How do you diagnose cavernous sinus venous thrombosis?

Diagnosing Cavernous Sinus Thrombosis

MRI with MR venography (MRV) is the preferred first-line imaging modality for diagnosing cavernous sinus thrombosis (CST), as it provides the highest sensitivity and shows both thrombus and parenchymal changes. 1

Clinical Presentation

When suspecting CST, look for these characteristic clinical features:

• Cranial nerve palsies, particularly:
  • CN VI (abducens) palsy - causing lateral rectus palsy and limited lateral gaze
  • CN III (oculomotor), IV (trochlear), and V (trigeminal) involvement
• Bilateral involvement often develops within 48 hours of initial unilateral signs
• Fever (present in nearly all cases)
• Headache
• Altered mental status
• Seizures
• Signs of increased intracranial pressure
• Proptosis and chemosis

CST should be considered in any patient presenting with multiple cranial nerve palsies, fever, and headache, as early recognition is critical for improved outcomes 1.

Diagnostic Imaging Algorithm

First-Line Imaging:

1. MRI with MRV:
   • Highest sensitivity for CST diagnosis
   • Shows absence of flow in thrombosed dural venous sinus
   • Better visualization of superficial and deep venous systems
   • Superior detection of early ischemic changes
   • No radiation exposure
   • Better detection of cortical and deep venous thrombosis
   • Superior detection of micro/macrobleed 1

Alternative First-Line Option:

1. CT with CT Venography (CTV):
   • Useful when MRI is contraindicated or when MRI artifacts are suspected
   • Quick (5-10 minutes)
   • Readily available
   • Fewer motion artifacts
   • Usable with pacemakers or in patients with claustrophobia
   • As accurate in diagnosis of CVT as MRV 2, 1

Imaging Findings Suggestive of CST:

On MRI/MRV:

• "Empty delta" sign within the thrombosed sinus or vein on contrast-enhanced images
• Absence of flow in thrombosed dural venous sinus 1

On CT/CTV:

• "Empty delta" sign (lack of enhancement within the affected venous structure)
• Increased density and distension of thrombosed sinus on unenhanced CT 1
• Only 30% of noncontrast head CT examinations are abnormal in the setting of cerebral venous thrombosis 2

Important Diagnostic Considerations

1. Initial Evaluation:

   • Noncontrast CT of the head is essential in the initial evaluation to assess for hemorrhagic complications and alternative etiologies 2
   • However, it has limited sensitivity for direct visualization of CST

2. Catheter-Directed Angiography:

   • Infrequently necessary due to the sensitivity and specificity of CTV and MRV
   • May be useful to assess potential endovascular treatment targets in cases of progressive infarct despite adequate medical therapy 2

3. Follow-up Imaging:

   • Early follow-up CTV or MRV is recommended for patients with persistent or evolving symptoms despite medical treatment
   • Follow-up imaging at 3-6 months after diagnosis is reasonable to assess recanalization 1

Complications to Look For on Imaging

• Hemorrhagic infarction (occurs in approximately 40% of cases)
• Hydrocephalus (occurs in approximately 10% of cases)
• Extension to other venous sinuses (lateral dural venous sinuses and superior sagittal sinus) 1

Common Pitfalls to Avoid

1. Delayed Diagnosis: CST is frequently misdiagnosed due to its rarity. Maintain a high index of suspicion in patients with characteristic clinical features 3.

2. Relying Solely on Noncontrast CT: Only 30% of noncontrast head CT examinations are abnormal in the setting of cerebral venous thrombosis 2.

3. Missing Underlying Causes: Always look for potential sources of infection, particularly:

   • Facial or sphenoid sinus infections
   • Otitis media/mastoid infections
   • Bacterial meningitis 3

4. Overlooking Atypical Presentations: Isolated sixth-nerve palsy or hypo/hyperesthesia of the fifth nerve may be the only presenting signs 3.

Despite modern treatment, CST carries significant morbidity, with less than half of patients recovering completely, and mortality rates of approximately 30% 1. Early diagnosis through appropriate imaging is crucial for improving outcomes.