Percutaneous Embolization of Carotid Paragangliomas Using Solely Onyx

Discussion

Paragangliomas are highly vascularized tumors, which might lead to a considerable blood loss during surgical extirpation. The potential invasiveness of an embolization must be justified by providing a clear advantage during surgery. Tumor devascularization reduces intraoperative blood loss, thus resulting in better defining the planes of dissection and simplifying total tumor resection.

Several techniques concerning glomus tumor embolization via the endovascular route (arterial, venous, or combined) or through direct percutaneous puncture have been previously described in the literature. Endovascular embolization was shown to facilitate surgical tumor removal and diminish the need for red blood cell transfusions.^1–3 Injection of Onyx through a combined arterial and venous route has also been reported to offer complete embolization of a paraganglioma.⁴

A percutaneous approach by using liquid embolic material such as cyanoacrylate glue, which has been previously described, was shown to be safe and effective and might have the advantage of obliterating the tumor bed in contrast to the endovascular tumor approach.^5–7 Nevertheless, there are potential risks of acute displacement of glue into brain-supplying arteries during injection,⁸ and even delayed migration has been described.⁹ Extreme caution must be used due to “dangerous” collaterals and retrograde filling of small vessels arising from the ICA and vertebral artery.

We report 4 patients treated for 6 carotid paragangliomas supplied by tumor vessels arising from the ECA and ICA. The tumors were embolized by direct puncture of the tumor, and complete obliteration could be achieved by using Onyx as the sole embolic agent. Although percutaneous tumor embolization with Onyx has already been described in the literature,¹⁰ it was used in combination with other embolic material such as particles administered by the endovascular route. In this case, tumor obliteration was not complete. Recently Elhammady et al¹¹ reported a single case of direct percutaneous embolization of a carotid body tumor with Onyx and confirmed the ease of access to the tumor vascularity by direct percutaneous tumor puncture, resulting in complete obliteration. A typical finding in carotid paragangliomas is the supply from extremely small vessels originating from the proximal part of the ICA and ECA, as in the case illustrated above (Fig 1A).

These tiny vessels cannot be selectively catheterized by endovascular techniques. With a percutaneous approach, complete obliteration even of those small vessels can be achieved. However, because direct intratumoral injection of liquid polymerizing agents may result in retrograde filling of those vascular channels, it bears the risk of migration of embolic material into intracranial arteries. Therefore, precautions to avoid such circumstances should be undertaken, even using a controllable slow-migrating embolic agent like Onyx. In our case, a nondetachable microballoon was inserted and temporarily inflated in the proximal ICA at the origin of the tiny tumor branches. The use of Onyx as a liquid embolic agent proved to be safe because the injection rate is very slow; because Onyx behaves like lava flow, the velocity of Onyx spread is much more controllable than that using conventional acrylates, especially if arteriovenous shunt surgery is present in the tumor.

Onyx is known and widely accepted for embolization of intracranial arteriovenous malformations. The flow characteristics of Onyx in contrast to conventional liquid embolic materials like n-BCA are optimal for tumor embolization by direct puncture, demonstrated in our series of 6 paragangliomas. Determining angioarchitecture by analyzing all feeding vessels plays a minor role when using Onyx. This embolic agent has the advantage of distributing slowly in an ante- and retrograde way to the entire tumor bed, even if it is supplied by different arteries. The fact that in most of our patients 1 needle position was sufficient underlines this fact. Regarding the degree of devascularization, direct puncture of the tumor with percutaneous embolization is considered superior to the endovascular approach. Tumor removal was considered easy due to devascularization and the elastic consistency of Onyx.

Further documentation is necessary to prove the higher grade of devascularization of paragangliomas with Onyx compared with conventional glue or other embolic material and the associated potential to facilitate surgery. Nevertheless, Onyx seems to be safe when used percutaneously due to its lavalike pattern flow and its controllable properties, allowing slow tumor-bed penetration. Onyx might be also an optimal embolic liquid to preoperatively treat paragangliomas percutaneously at more challenging locations at the skull base.