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June 13, 2024


The results, from a multicenter study, confirm previous findings showing flow diversion compares well with other treatment approaches.


Flow diversion holds up well as a first-line option for the treatment of blood blister aneurysms, according to a retrospective multicenter analysis published online February 24, 2018, in the Journal of NeuroInterventional Surgery.


“Blister-like aneurysms are often not easy to detect at the first angiography due to their small dimensions and unusual locations, but because of their rapid growth, they become more evident within a few days,” Simone Peschillo, MD, PhD (Policlinico Umberto I, Rome, Italy), who was not involved in the study, told Neurovascular Exchange.


“These lesions can be dangerous because of their propensity to rupture intraoperatively and postoperatively,” he said. “Originally, they were thought to occur exclusively in the internal carotid artery [ICA]; however, recent studies have shown that this type of vascular lesion can be found anywhere in the circle of Willis.”


Lead author Maxim Mokin, MD, PhD (University of South Florida, Tampa, FL), also in an interview with NVX, added that blood blister-like aneurysms are particularly challenging to treat because “these lesions are very small (only 1-3 mm typically) and occur at vessel segments with a thin wall, making it challenging for a neurosurgeon to use traditional approaches (clipping) or for a neurointerventionalist to use coils.”


While there are many treatment options for blood blister-like aneurysms, flow diversion is the first-line choice in most centers that routinely perform both open and endovascular treatments, he added. But questions still remain regarding its safety and durability.


Most See Complete Obliteration, Good Clinical Outcome


Mokin and colleagues reported on the multicenter experience of using the Pipeline embolization device (Medtronic) to treat 43 consecutive patients with 45 blood blister aneurysms located at nonbranching segments along the anteromedial wall of the supraclinoidal ICA.


Angiographic data at an average of 4 months’ follow-up were available for 30 patients with 32 aneurysms. The imaging revealed complete obliteration in most of the treated aneurysms (87.5%), while three (9.4%) had reduced filling and only one (3.1%) continued to have persistent filling.


There was no relationship between the rate of complete occlusion on angiographic follow-up and the size of aneurysm (≤ 2 mm vs > 2 mm; P = 0.354) or the use of adjunct coiling (P = 0.865).


Clinical follow-up data were available for 38 of 43 patients. Of these, 68% had a good clinical outcome at 30 days. Rates of immediate procedural and delayed complications were low at 16% and 5%, respectively, but included one case of fatal delayed rerupture after the initial treatment.


Knowledge Gaps Still Left to Fill


According to both Mokin and Peschillo, these findings are in line with previous studies showing a clinical advantage for flow diversion over other treatment options for blood blister aneurysms.


Indeed, in his recent meta-analysis, “endovascular treatment seems to be associated with lower morbidity and mortality compared with surgical approaches,” Peschillo said. “Concerning angiographic outcome, surgery was more likely to achieve early, complete occlusions, whereas there was an improvement of 32.4% between the early occlusion status and the follow-up occlusion status in the endovascular group. This difference did not, however, seem to influence the outcome; it appears clear that the clinical status at the outset has a much greater effect than complete occlusion of the aneurysm. Considering the numerically larger subgroups, the percentage of good outcomes (mRS 0-2) in the endovascular group was higher.”


Similarly, one of key findings of this study, pointed out Mokin, “was that even if persistent filling of the aneurysm is seen immediately after a flow diversions device is placed, most of these lesions will completely thrombose on follow-up imaging and the risk of rerupture is very low.”


But questions remain. A few patients in this study were lost to follow-up, and Mokin said they noticed “variations in how the antiplatelet regimen was initiated and continued at our participating sites.” Also, as an increasing number of flow diversion devices enter the market, it will be necessary to determine how they perform in comparison to the Pipeline.


“Vasospasm remains a challenge in some patients, and the combination of vasospasm, strokes, and dual antiplatelet therapy needs to be considered very carefully,” he added.


Peschillo also observed that the precise definition of blood blister aneurysms varies subtly from study to study. For the sake of future research, he said, it is important to settle on just one, and he and his team have proposed one in their meta-analysis.



Mokin M, Chinea A, Primiani CT, et al. Treatment of blood blister aneurysms of the internal carotid artery with flow diversion. J NeuroInterv Surg. 2018;Epub ahead of print.


Mokin and Peschillo report no relevant conflicts of interest.