Caroticocavernous fistulas (CCF) represent abnormal communication between the carotid circulation and the cavernous sinus. They can be classified as direct or indirect which are separate conditions with different aetiologies.
Direct CCFs are often secondary to trauma, and as such the demographics reflect the distribution of head trauma, most commonly seen in the young male patients. The presentation is acute and symptoms develop rapidly.
In contrast, indirect CCFs have a predilection for the postmenopausal female patient and the onset of symptoms is often insidious.
Other conditions that predispose to increased risk include:
- pulsatile exophthalmos: ~75% 3
- chemosis and subconjunctival haemorrhage
- progressive visual loss: 25-32% 3
- pulsatile tinnitus (usually objective)
- raised intracranial pressure
- subarachnoid haemorrhage, intracerebral haemorrhage, otorrhagia, epistaxis: ~5% 3
- cranial nerve (III, IV, Vc, VI) palsies5
It can be broadly classified into two main types:
- direct: direct communication between intracavernous ICA and cavernous sinus
- indirect: communication exists via branches of the carotid circulation (ICA or ECA)
Another method is to classify according to four main types:
- type A: direct connection between the intracavernous ICA and CS
- type B: dural shunt between intracavernous branches of the ICA and CS
- type C: dural shunts between meningeal branches of the ECA and CS
- type D: B + C
Direct: type A
A direct fistula is due to a direct communication between the intracavernous ICA and the cavernous sinus. There are a number of causes, however, aneurysm rupture and trauma are by far the most common:
- ruptured intracavernous carotid artery aneurysm
- trauma (including surgery/angiography)
- other causes include
- collagen deficiency syndromes
- fibromuscular dysplasia
- arterial dissection
Indirect: types B, C, D
Indirect fistulas are due to communication by multiple branches between the ICA/ECA and CS. The most frequent are type C, with meningeal branches of the ECA forming the fistula 3.
They are postulated to occur secondary to cavernous sinus thrombosis with revascularisation. Other predisposing factors appear to be pregnancy, surgical procedures in the region, and sinusitis 3.
- enlarged superior ophthalmic veins
- extraocular muscles may be enlarged
- orbital oedema
- may show SAH/ICH from a ruptured cortical vein
- rapid shunting from ICA to CS
- enlarged draining veins
- retrograde flow from CS, most commonly into the ophthalmic veins
- arterialised ophthalmic veins may be seen on Doppler study
Treatment and prognosis
The natural history of CCF is highly varied, ranging from spontaneous closure to rapidly progressive symptoms. Poor treatment outcome indicators include feeding vessel aneurysms (indirect CCF) and retrograde filling of cortical veins (increased risk of haemorrhage).
Direct fistulas have a relatively high spontaneous rate of haemorrhage (8.4%). This can be in the form of subarachnoid, intracerebral or external haemorrhage (epistaxis, or otorrhagia). Subconjunctival haemorrhage is also common but does not carry the same poor prognosis 3.
Treatment options include:
- carotid compression therapy
- most useful in the treatment of indirect fistulas resulting in spontaneous closure in up to 30% of cases
- only successful in 17% of direct fistulas, presumably due to the higher flow through larger defect 3
- transarterial balloon embolisation:
- treatment of choice for symptomatic direct CCF
- if not possible, detachable coils may be used
- both arterial and venous access (including superior ophthalmic vein) may be employed
- indirect fistulas typically require a combined transarterial (closure of feeders) and transvenous (closure of cavernous sinus) approach; they are more difficult to treat and have a higher rate of spontaneous closure
- surgical treatment with ligation or trapping of involved segments 3
- 1. Castillo M. Neuroradiology companion, methods, guidelines, and imaging fundamentals. Lippincott Williams & Wilkins. (2006) ISBN:0781779499. Read it at Google Books - Find it at Amazon
- 2. Bithal PK, Rath GP. Interventional Neuroradiology for Carotico-Cavernous Fistula : A Restrospective Analysis and Anaesthetic Implications. J Anaesth Clin Pharmacol 2005; 21(2) : 175-178 J Anaesth Clin Pharmacol (pdf)
- 3. Halbach VV, Hieshima GB, Higashida RT et-al. Carotid cavernous fistulae: indications for urgent treatment. AJR Am J Roentgenol. 1987;149 (3): 587-93. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Bojaniæ G et al. Carotid Cavernous Fistulas in Postenopausal Women Acta Clin Croat (2008) 47 (S1): 53-57
- 5. D Brosnahan, R M McFadzean, E Teasdale. Neuro-ophthalmic features of carotid cavernous fistulas and their treatment by endoarterial balloon embolisation.