Intra-arterial onyx embolisation of sphenobasilar sinus fistula using pressure cooker technique: case report and review of the literature

Abstract

Dural arterio-venous fistulas of the middle cranial fossa may occur within the dura of lesser or greater sphenoid wings. Lesser sphenoid wing fistulas rarely recruit cortical venous drainage and mostly drain in the cavernous sinus. On the other hand, greater sphenoid wing dural fistulas, also known as paracavernous fistulas or sphenobasilar and sphenopetrosal sinus fistulas, are much more notorious as they almost always connect with the superficial middle cerebral vein resulting in secondary cortical venous reflux and varix formation. Curative transarterial or transvenous endovascular embolisation of fistulous connection is the primary therapeutic strategy, particularly using onyx via the transarterial approach. In the present case we describe a 62-year-old man who presented with significant subarachnoid haemorrhage, intraparenchymal and intra-ventricular bleed. Digital subtraction angiography showed a middle cranial fossa dural arteriovenous fistula in the region of the sphenobasilar sinus with cortical venous reflux and varix formation. The patient underwent successful transarterial endovascular embolisation with complete elimination of the fistula using onyx 34, onyx 18, squid 12 and a Scepter XC balloon using the pressure cooker technique. We also report the development of facial nerve palsy due to inadvertent reflux of onyx in the petrosal branch of the middle meningeal artery.

Introduction

Dural arteriovenous fistulas (DAVFs) of the middle cranial fossa commonly involve connections between meningeal branches of the external carotid artery (ECA) and internal carotid artery (ICA) with cavernous sinus followed by spenoparietal sinus. Fistulous connections with paracavernous sinuses; that is, spenobasilar and sphenopetrosal sinus, are complex and very rare. They have a different clinical and imaging presentation with a different treatment strategy when compared to commoner DAVFs of the middle cranial fossa. Here we report a case of sphenobasilar DAVF with cortical venous reflux. We review the relevant literature regarding the anatomical aspects, clinical signs and symptoms and treatment strategy.

Case report

A 62-year-old man presented to emergency with sudden severe headache and left hemiparesis. He had no previous history of head trauma, headache or other neurological symptoms. Head computed tomography (CT) showed subarachnoid haemorrhage (SAH) mainly in the left parietal region, intra-parenchymal haemorrhage in the left parietal lobe with intra-ventricular extension into the bilateral lateral ventricles (Figure 1).

Figure 1.

Non-contrast computed tomography showing extensive subarachnoid haemorrhage, intra-parenchymal and intraventricular bleed over the left side.

Cerebral angiogram revealed a DAVF in the middle cranial fossa region with arterial feeders mainly from branches of the middle meningeal artery (MMA). A few feeders were also seen arising from the accessory MMA. Venous drainage was seen through the superficial middle cerebral vein (SMCV) into cortical veins, which formed multiple huge and tortuous varices and finally connected into the superior sagittal sinus (Figure 2(a) and (b)).

Figure 2.

(a) Left external carotid artery (ECA) lateral angiogram showing sphenobasal fistula with venous reflux in the superficial middle cerebral vein (SCMV). Also seen are multiple varix formation in the cortical veins. (b) Left ECA antero-posterior angiogram showing sphenobasal fistula with venous reflux in the SCMV.

After discussion, endovascular embolisation was undertaken under general anaesthesia by the transarterial route via the transfemoral approach. A detachable tip microcatheter, Sonic 1.2F (Balt Extrusion, Montmorency, France) was advanced into the MMA to reach the fistula with its distal tip in the foot plate of the vein. Another microcatheter, Headway duo 156 cm (MicroVention, CA, USA) was advanced in the MMA at the fistulous site in order to perform the pressure cooker technique. Onyx 34 and 18 (eV3, Irvine, CA, USA) and Squid 12 (Balt Extrusion, Montmorency, France) were used as liquid embolic agents. An onyx 34 plug was created from the second microcatheter and subsequent injection of squid 12 and onyx 18 was performed from the distal detachable tip microcatheter. Adequate penetration of embolising agent was noted in the fistula and foot of the draining vein. An angiogram showed significant slowing across the fistula; however, the fistula and retrograde cortical venous drainage remained. ECA angiogram revealed the opening of new feeders from the superficial temporal artery (STA) and accessory MMA. Subsequently, the STA branch supplying the fistula was hooked selectively and onyx embolisation was performed. Significant reflux of onyx was noted up to the skull base with little anterograde penetration of embolic agent across the fistula. An angiogram showed persistent slow flow across the fistula with arterial feeder from accessory MMA and reflux in the SMCV. Next, the accessory MMA feeder was selectively catheterised using a Marathon microcatheter (eV3, Irvine, USA). To prevent reflux of embolic agent across the dangerous anastomoses via the accessory MMA to the ophthalmic artery and petrocavernous ICA a Scepter XC balloon catheter was placed across the arterial feeder and embolisation was performed using onyx 18. Complete elimination of the fistula was achieved this time (Figure 3(a) and (b)).

Figure 3.

(a) Post-embolisation left external carotid artery (ECA) lateral angiogram showing complete elimination of the fistula. (b) Post-embolisation left ECA antero-posterior angiogram showing complete elimination of the fistula.

Post-procedure CT showed no fresh bleeding with embolising agent seen laterally along the greater sphenoid wing in the middle cranial fossa (Figure 4). Reflux of embolising agent was seen up to the level of the foramen spinosum (Figure 5). The patient tolerated the procedure very well and was extubated next day. As expected, he developed mild facial nerve palsy. His consciousness and left-sided weakness improved gradually and he was discharged on post-procedure day 10. At 3 months’ follow-up he had made a significant recovery with improvement in power over the left side.

Figure 4.

Post-embolisation non-contrast computed tomography showing onyx deposition along the greater sphenoid wing.

Figure 5.

Onyx cast with reflux at skull base.

Discussion

DAVFs in the sphenoid region are extremely rare and are commonly confused with other common middle cranial fossa DAVFs, particularly cavernous sinus DAVFs. These fistulas are located along the greater and lesser sphenoid wings and are different from cavernous sinus dural fistulas in the parasellar region. Arterial feeders are received from multiple dural branches from the ICA and ECA in this region, predominantly MMA, accessory MMA, artery of foramen rotundum, recurrent meningeal branches from the ophthalmic artery, inferolateral and meningohypophyseal trunk of the cavernous ICA. Venous drainage of sphenoial veins is commonly seen in sphenoparietal sinus and cavernous sinus and less commonly in paracavernous sinuses (sphenobasilar and sphenopetrosal sinus). Anatomically, the sphenoparietal sinus is located along the lesser sphenoid wing and it drains into the cavernous sinus. On the other hand, the spenobasilar and sphenopetrosal sinus are located at the skull base in the middle cranial fossa along the greater sphenoid wing, laterally and medially, respectively.¹ San Millán Ruíz et al., in their study on non-fixed human specimens found that a SMCV drains into the paracavernous sinus, laterocavernous sinus or cavernous sinus but never connects to the sphenoparietal sinus.²

Therefore, patients with sphenoparietal sinus DAVF commonly present with ophthalmic bruit, headache, exopthalmos and symptoms similar to cavernous sinus fistula. On the other hand, a fistula of the paracavernous sinus (sphenobasilar and sphenopetrosal sinus) presents with cortical venous reflux and secondary subarachnoid and intra-parenchymal haemorrhages secondary to intra-cranial venous hypertension. Shi et al., in their series of six sphenobasal sinus (greater wing) DAVFs, described how they are more likely drained into the SMCV (66%), with cortical venous drainage in 50% and variceal formation in 100% of these sphenobasal lesions.³

Long-standing venous hypertension resulting from retrograde sinus or cortical vein flow either leads to the formation of varix leading to intracranial haemorrhage, as has been described by Zhou et al.,⁴ or less commonly may lead to venous infarct as a result of congestion impairing normal parenchymal venous drainage leading to ischaemia, as reported by Lv et al.⁵ Retrograde flow into the galenic system has also been reported by Osbun et al.⁶ This calls for an aggressive and definite treatment strategy without delay. The aim of treatment should be complete occlusion of the fistula; that is, the occlusion of proximal parts of the draining veins.

We perform transarterial onyx embolisation as our primary technique. Transvenous embolisation must be considered when access to the fistulous site via the venous route is amenable. It is the safest and most effective approach if the fistulous site can be approached via a patent venous pathway, most commonly an inferior petrosal sinus and less commonly a facial vein or deep venous system (galenic pathway).⁷ One must be cautious of the incomplete occlusion of the fistula or cavernous sinus as this may lead to flow diversion towards cortical or deep veins.⁸ In this particular case transvenous embolisation was difficult due to no accessible route via the venous pathway to reach the fistulous point. As the fistulous point was close to the foramen spinosum, therefore, we performed the pressure cooker technique in the MMA branch to prevent reflux of onyx in order to avoid facial nerve palsy. For the pressure cooker technique a plug can be created by either a coil mass with glue or onyx 34. In the present case we used onyx 34 for plug formation. This proximal plug prevents retrograde reflux of embolising agent and aids in its forward flow towards the target fistulous point and is called the ‘plug and push technique’.⁹ Significant slowing of the fistula was seen; however, this technique is sometimes unpredictable and some reflux up to the level of the foramen spinosum resulted in the present case.

When onyx embolising MMA branches care should be taken to avoid reflux in the cavernous and petrosal branches as it may result in trigeminal or facial nerve palsy, respectively. Therefore, care should be taken to avoid reflux of onyx to the foramen spinosum.

Complete occlusion of the fistula was achieved when the remainder component of the fistula was approached by a different arterial feeder from the accessory meningeal artery and this time the pressure cooker technique was performed by a Scepter XC balloon catheter (MicroVention, CA, USA). The 0.0165-inch inner lumen of the Scepter XC allows tracking over a 0.014-inch guide wire, which is easier to steer compared to a 0.010-inch guide wire, providing more support for distal navigation of the balloon over tortuous vessels. The balloon portion of the Scepter XC microcatheter acts as the proximal plug. Onyx can be injected by balloon catheter itself or by a jailed microcatheter, as was done in this case. A disadvantage of using this technique is navigation of the large double lumen balloon microcatheter into small distal vessels only accessible to flow-guided microcatheters.¹⁰ Superior division of the accessory MMA enters the cavernous sinus through the foramen ovale to anastomose with the infero-lateral trunk of the cavernous ICA.¹¹ To prevent reflux of liquid embolic agent through these dangerous anastomoses, a balloon catheter was kept across the feeding branch in the main trunk of the accessory MMA in this case.

Thus, we conclude that paracavernous fistulas are an extremely rare entity and have a high propensity to present with intracranial bleed secondary to long-standing venous hypertension. Curative transarterial or transvenous embolisation is the primary therapeutic strategy for these lesions. The pressure cooker technique is the way towards achieving complete cure of the fistula. Care should be taken while embolising MMA branches to avoid reflux to the foramen spinosum. In incompletely embolised patients, the exclusion of any cortical venous reflux is paramount.