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Ocular System

Carotid-cavernous fistula (CCF)

Abnormal communication between the cavernous sinus and the carotid arterial system.

Abnormal communication between the cavernous sinus and the carotid arterial system.

Aetiology

Direct CCFs (Barrow type A):

High-flow fistulas characterized by a direct connection between the internal carotid artery (ICA) and the cavernous sinus
  • Traumatic in origin (M/C)
  • Rupture of ICA aneurysm within cavernous sinus
  • Ehlers–Danlos syndrome type IV
  • Iatrogenic intervention: transarterial endovascular intervention, internal carotid endarterectomy, percutaneous treatment of trigeminal neuralgia, trans-sphenoidal resection of a pituitary tumour, and maxillofacial surgery

Dural CCFs (Barrow types B, C, and D):

Low-flow fistulas that consist of communications between the cavernous sinus and cavernous arterial branches
  • Hypertension
  • Fibromuscular dysplasia
  • Ehlers–Danlos type IV
  • Dissection of the ICA

Classification

Barrow classification: 

Anatomical classification
  • Type A fistulas are direct connections between the internal carotid artery (ICA) and the cavernous sinus
  • Type B fistula results from dural branches of the ICA
  • Type C results from dural branches from the external carotid artery (ECA)
  • Type D result from dural branches from ICA and ECA

Clinical features

Classical triad:

  • Pulsatile proptosis
  • Chemosis
  • Bruit
This 25-year-old man presented with chief complaints of right eye proptosis, decreased vision and elevated intraocular pressure (A). Closer examination revealed dilated episcleral vessels. Based on history and imaging studies, diagnosis of CCF was made (B) | Chaudhry, I. A., Elkhamry, S. M., Al-Rashed, W., & Bosley, T. M. (2009). Carotid cavernous fistula: ophthalmological implications. Middle East African journal of ophthalmology, 16(2), 57–63. https://doi.org/10.4103/0974-9233.53862

Anteriorly draining fistulas:

More likely to cause ocular symptoms
  • Subjective bruit
  • Diplopia
  • Tearing
  • Red eye
  • Ocular foreign body sensation
  • Blurred vision
  • Headache

Posteriorly draining fistulas:

May develop neurologic symptoms
  • Confusion
  • Expressive aphasia
  • Diplopia (from isolated ocular motor nerve pareses)

Diagnosis

Pneumotonometry:

Valuable diagnostic tool
  • Difference in ocular pulse amplitudes (difference between systolic and diastolic IOP) of 1.6 mm Hg between the two eyes (100% sensitive & 93% specific for a CCF)
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. | Henderson, A., Miller, N. Carotid-cavernous fistula: current concepts in aetiology, investigation, and management. Eye 32, 164–172 (2018). https://doi.org/10.1038/eye.2017.240

Orbital ultrasound:

Can be used to exclude mimickers of CCF, including orbital tumours, dysthyroid orbitopathy, orbital inflammation, and scleritis.
  • Dilated superior ophthalmic vein (SOV)
  • Evidence of orbital congestion with enlarged extraocular muscles

Colour Doppler:

Evaluates flow velocity and direction, thus indicating arterial flow in the orbital veins in cases of CCF
  • Flow reversal in the SOV: Suggestive of a CCF

Computed tomographic angiography (CTA) or magnetic resonance angiography (MRA):

  • Unilateral/bilateral enlargement of the SOV (suggestive of CCF)
  • Orbital congestion
  • Enlargement of the extraocular muscles and periorbital fat
  • Convexity of the lateral wall of the cavernous sinus
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. | Henderson, A., Miller, N. Carotid-cavernous fistula: current concepts in aetiology, investigation, and management. Eye 32, 164–172 (2018). https://doi.org/10.1038/eye.2017.240

Digital subtraction angiography (DSA):

Gold standard for classification and diagnosis of CCF and can be both diagnostic and therapeutic
Selective left internal carotid arteriogram (lateral view) shows a dural CCF with drainage both anteriorly and posteriorly. | Henderson, A., Miller, N. Carotid-cavernous fistula: current concepts in aetiology, investigation, and management. Eye 32, 164–172 (2018). https://doi.org/10.1038/eye.2017.240

Differential diagnosis:

  • Non-specific orbital inflammation
  • Orbital hemorrhage
  • Orbital infection
  • Orbital tumor
  • Orbital vasculitis
  • Thyroid disease
  • Tumor with cavernous sinus involvement

Management

Direct CCF:

  • Endovascular intervention (first-line treatment):
    • Detachable balloons, coils, liquid embolic agents, or a combination of these tools.

Dural CCFs:

Often resolve spontaneously, low-risk cases may be managed conservatively.
  • Endovascular intervention or stereotactic radiosurgery (when invasive treatment is warranted)
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 a patient | Henderson, A., Miller, N. Carotid-cavernous fistula: current concepts in aetiology, investigation, and management. Eye 32, 164–172 (2018). https://doi.org/10.1038/eye.2017.240

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