Artery of Davidoff and Schechter Supply in Dural Arteriovenous Fistulas

Published Literature

Based on our review of the literature, this is the largest reported series of dural AVFs supplied by the ADS treated by endovascular techniques (the existing literature predominantly being case reports; On-line Table 3).^1⇓-3,18 The ADS supply may not be appreciated on angiography due to competitive flow from multiple arterial feeders (Fig 3A, -B) and thus may not always have been recognized in large series of tentorial AVFs.^9,19 Tentorial fistulas constitute <3% of cranial AVFs but are 6 times more likely than nontentorial AVFs to present with hemorrhage,²⁰ likely a result of the direct cortical venous drainage seen with these AVFs.^3,13,20

Surgical Approach to Falcotentorial AVFs

Most tentorial AVFs carry a high risk of hemorrhage²⁰ and endovascular approaches can be challenging; thus, some cases may require microsurgical disconnection.^13,21 The primary surgical goal for tentorial AVFs is the same as for all AVFs—occlusion of the proximal portion of the draining vein.²¹ In principle, the operative strategy is based on an optimal surgical approach with an ideally adapted patient position allowing gravity to retract the brain, open subarachnoid planes, and shorten dissection times to expose and interrupt the draining vein.^13,21

Lawton et al,¹³ in 2008, created a surgical classification of tentorial AVFs based on their experience with 31 cases, differentiating 6 types based on fistula location, dural base, associated sinuses, and direction of venous drainage. Among those 31 patients, arterial supply from branches of the SCA or PCA (including the ADS) was identified in 8 patients.¹³ Six of these 8 patients had the Galenic subtype, located adjacent to the falcotentorial junction with drainage to the vein of Galen either directly or via cortical veins, requiring a posterior interhemispheric surgical approach after initial transarterial embolization.¹³ Preoperative embolization is often undertaken to minimize blood loss due to the extensive adjacent arterial and deep venous structures in the operative field.^13,22 If a cure can be achieved by endovascular means, this may be preferable to a surgical approach.²¹

In our overall cohort of 173 patients with intracranial AVFs, only 4 patients had falcotentorial Galenic subtype AVFs¹³ (2.3%). All 4 patients demonstrated an ADS supply and were included in this study; this finding is consistent with the known high rates of SCA or PCA supply to this AVF subtype.¹³ All 4 patients underwent endovascular treatment with angiographic cure, and none required surgical intervention.

Endovascular Approaches to Falcotentorial AVFs with ADS Supply

Both transarterial^2,3,18 and transvenous²³ approaches with the use of liquid embolic agents have been described for the successful treatment of falcotentorial AVFs, with a treatment goal of occlusion of the fistulous point and foot of the draining vein to achieve cure. In our series, all patients initially underwent transarterial embolization using liquid embolics (On-line Table 2), with excellent outcomes, thus eliminating the need for potentially more invasive surgical approaches.

In patient 2, the initial embolization procedure also required microcatheter selection and embolization from the ADS itself (Fig 3) once competitive flow from the middle meningeal artery was excluded. In this instance, a highly distal position was achieved with the microcatheter, allowing deposition of small coils to minimize reflux followed by administration of Onyx (Covidien, Irvine, California) directly to the fistulous point using a modified pressure-cooker technique. Understanding the complex arterial anatomy and using imaging-based treatment were the keys to a complete, safe, and successful endovascular treatment approach in this case. In patient 1, the right ADS was cannulated with a microcatheter (Fig 2), but a distal position adjacent to the fistula could not be obtained. Our opinion was that successful injection of a liquid embolic agent from this proximal position would require initial formation of a long plug of embolic agent, thus increasing the risk of reflux into the PCA and basilar artery. This patient was subsequently cured by transvenous embolization.

Impact of ADS Supply on the Endovascular Approach

The key to avoiding reflux across the ADS was initial recognition of its supply to the AVF. Given the potential difficulties of identifying the ADS supply when there is competitive flow (Fig 3) and the high likelihood of pial supply from the SCA or PCA to a Galenic-type tentorial AVFs,¹³ it would be reasonable to assume that most fistulas in this location have potential ADS supply. Therefore, care should be taken to assess the ADS supply with magnified, high-frame-rate DSA and MPRs of 3D rotational angiography (Fig 2B) when treating these fistulas. Even if such a supply is not identified, care should still be taken during embolization to assess any linear reflux anteriorly from the vein of Galen and along the expected course of the free tentorial edge, because this could represent reflux back toward the PCA and basilar artery. We have summarized the strategies we used to avoid dangerous reflux across ADS in the Table.

Study Limitations

This study is limited by the small sample size, retrospective design, and the already-discussed difficulties associated with identifying the ADS supply (potentially underestimating the true rate of supply). The requirement for follow-up imaging may have excluded patients with low-grade fistulas (less of a concern in tentorial AVFs, which are usually high-grade).