The Donut Sign: A New Angiographic Sign for Partially Thrombosed Aneurysms with Flow-Induced Intraluminal Thrombus

Abstract

<jats:p> Three patients are described with unruptured large partially thrombosed aneurysms with a peculiar donut-shaped remaining lumen. </jats:p><jats:p> Observations suggest that the flow geometry of the aneurysm and parent vessels induces a preferential circular laminar flow inside the aneurysm followed by partial intraluminal thrombosis leaving a donut-shaped lumen to accommodate the circular flow. This flow mechanism of thrombus formation inside aneurysms is different from the more common repeated intramural dissections and hemorrhages that cause growth in most large and giant partially thrombosed aneurysms. </jats:p>

Internal carotid artery “donut” aneurysm treated using DERIVO flow-diverting stent

“…Phenomenon of "donut sign" or "donut aneurysm" was first described in 2014 by Van Rooij [2]. This radiological sign occurs in aneurysms in which there is partial thrombosis inside aneurismal sac and circular laminar flow between the aneurismal wall and the thrombus in its center.…”

“…Several methods have been used in treatment of this type of aneurysm: microvascular dissection and clipping, or endovascular treatment (stent assisted coiling, combined treatment with Woven Endo Bridge (WEB) and coils and FD stent in two cases) [2][3][4]6]. Microsurgical direct clipping giant aneurysms needs adequate craniotomy and visualization of the parent artery and its branches with minimal parenchymal retraction and minimal manipulation of the adjacent neurovascular structures.…”

“…Based on up-to-date experience, endovascular treatment has proven to be the method of choice. In cases with large aneurysms with mass effect and partial thrombosis, recanalisation after coiling is expected in high percentage of cases [2,11]. Flow diverting stents have proven to be an effective alternative to coiling, but they had several important disadventages, such as lack of immediate effect, need for antiplatelet therapy and relatively long latency for aneurysm exclusion to take place [12,13].…”

‘Donut’ basilar aneurysm with brainstem compression: Treatment using a flow diverting stent

“…The ‘donut sign’ is an angiographic sign seen when aneurysm geometry and flow conditions result in circular laminar flow. 1 Slow flow in the centre of the aneurysm results in partial thrombosis. This results in a central filling defect and is responsible for the donut shaped appearance seen at angiography.…”

“…3 Limited published experience with donut aneurysms suggests they are also prone to recurrence. 1 Flow diversion has been shown to be an effective alternative to coil embolisation of intracranial aneurysms. Disruption of flow within the aneurysm results in progressive thrombosis and exclusion from the intracranial circulation.…”