Chronic encapsulated intracerebral hematoma formation after radiosurgery for cerebral arteriovenous malformation.

We report a rare case of chronic encapsulated intracerebral hematoma (CEIH) after radiosurgery for a cerebral arteriovenous malformation (AVM). A 49-year-old male underwent transarterial embolization and surgical excision of a cerebral AVM presenting with cerebral hemorrhage in the left temporal lobe. Stereotactic radiosurgery (SRS) was done after 12 months. Magnetic resonance imaging (MRI) 14 months after SRS showed a small-enhancing lesion close to the left lateral ventricle and marked white matter edema. At that time a diagnosis of radiation-induced necrosis was made and steroids administered. At 43 months after SRS, MRI showed a small-enhancing mass close to the lateral ventricle with a hematoma cavity. Surgical excision was performed and histological examination revealed that the capsule consisted of an outer collagenous layer and an inner granulated layer with deposits of hemosiderin, which was compatible with CEIH. CEIH should be considered after SRS for AVM.