[A case of cerebral arteriovenous malformation revealing repeated intranidal hemorrhage accompanying neovascularization after stereotactic radiosurgery].

We report a patient with cerebral arteriovenous malformation (AVM) revealing growing mass lesion after stereotactic radiosurgery. This 12-year-old female presented headache. CT scan showed hematoma at the head of the right caudate nucleus and angiography showed AVM at the site. LINAC-based stereotactic radiosurgery was performed with the patient. Twenty-three months after the radiosurgery the patient complained headache and CT scan showed hematoma again at the same site, although angiography did not show AVM. Thirty-five months after the radiosurgery mass lesion with enhancement effect was observed at the site and the mass lesion grew gradually thereafter. Thirty-nine months after the radiosurgery the mass lesion was evacuated. Histological examination revealed fibrotic core and surrounding neovascularized area with hemorrhage. The histology shows a new etiology of growing mass lesion after radiosurgery for AVM.