6 Natural History of Arteriovenous Fistulas, Clinical Presentation, and Indications for Treatment
Dural arteriovenous fistulas (dAVFs) are direct shunts between dural arteries and a dural venous sinus or cortical veins. dAVFs present with a variety of symptoms dependent on location and venous drainage patterns. The Borden and Cognard classification systems are commonly used to categorize and risk-stratify dAVFs. The natural history of dAVFs depends primarily on the presence or absence of cortical venous drainage (CVD) coupled with clinical symptoms and location. In the absence of CVD, patients rarely present with neurological deficit or hemorrhage. The presence of CVD leads to a higher risk of future neurological deficit and intracranial hemorrhage. For Borden type II dAVFs, the annual rate of hemorrhage is 6%. For Borden III dAVFs, the annual rate of hemorrhage is 10%. Combining Borden type II and III dAVFs, the annual rate of hemorrhage is 2% for asymptomatic patients, 10% for patients with nonhemorrhagic neurological deficits, and 46% for patients with a history of hemorrhage. Immediate endovascular or surgical treatment of dAVFs with symptomatic CVD is always warranted, while treatment for dAVFs with asymptomatic CVD is nearly always justifiable. Treatment is also reasonable for dAVFs without CVD but with debilitating symptoms.
Keywords: dural arteriovenous fistula, natural history, intracranial hemorrhage
- Dural arteriovenous fistulas (dAVFs) may present with a variety of symptoms dependent on location and venous drainage patterns.
- The Borden and Cognard classification systems are commonly used to categorize and risk-stratify dAVFs.
- The natural history of dAVFs depends primarily on the presence or absence of cortical venous drainage (CVD) coupled with clinical symptoms and location.
- The presence of CVD leads to a higher risk of future neurological deficit and potentially fatal intracranial hemorrhage.
- Immediate endovascular or surgical treatment of dAVFs with symptomatic CVD is always warranted, while treatment for dAVFs with asymptomatic CVD is nearly always justifiable. Treatment is also reasonable for dAVFs without CVD but with debilitating symptoms.
Cranial dural arteriovenous fistulas (dAVFs) are complex vascular lesions that involve direct shunts between dural arteries and a dural venous sinus or cortical veins. The etiology of most dAVFs is idiopathic, although they can occur after trauma, tumor invasion of sinus, infection, and postcraniotomy.1 The presenting signs and symptoms depend largely on dAVF location and type of venous drainage patterns. While some dAVFs are discovered incidentally, many present with symptoms such as headache, pulsatile tinnitus, orbital symptoms, neurological deficit, and intracranial hemorrhage (ICH).2 The natural history and subsequent risk of neurological deficit or ICH highly depend on the presence or absence of cortical venous drainage (CVD).1,2,3,4,5,6,7,8,9,10,11 The symptomatology at presentation and knowledge of the natural history of a patient’s dAVF can help guide clinical decision making.
The aim of this chapter is to review the literature on the natural history of different subtypes of dAVFs, focusing chiefly on the risk of neurological deficit and ICH to aid in the therapeutic decision-making process.
6.2 Materials and Methods
Published peer-reviewed literature regarding the natural history of dAVFs, including those specifically describing the effects of presentation, location, and venous drainage patterns on the risk of nonhemorrhagic neurological deficit (NHND) and ICH, was reviewed. The Borden and Cognard classification systems were primarily used to frame this discussion.4,5 Lastly, illustrative cases were used to highlight the presenting symptoms and classification systems.
6.3.1 Classification Systems
The Borden and Cognard classification systems stratify dAVFs on angiographic findings based on the venous drainage patterns and risk of ICH over time (► Table 6.1).4,5 In the Borden system, classifications are based on the location of venous drainage and presence of CVD.4 Borden type I dAVFs drain directly into a dural venous sinus without CVD, Borden type II dAVFs drain into a dural venous sinus and have cortical venous reflux, and Borden type III dAVFs have direct CVD. Subtypes in the Borden classification are subtype A (single fistula) and subtype B (multiple fistulas).
Table 6.1 Classification systems for dAVFs
In the Cognard system, classifications are based on the direction of dural sinus flow, presence of CVD, and venous architecture.5 Cognard type I dAVFs drain into a dural venous sinus with antegrade flow and without CVD. Cognard type IIa dAVFs drain into a dural venous sinus with retrograde sinus flow but without CVD. Cognard type IIb dAVFs drain into a dural venous sinus with antegrade flow but with CVD, while Cognard type IIa + b dAVFs drain into a dural venous sinus with retrograde flow and CVD. Cognard type III dAVFs have direct CVD (similar to Borden type III), while Cognard type IV dAVFs have direct CVD and venous ectasia. Lastly, Cognard type V dAVFs have direct CVD into spinal perimedullary veins.
A third classification system warrants discussion as it describes a specific type of dAVFs of the cavernous sinus (CS). Barrow et al stratified carotid-cavernous fistulas (CCFs) by fistulous vessels.12 Type A CCFs are direct, high-flow fistulas between the internal carotid artery (ICA) and CS, type B CCFs are indirect, low-flow fistulas between dural branches of the ICA and the CS, type C CCFs are indirect, low-flow fistulas between dural branches of the external carotid artery (ECA) and CS, and type D CCFs are indirect fistulas between dural branches of both the ICA and ECA and the CS.
Borden type I and Cognard type I and IIa are frequently combined in the literature because of the absence of CVD (► Fig. 6.1 and ► Fig. 6.2). Similarly, Borden type II and Cognard type IIb and type IIa + b (► Fig. 6.3) as well as Borden type III and Cognard types III – V(► Fig. 6.4, ► Fig. 6.5, ► Fig. 6.6) are combined because of the presence of CVD.
Fig. 6.1 This 60-year-old man presented with occipital headaches and right-sided pulsatile tinnitus. Cerebral angiography revealed a Borden type I, Cognard type IIa dAVF of the right sigmoid sinus and jugular bulb with supply from the ECA (a), occipital artery, ascending pharyngeal artery, and vertebral artery dural branches (b). Retrograde dural venous sinus drainage was observed (*); however, there was no evidence of CVD. The patient’s symptoms were not debilitating, and he was managed medically.
Fig. 6.2 This 43-year-old man presented with chronic debilitating left pulsatile tinnitus and history of deep venous thrombosis. Cerebral angiography revealed a Borden type I, Cognard type I left transverse-sigmoid dAVF with multiple ECA feeding arteries. There was no retrograde venous drainage or CVD; however, relatively a high grade stenosis (*) of the left sigmoid sinus and proximal jugular vein and high flow through the fistula created venous congestion. The patient was treated and radiographically cured via staged transarterial embolization with Onyx and transvenous embolization with Onyx and coils. His tinnitus completely resolved immediately after treatment.
Fig. 6.3 This 70-year-old patient presented cognitive decline and seizures. Cerebral angiography revealed a Borden type II, Cognard type IIa + b right transverse-sigmoid dAVF fed by the right occipital and middle meningeal arteries with evidence of cortical venous reflux (*). The patient underwent transarterial embolization with Onyx through a branch of middle meningeal artery with occlusion of the dAVF resulting in no additional cognitive decline or seizures at follow-up.
Fig. 6.4 This 68-year-old patient presented with headaches and intermittent bilateral pulsatile tinnitus. Cerebral angiography demonstrated a Borden and Cognard type III torcular dAVF with arterial feeders from bilateral occipital arteries, bilateral middle meningeal arteries, left posterior meningeal artery, and right meningohypophyseal trunk (a,b). CVD (*) occurred through the inferior vermian and right superior and inferior hemispheric cerebellar veins emptying into the straight sinus (major) and right transverse sinus (minor). Transarterial embolization with Onyx was performed via two right occipital artery branches in a single session with successful occlusion of the dAVF restoring normal venous drainage. At 18-month follow-up, there was no recurrence and the patient’s symptoms had resolved.
Fig. 6.5 This 67-year-old patient presented with transient word-finding difficulty and pulsatile tinnitus. Cerebral angiography revealed a Borden and Cognard type III left transverse-sigmoid sinus dAVF. Arterial supply occurred via the posterior auricular, middle meningeal, and occipital arteries (a) and evidence of CVD in the posterior temporal area (b,*). The patient underwent transvenous embolization of the isolated venous pouch with resolution of CVD and symptoms at follow-up.