CT scan in CVT

Q; 32 years old recently postpartum patient presented with severe headache. Neuroradiologist called with concern for cerebral venous thrombosis (CVT). Which three radiological signs on a CT scan raise the concern for CVT?

Answer:

In CVT, history plays a pivotal role. Females are three times more prone to develop CVT due to a higher risk in a few situations, such as the postpartum period. Symptoms usually lead to a CT scan of the head as the first test. It may show focal areas of edema or venous infarction, cortical or juxtacortical hemorrhage, diffuse brain edema, and hyperdensities suggestive of venous occlusion.

A clinician should look for three signs:

• Dense triangle sign – triangular or round hyperdensity on a cross-section at the site of a sinus.
• Empty delta sign (also called the empty triangle or negative delta sign) – triangular hyperdensity surrounding a hypo-/iso-dense central region within the superior sagittal sinus on head CT performed with contrast.
• Cord sign – a curvilinear or linear hyperdensity typically found at the surface of the cerebral cortex.

Serial CT scans can be interesting with "vanishing infarcts", where some lesions may disappear and new lesions may appear.

On the same token, another interesting phenomenon to be observed is the H:H ratio, i.e., the Hounsfield unit (HU) to hematocrit ratio. It compares the density of the blood in the dural sinuses (measured in HU) to the patient's hematocrit level. A higher H:H ratio suggests a higher likelihood of CVT. 

MRI should be performed.

As expected, consultation with neurology and neurosurgery is recommended.

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References:

1. Otite FO, Patel S, Sharma R, et al. Trends in incidence and epidemiologic characteristics of cerebral venous thrombosis in the United States. Neurology 2020; 95:e2200.

2. Lee EJ. The empty delta sign. Radiology 2002; 224:788.

3. Boukobza M, Crassard I, Bousser MG. When the "dense triangle" in dural sinus thrombosis is round. Neurology 2007; 69:808.

4. Buyck PJ, De Keyzer F, Vanneste D, et al. CT density measurement and H:H ratio are useful in diagnosing acute cerebral venous sinus thrombosis. AJNR Am J Neuroradiol 2013; 34:1568.