RT Journal Article SR Electronic T1 Tumefactive Cysts: A Delayed Complication following Radiosurgery for Cerebral Arterial Venous Malformations JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 1152 OP 1157 VO 26 IS 5 A1 Whitney B. Edmister A1 John I. Lane A1 Julie R. Gilbertson A1 Robert D. Brown A1 Bruce E. Pollock YR 2005 UL http://www.ajnr.org/content/26/5/1152.abstract AB Summary: We report five cases of symptomatic delayed cyst formation after radiosurgery for intracranial arterial venous malformations. Median time to discovery of the cysts following most recent radiosurgery was 59 months (range, 34–89 months). In all five patients, the radiation therapy–induced cysts exhibited tumefactive characteristics, including vasogenic edema, mass effect, and nodular enhancement. Despite these malignant features, these cystic lesions should be recognized as a benign complication of radiosurgery so that proper treatment (i.e., cystoperitoneal shunt surgery or excision) can be initiated.