What is the differential for the intraventricular lesion, if other findings are ignored?
Intraventricular meningioma, subependymal hamartoma / subependymal giant cell astrocytoma, ependymoma, central neurocytoma (enhancement would be unusually vivid), choroid plexus papilloma (location would be unusual).
What 2mm finding remote from the main lesion makes one diagnosis almost certain?
The small focus of calcification on the lateral aspect of the body of the right lateral ventricle strongly implies that this patient has tuberous sclerosis and that the mass therefore represents subependymal hamartoma / subependymal giant cell astrocytoma.
A 2cm mass is located near the left foramen of Munro with associated ventriculomegaly, presumably due to obstruction at the level of the foramen. The mass is of soft tissue attenuation and demonstrates vivid contrast enhancement.
A single calcified subependymal focus is present on the lateral aspect of the right lateral ventricle. There is slight heterogeneity of the white matter of the cerebral hemispheres.