The MRI sequences demonstrate a midline mass of the posterior cerebral fossa mainly of vermian location. It appears of low signal intensity on T1WI, intermediate to high signal intensity on FLAIR and T2WI, containing cystic change/necrosis with heterogeneous enhancement following IV contrast. Moderate surrounding oedema with mass effect on the brainstem, midbrain and 4th ventricle which is laminated, and cerebellar tonsils which are herniating through the foramen magnum. Diffuse leptomeningeal seeding is noted in the infratentorial subarachnoid spaces seen as nodular and linear enhancement along the cerebellar surface.
At the supratentorial level, there is a dilatation of the 3rd and lateral ventricles with interstitial periventricular oedema, indicating obstructive hydrocephalus. A leptomeningeal seending is also noted with thick and nodular leptomeningeal enhancement at the temporal lobes, Sylvian fissures as well as the posterior interhemispheric fissure. There are multiple subependymal enhancing nodules of various size along the wall of the lateral ventricles, indicating intraventricular metastasis. Note also others signs of the increased intracranial pressure (tortuosity of the optic nerves, enlarged subarachnoid spaces around the optic nerves, flattening of the posterior sclera, and empty sella turcica)