title: Gamma knife radiosurgery-induced cavernous hemangioma: case report.
abstract: OBJECTIVE
  We report a rare case of gamma knife radiation-induced cavernous hemangioma.
  
  
  METHODS
  A 35-year-old man underwent resection of a left vestibular schwannoma and gamma knife radiosurgery (maximal dose, 24 Gy; marginal dose, 12 Gy) for the residual schwannoma. Follow-up magnetic resonance images showed no tumor progression. Ten years later, he developed right hemihyperesthesia and mild hemiparesis. Magnetic resonance imaging revealed a size reduction at the resected tumor site and a newly developed lesion in the adjacent pons. No connection was observed between the new mass and the previous tumor. The T2-weighted image showed the new mass as heterogeneous and "popcorn-like" with a mixed signal intensity core and a hypointense hemosiderin rim. Two years after its appearance, the new lesion appeared hypointense on the T2-weighted image, with a hyperintense core on the T1-weighted image. These findings were compatible with cavernous hemangioma.
  
  
  METHODS
  We diagnosed the new lesion as a radiation-induced cavernous hemangioma. Ten days after admission, symptoms improved without surgical intervention.
  
  
  CONCLUSIONS
  Gamma knife radiosurgery induced this rare case of cavernous hemangioma in an area that received a low dose of irradiation and was distant from the primary tumor. Because patients undergoing radiosurgery face the possibility, although small, that such neoplasms may occur, they should be followed for many years.
authors.affiliation: Department of Neurosurgery, Tonami General Hospital, Tonami, Toyama, Japan. yacchan1218@yahoo.co.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Sasagawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Akai
authors.forename: Shoutarou
authors.initials: S
authors.lastname: Itou
authors.forename: Hideaki
authors.initials: H
authors.lastname: Iizuka
mesh_terms: D000328:Adult; D006392:Hemangioma, Cavernous / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D016634:Radiosurgery / Q000009:adverse effects*