My name is David Hirsch, and today I'll be discussing the evaluation and treatment of children with radiation-induced cerebral vasculopathy. There are no disclosures for this talk. Radiation has delayed effects on large and intermediate vessels that have been well described in the past, resulting in a variety of histopathological changes that produce thickening of the vascular wall and narrowing of vascular channels, resulting in intracranial steno-occlusive disease or radiation-induced cerebral vasculopathy. A number of risk factors have been identified for radiation-induced vasculopathy. Young age has consistently been found to be a risk factor, and in one series, 80% of the patients with radiation-induced vasculopathy had undergone radiation at 10 years of age or younger. A paracellar tumor location has also been consistently found to be a risk factor, and tumors such as craniopharyngiomas and optic pathway gliomas are highly represented in most case series. The total radiation dose is a bit more controversial, with several authors reporting a higher correlation between higher radiation doses, typically above 50 gray, and the onset of radiation-induced vasculopathy, although others have failed to find a link. Recently, proton beam radiation has been increasingly used to treat a number of childhood brain tumors, particularly those involving the skull base. Proton beam radiation deposits its maximal dose at a precise depth, with minimal radiation being delivered to the surrounding tissues, allowing a highly conformal distribution. In theory, this should produce fewer downstream effects than with photon therapy. On the other hand, a few reports have shown that major cerebral vessels that are included in the radiation field can still be exposed to the potential effects of radiation-induced injury, and radiation-induced cerebral vasculopathy can still develop whether protons are used or not. There have been a few reports of surgical revascularization for patients with radiation-induced vasculopathy, but there are a few unique challenges in this patient population that have to be kept in mind. The STA, the superficial temporal artery, which is often used as a donor vessel, may be absent or insufficient as a result of the initial tumor surgery, while other local options such as the pericranium, dura, and temporalis may have been affected by prior radiation and surgery. Bone healing issues and infection become more of an issue after radiation, and cognitive issues, with or without endocrinopathies such as DI, make perioperative fluid management, which we know is critical after revascularization surgery, complicated to say the least. Therefore, our goal for this project was to report our experience in evaluating and treating children with radiation-induced cerebral vasculopathy. We performed a retrospective review of all patients who underwent a catheter angiogram between 2011 and 2019 and were diagnosed with steno-occlusive vasculopathy following radiation therapy. Patients were already undergoing serial MRIs and MRAs as part of a surveillance protocol following cranial radiation. Those who were identified to have significant vascular narrowing or who developed symptoms of stenosis went on to have a catheter angiogram and a Moyamoya protocol MRI-MRA. Thirty-one patients met these inclusion criteria. About half of the patients in our surveys had undergone radiation for a craniopharyngioma and almost 65% received proton beam radiation. Interestingly, the median interval from radiation to diagnosis of vasculopathy was significantly shorter for patients undergoing proton beam radiation compared to photon-based radiation, despite similar surveillance protocols. Fifteen of the 31 patients underwent surgical revascularization involving 18 hemispheres. We used a combination of qualitative ASL imaging and the dynamic cerebral angiogram to assess current at-risk cerebral parenchyma, defined as partially or fully uncompensated hypoperfusion. High-grade stenosis with a corresponding volume of hypoperfused cerebrum that did not fully compensate was one of the main drivers of surgical intervention. The patients in our surveys highlight some of the challenges of treating radiation-induced vasculopathy. The first challenge I had mentioned was the availability and quality of a donor STA. Of the 18 revascularizations, the STA could only be used in 11 cases. Other cases required the occipital artery, posterior auricular artery, or pericranium, and supplemental techniques such as dural inversion and myosinangiosis were sometimes necessary. Here is a representative patient who underwent pielosangiosis using the occipital artery. He was diagnosed with radiation-induced vasculopathy on surveillance imaging 26 months after undergoing proton beam radiation. He had a positive IV sign and diminished perfusion in the right hemisphere. His right STA had been sacrificed during his initial tumor resection, and therefore a right pielosangiosis utilizing the occipital artery was performed. An angiogram one year later demonstrated robust collateralization. The other challenge I highlighted was the high prevalence of endocrinopathies, such as DI, in this patient population. The one permanent adverse outcome in our series involved a patient who presented with right-sided TIAs three years after resection and radiation for a craniopharyngioma. The patient demonstrated a critical left M1 stenosis with mild uncompensated hypoperfusion, and he therefore underwent a left pielosangiosis utilizing the occipital artery. Two weeks later, he developed a contralateral right hemispheric infarct thought to have resulted from hypovolemia secondary to his DI. The remaining patients in the series have done well clinically and radiologically. In conclusion, radiation-induced cerebral vasculopathy is an increasingly recognized delayed complication of cranial radiation. Close surveillance is necessary for all pediatric patients after receiving cranial radiation, whether photon or proton-based radiation is used, and particularly in young patients with paracellar pathology. However, these patients are particularly challenging to evaluate and treat surgically. Thank you.

radiation-induced cerebral vasculopathy

histopathological changes

proton beam radiation

surgical revascularization

pediatric patients