Partial Steal Phenomenon in the Ophthalmic Artery Due to a Direct Carotid–Cavernous Sinus Fistula

Received March 24, 2003, from the Department of Radiology, Social Security Ankara Hospital (B.Y., I.C., H.O., B.H.), and Social Security Eye Hospital (G.A.), Ankara, Turkey. Revision requested April 19, 2003. Revised manuscript accepted for publication May 13, 2003. Address correspondence and reprint requests to Bahar Yanik, MD, Olgunlar Sokak 45/13, TR-06660 Kucukesat, Ankara, Turkey. Abbreviations CCF, carotid–cavernous sinus fistula; CS, cavernous sinus; ECA, external carotid artery; ICA, internal carotid artery; OA, ophthalmic artery; RI, resistive index; SOV, superior ophthalmic vein carotid–cavernous sinus fistula (CCF) is an abnormal communication between the carotid arterial system and cavernous sinus (CS). This condition often results from a head trauma or spontaneous vascular rupture.1 Anatomically, these fistulas can be classified into 3 categories: direct, indirect, and mixed. The direct type is characterized by a fistula between the internal carotid artery (ICA) and the CS and is often a result of trauma. The indirect type, also known as a dural shunt, shows a communicating flow between the meningeal branches of either the ICA or external carotid artery (ECA) and the CS. This type arises spontaneously in elderly patients with systemic hypertension and atherosclerosis and possibly secondary to a previous sinus thrombosis or thrombophlebitis. The mixed type, with contributions from both the ICA and ECA, has also been reported.2 A CCF usually causes orbital signs and symptoms according to the size and location of the lesion. Anterior segment changes include chemosis and engorged episcleral and conjunctival blood vessels and signs of anterior segment ischemia. Posterior segment changes include vascular engorgement or central retinal vein occlusion, which eventually leads to permanent loss of visual acuity. Proptosis is typically pulsatile, associated with a bruit and a thrill.3 Orbital color Doppler imaging has been used in the investigation of various vascular orbital diseases, including CCF. Reversal of flow and pulsatility in the waveform pattern of the superior ophthalmic vein (SOV) have been reported previously.4 Although the relevant literature reveals limited information about a steal phenomenon in ophthalmic arteries (OAs) of patients with dural arteriovenous fistulas, to our knowledge, the partial steal phenomenon in the OA has not been described.5–7 In this report, we describe color Doppler imaging findings and give a physiologic explanation of the partial steal phenomenon in the OA of a patient with a direct CCF.