Carotid Cavernous Fistula

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  • Direct Fistula
    • High-flow arteriovenous fistula between internal carotid artery and cavernous sinus
    • Usually occurs after trauma or ruptured aneurysm
  • Indirect Fistula
    • Low-flow arteriovenous fistula between meningeal branches of internal/external carotid artery and cavernous sinus
    • Mostly spontaneous, associated with arterial hypertension, atherosclerosis, connective tissue weakness, congenital malformations
    • Less pronounced findings than direct fistula

Clinical Presentation

  • Usually less pronounced in indirect fistula compared to direct fistula
  • Visual impairment: either as a direct result of trauma or secondary to changes in the eye (IOP, retina, etc.)
  • Conjunctival corkscrew vessels, conjunctival chemosis
    • Caution: may be misdiagnosed as conjunctivitis
  • Pulsating exophthalmos , possibly with a rhythmic swooshing or whooshing noise inside the head
    • Audible with a stethoscope; pressure on the carotid artery reduces the sound
    • Can mimic thyroid eye disease or nonspecific orbital inflammation
  • Increased intraocular pressure: typically increased pulse amplitude, consider measuring with Pascal tonometer
    • Due to elevated episcleral venous pressure, +/- blood in Schlemm’s canal
    • Caution: may be misdiagnosed as asymmetric glaucoma
  • Double vision with involvement of N. III / IV / VI in the cavernous sinus, possibly Horner syndrome
  • Fundus with congested veins, possible haemorrhages/macular edema/central vein occlusion/optic disc swelling


  • MR angiography (MRA) / CT angiography (CTA): thickened superior ophthalmic vein, possibly thickened eye muscles, fistula visible in angiography
  • Doppler ultrasound: flow reversal and arterialisation in the superior ophthalmic vein


  • Spontaneous closure possible in indirect cases, rarely in direct cases
  • Catheter-guided endovascular coil embolization or balloon embolization for direct fistulas


  • Carotid cavernous fistula by Dr. Andrew G. Lee
  • EyeWiki Carotid Cavernous Fistula
  • Kanski‚Äôs Clinical Ophthalmology: A Systematic Approach; John E Salmon MD; Elsevier; 9th Edition (2019)
  • Review of Ophthalmology: Neil J. Friedman; Peter K. Kaiser; William B. Trattler; Elsevier, 3rd Edition (2018)
  • The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Nika Bagheri MD, Brynn Wajda MD, et al; Lippincott Williams&Wilkins; 7th Edition (2016)