title: Stereotactic radiosurgery for arteriovenous malformations, Part 1: management of Spetzler-Martin Grade I and II arteriovenous malformations.
abstract: OBJECTIVE
  The aim of this paper was to define the outcomes and risks of stereotactic radiosurgery (SRS) for Spetzler-Martin Grade I and II arteriovenous malformations (AVMs).
  
  
  METHODS
  Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs, including 217 patients with AVMs classified as Spetzler-Martin Grade I or II. The median maximum diameter and target volumes were 1.9 cm (range 0.5-3.8 cm) and 2.3 cm(3) (range 0.1-14.1 cm(3)), respectively. The median margin dose was 22 Gy (range 15-27 Gy).
  
  
  RESULTS
  Arteriovenous malformation obliteration was confirmed by MR imaging in 148 patients and by angiography in 100 patients with a median follow-up of 64 months (range 6-247 months). The actuarial rates of total obliteration determined by angiography or MR imaging after 1 SRS procedure were 58%, 87%, 90%, and 93% at 3, 4, 5, and 10 years, respectively. The median time to complete MR imaging-determined obliteration was 30 months. Factors associated with higher AVM obliteration rates were smaller AVM target volume, smaller maximum diameter, and greater marginal dose. Thirteen patients (6%) suffered hemorrhages during the latency period, and 6 patients died. Cumulative rates of AVM hemorrhage 1, 2, 3, 5, and 10 years after SRS were 3.7%, 4.2%, 4.2%, 5.0%, and 6.1%, respectively. This corresponded to rates of annual bleeding risk of 3.7%, 0.3%, and 0.2% for Years 0-1, 1-5, and 5-10, respectively, after SRS. The presence of a coexisting aneurysm proximal to the AVM correlated with a significantly higher hemorrhage risk. Temporary symptomatic adverse radiation effects developed in 5 patients (2.3%) after SRS, and 2 patients (1%) developed delayed cysts.
  
  
  CONCLUSIONS
  Stereotactic radiosurgery is a gradually effective and relatively safe option for patients with smaller volume Spetzler-Martin Grade I or II AVMs who decline initial resection. Hemorrhage after obliteration did not occur in this series. Patients remain at risk for a bleeding event during the latency interval until obliteration occurs. Patients with aneurysms and an AVM warrant more aggressive surgical or endovascular treatment to reduce the risk of a hemorrhage in the latency period after SRS.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kano
authors.forename: L Dade
authors.initials: LD
authors.lastname: Lunsford
authors.forename: John C
authors.initials: JC
authors.lastname: Flickinger
authors.forename: Huai-che
authors.initials: HC
authors.lastname: Yang
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Flannery
authors.forename: Nasir R
authors.initials: NR
authors.lastname: Awan
authors.forename: Ajay
authors.initials: A
authors.lastname: Niranjan
authors.forename: Josef
authors.initials: J
authors.lastname: Novotny
authors.forename: Douglas
authors.initials: D
authors.lastname: Kondziolka
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging / Q000601:surgery*; D002533:Cerebral Angiography; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000009:adverse effects / Q000295:instrumentation*; D012189:Retrospective Studies; D016896:Treatment Outcome