Cavernous sinus arteriovenous fistula
What is it?
A cavernous sinus arteriovenous fistula is a communication between arteries and veins that shunts blood forward into the orbit under high pressure. . This makes the conjunctival vessels engorged, and may cause swelling of the eyelids and proptosis.
Cavernous sinus AV fistulas may be caused by head trauma or may occur spontaneously, especially in postmenopausal women. Low-flow fistulas may close without treatment; high-flow fistulas may require endovascular plugging procedures.
How does it present?
The patient complains of a chronically red eye that may be painful. The conjunctival vessels have a characteristic "corkscrew" enlargement that spirals toward the cornea. Sometimes there is eyelid edema, proptosis, elevated intraocular pressure, and even ocular misalignment from pressure on ocular motor nerves in the cavernous sinus.
The turbulent flow in the fistula causes some patients to hear a "whooshing" sound synchronous with their pulse.
What to do?
Refer nonurgently to an ophthalmologist for confirmation of the diagnosis. Management may involve endovascular embolization done by a radiologist.