Gamma Knife Radiosurgery for Cerebral Arteriovenous Malformation in Children

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

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     Children with arteriovenous malformations may respond differently than adults to gamma knife radiosurgery.
     Our purpose was 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 factors for AVM obliteration.
     Between February 2002 and October 2009, 138 AVM pediatric patients were treated by GKS and followed in our institute.  24 patients were treated twice and 1 patient was treated three times. There were 26 pediatric AVM patients less than 16 years old. Eighteen patients (12 male, 6 female) could be followed up at least 2 years (range; 2.4-7.7) and were continuously evaluated with conventional angiography or MRI about the obliteration of AVM after GKS. 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.
      Fourteen of 18 (77.8 %) patients resulted in the obliteration at 1.6-6.6 (median 4.0 ) months 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 60 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, epilepsy, S-M grade, bleeding episodes before GKS, deep draining vein, the number of isocenter ,volume nidus had no significant influence.
     This was 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 anatomy. 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 AVMs to avoid any complications due to high dose irradiation.


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