Post-traumatic carotid-cavernous fistula

History: Young man undergoing workup following trauma.
Additional clinical information: One week ago, patient was in a MVA. He has orbital discoloration and proptosis. Additional workup also reveals elevated intraocular pressure.


Findings

CT shows asymmetric increased size and density of the left cavernous sinus relative to the right side. No intraparenchymal abnormalities. Angiography shows abnormal communication between the left cavernous internal carotid (C4 segment) artery and adjacent enlarged left cavernous sinus. Immediate drainage is demonstrated via the ophthalmic veins, superior/inferior petrosal sinuses, and contralateral cavernous sinus.


Diagnosis: Post-traumatic carotid-cavernous fistula


Key points

A communication between the carotid artery and the cavernous sinus is called a carotid cavernous fistula (CCF). There are two types of CCF. A direct CCF involves the internal carotid artery and the cavernous sinus. An indirect CCF involves the dural branches of the external carotid artery and the cavernous sinus.

Carotid cavernous fistulas may be post traumatic or spontaneous in presentation. Trauma usually creates a direct CCF. Aneurysms of the cavernous ICA that rupture can cause a spontaneous direct CCF. Indirect fistulas are not usually related to trauma; rather they spontaneously develop in patients with underlying diseases such as hypertension, collagen vascular disease, or atherosclerosis.

Clinical manifestations of a direct CCF include pulsating exophthalmos, orbital bruit, motility disturbance, chemosis, and glaucoma. Vision loss will occur in 90% of patients with untreated direct CCF and 20-30% of patients with untreated indirect CCF.

Therapeutic options for a CCF include endovascular embolization of the fistula or surgery. The current method for endovascular treatment involves the use of detachable silicone balloons. A deflated balloon attached to the tip of a catheter is inserted into the cavernous sinus via the carotid artery. The balloon is slowly filled with a contrast agent until the abnormal flow of blood is no longer seen on angiography. An alternate method for endovascular treatment involves thrombosing the cavernous sinus using coils. If the endovascular rout fails to correct the CCF surgery is warranted.


Radiology

CT: Proptosis, extraoccular muscle enlargement, and enlargement of the superior ophthalmic vein may be seen. Enlargement of the cavernous sinus may be seen.
MRI: Similar findings as CT. Also, abnormal flow voids in the affected cavernous sinus may be seen.
Angiography: The most accurate way to diagnose a CCF is angiography. This allows the visualization of the fistulous communication. Immediate filling of the cavernous sinus, ophthalmic veins, and petrosal sinus occurs. If the flow is rapid through the fistula then a special maneuver may be used to slow the flow in order visualize the fistula. The Huber maneuver involves selecting the ipsilateral vertebral artery and manually compressing the ipsilateral common carotid artery. This allows slow retrograde flow of contrast into the cavernous carotid artery via the posterior communicating artery.