The indication for treatment of cranial dural arteriovenous malformations (DAVFs) is dictated by their natural history. Because the risk of hemorrhage and neurologic deficit is directly correlated to the presence of cortical venous reflux (CVR), a general principle is that only these lesions should be treated.

Two accepted classifications, the Borden and the Cognard classification, relate the different hemodynamic patterns of DAVFs and stratify their risk of aggressive progression by considering CVR and the involvement of major venous sinus drainage. These classification systems are important to determine the indication for treatment and to direct the treatment strategy. For simplicity, only the Borden classification is used in this chapter.

Because the risk of hemorrhage is very low in these lesions, they should be treated only in patients with intolerable symptoms, such as tinnitus, ophthalmologic symptoms, or pain. These benign lesions should be observed clinically and radiologically, however, because a small percentage (2% to 3%) eventually develop CVR.

Patients with these lesions should be treated because they have CVR. In patients with neurologic deficits, most often secondary to venous congestion, the sinus cannot be sacrificed, generally precluding a total obliteration of the fistula by surgery or endovascular therapy. The treatment is limited to disconnecting the arterial feeders and skeletonization of the involved sinus. In patients without neurologic deficits, CVR can be disconnected; the fistula can be totally excised with sacrifice of the sinus only if the brain does not use the draining sinus.

Patients with these lesions have the highest risk of bleeding and neurologic deficit. In patients without neurologic deficits, the treatment strategy depends on whether the functional brain uses the veins with cortical reflux from the DAVF. This can be assessed on the venous phase of angiography. In the event the brain uses cortical reflux veins for drainage (especially if there is reflux in the vein of Labbé), only arterial feeder disconnection should be done without disturbing the venous aspect of the lesion. If there is no evidence of brain dependence on cortical reflux veins, a classic CVR disconnection can be done. In patients with neurologic deficits that may be due to venous congestion, only arterial feeders are disconnected.

The classic locations of cranial DAVFs are (1) transverse and sigmoid sinus (40%), (2) cavernous sinus (30%), (3) deep venous and tentorial incisura (10%), (4) superior sagittal sinus and convexity (5%), (5) foramen magnum (5%), (6) anterior cranial fossa (4%), (7) temporal fossa (2%), and (8) superior petrosal sinus (1%). Treatment is determined by the criteria discussed earlier and not the location of the DAVF. Some DVAFs, such as anterior cranial fossa lesions, always have a CVR, however, and are always treated because there is no venous sinus in the proximity of the fistula to route the venous drainage away from cortical veins.

When the indication and the goals of treatment are established, the different management options generally include endovascular embolization through transarterial or transvenous routes and surgery. Although radiosurgery is described for the treatment of DVAFs, it is rarely used. Endovascular treatment should be the first choice whenever it is possible to achieve the goals of the treatment with low risk, and surgery is recommended whenever endovascular therapy fails or is technically not feasible.

Transarterial endovascular treatment involves superselective catheterization of arterial feeding vessels that can be occluded, but the fistula itself is rarely obliterated. Most of the time, treatment through a transarterial route reduces the flow in the fistula by eliminating major feeder arteries, but it is not curative because many smaller feeders cannot be embolized. If residual flow is present in the fistula, further feeders are likely to be recruited leading to recurrence. Some arteries are too microscopic to be occluded, and because of small arterioles in the dura and wall of sinus, these lesions often are hard to cure. Arterial embolization is a very effective adjunct before surgical treatment of DAVF because it can significantly reduce procedural blood loss. Transvenous embolization using a retrograde venous route to access the venous compartment of the fistula is a well-established treatment of DAVFs. It usually involves the occlusion and sacrifice of the DAVF draining sinus. Transvenous embolization is feasible only if venous phase angiography has documented the absence of venous drainage of normal brain by the involved sinus. Most of the time, venous access is impossible in Borden III lesions, which do not drain through a venous sinus but directly in cortical veins.

When endovascular therapy fails or is not possible, three main surgical strategies exist to treat cranial DAVFs.

The first option is direct surgical exposure, catheterization, and packing of the involved sinus with coils or other thrombogenic material (e.g., Gelfoam, silk sutures).

Another option, which is the traditional surgical treatment of DAVFs, is a complete excision of the fistula and the surrounding dura. This approach involves the disconnection of all feeding arteries and arterialized leptomeningeal veins and excision of the draining sinus, when not used by brain, together with pathologic dura. If the brain uses the sinus, the sinus is skeletonized and left patent.

The third option is a selective disconnection of the arterialized leptomeningeal veins with CVR, which is the procedure described here. The rationale of this simpler, less invasive, and less morbid option is based on our understanding of the natural history and physiopathology of DAVFs. Because CVR is the major risk factor for aggressive behavior of DVAFs, it seems plausible that selectively eliminating CVR would convert DVAFs into benign lesions and eliminate the risk of bleeding and neurologic deficit. Based on our positive experience and several reports in the literature, we currently prefer this strategy to complete excision to treat most aggressive DAVFs. As discussed previously, disconnection of CVR is safe only when the brain does not use the reflux veins for its own drainage.

Although there are a few reports on radiosurgical treatment of DAVFs, its current role is unclear. The long interval between treatment and the expected obliteration of DAVFs may be unacceptable for lesions having a CVR and a bleeding or neurologic deterioration risk of about 15% per year.