title: Long-term complications after gamma knife surgery for arteriovenous malformations.
abstract: OBJECTIVE
  The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs).
  
  
  METHODS
  Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05).
  
  
  CONCLUSIONS
  Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.
authors.affiliation: Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, Tokyo, Japan. mizawa@nij.twmu.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Izawa
authors.forename: Motohiro
authors.initials: M
authors.lastname: Hayashi
authors.forename: Mikhail
authors.initials: M
authors.lastname: Chernov
authors.forename: Koutarou
authors.initials: K
authors.lastname: Nakaya
authors.forename: Taku
authors.initials: T
authors.lastname: Ochiai
authors.forename: Noriko
authors.initials: N
authors.lastname: Murata
authors.forename: Yuchii
authors.initials: Y
authors.lastname: Takasu
authors.forename: Osami
authors.initials: O
authors.lastname: Kubo
authors.forename: Tomokatsu
authors.initials: T
authors.lastname: Hori
authors.forename: Kintomo
authors.initials: K
authors.lastname: Takakura
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D002533:Cerebral Angiography; D002543:Cerebral Hemorrhage / Q000209:etiology*; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011829:Radiation Dosage; D016634:Radiosurgery / Q000295:instrumentation*; D013995:Time; D014057:Tomography, X-Ray Computed