Anterior condylar arteriovenous fistula (ACAVF) is an osseous AVF that forms around the hypoglossal canal [1,2]. Transvenous embolization (TVE) is the first-line treatment for this condition [3]. However, catheterization can be challenging as a result of factors such as complex vascular anatomy, vessel overlap, three-dimensional tortuosity, and thrombosis [4]. Herein, we report a case in which catheterization was successfully performed by creating a roadmap using the 3D polyline function during TVE, for an ACAVF in which the access route was unclear because of overlapping vessels.

A 46-year-old man with no history of trauma visited our hospital complaining of diplopia and pulsatile tinnitus that had been present for two months. Intermittent congestion in the right eye, right oculomotor nerve palsy, and bruit in the mastoid region were observed. MRI revealed high signal intensity around the right hypoglossal canal on time-of-flight imaging. Cerebral angiography showed that the right ACAVF was mainly supplied by the right ascending pharyngeal artery (APhA) with multiple shunt points converging around the right condyle, and primarily drained through the anterior condylar confluence (ACC) to the internal jugular vein (IJV; Figure 1A). The ACC draining into the IJV was faintly visualized, and reflux from the right inferior petrosal sinus (IPS) to bilateral cavernous sinuses was also observed. Furthermore, the IJV also retroactively drained into the sigmoid sinus and the vertebral venous plexus via the posterior condylar vein. Three-dimensional rotational angiography (3D-RA) revealed that multiple shunt points converged into an intraosseous venous pouch posterior to the hypoglossal canal, which then drained into the ACC via the anterior condylar vein and further into the pre-vertebral vein. Feeding from the contralateral external carotid artery (Figure 1B), and bilateral vertebral arteries via each anterior meningeal artery were also observed (Figure 1C, D), and the bilateral internal carotid arteries fed slightly as well. In addition to a six-vessel study, selective angiography was performed on the right anterior meningeal artery and right APhA, but visualization of the access route for TVE was difficult because of the overlapping vessels. We then examined the multiplanar reconstruction (MPR) of the right external carotid artery obtained via 3D-RA, which clearly showed the draining route from the venous pouch to the IJV. However, the draining route was tortuous, so we tried to create a visual access route–or “roadmap,” using the 3D polyline function on a 3D workstation (syngo, Toolbox, Siemens Healthineers AG, Forchheim, Germany; Figure 2).

Figure 1: Preoperative angiographic studies, anterior-posterior view.

(A) The right external carotid angiogram shows an arteriovenous fistula primarily supplied by the right ascending pharyngeal artery, with multiple shunt points converging around the right condyle. The fistula mainly drained into the internal jugular vein, with reflux into the cavernous sinus via the right inferior petrosal sinus. (B) The left contralateral external carotid artery shows minimal feeding. (C) The right vertebral artery and (D) left vertebral artery supply the lesion via each anterior meningeal artery.

Figure 2: A preoperative screenshot of the 3D workstation.

A preoperative screenshot of the 3D workstation creating an access route using the 3D polyline function. The draining route (double arrow) is plotted from the internal jugular vein (arrow head) to the venous pouch (asterisk) on the multiplanar reconstruction (MPR) obtained via 3D rotational angiography of the right external carotid artery. The plotted route, or “roadmap,” was projected onto the 3D screen  (bottom right). The thickness of MPR images in this figure is 4 mm, to clearly depict the draining route.

Creation Procedure

First, on one of the three MPR cross-sectional images obtained by 3D-RA, the direction was finely adjusted so that two points—the confluence of the ACC and IJV, and the venous pouch to be embolized—were captured on the same plane. The draining route was then plotted onto that MPR image. Next, the plotted route displayed on the other two MPR images was finely adjusted to match the meandering of the draining route on each image. At this time, the route was made as thin as possible to create an accurate path, while also ensuring that it would not be lost in the thin images. This generated the roadmap on a 3D screen, which we then used to attempt TVE.

 Under general anesthesia, a 4 Fr angiographic catheter was placed in the right APhA, And an 8 Fr guiding catheter (Fubuki; Asahi Intecc) was guided into the right IJV, and a 3.2 Fr distal access catheter (Guidepost; Tokai Medical Products) was used. A catheter (Excelsior SL-10; Stryker) was first guided into the right ACC using a 0.014″ outer diameter guidewire (Synchro SELECT; Stryker). We then attempted to guide the SL-10 distal to the ACC, but the ACC was sharply angled, causing kickback to the distal IPS (Figure 3A). Therefore, we attempted to prevent this kickback by temporarily placing a coil in the IPS. Another catheter (Headway 17; MicroVention) was inserted into the guiding catheter, and was guided to the IPS with a 0.014″ outer diameter guidewire (CHIKAI; Asahi Intecc), and a coil (Target XL 360 Soft 4mm × 8cm; Stryker) was placed in the IPS without detaching. This coil enabled the SL-10 to be guided relatively easily to the distal part of the ACC (Figure 3B). Since further distal guidance was not possible, 3D-RA was performed to confirm the position of the catheter tip. This revealed that the catheter had reached the orifice of the hypoglossal canal (Figure 4A), and that the entrance to the target venous pouch was narrow. Therefore, we attempted to create a roadmap using a 3D polyline. The procedure was almost identical to the method used before this operation, but this time we plotted the draining route between the catheter tip and the venous pouch (Figure 4B–D). By overlapping this the 3D polyline roadmap onto the fluoroscopy screen, we were able to guide the catheter to the venous pouch confidently (Figure 4E, F).

Figure 3: Intraoperative fluoroscopic image.

(A) Catheterization was attempted at the anterior condylar confluence (ACC), but was kicked back toward the inferior petrosal sinus (arrow). (B) Assisted by a coil temporary placed on the inferior petrosal sinus (double arrow), the catheter was successfully navigated distal to the ACC.

Figure 4: Intraoperative screen of the 3D workstation.

Intraoperative screen of the 3D workstation obtained via 3D rotational angiography of the right ascending pharyngeal artery and intraoperative fluoroscopic images: (A) Axial section of the multiplanar reconstruction (MPR) showing the catheter tip (long arrow) reaching the hypoglossal canal. The venous pouch (asterisk) was separated by a thin wall  (short arrow) and connected via a narrow orifice. The thickness of this MPR is 0.3 mm, in order to visualize the small structures involved. (B) Axial section, and (C) Coronal section of the MPR after plotting the draining route between the catheter tip and the venous pouch using the 3D polyline function. The thickness of  these MPRs is 5 mm, to allow for clear visualization of the draining route and catheter. (D) The access route, or “roadmap,” drawn in the 3D screen show the working angle. (E) Fluoroscopy showing the catheter to be navigated with the roadmap overlaid (not shown). (F) Fluoroscopy showing the catheter reaching the venous pouch, with  the catheter curve following the previously created roadmap.

After confirming the position of the catheter tip using cone-beam CT, selective coil embolization was performed on the three main shunt points (seven coils, total 24cm) to reduce the shunt flow rate. The venous pouch was then sparsely embolized using four coils (total 80cm), resulting in the disappearance of the shunt (Figure 5A). The patient’s symptoms disappeared immediately following this operation, and he was discharged on the third postoperative day. Informed consent was obtained from the patient for the publication of this report.

Figure 5: Postoperative right external carotid angiogram and head CT.

(A) Anteroposterior view showing disappearance of the arteriovenous shunt. (B) Bone CT demonstrating the coil mass packed into the clivus.

The diseases previously known as IPS dAVF, marginal sinus dAVF, and hypoglossal canal dAVF are now considered to be the same pathology and are collectively referred to as ACC dAVF [5]. When the shunt is clearly located within the bone, as it was in the present case, it has more recently been reported as osseous AVF, [2] anterior condylar AVF [6], and even condylar AVF [7]. This condition is rare, accounting for only 3.8% of intracranial AVFs [8]. Owing to its complex anatomical characteristics, the associated symptoms can be diverse. These include tinnitus, ocular symptoms such as exophthalmos and diplopia, hypoglossal nerve palsy, and brainstem and spinal cord symptoms [5]. Aggressive symptoms such as bleeding and venous infarction have also been reported [3].

 TVE is an effective treatment for this condition; however, the access route can be problematic both visually and technically, because of overlapping vessels, three-dimensional tortuosity, and thrombosis. Previous reports have shown that the shunt point was visualized through contralateral angiography [9] or superselective angiography [4], and that a detouring access route was selected [10]. In our case, the access route could not be clearly visualized by contralateral or superselective angiography.

Conversely, the MPR images we obtained via 3D-RA of the APhA confirmed that the draining route was continuous from the shunt point to the IJV. This technique of using a 3D polyline function as a roadmap during surgery in endovascular therapy has not yet been reported in the literature, to our knowledge.

When treating ACAVF, identification of the shunt points or catheter position can be problematic because of the presence of overlapping vessels in the region. To address this, methods for identifying the catheter or coil position have been reported, using cone-beam CT [4,6,11], or image fusion techniques [12]. One related report detailed the use of a 3D polyline for navigation during percutaneous transthoracic needle biopsy [13]. We applied these techniques to endovascular therapy of an ACAVF with a complex vascular structure, allowing catheterization to be performed with relative ease. The original function of the 3D polyline is to measure the length of tortuous vessels, but the plotted route displayed on the 3D workstation can be rotated in any direction. This route can then be used to determine working angles and serve as a roadmap during the operation, making it particularly useful for endovascular treatment of cases with complex vascular structures.

We used a Siemens system, but similar processing can be done using other systems as well. It should be noted that this method requires practice in terms of plotting on a two-dimensional MPR. Additionally, since the MPR to be plotted is a thick image, there is a possibility that certain routes are not actually continuous, as thin partitions may be depicted as continuous. When working with thin images, it is also possible to lose track of the drainage route, so the thickness of the image should be adjusted appropriately during the process.

 Because the ACC has a complex branching course, catheterization can be technically challenging. In the present case, the catheter was kicked back into the IPS when we attempted to guide it into the ACC. To prevent this, a coil was temporarily placed in the IPS to prevent the catheter from kicking back. Previous reports have described the use of balloons [14], or shaped catheters [15], in similar scenarios. The advantages of our method are that the blood vessel is not completely occluded during assistance, and the coil can be retrieved to reduce artifacts or be used for embolization.

The limitations of this report include that it is a single case report and the approach used was not a first-line method. Further cases required to confirm the validity of this approach.

Herein, we report a case in which a roadmap was created using the 3D polyline function during TVE for an ACAVF, and catheterization was performed with the assistance of a temporary coil. Both methods appear to be effective treatment strategies for TVE in case of AVF with complex vascular structures.

Acknowledgments

We would like to thank Editage (www.editage.jp) for English language editing.

Disclosure of conflict of interest

The authors declare that they have no conflicts of interest.

1. Hiramatsu M, Sugiu K, Haruma J, Hishikawa T, Takahashi Y, Murai S, et al. Osseous arteriovenous fistulas in the dorsum sellae, clivus, and condyle. Neuroradiology. 2021; 63: 133-140.
2. Mizutani K, Akiyama T, Yoshida K. The anterior condylar arteriovenous fistula from the viewpoint of the osseous venous anatomy. J Neuroendovascular Therapy. 2019; 13: 97-104.
3. Spittau B, Millan DS, El-Sherifi S, C Hader, TP Singh, E Motschall, et al. Dural arteriovenous fistulas of the hypoglossal canal: systematic review on imaging anatomy, clinical findings, and endovascular management. J Neurosurg. 2015; 122: 883-903.
4. Miyachi S, Ohshima T, Izumi T, Kojima T, Yoshida J. Dural arteriovenous fistula at the anterior condylar confluence. Interv Neuroradiol. 2008; 14: 303-311.
5. Arai D, Sasagasako T, Yoshida S, Park S, Miyakoshi A, Kawanabe Y, et al. A patient with an anterior condylar confluence dural arteriovenous fistula in whom reflux to the anterior medullary vein was observed during follow-up. J Neuroendovascular Therapy. 2021; 15: 360-365.
6. Matsukawa S, Ishibashi R, Goto M, Terada Y, Hashikata H, Iwasaki K, et al. Cone-beam CT-assisted microcatheter tip placement at the shunted pouch entry zone: A technical note for anterior condylar arteriovenous fistula. Neuroradiol J. 2022; 36: 236-240.
7. Tsuruta W, Sekine T, Ishigami D, Fujitani S, Tomioka A, Kamiya Y, et al. Ventral clival branch of the ascending pharyngeal artery as a transosseous feeder of an arteriovenous fistula surrounding the clival lesions. Clinical Neuroradiology. 2023; 33: 467-474.
8. Hiramatsu M, Sugiu K, Hishikawa T, Nishihiro S, Kidani N, Takahashi Y, et al. Results of 1940 embolizations for dural arteriovenous fistulas. Japanese Registry of Neuroendovascular Therapy (JR-NET3). J Neurosurg. 2019; 28; 1-8.
9. Kimura G, Ikeda H, Nishi R, Hata H, Uezato M, Kinosada M, et al. Anterior condylar arteriovenous fistula mainly fed by peripheral branches of the bilateral internal maxillary arteries: illustrative case. J Neurosurg Case Lessons. 2023; 6: CASE23452.
10. Tanoue S, Goto K, Oota S. Endovascular treatment for dural arteriovenous fistula of the anterior condylar vein with unusual venous drainage: report of two cases. AJNR Am J Neuroradiol. 2005; 26: 1955-1959.
11. Okumura A, Nakaoka M, Ohbayashi N, Yahara K, Nabika S. Intraoperative cone-beam computed tomography contributes to avoiding hypoglossal nerve palsy during transvenous embolization for dural arteriovenous fistula of the anterior condylar confluence. Interv Neuroradiol. 2016; 22: 584-589.
12. Choi JH, Cho DY, Shin YS, Kim BS. Intraprocedural flat panel detector rotational angiography and an image fusion technique for delivery of a microcatheter into the targeted Shunt Pouch of a Dural Arteriovenous Fistula. Am J Neuroradiol. 2020; 41: 1876-78.
13. Han YM, Kim KY. Using 3D polylines to improve cone-beam CT-guided percutaneous transthoracic needle biopsy. Br J Radiol. 2022; 95: 20220406.
14. Shimizu N, Suzuki K, Fujii Y, Yuki I, Yoshiki S, Yosuke K, et al. Balloon-assisted coil embolization for anterior condylar confluent dural arteriovenous fistula. J Neuroendovascular Therapy. 2015; 9: 179-186.
15. Hiraoka F, Nii K, Inoue R, Mitsutake T, Sakamoto K, Eto A, et al. Selection of guiding catheter based on the anatomical structures when performing TVE to treat an anterior condylar confluence dural AVF. J Neuroendovascular Therapy. 2015; 9: 179-186.