A population-based study of brain arteriovenous malformation: long-term treatment outcomes.
BACKGROUND AND PURPOSE: By undertaking long-term follow-up of a functionally isolated population study group, we sought to achieve a true picture of intrinsic brain arteriovenous malformation (BAVM). We sought to assess the validity of earlier population-based series and to determine the effects of newer treatment methods on the overall morbidity and mortality of BAVM. METHODS: We excluded other intracranial vascular pathologies by defining criteria. By retrospective and prospective study, 240 patients with BAVM were followed for a mean of 10.11 years from first diagnosis. RESULTS: Death rates were as follows: all causes, 12.9%; all BAVM related, 8.75%; BAVM related during conservative management, 24.6%; and BAVM related during active management, 3.9% (P=0.031). Mean diagnosis-to-death interval was 10.6 years. Oxford neurological disability scale grades of 209 survivors (July 2001) were as follows: grades 0 to 2, 74.1%; grade 3, 17.2%; and grades 4 to 5, 9.5%. Death rates were higher for patients who had bled or suffered nonhemorrhagic neurological deficit at original presentation. Incidence of first-ever hemorrhage in untreated patients was as follows: 0 to 9 years, 4.6% (P=0.0035); 30 to 39 years, 21% (P=0.02); and 60 to 69 years, 40.0% (P=0.045). The first bleed was fatal in 4.6%. CONCLUSIONS: We find no evidence of a substantial undiagnosed reservoir of nonsymptomatic BAVM. All BAVM are potentially hazardous. The great majority of BAVM patients become symptomatic during the patient's lifetime, and the majority will bleed. The risk of first hemorrhage is lifelong and rises with age. Compared with earlier population-based series, our low overall patient mortality is predominantly due to higher proportions of active treatment in the 1980s and 1990s.