Transcranial Transvenous Embolization with Onyx through a Steerable Catheter for a Dural Arteriovenous Fistula of the Isolated Superior Sagittal Sinus: A Technical Case Report

Naoya KIDANI; Yasutaka AKINO; Ryohei TSUCHIE; Yusuke TOMITA; Kenichiro MURAOKA; Nobuyuki HIROTSUNE

doi:10.2176/jns-nmc.2025-0365

Abstract

We report a rare case of an isolated superior sagittal sinus dural arteriovenous fistula successfully treated by transcranial direct puncture transvenous Onyx embolization using a steerable microcatheter. With reduced arterial inflow and sinus balloon protection, Onyx injection through the steerable catheter achieved complete occlusion of the shunted pouch without complications. The patient showed marked improvement in cortical venous dilatation and cerebral edema. This case highlights the feasibility and safety of combining transarterial flow reduction, sinus balloon protection, and steerable microcatheter navigation for the curative embolization of isolated sinus dural arteriovenous fistulas.

Introduction

Dural arteriovenous fistulas (dAVFs) with an isolated sinus lack normal antegrade drainage and frequently cause cortical venous reflux, leading to intracranial hemorrhage, venous infarction, or intracranial hypertension.¹^,²⁾ Among these, superior sagittal sinus (SSS) dAVFs are often managed effectively with transvenous embolization (TVE).³⁾ When the sinus is occluded, however, the transfemoral approach may be unfeasible. Direct SSS puncture through a small craniotomy has been reported as an alternative, mainly enabling coil embolization of the venous pouch.⁴^,⁵⁾ Nevertheless, sinus packing with coils may be insufficient, leaving residual shunt flow.

Onyx (Medtronic, Irvine, CA, USA) can achieve curative pouch embolization, but reports of its use through direct sinus puncture and via a steerable microcatheter (SM) are extremely limited. Here, we report an isolated SSS dAVF cured by Onyx embolization using both transarterial and direct sinus puncture approaches with balloon protection, in which Onyx was injected through an SM.

Case Presentation

A 59-year-old man was admitted to our hospital following a seizure. He had no relevant past medical or family history. Cognitive dysfunction was observed, with a revised Hasegawa's Dementia Scale (HDS-R) score of 20. Magnetic resonance imaging (MRI) demonstrated deep white matter edema and diffuse cortical venous engorgement involving both cerebral hemispheres (Figure 1a and b). Six-vessel cerebral angiography revealed an arteriovenous shunt draining into the SSS (Figure 1c-e). The lesion was supplied by multiple branches of the external carotid arteries, predominantly from the bilateral middle meningeal arteries (MMAs). All feeders converged into the ventral part of the parasinus region of the SSS. The shunted pouch was located adjacent to the left upper aspect of the SSS and opened dorsally into the left lateral wall of the SSS. Given that the SSS was occluded just dorsal to the lesion, all shunted blood flowed retrogradely within the SSS and exhibited marked cortical venous reflux (Figure 1f). Based on these findings, the patient was diagnosed with an isolated SSS dAVF (Borden type III, functionally equivalent to Cognard type III). We planned TVE with Onyx under conditions of reduced arterial inflow from the feeders.

Figure 1

Preoperative fluid-attenuated inversion recovery (FLAIR) image (a) showed edematous changes in the bilateral deep white matter. Susceptibility-weighted imaging (SWI) (b) demonstrated dilation of the bilateral cortical veins. Anteroposterior (c) and lateral views (d) of the left external carotid angiogram revealed an SSS dAVF supplied by multiple branches of the external carotid artery. The anteroposterior view of the right external carotid angiogram (e) also showed an SSS dAVF fed by multiple branches of the MMA and the superficial temporal artery.

f: A simplified schematic illustration of the angioarchitecture from a left anterosuperior oblique perspective. The asterisk indicates the opening of the shunted pouch into the SSS. Note that the SSS is occluded (arrowhead) just dorsal to the shunt opening.

dAVF: dural arteriovenous fistula; MMA: middle meningeal artery; PMA: posterior meningeal artery; SSS: superior sagittal sinus

The procedure was carried out in a hybrid operating room to enable the combined use of endovascular and open surgical techniques. Under general anesthesia, an oval-shaped frontal midline craniotomy was performed, and the SSS was punctured from the ventral to dorsal side for insertion of a guiding sheath (Figure 2a). A SM, Leonis Mova Selective (SB-Kawasumi Laboratories, Kanagawa, Japan), was inserted into the guiding sheath of the SSS. By manipulating the tip angle of the SM, the catheter tip could be stably positioned opposite the orifice of the shunted pouch. To interrupt outflow from the shunted pouch into the SSS, balloon catheters (SHOURYU2 HR; Kaneka Medix, Osaka, Japan) were positioned within the SSS and fully inflated (Figure 2b). One balloon (7 × 11 mm) was placed at the orifice of the shunt pouch, and the other (7 × 7 mm) was positioned anterior to the shunt to prevent further extension into the SSS. However, external carotid angiography still demonstrated cortical venous reflux. Given that a substantial amount of liquid embolic material was expected to flow into the cortical veins under this condition, transarterial embolization (TAE) was performed in advance to reduce shunt flow prior to TVE.

Figure 2

a: Intraoperative photograph of the frontal region. A 6-French guiding sheath (white arrows) was inserted into the isolated SSS along the guidewire that had been previously advanced percutaneously. b: Lateral fluoroscopic image showing insertion of the guiding sheath (white arrow) into the SSS through a small frontal craniotomy (asterisk). The tip of the steerable microcatheter (white arrowheads) was maintained in a curved orientation toward the shunt point. c: Right external carotid angiogram obtained immediately after TAE. The dorsal component of the shunt pouch remained, and both the SSS and cortical venous reflux were still visualized (black arrows). d: Schematic illustration of the intraoperative catheterization before TVE. A steerable microcatheter (light green) was inserted into the shunt pouch. The Onyx cast injected during TAE is shown in black (star). e: Onyx cast after TAE penetrating multiple feeders and a portion of the shunt pouch (black arrowhead). f: Onyx cast obtained after TVE penetrating the dorsal component of the shunt pouch (double arrowheads) and partially into the SSS.

SSS: superior sagittal sinus; TAE: transarterial embolization; TVE: transvenous embolization

A microcatheter for TAE was inserted into the right MMA. Subsequently, Onyx 18 (2.7 mL) was injected via the MMA using a plug-and-push technique, achieving embolization of the ventral portion of the shunted pouch. As a result, shunt flow was reduced; however, residual inflow from the dorsal part of the pouch into the SSS persisted (Figure 2c-e). Under balloon protection within the SSS, transvenous continuous injection of Onyx 18 (1.9 mL) was performed through the SM, resulting in complete occlusion of the shunted pouch (Figure 2f). Hemostasis at the SSS puncture site was achieved by compression after sealing with fibrin glue.

Although the patient experienced an acute symptomatic seizure postoperatively, it was controlled with antiseizure medication. The HDS-R score improved to 29, and the patient was discharged with a modified Rankin Scale score of 0. MRI at 1 week postprocedure confirmed improvement in both cerebral edema and cortical venous dilatation (Figure 3a and b). Follow-up cerebral angiography 3 months after surgery confirmed the complete disappearance of the shunt (Figure 3c and d).

Figure 3

Postoperative fluid-attenuated inversion recovery (FLAIR) image (a) shows complete resolution of bilateral edematous changes. Susceptibility-weighted imaging (SWI) (b) demonstrates markedly reduced dilation of the cortical veins compared with the preoperative image. Right (c) and left (d) external carotid angiograms obtained three months after surgery demonstrated the complete disappearance of the shunt.

Discussion

dAVFs with cortical venous reflux carry a substantial risk of intracranial hemorrhage and focal neurological deficits and therefore warrant active intervention.¹^,⁶⁾ In cases of isolated sinus dAVFs, curative outcomes can be achieved by superselective embolization of the shunted pouch.²^,⁷⁾ However, when a route to the affected sinus shows long-segment occlusion, the traditional transfemoral venous approach is not feasible for reaching the lesion.⁸^,⁹⁾ In this case, the SSS was occluded over more than 11 cm from the shunt pouch to the torcular. Although cervical venous puncture with retrograde navigation or guidewire recanalization has been reported, traversing such a long thrombosed segment was considered unsafe and unreliable, with risks of perforation and inadequate catheter support. Therefore, transcranial direct access was selected as the most secure and controllable route to the shunt pouch.

We performed TVE with Onyx via direct puncture of the SSS. In this case, multiple feeders from the external carotid artery were identified, some of which drained directly into cortical veins without passing through the shunt pouch. For these reasons, we considered that TAE alone would be insufficient to achieve cure. Several treatment options, including transvenous coil embolization alone and surgical sinus isolation, were considered. However, particularly when the shunt orifice is wide, sinus packing with coils alone may result in incomplete occlusion of the shunt point,¹⁰^,¹¹⁾ whereas surgical sinus isolation was considered more invasive. In contrast, appropriate use of liquid embolic material can achieve complete shunt obliteration without extensive coil deployment.¹²⁾ Liquid embolic agents, however, carry the risk of unintended migration into draining veins.¹³⁾ In the present case, residual cortical venous reflux persisted despite sinus balloon inflation, and TAE was therefore performed in advance to reduce shunt flow and enable safer transvenous Onyx injection. Efficient and safe embolization of the shunted pouch was accomplished by reducing arterial inflow and injecting Onyx under sinus protection with a balloon placed in the SSS.

Stable positioning of the microcatheter tip oriented toward the shunt point was also considered to contribute to the achievement of complete embolization. A SM is a device that allows manual adjustment of the catheter tip angle using a hand-operated dial. Its orientation can be locked with a dial stopper to maintain the tip directed toward the target lesion or another intended direction. In this case, the shunt orifice was oriented in a direction nearly opposite to the catheter insertion axis, and the distance from the orifice to the shunt point was short, requiring the catheter tip to be sharply deflected and maintained in that position throughout prolonged Onyx injection. Although conventional microcatheters can be steam-shaped and may allow distal access in many cases, their flexible tips may deviate from the shunt pouch during injection in this anatomical configuration. Therefore, an SM was used to allow precise adjustment and locking of the tip orientation toward the shunt point, enabling stable and controlled embolic delivery. In the treatment of dAVFs, several reports have demonstrated that this device is useful and safe for selective catheterization of target lesions during selective TVE.¹⁴^,¹⁵⁾ However, to the best of our knowledge, there have been no previous reports of TVE in which a liquid embolic agent was injected through an SM inserted into the shunt pouch. Further studies are required to elucidate the usefulness and safety of the Leonis Mova microcatheter series for injection of liquid embolic agents.

Nevertheless, even with an SM, there remained a risk of catheter tip deviation and unintended Onyx reflux into the SSS. Hara et al.¹⁴⁾ noted that maintaining adequate support with an SM can be challenging during embolization procedures within large-caliber sinuses such as the SSS. For this reason, a balloon catheter was inflated within the sinus to enhance microcatheter stability and to occlude the shunt outflow, thereby preventing uncontrolled Onyx migration.

In the SSS and other dural sinuses, directional manipulation of a small-diameter SM may raise concerns about the risk of vessel wall perforation. Tomita et al.¹⁶⁾ demonstrated in an in vitro study that the SM could be safely navigated and manipulated to access a 7-mm sidewall-type aneurysm. In the present case, selective navigation into the 7-mm shunt pouch was also safely and easily achieved under micro-guidewire guidance. During catheter removal, the locking mechanism was released to allow free movement of the catheter tip, enabling safe withdrawal of the SM. Previous reports in neurointerventions, together with the present case, have demonstrated that SMs provide improved navigability, precise tip control, and acceptable safety profiles in complex vascular anatomy, supporting their utility in selected cases.¹⁴^,¹⁵^,¹⁷⁾

Conclusions

Transcranial direct puncture transvenous Onyx embolization using a SM enabled safe and complete occlusion of an isolated SSS dural arteriovenous fistula by allowing stable and controlled delivery of the embolic material under flow reduction and sinus balloon protection. This combined technique may represent a practical and effective therapeutic option when conventional transvenous access is precluded by sinus isolation or occlusion.

Conflicts of Interest Disclosure

All authors have no conflict of interest.

Ethical Considerations

The off-label use of Onyx through a steerable microcatheter was approved by the institutional review board of our hospital (approval No.2025-141), and written informed consent was obtained from the patient.

Patient Consent

The patient has consented to the submission of the case report to the journal.

References

責任著者(Corresponding author)

J-STAGEへの登録はこちら（無料）