Specific Imaging Findings

Symmetric bilateral thalamic edema (hypodense on CT, hypointense on T1, and hyperintense on T2-weighted images), which may extend into the basal ganglia, midbrain, and adjacent deep white matter, is the characteristic imaging finding in DCVT. Unilateral thalamic involvement has also been reported Thalamic hemorrhage is common, and intraventricular hemorrhage can also be seen. On DWI, the areas of edema will usually demonstrate increased ADC (compatible with vasogenic edema), rather than reduced diffusion typically seen in arterial infarctions.

Thrombus is usually evident within the affected vessels, primarily internal cerebral veins, which appear hyperdense on unenhanced CT, with reported sensitivity and specificity of this “attenuated vein sign” at 99-100%. On MRI, venous thrombus will appear iso- to hyperintense to brain on unenhanced T1-weighted images, with loss of normal flow voids on T2-weighted images. Time-of-flight MR venography (MRV) will demonstrate absence of normal flow-related signal within the thrombosed veins; however, in some cases, time-of-flight MRV may appear falsely negative due to high signal from thrombus simulating normal flow. Contrast-enhanced CT or MRV will demonstrate a filling defect. Thrombosis of the superficial dural sinuses can also be present.

Pertinent Clinical Information

Patients with DCVT tend to present with a short history (usually less than a week), most commonly of headache and reduced consciousness. D-dimer levels have low positive predictive value, but they are useful in ruling out cerebral venous thrombosis, given their high negative predictive value. Predisposing conditions include genetic or acquired prothrombotic disorders, cancer, pregnancy and puerperium, and oral contraceptive use.