16 Surgical Treatment of Intracranial Dural Arteriovenous Fistulas
Abstract
Intracranial dural arteriovenous fistulas (DAVFs) are pathological vascular connections between dural arteries and dural venous sinuses, dural veins, or meningeal veins, with the shunt usually located within the dural leaflets. The venous drainage pattern is the most important predictor of clinical behavior and possibility of treatment. Nowadays, most of intracranial DAVFs can be satisfactorily treated with an endovascular approach, and surgery has become a second line of treatment. However, surgical approach is a valid therapeutic strategy in symptomatic patients who need immediate cure, or when embolization is not feasible or safe due to the risk of collateral arterial branches embolization or inability to achieve a microcatheter position close enough to the shunt to achieve effective treatment. Accordingly, certain anatomical locations may still require surgical treatment, such as anterior ethmoidal, craniocervical junction, and tentorial DAVFs. Surgical disconnection of the draining vein is an effective strategy that allows occlusion of the fistula or promotes its conversion into a less aggressive lesion. Finally, surgery can be indicated after failed initial endovascular occlusion, or in a combined strategy with endovascular treatment.
Keywords: intracranial dural arteriovenous fistulas, surgical treatment, endovascular treatment, venous drainage
Key Points
- Intracranial dural arteriovenous fistulas (DAVFs) are rare vascular lesions, though potentially the cause of intracranial hemorrhage or neurological symptoms related to venous congestion.
- With the evolution of endovascular techniques, embolization represents a safe and effective treatment modality for most of these lesions.
- Despite advances of endovascular techniques, surgery remains a valid therapeutic strategy in those patients who need immediate cure and are not amenable to safe and effective embolization.
- Because of local anatomical conditions and/or characteristics of the feeding arteries, anterior ethmoidal, craniocervical junction, and tentorial DAVFs are those anatomical location that may still require surgical disconnection even in the modern endovascular era.
- The pattern of venous drainage influences clinical behavior. Surgical disconnection of the draining vein(s) is a feasible strategy that allows the occlusion of the fistula or promotes its conversion into a more benign lesion.
16.1 Introduction and General Principles
Intracranial dural arteriovenous fistulas (DAVFs) are pathological vascular connections between dural arteries and dural venous sinuses, dural veins, or meningeal veins, with the shunt usually located within the dural leaflets. The venous drainage pattern is the most important predictor of clinical behavior, natural history, risk of hemorrhage, and possibility of treatment.1 Borden et al and Cognard et al underlined the relation between the cortical venous reflux and the clinical aggressiveness.2,3 Angioarchitecture and venous outflow, as well as the location of the DAVF, are also critical for the treatment management. Therapeutic strategies include conservative monitoring, endovascular embolization (transarterial or transvenous), surgical excision, and radiosurgery.4
With the improvement of endovascular techniques, especially the advent of Onyx, embolization of DAVFs has become the first choice, and most intracranial DAVFs can be satisfactorily treated with an endovascular approach. With this paradigm shift, surgical management has become the second line of treatment usually utilized and indicated only in a certain subset of situations. Surgery is still required for cases in need of immediate cure (because of hemorrhage or aggressive neurological symptoms) and embolization is not feasible or safe because of high risk of embolization into collateral branches or inability to achieve favorable catheter position close enough to the shunt to provide effective treatment. Surgical treatment may also be evaluated after a failed endovascular embolization attempt or in a combined strategy with endovascular treatment.
16.2 Materials and Methods
The current literature regarding the surgical treatment of intracranial DAVFs was explored. We reported the results of the published surgical series in which the surgical approach was used alone or combined with endovascular treatment. The aim of this chapter is to describe the current surgical management of the intracranial DAVFs, and report the anatomical locations and angioarchitecture characteristics for which surgery is indicated.
16.3 Results and Discussion
16.3.1 General Principles
The potential approaches of surgical treatment include (1) occlusion of the involved sinus, (2) disconnection of the proximal portion of the draining vein in those with exclusive cortical venous drainage, or (3) disconnection of the dangerous portion of the cortical vein, without complete occlusion of the shunt turning a fistula with “dangerous” angioarchitecture into one with more benign features.
In general, treatment is indicated for symptomatic and clinically aggressive DAVFs. Borden type I fistulas have a very low risk of hemorrhage or nonhemorrhagic neurologic deficits, and observation with surveillance and palliation of symptoms with particulate embolization are viable choices. Alternatively, many Borden type II–III DAVFs show aggressive clinical behaviors, and treatment is often required. In a classic meta-analysis of 377 intracranial DAVFs, Awad et al noted that cortical venous drainage is often associated with progressive neurological deficits, increased intracranial pressure, and higher risk of hemorrhage.5
In a seminal publication now of historical value, Sundt and Piepgras described resection of the involved dural sinus before the development of endovascular treatment and modern microsurgical approaches. These authors described the results of 27 patients surgically treated with ligation and complete excision of the transverse sinus at the point of connection with the sigmoid sinus. The results were excellent in 22 patients and good in 1 patient. However, two patients died and two suffered poor outcome.6 With refinement of endovascular techniques, the vast majority of DAVFs with involvement of a major dural sinus and retrograde cortical venous drainage are treated with endovascular techniques and surgery is rarely necessary. When surgery is necessary for an isolated arterialized sinus, skeletonization of the sinus with disconnection of arterialized veins and packing of the sinus with hemostatic agent without excision is the preferred surgical technique (► Fig. 16.1 and ► Fig. 16.2).
Fig. 16.1 A 63-year-old man presented with progressive visual symptoms. (a) MRI demonstrates evidence of T2 signal changes in the left parietal occipital area (white arrow). The remaining of the MRI suggests evidence of abnormal vascularity of the region, so catheter angiography was performed. Left external ICA injection anteroposterior (AP) (b) and lateral (c) views show a fistula of the isolated transverse sigmoid sinus junction (arrows) with retrograde cortical venous drainage through multiple veins (arrowheads).
Fig. 16.2 Same patient as ► Fig. 16.1. Through a left parietal occipital craniotomy, the isolated left transverse sigmoid junction was exposed and the isolated sinus was packed with hemostatic agent and obliterated. Postoperative angiography, left external carotid artery injection, AP view (a) and lateral view (b) show complete occlusion of the fistula. Follow-up axial T2 MRI (c) shows resolution of the T2 changes at follow-up.
In those patients with DAVFs without sinus involvement and exclusive leptomeningeal drainage, simple disconnection of the proximal portion of the draining vein is a simple and effective technique (► Fig. 16.3). Collice et al described two types of DAVF: “sinus fistula,” which occurs when the lumen of the sinus participates in the shunt, and “nonsinus fistula,” which occurs when the shunt is confined into the wall of the sinus without communication to the inside of the parent sinus.7 The authors introduced the concept of “disconnecting” the venous drainage in the nonsinus fistula DAVFs. Twenty cases of DAVFs with “pure leptomeningeal drainage” were treated (9 with direct surgery, 11 with preoperative arterial embolization). Complete radioanatomical cure was obtained in 95% of cases with a low morbidity and mortality rate.
Fig. 16.3 In patients with exclusive leptomeningeal drainage, simple ligation of the proximal portion of the arterialized vein as it emerges from the dura results in complete obliteration and resolution of the fistula. This 54-year-old man presented with several-week history of intractable nausea, headache, and cognitive decline. CT of the head demonstrated edema of the right cerebellar hemisphere with compression of the fourth ventricle (a). CT with contrast (not shown) suggested abnormally dilated vessels in the posterior fossa, and this prompted a catheter angiography. (b) Right vertebral artery injection, lateral view shows a dilated posterior meningeal artery (arrows) supplying a dural fistula localized under the posterior third of the tentorium. (c) In the late arterial phase, there is an early filling vein (white arrows) emanating from the undersurface of the tentorium (asterisk) with retrograde cortical venous drainage (arrowheads). Because of inability to achieve distal microcatheter navigation of the feeding artery, the patient was treated with surgical disconnection by placing a surgical clip at the point of emergence of the arterialized vein from the tentorium. Follow-up catheter angiography (d) confirms complete angiographic obliteration of the fistula.
The similar treatment was reported by Thompson et al in four patients with DAVFs and leptomeningeal venous drainage. The authors treated two petrotentorial, one middle fossa, and one posterior fossa DAVF by interrupting the draining vein in the passage between dura and subarachnoid space. Improvement of neurological condition and complete occlusion were obtained in all four patients.8 Although simple and very effective, surgical disconnection of the draining vein has become a less common procedure given that many of these DAVFs can be effectively treated with liquid embolic agents.
In DAVFs with involvement of a main sinus and retrograde leptomeningeal drainage, the treatment strategy can be to simply exclude the retrograde leptomeningeal drainage without complete occlusion of the DAVF if complete occlusion of the fistula cannot be safely obtained. This strategy converts the DAVF into a more benign type of vascular lesion. Davies et al of the University of Toronto Brain Vascular Malformation Study Group assessed a large series of 102 patients with aggressive cranial DAVFs. In cases of combined dural sinus drainage and cortical venous reflux, the authors performed a selective disconnection of the drainage vein, which leaves the fistula in the wall of the dural sinus untouched. Selective disconnection was performed in 23 DAVFs and the neurological and angiographic outcome was comparable to those with obliterated DAVFs.9
16.4 Surgical Treatment by Location
16.4.1 Anterior Cranial Fossa (Ethmoidal Fistulas)
Anterior cranial fossa DAVFs have been reported with much lower frequency than with other locations and represent fewer than 10% of all DAVFs.10 Ethmoidal DAVFs can cause headache, visual symptoms, seizures, or epistaxis. They can also occasionally hemorrhage and cause more aggressive symptoms.11,12
The principal blood supply to these DAVFs is derived from the ophthalmic artery (► Fig. 16.4 and ► Fig. 16.5) but the external carotid artery can also give arterial feeders. The pial veins of the anterior frontal lobe usually drain the ethmoidal DAVF into the superior sagittal sinus. More rarely, they can drain posteriorly toward the cavernous or sphenoparietal sinuses.10,13 The higher hemorrhage risk could be related to the increased pressures in fragile pial veins that drain into the superior sagittal sinus. Varices or pseudoaneurysms can also increase the risk of rupture.
Fig. 16.4 This 45-year-old woman underwent MRI for investigation of new onset of headache. Coronal T2 MRI (a,b) suggests presence of abnormally dilated vessel in anterior frontal region (white arrows).
Related posts:
Development of the Cerebrovasculature and Pathogenesis of Arteriovenous Malformations and Arteriovenous Fistulas
Stereotactic Radiosurgery for Brain Arteriovenous Malformations
Classification of Brain Arteriovenous Malformations and Fistulas
Natural History of Arteriovenous Fistulas, Clinical Presentation, and Indications for Treatment
Surgery of Basal Ganglia, Thalamic, and Brainstem Arteriovenous Malformations
Surgical Treatment of Cerebellar Arteriovenous Malformations
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
