Obstructive hydrocephalus at the level of the foramen of Monro with periventricular white matter hypoattenuation consistent with transependymal CSF leakage and significant mass effect.
Multifocal nodular regions of increased attenuation surrounding the anterosuperior aspect of both lateral ventricles, third and fourth ventricles. No calcification. Superior to the mass lesion at the foramen of Monro there is a cystic component which to represent fluid within a dilated cavum septum pellucidum. Fourth ventricle is partially effaced.
Conclusion: CT findings are consistent with tumour; given the hyperattenuation and pattern of spread lymphoma is favoured.