Dural arteriovenous fistulas (dAVFs) are rare vascular malformations characterized by abnormal arteriovenous connections within the dura mater, primarily affecting intracranial venous sinuses, notably those in the posterior fossa [1,2]. Clinical presentations vary widely, ranging from mild symptoms such as headaches and pulsatile tinnitus to severe neurological deficits, seizures, and intracranial hemorrhage [3–5]. Diagnosis and precise anatomical characterization are established via digital subtraction angiography (DSA), the diagnostic gold standard, as dAVFs may remain occult in cross-sectional imaging modalities [2,6]. The classification by Cognard et al. [7] categorizes dAVFs according to their venous drainage patterns and the presence or absence of cortical venous reflux, correlating with hemorrhage risk and clinical severity. Higher-risk types (Cognard Types IIb to V), exhibiting cortical venous reflux, mandate intervention due to increased risk of severe complications, whereas lower-risk types are typically managed conservatively [2,8].

We present a challenging case of a Cognard Type IIb dAVF at the right transverse sinus, complicated by ipsilateral sigmoid sinus thrombosis and contralateral sinus hypoplasia. The lesion was successfully treated via a transvenous recanalization and sinus stenting approach, effectively downgrading the fistula to a stable Type I.

A patient in their 60s was admitted to the emergency department due to sudden loss of consciousness. Upon admission, the patient was somnolent, exhibiting enuresis, encopresis, and retrograde amnesia. Clinically, left-sided hemiparesis was evident. The patient had been suffering from recurrent complex focal epileptic seizures for 1 year. Cross-sectional imaging (CT, CTA, and cMRI) and subsequent DSA revealed a Cognard Type IIb dAVF at the lateral aspect of the right transverse sinus (Fig. 1A–C). Additionally, thrombosis of the right sigmoid sinus with compensated venous congestion was observed (Fig. 1D, E). There was no intracranial edema. The left transverse sinus appeared hypoplastic. There was significant venous reflux with retrograde filling of the superior sagittal sinus and deep venous system, as well as marked cortical reflux peritentorial. Arterial fistula supply was provided by transosseous branches of the occipital artery, middle and posterior meningeal arteries, and the meningohypophyseal trunk. Feeders also arose from the C1 branch of the left vertebral artery (through the posterior meningeal artery).

Given the high risk of bleeding, endovascular treatment was indicated. The usual treatment approach, considering the hypoplasia of the contralateral venous outflow, would have been transarterial embolization with preservation of the transverse sinus. However, as venous outflow caudally was impossible due to thrombosis of the sigmoid sinus, the decision was made to initially perform recanalization therapy to achieve downgrading of the fistula and access to the transverse sinus.

The recanalization of the sigmoid sinus was performed in 2 stages due to initial technical difficulties. On the first day, retrograde transfemoral venous access was established, placing an 8F Cerebase guiding catheter (CERENOVUS) at the jugular bulb. Retrograde catheterization of the occluded sigmoid sinus was achieved with a microwire. A large-bore aspiration catheter (6F Sofia Plus; MicroVention) was advanced into the right transverse sinus using a buddy-wire technique (2 0.035” wires; Terumo). Partial recanalization of the occlusion was then performed via a stent-retriever maneuver (NeVa 4.5x29 mm; Vesalio) combined with continuous aspiration (AXS Aspiration Tubing; Stryker). A sinus stenosis remained, but the fistula no longer showed reflux (Fig. 1F, G). Since antegrade flow is sufficient for downgrading the fistula, we decided to maintain this flow permanently by stenting the sinus. However, a Wallstent (PRECISE 9x30 mm; CORDIS) could not be implanted due to insufficient catheter support, attributed to a 360° loop in the distal internal jugular vein.

On the following day, direct ultrasound-guided puncture of the right internal jugular vein allowed insertion of a 6F sheath for enhanced stability and support. Using a stiff peripheral 0.035-inch wire (Rosen fixed core steel wire; Cook Medical), we introduced a self-expandable Superflex Stent (Sinus SuperFlex 635, 10x80 mm; OptiMed) across the remaining stenosis from the transverse sinus to the jugular vein (Fig. 1H, I). The final series already showed antegrade drainage through the sinuses with minimal residual fistula flow (Fig. 1J, K). The patient received intravenous full heparinization for 5 days (target partial thromboplastin time 60–90 seconds) and secondary prophylaxis with aspirin 100 mg/day, initially for 3 months.

Follow-up DSA after 3 months showed proper positioning of the implanted stent and a stable Cognard Type I situation. Clinically, there was almost complete improvement of neurological symptoms with residual mild left facial paresis. Regarding epilepsy, the patient remained seizure-free. In an interdisciplinary consensus, aspirin therapy was continued.

The patient was informed about the risk of recurrence and definite treatment of the residual dAVF via trans-arterial embolization or gamma-knife surgery. At the patient’s request following detailed counseling regarding therapeutic options and associated risks a conservative management strategy was chosen. The agreed-upon plan included regular magnetic resonance imaging (MRI) follow-up imaging with subsequent outpatient consultation. Follow-up MRI 1 year later showed a stable situation (Fig. 1L). The patient was instructed to seek immediate medical reassessment should symptoms such as recurrent pulsatile tinnitus occur in the interim.

Our case describes a complex anatomical situation in a patient with dAVF and associated sinus thrombosis. Transarterial embolization was not feasible for treating the acute symptoms. Transvenous embolization could not be performed due to contralateral hypoplasia. Our case demonstrates that recanalization of an occluded venous sinus via a jugular approach is possible. We achieved restoration of integral venous drainage and significant downgrading of the fistula to a stable Cognard Type I situation.

What is novel about our case is the use of a 0.035-inch guidewire and stent system for the treatment of a complex dAVF with associated sinus thrombosis. This approach allowed for successful recanalization and stenting of the occluded sinus, resulting in downgrading of the fistula without the need for additional embolization. Our case adds to the limited literature on alternative endovascular techniques for managing complex dAVFs.

Stiff guidewires increase the risk of vessel injury in neurointerventional procedures, and the complex anatomy of the transverse-sigmoid junction complicates the use of large catheters [9]. Due to residual sigmoid stenosis and anatomical constraints preventing the advancement of a Wallstent over a conventional 0.014-inch wire, we selected a stiff 0.035-inch Rosen peripheral guidewire, despite it not being specifically designed for neurointerventions. Its enhanced stiffness and radial force proved suitable for overcoming the challenging stenosis in the right sigmoid sinus, a technique previously described for severe sinus thrombosis but not yet reported for successful dAVF treatment [10]. A stiff 0.035-inch guidewire can effectively traverse highly stenotic or occluded venous sinuses that are otherwise impassable by microwires due to inadequate support [9,11]. Similar approaches involving large-caliber guidewires have successfully facilitated sinus recanalization in combination with adjunctive stenting. In the series by Lin et al. [12], which combined adjunct sinus stenting with embolization in 18 dAVF patients, a 0.035-inch guidewire or 0.027-inch microcatheter-microwire kit was used to pass the occluded sinus. Takemoto et al. [13] applied a hybrid strategy: they first penetrated an occluded sigmoid sinus with a 0.035-inch Terumo wire, then exchanged to a 0.014-inch microguidewire to perform sequential dilations, and finally deployed an 8×40 mm Precise stent. Although smaller microwires generally offer lower risk of vessel injury and greater compatibility with neurovascular devices, they often lack sufficient radial force in severely thrombosed segments [9].

Venous sinus stenting can be an effective treatment for dAVFs in selected cases, but stent occlusion remains an issue. Lin et al. [12] demonstrated the efficacy of adjunct venous sinus stenting in 18 patients. Stent patency was 69% on follow-up, yet only 38% of the patients could achieve angiographic AVF obliteration. Takada et al. [14] described using self-expanding closed-cell stents combined with high-pressure balloon angioplasty to compress the dural fistula within the sinus wall, thereby reducing or obliterating shunt flow. Similar to our case, Choi et al. [15] reported deploying a covered stent in the dominant transverse-sigmoid sinus of a patient with contralateral sinus hypoplasia, successfully occluding the dAVF while maintaining crucial venous outflow. Liebig et al. [16] treated 4 patients with transverse-sigmoid sinus dAVFs using stent deployment; complete angiographic occlusion of the fistula was achieved in 3 of 4 cases.

We opted for aspirin monotherapy as we deemed it adequate for this case. Post-interventional antiplatelet management following intracranial venous sinus stenting in dAVFs may involve dual antiplatelet therapy with aspirin and clopidogrel for approximately 3–6 months, transitioning subsequently to aspirin monotherapy to balance thrombosis prevention with bleeding risks [17,18]. Alternative regimens including anticoagulation combined with a single antiplatelet agent have also demonstrated safety and efficacy [19]. However, in our opinion there is only weak evidence supporting dual antiplatelet agent therapy in the setting of venous sinus stenting [18,20].

Our case further supports the potential of venous sinus stenting as a treatment option for complex dAVFs, particularly in cases where traditional embolization techniques are not feasible [21]. The use of a stiffer guidewire and larger stent system, as described in our case, may offer advantages in overcoming challenging anatomical situations and achieving adequate radial force for sinus recanalization.

The present case adds to this growing body of evidence by demonstrating that venous sinus stenting alone can effectively treat a complex dAVF. Stenting of dural fistulas without additional embolization may be sufficient for fistula reduction in selected cases. This approach expands the treatment options for complex dAVFs, particularly in situations where conventional techniques are limited by anatomical constraints or associated pathologies such as sinus thrombosis. Close follow-up of treated patients is necessary.