The variant with the absence of the superior petrosal venous and sinus: A potential pitfall of transvenous balloon-assisted embolisation of Borden type II transverse-sigmoid dural arteriovenous fistula

Abstract

We describe a patient with Borden type II transverse-sigmoid dural arteriovenous fistula. On the venous phase of the left vertebral artery injection, there was no superior petrosal veins and sinus on the side of lesion. After transvenous balloon-assisted Onyx embolisation, the patient developed extensive venous infarction from venous occlusion. This report calls attention to a highly unusual variant in which the superior petrosal veins and sinus are absent, and the cerebellar veins will be drained by tributaries of the bridging veins in this circumstance. In such circumstances, occlusion of the bridging vein on the tentorial cerebellar surface may lead to complications during transverse-sigmoid dural arteriovenous fistula embolisation.

Introduction

Transarterial Onyx (Medtronic, ev3, USA) embolisation is an accepted and effective method of treatment for dural arteriovenous fistulas (DAVFs), but it is not without morbidity and mortality related to the procedure itself.^1–4 In transverse-sigmoid DAVFs, Onyx embolisation through the middle meningeal artery poses a considerable risk of reflux into the transverse-sigmoid sinus (TSS).^5,6 When these problems are kept in mind, the embolisation to these branches is often combined with transvenous balloon protection of the TSS.^7–10 Complications caused by venous thrombosis after DAVF embolisation have been reported occasionally.¹¹ We recently treated a patient who died of massive cerebellar oedema due to venous outlet restriction after transvenous balloon-assisted Onyx embolisation.

Case description

A 22-year-old woman presented with a 3-month history of tinnitus. Magnetic resonance imaging (MRI) was normal (Figure 1). A diagnostic cerebral angiogram demonstrated a complex Borden type II DAVF of the left TSS. Left external and internal carotid angiography demonstrated that feeding arteries were meningeal arteries of the left external carotid artery and meningohypophyseal trunk (Figure 2(a) and (b)). On the venous phase of the left vertebral artery injection, the left superior petrosal vein and sinus were absent, and the tributaries draining the cerebellar surface formed bridging veins that drained into the transverse sinus (Figure 2(c)).

Figure 1.

Magnetic resonance imaging, T2-weighted, was normal.

Figure 2.

(a) Lateral view of left external carotid artery injection. (b) Lateral view of left internal carotid artery injection, showing a complex Borden type II transverse-sigmoid dural arteriovenous fistula supplied by meningeal branches of the left external carotid artery and meningohypophyseal trunk. (c) Venous phase, frontal view of left vertebral artery injection showing the superior petrosal veins and sinus on the right side (arrow heads). On the left side, the left superior petrosal veins and sinus were absent. The inferior hemispheric vein formed a bridging vein on the tentorial cerebellar surface, which drained through a short bridging vein into the transverse sinus (arrow). (d) Lateral view of injection of Onyx assisted by transvenous balloon inflation. Asteroid shows the microcatheter tip. The Onyx packed the shunts and then reversed into the bridging veins of the Labbe vein (arrowhead) and the tentorial cerebellar surface (arrow). (e) Lateral view of post-embolisation arterial phase of the left carotid artery showing complete occlusion of the dural arteriovenous fistula. (f) Lateral view of post-embolisation venous phase of the left carotid artery showing the patent left transverse-sigmoid sinus and restricted Labbe venous drainage.

Embolisation was performed from a transfemoral transarterial approach under general anaesthesia. The microcatheter (Echlon10; Medtronic, USA) was passed through the guiding catheter and its tip was inserted into the meningeal branches of the left external carotid artery. Onyx embolisation was from the middle meningeal artery and ascending pharyngeal artery. During Onyx injection, the TSS was protected using a 8 × 80 mm Copernic balloon. During the middle meningeal artery embolisation, the Onyx was found to reflux into the bridging vein (Figure 2(d)). A postoperative angiogram demonstrated that almost total obliteration of the DAVF was achieved, and patency of the left TSS was preserved (Figure 2(e) and (f)). The bridging veins were closed by the retrograde approach during sinus occlusion. The vein of Labbe was restricted on the post-embolisation venous phase (Figure 2(f)). The patient presented with sudden and progressive disturbance of consciousness 10 hours after treatment. MRI revealed venous infarction changes of cerebellar swelling on the left side with brain stem involvement (Figure 3(a)). Subsequently, she underwent external ventricular drainage, infarcted cerebellar tissue resection and posterior fossa decompressive craniectomy (Figure 3(b)). There was progressive deterioration in her Glasgow coma scale, and the patient matched the brain death criterion one month after embolization despite all efforts.

Figure 3.

(a) Sagittal magnetic resonance imaging revealed left cerebellar and brain stem venous infarction. (b) Computed tomography scanning showing the posterior fossa decompressive craniectomy.

Discussion

We report a variant of absence of the superior petrosal vein and sinus as a pitfall of transvenous balloon-assisted Onyx embolisation of a Borden type II TSDAVF. We speculate that the death was caused by the cerebellar and brain stem oedema from the venous outlet restriction. The deployment of a balloon in the TSS lumen during embolisation can not protect the bridging vein drainage. Transarterial Onyx embolisation is a well accepted and widely used technique in the management of DAVF.^1,2,12,13 It is a complex procedure requiring a deep knowledge of the meningeal artery and venous drainage anatomy including the possible vessel anastomoses.⁴ It has been reported that diffuse venous thrombosis may develop after transarterial DAVF embolisation with the potential to cause severe morbidity and mortality.^1,11 The typical structure of a TSDAVF is a direct multi-hole fistula involving a broad surface in length or circumference of the sinus wall.¹⁴ In the experience of Xu et al.,² the overall complete or near-complete occlusion rate is 82% of patients, 4.5% of patients experienced a transient neurological deficit (cranial nerve VII), 4.5% of patients with cortical venous reflux who had received incomplete treatment died of intracranial haemorrhage during the follow-up period.

According to the experience of this case, we think that the prevention of pial vein flow is most important but sometimes it is very complex and difficult. The pial veins should be searched whenever an embolisation procedure is attempted, because they increase the risk of non-targeted embolisation as in our case or failure of the procedure. The superior petrosal veins, known collectively as the ‘petrosal vein’, or ‘Dandy’s vein’, are one of the most constant and largest venous complexes in the posterior fossa,¹⁵ and may result in complications if occluded. The superior petrosal veins, described as one to three bridging veins, emptying into the superior petrosal sinus, are the major drainage pathways of posterior fossa veins. In the case presented, the superior petrosal vein and sinus were absent and venous drainage was through the bridging vein on the tentorial cerebellar surface into the TSS.¹⁶ Knowledge of the possible anatomical variations is considered to be essential to improve TSDAVF strategies.

Venous drainage is an important consideration in DAVF treatment. Sacrifice of veins may result in postoperative venous complications, which are difficult to predict due to the many anastomoses and variations in the venous system. Authors have reported and implied cerebellar infarction after division of the bridging veins on the tentorial cerebellar surface.^17,18 Page reported a case in which severe cerebellar swelling occurred after the division of one hemispheric and all vermian bridging veins.¹⁹

We emphasised the importance of the meticulous planning of DAVF and avoidance of bridging vein occlusion. The question frequently arises of whether to preserve the bridging veins. The difficulty in predicting outcomes is due to the many variations of venous anatomy and multiple anastomotic connections. Even with recent advances in preoperative venous assessment, it is difficult to determine whether a vein can be safely sacrificed. An attempt to preserve veins may lead to residual of DAVF and bleeding complications of DAVF embolisation.

Currently the size of the vein obliterated may be the most valuable predictor of whether complications will follow. Advances in preoperative venographic examination may also help. Neuroimaging studies known to be reliable for examining the superior petrosal veins, sinus and the bridging veins include digital subtraction venography, computed tomography or magnetic resonance venography.^20–25 Preoperative radiological examination may aid in selecting the approach.

Conclusion

The superior petrosal vein and sinus are occasionally absent, and venous drainage is by tributaries of the tentorial sinus in this circumstance. In such unique cases, occlusion of the bridging vein on the tentorial cerebellar surface may lead to complications during TSDAVF embolisation. Embolisations of venous structures in DAVF are still controversial, but an understanding of the variations of venous anatomy is essential, preoperative radiological assessment is necessary.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.