What is the diagnostic approach for cavernous sinus thrombosis?

Diagnostic Approach for Cavernous Sinus Thrombosis

Contrast-enhanced MRI with MR venography is the gold standard for diagnosing cavernous sinus thrombosis, with CT venography serving as an acceptable alternative when MRI is unavailable or contraindicated. 1, 2

Clinical Presentation

• Key symptoms to recognize:

  • Fever and headache (most common presenting symptoms) 3
  • Ocular manifestations: chemosis, periorbital edema, ptosis, ophthalmoplegia, vision changes 3
  • Cranial nerve palsies (particularly CN VI - lateral rectus palsy, also CN III, IV, and V) 3

• Risk factors to identify:

  • Recent sinusitis or facial infection (most common etiology) 3
  • Maxillofacial trauma or surgery 3
  • Thrombophilia or hypercoagulable states 3

Diagnostic Algorithm

Step 1: Initial Imaging

• First-line imaging:

  • Contrast-enhanced MRI with MR venography (MRV) - highest sensitivity for cavernous sinus thrombosis 1, 2
  • MRI findings: absence of flow void with altered signal intensity in the cavernous sinus, T2 hypointensity suggesting thrombus, or central isodense lesion with surrounding enhancement 1
  • T2*-weighted/gradient echo/susceptibility-weighted sequences improve diagnostic accuracy 1

• Alternative if MRI unavailable/contraindicated:

  • CT venography (CTV) with IV contrast - comparable accuracy to MRV 1, 2
  • CT findings: hyperdensity of the cavernous sinus on non-contrast CT (seen in ~30% of cases), "empty delta" sign on contrast-enhanced images 1

Step 2: Laboratory Evaluation

• Complete blood count with differential
• Blood cultures (positive in up to 70% of cases) 3
• Inflammatory markers (typically elevated) 3

Step 3: Additional Imaging Considerations

• When initial imaging is inconclusive but clinical suspicion remains high:
  • Consider catheter cerebral angiography with venography 1
  • Repeat imaging if symptoms persist or worsen despite treatment 1

Diagnostic Pitfalls to Avoid

1. Misinterpreting normal anatomic variants:

   • Asymmetrical lateral (transverse) sinuses (49% of normal population) 1
   • Partial or complete absence of one lateral sinus (20% of normal population) 1
   • Normal filling defects from arachnoid granulations or intrasinus septa 1

2. Relying solely on non-contrast CT:

   • Only 30% of non-contrast head CTs are abnormal in cerebral venous thrombosis 1
   • Always proceed to venographic study (CTV or MRV) even with negative plain CT/MRI 1

3. Missing isolated mental status changes:

   • Patients may present with somnolence or confusion without obvious focal neurological deficits, especially in elderly patients or with deep venous system involvement 1

4. Overlooking atypical presentations:

   • Venous infarcts may cross arterial territories and have cortical sparing 1
   • Parasagittal or temporoparietal lesions should raise suspicion 1

5. Delayed diagnosis:

   • Early recognition and treatment are critical to reduce morbidity and mortality 2, 4
   • Presence of RAPD (relative afferent pupillary defect) at presentation is associated with worse visual outcomes and higher mortality (37.5% vs 0%) 4

Follow-up Imaging

• Follow-up CTV or MRV at 3-6 months after diagnosis to assess recanalization of occluded sinuses 1, 2
• Earlier follow-up imaging if symptoms persist or worsen despite treatment 1

Recent data shows that with modern management, mortality from cavernous sinus thrombosis has decreased to approximately 11%, though nearly one-third of patients may still experience permanent ophthalmic deficits 4.