Use of Onyx for Transarterial Balloon-Assisted Embolization of Traumatic Carotid Cavernous Fistulas: A Report of 23 Cases

Discussion

Endovascular treatment for TCCFs aims at total occlusion of the fistulous communications to decrease the pressure in the CS and improve cerebral perfusion. However, controversy still exists regarding the optimal treatment strategy for these lesions. Transarterial embolization with detachable balloons used to be the standard treatment of TCCFs.^6,7 The reported cure rate with balloon embolization of direct CCFs is 88%–99%,^8⇓–10 and the ICA preservation is 88%–98%.^8,11 However, technical problems of detachable balloons, such as early detachment, deflation, and rupture of the balloon caused by bone fragments, may result in some severe complications or recurrence of the fistula.¹⁰ Among the 23 patients in our series, 3 had been treated by detachable balloon embolization before admission to our hospital, with total occlusion in 2 patients and partial occlusion in 1 patient. However, postprocedural symptoms, including pulsating tinnitus, proptosis, and chemosis, recurred in 1–3 months. Angiographic follow-ups in all these cases demonstrated deflation of the balloon and recurrence of the fistula. The FDA approved the first detachable balloons, Silicone Mini Balloon (Becton-Dickinson, Rutherford, New Jersey), for peripheral vessel occlusion in 1982, and in 1990 the manufacturer withdrew this device for financial reasons.¹² Detachable balloons (DSB; Boston Scientific-Target, Fremont, California) for intracranial use were approved by the FDA in 1991. Because of balloon valve leaks, these were withdrawn from use in United States¹³; however, the balloon remains in clinical use for the treatment of TCCFs in many other countries, especially in China. Coils, especially hydrogel-coated coils, for the embolization of TCCFs were reported to be safe, effective, and controllable and a stable method of maintaining high carotid artery patency.¹⁴ However, the cost of this therapy is so high that many patients cannot afford it, especially in developing countries like China. Moreover, it is difficult to identify herniation of coil loops in the ICA when the fistula ostium is too large. To some extent, stent-assisted coil embolization for TCCFs may solve this technical problem,¹⁵ but anticoagulant and antiplatelet therapy after stent placement may decrease the complete occlusion rate of the fistula. In recent years, the covered stent also became available for patients with TCCFs whose fistulas cannot be successfully occluded with detachable balloons or detachable coils.^16⇓–18 Its main drawback for intracranial use is the limited longitudinal flexibility, and more investigation is required to further develop its specifications and indications.¹⁷

Onyx is a liquid mixture of ethylene-vinyl alcohol copolymer and suspended tantalum powder for radiopacity in a DMSO solvent. Mixed in varying proportions, the manufacturer can produce Onyx in different concentrations for different vascular disorders. This nonadhesive embolic polymer precipitates and solidifies in the vessel as DMSO diffuses away in blood. The nonadhesive nature of Onyx permits a long and controlled infusion. The direction of the Onyx casting in the vessel changes as the injection speed slows down. Therefore, Onyx can be cast in the sinus or vessels adequately. Onyx embolizations become the preferred treatment for brain AVMs and DAVFs, and its safety and efficacy have been fully evaluated.^19⇓–22

TCCFs are different from spontaneous cavernous sinus DAVFs. The latter are often complicated and with a bilateral arterial or both internal and external carotid artery supply. The feeding artery is often so tiny that the transarterial approach still remains a technical challenge. The former are the direct communications between ICA and CS, where embolization via a transarterial approach is very convenient because the microcatheter may be easily navigated to the CS through the fistula with a guidewire. Although the use of Onyx is well-controlled with long injection features, it has a potential risk of occluding ICA-external carotid artery anastomoses.²³ However, injection resistance in the CS is low and especially for TCCFs, the fistula is directed to the CS. Accordingly, the risk of misembolization of pre-existing collateral vessels is also relatively lower than that in cavernous sinus DAVFs. Therefore, the avoidance of Onyx reflux to the ICA from the CS through the fistula ostium is the key to avoiding severe embolic complications. In our series, we used a nondetachable balloon within the ICA to cover the fistula ostium before Onyx injection and confirmed total coverage with angiography of CS injection through the microcatheter and/or ICA injection through the guiding catheter.

Despite the protection of nondetachable balloons, there is no denying that a tiny quantity of Onyx may spill over the ostium and cast between the artery and the nondetachable balloon at the end of the Onyx injection, but the quantity of the excess Onyx is too tiny to be observed. What bothered us was that the flaking of the Onyx might cause new infarctions. We are delighted that no ischemic complications occurred, and all the treated ICAs were well preserved among these 23 patients.

However, TCCFs usually follow a traumatic tear of the cavernous segment of the ICA by skull fracture fragments, so the location and the size of the fistula ostium are very difficult to ascertain due to the high flow rates, especially in the case of total arterial steal. Furthermore, the superselective navigation of a nondetachable balloon to the distal ICA may be difficult due to a large fistula because of high rates of blood flow of the fistula. Under such circumstances, pre-embolization with a detachable balloon could be performed first. The detachable balloon in the CS decreases the blood flow rates of the fistula and facilitates the navigation of the protective balloon, and at the same time, pre-embolization with a detachable balloon may reduce the volume of Onyx and the injection time. In addition, the Onyx casting around the detachable balloon also protects the balloon from rupture by bone fragments. In 1 case, as depicted in Fig 1, the patient underwent detachable balloon embolization before being admitted to our department, and angiograms demonstrated deflation of the balloons and a total arterial steal. In the treatment procedure, it was very difficult to navigate the guidewire of the nondetachable balloon across the fistula site superselectively to the distal part of the ICA. Therefore, we performed an unplanned pre-embolization with a detachable balloon first to decrease the blood rate of the fistula ostium. Afterward, we successfully positioned the protective nondetachable balloon within the ICA and occluded the fistula completely with 3.6 mL of Onyx-34. The 3-month digital subtraction angiography confirmed the complete occlusion of the TCCFs.

• Download figure
• Open in new tab
• Download powerpoint

Fig 1.

A, The fistula ostium is definitely identified by the pressing test of the left ICA. B, Pre-embolization with a detachable balloon first. C, Onyx-34 is injected under the protection of a nondetachable balloon within the ICA. D, The Onyx cast postembolization. E, Immediate angiogram reveals complete occlusion. F, The 3-month digital subtraction angiography confirms complete occlusion of the TCCF.

Delayed cranial nerve palsy has been reported with the use of coils²⁴ and nBCA.²⁵ We were concerned about the same complication with the use of Onyx, especially that the solvent DMSO might have neurotoxicity²⁶ on cranial nerves in the CS. Nevertheless, after an up-to 24-month follow-up, there was no demonstrated aforementioned complication among these 23 patients. The reasons might be as follows: First, for a direct CCF, we just needed to occlude the ostium of the fistula; therefore, there should be more Onyx around the ostium instead of in the CS and less compression to the nerves in the CS. Second, we did find delayed cranial nerve palsies with the use of Onyx for the treatment of cavernous sinus DAVFs due to devascularization of the vasa nervorum. The risk of misembolization of pre-existing collateral vessels with the use of Onyx for the treatment of TCCFs is relatively smaller than that in cavernous sinus DAVFs as mentioned above.

The change of cerebral hemodynamics after complete occlusion of the fistula may result in hyperperfusion syndrome. Thus for patients with bilateral fistulas and total arterial steal, a staged procedure may be very important to reduce the risk of hemorrhagic reperfusion, as in the case demonstrated in Fig 2.

• Download figure
• Open in new tab
• Download powerpoint

Fig 2.

A and B, Left ICA (L-ICA) injection demonstrates total arterial steal. The fistula mostly drains from vertex veins into the superior sagittal sinus. C and D, Right ICA injection shows the other fistula. The superior ophthalmic vein as a draining vein could be identified easily. E, The microcatheter navigates into the cavernous sinus superselectively, and the nondetchable balloon is inflated within the L-ICA before starting the Onyx injection. F, The immediate postembolization angiograms confirm complete occlusion with good preservation of the L-ICA and a great change of remote cerebral hemodynamics. G, The Onyx cast after injection. H, Three-month follow-up reveals stable complete occlusion of left TCCF.

There are some limitations to our study. Because of high blood rates of fistulas, even in total arterial steal, the damaged side of the cerebral hemisphere is in a state of relative hypoperfusion. Pre- and postoperative MR imaging should have been performed to identify asymptomatic cerebral infarction related to nondetachable balloons and flaking of solidified Onyx around the ostium, even though there is no significant relationship between balloon inflation practices and ischemic events, as reported by Spiotta et al,²⁷ and no new ischemic events were observed in any of these 23 patients either. Besides, long-term follow-up and larger case series are needed for further evaluation of the safety and efficacy of Onyx for the transarterial balloon-assisted embolization for TOCFs.