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).
CONCLUSION: 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.
Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan (Kunishima) (Kunimatsu) (Sasaki) (Mori) (Abe) (Ohtomo)
Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan (Shin) (Koga) (Saito)
Department of Radiology, Juntendo University School of Medicine, Tokyo, Japan (Aoki)
Department of Radiology, Tokyo Kita Social Insurance Hospital, Tokyo, Japan (Itoh)
Reprint requests: Masahiro Shin, MD, PhD, Department of Neurosurgery, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113–8655, Japan. E-mail: email@example.com
Received, March 30, 2009.
Accepted, September 16, 2009.