Carotid-cavernous fistula

A carotid-cavernous fistula (CCF) results from an abnormal communication between the arterial and venous systems within the cavernous sinus in the skull. It is a type of arteriovenous fistula. As arterial blood under high pressure enters the cavernous sinus, the normal venous return to the cavernous sinus is impeded and this causes engorgement of the draining veins, manifesting most dramatically as a sudden engorgement and redness of the eye of the same side.

Causes
Carotid cavernous fistulae may form following closed or penetrating head trauma, surgical damage, rupture of an intracavernous aneurysm etc or in association with connective tissue disorders, vascular diseases and dural fistulas.

Classification
Many types of classification have been proposed for CCF, based on the anatomy, pathophysiology and aetiology. They may be divided into low-flow or high-flow, traumatic or spontaneous and direct or indirect. One of the most popular classifications divides CCF into four varieties depending on the type of arterial supply.

Symptoms and presentation
While CCF is not a lethal disease, its symptoms can be disabling and include bruit (a humming sound within the skull due to high blood flow through the arteriovenous fistula), progressive visual loss, and proptosis or progressive bulging of the eye due to dilatation of the veins draining the eye.

Patients usually present with sudden or insidious onset of redness in one eye, associated with proressive proptosis or bulging.

They may have a history of similar episodes in the past.

Diagnosis
This is based on MRI scan with MRA/MRV, CT angiogram and a cerebral DSA.