Hemorrhage Risk Lower Than Expected in Patients With Unruptured Brain AVMs

The annual risk for first intracranial hemorrhage (ICH) among patients with unruptured brain arteriovenous malformations (AVMs) is lower than previously reported, according to study results published in JAMA Neurology.

Unruptured brain AVMs are complex vascular lesions associated with potentially fatal hemorrhage, but treatment decisions remain challenging due to uncertainty about the natural risk for rupture. Therefore, researchers determined precise estimates of first ICH rates and risk factors. This multicenter, international cohort study was conducted between 2017 and 2023 using data from 9 participating centers across 7 countries. Both retrospective and prospective data were included.

A total of 3030 participants, all of whom were diagnosed with an unruptured brain AVM confirmed by imaging, were included in the analysis. Of the participants, the median age was 38 (IQR, 25-50) years, and 50.3% were women. Additionally, 45% presented with seizure, 36% with headache, and 21% with focal neurological deficits. The median maximal AVM diameter was 3.1 (IQR, 2.2-4.4) cm. Of the AVMs, 10% demonstrated exclusively deep venous drainage, 11% were located in cerebellar or deep supratentorial regions, and 19% had associated arterial aneurysms.

Management decisions of unruptured brain AVMs depends on carefully weighing the risk-benefit of treatment against the risk of hemorrhage.

Over 11,339 person-years of follow-up, 159 participants experienced a first ICH, corresponding to a rate of 1.40 (95% CI, 1.20–1.64) per 100 person-years. In multivariable analysis, independent risk factors for first hemorrhage included older age, with individuals aged 60 years and older having a higher risk compared with those younger than 20 years (hazard ratio [HR], 2.01; 95% CI, 1.14–3.57). The presence of associated arterial aneurysms also increased risk (HR, 1.66; 95% CI, 1.06–2.59), as did cerebellar or deep supratentorial location (HR, 1.87; 95% CI, 1.16–3.00). Participants with 2 or more risk factors had a 65% higher risk for hemorrhage (HR, 1.65; 95% CI, 1.21–2.25).

The annual ICH rate observed in this study was notably lower than the 2% to 4% rate often cited in clinical practice.

Study limitations include a mixed retrospective and prospective design, variable follow-up duration across cohorts, and missing data for some clinical factors.

“Management decisions of unruptured brain AVMs depends on carefully weighing the risk-benefit of treatment against the risk of hemorrhage,” the study authors noted.

Disclosures: This research was supported by the National Institutes of Health and additional international foundation grants. Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.