Objectives: The study of pediatric arteriovenous malformations (pAVMs) is complicated by the rarity of the entity. While Gamma Knife Radiosurgery (GKRS) has been well validated in pediatric patients, the predictors of post-treatment hemorrhage are unclear. We sought to characterize the frequency and predictors of post-treatment hemorrhage after GKRS.

Methods: We conducted a retrospective cohort study examining 183 patients with pAVM presenting to the University of Pittsburgh from 1988-2018 who underwent GKRS as part of their therapy. Univariate analysis was performed comparing post-treatment hemorrhage cases to cases without post-treatment hemorrhage.

Results: A total of 8 (4.4%) patients developed post-treatment hemorrhage at a mean time of 2 years after GKRS. The mean number of GKRS treatments performed in patients with post treatment hemorrhage was 2 (Range 1-3) compared to 1.13 (Range 1-3) in patients without hemorrhage (p = 0.027). Two patients developed recurrence after documented obliteration. Neither patient had post-treatment hemorrhage. The mean first treatment GKRS dose was 20Gy amongst patient without hemorrhage and 18.5Gy amongst those with post-treatment hemorrhage (p = 0.1). Of the 5 patients with post-treatment hemorrhage with adequate follow-up imaging at least 3 years post-treatment, two (40%) had documented obliteration. Of the 137 patients without post-treatment hemorrhage with adequate follow-up imaging, 108 (79%) had documented obliteration (p = 0.08). The mean modified Rankin Scale score at most recent follow-up was 1.6 for patients with post-treatment hemorrhage and 1.0 for patients without post-treatment hemorrhage (p = 0.11). Mean follow-up was 82 months, with 141 (81%) patients having at least 3 years of follow-up and only 3 (1.7%) patients without any follow-up.

Conclusions: Post-radiosurgery hemorrhage is an uncommon consequence of GKRS treatment for pAVMs, but patients still maintain a high rate of good functional outcome despite of this complication. Inadequate treatment doses resulting in poor obliteration rates and thus repeat treatment may be associated with post-treatment hemorrhage.