Which clinical triad is MOST characteristic of a direct carotid-cavernous fistula?

• A Painless non-pulsatile proptosis, normal intraocular pressure, and choroidal folds
• B Painful ophthalmoplegia, ptosis, and steroid responsiveness
• C Pulsatile proptosis, orbital bruit, and corkscrew episcleral vessels ✓
• D Progressive enophthalmos, horizontal diplopia, and infraorbital numbness

Explanation

A direct carotid-cavernous fistula shunts arterial blood into the cavernous sinus, raising venous pressure and producing pulsatile proptosis, an audible orbital bruit, dilated corkscrew episcleral veins, raised intraocular pressure, and chemosis. Option A describes idiopathic orbital inflammation with mild signs. Option B describes Tolosa-Hunt syndrome, which is steroid responsive. Option D describes a blowout fracture pattern. The combination of pulsation plus bruit localises the lesion to an arteriovenous shunt.

Reference: Kanski's Clinical Ophthalmology, 10th ed.

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