The pattern of bilateral thalamic low density strongly suggests internal cerebral vein thrombosis.  This may be apparent on non contrast enhanced CT as increased density.  MRI or CTA/CTV can confirm the diagnosis.  In this case there is a complex DAVF, with the presentation precipitated by internal cerebral vein thrombosis, confirmed by the lack of opacification on venous phase of bilateral carotid and vertebral angiography. More commonly deep venous "infarction" follows spontaneous internal cerebral vein thrombosis.