Indirect Flow Diversion for Off-Centred Bifurcation Aneurysms and Distant Small-Vessel Aneurysms: A Retrospective Proof of Concept Study From Five Neurovascular Centres - European Medical Journal

Indirect Flow Diversion for Off-Centred Bifurcation Aneurysms and Distant Small-Vessel Aneurysms: A Retrospective Proof of Concept Study From Five Neurovascular Centres

1 Mins
Stefan Schob, *Marie-Sophie Schüngel, Richard Brill, Martin Skalej
*Correspondence to [email protected]

Schob has received consulting fees from Acandis, Balt, Cerenovus, and Phenox. Schüngel has received consulting fees from Balt. Brill and Skalej have declared no conflicts of interest.

EMJ Radiol. ;4[1]:34-35. DOI/10.33590/emjradiol/10305753.
Bifurcation aneurysm, indirect flow diversion, indirect flow-diverting, slipstream effect.

Each article is made available under the terms of the Creative Commons Attribution-Non Commercial 4.0 License.


Treatment of cerebral aneurysms using haemodynamic implants such as endosaccular flow disruptors and endoluminal flow diverters has gained significant momentum during recent years. The intended target zone of these devices is the immediate interface between the aneurysm and the parent vessel. The therapeutic success is based on the reduction of aneurysmal perfusion and the subsequent formation of a neointima along the surface of the implant. However, a subset of aneurysms (off-centred bifurcation aneurysms involving the origin of efferent branches and aneurysms arising from peripheral segments of small cerebral vessels) often cannot be treated via coiling or implanting a haemodynamic device at the neck level for technical reasons. In these cases, indirect flow diversion (FD), a flow diverter deployed in the main artery proximal to the parent vessel of the aneurysm, can be a viable treatment strategy, but clinical evidence is lacking in this regard.


Five neurovascular centres contributed to this retrospective analysis of patients who were treated with indirect FD. Clinical data, aneurysm characteristics, anti-platelet medication, and follow-up results, including procedural and post-procedural complications, were recorded.


Seventeen patients (mean age: 60.5 years; range: 35–77 years) with 17 target aneurysms (vertebrobasilar: n=9) were treated with indirect FD. The average distance between the flow-diverting stent and the aneurysm was 1.65 mm (range: 0.4–2.4 mm). In 15 out of 17 patients (88.2%), perfusion of the aneurysm was reduced immediately after implantation. Follow-ups were available for 12 cases. Delayed opacification (OKM A3: 11.8%), reduction in size (OKM B1–3: 29.4%), and occlusion (D1: 47.1%) were observable at the latest investigation. Clinically relevant procedural complications, and adverse events in the early phase and in the late subacute phase, were not observed in any case.

The indications for flow-diverting techniques are rapidly expanding; however, evidence for the endovascular treatment of bifurcation aneurysms or very small branches impeding direct probation is yet scarce, and still under debate. There is great controversy, as indirect FD demands jailing of major vessel branches, consequently affecting the haemodynamic situation; it may also alter the perfusion of the downstream territory. Therefore, it is essential to evaluate the individual collateral supply prior to the treatment, in order to decrease the risk of ischaemic events that may occur as a result of competitive flow. The study results, however, predict the indirect affection of the aneurysm perfusion as sufficient bail-out option without an increased risk of ischaemic events, and still afford adequate occlusion rates. The effect might be attributed to progressive deconstruction of the aneurysm and its parent vessel.1 Furthermore, no increased incidence of vessel degradation as a result of FD coverage was observed.


The authors’ preliminary data suggest that indirect FD is a safe, feasible, and effective approach for off-centred bifurcation aneurysms and distant small-vessel aneurysms. However, validation with larger studies, including long-term outcomes and optimised imaging, is warranted.

Wajnberg E et al. Progressive deconstruction: a novel aneurysm treatment using the pipeline embolization device for competitive flow diversion: case report. Neurosurgery. 2014;10(Suppl 1):E161-6.

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