Specific Imaging Findings

The cavernous sinus (CS) ipsilateral to the side of the carotid-cavernous sinus fistula (CCF) is typically enlarged with prominent contrast enhancement, and bilateral CS enlargement may be seen. T2-weighted MR images usually show abnormal flow voids within the CS, which may communicate with the cavernous internal carotid artery (ICA). Abnormal hyperintense flow is also present adjacent to the cavernous ICA on TOF MRA and the fistula site may be observed with other high resolution 3D MRI techniques and, usually to a better advantage, with CTA. Asymmetric and/or diminished pituitary gland enhancement may sometimes be observed. Additional imaging findings are primarily intraorbital: enlarged superior ophthalmic vein (SOV), thickened bulky extraocular muscles, proptosis, and intraorbital edema. Signs of intracranial venous congestion with engorged vessels and cerebral venous hypertension with white matter T2 hyperintensity may be present. Definite diagnosis is with cerebral DSA.

Pertinent Clinical Information

Most cases of CCF are post-traumatic, including rare iatrogenic causes (such as trans-sphenoidal surgery and Gasserian ganglion ablation). Based on the nature of the fistula, CCF is divided into direct and indirect types. Direct CCF is a high-flow lesion and the typical clinical presentation includes the triad of exophthalmos, bruit, and conjunctival chemosis. Diplopia (caused by ophthalmoplegia from compression of the cranial nerves), headache, retroorbital pain, development of glaucoma and decreasing visual acuity may be present in advanced cases. Indirect CCF is a dural arteriovenous fistula (DAVF) and may be of a low-flow or a high-flow variety.