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Carotid Cavernous and Other Dural Arteriovenous Fistulas


Introduction

Intracranial dural arteriovenous fistulas (dAVFs) are acquired vascular lesions that usually involve the intracranial dural sinuses and comprise less than 10% of all intracranial vascular lesions . They are commonly divided into carotid cavernous fistulas (CCFs) and other dAVFs. Usually branches of the external carotid artery (ECA), internal carotid artery (ICA), or vertebral artery or a combination thereof form a direct connection with dural sinus and/or intracranial veins resulting in an arteriovenous shunt. Management is directed by symptomatology, location, and angioarchitecture of the lesion. Arterialization of intracranial veins through retrograde venous flow is classically associated with increased risk of cerebral hemorrhage.

Carotid Cavernous Fistulas

CCFs are abnormal communications between the ICA or ECA and their branches and the cavernous sinus and comprise approximately 35% of all dAVFs .

Classification

Numerous classification systems have been applied to CCFs. The simplest classification divides CCFs into direct and indirect fistulas. Direct fistulas result from a defect in the ICA wall, from trauma or rupture of a cavernous ICA aneurysm, and are usually high-flow fistulas. Indirect fistulas are low-flow fistulas and the equivalent of a dAVF of the cavernous sinus and comprise the majority of CCFs encountered in clinical practice. The most widely adopted system to classify CCFs is the Barrow classification where the angioarchitecture of the arterial side of the fistula determines type . However, the Barrow classification is not very practical from a clinical and therapeutic point as symptomatology and current treatment approach are influenced largely by venous drainage. In addition, most CCFs are indirect fistula and fall under Barrow type D since there is always some supply from meningeal branches of both ICA and ECA. One of the authors have proposed an updated five-tier classification system utilizing venous drainage, which captures symptomatology, endovascular treatment approach, and outcome ( Fig. 98.1 ; Table 98.1 ) .

Figure 98.1, Schematic illustration of the venous drainage–based classification system for carotid cavernous fistulas. Normal venous anatomy is colored light blue. Preferential drainage of the individual fistula types are colored dark red. (A–E) Types I–V, respectively. IPS , inferior petrosal sinus; SMCV , superficial middle cerebral vein.

Table 98.1
Proposed Venous Drainage–Based Classification System for Carotid Cavernous Fistulas
Reproduced with permission from Thomas A, Chua M, Fusco M, et al. Neurosurgery. © 2015 Wolters Kluwer Health, Inc.
Type Venous Drainage
Type I Posterior/inferior drainage only
Type II Posterior/inferior and anterior drainage
Type III Anterior drainage only
Type IV Retrograde drainage into cortical veins ± other routes of venous drainage
Type V High flow direct shunt between cavernous internal carotid artery and cavernous sinus (Barrow type A) ± multiple routes of venous drainage
Posterior/inferior drainage: inferior petrosal sinuses, superior petrosal sinus, pterygoid, and parapharyngeal plexus. Anterior drainage: superior and inferior ophthalmic veins. Cortical drainage: superficial middle cerebral veins, perimesencephalic, and cerebellar venous system

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