Moyamoya syndrome after prophylactic cranial irradiation for acute lymphocytic leukemia.

A 9-year-old boy presented with an episode of syncope, and MR imaging revealed bilateral internal carotid artery stenosis with moyamoya vessel formation. He had had prophylactic cranial irradiation at a total dose of 24 Gy for the treatment of acute lymphocytic leukemia at the age of 4. Following this, he was in a complete state of remission for 6 years. During an observation period of a year after the onset of syncope, MR imaging showed development of multiple ischemic lesions in both hemispheres. He developed a transient ischemic attack of mild motor weakness in his arm and an indirect anastomosis was performed on the severely affected side at the age of 10. Radiation-induced vasculopathies are known to be associated with primary diseases of intracranial tumors, but the frequency is unclear. Ours is the third case in whom prophylactic cranial irradiation for a hematological disorder might have induced cerebral vasculopathies.