Moyamoya syndrome after radiation therapy: case reports.

UNLABELLED: Potentially harmful effects of irradiation on the developing central nervous system have been well documented. We report 2 pediatric patients with moyamoya syndrome developed after irradiation. CASE: A 3-year-old girl had received 4,860 cGy of postoperative radiation for optic pathway glioma. Cerebral angiography 7 months after completion of the radiation therapy revealed progressive cerebral arterial occlusive disease, involving the internal carotid artery on either side of the circle of Willis, with abnormal netlike vessels. Another 5-year-old girl had received 3,600 cGy of postoperative radiation on the cerebrum for a medulloblastoma. Two years later, she was diagnosed with moyamoya syndrome and treated with indirect revascularization. She died due to further progressive obstruction of the right M1 and A1 on the unoperated hemisphere, in spite of well-developed collateral circulation from the superficial temporal artery and middle meningeal artery on the operated left hemisphere. We suggest that radiation therapy with portals typically including carotid siphon may particularly cause vascular damage, regardless of the tumor pathology and lead to radiation-induced moyamoya syndrome. The prognosis may be poorer in case of poor collateral flow and rapid progression. The radiation therapy may cause fatal vascular damage so it should be taken into consideration when a treatment plan is being formulated for young patients.