Carotid-cavernous fistula: current concepts in aetiology, investigation, and management

Abstract

A carotid-cavernous fistula (CCF) is an abnormal communication between arteries and veins within the cavernous sinus and may be classified as either direct or dural. Direct CCFs are characterized by a direct connection between the internal carotid artery (ICA) and the cavernous sinus, whereas dural CCFs result from an indirect connection involving cavernous arterial branches and the cavernous sinus. Direct CCFs frequently are traumatic in origin and also may be caused by rupture of an ICA aneurysm within the cavernous sinus, Ehlers-Danlos syndrome type IV, or iatrogenic intervention. Causes of dural CCFs include hypertension, fibromuscular dysplasia, Ehlers-Danlos type IV, and dissection of the ICA. Evaluation of a suspected CCF often involves non-invasive imaging techniques, including standard tonometry, pneumotonometry, ultrasound, computed tomographic scanning and angiography, and/or magnetic resonance imaging and angiography, but the gold standard for classification and diagnosis remains digital subtraction angiography. When a direct CCF is confirmed, first-line treatment is endovascular intervention, which may be accomplished using detachable balloons, coils, liquid embolic agents, or a combination of these tools. As dural CCFs often resolve spontaneously, low-risk cases may be managed conservatively. When invasive treatment is warranted, endovascular intervention or stereotactic radiosurgery may be performed. Modern endovascular techniques offer the ability to successfully treat CCFs with a low morbidity and virtually no mortality.

Figure 1

(a) Gross anatomic coronal section through the cavernous sinuses demonstrates the concept of a direct CCF on the left (asterisk). Open arrows delineate the left cavernous sinus. The locations of the cranial nerves within the cavernous sinus (solid arrows) emphasize the relative vulnerability to injury of the abducens nerve, which lies in the body of the cavernous sinus adjacent to the cavernous portion of the ICA. 3=oculomotor nerve, 4=trochlear nerve, V1=ophthalmic division of the trigeminal nerve, V2=maxillary division of the trigeminal nerve, 6=abducens nerve, VN=vidian nerve. (b) Gross anatomic axial section showing branches of the cavernous portion of the ICA. One or more of these branches may participate in dural CCFs.

Figure 2

External photograph of a patient with a red left eye and mild left proptosis (inset) from a left-sided CCF.

Figure 3

Left eye conjunctival and episcleral injection in a patient with a left-sided CCF. Inset shows that the injection is due to tortuous vessels containing arterial blood (ie, arterialized vessels).

Figure 4

Patient with marked left eye injection, chemosis, and proptosis from a left-sided dural CCF. The patient also has left ptosis and a dilated left pupil, consistent with an ocular motor nerve paresis caused by the fistula.

Figure 5

Left ptosis, exotropia, and dilated pupil caused by a left oculomotor nerve paresis in a patient with a left-sided dural CCF. Note bilateral dilation of conjunctival and episcleral vessels.

Figure 6

Left sixth nerve palsy in a patient with left-sided dural CCF.

Figure 7

Pneumotonometry measurements in a patient with a right dural CCF reveal an ocular pulse amplitude of 6 mm Hg OD compared with 2 mm Hg OS. The difference in ocular pulse amplitude between the two eyes is 4 mm Hg, supporting the diagnosis of a CCF.

Figure 8

Axial computed tomographic scan (left) and postcontrast magnetic resonance image (right) show enlargement of the left SOV in a patient with a left-sided, anteriorly draining, CCF.

Figure 9

Selective left internal carotid arteriogram (lateral view) shows a dural CCF with drainage both anteriorly and posteriorly.

Figure 10

Successful closure of a dural CCF using a transvenous approach via the SOV. Prior to treatment, the common carotid arteriogram shows a dural CCF draining both anteriorly and posteriorly (left). After treatment, there are multiple platinum coils present within the fistula (middle). Post-procedure common carotid arteriogram shows obliteration of the fistula with intact flow in the ICA (right).

Figure 11

Improvement in visual manifestations after successful endovascular closure of direct (a, b) and dural (c) CCFs. (a, b) Pretreatment (a) and post-treatment (b) appearance of a patient with a post-traumatic right direct CCF. (c) Post-treatment appearance of the patient whose pretreatment appearance is seen in Figure 4.