Will a computed tomography (CT) scan of the head with contrast medium reveal a cerebral thrombosis?

From the Guidelines

CT of the head with contrast can show a cerebral thrombosis, but it is not the optimal imaging modality for this purpose. According to the most recent study 1, contrast-enhanced CT is less commonly performed than CTV in initial screening but may demonstrate the thrombus in the form of the “empty delta sign” in some cases. This is further supported by another study 1, which states that contrast-enhanced CT may demonstrate the thrombus in the form of the “empty delta sign” in some cases, allowing for assessment of the extent of thrombus.

Key Points to Consider

• CT with contrast may identify a cerebral thrombosis as a "cord sign" (hyperdense thrombus in a vein), "empty delta sign" (filling defect in the superior sagittal sinus), or through indirect signs like venous infarction or hemorrhage.
• However, CT can miss smaller thrombi or those in certain locations.
• If cerebral thrombosis is suspected clinically but CT results are negative, further imaging with MRI/MRV should be pursued, as MRI with magnetic resonance venography (MRV) is generally preferred for detecting cerebral venous thrombosis due to its superior sensitivity 1.
• The timing of the thrombosis also affects detection - acute thrombi (less than 7 days) are more likely to be visible on CT than subacute or chronic thrombi.
• In emergency situations where MRI is unavailable or contraindicated, CT with contrast remains a valuable initial screening tool, but its limitations should be recognized 1.

From the Research

CT of the Head with Contrast and Cerebral Thrombosis

• A CT of the head with contrast may show a cerebral thrombosis, but the sensitivity and specificity of this method can vary depending on the specific conditions and imaging techniques used 2, 3.
• Cerebral venous thrombosis (CVT) can be diagnosed using CT/CTV, MRI/MRV, and US, with CT/CTV being a commonly used method for initial diagnosis 2.
• The presentation of CVT on non-contrast-enhanced CT (NECT) can be non-specific and may require a high index of clinical suspicion, with signs including edema, parenchymal hemorrhage, and subarachnoid hemorrhage 2.
• CT perfusion studies can provide valuable information regarding clinical outcome in patients with CVT, with parameters such as relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), and relative mean transit time (rMTT) being used to assess prognosis 4.
• The use of quantitative imaging parameters measured on non-contrast CT, such as attenuation values and veno-arterial difference, can improve the diagnostic accuracy of CVT 3.
• CT perfusion can also improve diagnostic accuracy of ischemic stroke, particularly in anterior circulation, and can provide information on the current status of cerebral perfusion 5.

Diagnostic Accuracy

• The sensitivity and specificity of CT-based diagnosis of CVT can vary, with a study finding that an attenuation threshold value of >55 HU yielded a sensitivity of 86% and a specificity of 90% 3.
• The combination of an attenuation value greater than 55, or a veno-arterial difference greater than 22, can yield a high diagnostic performance, with sensitivity and specificity values of 86% and 100%, respectively 3.
• CT perfusion studies can provide prognostic information, with optimal threshold values for rCBF, rCBV, and rMTT correlating with better clinical outcomes 4.