Christina Iosif

Flow-diverting stents for intracranial bifurcation aneurysm treatment.

BACKGROUND Although initially considered safe when covering bifurcation sites, flow-diverting stents may provoke thrombosis of side branches that are covered during aneurysm treatment. OBJECTIVE To understand the occurrence and clinical expression of side-branch remodeling in distal intracranial arterial sites after flow diverter deployment by means of correlation of imaging and clinical data. METHODS We analyzed our prospectively collected data on a series of patients treated with flow diverters for intracranial aneurysms at bifurcation sites. From February 2011 to May 2013, 32 patients with 37 aneurysms (anterior communicating artery, 9 [24.3%]; anterior cerebral artery, 5 [13.5%]; middle cerebral artery, 19 (51.4%); terminal internal carotid artery, 4 [10.8%]) were treated. We divided aneurysms into 2 groups based on the side branches covered by the stent during treatment. Group A consisted of cases with side branches that supplied brain territories also receiving a direct collateral supply. Group B consisted of cases in which side branches supplied territories without direct collateral supply. The 2 groups were compared statistically. RESULTS Total exclusion occurred in 97.3% of aneurysms at follow-up. Initial modified Rankin Scale (mRS) score was 0 to 1 for 29 patients (90.6%) and 2 for 3 patients (9.4%). New permanent neurological deficit was reported in 3 patients (9.4%). At the 6-month follow-up, the mRS score was 0 to 1 for 31 patients (96.8%) and 3 for 1 patient (3.2%). Although 78.5% of side branches in group A underwent narrowing or occlusion after 6 months, no new stroke was found on magnetic resonance imaging. CONCLUSION Symptomatic modifications of side branches after flow diverter treatment depend on the extent and type of collateral supply.

Endothelialization of over- and undersized flow-diverter stents at covered vessel side branches: An in vivo and in silico study.

Although flow-diverting devices are promising treatment options for intracranial aneurysms, jailed side branches might occlude leading to insufficient blood supply. Especially differences in the local stent strut compression may have a drastic influence on subsequent endothelialization. To investigate the outcome of different treatment scenarios, over- and undersized stent deployments were realized experimentally and computationally. Two Pipeline Embolization Devices were placed in the right common carotid artery of large white swine, crossing the right ascending pharyngeal artery. DSA and PC-MRI measurements were acquired pre- and post-stenting and after three months. To evaluate the stent strut endothelialization and the corresponding ostium patency, the swine were sacrificed and scanning electron microscopy measurements were carried out. A more detailed analysis of the near-stent hemodynamics was enabled by a realistic virtual stenting in combination with highly resolved Computational Fluid Dynamics simulations using case-specific boundary conditions. The oversizing resulted in an elongated stent deployment with more open stent pores, while for the undersized case a shorter deployment with more condensed pores was present. In consequence, the side branch of the first case remained patent after three months and the latter almost fully occluded. The virtual investigation confirmed the experimental findings by identifying differences between the individual velocities as well as stent shear stresses at the distal part of the ostia. The choice of flow-diverting device and the subsequent deployment strategy strongly influences the patency of jailed side branches. Therefore, careful treatment planning is required, to guarantee sufficient blood supply in the brain territories supplied those branches.

Transvenous Embolization in Pediatric Plexiform Arteriovenous Malformations.

BACKGROUND Transvenous embolization is a developing concept for curative therapy of cerebral arteriovenous malformations (AVMs). The feasibility of this endovascular method has not been reported in children. OBJECTIVE To report our experience treating pediatric AVMs with the transvenous approach (TVA). METHODS A cohort of 7 pediatric patients (younger than 18 years of age) who underwent the TVA for cerebral AVMs between January 2012 and January 2014. The TVA was used alone or in conjunction with other arterial approaches in definitive embolization sessions. Patient demographics, AVM characteristics, clinical outcomes, and angiographic results were independently assessed. Pial arteriovenous fistulae and vein of Galen malformations were excluded. Control angiograms were obtained at 6 months, and curative treatment was determined by the anatomic obliteration of the nidus. RESULTS All patients had anatomic exclusion of the AVM. The mean size was 2 ± 0.6 cm, and hemorrhage was the most common presentation (100%, n = 7). Most AVMs were deeply placed (71%, n = 5), and a proximal approach to the nidus was achieved in all cases. Transvenous embolization alone was performed in 3 patients (43%), whereas combined arterial and venous embolization was required in 4 patients (57%). The mean follow-up period was 20.2 ± 10.5 months. There were no hemorrhagic or thromboembolic events, and venous infarction was not documented. No recurrence was documented. CONCLUSION This is the first report that demonstrates the feasibility of transvenous Onyx embolization of AVMs in the pediatric population. Such a technique may be considered in certain AVMs that meet anatomic criteria in which microsurgery and radiosurgery might not be indicated.

Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: animal flow model evaluation and preliminary results

OBJECTIVE The authors describe herein the creation of an animal model capable of producing quantifiable data regarding blood flow rate and velocity modifications in terminal and anastomotic types of cerebrofacial circulation. They also present the preliminary results of a translational study aimed at investigating the role of terminal and anastomotic types of circulation in arterial branches jailed by flow-diverting stents as factors contributing to arterial patency or occlusion. METHODS Two Large White swine were used to validate a terminal-type arterial model at the level of the right ascending pharyngeal artery (APhA), created exclusively by endovascular means. Subsequently 4 Large White swine, allocated to 2 groups corresponding to the presence (Group B) or absence (Group A) of terminal-type flow modification, underwent placement of flow-diverting stents. Blood flow rates and velocities were quantified using a dedicated time-resolved 3D phase-contrast MRA sequence before and after stenting. Three months after stent placement, the stented arteries were evaluated with digital subtraction angiography (DSA) and scanning electron microscopy (SEM). Patent (circulating) ostia quantification was performed on the SEM images. RESULTS Terminal-type flow modification was feasible; an increase of 75.8% in mean blood velocities was observed in the right APhAs. The mean blood flow rate for Group A was 0.31 ± 0.19 ml/sec (95% CI -1.39 to 2.01) before stenting and 0.21 ± 0.07 ml/sec (95% CI -0.45 to 0.87) after stenting. The mean blood flow rate for Group B was 0.87 ± 0.32 ml/sec (95% CI -1.98 to 3.73) before stenting and 0.76 ± 0.13 ml/sec (95% CI -0.41 to 1.93) after stenting. Mean flow rates after stenting showed a statistically significant difference between Groups A and B (Welch test). Mean and maximal blood velocities were reduced in Group A cases and did not decrease in Group B cases. Control DSA and SEM findings showed near occlusion of the jailed APhAs in both cases of anastomotic circulation (mean patent ostium surface 32,776 μm2) and patency in both cases of terminal-type circulation (mean patent ostium surface 422,334 μm2). CONCLUSIONS Terminal-type arterial modification in swine APhAs is feasible. Sufficient data were acquired to perform an a priori analysis for further research. Flow diversion at the level of the APhA ostium resulted in significant stenosis in cases of anastomotic circulation, while sufficient patency was observed in terminal-type circulation.

Spontaneous closure of intracranial dural arteriovenous fistulas: A report of 3 cases

Spontaneous closures of dural arteriovenous fistulas (dAVFs) are rare. We present spontaneous occlusion of dAVFs in 3 cases (one type IIa dAVF, one type IIb and one type III). Patients were 3 males with a mean age of 55 years (range 45-61). For two patients, the dAVF was revealed by hemorrhage. No head trauma was recorded at the interrogatory. Mean delay for spontaneous closure was 4 months (3-5 months). Review of the literature about this rare occurrence is presented and the factors that may lead to spontaneous occlusion of dAVFs are discussed.

Scanning electron microscopy for flow-diverting stent research: technical tips and tricks

Flow-diverting (FD) stents represent a new concept in the treatment of intracranial aneurysms with challenging anatomical dispositions. Having been introduced to clinical practice only in the last 5 years and featuring complex mechanisms of action, they are still under research. Scanning electron microscopy, as part of an animal research protocol, provides detailed surface observations of neointimal healing at the aneurysms neck, as well as covered side branch ostia, allowing for the confirmation of scientific hypotheses and observations. Technical adaptations of preparation protocols are presented based on a pilot study on Large White pigs, stented with FD stents at carotid bifurcations.

Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: from hemodynamic changes to ostia surface modifications

OBJECTIVE The outcome for jailing arterial branches that emerge near intracranial aneurysms during flow-diverting stent (FDS) deployment remains controversial. In this animal study, the authors aimed to elucidate the role of collateral supply with regard to the hemodynamic changes and neointimal modifications that occur from jailing arteries with FDSs. To serve this purpose, the authors sought to quantify 1) the hemodynamic changes that occur at the jailed arterial branches immediately after stent placement and 2) the ostia surface values at 3 months after stenting; both parameters were investigated in the presence or absence of collateral arterial flow. METHODS After an a priori power analysis, 2 groups (Group A and Group B) were created according to an animal flow model for terminal and anastomotic arterial circulation; each group contained 7 Large White swine. Group A animals possessed an anastomotic-type arterial configuration to supply the territory of the right ascending pharyngeal artery (APhA), while Group B animals possessed a terminal-type arterial configuration to supply the right APhA territory. Subsequently, all animals underwent FDS placement, thereby jailing the right APhAs. Mean flow rates and velocities inside the jailed branches were quantified using time-resolved 3D phase-contrast MR angiography before and after stenting. Three months after stent placement, the jailed ostia surface values were quantified on scanning electron micrographs. The data were analyzed using descriptive statistics and group comparisons with parametric and nonparametric tests. RESULTS The endovascular procedures were feasible, and there were no findings of in situ thrombus formation on postprocedural optical coherence tomography or ischemia on postprocedural diffusion-weighted imaging. In Group A, the mean flow rate values at the jailed right APhAs were reduced immediately following stent placement as compared with values obtained before stent placement (p = 0.02, power: 0.8). In contrast, the mean poststenting flow rates for Group B remained similar to those obtained before stent placement. Three months after stent placement, the mean ostia surface values were significantly higher for Group B (527,911 ± 306,229 μm2) than for Group A (89,329 ± 59,762 μm2; p < 0.01, power: 1.00), even though the initial dimensions of the jailed ostia were similar between groups. A statistically significant correlation was found between groups (A or B), mean flow rates after stent placement, and ostia surface values at 3 months. CONCLUSIONS When an important collateral supply was present, the jailing of side arteries with flow diverters resulted in an immediate and significant reduction in the flow rate inside these arteries as compared with the prestenting values. In contrast, when competitive flow was absent, jailing did not result in significant flow rate reductions inside the jailed arteries. Ostium surface values at 3 months after stent placement were significantly higher in the terminal group of jailed arteries (Group B) than in the anastomotic group (Group A) and strongly correlated with poststenting reductions in the velocity value.

Is a high initial World Federation of Neurosurgery (WFNS) grade really associated with a poor clinical outcome in elderly patients with ruptured intracranial aneurysms treated with coiling

Background Coiling of ruptured intracranial aneurysms in elderly patients remains debatable in terms of technical feasibility and clinical outcome. Aims In this observational cohort study we aimed to assess the technical feasibility, complication profile and clinical outcomes of elderly patients with subarachnoid hemorrhage (SAH) treated with endovascular therapy. Methods The study included 59 consecutive patients (47 women) aged ≥70 years (mean age 76 years, range 71–84) admitted to our institution with SAH from January 2002 to July 2011. The patients were treated for 66 aneurysms (regular coiling: n=62 (94%), balloon-assisted technique: n=2 (3%), stent and coil technique: n=2 (3%)). World Federation of Neurosurgery (WFNS) grade at admission was 1 in 13 patients, 2 in 23 patients, 3 in 8 patients, 4 in 11 patients and 5 in 4 patients. We analysed data by univariate and multivariate statistical analyses with an emphasis on the initial clinical situation, complications and clinical outcome. Results The technical success rate was 98% with a procedure-related deficit rate of 10% and procedure-related death rate of 5%. The Glasgow Outcome Scale score at 6 months was 1 in 15 patients (25.4%), 2 in 8 patients (13.6%), 3 in 14 patients (23.7%), 4 in 11 patients (18.6%) and 5 in 11 patients (18.6%). Patients admitted with a high initial WFNS grade did not differ statistically in terms of clinical outcome. The final clinical outcome was not significantly correlated with age, initial Fisher score or procedure-related complications. Conclusions Endovascular treatment of elderly patients with ruptured cerebral aneurysms is feasible, safe and beneficial regardless of the presenting WFNS score.

Balloon-assisted microcatheter navigation for AVM embolization: technical note

Recurrent feeders may preclude a successful arterial catheterization of arteriovenous malformations (AVMs). In this paper, the authors report their experience with the use of a compliant balloon to assist the microcatheter navigation in AVMs supplied by feeders with recurrent configuration. Eight patients with AVMs supplied by recurrent feeders had unsuccessful microcatheter navigation after multiple attempts to catheterize the pedicle. A compliant balloon was inflated in the parent artery immediately after the origin of the feeder. The microcatheter was then advanced over the wire while the balloon provided support for the navigation. Distal access close to the nidus was achieved in all cases. Anatomical cure was documented in 75% cases. There were no arterial perforations or thromboembolic events. The described technique is a straightforward method for providing support to microcatheter navigation in certain cases of cerebral AVMs supplied by recurrent arterial feeders. This simple yet effective maneuver may enhance outcomes of AVM embolization by eliminating the need for excessive attempts of catheterization.

Safety and effectiveness of the Low Profile Visualized Intraluminal Support (LVIS and LVIS Jr) devices in the endovascular treatment of intracranial aneurysms: results of the TRAIL multicenter observational study

Background and purpose To evaluate the safety and effectiveness of the low-profile braided intracranial stents called the Low Profile Visualized Intraluminal Support (LVIS) devices for stent-assisted coil embolization of wide-necked intracranial aneurysms. Materials and methods This was a prospective, multicenter, observational study of unruptured and ruptured intracranial aneurysms treated with the LVIS devices. Imaging and clinical data were independently analyzed respectively by CoreLab and Clinical Event Committee. Primary endpoints were clinical safety, effectiveness, and angiographic stability of the results at 6 and 18 months. Results Ten centers participated in the study; 102 patients were included and 90 patients (42.2% men, 57.8% women) were eventually analyzed, among which 27 (30.0%) had multiple aneurysms. Twenty-three (25.6%) were ruptured aneurysms, four of which (4.4%) were treated in the acute phase. One aneurysm was treated per patient; 92 LVIS and LVIS Jr devices were placed overall. The total aneurysm occlusion rate was 91.0% on immediate post-procedure angiograms, which remained unchanged at 6-month follow-up and was 92.4% at 18-month follow-up. One patient (1.1%) underwent retreatment between 6 and 18 months of follow-up. A modified Rankin score of 0 was documented for most cases immediately after the procedure (86.7%) and at 6-month (86.8%) and 18-month (83.3%) follow-up. The overall permanent morbidity rate at 18 months was 5.6% and the overall rate of events with sequelae related to the stent was 2.2%. The 18-month procedure-related mortality rate was 3.3%. No patient was deemed to require retreatment at 18-month follow-up. Conclusion The LVIS/LVIS Jr endovascular devices are safe and effective in the treatment of ruptured and unruptured intracranial aneurysms, with acceptable complication rates, very high immediate total occlusion rates, and stable angiographic results.