Large venous malformation of the vein of Gallen, showing early arterial filling on the MRA. It is fed by the right posterior circulation as we see the right PCA (posterior cerebral artery) and SCA (superior cerebellar artery) significantly prominent in caliber, the basillar artery and both vertebral arteries are also prominent. The direct feeding branches are mainly the posterior choroidal and thalamoperforating arteries, both branches of the right PCA. The draining venous sinuses namely the straight, right transverse and sigmoid sinuses are also prominent. The T2 and FLAIR scans show diffuse prominence of the cortical and parenchymal arterial circulation as well as associated cerebral atrophy and abnormal white matter signal and gliosis denoting chronic global cerebral ischemia. These changes are most likely due to hyperdynamic shunting with steel phenomenon. Interestingly the subcortical and periventricular patches of gliosis are showing mrginal enhancement on post contrast study likley due to sever gliosis and ongoing ischemia together with the abnormal cerebral hemodynamics.