What investigations should be sent for a patient with suspected cortical vein thrombosis?

Investigations for Suspected Cortical Vein Thrombosis

For suspected cortical vein thrombosis, immediately obtain neuroimaging with CT venography or MR venography, along with complete blood count, D-dimer, coagulation screen (PT/aPTT), and fibrinogen level. 1

Initial Laboratory Testing

Essential blood work includes:

• Complete blood count to assess platelet count and identify thrombocytopenia 1
• D-dimer measurement - while a normal D-dimer (using sensitive immunoassay or rapid ELISA) may help identify low-probability cases, an elevated D-dimer is common but non-specific; a normal result should not preclude further evaluation if clinical suspicion remains high 1
• Coagulation screen including prothrombin time (PT) and activated partial thromboplastin time (aPTT) 1
• Clauss fibrinogen assay to assess for consumptive coagulopathy 1
• Blood film to confirm true platelet abnormalities and exclude alternative diagnoses 1

Neuroimaging Studies

Diagnostic imaging is critical and should be performed urgently:

• CT venography or MR venography is recommended as first-line imaging to confirm cortical vein thrombosis 1
• MRI with venography is the standard diagnostic tool and superior for detecting isolated cortical vein thrombosis 1, 2
• Catheter angiography (DSA) should be considered if non-invasive venography is inconclusive but clinical suspicion remains high 1
• Plain CT or MRI may show the "cord sign" (hyperdense thrombosed vein) or associated hemorrhage, but venographic sequences are essential for definitive diagnosis 1

Screening for Underlying Causes

Evaluate for prothrombotic conditions and precipitating factors:

• Vaccination history - particularly recent COVID-19 vaccination to assess for vaccine-induced immune thrombocytopenia and thrombosis (VITT) 1
• Anti-PF4 antibody ELISA if VITT is suspected (thrombocytopenia with D-dimer >2000-4000 μg/mL FEU within 5-30 days of vaccination) 1
• Screen for infections and inflammatory conditions that may predispose to thrombosis 1
• Contraceptive use history and other medication exposures 1
• JAK2 V617F mutation testing should be considered, as myeloproliferative disorders can be found in up to 13% of cerebral venous thrombosis cases 1

Special Considerations

Important caveats in the diagnostic workup:

• D-dimer levels decline with time from symptom onset, so patients with subacute or chronic presentations may have false-negative results 1
• Lumbar puncture is not routinely indicated unless meningitis is suspected; it does not help confirm the diagnosis when imaging is available 1
• Repeat platelet count in 2-3 days if initial count is normal but clinical suspicion remains high, as 5% of VITT patients have initially normal platelets that subsequently fall 1
• Thrombophilia testing (protein C, protein S, antithrombin, factor V Leiden, prothrombin G20210A) is generally not recommended acutely as it rarely alters immediate management and results are affected by acute thrombosis and anticoagulation 3, 4, 5, 6

Timing and Urgency

Same-day imaging is essential when clinical suspicion is high, as cortical vein thrombosis can extend bidirectionally to involve dural sinuses and cause rapid neurological deterioration 1, 2

The diagnostic approach should prioritize rapid confirmation of thrombosis to enable immediate anticoagulation, which is the cornerstone of treatment even in the presence of hemorrhagic transformation 1, 2