The clinical picture of deep cerebral vein thromboses (DCVT) usually is acute, combining vigilance disorders, headaches, and focal neurologic deficit. The authors describe a patient who presented with isolated subacute dementia as the sole manifestation of DCVT. In the setting of subacute cognitive deficit, the diagnosis of DCVT must be considered when neuroimaging shows bilateral thalamic changes. Enhanced venous MR angiography is the noninvasive method of choice to ascertain the diagnosis.