What is the test of choice for diagnosing sinus thrombosis infection?

Diagnostic Imaging for Sinus Thrombosis Infection

MRI with MR venography (MRV) is the test of choice for diagnosing sinus thrombosis infection due to its superior sensitivity and specificity compared to other imaging modalities. 1, 2

Imaging Options and Their Utility

First-Line Imaging

• MRI with MRV:
  • Highest sensitivity (92.5%) and specificity (100%) for detecting dural venous sinus thrombosis 1
  • Can detect both the thrombus and associated parenchymal changes
  • Contrast-enhanced MRV is less susceptible to flow artifacts than non-contrast MRV 1
  • Shows the "empty delta" sign (central hypodensity surrounded by contrast enhancement) 2
  • Can detect early cerebritis and meningitis better than CT 2

Alternative Options

• CT with CT venography (CTV):

  • Reasonable alternative when MRI is contraindicated or unavailable 1
  • Approximately 87% accuracy for detecting intracranial complications (vs. 97% for MRI) 2
  • Should be performed with thin sections (1-2mm) through the skull base 2
  • Shows the "empty delta" sign on contrast-enhanced images 2
  • Only about one-third of cases show direct signs of hyperdense dural sinus on non-contrast CT 2

• Conventional Cerebral Angiography:

  • Not routinely used for diagnosis 1
  • Reserved for cases where MRV/CTV results are inconclusive 1
  • Used when endovascular treatment is being considered 1

Specific MRI Protocol Recommendations

1. MRI head/orbits without and with IV contrast
2. Coverage through cavernous sinuses
3. T2*-weighted/gradient echo/susceptibility-weighted sequences
4. Diffusion-weighted imaging to detect restricted diffusion
5. MR venography 2

Key Diagnostic Findings

• MRI findings:

  • Short echo-time gradient-echo MRI with IV contrast shows "empty delta" sign 1
  • T2 prolongation in affected areas
  • Gradient-echo T1-weighted postcontrast MRI shows filling defects 1

• MRV findings:

  • Absence of flow in thrombosed sinus
  • Contrast-enhanced MRV shows filling defects within venous sinuses 2

Common Pitfalls to Avoid

1. Misinterpreting normal anatomic variants as thrombosis:

   • Asymmetrical lateral sinuses (present in 49% of normal population)
   • Partial or complete absence of one lateral sinus (present in 20% of normal population) 2

2. Relying solely on non-contrast CT:

   • Only 30% of non-contrast head CTs are abnormal in cerebral venous thrombosis 2
   • May miss early thrombosis 3

3. Flow artifacts in non-contrast MRV:

   • Can lead to false-positive diagnoses 4
   • Contrast-enhanced MRV helps reduce these artifacts 1

Follow-up Imaging

• Follow-up imaging with MRV or CTV at 3-6 months to assess recanalization 2
• Imaging beyond 6 months appears unnecessary unless relapse is suspected 5

Clinical Correlation

• Imaging should be interpreted in conjunction with clinical presentation, which commonly includes:
  • Headache (present in ~79% of patients) 3, 6
  • Focal neurological deficits
  • Seizures
  • Papilledema 3

In summary, while both MRI/MRV and CT/CTV can diagnose sinus thrombosis infection, MRI with MRV offers superior diagnostic accuracy and should be the first-line imaging modality when available. CT with CTV remains a valuable alternative when MRI is contraindicated or unavailable.