MRI of the brain demonstrates a large heterogeneous mass centred in the fourth ventricle and herniating out of the left foramen of Luschka. It is mostly isointense to the adjacent cerebellum on T1 weighted images, hyperintense on T2 (with areas of higher signal / cystic change), and without significant restricted diffusion. Post contrast images demonstrate vivid but heterogeneous contrast enhancement.
There is no surrounding oedema, and although the fourth ventricle is effaced there are no features to suggest significant hydrocephalus on the images provided.