Interventions for treating brain arteriovenous malformations in adults

Risk of intracranial hemorrhage in brain arteriovenous malformations: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Brain arteriovenous malformations (bAVMs) carry a risk of hemorrhage. We aim to identify factors associated with subsequent hemorrhages.

METHODS

Systematic searches were conducted across the ScienceDirect, Medline, and Cochrane databases. Assessed risk factors included bAVM size, bAVM volume, hemorrhage and seizure presentations, presence of deep venous drainage, deep-seated bAVMs, associated aneurysms, and Spetzler-Martin grade. Subgroup analyses were conducted on prior treatments, hemorrhage presentation, AVM size, and type of management.

RESULTS

The meta-analysis included 8 cohort studies and 2 trials, with 4,240 participants. Initial hemorrhage presentation (HR 2.41; 95% CI 1.94-2.98; p < 0.001), any deep venous drainage (HR 1.52; 95% CI 1.09-2.13; p = 0.01), and associated aneurysms (HR 1.78; 95% CI 1.41-2.23; p < 0.001) increased secondary hemorrhage risk. Conversely, higher Spetzler-Martin grades (HR 0.77; 95% CI 0.68-0.87; p < 0.001) and larger malformation volumes (HR 0.87; 95% CI 0.76-0.99; p = 0.04) reduced risk. Subgroups showed any deep venous drainage in patients without prior treatment (HR 1.64; 95% CI 1.25-2.15; p < 0.001), bAVM > 3 cm (HR 1.79; 95% CI 1.15-2.78; p = 0.01), and multimodal interventions (HR 1.69; 95% CI 1.12-2.53; p = 0.01) increased risk. The reverse effect was found for patients initially presented without hemorrhage (HR 0.79; 95% CI 0.67-0.93; p = 0.01). Deep bAVM was a risk factor in > 3 cm cases (HR 2.72; 95% CI 1.61-4.59; p < 0.001) and multimodal management (HR 2.77; 95% CI 1.66-4.56; p < 0.001). Kaplan-Meier analysis revealed increased hemorrhage risk for initial hemorrhage presentation, while cumulative survival was higher in intervened patients over 72 months.

CONCLUSION

Significant risk factors for bAVMs hemorrhage include initial hemorrhage, any deep venous drainage, and associated aneurysms. Deep venous drainage involvement is a risk factor in cases without prior treatment, those with bAVM > 3 cm, and cases managed with multimodal interventions. Deep bAVM involvement also emerges as a risk factor in cases > 3 cm and those managed with multimodal approaches.

Endothelial Rbpj deletion normalizes Notch4-induced brain arteriovenous malformation in mice

Upregulation of Notch signaling is associated with brain arteriovenous malformation (bAVM), a disease that lacks pharmacological treatments. Tetracycline (tet)-regulatable endothelial expression of constitutively active Notch4 (Notch4*tetEC) from birth induced bAVMs in 100% of mice by P16. To test whether targeting downstream signaling, while sustaining the causal Notch4*tetEC expression, induces AVM normalization, we deleted Rbpj, a mediator of Notch signaling, in endothelium from P16, by combining tet-repressible Notch4*tetEC with tamoxifen-inducible Rbpj deletion. Established pathologies, including AV connection diameter, AV shunting, vessel tortuosity, intracerebral hemorrhage, tissue hypoxia, life expectancy, and arterial marker expression were improved, compared with Notch4*tetEC mice without Rbpj deletion. Similarly, Rbpj deletion from P21 induced advanced bAVM regression. After complete AVM normalization induced by repression of Notch4*tetEC, virtually no bAVM relapsed, despite Notch4*tetEC re-expression in adults. Thus, inhibition of endothelial Rbpj halted Notch4*tetEC bAVM progression, normalized bAVM abnormalities, and restored microcirculation, providing proof of concept for targeting a downstream mediator to treat AVM pathologies despite a sustained causal molecular lesion.

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

Introduction

Transvenous embolization (TVE) has been proven to be safe and feasible as an alternative management of brain arteriovenous malformations (AVMs). We presented four patients with a hemorrhagic brain AVM who underwent TVE and reviewed the relevant literature.

Methods

Four patients underwent TVE of a hemorrhagic brain AVM in our center between July 2019 and July 2020. We retrospectively collected and analyzed the clinical and imaging data of these patients and those reported in previously published studies.

Results

Four patients with a hemorrhagic brain AVM were included. Nidus sizes ranged from 0.79 to 2.56 cm. Spetzler-Martin grade ranged from grade II to grade III. The AVM nidus was located in a deep brain region in three patients. One patient underwent TVE alone and three underwent combined transarterial and transvenous approaches. Digital subtraction angiography (DSA) demonstrated complete obliteration of the vascular malformation after embolization in all four patients. Three patients were independent [modified Rankin Scale (mRS) score ≤ 2] at discharge. All four patients were independent at the last follow-up. AVM obliteration was confirmed in all four patients at the last angiographic follow-up.

Conclusion

Transvenous embolization can be used as an alternative treatment for contemporary management of brain AVMs, appropriate patient selection is essential to achieve a good clinical outcome.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.