Carotid-Cavernous Fistula

What's going on?

There is an abnormal communication between the carotid artery and the cavernous sinus. High-pressure, high-flow blood enters the sinus and causes marked dilatation. The venous vasculature of the orbit cannot drain effectively and the orbit becomes engorged. The eye becomes red and proptosed. The oculomotor nerves run through or close to the cavernous sinus, and thus a third, fourth or sixth nerve palsy is common. Vision may be compromised, and patients usually have pain.

This condition is often related to trauma but can occur sporadically in the elderly. The high-flow type is worse as there is a direct communication between the artery and the venous circulation. In the low-flow type, the connection is via the dural plexus, and the features and subsequent risks are less marked.

If I examine the patient, what will I find?

One or both eyes will be red and proptosed. If you look closely with a magnifying glass or ophthalmoscope, you will see that all of the conjunctival vessels are markedly dilated.

What if I've diagnosed it?

Such patients should be referred immediately/urgently to hospital.

What will the hospital do?

Neuro-imaging is carried out and the patient will often be referred to a neurosurgeon. An interventional radiologist may be able to occlude the aneurysm with an intravascular balloon or coil. This procedure carries significant risks of CVA.

Problems that may arise, and how to deal with them

Beware drying of the cornea due to proptosis.