Supplementary Material for: Radiation-Induced Moyamoya Syndrome after Proton Beam Therapy in the Pediatric Patient: A Case Series

Minimizing normal-tissue radiation exposure is especially important in the pediatric population as children appear to be particularly sensitive to postradiation vasculopathies after conventional photon radiotherapy. Given the limited scattering effect and low-dose radiation delivery to the surrounding tissues with proton beam radiotherapy, this modality is considered to be an effective treatment for pediatric skull-base tumors compared to conventional radiotherapy, and to have fewer adverse side effects. We report 2 cases of radiation-induced moyamoya syndrome following proton beam therapy in pediatric patients. To our knowledge, only a few other reported cases of radiation-induced moyamoya syndrome following proton beam therapy exist in the current literature. While rare, radiation-induced moyamoya syndrome can occur in the pediatric population with newer techniques like proton beam radiotherapy. Accordingly, patients and their families should be informed about this potential complication prior to all forms of radiation treatment.