Radiation-Induced Moyamoya Syndrome in Children with Brain Tumors: Case Series and Literature Review

Background: Over the last decades, significant advancements have been achieved in the treatment of pediatric brain tumors as a result of radiation therapy (RT). With the increasing diffusion of this treatment, iatrogenic damage to cerebrovascular tissues contouring the radiation target volume has become the subject of debate, especially radiation-induced moyamoya syndrome (RIMS). Methods: A systematic literature search was performed on the association between moyamoya vasculopathy and cranial irradiation in children. Large case series of patients with moyamoya were analyzed and clinicoradiologic data were collected reviewing pediatric patients treated with RT for primary brain tumors at our institution. Results: The risk of developing RIMS is higher in younger children, in patients with optic pathway glioma, and in those receiving higher radiation doses. Headache is the most common presenting symptom and cerebral infarction is frequent. The preferred surgical techniques were pial synangiosis and encephaloduroarteriosynangiosis. In our case series, surgical revascularization led to neovascularization, with clinical improvement or stability in all patients. Medical therapy did not significantly affect the clinical course. Conclusions: Pediatric patients receiving involved field RT for the treatment of brain tumors have an increased risk of developing RIMS. Prompt diagnosis and early surgical revascularization play a pivotal role in decreasing the clinical impact of this complication. The use of new techniques, such as the intensity-modulated RT, and the increasing dose saving for the organs at risk, are essential to prevent iatrogenic vasculopathy. The combination of appropriate medical therapy and surgery will improve patient management and clinical outcome.