Neurointervention · IR Playbook

Endovascular Treatment of Carotid–Cavernous Fistula (CCF)

Endovascular closure of an abnormal communication between the carotid arterial system and the cavernous sinus, performed transvenously, transarterially or by direct puncture. The fistula arterialises the cavernous sinus, so venous pressure rises and drainage reverses into the superior ophthalmic vein and, in a minority, into cortical veins; every symptom and every hazard of the disease follows from which outflow pathway is carrying the arterialised blood. Because the disease is one of venous outflow, treatment must close the fistulous point itself rather than merely obstruct an outflow channel, and the commonest catastrophic error is occluding drainage while the shunt still flows. Technical closure exceeds 90 percent for direct fistulae and is achieved in the large majority of indirect fistulae, with cranial nerve palsy the commonest complication and haemorrhage from cortical venous reflux the most feared.

Learning objectives

• Classify a cavernous shunt by Barrow type from the angiographic feeders and select the corresponding treatment route
• Identify cortical venous reflux and revise the urgency and the sequence of the procedure when it is present
• Navigate the inferior petrosal sinus and recognise when an alternative venous or direct route is required
• Recognise the objective angiographic endpoints of fistula closure and distinguish them from mere flow reduction
• Manage worsening orbital congestion, cranial nerve palsy and intracranial haemorrhage after embolisation

Indications

• Direct Barrow type A fistula from trauma or from rupture of a cavernous internal carotid artery aneurysm
• Any fistula with cortical venous drainage, irrespective of symptom severity, because of the haemorrhage risk
• Progressive visual loss, uncontrolled intraocular hypertension or retinal venous congestion
• Intolerable proptosis, chemosis, diplopia or orbital bruit failing conservative measures in an indirect fistula
• Recurrent or residual shunt after previous endovascular or surgical treatment
• Epistaxis or an enlarging pseudoaneurysm arising from a traumatic direct fistula

Absolute contraindications

• No safe arterial, venous or direct route to the fistulous point after full angiographic assessment
• Active untreated infection along the planned direct orbital or facial venous access

Relative contraindications

• Uncorrected coagulopathy or thrombocytopenia in a non-urgent indirect fistula
• Severe contrast allergy or contrast-limiting renal impairment when the shunt is asymptomatic
• An asymptomatic indirect fistula without cortical venous reflux, where spontaneous or compression-induced closure remains reasonable
• Anatomy in which the only venous access would obliterate the sole ophthalmic outflow before the shunt can be closed

Equipment

• 6 Fr arterial and 6-8 Fr venous 11 cm femoral sheaths
• 5 Fr diagnostic catheters for six-vessel angiography with a 0.035 inch hydrophilic guidewire
• 6 Fr guide catheter or 088 long sheath for the internal jugular vein
• 5-6 Fr guide catheter for the internal carotid or external carotid artery for road map and control runs
• 0.017 inch coil-compatible microcatheter and a 0.021 inch microcatheter for larger coils
• Dimethyl sulfoxide compatible detachable-tip microcatheter for liquid embolic
• 0.014 inch shapeable and hydrophilic microwires
• Detachable platinum coils in framing, filling and finishing sizes
• Onyx 18 and Onyx 34 with dimethyl sulfoxide and a dedicated injection set
• Compliant balloon catheter for internal carotid artery protection
• Covered stent and flow diverter available on the shelf for direct fistulae
• Biplane angiographic suite with three-dimensional rotational and cone-beam capability
• Heparin, protamine and activated clotting time monitoring

Procedure steps

1. Perform bilateral internal carotid, external carotid and vertebral injections with prolonged venous phases. Identify the exact fistulous point, every arterial feeder, and every draining channel including any cortical vein, because the route, the urgency and the endpoint all follow from this run. Use ipsilateral carotid compression during vertebral injection or contralateral injection during compression when a high-flow direct shunt obscures the tear.Pearl: Compression manoeuvres slow a high-flow direct shunt just enough to localise the tear that is invisible on an uncompressed run.
2. Place a 6 Fr sheath in the right common femoral artery and a 6-8 Fr sheath in the right common femoral vein under ultrasound guidance. The arterial limb is retained throughout for road maps and control runs even when the treatment is entirely transvenous.
3. Advance a guide catheter into the internal or external carotid artery to give the working road map, and a guide catheter or long sheath into the internal jugular vein at the level of the jugular bulb. Give heparin to an activated clotting time of 250 to 300 seconds for transarterial work; reduce or withhold it when cortical venous reflux is present and haemorrhagic risk outweighs thromboembolic risk.Pearl: A stable jugular guide at the bulb converts the inferior petrosal sinus from an unsupported reach into a short, supported push.
4. Under road map from the arterial injection, direct a 0.014 inch microwire and microcatheter medially and anteriorly from the jugular bulb into the inferior petrosal sinus. Watch the wire tip stay within the contrast-defined channel and advance only while the wire moves freely; resistance with tip deformation means the wire is in a dural cul-de-sac or against the clivus rather than in the sinus. The step is complete when the microcatheter tip lies within the posterior cavernous compartment and a gentle hand injection opacifies the fistulous point.Pearl: An angiographically occluded inferior petrosal sinus is frequently still traversable, so failure of the sinus to opacify is not by itself a reason to abandon the route.
5. If the inferior petrosal sinus cannot be crossed, attempt the contralateral inferior petrosal sinus through the intercavernous sinus, the superior petrosal sinus, the pterygoid plexus, or the facial and angular veins into the superior ophthalmic vein. Choose the route that reaches the compartment receiving the shunt, confirmed by test injection, and abandon a route once two wire and catheter shapes have failed rather than persisting into perforation.Pearl: The angular vein is superficial at the medial canthus and can be compressed manually to redirect a wire that repeatedly enters facial tributaries.
6. Standard textbook technique: with oculoplastic assistance, expose the superior ophthalmic vein through a small superomedial eyelid crease incision and cannulate it directly, or puncture the cavernous sinus percutaneously through the inferior orbital fissure under fluoroscopic and cone-beam guidance. Confirm the position with a hand injection showing the cavernous compartment before any device is delivered.Pearl: Cone-beam computed tomography acquired after the needle is sited confirms the intracavernous position before committing coils, when plain fluoroscopy is ambiguous.
7. Deploy detachable coils into the venous compartment immediately adjacent to the fistulous point, framing first and then filling, with repeated arterial control runs after every few coils. Watch the shunt slow and the ophthalmic and any cortical outflow disappear before the residual sinus is packed. Stop packing when arterial injection shows no early cavernous filling, not when the sinus appears full on plain fluoroscopy.Pearl: Packing tightly at the fistulous point and loosely elsewhere achieves closure with the least coil mass against the cranial nerves.
8. Where a residual dural shunt persists within a coil mass, inject Onyx through a dimethyl sulfoxide compatible microcatheter within the coil interstices, using Onyx 34 when flow remains brisk. Watch for reflux along the microcatheter and for any cast approaching the internal carotid artery or the ophthalmic artery territory, and stop immediately if either occurs.Pearl: The coil mass acts as a scaffold that holds the liquid embolic at the fistulous point instead of allowing it to be washed into the venous outflow.
9. For a Barrow type A fistula not closed transvenously, cross the tear with a microcatheter and coil the venous pouch with a compliant balloon inflated across the defect in the internal carotid artery, or exclude the tear with a covered stent. Deflate the balloon intermittently and confirm carotid patency and absence of coil prolapse on each control run. Practice varies: flow diversion is used where a ruptured cavernous aneurysm is the cause and immediate closure is not required.Pearl: Balloon inflation across the defect both protects the carotid lumen and stabilises the first framing coil so that it does not prolapse.
10. Repeat internal carotid, external carotid and, where relevant, vertebral injections through the full venous phase. The endpoint is absent early cavernous opacification, absent cortical venous reflux and a widely patent internal carotid artery. A slow residual dural blush without cortical reflux may be accepted and reviewed rather than pursued into a hazardous additional injection.
11. Remove the sheaths with manual compression or a closure device once the activated clotting time permits, then examine pupils, visual acuity, eye movements and limb power before the patient leaves the table or as soon as the anaesthetic is reversed.Pearl: A documented on-table examination separates a new deficit caused by the procedure from a pre-existing one and directs immediate imaging.

Complications

• Intracranial haemorrhage from cortical venous reflux
• Acute visual loss
• Thromboembolic stroke
• Venous perforation during navigation
• Cranial nerve palsy
• Transient worsening of orbital congestion
• Coil or embolic migration
• Recurrent or residual fistula
• Access site haematoma or pseudoaneurysm

Exam pearls

• The Barrow classification divides cavernous shunts into direct type A from an internal carotid artery tear and indirect types B, C and D fed by internal carotid dural branches, external carotid dural branches or both.
• Cortical venous drainage in a carotid-cavernous fistula is an indication for treatment irrespective of ocular symptoms, because it carries a risk of intracranial haemorrhage.
• Occluding venous outflow before the fistulous point is closed diverts arterialised blood anteriorly and cortically, and is the commonest avoidable cause of acute visual loss or haemorrhage during transvenous treatment.
• An angiographically occluded inferior petrosal sinus can usually still be catheterised, so non-opacification is not a reason to abandon the transvenous route.
• The abducens nerve lies free within the cavernous sinus rather than in its lateral wall, making it the cranial nerve most often affected by shunt pressure or coil mass.
• An ophthalmic artery arising from the middle meningeal artery must be excluded before external carotid feeder embolisation, since inadvertent occlusion causes irreversible blindness.

Viva questions

A patient with an indirect cavernous shunt has minimal proptosis but the angiogram shows filling of the superficial middle cerebral vein. How does that change your plan?

Cortical venous reflux carries a risk of parenchymal haemorrhage that is independent of ocular symptoms, so the lesion moves from elective observation to prompt treatment. The plan also changes intraprocedurally, because heparinisation is moderated and the fistulous point must be closed before any outflow is sacrificed.

You are coiling transvenously and the shunt is only partly closed, but the patient's proptosis worsens acutely on the table. What has happened and what do you do?

Posterior outflow has been occluded while arterial inflow persists, so arterialised blood has been diverted anteriorly into the superior ophthalmic vein. The correct response is to continue and complete closure of the fistulous point rather than to stop, because stopping leaves the orbit exposed to the full shunt pressure.

Why is the inferior petrosal sinus still attempted when it fails to opacify on the venous phase?

Angiographic non-opacification usually reflects chronic thrombosis or diversion of flow rather than obliteration of the channel, and the sinus remains navigable with a wire and microcatheter in a large proportion of such cases. Abandoning the route on the venous run alone forfeits the safest and most direct access.

Which arterial anatomy must you exclude before injecting liquid embolic into a middle meningeal artery feeder, and why?

An ophthalmic artery arising from the middle meningeal artery, and dangerous anastomoses between the internal maxillary or ascending pharyngeal arteries and the internal carotid or vertebral circulations. Injecting without excluding these risks central retinal artery occlusion with blindness, or reflux into the cerebral circulation with stroke.

You have completed coiling and the ipsilateral internal carotid run shows no cavernous filling. Is the case finished?

No. The endpoint requires external carotid and, where relevant, contralateral and vertebral injections through the full venous phase, because indirect fistulae are frequently supplied from multiple territories. A single ipsilateral run can appear clean while an external carotid feeder continues to shunt.

A young man with a traumatic direct fistula has a pseudoaneurysm at the tear. Why does this alter your technique?

Coils placed into an unsupported pseudoaneurysm cavity will prolapse into the carotid lumen and embolise distally. A compliant balloon inflated across the defect or a covered stent is used to stabilise the framing coil and protect the carotid lumen during deployment.

Why is the sixth nerve the one most often affected after transvenous coiling, and what does that tell the patient about prognosis?

The abducens nerve travels freely within the cavernous sinus rather than in its lateral wall, so it is directly exposed to the coil mass. The palsy is usually a compressive and transient phenomenon and the majority recover over weeks to months, which allows conservative management with orthoptic support.

When is internal carotid artery sacrifice acceptable in a direct fistula, and what must precede it?

It is a last resort when the fistula cannot be closed with carotid preservation and the shunt threatens vision or life. It must be preceded by balloon test occlusion demonstrating adequate cross-flow and clinical tolerance, because sacrifice without this assessment risks a large territorial infarct.

References