The Source for Neurovascular News and Education

October 27, 2021


Key Points:

- Study looks at effects of flow diverters for carotid siphon aneurysms

- Flow diverters may affect posterior communicating artery flow without any symptoms


Use of flow diverters for carotid siphon aneurysms can affect the flow through the posterior communicating artery if the stent covers the artery ostium, particularly when P1/posterior communicating artery flow ratio size is large. There do not appear to be any clinical sequelae to this flow change, however, according to a study published online July 7, 2016, ahead of print in the Journal of NeuroInterventional Surgery.

“A recurrent concern about the use of [flow-diverter stents] relates to their occlusion of side branches,” write the authors, led by Fernando M. de Carvalho, MD, of Bicêtre Hospital (Bicêtre, France). “When placed within the internal carotid artery, the main problem is the coverage of the ophthalmic artery, the posterior communicating artery, and the anterior choroidal artery.”

While carotid siphon branch occlusion has been studied, they report, researchers have typically focused on the Pipeline embolization device (Covidien) and limited their investigations to occlusions of the ophthalmic and anterior choroidal arteries.

de Carvalho and colleagues retrospectively assessed the impact of flow-diverter stents—including Pipeline, Silk (Balt, Montmorency, France), Surpass (Stryker Neurovascular, Fremont, CA), and FRED (MicroVention, Tustin, CA)—on the flow of the posterior communicating artery among patients treated for carotid siphon aneurysms between February 2011 and January 2015.

During this time period, 125 cases were treated. Among these, angiographic follow-up revealed that 18 aneurysms in 17 patients were treated with flow-diverter stents that covered the ostium of the posterior communicating artery. Ten of these cases had a P1/ posterior communicating artery size ratio > 1, and 8 had a size ratio ≤ 1.

After a mean follow-up of 10 months, angiography showed changes in posterior communicating artery flow in 90% of the patients with the larger P1/posterior communicating artery size ratio but in only 12.4% of those with the smaller ratio (P = .002).

No Clinical Impact

Importantly, no symptoms related to flow changes were observed.

Giuseppe Lanzino, MD, of the Mayo Clinic (Rochester, MN), told Neurovascular Exchange in an email that the use of flow diverters for this indication is quite common nowadays because “there is no need to go into the aneurysm itself, [and the procedure] potentially treats the diseased segment of the vessel instead of the aneurysm alone. . . . The treatment is approved for proximal internal carotid artery aneurysms which have a ‘side-wall; morphology.”

On the other hand, patients must remain on dual antiplatelet therapy postprocedure, he said, adding that sometimes the only way to perform it is to cover up other important vessels. This study “confirms what we have all observed: that it is safe to cover vessels with a flow diverter, and these vessels may undergo angiographic obliteration often without clinical symptomatology,” Dr. Lanzino said. “This happens because the vessel goes on to occlusion if there is enough collateral circulation.”

Repaving the Road

Flow diverters are such a new area, Ryan McTaggart, MD, of Brown University (Providence, RI), told Neurovascular Exchange in a telephone interview, that studies like this one offer valuable insight.

In the United States, flow-diverter use is limited by the specific indications currently approved by the Food and Drug Administration. Dr. McTaggart said. But in fact, he reported, up to 50% of aneurysms are potentially eligible for treatment with flow diverters. Unlike clipping and coiling, he said, the treatment is “not just fixing the pothole but repaving the whole road.”

Dr. McTaggart was particularly interested in the data in this study demonstrating the importance of the P1/posterior communicating artery size ratio. It would be interesting, he said, to uncover the significance of ratio size among a larger population of patients whose aneuryms arise specifically from the posterior communicating artery segment.

Currently, Dr. Lanzino pointed out, the decision to use flow diverters over clipping and coiling is based not on clinical factors or evidence but on personal preference, which is not ideal. Determining which is the best option remains a “moving target,” said Dr. McTaggart, because proceduralists are contining to gain experience with flow diverters, and the devices themselves continue to evolve, becoming safer and easier to use. “We must proceed with caution and be judicious in whom we select and how fast we move,” he said.



de Carvalho FM, Caroff J, Pereira Dos Santos Neto E, et al. Flow changes in the posterior communicating artery related to flow-diverter stents in carotid siphon aneurysms. J NeuroInterv Surg. 2016;Epub ahead of print.


- Drs. de Carvalho and McTaggart report no relevant conflicts of interest

- Dr. Lanzino reports being a consultant for Covidien and Medtronic