What determines the risk of hemorrhage from cerebral arteriovenous malformations?

We reviewed seven recent articles that discuss the risk factors associated with the hemorrhagic presentation of cerebral arteriovenous malformations (AVMs). Although several such factors have been identified, only nine have been shown to be independent predictors of AVM hemorrhage by multiple logistic regression. All of the studies reviewed are subject to biases that compromise their ability to identify risk factors for hemorrhage confidently. A prospective, multicenter, controlled trial would be necessary to identify such risk factors with certainty.