Usefulness of Non–Contrast-Enhanced MR Angiography Using a Silent Scan for Follow-Up after Y-Configuration Stent-Assisted Coil Embolization for Basilar Tip Aneurysms

BACKGROUND AND PURPOSE:Y-configuration stent-assisted coil embolization is used for treating wide-neck aneurysms. Noninvasive alternatives to x-ray DSA for follow-up after Y-configuration stent-assisted coil embolization treatment are required. This study aimed to assess the usefulness of non–contrast-enhanced MRA by using a Silent Scan (silent MRA) for follow-up after Y-configuration stent-assisted coil embolization for basilar tip aneurysms.MATERIALS AND METHODS:Seven patients treated with Y-configuration stent-assisted coil embolization for basilar tip aneurysms underwent silent MRA, 3D TOF-MRA, and DSA. Silent MRA and 3D TOF-MRA images were obtained during the same scan session on a 3T MR imaging system. Two neuroradiologists independently reviewed both types of MRA images and subjectively scored the flow in the stents on a scale of 1 (not visible) to 5 (nearly equal to DSA) by referring to the latest DSA image as a criterion standard. Furthermore, we evaluated the visualization of the neck remnant.RESULTS:In all patients, the 2 observers gave a higher score for the flow in the stents on silent MRA than on 3D TOF-MRA. The average score ± standard deviation was 4.07 ± 0.70 for silent MRA and 1.93 ± 0.80 (P < .05) for 3D TOF-MRA. Neck remnants were depicted by DSA in 5 patients. In silent MRA, neck remnants were depicted in 5 patients, and visualization was similar to DSA; however, in 3D TOF-MRA, neck remnants were depicted in only 1 patient.CONCLUSIONS:Silent MRA might be useful for follow-up after Y-configuration stent-assisted coil embolization.

In recent years, intracranial stents have been used for the treatment of wide-neck aneurysms. The Y-configuration stent-assisted coil embolization technique has been generally used for wide-neck bifurcation aneurysms such as those at the tip of the basilar artery (BA).^1–6 The Y stent deploys 2 stents from the BA to the bilateral posterior cerebral artery (PCA). The 2 stents overlap in the distal BA trunk, with 1 stent penetrating the mesh of the other. The use of 2 stents in a “Y” configuration to assist with coil embolization for bifurcation aneurysms has been accepted for broad-neck aneurysms.X-ray DSA is the standard technique used for follow-up after an intracranial stent. However, DSA is an invasive technique that carries a risk of neurologic complications, contrast materials, and x-ray radiation.^7–10On the other hand, 3D TOF-MRA is widely used as a noninvasive substitute for DSA for the follow-up of coiled aneurysms.^11–14 Although there have been reports of 3D TOF-MRA being used after stent-assisted coil embolization,^12,13 it remains difficult to visualize flow in an intracranial stent when using this method because of magnetic susceptibility and radiofrequency shielding. Therefore, contrast-enhanced MRA (CE-MRA) is used for follow-up after stent-assisted coil embolization. However, the use of contrast materials in CE-MRA is associated with nephrogenic systemic fibrosis and anaphylactic shock; therefore, this technique might not be appropriate for repeated examinations.^15–17 Furthermore, it has been reported that gadolinium-based contrast material accumulates in the dentate nucleus and globus pallidus.¹⁸Silent MRA uses a Silenz pulse sequence (GE Healthcare, Milwaukee, Wisconsin) containing an ultrashort echo time (UTE) combined with arterial spin-labeling. Data acquisition is based on 3D radial sampling, and the arterial spin-labeling technique is used as a preparation pulse for visualization of the blood flow.^19,20 It is a non–contrast-enhanced MRA technique; therefore, it is better for the patient and suitable for repeated follow-ups.UTE of silent MRA minimizes phase dispersion of the labeled blood flow signal and decreases magnetic susceptibility to coils and stents. Thus, silent MRA can evaluate the blood flow in an intracranial stent.²⁰To the best of our knowledge, there have been no studies of the use of non–contrast-enhanced MRA for follow-up after Y-configuration stent-assisted coil embolization for basilar tip aneurysms. Therefore, in the present study, we evaluated the usefulness of silent MRA compared with 3D TOF-MRA for follow-up after Y-configuration stent-assisted coil embolization for basilar tip aneurysms.     

Non-Contrast-Enhanced Silent Scan MR Angiography of Intracranial Anterior Circulation Aneurysms Treated with a Low-Profile Visualized Intraluminal Support Device

BACKGROUND AND PURPOSE:The Low-Profile Visualized Intraluminal Support Device comprises a small-cell nitinol structure and a single-wire braided stent that provides greater metal coverage than previously reported intracranial stents, as well as assumed strong susceptibility artifacts. This study aimed to assess the benefits of non-contrast-enhanced MRA by using a Silent Scan (Silent MRA) for intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.MATERIALS AND METHODS:Thirty-one aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents were assessed by using Silent MRA, 3D TOF-MRA, and x-ray DSA. The quality of MRA visualization of the reconstructed artery was graded on a 4-point scale from 1 (not visible) to 4 (excellent). Aneurysm occlusion status was evaluated by using a 2-grade scale (total occlusion/remnant [neck or aneurysm]). Weighted κ statistics were used to evaluate interobserver and intermodality agreement.RESULTS:The mean scores ± SDs for Silent MRA and 3D TOF-MRA were 3.16 ± 0.79 and 1.48 ± 0.67 (P < .05), respectively, with substantial interobserver agreement (κ = 0.66). The aneurysm occlusion rates of the 2-grade scale (total occlusion/remnant [neck or aneurysm]) were 69%/31% for DSA, 65%/35% for Silent MRA, and 92%/8% for 3D TOF-MRA, respectively. The intermodality agreements were 0.88 and 0.30 for DSA/Silent MRA and DSA/3D TOF-MRA, respectively.CONCLUSIONS:Silent MRA seems to be useful for visualizing intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.

Endovascular treatment involving coil embolization is commonly used to manage both ruptured and unruptured intracranial aneurysms.^1,2 In recent years, intracranial stents, including the Neuroform^3,4 (Stryker, Kalamazoo, Michigan) and Enterprise stents^5,6 (Codman & Shurtleff, Raynham, Massachusetts), have been implemented for the stent-assisted coil embolization of wide-neck aneurysms. Both types of stents comprise nitinol and are self-expandable. The Neuroform stent features an open-cell design with stainless steel and platinum markers,^7,8 whereas the Enterprise stent is a closed-cell design with tantalum markers.^9,10This study implemented the Low-Profile Visualized Intraluminal Support Device^11–14 (LVIS Jr. stent; MicroVention, Tustin, California), a self-expandable nitinol single-wire braided stent comprising 1.5-mm cells. The LVIS Jr. stent contains 3 radiopaque tantalum markers on the proximal and distal tines and 3 tantalum helical strands in the stent body^13,14; thus, it provides higher metal coverage (12%–21%)^11–13 relative to previously reported stents. Accordingly, stent-related magnetic susceptibility during MR imaging is a topic of research interest.Despite reports of the use of 3D TOF-MRA after stent-assisted coil embolization,⁹ the radiofrequency shielding and susceptibility artifacts make it difficult to visualize flow in an intracranial stent with this technique. Because the LVIS Jr. stent is composed of nitinol and features a braided component and higher metal coverage relative to earlier stents, this device may not facilitate depiction of an intracranial stent with 3D TOF-MRA for radiofrequency shielding and susceptibility artifacts.Silent Scan (GE Healthcare, Milwaukee, Wisconsin) MRA (Silent MRA) is a non-contrast-enhanced MRA technique that uses an ultrashort TE (UTE) combined with arterial spin-labeling,¹⁵ which is used as a preparation pulse to visualize blood flow. Subsequent data acquisition is based on 3D radial sampling.^15,16 Because UTE decreases the susceptibility artifacts associated with metallic devices, Silent MRA could potentially reduce the artifacts associated with braided, high-metal-coverage stents. Accordingly, we evaluated the efficacy of Silent MRA versus 3D TOF-MRA for intracranial anterior circulation aneurysms treated with LVIS Jr. stent-assisted coil embolization.     

Identification of the Inflow Zone of Unruptured Cerebral Aneurysms: Comparison of 4D Flow MRI and 3D TOF MRA Data

BACKGROUND AND PURPOSE:The hemodynamics of the inflow zone of cerebral aneurysms may be a key factor in coil compaction and recanalization after endovascular coil embolization. We performed 4D flow MR imaging in conjunction with 3D TOF MRA and compared their ability to identify the inflow zone of unruptured cerebral aneurysms.MATERIALS AND METHODS:This series comprised 50 unruptured saccular cerebral aneurysms in 44 patients. Transluminal color-coded 3D MRA images were created by selecting the signal-intensity ranges on 3D TOF MRA images that corresponded with both the luminal margin and the putative inflow.RESULTS:4D flow MR imaging demonstrated the inflow zone and yielded inflow velocity profiles for all 50 aneurysms. In 18 of 24 lateral-projection aneurysms (75%), the inflow zone was located distally on the aneurysmal neck. The maximum inflow velocity ranged from 285 to 922 mm/s. On 4D flow MR imaging and transluminal color-coded 3D MRA studies, the inflow zone of 32 aneurysms (64%) was at a similar location. In 91% of aneurysms whose neck section plane angle was <30° with respect to the imaging section direction on 3D TOF MRA, depiction of the inflow zone was similar on transluminal color-coded 3D MRA and 4D flow MR images.CONCLUSIONS:4D flow MR imaging can demonstrate the inflow zone and provide inflow velocity profiles. In aneurysms whose angle of the neck-section plane is obtuse vis-a-vis the imaging section on 3D TOF MRA scans, transluminal color-coded 3D MRA may depict the inflow zone reliably.

Although endovascular coil embolization has become a major tactic to address cerebral aneurysms, recanalization or recurrence, which may result in rebleeding, are important problems. Recanalization was reported in 6.1%–39.8% of patients who had undergone endovascular treatment,^1–6 and a meta-analysis found that 20.8% of treated aneurysms recurred.³ The rate of rerupture after endovascular treatment for ruptured aneurysms has ranged from 0.11% to 5.3%,^1,4,6 and the rupture rate in the first year after coil embolization was reported as 2.5%⁷ and 2.2%.⁸ Because hemodynamics acting on the aneurysmal inflow zone may play a key role in the development of coil compaction or recanalization after endovascular coil embolization, the aneurysmal inflow zone must be packed densely to preserve the durability of aneurysm obliteration and to prevent rerupture.^9–15The inflow through the aneurysmal neck into the dome can be seen on 3D TOF MRA images.^13,16,17 Satoh et al,^16,17 who used conventional 3D TOF MRA techniques to select threshold ranges based on the signal intensity of the volume-rendering data, determined the spatial signal-intensity distribution in aneurysms. They developed transluminal color-coded 3D MRA (TC 3D MRA) to improve visualization of the aneurysmal inflow. More recently, 4D flow MR imaging based on time-resolved 3D cine phase-contrast MR imaging techniques was used to evaluate the hemodynamics of cerebral aneurysms.^18–27 However, 4D flow MR imaging requires additional time for data acquisition, and TC 3D MRA may be a convenient alternative to 4D flow MR imaging for identifying the aneurysmal inflow zone.Here, we compared the ability of 4D flow MR imaging and TC 3D MRA to identify the inflow zone of cerebral aneurysms.     

High-Resolution C-Arm CT and Metal Artifact Reduction Software: A Novel Imaging Modality for Analyzing Aneurysms Treated with Stent-Assisted Coil Embolization

BACKGROUND AND PURPOSE:Combination of high-resolution C-arm CT and novel metal artifact reduction software may contribute to the assessment of aneurysms treated with stent-assisted coil embolization. This study aimed to evaluate the efficacy of a novel Metal Artifact Reduction prototype software combined with the currently available high spatial-resolution C-arm CT prototype implementation by using an experimental aneurysm model treated with stent-assisted coil embolization.MATERIALS AND METHODS:Eight experimental aneurysms were created in 6 swine. Coil embolization of each aneurysm was performed by using a stent-assisted technique. High-resolution C-arm CT with intra-arterial contrast injection was performed immediately after the treatment. The obtained images were processed with Metal Artifact Reduction. Five neurointerventional specialists reviewed the image quality before and after Metal Artifact Reduction. Observational and quantitative analyses (via image analysis software) were performed.RESULTS:Every aneurysm was successfully created and treated with stent-assisted coil embolization. Before Metal Artifact Reduction, coil loops protruding through the stent lumen were not visualized due to the prominent metal artifacts produced by the coils. These became visible after Metal Artifact Reduction processing. Contrast filling in the residual aneurysm was also visualized after Metal Artifact Reduction in every aneurysm. Both the observational (P < .0001) and quantitative (P < .001) analyses showed significant reduction of the metal artifacts after application of the Metal Artifact Reduction prototype software.CONCLUSIONS:The combination of high-resolution C-arm CT and Metal Artifact Reduction enables differentiation of the coil mass, stent, and contrast material on the same image by significantly reducing the metal artifacts produced by the platinum coils. This novel image technique may improve the assessment of aneurysms treated with stent-assisted coil embolization.

Stent-assisted coil embolization has recently become a common treatment strategy for wide-neck aneurysms.^1–4 However, poor visibility of the deployed stent during the procedure is considered a limitation because digital subtraction angiography does not allow the visualization of many intracranial stents. Ovalization or kinking of the deployed stent in the parent artery is another limitation.^5–8 This phenomenon, also called “inappropriate stent apposition,” can hinder the growth of neointimal coverage on the stent.⁹ Consequently, treated patients are required to undergo a prolonged postprocedural antiplatelet therapy.Recent reports show that C-arm CT with contrast has superior spatial resolution compared with conventional CT and allows the visualization of both the deployed stent and the contrast material.^8,10–12 However, once coil embolization is completed, prominent metal artifacts produced by the platinum coils degrade the image quality in the region adjacent to the coil mass, making it extremely difficult to evaluate the minuscule structures around the coil mass.A new prototype software, Metal Artifact Reduction (MAR; Siemens, Erlangen, Germany), dramatically reduces the metal artifacts in C-arm CT imaging by using a novel image-reconstruction algorithm.^13,14 Combined with currently available high spatial-resolution C-arm CT prototype implementation, the software enables visualization of meticulous structures around highly attenuated materials like platinum coils.To evaluate the efficacy of MAR, we treated experimental aneurysms with coil embolization by using a stent-assisted technique. Images obtained by using the high-resolution (HR) C-arm CT were processed with MAR. The images before and after MAR processing were compared, and an observational and quantitative analysis was performed.     

Dual Stenting Using Low-Profile LEO Baby Stents for the Endovascular Management of Challenging Intracranial Aneurysms

BACKGROUND AND PURPOSE:Endovascular treatment of wide-neck, complex, and distally located cerebral aneurysms is a challenging issue. This study evaluated the safety and efficacy of dual stent placement by using a low-profile stent system (LEO Baby) for the treatment of challenging distal intracranial aneurysms.MATERIALS AND METHODS:We retrospectively reviewed patients in whom at least 1 LEO Baby stent was used in the context of dual stent placement for the treatment of intracranial aneurysms. Patients who were treated with dual stent-assisted coil embolization and telescopic implantation of LEO Baby stents were included in the study. Clinical and angiographic findings, procedural data, and follow-up are reported.RESULTS:Twelve patients were included in this study. Three patients presented with subarachnoid hemorrhage in the subacute-chronic phase, and the remaining patients had unruptured aneurysms. Nine patients were treated by using the dual stent-assisted coiling method. X- (nonintersecting), Y- (intersecting and reversible), T-, and parallel-stent configurations were performed for the dual stent-assisted coiling procedures. Three patients were treated by using telescopic stent placement for a flow diverter–like effect. The procedures were successful in all cases. Technical complications without a significant clinical adverse event developed in 2 patients. The 3- and 6-month control MRAs and DSAs demonstrated complete occlusion of the aneurysms in all patients except 1. All patients had good clinical outcomes on follow-up (mRS ≤1).CONCLUSIONS:The results of this small study showed the feasibility of dual stent placement by using low-profile LEO Baby stents to treat distally located complex intracranial aneurysms.

Coiling of intracranial aneurysms is safe and effective, but endovascular treatment of wide-neck and anatomically complex aneurysms remains challenging.¹ Self-expandable intracranial stents have been used in the past decade to achieve successful and durable coil embolizations of these aneurysms.^2–4 The placement of a stent bridging the ostium of a wide-neck aneurysm creates a scaffold, which prevents the protrusion or herniation of coils into the parent artery and results in denser coil packing. In addition to the mechanical effect, intracranial stents have hemodynamic and biologic effects.^5–8 Stent deployment across the orifice of an aneurysm is thought to redirect blood flow from the sac of the aneurysm toward the distal parent artery and decrease the hemodynamic stress that contributes to thrombosis of the aneurysmal sac.⁹ Furthermore, stent-induced neointimal overgrowth leads to the healing of the neck of the aneurysm.¹⁰ On the basis of these effects, stent monotherapy has been proposed as an alternative strategy for the endovascular treatment of uncoilable and complex intracranial aneurysms.^9–11 The telescopic placement of self-expandable intracranial stents can adequately divert the blood flow, especially for the treatment of blisterlike aneurysms.¹²Recently, low-profile, self-expandable, braided intracranial stents (LEO Baby [Balt, Montmorency, France] and LVIS Jr. [MicroVention, Tustin, California]) have been available for the endovascular treatment of complex and/or distal aneurysms.^13,14 These low-profile intracranial stents can be deployed into arteries with diameters of <3.5 mm and delivered through microcatheters with an internal diameter of 0.0165 inches, which allows easier navigation in small-sized, delicate vessels.A single stent may not suffice for the endovascular treatment of wide-neck and geometrically complex bifurcation aneurysms with involvement of 1 or both side branches. Endovascular treatment of these complex aneurysms often necessitates the implantation of 2 stents (ie, dual stent placement) in various configurations, such as Y-, X-, or parallel configurations.^14–16This retrospective study evaluated the safety and efficacy of dual stent placement by using a low-profile stent system (LEO Baby) for the treatment of challenging intracranial aneurysms.     

Packing Density Necessary to Reach a High Complete Occlusion Rate in Circumferential Unruptured Intracranial Aneurysms Treated with Stent-Assisted Coil Embolization

BACKGROUND AND PURPOSE:This study is a homogeneous series of circumferential unruptured intracranial aneurysms with large necks treated with stent-assisted coil embolization. Our purpose was to demonstrate which value of packing density is required to produce a durable occlusion.MATERIALS AND METHODS:We retrospectively evaluated all patients with unruptured intracranial aneurysms who were treated with stent-assisted coil embolization having late angiographic control between 2004 and 2014, in a single large cerebrovascular referral center. To calculate the packing density, aneurysm volume, and coil volume, we used an on-line system.RESULTS:In 49 circumferential unruptured intracranial aneurysms treated with stent-assisted coil embolization, 38.7% (n = 19) had complete occlusion in the immediate control. Of those with incomplete occlusion, 80% (n = 24) progressed to complete occlusion in the late angiographic follow-up. At late angiographic control, 87.7% (n = 43) of aneurysms were completely occluded. All aneurysms with a packing density of ≥19% were completely occluded. Packing density was the only statistically significant predictor of complete occlusion. None of the aneurysms with complete occlusion at immediate control or at late angiographic control had recurrence.CONCLUSIONS:In circumferential aneurysms treated with stent-assisted coil embolization, packing density is the main predictor of complete occlusion. In this type of aneurysm, a packing density of ≥19% was enough to reach complete occlusion; knowing this is important to avoid higher packing densities that have more risk.

Unruptured intracranial aneurysms (UIAs) are present in 3% of the adult population and are increasingly detected due to more frequent use of noninvasive angiographic diagnostic imaging.^1–3Endovascular coiling for the treatment of intracranial aneurysms was first introduced into clinical use in 1990, and since then, the greatest concern has been the high recanalization rate, recently estimated to be approximately 20%.^4,5 This occurs more often in large-neck aneurysms,⁶ which are currently treated with stent-assisted coil embolization (SACE).In unassisted coil embolization, higher packing density (PD) rates are correlated with lower recanalization rates.^7–10 It is likely that in SACE treatment, the packing density necessary to reach a stable complete occlusion is lower, but there is no homogeneous study to confirm that possibility, to our knowledge.The purpose of this study was to demonstrate which value of PD is likely to produce durable occlusion in a homogeneous series of circumferential, large-neck UIAs treated with SACE in a single cerebrovascular referral center.     

Contrast-Enhanced Time-Resolved MRA for Follow-Up of Intracranial Aneurysms Treated with the Pipeline Embolization Device

BACKGROUND AND PURPOSE:Endovascular reconstruction and flow diversion by using the Pipeline Embolization Device is an effective treatment for complex cerebral aneurysms. Accurate noninvasive alternatives to DSA for follow-up after Pipeline Embolization Device treatment are desirable. This study evaluated the accuracy of contrast-enhanced time-resolved MRA for this purpose, hypothesizing that contrast-enhanced time-resolved MRA will be comparable with DSA and superior to 3D-TOF MRA.MATERIALS AND METHODS:During a 24-month period, 37 Pipeline Embolization Device–treated intracranial aneurysms in 26 patients underwent initial follow-up by using 3D-TOF MRA, contrast-enhanced time-resolved MRA, and DSA. MRA was performed on a 1.5T unit by using 3D-TOF and time-resolved imaging of contrast kinetics. All patients underwent DSA a median of 0 days (range, 0–68) after MRA. Studies were evaluated for aneurysm occlusion, quality of visualization of the reconstructed artery, and measurable luminal diameter of the Pipeline Embolization Device, with DSA used as the reference standard.RESULTS:The sensitivity, specificity, and positive and negative predictive values of contrast-enhanced time-resolved MRA relative to DSA for posttreatment aneurysm occlusion were 96%, 85%, 92%, and 92%. Contrast-enhanced time-resolved MRA demonstrated superior quality of visualization (P = .0001) and a higher measurable luminal diameter (P = .0001) of the reconstructed artery compared with 3D-TOF MRA but no significant difference compared with DSA. Contrast-enhanced time-resolved MRA underestimated the luminal diameter of the reconstructed artery by 0.965 ± 0.497 mm (27% ± 13%) relative to DSA.CONCLUSIONS:Contrast-enhanced time-resolved MRA is a reliable noninvasive method for monitoring intracranial aneurysms following flow diversion and vessel reconstruction by using the Pipeline Embolization Device.

Surgical clipping or endovascular coil embolization is generally the preferred treatment for intracranial aneurysms.¹ The Pipeline Embolization Device (PED; Covidien, Irvine, California) is an endovascular device that has redefined the scope of treatment for large, giant, wide-neck, or fusiform aneurysms or aneurysms having failed coil embolization, by reconstructing the parent artery and restoring its natural course.² The PED is designed for 85% reduction of blood flow within an aneurysm, which induces thrombosis² while keeping perforators and/or side branch vessels patent.³ Results from a multicenter prospective trial for treatment of uncoilable or failed large and giant ICA aneurysms with the PED demonstrated 99% technical success and 74% complete occlusion with 6% major ipsilateral stroke or death.⁴ Flow diversion with the PED has also been reported in the treatment of HIV vasculopathy, with fusiform cerebral aneurysms precluding parent vessel sacrifice or surgical bypass.⁵Digital subtraction angiography is the reference standard for the evaluation of aneurysms after endovascular treatment due to its unsurpassed spatial resolution; however, DSA is invasive and not without risks of puncture site and neurologic complications.⁶ Posttreatment follow-up of intracranial aneurysms after coil embolization with MRA by using 3D-TOF or contrast-enhanced techniques is a potential noninvasive alternative to DSA for the evaluation of PED-treated aneurysms without the use of ionizing radiation.⁷ Contrast-enhanced time-resolved MRA (CE-TR MRA) uses acquisition schemes aimed at accelerated data collection, primarily using parallel imaging algorithms and novel k-space trajectories to achieve high temporal resolution for multiphasic MRA examinations. This technique provides consistent, technologist-independent, optimal arterial enhancement for contrast-enhanced MRA and provides information on temporal contrast kinetics.^8,9 Use of CE-TR MRA has been reported in the evaluation of intracranial lesions such as arteriovenous malformations and dural arteriovenous fistulas and for assessment of stenosis of the extracranial carotid artery, and it seems to be a promising technique for evaluating aneurysms after stent-assisted coil embolization.^9–11We hypothesized that TR-CE MRA could provide information comparable with DSA and would be superior to 3D-TOF MRA in the evaluation of intracranial aneurysms and the parent artery following flow diversion and parent vessel reconstruction with the PED.     

Silk Flow-Diverter Stent for the Treatment of Intracranial Aneurysms: A Series of 58 Patients with Emphasis on Long-Term Results

BACKGROUND AND PURPOSE:The Silk flow-diverter stent is increasingly used to treat complex intracranial aneurysms including wide-neck, fusiform aneurysms. Sparse data are available concerning long-term results of this technique. We report our 5-year experience with Silk stent treatment of intracranial aneurysms.MATERIALS AND METHODS:A retrospective review of our prospectively maintained database identified all patients treated by the Silk stent in 2 institutions. Clinical charts, procedural data, and angiographic results were reviewed.RESULTS:Between July 2009 and May 2014, we identified 58 patients with 70 intracranial aneurysms. Endovascular treatment was successful in 93% of patients with 32 treated with the first-generation Silk stent and 26 with the new Silk+ stent. Mean follow-up in 47 patients was 22 months. Despite an 11% delayed complication rate, overall permanent neurologic morbidity was 5.5%. All complications were seen with the first-generation Silk stent. There was no procedure-related mortality. Long-term anatomic results showed 73% with complete occlusion, 16% with neck remnants, and 11% with incomplete occlusion. No recanalization or retreatment was performed. The midterm intrastent stenosis rate was 57%, of which 60% improved or disappeared, 28% were stable, and 12% led to vessel occlusion. Seventy-four percent of stenosis and all vessel occlusions occurred with the first-generation Silk stent.CONCLUSIONS:Endovascular treatment of complex intracranial aneurysms with the Silk stent is an effective therapeutic option. Despite a high rate of delayed complications with the first-generation stents, the current Silk+ stent appears safer. This treatment achieves a high rate of adequate and stable occlusion at long-term follow-up.

Endovascular treatment is now the first-intention treatment for both ruptured and unruptured intracranial aneurysms.^1–4 However, endovascular treatment of complex intracranial aneurysms (wide-neck and fusiform) remains technically challenging. On the other hand, aneurysm coil recanalization is an important issue in endovascular therapy, with approximately 20% of coiled aneurysms recanalized and 10% retreated.⁵ As previously shown, wide-neck aneurysms are highly prone to recanalization.⁶These relative limitations of standard coiling have contributed to the development of new endovascular approaches, including balloon-assisted coiling, stent-assisted coiling, flow diversion, and flow disruption. Flow-diverter stents have been developed, and they offer the potential of aneurysm occlusion related to flow disruption. Recently, several flow-diverter stents, such as the Silk flow diverter (Balt Extrusion, Montmorency, France), have been released, and short- and midterm results have been published.^7–15 Notwithstanding the early promise of these devices, important shortcomings have been reported. First, delayed complications, either hemorrhagic or thromboembolic, are not uncommon; second, the flow-diverter stent tolerance might be considered poor because of the relatively high rates of intrastent stenosis and parent artery occlusion (PAO) during follow-up.^7–15 To the best of our knowledge, sparse data are available about the long-term results of this technique, including stability of aneurysm occlusion and stent tolerance. These data are mandatory to define the place of flow-diverter stents in the therapeutic armamentarium of intracranial aneurysms. Therefore, the aim of our study was to report our 5-year experience with Silk stent treatment of intracranial aneurysms with an emphasis on long-term results.     

Temporary Stent-Assisted Coil Embolization as a Treatment Option for Wide-Neck Aneurysms

BACKGROUND AND PURPOSE:Simple coil embolization is often not a feasible treatment option in wide-neck aneurysms. Stent-assisted coil embolization helps stabilize the coils within the aneurysm. Permanent placement of a stent in an intracranial vessel, however, requires long-term platelet inhibition. Temporary stent-assisted coiling is an alternative technique for the treatment of wide-neck aneurysms. To date, only case reports and small case series have been published. Our purpose was to retrospectively analyze the effectiveness and safety of temporary stent-assisted coiling in a larger cohort.MATERIALS AND METHODS:Research was performed for all patients who had undergone endovascular aneurysm treatment in our institution (University Hospital Aachen) between January 2010 and December 2015. During this period, 355 consecutive patients had undergone endovascular aneurysm treatment. We intended to treat 33 (9.2%) of them with temporary stent-assisted coiling, and they were included in this study. Incidental and acutely ruptured aneurysms were included.RESULTS:Sufficient occlusion was achieved in 97.1% of the cases. In 94%, the stent could be fully recovered. Complications occurred in 5 patients (14.7%), whereas in only 1 case was the complication seen as specific to stent-assisted coiling.CONCLUSIONS:Temporary stent-assisted coiling is an effective technique for the treatment of wide-neck aneurysms. Safety is comparable with that of stent-assisted coiling and coiling with balloon remodeling.

Simple coil embolization is often not a feasible treatment option in wide-neck aneurysms. Stent-assisted coil embolization helps stabilize the coils within the aneurysm.¹ Permanent placement of a stent in an intracranial vessel, however, requires long-term platelet inhibition. Platelet inhibition is known to be associated with a higher bleeding risk.² Particularly in patients who require further treatment in an intensive care unit, such as patients with an acute subarachnoid hemorrhage, a higher bleeding risk should be avoided. In addition, dual platelet inhibition as recommended when stents are deployed permanently, increases the risk for cerebral hemorrhage within potentially existent ischemic brain tissue due to vasospasms.³ Hence, avoiding permanent stent placement is an advantage in patients with acute SAH.In the past, several techniques have been established for the treatment of wide-neck aneurysms. Common techniques are stent-assisted coiling, balloon-assisted coiling, double microcatheter coiling, and aneurysm treatment with dedicated devices such as the Woven EndoBridge (WEB; Sequent Medical, Aliso Viejo, California) device^4,5 or the Comaneci device (Rapid Medical, Yokneam, Israel).^6,7 The combination of balloon remodeling and stent-assisted coiling is another treatment option with possible achievement of higher occlusion rates.⁸Stent-assisted coiling and balloon remodeling seem to have a comparable complication rate in the literature, ranging between 10% and 20%.^9,10Treatment of wide neck-aneurysms is also possible with flow diverter devices with an occlusion rate of about 80%.¹¹ However, with a latency of 4–12 months to aneurysm thrombosis and the need for subsequent platelet inhibition, these are not a primary option in patients with an acutely ruptured intracranial aneurysm.Another treatment option for wide-neck aneurysms is temporary stent-assisted coiling.^12,13 For this purpose, 2 microcatheters are used. The first microcatheter is used to cover the aneurysm neck and deploy the stent. The second microcatheter is advanced into the aneurysm to perform coil embolization. Advancement of the second microcatheter into the aneurysm can be performed either before deployment of the stent or after stent deployment.¹⁴ The stent is deployed to cover the aneurysm neck but is not fully released. After coil embolization has been completed, the stent is recovered (Figs 1 and ​and2).2). In the unlikely event of coil protrusion during the process of recovery of the stent, recovery is stopped, the stent is deployed again, and it is released for permanent implantation. Temporary stent-assisted coiling is an established standard technique in our institution for the treatment of wide-neck aneurysms. Because to date, only case reports and small case series have been published, we analyzed a larger cohort of patients treated with temporary stent-assisted coiling.^12,13 Following, we present a retrospective analysis on the effectiveness and safety of temporary stent-assisted coiling.Open in a separate windowFig 1.A, An aneurysm of the anterior communicating artery before coiling. B, The same aneurysm partially coiled with a deployed Solitaire stent from the left A1 to the right A2 segment. C, The same aneurysm after complete coil embolization. The Solitaire stent has been recovered.Open in a separate windowFig 2.A, A carotid-T aneurysm before coiling. B, The same aneurysm partially coiled with the deployed Solitaire stent from the internal carotid artery to the left M1 segment. C, The same aneurysm after complete coil embolization. The Solitaire stent has been recovered.     

Contrast-Enhanced and Time-of-Flight MRA at 3T Compared with DSA for the Follow-Up of Intracranial Aneurysms Treated with the WEB Device

BACKGROUND AND PURPOSE:Imaging follow-up at 3T of intracranial aneurysms treated with the WEB Device has not been evaluated yet. Our aim was to assess the diagnostic accuracy of 3D–time-of-flight MRA and contrast-enhanced MRA at 3T against DSA, as the criterion standard, for the follow-up of aneurysms treated with the Woven EndoBridge (WEB) system.MATERIALS AND METHODS:From June 2011 to December 2014, patients treated with the WEB in our institution, then followed for ≥6 months after treatment by MRA at 3T (3D-TOF-MRA and contrast-enhanced MRA) and DSA within 48 hours were included. Aneurysm occlusion was assessed with a simplified 2-grade scale (adequate occlusion [total occlusion + neck remnant] versus aneurysm remnant). Interobserver and intermodality agreement was evaluated by calculating the linear weighted κ. MRA test characteristics and predictive values were calculated from a 2 × 2 contingency table, by using DSA data as the standard of reference.RESULTS:Twenty-six patients with 26 WEB-treated aneurysms were included. The interobserver reproducibility was good with DSA (κ = 0.71) and contrast-enhanced-MRA (κ = 0.65) compared with moderate with 3D-TOF-MRA (κ = 0.47). Intermodality agreement with DSA was fair with both contrast-enhanced MRA (κ = 0.36) and 3D-TOF-MRA (κ = 0.36) for the evaluation of total occlusion. For aneurysm remnant detection, the prevalence was low (15%), on the basis of DSA, and both MRA techniques showed low sensitivity (25%), high specificity (100%), very good positive predictive value (100%), and very good negative predictive value (88%).CONCLUSIONS:Despite acceptable interobserver reproducibility and predictive values, the low sensitivity of contrast-enhanced MRA and 3D-TOF-MRA for aneurysm remnant detection suggests that MRA is a useful screening procedure for WEB-treated aneurysms, but similar to stents and flow diverters, DSA remains the criterion standard for follow-up.

Endovascular treatment is now the first-line treatment for the management of ruptured and unruptured intracranial aneurysms.^1–4 However, the limitations of standard coiling for complex aneurysms (large, wide-neck, or developed in a bifurcation) have contributed to the development of new endovascular approaches, including balloon-assisted coiling, stent-assisted coiling, flow diversion, and flow disruption.⁵The Woven EndoBridge (WEB) aneurysm embolization system (Sequent Medical, Aliso Viejo, California) is an intrasaccular device designed to disrupt the intra-aneurysmal flow at the level of the neck.^6,7 Initial experience with the WEB–Dual-Layer (DL) showed the clinical utility of this device in wide-neck bifurcation aneurysms with high technical success and low acute morbidity and mortality.^6–16 Several WEB devices are now available, including Single-Layer (WEB-SL), Single-Layer Sphere (WEB-SLS), and WEB-DL subtypes.^12,13 Recently, Enhanced-Visualization (EV) versions were developed to improve fluoroscopic visualization of the devices during treatment.Because of the potential risk of aneurysm recanalization after endovascular treatment, regular imaging follow-up is recommended. Digital subtraction angiography is the criterion standard for the follow-up of intracranial aneurysms after endovascular treatment but has some disadvantages, including potential neurologic complications, iodinated contrast injection, and radiation exposure. With the goal of avoiding DSA drawbacks, several MR angiography techniques have been tested to follow intracranial aneurysms. 3D-TOF-MRA and contrast-enhanced MRA (CE-MRA) at 3T are appropriate techniques for the follow-up of coiled aneurysms but have some limitations for the aneurysms treated with stents or flow diverters.^17–23 Because the WEB is a relatively new device, the value of 3D-TOF-MRA and CE-MRA for the follow-up of WEB-treated intracranial aneurysms has been evaluated in a small number of patients at 1.5T.²⁴The aim of this single-center prospective study was to assess the diagnostic accuracy of 3D-TOF-MRA and CE-MRA at 3T against DSA, as the criterion standard, for the evaluation of aneurysm occlusion after WEB treatment.     

Stent-assisted coiling of intracranial bifurcation aneurysms leads to immediate and delayed intracranial vascular angle remodeling

BACKGROUND AND PURPOSE:Wide-neck bifurcating aneurysms are increasingly treated with intracranial stent-assisted coiling by using shape-memory alloy microstents. We sought to investigate the short- and long-term effects of intracranial stent implantation on the geometry and angular conformation of the stent-coiled vascular bifurcation.MATERIALS AND METHODS:Thirty patients underwent stent-mediated coiling for 31 bifurcation aneurysms by using 31 self-expanding Neuroform (n = 14) and Enterprise (n = 17) stents (17 women; mean age, 56 years). The angle (δ) between the stented mother and daughter vessels at the bifurcation was measured by using multiplanar imaging of reconstructed rotational conventional angiography volumes and was compared by using matched-pair statistics. Neuroform and Enterprise longitudinal stent stiffness was measured in vitro at an increasing bending angle θ (θ = 180°− δ).RESULTS:Stent deployment increased the bifurcation angle δ from 101.5° to 119.8° postprocedurally and to 137.3° (P < .0001) at latest follow-up, resulting in effective straightening; the angular remodeling was greater in distal-versus-proximal arteries (anterior cerebral > MCA > BA > ICA), inversely proportional to mother-vessel diameter and proportional to pretreatment bending angle θ. At follow-up, angle δ continued to significantly expand, with remodeling being greater in the early period (1–6 versus >7 months) and more pronounced with the longitudinally stiffer closed-cell Enterprise compared with the open-cell Neuroform stent.CONCLUSIONS:Stent placement across bifurcation aneurysms leads to a significant biphasic angular remodeling related to stent type and vessel caliber, altering morphology to mimic sidewall lesions, a phenomenon needing consideration during procedural planning. Future work is needed to uncover the hemodynamic implications of this structural change and any possible effect on aneurysm-recurrence rates.

The stent-assisted coiling technique has gained increased utility in the endovascular treatment of wide-neck cerebral aneurysms that pose a challenge to conventional coiling because of poor dome-to-neck ratio.^1–7 The deployment of an intracranial microstent serves as a metal scaffold to prevent coil herniation through the neck of these wide-neck aneurysms and can also increase the treatment−coil packing attenuation.⁸ Since the introduction of stent-placement techniques for aneurysm treatment, significant progress has led to their use in a variety of methods, including sole stent placement for side wall or fusiform aneurysms,^4,9–11 “kissing” stents for wide fusiform aneurysms,¹² overlapping stents with or without coiling for ruptured dissecting aneurysms or small wide-neck aneurysms,^13,14 stents deployed in “Y”^15,16 or “waffle-cone”¹⁷ configurations, and transcirculation¹⁸ horizontal stent placement across the neck of a bifurcation aneurysm.^19,20Despite the availability of intracranial stent placement for >7 years, there remains little information regarding the effect of the deployment of self-expanding microstents (Neuroform, Boston Scientific, Natick, Massachusetts; Enterprise, Cordis, Miami Lakes, Florida) on cerebral vascular architecture. In-stent stenosis has been documented as a low-risk phenomenon in certain cases.²¹ Data on other structural changes following the stent-mediated coiling procedure remain sparse. Little information exists on the effect of the deployment of self-expanding stents across vascular bifurcations during stent-mediated coiling of bifurcation aneurysms and specifically on immediate and long-term bifurcation angular configurations. Bifurcation aneurysm stent-mediated coiling with a single stent is a multistep process. It involves the deployment of the intracranial stent across the bifurcation over the aneurysm neck from the mother vessel to 1 of the daughter vessels that is most likely to result in best neck coverage and facilitate aneurysm coiling with the least chance of coil herniation or impingement of the other daughter vessel. Recent work has suggested an important contribution to vessel angle with respect to aneurysm inflow.^22,23 After noting striking cerebral vascular deformation with stent placement in a preliminary analysis,²⁴ we sought to investigate the geometric consequences of intracranial stent coiling at bifurcations harboring aneurysms.     

Temporal evolution of susceptibility artifacts from coiled aneurysms on MR angiography: an in vivo canine study

BACKGROUND AND PURPOSE:Intracranial aneurysms treated by coiling have a risk for recurrence, requiring surveillance imaging. MRA has emerged as an attractive technique for postcoiling aneurysm imaging. Previous research has evaluated MR imaging artifacts of the coil mass in vitro. Our aim in this study was to evaluate MR imaging artifacts of coiled aneurysms in vivo with time.MATERIALS AND METHODS:Four sidewall aneurysms were created in each of 4 dogs. Aneurysms were embolized receiving only 1 type of coils. After embolization, the animals were transferred to MR imaging, which included axial 3D TOF MRA (TEs, 3.5, 5, and 6.9 ms), phase-contrast MRA, and coronal CE-MRA. MR imaging studies were repeated at 1, 4, 6, 8, 14, and 28 weeks. We calculated an OEF: OEF = V_A/V_CM, where the numerator represents the volume of the MR imaging artifacts and the denominator is the true volume of the coil mass measured by 3D RA.RESULTS:OEFs were largest immediately after embolization and showed a gradual decay until approximately 4 weeks, when there was stabilization of the size of the artifacts. By 4 weeks, there was mild coil compaction (average coil mass volume decrease of 7.8%); however, the OEFs decreased by 25% after 4 weeks (P < .001).CONCLUSIONS:MR imaging susceptibility artifacts change with time, being maximal in the postembolization setting and decaying until 4 weeks. The clinical implications of this study are that baseline MRA for comparison with future imaging should be acquired at a minimum of 1 week after the procedure.

Endovascular procedures are increasingly being used for the treatment of intracranial aneurysms. In this setting, coiling has evolved with new devices and technologies achieving better outcomes.¹ Nevertheless, recurrence due to coil compaction and/or aneurysm regrowth still remains a limitation of the method, and long-term imaging follow-up is a requirement.^2–5DSA is an invasive procedure that involves risks for permanent neurologic deficits ranging from 0% to 5.7%^6–8 and also exposure to ionizing radiation, which has been recently regarded with increasing concern, especially in this subset of patients who receive high doses from diagnostic work-up and treatment procedures.⁹ CTA is very effective in detecting aneurysms; however, the beam-hardening and streak artifacts limit its use as a posttreatment imaging method.¹⁰ Recently, MRA has become a viable option for noninvasive follow-up. 3D-TOF and CE-MRA offer a noninvasive high-resolution alternative to DSA for postembolization surveillance due to its high flow sensitivity and lack of ionizing radiation. Other advantages include comfort, convenience for the patient, and cost reduction.^10–13 Often, a baseline MRA within 1 week of coiling is acquired for future comparison. This timeframe is presumably based on the hospital admission of the patient.With MR imaging, it is possible to obtain information on aneurysm residual patency or recanalization and parent vessel abnormalities. The coil mass produces magnetic susceptibility or blooming artifacts that can obscure visualization of these parameters and subsequent interpretation. Shorter TE techniques can be used to reduce susceptibility-induced signal-intensity loss from the coil mass.^14,15 Previous research into MR imaging artifacts has been conducted mostly in vitro,^16–19 but the dynamic characteristics of a functional vascular system cannot be fully simulated. Plastic or vascular replicas have little MR imaging signal intensity compared with the arterial wall. Most important, the signal intensity from the aneurysm healing process—the acute thrombosis and thrombus organization—are not evaluated. Therefore, implantation and imaging of these devices in animal models are desirable. Our aim in this study was to evaluate the MR imaging artifacts of the coiled aneurysms in an animal model in different MRA sequences, with time.     

The FRED Flow-Diverter Stent for Intracranial Aneurysms: Clinical Study to Assess Safety and Efficacy

BACKGROUND AND PURPOSE:Flow-diverter stents are emerging for the endovascular treatment of difficult-to-treat or otherwise untreatable cerebral aneurysms (wide-neck, fusiform, dissecting, blisterlike, or giant). We assessed the clinical safety and efficacy of the Flow-Redirection Endoluminal Device.MATERIALS AND METHODS:This was an institutional review board–approved single-center observational clinical study in 29 patients with 34 aneurysms elected to be treated by endovascular intervention. After providing informed consent, patients were included according to the following criteria: aneurysm fundus-to-neck ratio <2 or neck diameter >4 mm, fusiform, dissecting, or giant aneurysms. The primary end point for clinical safety was the absence of death, absence of major or minor stroke, and absence of transient ischemic attack. The primary end point for treatment efficacy was complete angiographic occlusion according to the O''Kelly Marotta grading scale immediately after the procedure and at follow-up after 3 and 6 months (O''Kelly Marotta D: complete occlusion).RESULTS:The Flow-Redirection Intraluminal Device deployment was technically successful in all cases. In 26/29 (89%) of patients, the primary end point of safety was reached; in the 3 remaining patients, 1 disabling ischemic stroke and 2 minor strokes with complete recovery at follow-up were observed. Angiographic (DSA and MRA) and clinical follow-up were available after 3 months in 29/29 (100%) and after 6 months in 25/29 (86%) patients (after 6 months, only MRA follow-up was performed according to our study protocol and institutional standard). At 3-month follow-up, complete occlusion was reached in 19/34 aneurysms (O''Kelly Marotta D: 19/34; 56%). At 6-month follow-up, aneurysm occlusion was complete in 22/30 aneurysms (O''Kelly Marotta D: 22/30; 73%).CONCLUSIONS:Deployment of the Flow-Redirection Intraluminal Device flow-diverter stent is safe and effective in the treatment of difficult-to-treat or otherwise untreatable intracranial aneurysms.

Endovascular treatment of intracranial aneurysms by coiling has become an accepted alternative to surgical clipping, with increasing evidence for lower morbidity and mortality rates, especially in clinical equipoise.^1–3 However, especially in wide-neck, fusiform, dissecting, and giant aneurysms, incomplete coiling and reperfusion are still a major limitation preventing stable long-term occlusion. Aneurysm recanalization and/or neck remnants may be observed despite further refinement in coil technology such as coated platinum coils⁴ and/or procedural modification such as the balloon-remodeling technique⁵ or stent-assisted coil embolization.⁶The development of flow-diverter (FD) stents has offered the potential of aneurysm occlusion through thrombosis triggered by the disruption of flow into the aneurysm sac.^7–16 As a key element of construction, these stents have a braided mesh with a densely covered surface. Once the FD is expanded to cover the aneurysm neck, thrombosis is induced by stasis of flow within the aneurysmal sac. The porosity of the FD mesh and the pressure gradient between parent and smaller adjacent branch vessels preserve flow and patency of the latter even if covered. The Flow-Redirection Endoluminal Device (FRED; MicroVention, Tustin, California) is a new generation of FDs for reconstruction of the parent artery and aneurysm occlusion. Its unique dual-layer design composed of a low-porosity inner mesh and a high-porosity outer stent may provide potential advantages over other available FDs in safe deliverability and effective occlusion of the target lesion. We report our analysis of the clinical safety and efficacy of the FRED in 29 patients with 34 aneurysms.     

Preliminary Experience with Stent-Assisted Coiling of Aneurysms Arising from Small (<2.5 mm) Cerebral Vessels Using The Low-Profile Visualized Intraluminal Support Device

BACKGROUND AND PURPOSE:The Low-Profile Visualized Intraluminal Support (LVIS) stent is a new device recently introduced for the treatment of wide-neck intracranial aneurysms. This single-center study presents the authors'' preliminary experience using the LVIS stent to treat saccular aneurysms with parent arteries smaller than 2.5 mm.MATERIALS AND METHODS:Aneurysms with a LVIS stent used in a small parent vessel (<2.5 mm in diameter) between October 2014 and April 2016 were included. Procedure-related complications, angiographic results, clinical outcomes, and midterm follow-up data were analyzed retrospectively.RESULTS:A total of 22 patients was studied, including 5 ruptured and 17 unruptured aneurysms. Most of the aneurysms were located in the anterior circulation (90.9%). Stent placement in the parent arteries measuring 1.7–2.4 mm in diameter (mean, 2.1 mm) was successful in 100% of cases. Procedure-related complication developed in 1 patient (4.5%) who presented with aneurysm rupture. No permanent morbidity and mortality occurred. Immediate angiographic outcome showed complete occlusion in 8 aneurysms (36.4%), neck residual in 8 (36.4%), and residual aneurysm in 6 (27.3%). All patients underwent angiographic follow-up at a mean of 8.3 months, which revealed complete occlusion in 18 (81.8%) patients, neck remnant in 3 (13.6%), and residual sac in 1 (4.5%). No recanalization of the target aneurysm was observed. There was 1 case with asymptomatic in-stent stenosis.CONCLUSIONS:Our preliminary results show that the deployment of LVIS stents in small vessels is feasible, safe, and effective in the midterm. Larger studies with long-term follow-up are needed to validate our promising results.

The introduction of stent devices has greatly advanced the endovascular treatment options of intracranial aneurysms. Many aneurysms that had been previously considered untreatable because of their morphology, including those with unfavorable dome-to-neck ratios and/or location, are now amenable to coiling with the use of stents.^1,2 However, the use of stents for treating wide-neck distal intracranial aneurysms with small parent vessels remains challenging. Several previous studies reported relatively high rates of periprocedural thromboembolic events and in-stent stenosis.^3–11The Low-Profile Visualized Intraluminal Support (LVIS) device (MicroVention, Tustin, California), a new device offering an option between conventional stents and flow diverters, is designed for the stent-assisted coil embolization of wide-neck intracranial aneurysms. There is an increasing number of publications on the use of the LVIS device.^12–16 However, to our knowledge, no studies to date have specifically investigated the placement of the LVIS device in small vessels. Hence, we conducted this retrospective study to examine the LVIS device in terms of its safety, deployment feasibility, and treatment effectiveness in intracranial aneurysms with parent vessels measuring <2.5 mm in diameter.     

Complications in Stent-Assisted Endovascular Therapy of Ruptured Intracranial Aneurysms and Relevance to Antiplatelet Administration: A Systematic Review

BACKGROUND AND PURPOSE:Despite the increasing use of stent-assisted coiling for ruptured intracranial aneurysms, there is little consensus regarding the appropriate antiplatelet administration for this. The objectives of this systematic review were to provide an overview of complications and their association with the method of antiplatelet administration in stent-assisted coiling for ruptured intracranial aneurysms.MATERIALS AND METHODS:A comprehensive search of the literature in the data bases was conducted to identify studies reporting complications of stent-assisted coiling for ruptured intracranial aneurysms. The pooled event rate of preprocedural thromboembolisms, hemorrhages, and mortality was estimated from the selected studies. Subgroup analyses were performed by the method of antiplatelet administration (pre-, postprocedural, and modified). Meta-analysis was conducted to compare periprocedural complications and mortality between ruptured intracranial aneurysms and unruptured intracranial aneurysms.RESULTS:Of the 8476 studies identified, 33 with 1090 patients were included. The event rates of thromboembolism and intra- and postprocedural hemorrhage were 11.2% (95% CI, 9.2%–13.6%), 5.4% (95% CI, 4.1%–7.2%), and 3.6% (95% CI, 2.6%–5.1%), respectively. Subgroup analyses of thromboembolism showed a statistically significant difference between groups (P < .05). In the preprocedural and modified antiplatelet groups, the risk for thromboembolism in stent-assisted coiling for ruptured intracranial aneurysm was not significantly different from that for unruptured intracranial aneurysm, though this risk of the postprocedural antiplatelet group was significantly higher in ruptured intracranial aneurysms than in unruptured intracranial aneurysms.CONCLUSIONS:On the basis of current evidence, complications of stent-assisted coiling for ruptured intracranial aneurysm may be affected by the method of antiplatelet administration.

Aneurysmal neck remodeling with stents has recently emerged as an effective treatment option. This method is beneficial for treating aneurysms with wide necks or for situations in which coils unexpectedly herniate into the parent vessel, requiring rescue with a device that can reconstrain the coil within the lesion.¹ Currently, various stents specialized for aneurysmal neck remodeling are used during endovascular treatment of intracranial aneurysms. However, physicians are often reluctant to apply stents to acutely ruptured aneurysms due to the necessity of antiplatelet medications. During implantation of stents within an intracranial artery, antiplatelet agents should be administrated and maintained postoperatively to prevent in-stent thrombosis and subsequent ischemic events.² In the setting of acutely ruptured aneurysms, antiplatelet medications may lead to complications such as intraprocedural rebleeding, the need for a ventriculostomy, co-occurrence of an intraparenchymal hematoma, and a high likelihood of future invasive procedures.^3–7Despite the chance of complications, administration of antiplatelet agents is an important element of management when using an intracranial stent, regardless of the presence of an acute aneurysm rupture. The type and/or method of antiplatelet agent might affect the periprocedural complication rate of endovascular aneurysm treatment.^8,9 Despite many previous studies of stent-assisted aneurysm management, no published recommendations or large randomized clinical trials provide a consensus as to the appropriate method of antiplatelet medication in stent-assisted endovascular treatment for ruptured intracranial aneurysms (RIAs). The medication method usually varied depending on the institution or the rationales of clinicians in most published case series. Some review articles suggested a higher risk of complications in endovascular therapy for acutely ruptured aneurysms.^3,10,11 However, these reviews did not analyze independent factors affecting the risk of complications in stent-assisted coiling for RIA, including the application of antiplatelet agents.The purposes of this systematic review were to calculate the accumulated complication risk during stent-assisted coiling for RIA and to assess whether the risk of complications would be affected by the method of antiplatelet administration. This information will guide selection of safer antiplatelet administration for stent-assisted coiling of RIA.     

LEO Baby Stent Use following Balloon-Assisted Coiling: Single- and Dual-Stent Technique—Immediate and Midterm Results of 29 Consecutive Patients

BACKGROUND AND PURPOSE:We report our preliminary results in terms of safety and efficacy in using the low-profile LEO Baby stent for the treatment of large-neck and complex intracranial aneurysms with balloon-then-stent-assisted coiling and single- or dual-stent-assisted coiling.MATERIALS AND METHODS:Clinical and radiologic data of all consecutive patients treated at our institution from September 2012 to October 2013 for an intracranial aneurysm by using a LEO Baby stent were retrospectively analyzed. Immediate and midterm clinical and anatomic follow-up of each patient is reported.RESULTS:Twenty-nine patients with 29 aneurysms were treated with LEO Baby stents at our institution. The mean age of patients was 48 years; 20 patients were women (71%). One patient was treated in the acute phase of a subarachnoid hemorrhage. In 8 procedures, a double-lumen-catheter balloon was used for balloon-then-stent-assisted coiling. In 3 cases, a LEO Baby stent was used in a Y-, T-, and telescopic dual-stent configuration. In 18 cases, a single LEO Baby stent was used. In 2 cases, technical failure to deploy the stent resulted in acute parent artery thrombosis. In 3 further cases, thromboembolic complications occurred intraoperatively. MR imaging and angiographic midterm follow-up showed complete aneurysm occlusion for 96% of the followed patients (27/29). Clinical outcome was favorable for all patients followed up.CONCLUSIONS:Results obtained in our study by using the LEO Baby stent for balloon-then-stent and single- or dual-stent-assisted coiling of complex and distally located intracranial aneurysms are encouraging. Incomplete or inadequate opening of the device is a potential cause of laminar blood flow alteration and thrombus formation.

The results of endovascular treatment of wide-neck and complex intracranial aneurysms have improved following the introduction of balloon remodeling and stent-assisted coiling.^1–6 Theoretically, intracranial stents act as a scaffold to maintain the coil mass within the aneurysmal sac, allowing higher packing density. This leads to a reduction of the blood flow into the aneurysmal sac while diverting it toward the parent vessel and provides support for the neointima growth across the neck.^7,8 The LEO Baby stent (LBS; Balt Extrusion, Montmorency, France) is a new self-expandable stent with 16 nitinol wires (2 of which are radiopaque). This braided microstent can be delivered through a 0.0165-inch microcatheter or a dual-lumen balloon catheter system (Scepter XC; MicroVention, Tustin, California) and deployed within arteries with diameters ranging from 1.5 to 3.1 mm. In the present study, we report our preliminary results in terms of safety and efficacy by using the LBS for the treatment of large-neck and complex intracranial aneurysms with balloon-then-stent-assisted coiling and single- or dual-stent-assisted coiling.     

Diffusion-Weighted Imaging–Detected Ischemic Lesions following Endovascular Treatment of Cerebral Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE:Endovascular treatment of intracranial aneurysms is associated with the risk of thromboembolic ischemic complications. Many of these events are asymptomatic and identified only on diffusion-weighted imaging. We performed a systematic review and meta-analysis to study the incidence of DWI positive for thromboembolic events following endovascular treatment of intracranial aneurysms.MATERIALS AND METHODS:A comprehensive literature search identified studies published between 2000 and April 2016 that reported postprocedural DWI findings in patients undergoing endovascular treatment of intracranial aneurysms. The primary outcome was the incidence of DWI positive for thromboembolic events. We examined outcomes by treatment type, sex, and aneurysm characteristics. Meta-analyses were performed by using a random-effects model.RESULTS:Twenty-two studies with 2148 patients and 2268 aneurysms were included. The overall incidence of DWI positive for thromboembolic events following endovascular treatment was 49% (95% CI, 42%–56%). Treatment with flow diversion trended toward a higher rate of DWI positive for lesions than coiling alone (67%; 95% CI, 46%–85%; versus 45%; 95% CI, 33%–56%; P = .07). There was no difference between patients treated with coiling alone and those treated with balloon-assisted (44%; 95% CI, 29%–60%; P = .99) or stent-assisted (43%; 95% CI, 24%–63%; P = .89) coiling. Sex, aneurysm rupture status, location, and size were not associated with the rate of DWI positive for lesions.CONCLUSIONS:One in 2 patients may have infarcts on DWI following endovascular treatment of intracranial aneurysms. There is a trend toward a higher incidence of DWI-positive lesions following treatment with flow diversion compared with coiling. Patient demographics and aneurysm characteristics were not associated with DWI-positive thromboembolic events.

Coil embolization and flow diversion have proved highly efficacious options for the endovascular treatment of intracranial aneurysms. However, both techniques are associated with potential periprocedural complications, including aneurysm rupture, transient ischemic attacks, and ischemic stroke. Small, silent infarcts caused by thromboemboli are often seen on postprocedural diffusion-weighted imaging. While many of these lesions remain ostensibly asymptomatic, the long-term effects of such tiny infarcts remain unclear.^1–3Previous studies have reported that the rate of ischemic lesions on postoperative DWI ranges from 10% to 77% following coil embolization^4–15 and 51% to 63% following therapy with flow diversion.^16–19 However, baseline clinical and angiographic risk factors for postoperative DWI lesions, to our knowledge, have not been fully elucidated previously. We performed a systematic review and meta-analysis for the following: 1) to determine the overall incidence of perioperative infarcts on DWI in patients undergoing endovascular treatment of intracranial aneurysms; and 2) to demonstrate the relationship between treatment type, patient demographics, and aneurysm characteristics with postoperative infarcts on DWI.     

Symptom Differences and Pretreatment Asymptomatic Interval Affect Outcomes of Stenting for Intracranial Atherosclerotic Disease

BACKGROUND AND PURPOSE:Different types of symptomatic intracranial stenosis may respond differently to interventional therapy. We investigated symptomatic and pathophysiologic factors that may influence clinical outcomes of patients with intracranial atherosclerotic disease who were treated with stents.MATERIALS AND METHODS:A retrospective analysis was performed of patients treated with stents for intracranial atherosclerosis at 4 centers. Patient demographics and comorbidities, lesion features, treatment features, and preprocedural and postprocedural functional status were noted. χ² univariate and multivariate logistic regression analysis was performed to assess technical results and clinical outcomes.RESULTS:One hundred forty-two lesions in 131 patients were analyzed. Lesions causing hypoperfusion ischemic symptoms were associated with fewer strokes by last contact [χ² (1, n = 63) = 5.41, P = .019]. Nonhypoperfusion lesions causing symptoms during the 14 days before treatment had more strokes by last contact [χ² (1, n = 136), 4.21, P = .047]. Patients treated with stents designed for intracranial deployment were more likely to have had a stroke by last contact (OR, 4.63; P = .032), and patients treated with percutaneous balloon angioplasty in addition to deployment of a self-expanding stent were less likely to be stroke free at point of last contact (OR, 0.60; P = .034).CONCLUSIONS:More favorable outcomes may occur after stent placement for lesions causing hypoperfusion symptoms and when delaying stent placement 7–14 days after most recent symptoms for lesions suspected to cause embolic disease or perforator ischemia. Angioplasty performed in addition to self-expanding stent deployment may lead to worse outcomes, as may use of self-expanding stents rather than balloon-mounted stents.

Intracranial atherosclerotic disease (ICAD) causes considerable morbidity and mortality, accounting for up to one-third of ischemic strokes in some series, particularly in certain populations.^1–3 Some lesions prove recalcitrant to first-line medical management, and, in recent decades, endovascular treatments have emerged and evolved as complementary therapies.^4,5 Early series demonstrated technical feasibility and acceptable safety for percutaneous transluminal angioplasty (PTA) and then stent placement of lesions in ICAD.^5–17 Initially, intracranial procedures were performed with devices designed and approved for coronary interventions, with subsequent release of angioplasty balloons specifically engineered for intracranial use.^5,12,17–33 In 2005, the Wingspan stent system with Gateway PTA balloon catheter (Stryker, Kalamazoo, Michigan) became the first stent approved for treatment of ICAD in the United States.^{5,12,18–22,25,34} Numerous studies reported progressively improved outcomes and low complication rates, but randomized data proving efficacy were lacking.^{5,12,18,20,24,25,35,36} In 2011, enrollment in the first randomized, controlled trial to evaluate stent placement versus medical management of ICAD, the Stent placement and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial, was halted early due to high complication rates in the stent placement group as compared with the medical management group.⁴The results of SAMMPRIS have elicited strong responses from both proponents and detractors of stent placement, with clinical decisions now changing.⁵ This current study retrospectively analyzes results of stent placement procedures performed for ICAD at 4 centers, with attention given to factors not specifically assessed in SAMMPRIS that may help guide further investigations of endovascular ICAD management.     

Vascular Wall Imaging of Unruptured Cerebral Aneurysms with a Hybrid of Opposite-Contrast MR Angiography

BACKGROUND AND PURPOSE:Inflammation and degeneration of the intracranial saccular aneurysm wall play a major role in aneurysm formation, development and subsequent rupture. The aim of this study was to characterize the walls of unruptured intracranial aneurysms by using a hybrid of opposite-contrast MRA at 3T.MATERIALS AND METHODS:Fourteen consecutive patients with 17 unruptured intracranial aneurysms who initially underwent clipping surgery were prospectively evaluated. All aneurysms were scanned preoperatively by using a hybrid of opposite-contrast MRA in 3T high-resolution MR imaging. We classified intraoperative findings of atherosclerotic plaques in the aneurysms into 3 grades: grade A (major plaques), grade B (minor plaques), and grade C (no plaques). The contrast ratio of the high-intensity area was also measured relative to the background low-intensity area inside the carotid artery.RESULTS:Findings from preoperative plaque imaging of the aneurysm corresponded to the intraoperative findings in 15 of 16 aneurysms (excluding 1 that was impossible to visualize in its entirety due to anatomic reasons). Overall sensitivity and specificity of the hybrid of opposite-contrast MRA were 88.9% and 100%, respectively. During the operation, 4 aneurysms were classified as grade A; 5, as grade B; and 7, as grade C. The means of the contrast ratio for grades A, B, and C were 0.72 ± 0.03, 0.34 ± 0.30, and −0.02 ± 0.09, respectively.CONCLUSIONS:The hybrid of opposite-contrast MRA can detect visible atherosclerotic plaques in the unruptured aneurysm wall, and the contrast ratio in intracranial aneurysms correlated with their presence and extent. A study including a larger series is needed to validate the diagnostic potential of this imaging technique.

Intracranial aneurysms are common vascular lesions, often consisting of a saccular dilation of a cerebral artery vessel. The prevalence of intracranial aneurysms in the general population is estimated between 2.5% and 5%.^1,2 Aneurysmal rupture occurs with a 1% risk per year, depending on the size, location, and morphometry of the aneurysm, and leads to subarachnoid hemorrhage with associated high morbidity and mortality rates.^1,2 Intracranial aneurysms with an estimated high risk of rupture undergo management via a surgical or endovascular approach, depending on the specific risks of treatment.^3,4 Therefore, it is important to accurately assess the risk of aneurysmal rupture.The pathogenesis of intracranial aneurysms and their natural history are not well-understood. Histopathologic studies have shown that the infiltration of inflammatory cells and the degeneration of the aneurysm wall with atherosclerosis correlates with the formation, development, and rupture risk of cerebral aneurysms.^5–9 However, characterization of the aneurysm wall is limited by imaging data quality and the need to harvest surgical specimens.In this regard, the characteristics of high-field-strength MR imaging, which has a favorable SNR and changes in relaxation time and susceptibility, can depict the intracranial vessel walls and their pathologies, including small vessels with atherosclerosis.^10,11The hybrid of opposite-contrast MR angiography (HOP-MRA) used in this study is a modern technique that combines the advantages of 3D TOF MRA and flow-sensitive black-blood (FSBB) MRA.¹² The clinical efficacy of this technique was established to improve the visualization of peripheral vessels.^13,14 Theoretically, tissue with shorter T1 and T2* introduces high signal in FSBB of HOP-MRA, which demonstrates atherosclerotic plaques, including fat, as high-signal-intensity areas and demonstrates the blood space as low-signal-intensity areas in intracranial aneurysms.¹² The strength of this technique is the dual-echo 3D gradient-echo sequence, which enables a shorter imaging time and minimization of misregistration. The present study investigated the utility of HOP-MRA at 3T for the characterization of visible atherosclerotic plaques in intracranial aneurysms by using subtraction between TOF and FSBB imaging.     

Association between Postprocedural Infarction and Antiplatelet Drug Resistance after Coiling for Unruptured Intracranial Aneurysms

BACKGROUND AND PURPOSE:Procedure-related thromboembolism is a major limitation of coil embolization, but the relationship between thromboembolic infarction and antiplatelet resistance is poorly understood. The purpose of this study was to verify the association between immediate postprocedural thromboembolic infarction and antiplatelet drug resistance after endovascular coil embolization for unruptured intracranial aneurysm.MATERIALS AND METHODS:This study included 338 aneurysms between October 2012 and March 2015. All patients underwent postprocedural MR imaging within 48 hours after endovascular coil embolization. Antiplatelet drug resistance was checked a day before the procedure by using the VerifyNow system. Abnormal antiplatelet response was defined as >550 aspirin response units and >240 P2Y12 receptor reaction units. In addition, we explored the optimal cutoff values of aspirin response units and P2Y12 receptor reaction units. The primary outcome was radiologic infarction based on postprocedural MR imaging.RESULTS:Among 338 unruptured intracranial aneurysms, 134 (39.6%) showed diffusion-positive lesions on postprocedural MR imaging, and 32 (9.5%) and 105 (31.1%) had abnormal aspirin response unit and P2Y12 receptor reaction unit values, respectively. Radiologic infarction was associated with advanced age (65 years and older, P = .024) only with defined abnormal antiplatelet response (aspirin response units ≥ 550, P2Y12 receptor reaction units ≥ 240). P2Y12 receptor reaction unit values in the top 10th percentile (>294) were associated with radiologic infarction (P = .003). With this cutoff value, age (adjusted odds ratio, 2.29; 95% confidence interval, 1.28–4.08), P2Y12 receptor reaction units (>294; OR, 3.43; 95% CI, 1.53–7.71), and hyperlipidemia (OR, 2.05; 95% CI, 1.04–4.02) were associated with radiologic infarction in multivariate analysis.CONCLUSIONS:Radiologic infarction after coiling for unruptured aneurysm was closely associated with age. Only very high P2Y12 receptor reaction unit values (>294) predicted postprocedural infarction. Further controlled studies are needed to determine the precise cutoff values, which could provide information regarding the optimal antiplatelet regimen for aneurysm coiling.

Endovascular coil embolization is a well-established treatment method for intracranial aneurysms. Recent evidence suggests that this procedure can be considered a first-line treatment for both ruptured and unruptured intracranial aneurysms.^1,2 However, endovascular coil embolization still has major drawbacks, including procedural rupture, thromboembolic complications, and durability issues. Among these shortcomings, thromboembolism is the most common problem.^3–5 To reduce thromboembolic complications, many studies investigated the association between thromboembolism and aneurysm and/or patient factors.^5–8 Previous studies have demonstrated that 30%–60% of endovascular coil embolizations for unruptured aneurysms show ischemic lesions on postprocedural diffusion-weighted images. Although most of the lesions seem to be benign, some could result in permanent neurologic sequelae. Recent studies demonstrated that antiplatelet resistance was associated with ischemic complications after coil embolization and that drug adjustment could lower the risk.^9,10 Still, these results are controversial, and the association between antiplatelet drug resistance and diffusion lesions has not yet been fully elucidated.^11,12Therefore, the purpose of this study was to verify the association between thromboembolic infarction and antiplatelet drug resistance after endovascular coil embolization for unruptured intracranial aneurysms. We also explored other risk factors for thromboembolic complications.