Background: Posterior fossa tumors have a wide range of differential diagnosis. Accurate radiological differentiation by magnetic resonance imaging which is the imaging technique of choice in assessing the site and the extent of the tumor is important for determining the correct treatment plan.
Objectives: To evaluate the value of MRI in localization, extension, characterization, differentiation of posterior fossa masses.
Patients and methods: This was cross sectional study done at interventional and diagnostic radiology department at Qena university hospital on 50 patients with posterior cranial fossa masses. All studied cases underwent a full history taking and MRI scans of the brain in a supine position. MRI results were compared with histopathological assessment in undetermined cases.
Results: 26 (52%) cases were under 16 years old.  MRI revealed that 16 (32%) diagnosed cases as pilocytic astrocytoma, 7 (14%) as glioma, 6 (12%) each of ependymoma, acoustic neuroma, metastasis and medulloblastoma, two (4%) as meningioma and one (2%) as arachnoid cyst. On T1WI, 92% were hypointense on T1WI. On T2WI, 70% were hyperintense, whereas 16% were heterogeneous. On FLAIR, most of tumors were hyperintense (64%). On post-contrast images, the majority of the tumors showed both heterogenous post-contrast enhancement (34%) and enhanced mural nodule (30%).
Conclusion: It was found that the MRI is a golden tool in characterization of these masses as it demonstrated the extent of the tumor and the amount to which the surrounding tissues were involved, thus aiding in the management of tumors. In most cases, the histopathologic diagnosis and the MR diagnostic imaging are correlated