title: Repeat γ knife surgery for incompletely obliterated cerebral arteriovenous malformations.
abstract: OBJECTIVE
  The causes of failure after an initial Gamma procedure were studied, along with imaging and clinical outcomes, in a series of 140 patients with cerebral arteriovenous malformations (AVMs) treated with repeat Gamma Knife surgery (GKS).
  
  
  METHODS
  Causes of initial treatment failure included inaccurate nidus definition in 14 patients, failure to fill part of the nidus as a result of hemodynamic factors in 16, recanalization of embolized AVM compartments in 6, and suboptimal dose (<20 Gy) in 23. Nineteen patients had repeat GKS for subtotal obliteration of AVMs. In 62 patients, the AVM failed to obliterate despite correct target definition and adequate dose. At the time of retreatment, the nidus volume ranged from 0.1 to 6.9 cm3 (mean, 1.4 cm3), and the mean prescription dose was 20.3 Gy.
  
  
  RESULTS
  Repeat GKS yielded a total angiographic obliteration in 77 patients (55%) and subtotal obliteration in 9 (6.4%). In 38 patients (27.1%), the AVMs remained patent, and in 16 patients (11.4%), no flow voids were observed on magnetic resonance imaging. Clinically, 126 patients improved or remained stable, and 14 experienced deterioration (8 resulting from a rebleed, 2 caused by persistent arteriovenous shunting, and 4 related to radiation-induced changes).
  
  
  CONCLUSIONS
  By using repeat GKS, we achieved a 55% angiographic cure rate. Although radiation-induced changes as visualized on magnetic resonance imaging occurred in 48 patients (39%), only 4 patients (3.6%) developed permanent neurological deficits. These findings may be useful in deciding the management of AVMs in whom total obliteration after initial GKS was not achieved.
authors.affiliation: Lars Leksell Center for Gamma Surgery, Department of Neurological Surgery, University of Virginia Health Sciences System, Charlottesville, Virginia 22908, USA.
authors.forename: Chun-Po
authors.initials: CP
authors.lastname: Yen
authors.forename: Surbhi
authors.initials: S
authors.lastname: Jain
authors.forename: Iftikhar-ul
authors.initials: IU
authors.lastname: Haq
authors.forename: Jay
authors.initials: J
authors.lastname: Jagannathan
authors.forename: David
authors.initials: D
authors.lastname: Schlesinger
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
authors.forename: Ladislau
authors.initials: L
authors.lastname: Steiner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology* / Q000601:surgery; D011859:Radiography; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D012086:Reoperation / Q000379:methods / Q000639:trends; D055815:Young Adult