Contrast-enhanced magnetic resonance characteristics of arteriovenous malformations after γ knife radiosurgery: predictors of post-angiographic obliteration hemorrhage.
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.
Kunishima
Kanako
K
Department of Radiology, The University of Tokyo Hospital, and Juntendo University School of Medicine, Tokyo, Japan.
Shin
Masahiro
M
Kunimatsu
Akira
A
Aoki
Shigeki
S
Sasaki
Hiroki
H
Koga
Tomoyuki
T
Itoh
Daisuke
D
Mori
Harushi
H
Abe
Osamu
O
Ohtomo
Kuni
K
Saito
Nobuhito
N
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
D003287:Contrast Media