title: Stereotactic radiosurgery for arteriovenous malformations, Part 5: management of brainstem arteriovenous malformations.
abstract: OBJECTIVE
  In this paper, the authors' goal was to define the long-term outcomes and risks of stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs) of the medulla, pons, and midbrain.
  
  
  METHODS
  Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs; 67 patients had AVMs in the brainstem. In this series, 51 patients (76%) had a prior hemorrhage. The median target volume was 1.4 cm(3) (range 0.1-13.4 cm(3)). The median margin dose was 20 Gy (range 14-25.6 Gy).
  
  
  RESULTS
  Obliteration of the AVMs was eventually documented in 35 patients at a median follow-up of 73 months (range 6-269 months). The actuarial rates of documentation of total obliteration were 41%, 70%, 70%, and 76% at 3, 4, 5, and 10 years, respectively. Higher rates of AVM obliteration were associated only with a higher margin dose. Four patients (6%) suffered a hemorrhage during the latency period, and 2 patients died. The rate of AVM hemorrhage after SRS was 3.0%, 3.0%, and 5.8% at 1, 5, and 10 years, respectively. The overall annual hemorrhage rate was 1.9%. Permanent neurological deficits due to adverse radiation effects (AREs) developed in 7 patients (10%) after SRS, and a delayed cyst developed in 2 patients (3%). One patient died at an outside institution with symptoms of AREs and unrecognized hydrocephalus. Higher 12-Gy volumes and higher Spetzler-Martin grades were associated with a higher risk of symptomatic AREs. Ten of 22 patients who had ocular dysfunction before SRS had improvement, 9 were unchanged, and 3 were worse due to AREs. Eight of 14 patients who had hemiparesis before SRS improved, 5 were unchanged, and 1 was worse.
  
  
  CONCLUSIONS
  Although hemorrhage after obliteration did not occur in this series, patients remained at risk during the latency interval until obliteration occurred. Thirty-eight percent of the patients who had neurological deficits due to prior hemorrhage improved. Higher dose delivery in association with conformal and highly selective SRS is required for safe and effective radiosurgery.
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: Douglas
authors.initials: D
authors.lastname: Kondziolka
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: Ajay
authors.initials: A
authors.lastname: Niranjan
authors.forename: Josef
authors.initials: J
authors.lastname: Novotny
authors.forename: L Dade
authors.initials: LD
authors.lastname: Lunsford
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001933:Brain Stem / Q000000981:diagnostic imaging / Q000601:surgery*; D002533:Cerebral Angiography; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation*; D012189:Retrospective Studies; D016896:Treatment Outcome