Posterior condylar canal dural arteriovenous fistulas

Introduction

The posterior condylar vein (PCV) travels through the posterior condylar canal (PCC), serving as a major emissary vein that plays a crucial role in connecting the intracranial and extracranial venous networks.[1,2] The PCC/PCV dural arteriovenous fistulas (DAVFs) are uncommon, with only several cases reported.[3,4,5,6,7,8,9,10,11,12] They are less studied than hypoglossal canal (HC)/anterior condylar vein DAVFs.[13] Transvenous embolization (TVE) is the primary treatment option for PCC DAVFs, which is typically performed through the internal jugular vein (IJV),[3,5,7,8,12] with only one reported through the deep cervical vein (DCV).[10] Here, we present a case of PCV DAVF treated with TVE through the DCV combined with transarterial embolization (TAE) through the middle meningeal artery (MMA). In addition, a literature review was conducted on the topic.

Case Report

A 43-year-old Asian woman presented with right pulsatile tinnitus for 6 months. The patient had no history of trauma, infection, or other medical interventions, but she did have gallstones. The clinical examination showed no abnormalities, specifically ruling out neurological issues, except for the presence of pulsatile tinnitus. The digital subtraction angiography (DSA) showed a PCV DAVF fed by the right ascending pharyngeal artery (AphA), right occipital artery (OA), right MMA, right posterior auricular artery (PAA), and multiple branches from the right vertebral artery (VA) with (IJV and PCV/suboccipital cavernous sinus (SCS) drainage [Figure 1a-d].

Figure 1.

(a-d) Right external carotid and vertebral artery (VA) injection before embolization revealed a posterior condylar canal (PCC) dural arteriovenous fistula (DAVF) supplied by multiple arterial feeders from right ascending pharyngeal artery, right occipital artery, right middle meningeal artery (MMA), right posterior auricular artery, and multiple branches from the right VA with internal jugular vein and posterior condylar vein (PCV)/suboccipital cavernous sinus drainage. (e) A microcatheter was advanced into the venous pouch of the right PCC, passing through the right innominate vein and deep cervical vein. A balloon was subsequently guided to the proximal draining vein and inflated. The fistula and proximal draining vein were embolized with Onyx. (f) A right external carotid artery angiogram injection revealed that there is still arterial supply from the MMA-petrosal branch. (g and h) Onyx was delivered as close as possible to the fistula site and draining vein resulting in complete occlusion of the fistula. Immediate right common carotid and VA injection after treatment showed the fistula was completely occluded. (i-k) 11 years after treatment, the patient complained of headaches and bilateral tinnitus. A repeat digital subtraction angiography did not show a recurrence of the PCV DAVF but revealed a new superior sagittal sinus DAVF. The new DAVF was completely occluded through transarterial embolization. Upon discharge, the patient only complained of mild headache. (l) Schematic diagram of this PCV DAVF case. AphA: Ascending pharyngeal artery, DAVF: Dural arteriovenous fistula, DCV: Deep cervical vein, IJV: Internal jugular vein, IPS: Inferior petrosal sinus, MMA: Middle meningeal artery, OA: Occipital artery, PCV: Posterior condylar vein, SCS: Suboccipital cavernous sinus, SS: Sigmoid sinus, VAVP: Vertebral artery venous plexus

Treatment

To confirm the DAVF’s angioarchitecture, a 5F guide catheter was used under general anesthesia through the right transfemoral approach to access the right external carotid artery and right VA. The patient was scheduled for TVE because of the numerous arterial feeders and dangerous anastomoses. The route from the IJV to the PCV was deemed tortuous, whereas the route from the DCV to the PCV was more appropriate. An Echelon-10 microcatheter (Medtronic, USA) was inserted into the venous pouch of the right PCC, passing through the right innominate vein and DCV/SCS. A HyperForm balloon (Medtronic, USA) (4 mm × 7 mm) was subsequently guided to the proximal draining vein and inflated. The fistula and proximal draining vein were embolized with onyx (Medtronic, USA) [Figure 1e]. However, a right external carotid artery angiogram injection revealed that there is still arterial supply from the MMA-petrosal branch [Figure 1f]. Onyx was delivered as near to the fistula site and draining vein as feasible. Through a Marathon microcatheter (Medtronic, USA), resulting in complete occlusion of the fistula. Postprocedural DSA showed complete obliteration of the DAVF [Figure 1g and h]. No complications were found during or after the procedure (e.g., facial paralysis), and the pulsatile tinnitus was immediately resolved.

Outcome and follow-up

The patient was discharged with no neurological deficits. Afterward, the patient did not undergo regular clinical follow-ups and examinations. The patient complained of bilateral tinnitus and headaches 11 years after starting treatment. A repeat DSA did not reveal a recurrence of the PCV DAVF; however, it disclosed a new parasagittal DAVF primarily supplied by the MMA and the superficial temporal artery, with drainage into the cortical vein and the superior sagittal sinus [Figure 1i and j]. The new DAVF was completely occluded by TAE through the MMA using Onyx [Figure 1k]. On discharge, the patient only complained of mild headache. Schematic diagram of this PCV DAVF case was shown in Figure 1l.

Discussion

Anatomy

Although PCC DAVFs are exceedingly rare, the venous architecture in the lateral foramen magnum region is complex. In cases of PCC DAVF, it is possible to discern venous structures that are not typically visible in normal angiography, offering a unique educational opportunity. Furthermore, a comprehensive understanding of this intricate venous anatomy can greatly improve the efficacy of treatments administered through TVE using an appropriate route. The PCC is a major emissary channel in the skull. It is present, at least unilaterally, in up to 80% of patients and can be easily identified on computed tomography scans.[14] The PCV serves as a connecting vein between the extracranial and intracranial venous systems, traversing the PCC along with the meningeal branch of the OA.[15] The PCV can terminate intracranially at the anterior condylar vein, sigmoid sinus, jugular bulb, or occipital sinus. Its extracranial opening can be either the SCS or DCV.[16,17] Although there is no direct connection between the PCV and the bridging vein,[12] the fistula point of PCC DAVF may be situated at the junction of the PCV and the anterior condylar confluence.[4] This allows for bridging vein drainage around the PCC but may not for PCV drainage.[1,6,11]

Therefore, classifying all PCC DAVFs as low-grade DAVFs is problematic.[12] Some PCC DAVFs may drain through the medulla bridging vein as described above, manifesting as high grade.[5] Their classification is comparable to that of HC DAVFs, with high and low grades.[13]

Literature review

We performed a PubMed search with the terms “posterior condylar” and “arteriovenous fistula,” and further explored the citation lists for additional pertinent publications. Our inclusion criteria encompassed English-language articles that presented comprehensive clinical data and angiographic illustrations for each case; however, duplicate literature and multiple fistulas were excluded from the study. The PCC DAVFs reported in the literature are summarized in Table 1.

Table 1.

Summary of reported cases of posterior condylar canal dural arteriovenous fistulas

	Age	Side	Presentation	Feeder	Draining vein	Cognard/Borden grade	Procedure	Results	Complication
Kiyosue et al.[3]	50s	Left	Tinnitus	AphA, OA, lateral clival artery (ICA), AMA (VA)	IJV, SCS	Low grade	TVE (IJV; coils)	CO	-
Mondel et al.[4]	40s	Right	SAH, IVH	AphA, dural branches (VA), PMA	Bridging vein	High grade	TAE (AphA; Onyx)	CO	-
Maus et al.[5]	Adult	Left	Tinnitus	VA, ascending cervical artery, ECA	IJV, SCS	Low grade	TVE (IJV; coil)	CO	-
Shambanduram et al.[6]	70s	Left	SAH, IVH	PMA	Bridging vein	High grade	TAE (PMA; nBCA)	CO	Brainstem infarction
Brinjikji et al.[7]	Adult	Left	Tinnitus	AphA, OA, VA	IJV, SCS	Low grade	TVE (IJV; coil)	CO	-
Matsuda et al.[8]	70s	Left	Tinnitus	AphA, OA, AMA, PMA, VA, deep cervical artery	IJV, SCS	Low grade	TVE (IJV; coil)	CO	-
Yokogawa et al.[9]	30s	Right	Tinnitus	OA, VA, AphA, PAA, MMA	IJV, SCS	Low grade	TVE (IJV; coil) + TAE (OA; Onyx)	CO	-
Suyama et al.[10]	30s	Right	Tinnitus	AphA, OA, AMA, PMA	SCS, LCV	Low grade	TVE (DCV; coil)	CO	-
Prasad et al.[11]	30s	Right	Intracranial hemorrhage	OA	Bridging vein	High grade	TAE (OA; Onyx)	CO	-
Maekawa et al.[12]	Adult	Left	Tinnitus	OA	IJV, SCS	Low grade	TAE (OA; coil)	CO	-
	Adult	Right	Tinnitus	PMA, AphA	SCS	Low grade	TAE (PMA; coil)	PO	-
	Adult	Right	Tinnitus	OA, PMA, AphA, lateral clival artery (ICA)	IJV	Low grade	TVE (IJV; coil + Onyx)	CO	-
	Adult	Right	Tinnitus	PAA, OA, AphA	SCS	Low grade	Conservative treatment	-	-
Present case	40s	Right	Tinnitus	OA, PAA, AphA, VA, MMA	IJV, SCS	Low grade	TVE (DCV; Onyx) + TAE (MMA; Onyx)	CO	-

AMA: Anterior meningeal artery, AphA: Ascending pharyngeal artery, CO: Complete obliteration, DCV: Deep cervical vein, ECA: External carotid artery, ICA: Internal carotid artery, IJV: Internal jugular vein, IVH: Intraventricular hemorrhage, LCV: Lateral condylar vein, MMA: Middle meningeal artery, OA: Occipital artery, PAA: Posterior auricular artery, PMA: Posterior meningeal artery, PO: Partial obliteration, SAH: Subarachnoid hemorrhage, SCS: Suboccipital cavernous sinus, TAE: Transarterial embolization, TVE: Transvenous embolization, VA: Vertebral artery, nBCA: n-butyl-2-cyanoacrylate

A total of 14 PCC DAVF cases were reported, including one of ours.[3,4,5,6,7,8,9,10,11,12] The average age reported was 45.8 years, ranging from 30 to 72 years. Seven patients (53.8%, 7/13) were female. Eleven (78.6%) patients presented with tinnitus, whereas the other three presented with intracranial hemorrhage. The arterial supplies mainly from the branches of the VA (78.6%), AphA (71.4%), PAA (21.4%), OA (71.4%), MMA (14.3%), dorsal meningeal artery/lateral clival artery (14.3%), and deep cervical artery/ascending cervical artery (14.3%). In 11 (78.6%) patients, venous drainage occurred through the IJV and/or SCS. Three cases were classified as high-grade DAVFs because of the venous drainage through the bridging vein into the pontomedullary venous system.[4,6,11]

Although most PCC DAVFs are benign diseases, their symptoms can be unbearable and have a significant impact on daily life, so the majority are treated with endovascular therapy. TVE alone was performed in six patients, whereas TAE alone was performed in five. Two patients were treated with TVE combined with TAE, whereas one received only conservative treatment. The most common approach for TVE is through the ipsilateral IJV. There are two cases where embolization was performed through the ipsilateral DCV route. The arterial routes included the OA, AphA, MMA, and dural branches of the VA (posterior meningeal artery). In the literature, all fistulas treated with TVE were completely occluded, whereas one case treated with TAE-posterior meningeal artery resulted in partial occlusion. Furthermore, one case treated with TAE experienced complications probability related to the device manipulation.[6] The common embolic materials are coils and Onyx. TAE can be risky because the arterial feeders involved in PCC DAVFs supply the lower cranial nerves and medulla oblongata (e.g., AphA, VA).[15,18] Dangerous anastomoses between the AphA and intracranial arteries can lead to ischemic stroke as well.[19] Given that sacrificing, the PCV is deemed safe in neurosurgical procedures, obliterating this vein in PCC DAVF is also considered safe. When planning the obliteration of the jugular vein or SCS, careful study of the cerebral venous flow is essential. If the draining veins of the DAVF do not contribute to the normal cerebral venous outflow, they can be safely sacrificed. Otherwise, this may result in potential venous drainage restriction and venous hypertension. TVE is considered the primary treatment for low-grade PCC DAVFs, but for high-grade PCC DAVFs, TAE is still preferred as it cannot be possible to reach the venous side through TVE.[4,6,11]

Conclusion

The PCC/PCV DAVFs are uncommon, with only several cases reported. They are not well studied as HC DAVFs. PCC DAVF can be classified into high grade and low grade, similar to HC DAVF, with the majority being low grade. TVE is often used as the primary treatment for low-grade PCC DAVF. The transvenous route can be ipsilateral IJV or DCV. TAE is employed as the primary treatment for high-grade PCC DAVF or adjunctive treatment modality. However, TAE can be risky as it may cause lower cranial nerve palsy, cerebral, and brain stem infarction. The lesions in this location have a high cure rate and patients have a good prognosis.

Author contributions

Conception and design: Xin Su, Tongyue Li, Jiachen Wang. Acquisition of data: Xin Su, Tongyue Li, Jiachen Wang. Drafting the article: Xin Su. Critically revising the article: Yongjie Ma, Peng Zhang, Hongqi Zhang. All of the authors have read and approved the final manuscript.

Ethical policy and institutional review board statement

Not applicable.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

This study was funded by the National Natural Science Foundation of China (No. 82101460).