Tumefactive cyst with a vascular blush as a late complication after combined embolization and stereotactic radiosurgery treatments for a cerebral arteriovenous malformation.

Cyst formation is a recognized late complication after stereotactic radiosurgery for cerebral arteriovenous malformations (AVMs). We report on a patient with delayed cyst formation after combined embolization and stereotactic radiosurgery treatments for a cerebral AVM. The true nature of the cyst was complicated by tumefactive magnetic resonance MR imaging characteristics. The tumefactive cyst was associated with an additional imaging finding suggestive of a neoplastic lesion - a 'blush' on conventional angiography.