The natural history of intracranial arteriovenous malformations (AVMs) was studied in 143 patients. The main emphasis of the study was hemorrhages. One hundred four of the patients were treated surgically, and 39 were managed nonsurgically. The initial symptom in 68.5% of all patients was hemorrhage. In particular, small and medium-sized AVMs located in the posterior fossa and deep-seated AVMs had a higher risk of hemorrhage.
Follow-up information was obtained from 65 patients, excluding those who underwent acute surgery and died of initial bleeding. The mean follow-up time was 5.6 years. Rebleeding occurred in 60% of 20 patients for whom this was their first hemorrhage, and those cases were followed for an average of 5.3 years.
The rate of rebleeding was 20 a year initially, 3.5 a year after 5 years, and then 1 a year after 10 years. The small-sized AVMs had a higher risk of rebleeding.
On the other hand, patients presenting the symptom of seizure were followed for an average of 5.9 years, and 4 of those patients had a hemorrhage event. Their prognosis was more favorable than patients with only hemorrhage.