[Spontaneous carotid-cavernous fistula: correlations between clinical findings and venous drainage]

Abstract

We reviewed retrospectively 6 cases of spontaneous carotid cavernous fistulas to discuss the differences in clinical findings depending on venous patterns. Orbit US was performed in all patients but one and all patients were examined with CT and intraarterial digital subtraction angiography (DSA). Orbit US, performed in 5 patients with ocular signs, showed dilation of the ophthalmic veins, in 3 cases bilaterally. CT was performed to demonstrate possible lesions of the orbit apex or skull base and showed dilation of the superior ophthalmic vein in 4 patients, bilateral in only one case. Moreover, CT detected enlargement of the cavernous sinuses in 4 cases (3 unilateral, one bilateral). Dynamic CT, performed in 2 patients, showed early opacification of both cavernous sinuses. DSA was carried out on the basis of clinical data and US and CT findings. It diagnosed carotid cavernous fistulas in all cases. The fistulas were bilateral in 3 subjects. In all the patients with exophthalmos, conjunctival chemosis and dilated episcleral veins, the superior ophthalmic vein was the main venous drainage from the cavernous sinus. Only 4 of these patients had abducent nerve palsy; bruit was present in 2 cases only. The ocular signs were contralateral to the fistula in one patient. In the patient presenting III, IV and VI nerve palsy, the venous drainage was direct from the cavernous sinus to pericarotid plexus, pterygoid plexus and inferior petrosal sinus; in this case there were no ocular signs. The clinical findings of spontaneous cavernous fistulas are caused by the arterial supply and, especially, by the venous drainage of the fistula; for the early diagnosis and treatment it is important to know that some patients do not exhibit the classic triad of symptoms, characterized by pulsating exophthalmos, bruit and conjunctival chemosis. Our experience has confirmed that spontaneous carotid cavernous fistulas may be characterized by atypical clinical findings, such as ocular signs contralateral to the fistula side or palsies of cranial nerves only.