Intraoperative cone-beam computed tomography contributes to avoiding hypoglossal nerve palsy during transvenous embolization for dural arteriovenous fistula of the anterior condylar confluence

Abstract

Background: Dural arteriovenous fistula of the anterior condylar confluence (ACC-DAVF) is a rare subtype of DAVFs that occurs around the hypoglossal canal. Transvenous embolization (TVE) with coils has been performed for most ACC-DAVFs with a high clinical cure rate. However, some reports call attention to hypoglossal nerve palsy associated with TVE due to coil mass compression of the hypoglossal nerve caused by coil deviation from the ACC to the anterior condylar vein (ACV). Herein, we report a case of ACC-DAVF in which an intraoperative cone-beam computed tomography (CT) contributed to avoiding hypoglossal nerve palsy.

Case presentation: A 74-year-old man presented with left pulse-synchronous tinnitus. An angiography detected left ACC-DAVF mainly supplied by the left ascending pharyngeal artery and mainly drained through the ACV. The two fistulous points were medial side of the ACC and the venous pouch just cranial of the ACC. We performed TVE detecting the fistulous points by contralateral external carotid angiography (ECAG). The diseased venous pouch and ACC were packed with seven coils but a slight remnant of the DAVF was recognized. Because a cone-beam CT revealed that the coil mass was localized in the lateral lower clivus osseous without deviation to the hypoglossal canal, we finished TVE to avoid hypoglossal nerve palsy. Postoperatively, no complication was observed. No recurrence of symptoms or imaging findings were detected during a five-month follow-up period.

Conclusion: An intraoperative cone-beam CT contributed to avoiding hypoglossal nerve palsy by estimating the relationship between the coil mass and the hypoglossal canal during TVE of ACC-DAVF.

Keywords: Anterior condylar confluence; cone-beam computed tomography; dural arteriovenous fistula; hypoglossal nerve palsy; transvenous embolization.

Figure 1.

Images on admission: ((a), (b)) Time-of-flight MRA source image and MRA showing high intensity around the left hypoglossal canal (white arrow). MRA: magnetic resonance angiography; MRI: magnetic resonance imaging.

Figure 2.

Preoperative angiographic studies: ((a), (b)) A left ECAG showing left ACC-DAVF ((a) anterior-posterior view. (b) lateral view). The ACC (arrow) was mainly supplied by the left APA. Although the ACV (double arrow) showed as a main drainer, the ipsilateral angiography failed to reveal the fistulous points because of overlapping of vessels. (c) A right, contralateral, ECAG of the anterior-posterior view showing the right APA and maxillary artery flowing into the ACC and the venous pouch just cranial of the ACC. The two fistulous points (arrow head) were medial side of the ACC and the venous pouch. The ACC was drained caudally through the ACV and LCV to VVP, laterally to the IJV, and cranially slightly to the IPS (white arrow). (d) A schematic drawing of the anterior-posterior view of the feeding arteries, fistulous points, draining veins, and hypoglossal canal. ACC: anterior condylar confluence; ACV: anterior condylar vein; APA: ascending pharyngeal artery; DAVF: dural arteriovenous fistula; ECAG: external carotid angiography; IJV: internal jugular vein; IPS: inferior petrosal sinus; LCV: lateral condylar vein; VVP: vertebral venous plexus.

Figure 3.

Intraoperative findings during TVE. (a) A right ECAG showing the venous pouch, which was embolized with two coils, total length: 18 cm. The Excelsior SL-10 microcatheter was pushed out from the venous pouch to the ACC. (b) A sequential right ECAG showing the ACC, which was embolized with five coils, total length: 50 cm. (c) A right ECAG not visualizing the ACC-DAVF. (d) A left CCAG showing a slight remnant of the DAVF (double arrow). ((e), (f)) A cone beam CT showing that the coil mass was localized in the lateral lower clivus osseous without deviation to the hypoglossal canal. (g) Postoperative MRA five months after TVE not visualizing high intensity around the left hypoglossal canal. ACC: anterior condylar confluence; CCAG: common carotid artery angiography; CT: computed tomography; DAVF: dural arteriovenous fistula; ECAG: external carotid artery angiography; MRA: magnetic resonance angiography; TVE: transvenous embolization.