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  • Updated 11.08.2020
  • Released 06.30.1999
  • Expires For CME 11.08.2023

Carotid-cavernous fistulas

Introduction

Overview

Carotid-cavernous fistulas are abnormal connections between the cavernous sinus and the internal carotid artery, external carotid artery, their branches, or both. There are 2 broad categories of carotid-cavernous fistulas—direct and indirect—each of which has a markedly different clinical presentation. In this article, the author discusses the clinical presentation, pathogenesis, and methods of diagnosis for this disease entity. This article provides an in-depth review of the current treatments for carotid-cavernous sinus fistulas, including the endovascular repair via transarterial or transvenous embolization.

Key points

• Carotid-cavernous sinus fistulas are communications between the cavernous sinus and the carotid arterial system.

• “Direct” carotid-cavernous sinus fistulas are abnormal communications between the internal carotid artery and the cavernous sinus, whereas “indirect” carotid-cavernous fistulas are aberrant connections between the branches of either the internal or external carotid arterial system or both and the cavernous sinus.

• “Direct” carotid-cavernous sinus fistulas are typically caused by head trauma or a ruptured cavernous carotid aneurysm and present in a dramatic fashion with proptosis, ophthalmoplegia, and loss of vision. “Indirect” or “dural” carotid-cavernous fistulas typically present in elderly women with hypertension in a more subtle fashion. Most of the time, both types of carotid-cavernous sinus fistulas can be closed successfully with modern neuro-interventional techniques.

Historical note and terminology

Carotid-cavernous fistulas are abnormal communications between the cavernous sinus and the carotid arterial system, which includes the internal carotid artery, external carotid artery, and their meningeal branches. Historically, carotid-cavernous fistulas have been classified into 2 broad categories: direct and indirect. “Direct” or “high flow” carotid-cavernous fistulas are defined as direct connections between the internal carotid artery and cavernous sinus, whereas “indirect” or “dural” carotid-cavernous fistulas are characterized by connections between the meningeal branches of the internal carotid artery or external carotid artery and the cavernous sinus. A more specific anatomical-angiographic classification for carotid-cavernous fistulas was proposed by Barrow and colleagues who differentiated between 4 types of carotid-cavernous fistulas (06). Type A is a direct fistula between the cavernous internal carotid artery and cavernous sinus and is most often caused by a traumatic tear in the arterial wall or a rupture of an cavernous carotid aneurysm.

Direct carotid-cavernous fistula, type A
Anterior-posterior projection left. Lateral projection right. Early filling of the veins can be seen before any of the distal vascular is opacified. (Courtesy of Dr. Kim Rickert.)

Type B is a fistula between meningeal branches of the internal carotid artery and cavernous sinus. Type C is a fistula between meningeal branches of the external carotid artery and cavernous sinus. Type D is a fistula between meningeal branches of both the internal carotid artery and external carotid artery and the cavernous sinus.

Carotid-cavernous fistula, type D: digital angiography of the external and internal carotid artery
(Left) Anterior-posterior view of an external carotid injection. The branches of the external carotid can be seen filling the cavernous sinus. (Right) Lateral view of a left internal carotid injection in the same patient, also sho...

Thus, the traditional “direct” carotid-cavernous fistula is equivalent to a Type A carotid-cavernous fistula, whereas “indirect” (or “dural”) carotid-cavernous fistulas encompass Types B, C, and D. This classification gives the treating physician a more precise anatomical guideline on which treatment can be based.

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