Acute Formation of a Blunt Trauma-induced Vertebral Artery Arteriovenous Fistula Treated with Endovascular Occlusion of Vertebral Artery

Fistulous cerebrovascular injuries can occur spontaneously, iatrogenically following surgical procedures, or can result as a consequence of penetrating trauma. To our knowledge, this is only the second reported case of blunt-trauma induced cervical vertebral artery arteriovenous fistula (AVF) formation in a 55-year-old male. This was successfully occluded with N-butyl cyanoacrylate (NBCA) embolization of the recipient vein and endovascular coil ligation of the vertebral artery.


Introduction
Arteriovenous fistulas (AVF) of the vertebral artery are rare vascular malformations of the spinal vasculature that can present after cervical spine surgery, central venous catheterization, chiropractic manipulations, diagnostic cerebral angiography, percutaneous nerve blocks, radiation therapy, penetrating traumatic injury, or even more rarely blunt traumatic injury. We present a case of a 55-yearold male who sustained an AVF of the vertebral artery after a blunt traumatic mechanism. This vertebral artery AVF was treated promptly with an endovascular sacrifice of the parent vertebral artery with subsequent obliteration of this fistula.

Case Presentation
A 55-year-old male with past medical history significant for schizophrenia presented to the emergency department (ED) after being found unresponsive outside by family members at his residence. The presumed mechanism was a traumatic fall off the patient's porch, but this was unwitnessed. Paramedics reported a Glasgow coma score (GCS) of 3 in the field and he was intubated for airway protection. He was hemodynamically stable on arrival to the ED. Neurologically, his pupils were equal and reactive to light, and brainstem reflexes were all intact. He did not display any movements to noxious stimuli in all his extremities. Computed tomography (CT) and computed tomography angiography (CTA) of the head and cervical spine were significant for unstable vertical shear fractures involving the posterior cortices of C1, C2, C3, and C4. Additionally, there was evidence of contrast extravasation from the distal V2/proximal V3 segment of the left vertebral artery ( Figure 1A, 1B). To further evaluate for left vertebral artery injury, the patient underwent a catheter-based digital subtraction angiogram (DSA) on the first day of hospitalization. DSA demonstrated an AVF at the left V2/V3 vertebral artery junction with an enlarged ectatic recipient vein draining into the perimedullary and deep venous structures ( Figure 2A). In anticipation of surgical stabilization of the cervical spine fractures, endovascular disconnection of the shunt vascularity was performed under general anesthesia. An Excelsior SL-10 (Stryker, Kalamazoo, MI, USA) microcatheter was used to catheterize the recipient vein. N-butyl cyanoacrylate (NBCA) of 3 mL was injected under fluoroscopic observation ( Figure 2B). This resulted in a reduction of fistulous flow through the AVF ( Figure 3A). A 4 mm x 20-mm TransForm Balloon catheter (Stryker, Kalamazoo, MI, USA) was then advanced through the distal aspect of the left cervical vertebral artery to prevent reflux of the embolic material into the basilar artery. An Excelsior SL-10 microcatheter was then advanced into the residual AVF, and an additional 3 mL of NBCA was injected ( Figure 3B). The TransForm Balloon catheter was removed, and subsequent angiographic imaging revealed persistent filling of the AVF. Due to the pending cervical spine surgery, the decision at this time was to endovascularly ligate the left vertebral artery to avoid stent placement and the need for dual antiplatelet therapy. Ligation of the left vertebral artery was accomplished with the deployment of nine Target 360 detachable coils (Stryker, Kalamazoo, MI, USA), and two Tornado embolization coils (Cook Medical, Bloomington, IN, USA; Figure 4A). This resulted in complete angiographic obliteration of the left vertebral artery with adequate flow through the nondominant right vertebral artery, basilar artery and the left posterior inferior cerebellar artery ( Figure 4B). On post-procedure day one, the patient improved neurologically, demonstrated by an improvement in GCS from 3T to 8T. He was localizing to noxious stimuli with the left upper extremity and withdrawing to noxious stimuli in the left lower extremity. He would open his eyes to voice. On post-procedure day two, the patient underwent a posterior occipito-cervical stabilization with occipital titanium cables, lateral mass screws, and connecting rods for his unstable vertical shear fractures from C2 to C4. There were no intraoperative or perioperative complications and the patient was transferred to the intensive care unit postoperatively.
His neurologic status slowly improved throughout the remainder of his hospitalization. Prior to discharge, he was able to open his eyes spontaneously and track objects across his visual fields bilaterally. His brainstem reflexes remained intact. He did not follow commands but continued to localize in the left upper extremity. His right upper and lower extremities withdrew to noxious stimuli. His GCS was 10T upon discharge.
In order to better prognosticate rehabilitation potential, an magnetic resonance image (MRI) brain was performed on the sixth day of hospitalization, which demonstrated small areas of punctate acute infarcts involving the left cerebellar hemisphere, but no evidence of large vessel or brainstem strokes to suggest ongoing vertebrobasilar ischemia. The punctate infarcts are believed to be reflective of hypoperfusion or thromboembolic phenomena related to the initial injury to the left vertebral artery. The patient additionally underwent tracheostomy and percutaneous endoscopic gastrostomy tube placement on days 11 and 12 of admission, respectively. He was weaned from full ventilatory support and was tolerating tracheostomy collar prior to discharge. He was sent to a long-term acute care facility for rehabilitation on post-interventional procedure day 13.

Discussion
Acquired spinal AVFs are rare vascular malformations of the spine. Typically, they present after an iatrogenic injury during cervical spine surgery, central venous catheterization, chiropractic manipulations, diagnostic cerebral angiography, percutaneous nerve blocks, radiation therapy, or penetrating traumatic injury [1][2][3][4][5]. Spinal AVFs can present with symptoms of myelopathy or cervical neuralgia due to arterial blood reflux into spinal pial veins or after root compression by engorged epidural veins [6]. The timing of the development of symptoms is related to the flow velocity, venous drainage pattern, and lesion chronicity [7]. Arterial steal via rapid blood flow or altered venous drainage causing venous hypertension is the primary pathophysiologic mechanism by which acute neurologic deterioration occurs [8][9].
Blunt traumatic injury is an extremely rare etiology of spinal AVFs. We present the second reported case of cervical spinal AVF developing after blunt traumatic injury, sustained after a fall with fracture dislocations of the upper cervical spine. Heuer et al. reported the only other case in the literature of a spinal AVF developing after a blunt traumatic injury. Their report described a young male who presented after a motor vehicle accident with a C2 fracture. [10] The patient developed symptoms of upper and lower extremity weakness six hours after presenting with a normal neurologic exam. MRI of the cervical spine with magnetic resonance angiography and venography (MRA/MRV) demonstrated a probable high cervical cord AVF off of the right vertebral artery. [10] Digital subtraction angiography (DSA) showed complete transection of the distal cervical aspect of the right vertebral artery at the level of the base of C2 with anterograde and retrograde blood flow into a direct AVF, resulting in early filling of the right internal jugular vein and other external draining veins [10]. The patient was treated with coils proximal and distal to the vertebral artery transection [10]. Obliteration of the recipient venous pouch with NBCA and proximal sacrifice of the feeding vertebral artery as a method of shunt disconnection has not been previously described.
Historically, open surgery was used to treat spinal AVFs via proximal and distal trapping with surgical excision of the fistula [11][12]. However, there were significant morbidity and high failure rates via open surgery [11][12]. This was likely due to ineffective proximal vertebral artery ligation because of the extensive anastomotic circulation between the external carotid and vertebral arterial systems [13][14]. Due to advancements in endovascular technology and technique, spinal AVFs can be treated with low morbidity and high treatment success via obliteration of the fistula and preservation of flow in the parent vertebral artery [15][16]. Herrera et al. reported a case series of patients who developed spinal AVFs treated primarily via vertebral artery occlusion [7]. In their case series, patients presented with symptoms of cephalgia, cervical radiculopathy, subarachnoid hemorrhage, stiff neck, tinnitus, and myelopathy [7]. The authors demonstrated that endovascular treatment can be safely accomplished whenever the contralateral vertebral artery is adequate to supply both intracranial vertebral circulations, as was in our case.

Conclusions
Cervical vertebral artery injury after blunt traumatic injury is extremely rare and vascular imaging in such instances is important, especially when an associated osseous injury is identified. In such cases of acquired vertebral artery AVF, endovascular treatment is a safe and effective method of shunt disconnection.

Additional Information Disclosures
Human subjects: Consent was obtained by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.