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Carotid-cavernous fistula


Key points

  • Definition: Carotid-cavernous fistula (CCF) is an abnormal connection between the carotid artery and/or its branches and the cavernous sinus (CS).

  • Classic clue: Patient presents with an acute onset of Dandy’s triad with pulsatile proptosis, chemosis, and bruit accompanied by pain and progressive visual loss. Initial computed tomography (CT) or magnetic resonance imaging (MRI) shows enlarged CS and superior ophthalmic vein (SOV) followed by CT or catheter angiography displaying anatomy of CCF in exquisite detail.

  • CCFs may be direct (high-flow) or indirect (low-flow).

  • CCFs can be posttraumatic or spontaneous.

  • Head injuries range from minor falls to severe penetrating injuries or postsurgical damage. These cause some arterial tearing, which sooner or later can succumb to unrelenting arterial pressure.

  • Patients with traumatic CCF usually present with Dandy’s triad of pulsatile exopthalmos, chemosis, and intracranial bruit.

  • A traumatic cerebral aneurysm (TCA) by comparison is frequently asymptomatic until its fatal rupture.

  • Spontaneous CCF usually results from a ruptured cavernous carotid aneurysm.

  • CCF can be caused by congenital arteriovenous connections that spontaneously start to leak because of hypertension, atherosclerosis, collagen vascular disease, childbirth, or a combination of culprits.

  • Direct CCF results when a cavernous internal carotid artery (ICA) fistulizes into the CS.

  • Indirect CCF results when a branch of ICA or external carotid artery (ECA) communicates with CS.

Imaging

General imaging features

The clinical diagnosis of CCF may be established by hearing a bruit in the patient’s head.

  • Some suggest moving on quickly to CT angiography (CTA) or digital subtraction angiography (DSA).

  • CCFs fall into four types:

Type I: Direct CCF

  • High-flow connection between ICA and CS.

  • Secondary to trauma or ruptured ICA aneurysm.

  • Acute presentation with pulsatile exopthalmos, chemosis, and carotid sinus syndrome.

Types II, III, IV: Dural CCF

  • Low-flow fistulas between meningeal branches of carotid artery and CS.

  • Less symptomatic than direct CCF. Computed Tomography

Features

  • Proptosis (see Figure 28-1 , D and E ).

    FIGURE 28-1 ■, A, Axial NECT shows dilated, tortuous left SOV and asymmetrically enlarged left CS. Old right temporal lobe infarct. B, Axial CECT fills dilated, tortuous left SOV and CS. Attenuation matches the mildly enlarged contralateral CS. C, Axial CECT shows enhancing dilated left SOV and prominent left EOMs D, Sagittal CECT shows enhancing SOV displacing superior rectus muscle cranially. E, Sagittal CECT shows enhancing SOV displacing superior rectus muscle with exopthalmos. SOV is associated with very enlarged CS. F, Three-dimensional (3D) reconstruction of CTA shows premature abnormal filling of CS and grossly dilated SOV during arterial phase of CTA. This is clearly a CCF. G and H, 3D reconstruction of CTA demonstrates circle of Willis. Approximately 6 × 12 mm aneurysm protrudes posteriorly and laterally from the left cavernous ICA.

  • Enlarged SOV (see Figure 28-1 , A through E ).

  • Enlarged CS.

  • Extraocular muscles (EOMs) may be enlarged ( Figure 28-1 , C ).

  • Orbital edema.

  • Dilated superficial veins are an ominous sign of cortical venous drainage.

  • May show subarachnoid hemorrhage (SAH) or intracranial hemorrhage (ICH) from ruptured cortical vein.

Magnetic resonance imaging features

  • Dilation of one or both CSs and SOVs.

  • Flow-related enhancement of dilated CS and SOV in patient with proptosis.

  • “Dirty” appearing retroorbital fat.

    • Proptosis ( Figure 28-2 , B and C ).

      FIGURE 28-2 ■, A, Coronal T1 Gd shows orbital edema with increased enhancement in EOMs and other orbital soft tissues L > R. B and C, Axial T1 Gd shows increased orbital edema with enhancement in EOMs and other orbital soft tissues L > R. Abnormal choroidal enhancement is better appreciated on these images.

    • Enlarged SOV.

    • Enlarged CS.

    • Enlarged EOMs.

    • Orbital edema ( Figure 28-2 , A through C ).

    • Choroidal enhancement ( Figure 28-2 , B and C ).

    • Dilated superficial veins are an ominous sign of cortical venous drainage.

    • May develop SAH or ICH from ruptured cortical vein.

    • May show flow void related to cavernous ICA aneurysm.

Ultrasound features

  • Grayscale imaging shows anechoic superior orbital vascular mass corresponding to SOV.

  • Color flow Doppler may show high-velocity turbulent bidirectional flow within dilated SOV.

CTA/DSA features

  • Rapid shunting from ICA to CS causes immediate opacification during arterial phase of injection from a direct CCF ( Figure 28-1 , F ).

  • Enlarged draining veins.

  • Retrograde flow from cavernous sinus, commonly into ophthalmic veins, particularly SOV.

Clinical issues

Presentation

  • Acute onset of symptoms.

  • Pulsatile orbital bruit invariable.

  • Increased intraocular pressure (IOP).

  • Oculomotor nerve palsy.

  • Clinical symptoms correlate with extent of venous drainage.

  • Intracranial hemorrhage is associated with drainage into cortical veins.

  • Intracavernous aneurysm can cause epistaxis, CCF, or SAH.

  • CCF drainage into SOV causes exopthalmos, dilated conjunctival vessels with conjunctival injection.

Symptoms

  • Diplopia.

  • Decreased visual acuity.

  • Pulsatile tinnitus.

  • Proptosis.

Epidemiology

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