Carotid-cavernous fistula

Background

• Fistula between carotid and cavernous sinus
• Majority arise from trauma
  • Exact mechanism unclear/variable, may arise from small tear in internal carotid or branches due to basilar skull fracture (esp. through sphenoid), shear forces, or abrupt increases in intraluminal pressure when compressed due to neck flexion
• May also occur spontaneously, due to aneurysms, thrombosis, or weakening in arterial wall
  • Risk factors include connective tissue disease e.g. Ehler's Danlos

Clinical Features=

• Onset typically abrupt within hours to few days after initial insult, but may present weeks after trauma
• Symptoms due to arterialization of orbital veins
• Pulsating exophthalmos/proptosis
• Raised intraocular pressure
• Eye pain (ocular and/or orbital), headache
• Chemosis
• Diplopia or blurry vision
• CN VI palsy
  • Esotropia (eye moves inwards), diplopia
• CNIII palsy
  • Exotropia (eye moves laterally)
  • Ptosis
  • Pupillary dilation
• Bruit (over eye or head)

Possible complications include:

• Acute angle glaucoma, vitreous hemorrhage, retinal detachment
  • Can lead to vision loss
• ICH, SAH (if fistula drains into cortical veins)
• Severe epistaxis

Differential Diagnosis

Bilateral red eyes

• Painful
  • Caustic keratoconjunctivitis
  • Ocular foreign body
  • Orbital trauma
  • Contact lens problems
  • Conjunctivitis
  • Blepharitis
  • Allergic reaction
  • Thyroid disease
  • Carotid-cavernous fistula
• Painless
  • Conjunctivitis
  • Blepharitis
  • Allergic reaction
  • Thyroid disease

Evaluation

• Conventional angio is gold standard, but can be seen on CT/CTA or MRI/MRA of head/orbits

Management

• 5-10% close spontaneously remainder must be closed by interventional radiology (e.g. embolization) or surgically

See Also

• Red eye, eye pain
• Head trauma
• Cranial nerve palsies