POSTERIOR-FOSSA GLIOBLASTOMA-MULTIFORME - MR FINDINGS

PURPOSE: To characterize the MR findings of glioblastoma multiforme in the posterior fossa. METHODS: MR studies of nine patients with surgic ally proved posterior fossa glioblastoma multiforme were retrospective ly evaluated. MR characteristics studied included tumor location, sign al intensity, enhancement pattern, and presence of intratumoral hemorr hage, as well as presence of secondary hydrocephalus or metastatic spr ead. RESULTS: The tumors were located in the median portion of the cer ebellum or brain stem in eight cases. Six extended into the fourth ven tricle. Hydrocephalus was seen in four cases. Six cases demonstrated d ecreased T1- and increased T2-weighted signal intensities. Three cases demonstrated mixed signal intensities suggesting intratumoral hemorrh age. All of the eight patients who received contrast showed moderate t o marked heterogeneous ringlike enhancement suggesting intratumoral ne crosis. Multicentric/multifocal lesions or extraaxial metastases were identified in three of the nine cases, and there was extracranial exte nsion into the cervical region in one case. CONCLUSION: Glioblastoma m ultiforme is a rare tumor in the posterior fossa. Differentiating it f rom metastatic tumor or malignant astrocytoma was difficult. However, combination of heterogeneous and ringlike enhancement, midline locatio n, poorly defined margin, tumoral hemorrhage, concomitant multicentric /multifocal lesions, and extraaxial or extracranial metastasis may be clues for the prospective diagnosis of glioblastoma multiforme.