Gamma Knife Radiosurgery For Cerebral Arteriovenous Malformation In Children

Noriko Tamura1, Motohiro Hayashi2, Yoshikazu Okada3

1Shinjukuku, Japan 2Tokyo, Japan 3Tokyo Women’s Medical University Hospital, Tokyo, Japan

Keywords: arteriovenous malformation, gamma knife, children, pediatrics, outcome

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     To evaluate the initial obliteration rate and complication of Gamma Knife Radiosurgery (GKS) for Arteriovenous malformation (AVM) patients in children with a long follow-up and analyze the predictive factor for AVM obliteration.
     Between February 2002 and October 2009, 138 AVMpatients were treated by GKS and followed in our institute. 24 patients were treated twice. And 1 patient ware treated three times.  Among of them, pediatric patients ( less than 16 years old) was 26. Eighteen patients (12 male, 6 female) could be followed up at least2 years (range; 2.4-7.7) and were continuously evaluated with conventional angiography or MRI about the obliteration of AVM after GKS. Six patients were treated twice. Patient’s age was 9.5 in median (range 4-14) years old. Hemorrhage before GKS were seen in 14 (77.8%) patients. According to Spetzler and Martin (S-M) grade, 11 patients (61.1%) were categorized in higher grade (III to VI) including 2 lesions which were located at basal ganglia and thalamus (S-M grade VI).
      Previous treatment before GKS was 4 patients (nidus embolization: 3, surgery: 2). Our treatment strategy for AVM was decided that target volume should be less than 4 ml and target priority should be the nidus related to draining vein. If the target volume of AVM is too large to do single session, we decided to do “staged GKS”. The median number of isocenter was 7.22 (range 1-15) and the average prescription/maximum dose was 22.0/43.8 (range 20-25/36.3-50) Gy. Prescription isodose volume varied from 0.37-6.90 (median 1.90) ml.
     14 of 18 (77.8 %) patients resulted in the overall obliteration at 1.6-6.6 (median 4.0) years after GKS. Post-GKS MRI change showed only 2 patients (one after initial GKS, the other after 2nd GKS) and no neurological deficits occurred in these patients. Two patients had bleeding episode according to AVM at 20 and 36 months after GKS. In statistic analysis, peripheral dose (p=0.013), maximum dose at GKS(p=0.041) had possibility to obliterate AVM. Sex, age, previous AVM treatment, bleeding episodes before GKS, deep draining vein , S-M grade, the number of isocenter ,target volume and volume nidus had no significant influence.
     This is a retrospective study.
     The probability of AVM obliteration following initial Gamma Knife radiosurgery with our treatment strategy demonstrated satisfactory results with higher dose to the nidus related to draining vein. No radiation induced complication occurs and a low bleeding rate (2.8%/year) after the staged radiosurgery.
     Staged radiosurgery should be recommended for pediatric large AVM to avoid any complications due to high dose irradiation.


Project Roles:

N. Tamura (), M. Hayashi (), Y. Okada ()