Simultaneous findings of shunt obliteration and arterial flow restoration during balloon-assisted technique in the management of idiopathic vertebral arteriovenous fistula

Abstract

The etiology of vertebral arteriovenous fistulas (VAVFs) is diverse, and when selecting an optimal therapeutic strategy, it is important to evaluate the feasibility of preserving the vertebral artery (VA). A 75-year-old woman presented with pulsatile tinnitus, and imaging revealed a high-flow vertebral arteriovenous fistula (VAVF) with a single shunt point at the V2 segment; the distal ipsilateral VA was not visualized, suggesting occlusion or a steal phenomenon. Stepwise balloon adjustment near the shunt site eliminated shunt flow and restored distal VA flow, confirming steal and enabling a successful vessel-preserving treatment. This case demonstrates that controlled modulation of flow near the shunt site using a balloon catheter can effectively predict the potential for restoration of VA flow, and suggests the clinical utility of this technique in planning a strategy that achieves shunt obliteration while preserving the vertebral artery.

Introduction

Vertebral arteriovenous fistulas (VAVFs) are usually associated with trauma, iatrogenic injury, or connective tissue disorders. Truly idiopathic cases without any identifiable etiology are relatively uncommon. VAVFs are typically treated using endovascular techniques, and a critical factor influencing the success of treatment is the management of the vertebral artery (VA) during intervention. This report describes a case of idiopathic VAVF in which distal flow in the affected VA was not visualized, likely due to a high-flow shunt and an associated steal phenomenon. Targeted embolization of a single draining vein resulted in rapid and complete obliteration of the shunt with restoration of distal VA flow. In this case, a balloon occlusion test (BOT) followed by a simple technique of stepwise deflation of the balloon at the shunt site played an important role in assessing the feasibility of VA preservation, and contributed to the success of the subsequent vessel-preserving treatment.

Case

A 75-year-old woman presented to our hospital with pulsatile tinnitus in the absence of any apparent precipitating factor. The tinnitus was constantly audible, particularly distressing in quiet environments, and was clearly auscultated as a bruit near the affected ear. Three-dimensional CT angiography and digital subtraction angiography of the head and neck revealed a high-flow VAVF with a single shunt point on the right vertebral artery at the V2 segment (Fig. 1, Fig. 2). The distal portion of the ipsilateral VA beyond the shunt point was not visualized, suggesting that either occlusion or a steal phenomenon was responsible for the nonopacification. Because it was possible that the VA was not occluded but rather not visualized due to a steal phenomenon, we planned to evaluate the potential for VA preservation using a balloon occlusion test (BOT) in conjunction with balloon-assisted flow modulation at the shunt site.

Fig. 1.

Initial digital subtraction angiography (DSA) images of the right vertebral artery. (A) Anteroposterior view and (B) Lateral view. A high-flow vertebral arteriovenous fistula with a single shunt point is seen at the V2 segment. Due to the strong shunt flow, the distal portion of the right vertebral artery is not visualized beyond the fistula. The white arrow heads indicate the vertebral artery, and the white arrow points to the shunt point. The draining vein corresponded to the vertebral venous plexus, draining anterogradely into the internal jugular vein. There was no evidence of retrograde reflux into the dural sinuses or intracranial veins.

Fig. 2.

Axial (A) and coronal (B) views of contrast-enhanced CT angiography (3DCTA). The white arrow heads indicate the vertebral artery, and the white arrow indicates the shunt point. The coronal view demonstrates that the shunt point at the V2 segment is located at the upper margin of the C3 vertebral body.

The procedure was performed under systemic heparinization. Under local anesthesia, A 6Fr guiding catheter (ROADMASTER, 90 cm, STR; Goodman Co., Ltd., Aichi, Japan) was introduced via the left femoral artery and advanced to the origin of the right VA. Through this, A balloon catheter (SHOURYU, 7×7 mm; Kaneka Corporation, Osaka, Japan) was navigated distally into the right VA. The balloon was fully inflated near the shunt site, resulting in complete interruption of contrast flow into the proximal VA and disappearance of shunt flow (Fig. 3A and D). The balloon size was selected based on multiplanar reconstruction (MPR) images from 3D-DSA, which showed the fistula orifice to be 2.5 mm and the VA diameter to be 4.5 mm. At this point, the patient’s pulsatile tinnitus immediately resolved. The balloon was then very gradually deflated, with repeated contrast injections performed frequently at each step. At a certain point, the shunt remained occluded, while distal VA flow, which had not been visualized previously, began to appear (Fig. 3, Fig. 3). No neurological abnormalities were observed during a 5-minute observation period in this state. Continuing the same technique of very slow deflation with frequent contrast injections, a point was reached at which shunt flow recurred and distal VA perfusion again disappeared (Fig. 3, Fig. 3). In Fig. 3C, the shunt region was partially obscured by dental metal artifacts, but recurrence of shunt flow was clearly confirmed in the corresponding lateral image (Fig. 3F). Re-inflation of the balloon completely occluded both the shunt and distal VA flow, and an additional 10-minute BOT was performed, during which no new neurological symptoms appeared. These findings confirmed that the lack of visible distal VA flow was due to a steal phenomenon rather than occlusion of the VA.

Fig. 3.

DSA images showing hemodynamic changes during the balloon-assisted technique.(A–C) Anteroposterior views. (D–F) Lateral views. (A, D) Complete balloon inflation at the shunt site (arrow) resulted in arrest of shunt flow. Although faint contrast pooling is seen proximally, antegrade flow in the vertebral artery (VA) is not visualized. (B, E) Slight balloon deflation allowed restoration of distal VA flow without recurrence of shunt flow (arrow) and (C, F) Further deflation led to recurrence of shunt flow (arrow), with distal VA flow again disappearing owing to a steal phenomenon. Note: In image (C), the shunt region is partially obscured by dental metal artifacts, but recurrence of shunt flow is clearly confirmed in the lateral view (F).

Three days after the BOT, transarterial embolization targeting the shunt point was performed. Under general anesthesia and systemic heparinization, .a 7Fr guiding catheter (FUBUKI STRAIGHT, 90 cm; Asahi Intecc Co., Ltd., Aichi, Japan) was placed in the proximal right vertebral artery via the right femoral artery. Through this, A microcatheter (Excelsior SL-10, 45° tip; Stryker Neurovascular, Fremont, CA, USA) was navigated beyond the shunt point at the V2 segment of the VA and advanced sufficiently distal into a single draining vein connected to the fistula. After confirming the draining vein by microangiography, coil embolization was performed. A total of ten detachable coils (Target™ coils, Stryker Neurovascular, Fremont, CA, USA) were deployed, starting from the distal portion of the draining vein and packed proximally toward its origin, resulting in complete obliteration of the shunt flow (Fig. 4). Simultaneously, restoration of distal VA flow was confirmed, and the patient’s pulsatile tinnitus resolved immediately after treatment.

Fig. 4.

Findings at the time of transarterial coil embolization (frontal views). (A) The white arrow indicates the location of the single shunt point. A microcatheter was navigated through this site for embolization. (B) Vertebral angiogram obtained following coil embolization of a single draining vein (white arrow), showing complete obliteration of the draining vein and shunt flow and (C) Native image confirming the location of the deployed coils (white arrow).

Postoperatively, strict blood pressure control and neurological monitoring were implemented to mitigate the risk of reperfusion injury. No new neurological deficits or recurrence of tinnitus were observed. The patient was discharged home 1 week after the procedure. Follow-up magnetic resonance angiography performed 3 months after discharge confirmed no recurrence of the VAVF or tinnitus.

Discussion

We encountered a case of truly idiopathic VAVF in which high-flow shunting caused a steal phenomenon, resulting in nonvisualization of distal VA flow. Selective embolization of a single draining vein directly connected to the shunt point led to immediate and complete obliteration of the shunt, with restoration of distal VA flow. Rather than simply inflating and deflating the balloon at the shunt site, we performed stepwise and fine modulation of balloon deflation, confirming each change with repeated contrast injections. This modified approach allowed us to assess the potential for restoration of VA flow prior to treatment and was notably helpful in planning the therapeutic strategy.

The goal of VAVF treatment is complete obliteration of the arteriovenous shunt. Endovascular therapy is the mainstay of treatment, and surgical approaches are rarely used [1]. The treatment strategy is determined based on anatomical considerations, including the location of the fistula, whether there is 1 shunt or multiple shunts, flow rate, type of venous drainage (epidural, intradural, or perimedullary), and the feasibility of preserving the parent VA [2]. BOT is often used to assess the safety of sacrificing the affected VA, based on compensatory flow from the contralateral VA or posterior communicating artery [3].

Patients with idiopathic VAVF, unlike traumatic or iatrogenic cases, are more likely to be younger, female, and to have a genetic disorder, such as neurofibromatosis type 1, hereditary hemorrhagic telangiectasia, or RASA1 mutation [1,4]. Anatomically, idiopathic cases frequently involve high-flow, single-hole shunts at the upper cervical level, as observed in this case.

Tinnitus is reportedly the most common symptom of VAVF, followed by neurological deficits associated with myelopathy [3]. In high-flow shunts, cerebellar infarction may also occur [8], and delayed occlusion of the VA after treatment has been reported to result in sequelae related to anterior spinal artery syndrome [9]. In cases with direct carotid-cavernous fistula, reperfusion complications such as cerebral infarction, intracranial hemorrhage, and visual disturbances have been described [6,10]. Similarly, in VAVFs, there is a risk of reperfusion-related complications including spinal cord infarction, brainstem infarction, and, though rare, intracranial hemorrhage [1,9,11]. In cases such as ours, where flow in the VA is completely unvisualized before treatment, particular caution is warranted concerning the risk of reperfusion injury.

A steal phenomenon is a hemodynamic condition in which shunt flow diverts antegrade arterial flow from the distal vasculature, resulting in nonvisualization on angiography.In a direct carotid-cavernous fistula, the steal phenomenon can similarly result in the nonvisualization of distal flow in the internal carotid artery, which may recover after closure of the shunt. However, if prolonged or complicated by vessel wall damage or thrombosis, the occlusion may persist. No definitive pretreatment method exists for predicting flow restoration in such cases [5,6]. Similarly, in VAVFs, inability to visualize the distal VA as a result of the steal phenomenon is not uncommon, but predicting whether flow will return after treatment remains challenging [7].

BOT is typically considered meaningful in cases where distal VA flow is visible on imaging. When flow is completely absent, BOT is often omitted. However, if the distal VA lumen remains patent, selective shunt closure may allow for restoration of physiological flow. Furthermore, since preoperative 3D-DSA did not provide definitive evidence of a single shunt point, we opted to perform BOT in this case. On diagnostic angiography prior to treatment, delayed and retrograde filling of the right VA through the vertebral union was faintly observed up to the mid-V3 segment during contralateral VA injection. However, no shunt flow was demonstrated, and the possibility of VA occlusion could not be excluded. Additionally, there was no antegrade flow through the posterior communicating artery or evidence of collateral supply to the shunt from the external carotid muscular branches, further preventing us from ruling out occlusion. Performing contralateral vertebral angiography during BOT from the proximal right VA might have revealed shunt flow via retrograde circulation and helped clarify whether the distal VA was truly occluded. However, doing so would have required the placement of an additional catheter through a separate access route, which was not performed.

The technique we employed in this case is relatively simple and can be implemented as part of routine diagnostic angiography. It not only allows for the preoperative prediction of the feasibility of arterial reconstruction but may also help assess the potential risk of ischemic complications or reperfusion injury in advance. Particularly in high-flow vertebral arteriovenous fistulas (VAVFs), where true vascular anatomy is often obscured, such dynamic use of a balloon may serve as an effective therapeutic strategy.

While this technique demonstrated potential for vessel preservation, the favorable findings in this case may have been obtained merely by chance, as the balloon happened to be positioned directly over the shunt opening. In cases involving multiple shunt points or widespread venous drainage, controlling blood flow with a balloon may introduce hemodynamic risks due to unpredictable vascular responses. Although its applicability may be limited to carefully selected cases, this technique might still offer significant diagnostic and therapeutic value, as suggested by the present case.

Conclusion

This case demonstrates successful management of a true idiopathic VAVF in which both shunt obliteration and preservation of the VA were achieved through strategic pretreatment flow evaluation. By using a dynamic approach involving careful modulation of balloon inflation and deflation, the feasibility of arterial reconstruction was assessed in real time, minimizing procedural risks. This technique highlights a practical strategy for preserving critical arterial flow in selected cases of high-flow VAVF and may aid future decision-making in similarly complex cases.

Patient consent

Written informed consent was obtained from the patient for publication of this case report and any accompanying images.