ANNUAL RISK FOR THE FIRST HEMORRHAGE FROM UNTREATED CEREBRAL ARTERIOVENOUS-MALFORMATIONS

To estimate the annual risk for the first hemorrhage, survival and lif e table statistics were used to analyze data from 2262 patients with c erebral arteriovenous malformations (AVM). We found that the risk for hemorrhage increases with increasing age. A validity test revealed, ho wever, that life table statistics used on the total patient materia I underestimated the annual risk for hemorrhage, especially for patients 20-50 years of age. A method based on the fact that the distribution of the time at risk until the initial hemorrhage (=age at first ruptur e) reflects the risk for hemorrhage in untreated AVM was therefore als o employed. The analysis yielded three conclusions: 1) the annual risk of hemorrhage increases with age; 2) small AVM are less prone to rupt ure; and 3) the risk of hemorrhage is higher in women during their fer tile years as compared to males in the same age group. The risk relate d to age, AVM size and location assessed by survival statistics in the subgroup of patients with a known date for the initial hemorrhage gav e similar results.