- Blood flow diversion has the potential to improve outcomes in the treatment of complex brain aneurysms that are poorly suited to traditional surgical methods
- In the treatment of ruptured aneurysms, two principal concerns are the risk of hemorrhage because of potential delayed aneurysm occlusion and the hemorrhagic complications from antiplatelet use
- There has been preliminary success in using flow diversion to treat blister aneurysms and subarachnoid aneurysms
- Refinements in devices, techniques and management of thromboembolism prophylaxis are ongoing
There are two principal concerns when treating ruptured aneurysms: the risk of hemorrhage because of potential delayed aneurysm occlusion and the hemorrhagic complications from antiplatelet use. Over the past few years, blood flow diversion has become a primary treatment option for complex unruptured brain aneurysms that are difficult to treat with surgical clipping, endovascular coiling or other traditional methods. In certain cases, flow diversion is now being used as a primary treatment for ruptured aneurysms as well. Flow diversion involves placing a stent such that blood flow stagnates inside the aneurysm dome and undergoes thrombosis. As a new endothelium develops, it reconstructs the parent vessel and cures the aneurysm.
Aman Patel, MD, director of Cerebrovascular and Endovascular Neurosurgery at Massachusetts General Hospital, and colleagues, including Mass General neurosurgery residents Matthew J. Koch, MD, and Christopher J. Stapleton, MD, recently reviewed these indications in Neurocritical Care. They found that there has been preliminary success in using flow diversion to treat two subtypes of ruptured aneurysms—blister aneurysms (also called dissecting aneurysms or pseudoaneurysms) and subarachnoid aneurysm.
The reviewers summarized a meta-analysis that identified 62 patients with blister aneurysms who had flow-diverting stents placed. The pooled data showed a 90.8% rate of mid- to long-term complete occlusion and a low need for retreatment at 6.6%. Dr. Patel’s group cautions, however, that instances of stroke, aneurysm persistence and death have been reported.
Flow-diverting stents have also been used to treat subarachnoid aneurysm, but there is concern about the immediacy of the effect. The stents do not typically eliminate the aneurysmal blood flow immediately, which leaves the aneurysm susceptible to re-rupture because of tenuous aneurysm wall integrity at the site of primary rupture.
To mitigate this risk, the reviewers say, some surgeons are adding a second technique when using flow diversion to treat a subarachnoid aneurysm. Coil packing of the aneurysm dome may be the adjunctive technique, or partial coiling may be used to prevent re-rupture in the acute period, followed by staged flow diversion weeks later, after recovery. The latter strategy is meant to prevent hemorrhagic complications resulting from antiplatelet therapy during the initial hospitalization.
Dr. Patel’s team notes that the first-generation flow diverter in the U.S. (Pipeline, Covidien EV3 Neurovascular, Plymouth, MN) presented several technical problems. In 2015, the FDA approved a redesigned device, Pipeline Flex.
Other innovations are a stent that is coated with phosphorylcholine to decrease thrombogenicity, and an expanding spherical mesh device that is placed completely within the aneurysm dome, so that it does not require thromboembolism prophylaxis. Experience with these newer devices is still preliminary.
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