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.
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.