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I'm doing research of flow diverter for cerebral aneurysms applications and I'm wondering the reason behind stent placement underneath of cerebral aneurysms is to divert the flow or stabilize the hemodynamics (e.g. reduce wall shear stress or blood flow velocity in the aneurysmal region)? Let's say people do it to divert the flow and prevent blood to enter the aneurysmal region. That looks fine for side wall aneurysms when there is no smaller arterioles or branches connected to the aneurysm, but for terminal aneurysm where the flow diverter may block the blood flow into smaller arterioles, is it a appropriate case to deploy stent? I mean if we prevent the blood to enter some part of smaller arterioles how brain could maintain its functionality due to its need for oxygen. I appreciate if someone could explain the logic behind the flow diverter placement in the cerebral aneurysms.

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I don't quite understand the dichotomy you present between diverting flow and stabilizing hemodynamics. The former is a direct outcome and the latter is a secondary outcome: both are goals.

The overall goal is to isolate the blood in the aneurysm and allow it to clot and heal over time. Embolic coils are also used to assist the process, in which case the flow diverter helps to keep the coil in place and the resulting embolism out of the primary circulation.

One would not typically deploy a flow diverter over branches that one wishes to remain patent, although patency can be maintained in smaller vessels. In many neurovascular situations, collateral circulation can make it acceptable to occlude a branch, however.

You may be confusing plain stents with flow diverters; a plain stent has as few struts as possible while maintaining structural support (though high flow through the struts can cause turbulence and is something you want to avoid if possible), and creative stent placement techniques including deployment of multiple stents and use of balloons to break open strut configurations can be used. These do not block flow per se, but can help keep coils in place and maintain the desired structure of the vessels involved.

I've included several references that I quickly gathered; these may not be the most ideal references but should give you a look at some of the approaches used. I would strongly suggest you look through the rest of the literature using search terms from your question to get an idea of how interventionalists approach different situations.

I'll add that I am not a physician and am not up-to-date with the latest guidelines or standard of care, but in my experience with the literature a lot of these decisions are up to the experience of the physicians involved and based on a lot of case study; randomized trials aren't really possible to cover all the anatomical variety that is experienced.


Burkhardt, J. K., Riina, H. A., Tanweer, O., Shirani, P., Raz, E., Shapiro, M., & Nelson, P. K. (2018). Flow diversion and microvascular plug occlusion for the treatment of a complex unruptured basilar/superior cerebellar artery aneurysm: case report. Journal of neurosurgery, 1-6.

Chow, M. M., Woo, H. H., Masaryk, T. J., & Rasmussen, P. A. (2004). A novel endovascular treatment of a wide-necked basilar apex aneurysm by using a Y-configuration, double-stent technique. American Journal of Neuroradiology, 25(3), 509-512.

Miyachi, S., Matsubara, N., Izumi, T., Asai, T., Yamanouchi, T., Ota, K., ... & Wakabayashi, T. (2013). Stent/balloon combination assist technique for wide-necked basilar terminal aneurysms. Interventional Neuroradiology, 19(3), 299-305.

Puffer, R. C., Kallmes, D. F., Cloft, H. J., & Lanzino, G. (2012). Patency of the ophthalmic artery after flow diversion treatment of paraclinoid aneurysms. Journal of neurosurgery, 116(4), 892-896.

Siddiqui, M. A., Bhattacharya, J. J., Lindsay, K. W., & Jenkins, S. (2009). Horizontal stent-assisted coil embolisation of wide-necked intracranial aneurysms with the Enterprise stent—a case series with early angiographic follow-up. Neuroradiology, 51(6), 411-418.

Wong, G. K., Kwan, M. C., Ng, R. Y., Simon, C. H., & Poon, W. S. (2011). Flow diverters for treatment of intracranial aneurysms: current status and ongoing clinical trials. Journal of Clinical Neuroscience, 18(6), 737-740.

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  • $\begingroup$ The flow diverter and plain stents are used interchangeably by authors, whom do not have any medical experience and are engineers like me, in the literature. At least is there any way to find out in which case we need to put plain stent or flow diverter?! Also, is it possible to explain a little bit more about plain stents and its application and what does it do to change hemodynamics? I appreciate your help. $\endgroup$ – Mehrdad Yousefi Sep 11 '18 at 21:50
  • $\begingroup$ A plain stent has no covering on it, it's just metal mesh. It provides structural support and keeps an embolic coil inside the aneurysm. If you are engineers and have no medical experience, you should really find an interventional radiologist/neurosurgeon/whoever does intracranial embolism at your institution to discuss with. I'm neither an engineer nor a physician but I did have a job bridging exactly that gap for engineers in the area of intravascular devices; the engineers often didn't even know what they didn't know when they came to us and talked a lot about how much they benefited. $\endgroup$ – Bryan Krause Sep 11 '18 at 21:54
  • $\begingroup$ Ok you made the question more interesting to me! What is that cover you are talking about in the flow diverters? it's a coating? If yes, do you know what's the material of that coating and its purpose perhaps? I mean I really apologize to ask a lot of question from you. But I believe you are the only person here which knows these kind of things. I really appreciate your help! $\endgroup$ – Mehrdad Yousefi Sep 11 '18 at 21:56
  • $\begingroup$ Yes this is a small community, I doubt you will find another person here who did R&D with stents. I think I am partly mistaken about the flow diverters, as I was thinking these are covered stents but it seems they are just high-metal density stents. They just have more struts for a given area and are meant to occlude to some extent, whereas normal stents are meant to avoid occulsion as much as possible (i.e., to provide as much support as possible with minimal contact to tissue). I'll make sure to update my answer. $\endgroup$ – Bryan Krause Sep 11 '18 at 22:05
  • $\begingroup$ One interesting question about occlusion is that: a lot of researches in the literature claim that low wall shear stress is responsible for cerebral aneurysms' rupture but when we put flow diverter (FD) it will reduce the wall shear stress in the aneurysmal region because it prevents the blood to enter the aneurysm. So, does it increase the rupture risk or decrease it? I mean in the literature people are saying FDs reduce the wall shear stress and that will help to occlude the aneurysm but if the low wall shear stress is responsible for rupture, it looks counter intuitive to me. $\endgroup$ – Mehrdad Yousefi Sep 11 '18 at 22:10

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