A dural arteriovenous fistula (DAVF) is a rare type of vascular malformation that occurs when an abnormal connection forms between an artery and a vein in the dura mater [1]. DAVFs comprise approximately 5% of cranial arteriovenous shunts, with the most common location being the transverse and sigmoid sinuses [14]. Vertebral artery dural arteriovenous fistulae (VADAVF) are an exceedingly rare location that most frequently have a traumatic origin [5]. Presentation of VADAVF varies from asymptomatic to those of vertebrobasilar insufficiency [10]. Symptoms may include tinnitus, vertigo, neck pain, visual changes, and ataxia [7,13]. The goal of treatment is occlusion of the shunt while maintaining patency of the parent vessel [6]. We present the first reported case in the literature of use of a flow re-direction endoluminal device (FRED) for successful embolization of a vertebral artery dural arteriovenous fistula.

A 65-year-old male presented with acute onset double vision, slurred speech, and dizziness. He had experienced multiple prior episodes of presyncope within the year prior to presentation. A computed tomography angiogram (CTA) identified a vascular abnormality at the cranio-cervical junction that was difficult to characterize. The brain magnetic resonance imaging (MRI) at the time of presentation identified no acute infarction and confirmed vascular flow voids at the ventral cranio-cervical junction. MRI of the cervical spine demonstrated no cervical cord or brainstem edema.

Diagnostic catheter-based angiography demonstrated a dural shunt originating from the right vertebral artery at the junction of the V3 and V4 segments in the region of the right posterior meningeal artery. A plexiform configuration of poorly defined periarterial vessels contributed to the shunt that demonstrated a prominent arterialized vein extending superiorly through the posterior fossa with drainage into the right transverse sinus (Borden Type 3 DAVF; Figs. 1, 2).

After the catheter-based angiographic study was obtained, the patient underwent initial neurosurgical disconnection of the shunt. An operating microscope was used to dissect down to the jugular region and two fistulous venous structures exiting the dura were cauterized. The dura was closed using harvested fascial graft for duraplasty (Fig. 3A, 3B). Post-surgical follow-up angiogram identified persistence of the shunt vascularity (Fig. 3C). The patient also demonstrated progression of symptoms in the interval with increased dizziness.

The patient agreed to proceed with flow diversion treatment of the shunt. Clopidogrel 75 mg and aspirin 325 mg was commenced five days prior to the procedure. Adequate platelet inhibition was confirmed on the day of the procedure using the VerifyNow-P2Y12 assessment.

The procedure was performed under endotracheal general anesthesia. A Neuron Max guide (Penumbra, Alameda, California, USA) catheter was advanced through to the right vertebral artery. A SOFIA EX (MicroVention, Inc., Aliso Viejo, California, USA) intermediate guide catheter was coaxially placed within a Headway 27 microcatheter (MicroVention, Inc., Aliso Viejo, California, USA) and was advanced through to the right intracranial vertebral artery. A Flow Re-Direction Endoluminal Device (FRED; MicroVention, Aliso Viejo, California, USA) (4 mm × 38 mm) was delivered into the right proximal intracranial vertebral artery, across the most distal and proximal identified arterial feeder vessel. A second FRED (4.5 mm × 45 mm) was tunneled through the first device extending across both arterial feeder vessels.

Post-implantation digital subtraction angiogram (DSA) revealed a significant diminution in opacification of the shunt vascularity without localized vessel injury or thromboembolic phenomenon (Fig. 4). Dual antiplatelet therapy with aspirin and clopidogrel at the same doses was continued for 12 months after the procedure. Follow-up catheter-based angiography obtained at one-year post-procedure showed persistent filling of the shunt (Fig. 4C, D). Dual antiplatelet therapy was not resumed. MR angiography with gadolinium contrast obtained at 18 months suggested progressive occlusion.

Two years after the endovascular procedure, follow-up angiography was obtained with the intent of placing additional flow diverters if the shunt had not disconnected. The angiographic study demonstrated complete disconnection of the previously seen shunt vascularity marginating the right vertebral artery (Fig. 5). MRA after three years demonstrated persistent disconnection. The patient’s symptoms of dizziness had resolved.

A vertebral artery dural arteriovenous fistula can cause high-pressure arterial blood to flow into low-pressure venous blood, which may affect the normal circulation and function of the brain and spinal cord [1]. The exact cause of VADAVF is unknown, but it may be associated with trauma, surgery, tumors, infections, or inherited prothrombotic conditions [1,10]. Traumatic VADAVF most commonly results from cervical spine trauma [10]. When spontaneous, they may be associated with connective tissue diseases such as fibromuscular dysplasia, Ehlers-Danlos syndrome, and neurofibromatosis type 1 [6].

VADAVFs can occur at any age, but are more common in adults and affect men more than women [1]. Symptomatic DAVF are believed to result from venous hypertension [14]. The symptoms of VADAVF depend on the location and size of the fistula, as well as the pattern of venous drainage. Some common symptoms include pulsatile tinnitus [5], headaches, dizziness, neck pain, cranial nerve palsies, visual disturbances, seizures, stroke, or spinal cord compression.1) The diagnosis of VADAVF is based on clinical history, physical examination, and imaging tests such as CT, MRI, CTA, MRA, and DSA [1].

The relative rarity and complicated anatomy of vertebral artery dAVFs make treatment delicate, with an aim to close the abnormal collection, restore normal blood flow, and maintain patency. Treatment options include surgical and endovascular solutions, with unique risks and benefits involved with each [9,11,12]. Prior to approximately 2010, microsurgical disconnection was the preferred treatment modality for dAVFs within the region of the foramen magnum [9,12]. However, more recent advances in endovascular techniques have changed the treatment paradigm [10].

Endovascular embolization involves delivery of liquid embolic agents to block the abnormal connection or coil occlusion of the recipient dural sinus [1]. Embolization with parent vessel balloon occlusion has shown to be an effective option [4]. However, vertebral artery sacrifice can risk ischemia if contralateral flow is compromised at the time or treatment or at a later time, highlighting the importance of stent placement [5]. Beaujeux et al. described 46 AVFs vertebral AVFs in 45 patients [4]. Thirty-four patients (35 AVFs) were treated endovascularly, most commonly with embolization via a latex balloon filled with contrast. Endovascular treatment accomplished complete occlusion in 91% of cases and partial occlusion in 9%. In three patients, the vertebral artery had to be sacrificed. Singer et al. illustrated a case in which detachable balloons failed to occlude a vertebrojugular fistula. A stent covered by Gortex was then placed across the fistula with success [11].

Incomplete occlusion of cerebrovascular lesions after endovascular treatment is not an uncommon occurrence. There is limited information known about rescue treatment options for AVFs after endovascular treatment. While the pathophysiology varies between AVFs and aneurysms, rescue treatment options may be drawn from literature regarding aneurysm occlusion. Orhan et al. reviewed 14 cases of craniovertebral junction aneurysms, all of which were managed endovascularly [8]. On follow-up, only 57.1% of cases had complete angiographic occlusion. Vertebral artery occlusion occurred in one patient. The authors did not comment on further treatment for partially occluded aneurysms. Al-Mufti et al. reported an approximate 20% failure of aneurysm occlusion after treatment with a flow diverting device [3]. The authors identified that the presence of a device limits further endovascular options in the case of partial occlusion. They recommended either a second device be deployed or alternatively reverting to surgical clipping. Other risks identified with flow diverting device for aneurysm treatment were parent vessel injury in the form of dissection. While the authors generally recommended antiplatelet therapy in the setting of dissection, they noted flow-diverting devices may be a consideration.

Flow diverter consideration was made in this case consequent to the known high-risk rate of covered stent occlusion, post deployment. Al-Lamee et al reported an incidence of definite stent thrombosis of 8.6% in 46 patients [2]. Alternatively, stent angioplasty alone may not have been sufficient to address the plexiform configuration of the peri vascular origin of the shunt. No direct arterial vascular access to the shunt precluded usage of a liquid embolic agent. Dural sinus occlusion with coils, which is the most common endovascular method for dural shunt closure, was not feasible, as this was surgically addressed without success. Angiographic follow up is an important consideration to make a post flow diversion placement, as it may prompt placement of additional implants if the shunt persists.

While advances have continued in endovascular therapies, we provide the first report that describes use of a flow diverter to effectively treat a vertebral artery dAVF. A multidisciplinary team and creative approach remains important in the treatment of this rare pathology.

VADAVF is a challenging condition that requires early diagnosis and treatment to prevent serious complications such as hemorrhage or neurological deficits [1]. The prognosis of VADAVF depends on several factors such as the location and size of the fistula, the pattern of venous drainage, the presence of comorbidities, and the response to treatment [9]. Some patients may have complete recovery after treatment, while others may have residual symptoms or recurrence of the fistula. Rare variant anatomic considerations as identified by angiography in our case, may allow for placement of flow diverters to address this condition successfully, as the first choice or when other options fail.