MRV Imaging for Suspected CVST
For suspected cerebral venous sinus thrombosis, order MRV both without and with IV contrast—the combination of time-of-flight (TOF) and contrast-enhanced MRV provides the highest diagnostic accuracy and addresses the complementary limitations of each technique. 1
Optimal Imaging Protocol
The ideal MRV protocol includes both non-contrast TOF and contrast-enhanced sequences performed together. 1 This combined approach is superior because:
Contrast-enhanced MRV is the most accurate single technique for CVST diagnosis 1, but has a critical limitation: T1 isointense thrombus can mimic normal sinus opacification, leading to false negatives 1
TOF MRV mitigates against this pitfall by detecting T1 isointense thrombus that would be missed on contrast-enhanced imaging alone 1
Contrast-enhanced MRV better evaluates hypoplastic sinuses with slow flow, which can appear falsely thrombosed on TOF sequences 1
T1 hyperintense thrombus can mimic normal flow patterns, making non-contrast MRI sequences essential for accurate interpretation 1
Supporting Evidence from Research
The 2024 ACR Appropriateness Criteria explicitly state that MRV "ideally consists of both noncontrast TOF and contrast-enhanced MRV" because these techniques are complementary 1. Research supports this recommendation:
A 2016 study found that 3D T1-weighted contrast-enhanced sequences had the highest diagnostic performance (AUC 77-81%) among routine MRI sequences 2
A 2010 study demonstrated that combined dynamic and static contrast-enhanced 4D MRV achieved excellent accuracy (AUC 0.99) for dural sinus thrombosis 3
A 2007 comparative study showed contrast-enhanced 3D MRV had superior sensitivity (85.7%) and specificity (97.2%) compared to 2D TOF alone (71.4% sensitivity, 55.6% specificity) 4
When Non-Contrast MRV Alone May Be Acceptable
If findings on non-contrast TOF MRV are unclear or equivocal, you must proceed to contrast-enhanced imaging 1. The AHA/ASA guidelines recommend that "a venographic study (either CTV or MRV) should be performed in suspected CVT" without specifying contrast requirement, but emphasize that lack of thrombus identification on contrast-enhanced MRV helps clarify diagnosis 1.
Additional Imaging Considerations
Add gradient echo T2 susceptibility-weighted imaging to improve diagnostic accuracy (Class IIa recommendation) 1. This sequence helps:
- Distinguish hypoplastic sinuses from thrombosed sinuses (non-thrombosed hypoplastic sinuses lack abnormal low signal) 1
- Detect cortical vein thrombosis, where GRE showed the highest sensitivity (66%) in research studies 3
Volumetric MRI sequences are essential for contrast-enhanced MRV, and delayed post-contrast imaging can further increase sensitivity for T1 isointense thrombus 1.
Common Pitfalls to Avoid
Flow gaps are commonly seen on TOF MRV and can be misinterpreted as thrombosis in normal anatomic variants (49% have asymmetrical transverse sinuses, 20% have partial/complete absence of one lateral sinus) 1
Never rely on plain MRI alone—a negative plain MRI does not rule out CVST (Class I recommendation) 1
Sinus signal-intensity variations affect interpretation, making the combination of sequences critical for accurate diagnosis 1
If MRV remains inconclusive despite optimal imaging, catheter cerebral angiography is reasonable (Class IIa recommendation) 1