time-resolved MR angiography data. In two patients, time-resolved MR angiography data alone were considered insufficient. The target volumes showed a notable shift of centers between modalities.

Conclusions

Integration of time-resolved MR angiography data into the Leksell GammaPlan system for patients with brain AVMs is feasible. The proposed algorithm seems concise and sufficiently robust for clinical application. The quality of the time-resolved MR angiography sequencing needs further improvement.