There is a large flow void structure in the expected anatomical location of vein of Galen and internal cerebral veins. It appears to be stealing blood from the dilated anterior and posterior circulation branches (cortical and deep branches of MCA and PCA).and draining to two dilated flow void structures, the more superior of which appears to be draining to the superior sagittal sinus, while the inferior vessel is draining to the location of confluence of sinuses (torcular herophilli).
The large anomalous vein is causing positive mass effect, associated with compression of the left thalamus, effacement of the left lateral ventricle as well as some midline shift to the right. There is mild dilatation of the lateral and third ventricles from cerebral aqueduct compression.
There are large areas of T2/FLAIR high signals in both hemispheres, especially, the left temporo-parietal and right parietal lobes. These are likely represent areas of gliosis. Several high DWI spots seen in both hemispheres scattered in the anterior as well as posterior circulation territories, they are of faintly low ADC, likely representing infarction from "steal" phenomena.
Interpretation: Findings are consistent with vein of Galen aneurysmal dilatation (VGAM), causing positive mass effect and mild hydrocephalus. Large areas of gliosis and several small regions of acute infarction are seen as a result.