MRI Protocol for Cortical Venous Thrombosis
For diagnosing cortical venous thrombosis, obtain MRI with T2-weighted susceptibility imaging (gradient-echo or susceptibility-weighted imaging) combined with MR venography (MRV), using both time-of-flight and contrast-enhanced sequences.* 1, 2
Optimal MRI Protocol Components
The most sensitive imaging approach requires multiple complementary sequences:
- T2*-weighted susceptibility imaging (T2*SW or gradient-echo) is the single most critical sequence, demonstrating 90% sensitivity for detecting cortical vein thrombus from day 1-3, with stable sensitivity throughout the first week 3, 4
- MR venography (MRV) should include both noncontrast time-of-flight (TOF) and contrast-enhanced sequences, as they provide complementary information 2
- Contrast-enhanced 3D gradient-echo T1-weighted imaging achieves 92.5% sensitivity and 100% specificity, superior to unenhanced MRV alone (89.6% sensitivity, 91.8% specificity) 5
Why This Combination Matters
T2-weighted sequences are particularly crucial for cortical venous thrombosis specifically*, detecting 97% of thrombosed cortical veins even when magnetic resonance venography shows no visible occlusion 3. This is critical because isolated cortical venous thrombosis is identified much less frequently than sinus thrombosis and can be easily missed 1.
Standard sequences like T2-weighted, FLAIR, and diffusion-weighted imaging detect fewer than 40% of cortical vein thromboses 3. T1-weighted spin-echo detects 78% but is still inferior to T2*-weighted imaging 3.
Additional Useful Sequences
- T1-weighted images (pre- and post-contrast) help identify the "empty delta sign" and assess thrombus age 1
- T2-weighted and FLAIR images detect parenchymal changes (edema, hemorrhage, venous infarction) better than CT, visualizing focal edema in 25% versus 8% on CT 1
- Diffusion-weighted imaging (DWI) may show restricted diffusion, though findings are less pronounced than in arterial infarction 1
Alternative When MRI Unavailable
If MRI is contraindicated or unavailable in an emergency setting, multidetector CT with CT venography (CTV) is an acceptable alternative, showing 95% sensitivity and 91% specificity 1, 2. However, CT has poor detection of cortical and deep venous thrombosis compared to MRI 1.
Common Pitfalls to Avoid
- Acute thrombus can appear hypointense on T2-weighted images, mimicking normal flow void* 1. This is why combining multiple sequences is essential.
- Relying on conventional sequences alone misses most cortical vein thromboses - T2*-weighted imaging is non-negotiable 3, 4
- The "cord sign" (irregular signals in thrombotic cortical veins on T2-weighted images) may not be visible on initial imaging*, particularly without susceptibility-weighted sequences 1
- Signal intensity of venous thrombus varies with time: isointense on T1 and hypointense on T2 in the first week (deoxyhemoglobin), then hyperintense on both by the second week (methemoglobin) 1
Clinical Context
The American Heart Association recommends this imaging approach for acute or subacute onset of symptoms in emergency or ambulatory settings, particularly when deep or cortical venous thrombosis is suspected 1. MRI is superior to CT at every stage after thrombosis for detecting cerebral venous thrombosis 2.