title: Posterior fossa glioblastoma multiforme: MR findings.
abstract: OBJECTIVE
  To characterize the MR findings of glioblastoma multiforme in the posterior fossa.
  
  
  METHODS
  MR studies of nine patients with surgically proved posterior fossa glioblastoma multiforme were retrospectively evaluated. MR characteristics studied included tumor location, signal intensity, enhancement pattern, and presence of intratumoral hemorrhage, as well as presence of secondary hydrocephalus or metastatic spread.
  
  
  RESULTS
  The tumors were located in the median portion of the cerebellum or brain stem in eight cases. Six extended into the fourth ventricle. Hydrocephalus was seen in four cases. Six cases demonstrated decreased T1- and increased T2-weighted signal intensities. Three cases demonstrated mixed signal intensities suggesting intratumoral hemorrhage. All of the eight patients who received contrast showed moderate to marked heterogeneous ringlike enhancement suggesting intratumoral necrosis. Multicentric/multifocal lesions or extraaxial metastases were identified in three of the nine cases, and there was extracranial extension into the cervical region in one case.
  
  
  CONCLUSIONS
  Glioblastoma multiforme is a rare tumor in the posterior fossa. Differentiating it from metastatic tumor or malignant astrocytoma was difficult. However, combination of heterogeneous and ringlike enhancement, midline location, poorly defined margin, tumoral hemorrhage, concomitant multicentric/multifocal lesions, and extraaxial or extracranial metastasis may be clues for the prospective diagnosis of glioblastoma multiforme.
authors.affiliation: Department of Diagnostic Radiology, University of Maryland Medical System, Baltimore 21201, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kuroiwa
authors.forename: Y
authors.initials: Y
authors.lastname: Numaguchi
authors.forename: M I
authors.initials: MI
authors.lastname: Rothman
authors.forename: G H
authors.initials: GH
authors.lastname: Zoarski
authors.forename: M
authors.initials: M
authors.lastname: Morikawa
authors.forename: M T
authors.initials: MT
authors.lastname: Zagardo
authors.forename: D A
authors.initials: DA
authors.lastname: Kristt
mesh_terms: D000328:Adult; D001933:Brain Stem / Q000473:pathology / Q000601:surgery; D002528:Cerebellar Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D002531:Cerebellum / Q000473:pathology / Q000601:surgery; D002543:Cerebral Hemorrhage / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D003388:Cranial Fossa, Posterior; D003937:Diagnosis, Differential; D005260:Female; D005909:Glioblastoma / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D012189:Retrospective Studies