title: Natural history of brain arteriovenous malformations: a long-term follow-up study of risk of hemorrhage in 238 patients.
abstract: OBJECTIVE
  Long-term follow-up studies in patients with brain arteriovenous malformations (AVM) have yielded contradictory results regarding both risk factors for rupture and annual rupture rate. We performed a long-term follow-up study in an unselected, consecutive patient population with AVMs admitted to the Department of Neurosurgery at Helsinki University Central Hospital between 1942 and 2005.
  
  
  METHODS
  Patients with untreated AVMs were followed from admission until death, occurrence of AVM rupture, initiation of treatment, or until the end of 2005. Patients with at least 1 month of follow-up were included in further analysis. Annual and cumulative incidence rates of AVM rupture as well as several potential risk factors for rupture were analyzed using Kaplan-Meier life table analyses and Cox proportional hazards regression models.
  
  
  RESULTS
  We identified 238 patients with a mean follow-up period of 13.5 years (range, 1 month-53.1 years). The average annual risk of hemorrhage from AVMs was 2.4%. The risk was highest during the first 5 years after diagnosis, decreasing thereafter. Risk factors predicting subsequent AVM hemorrhage in univariate analysis were young age, previous rupture, deep and infratentorial locations, and exclusively deep venous drainage. Previous rupture, large AVM size, and infratentorial and deep locations were independent risk factors according to multivariate models.
  
  
  CONCLUSIONS
  According to this long-term follow-up study, AVMs with previous rupture and large size, as well as with infratentorial and deep locations have the highest risk of subsequent hemorrhage. This risk is highest during the first few years after diagnosis but remains significant for decades.
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Juha A
authors.initials: JA
authors.lastname: Hernesniemi
authors.forename: Reza
authors.initials: R
authors.lastname: Dashti
authors.forename: Seppo
authors.initials: S
authors.lastname: Juvela
authors.forename: Kristjan
authors.initials: K
authors.lastname: Väärt
authors.forename: Mika
authors.initials: M
authors.lastname: Niemelä
authors.forename: Aki
authors.initials: A
authors.lastname: Laakso
mesh_terms: D000293:Adolescent; D000328:Adult; D002543:Cerebral Hemorrhage / Q000209:etiology* / Q000401:mortality; D018450:Disease Progression; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D002538:Intracranial Arteriovenous Malformations / Q000150:complications* / Q000453:epidemiology; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018570:Risk Assessment; D012307:Risk Factors; D013995:Time; D055815:Young Adult