Background: Imaging criteria of medulloblastomas and ependymomas were defined retrospectively to allow a preoperative differential diagnosis of these malignant tumors of the posterior fossa.
Patients and methods: CT and/or MR-studies of 103 patients with medulloblastomas and 19 ependymomas treated in the HIT'91-trial were centrally reviewed. Evaluation concerned the origin, CT-density or MR-signal intensity, enhancement, internal structural homogeneity and results of staging of the tumors.
Results: Medulloblastomas and Ependymomas showed different results concerning all imaging criteria.
Conclusion: On the basis of differences in localisation, enhancement and tumor growth in most cases a preoperative differential diagnosis between medulloblastomas and ependymomas is possible. Increased density on CT allows the differentiation of the malignant tumors from pilocytic astrocytomas of the fourth ventricle.