title: Contrast-enhanced magnetic resonance characteristics of arteriovenous malformations after γ knife radiosurgery: predictors of post-angiographic obliteration hemorrhage.
abstract: BACKGROUND
  The reported cumulative risk of post-angiographic obliteration (post-AO) hemorrhage from arteriovenous malformations (AVMs) following gamma knife radiosurgery (GKRS) over 10 years is 2.2%.
  
  
  OBJECTIVE
  To identify the warning signs of post-AO hemorrhage by analyzing the characteristics of enhancement on contrast-enhanced MRI magnetic resonance imaging (MRI) of AVMs with post-AO hemorrhage.
  
  
  METHODS
  We performed a retrospective analysis of 121 patients whose AVMs were angiographically obliterated within 5 years of GKRS without hemorrhage and who received at least 1 contrast-enhanced MRI after GKRS (group 1), and 7 patients who experienced post-AO hemorrhage (group 2). We analyzed the enhancement persistence ratio (the percentage of AVMs with persisting enhancement on contrast-enhanced T1-weighted image after obliteration) and the change in size of the enhanced region over time in each patient.
  
  
  RESULTS
  The enhancement persistence ratio showed no significant difference between the 2 groups (89.4% vs 100% for groups 1 and 2, respectively; P=.401). While most cases in group 1 showed a tendency to decrease in size and gradually stabilize following GKRS, there were significantly more cases in group 2 with obvious increment of the enhanced regions within 1 year of angiographic obliteration compared with the previous measurement (4.96% vs 71.4% for groups 1 and 2, respectively; P<.0001).
  
  
  CONCLUSIONS
  Our results suggest that AVMs that show an increase in the size of the enhanced region within 1 year of angiographic obliteration should be followed up with caution for post-AO hemorrhage. Persisting enhancement itself is not positively associated with subsequent hemorrhage.
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, and Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Kunishima
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shin
authors.forename: Akira
authors.initials: A
authors.lastname: Kunimatsu
authors.forename: Shigeki
authors.initials: S
authors.lastname: Aoki
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sasaki
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Koga
authors.forename: Daisuke
authors.initials: D
authors.lastname: Itoh
authors.forename: Harushi
authors.initials: H
authors.lastname: Mori
authors.forename: Osamu
authors.initials: O
authors.lastname: Abe
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D002543:Cerebral Hemorrhage / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D003287:Contrast Media / Q000009:adverse effects*; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications* / Q000000981:diagnostic imaging* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011859:Radiography; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media