Editorial

Safety and efficacy of flow-diverter stents in endovascular treatment of intracranial aneurysm: Interest of the prospective DIVERSION observational study

Flow diverters are considered as an essential tool in the stent-based treatment of complex intracranial aneurysms. We report here a subgroup analysis of the nationwide prospective DIVERSION study to investigate the safety and efficacy of the Silk flow diverter at 12 months follow-up.

We performed a subgroup analysis of patients included in the DIVERSION, a national prospective cohort study including all flow diverters placement between 2012 and 2014 in France, and treated with the Silk. The primary outcome was the morbi-mortality at 12 months, including death, morbidity event and aneurysm retreatment within 12 months post-treatment. All reported serious events were adjudicated by an independent Data Safety and Monitoring Board. Satisfactory occlusion was defined as 3 or 4 on Kamran's scale by an independent imaging core laboratory during follow-up.

A total of 102 procedures involving 101 patients (mean age ± standard deviation, 54.3 ± 13.5 years) harbouring 118 aneurysms (113/118 located in the anterior circulation; mean size 8.2 ± 7.1 mm) were included. During the 12-month follow-up, 34 (33.3%) procedures experienced at least one morbi-mortality event: 3 deaths, 27 morbidity events and 4 retreatments. Overall, 1/3 deaths and 10/27 morbidity events were related to the device and/or the procedure, leading to a specific survival rate and a specific free-morbidity survival rate at 12 months of 98.98% [95% confidence interval, 92.98%–99.86%] and 89.73% [95%CI, 81.71%–94.36%], respectively. The rate of permanent-related neurological deficit was 5.9% within 12 months. One year follow-up imaging showed satisfactory occlusion in 82.2% of cases.

Flow diversion with the Silk device has a reasonable safety and effectiveness profile for the endovascular treatment of intracranial aneurysms.

To quantify the relationship and to demonstrate redundancies between hemodynamic and structural parameters before and after virtual treatment with a flow diverter device (FDD) in cerebral aneurysms.

Steady computational fluid dynamics (CFD) simulations were performed for 10 cerebral aneurysms where FDD treatment with the SILK device was simulated by virtually reducing the porosity at the aneurysm ostium. Velocity and pressure values proximal and distal to and at the aneurysm ostium as well as inside the aneurysm were quantified. In addition, dome-to-neck ratios and size ratios were determined. Multiple correlation analysis (MCA) and hierarchical cluster analysis (HCA) were conducted to demonstrate dependencies between both structural and hemodynamic parameters.

Velocities in the aneurysm were reduced by 0.14 m/s on average and correlated significantly (p<0.05) with velocity values in the parent artery (average correlation coefficient: 0.70). Pressure changes in the aneurysm correlated significantly with pressure values in the parent artery and aneurysm (average correlation coefficient: 0.87). MCA found statistically significant correlations between velocity values and between pressure values, respectively. HCA sorted velocity parameters, pressure parameters and structural parameters into different hierarchical clusters. HCA of aneurysms based on the parameter values yielded similar results by either including all (n=22) or only non-redundant parameters (n=2, 3 and 4).

Hemodynamic and structural parameters before and after virtual FDD treatment show strong inter-correlations. Redundancy of parameters was demonstrated with hierarchical cluster analysis.

Endovascular treatment of small anterior choroidal artery (AChA) aneurysms can be challenging, especially if the AChA arises from the sac. Preserving its patency during embolization is as important as obliterating the aneurysm. We describe a variant of the “protective microcatheter technique” (PMT) in a series of six patients with AChA aneurysms where the AChA emerged from the sac.

Three different microcatheters (KT) were used. The first microcatheter was placed in the AChA to protect it. A remodeling balloon-catheter was then positioned in the internal carotid artery to stabilize the coils during embolization and to control a potential rupture. The third microcatheter was finally used to coil the aneurysm.

Mean sac size of anterior choroidal artery aneurysms was 2 × 2 × 2 mm. All aneurysms were successfully occluded. There was neither ischemic complication nor ruptured aneurysm during endovascular treatment. A final angiogram demonstrated AChA patency in all cases.

The 3KT-PMT for AChA aneurysms appears to be safe and effective to prevent AChA occlusion during aneurysm coiling, especially when the AChA arises from the sac.

Unruptured intracranial aneurysms are frequently and incidentally discovered with noninvasive imaging and the decision for preventive treatment is supported by epidemiologic and statistics data, lacking personalized argumentation about individual aneurysm behavior and inflammatory status of its wall. After a review of hemodynamic forces leading to aneurysm genesis and interaction with inflammation onset within aneurysmal wall, we will successively detail routine imaging methods for the aneurysmal wall and their respective contribution. Then, we will draw up the inventory of different experimental imaging and in vitro methods for future investigation of the aneurysmal wall. We emphasize the need for cooperation with various specialties: histopathology, genetics, and immunology in order to understand the natural history of the aneurysmal sac leading most often to stability but elsewhere to aneurysmal growth, thrombosis or rupture. A description of a research protocol devoted to aneurysmal wall inflammation and recently accepted in our university is introduced.

Recanalization of post-embolization cerebral aneurysms remains a serious problem that influences treatment outcomes. Matrix2 is a bioactive, bio-absorbable, detachable coil that was developed to reduce the risk of recanalization. We examined the short-term efficacy of the Matrix2 coil system, and evaluated the temporal profile of tissue proliferation in a swine experimental aneurysm model compared with the bare platinum (BP) coil.

Thirty-six experimental aneurysms were created in 18 swine. All aneurysms were tightly packed with Matrix2 or BP coils. Comparative histologic and morphologic analyses were undertaken 1, 2 and 4 weeks post-embolization.

Endothelial-like cells were observed partially lining the aneurysmal opening one week post-embolization with both coil types. At two and four weeks post-embolization, the aneurysms treated with Matrix2 coils had more extensive areas of organized thrombus than those packed with BP coils, but the numbers of functional proliferating endothelial cells identified by immunohistochemistry in the tissue were broadly comparable between the groups. Moreover, morphological analysis suggested there were more mature endothelial cells in aneurysms treated with bare platinum rather than Matrix2 coils.

Our results indicate that aneurysms embolized with Matrix2 coils build thicker scaffolds for endothelialization, but this is not necessarily evidence of earlier tissue proliferation and maturation than those embolized with BP coils. Matrix2 coils may not be superior to BP coils for preventing aneurysmal recanalization after endovascular treatment of cerebral aneurysms.