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.