Neurosurgical management of proton beam therapy-induced moyamoya syndrome

OBJECTIVE Proton beam therapy (PBT) is an increasingly used treatment modality for pediatric patients with brain tumors. Moyamoya syndrome (MMS) is well recognized as a complication of traditional photon radiotherapy, however its association with PBT is less well described. The authors discuss their initial experience with the neurosurgical manage-ment of MMS secondary to PBT in a large-volume pediatric neurovascular service.METHODS The authors performed a retrospective case review of consecutive children referred for neurosurgical man-agement of MMS after PBT between 2009 and 2022. Patient demographic characteristics, oncological history and treat-ment, interval between PBT and MMS diagnosis, and MMS management were recorded. Clinical outcome at last review was classified as good if the modified Rankin Scale (mRS) score was <= 2 and/or the patient attended mainstream educa- tion without additional assistance. Poor outcome was defined as mRS score >= 3 and/or the patient received additional educational support. The recorded radiological outcomes included angiographic analysis of stenosis, evidence of brain ischemia/infarction on MRI, and postsurgical angiographic revascularization.RESULTS Ten patients were identified. Oncological diagnosis included craniopharyngioma (n = 6), optic pathway glioma (1), ependymoma (1), Ewing sarcoma (1), and rhabdosarcoma (1). The median (interquartile range [IQR]) age at PBT was 5.1 (2.7-7.9) years. The median (IQR) age at MMS diagnosis was 7.8 (5.7-9.3) years. The median time be-tween PBT and diagnosis of MMS was 20 (15-41) months. Six patients had poor functional status after initial oncologi-cal treatment and prior to diagnosis of MMS. All 10 patients had endocrine dysfunction, 8 had visual impairment, and 4 had behavioral issues prior to MMS diagnosis. Four patients had a perioperative ischemic event: 2 after tumor surgery, 1 after MMS surgical revascularization, and 1 after receiving a general anesthetic for an MRI scan during oncological surveillance. Seven children were treated with surgical revascularization, whereas 3 were managed medically. The inci-dence of ischemic events per cerebral hemisphere was reduced after surgical revascularization: only 1 patient of 7 had an ischemic event during the follow-up period after surgery. No children moved from good to poor functional status after MMS diagnosis.CONCLUSIONS MMS can occur after PBT. Magnetic resonance angiography sequences should be included in sur-veillance MRI scans to screen for MMS, and families should be counseled about this complication. Management at a high-volume pediatric neurovascular center, including selective use of revascularization surgery, appears to maintain functional status in these children. https://thejns.org/doi/abs/10.3171/2022.12.PEDS22423