A 66-year-old woman presented with bilateral gritty sensation and throbbing eye pain starting 4 months earlier. She was initially treated as a corneal abrasion related to dry eye, with no improvement. The pain was associated with left exophthalmos and red-eye without loss of vision. Ophthalmological examination revealed “corkscrew” appearance of conjunctival vessels.
CT angiography revealed enlargement and early enhancement of left cavernous sinus (CS) and superior ophthalmic vein (SOV) with tortuous morphology, compatible with carotid-cavernous sinus fistula.
Digital subtraction angiography confirmed the diagnosis, demonstrating several arterial branches from both left external carotid artery (ECA) and internal carotid artery (ICA), but mainly from right ICA, communicating with the left cavernous sinus.
Due to the multiplicity of the arterial side of the fistula, a transvenous approach from the inferior petrosal sinus (IPS) was decided. Thus, after the super-selective catheterization of left IPS, a gradual occlusion of the affected cavernous sinus with several platinum coils was achieved. Post-embolization DSA showed total occlusion of the fistula which was also confirmed by the subsidence of both clinical and ophthalmological manifestations.
Carotid-cavernous fistulas (CCFs) are abnormal communications between the CS and ICA or between CS and dural branches of ICA and/or ECA. Approximately 70% of all CCFs are caused by trauma, while the remaining 30% represent spontaneous CCFs .
The intracavernous hypertension is considered the major factor in the pathogenesis of CCFs. Draining and receiving drainage CS veins show congestion and revised blood flow (e.g. SOV, cortical veins) [2–6]. The symptomatology depends on the reflux capacity of the regional veins, the ostium size and the drainage pattern . Anterior drainage is associated with orbital/ophthalmological symptoms (pulsatile exophthalmos, orbital bruit, and chemosis). Posterior and cortical drainage is associated with neurological symptoms (headache, confusion, diplopia) or intracranial haemorrhage [8,9].
Several CCFs classifications exist depending on their aetiology (traumatic, spontaneous), blood flow (high, low) and anatomy (direct, indirect). According to Barrow classification, a CCF can derive from a direct communication between ICA and CS (type A) or indirect between meningeal branches of ICA and CS (type B), ECA branches and CS (type C) or meningeal branches of both ICA and ECA (type D) . It is the most used and is based on the angioarchitecture of the CCFs arterial side. Thomas et al. proposed another validated CCFs classification according to venous drainage, one that overcomes the limitations of Barrow classification demonstrating better correlation with clinical symptoms and treatment planning [11,12]. According to Thomas classification, CCFs with posterior/inferior drainage only, posterior/inferior and anterior drainage, anterior drainage only, and retrograde drainage into cortical veins with/without other drainage channels were designated as types 1, 2, 3, and 4, respectively. CCFs involving a direct connection between ICA and CS were designated as type 5 .
Non-invasive imaging modalities (CT/CT angiography (CTA), MR/MR angiography (MRA), Doppler) are used as the initial work-up of a possible CCF. Color Doppler imaging shows characteristic SOV findings (dilatation, increased velocity, arterial pulsation and reversal of blood flow direction), suggesting that Doppler can help not only in the diagnosis but also in the follow-up of patients with CCFs [13,14]. CT/CTA findings include proptosis, extraocular muscle enlargement, SOV dilatation and tortuosity. Nonetheless, the most significant imaging findings are the synchronous to ICA enhancement of CS as well as its enlargement . MR/MRA findings are similar with the addition of orbital oedema and abnormal flow voids in the affected cavernous sinus. Nevertheless, digital subtraction angiography (DSA) is the gold standard for the diagnosis, classification, and planning of endovascular intervention of CCFs. DSA is able to dynamically evaluate the blood-flow through CS determining CCF drainage pattern and detect small feeding arteries or the exact site of the communication .
Management options include observation, surgery, stereotactic radiosurgery and endovascular repair. The latter is considered the mainstay therapy for definitive treatment of CCFs . Two routes of endovascular approach exist, transarterial and transvenous. Direct CCFs are treated with transarterial or transvenous coil obliteration of CS or deployment of a flow diverter stent. In indirect CCFs, the transvenous route is preferred as it shows better outcomes .
The final decision to treat with a trans-arterial or transvenous approach should be made after assessment of both clinical and imaging/angiographic findings.
Take-Home Message / Teaching Points
CCFs are pathological entities that should be suspected in the appropriate clinical setting.
DSA remains the gold standard for the definitive diagnosis, classification and treatment planning.
Endovascular approach demonstrates the most effective clinical outcome as the primary CCFs treatment option but should be tailored for each patient based on the characteristics of the CCFs.
Written informed patient consent for publication has been obtained.
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