Long-term outcomes and safety of Gamma Knife radiosurgery in pediatric arteriovenous malformations

Purpose Despite the unique challenges presented by pediatric intracranial AVMs, little data is available on the use of GKRS in the pediatric population. Therefore, we aimed to present our experience with GKRS in treating pediatric AVMs, determining the factors that influence nidus obliteration and poor outcomes, with a focus on delayed complications. Methods This retrospective review examined patients <= 18 years who underwent GKRS between January 2013 and December 2021 for intracranial AVMs. Factors that predicted residual nidus and poor outcomes were analyzed. The utility of AVM size reduction at follow-up in predicting eventual nidus obliteration was tested. Results We treated 101 pediatric patients for AVMs with a mean age of 14.2 +/- 2.8 years. The mean dose delivered was 22.7 +/- 2.4 Gy. After a mean follow-up of 41.4 months, 78 AVMs (77.8%) were obliterated. Residual nidus was associated with prior embolization (HR 4.953; 95% CI 1.343, 18.268; p = 0.016) and age >= 14 years (HR 5.920; 95% CI 1.559, 22.480; p = 0.009) while presentation with bleed (HR 0.178; 95% CI 0.05, 0.631; p = 0.008) was protective. Reduction in size of a nidus during early follow-up closely correlated with eventual obliteration, with increasing accuracy at 6-month, 12-month, and 24-month follow-up (67.6%, 80.2%, and 86.5% respectively). Twelve patients developed perilesional edema, while one patient each developed a chronic encapsulated hematoma (CEH), cyst formation, and rebleed. Dose > 22 Gy (HR 25.641; 95% CI 2.257, 250; p = 0.009) and volume >= 3 cc (HR 7.189; 95% CI 1.176, 43.945; p = 0.033) predicted poor outcomes on multivariate analysis. Conclusions GKRS delivers a high rate of AVM nidus obliteration in the pediatric population, with prior embolization, older age, and unruptured presentation associated with residual nidus. The incidence of delayed complications, although low, warrants regular surveillance in the pediatric population due to their greater life expectancy.