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What is a carotid cavernous fistula?

A carotid cavernous fistula is a condition that develops when there is an irregular connection between the internal carotid artery and the cavernous sinus vein located behind the eye. A carotid cavernous fistula can also be due to a communication between the cavernous sinus and one or more meningeal branches of the external carotid artery, internal carotid artery or both.

Carotid cavernous fistulas can be divided into spontaneous or traumatic in relation to the cause, and direct or dural in relation to angiographic findings. Dural fistulas usually have low rates of arterial blood flow and may be hard to diagnose without the use of medical imaging (angiography)


Symptoms of a carotid cavernous fistula can be both direct and indirect. Direct carotid cavernous fistulas require more urgent attention. Indirect carotid cavernous fistulas cause fewer and far less serious symptoms, directly related to the low rate of blood flow. Symptoms for both direct and indirect carotid cavernous fistulas can include:

  • A bulging eye, which may pulsate
  • A red eye
  • An audible swish or buzz coming from your eye
  • An eye that protrudes forwards
  • Double vision
  • Headaches
  • Loss of vision
  • Nosebleeds
  • Facial pain
  • Ringing in your ears
  • Weak or missing eye movements


The most common diagnosis of a direct carotid cavernous fistula follows trauma from a basal skull fracture resulting in tear in the internal carotid artery within the cavernous sinus. Falls, automobile accidents and other injuries can contribute to the incidence of basilar skull fractures and the formation of carotid cavernous fistulas.

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