Imaging features of medulloblastoma CT features of medulloblastoma - medulloblastomas often appear as a mass arising from the vermis - effacement of the fourth ventricle / basal cisterns and obstructive hydrocephalus. - hyperdense on CT - cysts formation/necrosis is common - Enhancement MRI T1 hypointense to grey matter T1 C+ (Gd) enhancely heterogenously T2/FLAIR hyperintense to grey matter heterogeneous due to calcification, necrosis and cyst formation surrounding oedema is common DWI/ADC high DWI signal ("restricted diffusion") - due to their hypercellularity MR spectroscopy elevated choline decreased NAA