How to evaluate for cavernous sinus thrombosis or aneurysm?

Evaluation of Cavernous Sinus Thrombosis or Aneurysm

Contrast-enhanced MRI with MR venography (MRV) for thrombosis or MR angiography (MRA) for aneurysm is the gold standard for evaluating cavernous sinus pathology, with CT-based techniques as alternatives when MRI is contraindicated. 1

Clinical Presentation to Guide Evaluation

Cavernous Sinus Thrombosis

• Orbital symptoms: proptosis, chemosis, impaired eye movement, decreased visual acuity 1
• Neurological symptoms: severe headache, photophobia, seizures, focal neurologic deficits 1
• Associated findings: fever (if septic), cranial nerve palsies (especially III, IV, VI, V1) 1

Cavernous Sinus Aneurysm

• May present with cranial neuropathies
• Potential concomitant Horner's syndrome
• Associated with facial pain due to proximity to trigeminal nerve 1
• May cause venous congestion with chemosis and increased intraocular pressure 1

Diagnostic Algorithm

First-Line Imaging

1. MRI with contrast of face/sinuses/head

   • Provides superior evaluation of soft tissues and vascular structures
   • Include coverage through cavernous sinuses 1
   • For thrombosis: MRI without and with contrast plus dedicated MRV 1
   • For aneurysm: MRI without and with contrast plus dedicated MRA 1

2. CT with contrast (if MRI contraindicated or unavailable)

   • CT maxillofacial with IV contrast to evaluate sinuses and orbital complications 1
   • CT head with IV contrast to assess for intracranial complications 1
   • For thrombosis: CT venography (CTV) 1
   • For aneurysm: CT angiography (CTA) 1

Key Imaging Features

Cavernous Sinus Thrombosis

• On MRV: filling defect within sinus lumen or complete nonfilling 1
• On direct venography: "cupping appearance" within sinus in complete thrombosis 1
• Contrast-enhanced MRI: more accurate than CT for detecting cavernous sinus thrombosis (97% vs 87% accuracy) 1

Cavernous Sinus Aneurysm

• MRA/CTA: demonstrates aneurysm morphology and relationship to surrounding structures
• Evaluate for potential mass effect on adjacent cranial nerves 1
• Assess for potential pseudoaneurysm formation in traumatic cases 1

Special Considerations

When to Consider Advanced Imaging

• Direct cerebral venography: during endovascular therapeutic procedures for thrombosis 1
• Cerebral angiography: for definitive evaluation of aneurysms or when pseudoaneurysm is suspected 1
• Balloon test occlusion with xenon/CT cerebral blood flow study: for treatment planning of cavernous aneurysms to assess collateral circulation 2

Potential Pitfalls

• Anatomic variants may mimic sinus thrombosis (sinus atresia/hypoplasia, asymmetrical drainage) 1
• Flow gaps on time-of-flight MRV can be misinterpreted as thrombosis 1
• Asymmetrical lateral sinuses are common (49% of normal population) 1
• Partial/complete absence of one lateral sinus occurs in 20% of normal population 1

Recommendations Based on Clinical Scenario

• For suspected septic cavernous sinus thrombosis: Immediate contrast-enhanced MRI with MRV; evaluate adjacent sinuses for source of infection 3
• For suspected traumatic aneurysm: CTA or MRA with attention to skull base fractures that may have caused vascular injury 4
• For patients with bilateral symptoms: Evaluate both sides thoroughly as complications can occur bilaterally 5

Remember that cavernous sinus pathology requires prompt diagnosis and treatment to prevent serious complications including permanent vision loss, stroke, or death.