In what compartment is this abnormality located?
It is hard to tell. The two options are intraventricular or intraparenchymal (or both). In any case it is supratentorial.
Why is the right lateral ventricle enlarged? What supports that this is acute?
The outflow of the lateral ventricle at the foramen of Munro is obstructed by the left sided mass. There is thus acute obstructive hydrocephalus. Transependymal oedema suggests that at least a component is acute.
Digitized images from printed film. A large, heterogeneous mass is present within the left frontal lobe. It is strikingly hyperdense, without definite calcification. The solid component enhances. Hydrocephalus is present, best seen on the right, due to outflow obstruction.