MRI
Axial T2
Axial T2
Sagittal T1 C+
Axial T1
Very large mass located centrally within the posterior fossa. It is high T2 signal and low T1 signal with only patchy contrast enhancement.
No normal vermis can be identified and the mass is likely to arise from it, completely effacing the fourth ventricle and abutting the dorsal aspect of the brainstem without convincing evidence of extension into the pons.
As a result of the mass effect on the fourth ventricle, significant obstructive hydrocephalus has developed, with transependymal oedema noted particularly around the frontal and occipital horns.