Risk of spontaneous haemorrhage after diagnosis of cerebral arteriovenous malformation

Background A small proportion of strokes are caused by cerebral arteriovenous malformations (AVM). Treatment to prevent intracranial haemorrhage itself carries risks, and untreated AVM may in many cases have a good prognosis. We investigated the risk of subsequent symptomatic bleeding in the clinical course of AVM in patients with and without an initial haemorrhage. Methods 281 unselected, consecutive, prospectively enrolled patients with cerebral AVM were grouped according to their initial clinical presentation—142 presented with and 139 without haemorrhage. The frequency of AVM haemorrhages during the subsequent clinical course (before the start of endovascular, surgical, or radiation treatment) in the two groups was compared by means of Kaplan-Meier life-tables, log-rank test, and multivariate proportional-hazards regression models. Haemorrhage was defined as a clinically symptomatic event with signs of acute bleeding on computed tomography or magnetic resonance brain imaging. Findings During mean follow-up of 8·5 months for the haemorrhage group and 11·9 months for the non-haemorrhage group, haemorrhages occurred in 18 (13%) of the former patients and in three (2%) of the latter (p=0·0002). The annual risk of haemorrhage was 17·8% and 2·2%, respectively. In the multivariate regression model, the adjusted hazard ratio for haemorrhage at initial presentation was 13·9 (95% Cl 2·6–73·8; p=0·002). Deep venous drainage (hazard ratio 4·1 [1·2–14·9], p=0·029) and male sex (9·2 [2·1–41·3], p=0·004) were also significantly associated with subsequent haemorrhage, but no significant association was found for age or AVM size. The annual rate of spontaneous haemorrhage was 32·6% for men and 10·4% for women in the haemorrhage group compared with 3·3% for men and 1·3% for women in the non-haemorrhage group. Among patients with haemorrhage at initial presentation, the risk of haemorrhage fell from 32·9% in year 1 to 11·3% in subsequent years (34·2% to 31·0% in men; 31·1% to 5·5% in women). Interpretation In AVM, patients initially presenting with haemorrhage have a higher risk of subsequent bleeding than those presenting with other symptoms. The risk is higher in men than in women.