Brain AVM management is still in debate. Because AVM rupture with hemorrhage is on of the main cause of morbi-mortality in this disease, there is a permanent search for predictive factors for bleeding. Some have been determined such as intranidal aneurysms, size, venous stenosis or deep venous drainage. Nevertheless the strongest parameter to predict bleeding is still an episode of AVM rupture and symptomatic hemorrhage. With the need of new parameters that could predict bleeding in clinically unruptured AVMs, the authors of this paper look for a database searching for neuroimaging evidence of blood and histological presence of hemosiderin. They made a retrospective search in their database from 1992 to 2000. In a total of 975 patients, the presence of bleeding signs at MRI was a strong predictor for bleeding (OR 3.97, p<0.001). Also, this parameter showed its prediction capacity for new bleedings after a first ICH (Hazard ratio 3.53, p=0.01). In 127 patients they made an histological analysis looking for hemosiderin. When the sample was positive for hemosiderin there was an association for ICH (OR 2.18, p=0.042).

This novel approach for searching risk factors for AVM rupture is a great contribution for the understanding of this vascular malformations and their natural evolution and rational treatment. Thus, this work could be improved in future works, as the authors also addressed in the paper, with a prospective protocol and the use of more blood sensitive MRI sequences as gradient T2 images.