Delayed ipsilateral parenchymal hemorrhage following flow diversion for the treatment of anterior circulation aneurysms

Clinically Silent Microinfarct Incidence and Risk Factors After Treatment of Unruptured Intracranial Aneurysms with Hydrophilic Polymer-Coated Flow Diverters

PURPOSE

Although flow diverters (FDs) revolutionized the treatment of unruptured intracranial aneurysms (UIAs), clinically silent microinfarcts (SMs) are consistently detected in postprocedural diffusion-weighted imaging (DWI), and their clinical consequences remain unknown. This study examined the incidence of, and factors associated with, SM development after the use of two surface-modified FDs: the p48MW-HPC and p64MW-HPC.

METHODS

A non-concurrent cohort study was conducted in 404 consecutive patients with UIAs treated with these two FDs between January 2020 and July 2023. The primary endpoint was the number of asymptomatic DWI lesions within 72 h after the procedure.

RESULTS

SMs were detected in 58.2% of the cases, and ≥ 20 lesions were identified in 7.2% of cases. Multivariate analysis revealed that the use of two specific types of microcatheters-Prowler Select Plus (P < 0.001; IRR, 3.2) and RapidTransit (P = 0.001; IRR, 2.2)-and difficulty in microcatheter navigation to the target vessel (P = 0.039; IRR, 1.8) were significantly associated with greater numbers of lesions. After exclusion of outlier cases, these devices remained associated with a significant 2‑ to 3‑fold increase in SMs. Diabetes was associated with fewer SMs (P = 0.024; IRR, 0.5), although this association disappeared after exclusion of outlier cases.

CONCLUSION

The postprocedural incidence of SMs associated with hydrophilic polymer-coated FDs was similar to that previously reported. Interestingly, the main factor contributing to this phenomenon was the use of certain microcatheters. Careful device selection is crucial, and further research is needed to improve the safety of neurovascular interventions.

Intracranial hemorrhagic events associated with flow diversion treatment: a retrospective analysis from a single academic institution

Intracranial hemorrhages are highly concerning but underreported complications related to flow diversion (FD) treatment of intracranial aneurysms. Herein, we aimed to characterize these complications and the factors influencing their occurrence. We retrospectively reviewed patients treated with FD from 2013 to 2023 at a single U.S. institution, analyzing aneurysm characteristics, comorbidities, antiplatelet and anticoagulation use, and hemorrhage imaging features. Risk factors for intraparenchymal hemorrhages (IPHs) were assessed with univariate analysis. There were 622 patients harboring 788 aneurysms treated in 690 procedures during the study period. Within 7 months of follow-up, 15 intracranial hemorrhages were identified (2.2%): 2 acute subdural hematomas (SDH), 7 IPH, 1 intraventricular hemorrhage (IVH), and 5 subarachnoid hemorrhages (SAH), most of which presented within the first 24 h after initial treatment. Patients experiencing hemorrhages exhibited lower rates of functional independence (mRS ≤ 2) compared to those without hemorrhage (66.7% vs. 93.3%; p < 0.01). IPHs were slightly higher in patients receiving aspirin-ticagrelor (1.2%) compared to those on aspirin-clopidogrel (0.9%) or aspirin-prasugrel (0.0%). A univariate logistic regression model demonstrated an aneurysmal diameter ≥ 12 mm (OR = 8.98; 95% CI = 1.98-16.03) and aneurysms with prior treatment (OR = 7.20; 95% CI = 1.59-32.60) as factors influencing IPHs after treatment. The incidence of hemorrhage decreased over the time interval of study. Intracranial hemorrhages related to FD are rare but highly morbid complications. Treatments involving larger aneurysms and those with prior interventions are associated with a higher risk of IPHs.

Two Patients With Ipsilateral Cerebellar Hemorrhage After Superficial Temporal Artery-Middle Cerebral Artery Bypass Grafting

OBJECTIVE

To summarize the clinical experience of ipsilateral cerebellar hemorrhage after superficial temporal artery-middle cerebral artery bypass surgery.

METHODS

The clinical data of 2 patients with cerebellar hemorrhage after superficial temporal artery-middle cerebral artery bypass grafting were retrospectively collected, including 1 case with left cerebellar hemorrhage after left cerebral artery bypass grafting and 1 case with right cerebellar hemorrhage after right cerebral artery bypass grafting. The perioperative blood pressure, laboratory, and imaging data were analyzed.

RESULTS

All patients had a history of hypertension, and their perioperative blood pressure was stable. Low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were normal before the operation. Cerebral magnetic resonance imaging showed cerebral atherosclerosis and multiple ischemic cerebral infarcts. At 24 hours after surgery, the patients' continuous epidural low drainage was 260 mL and 160 mL, respectively. The amount of cerebellar bleeding was small, and no new sequelae were left after conservative treatment with drugs.

CONCLUSION

Cerebellar hemorrhage after superficial temporal artery-middle cerebral artery bypass grafting is related to perioperative blood pressure fluctuation, hemodynamic changes, hemorrhagic transformation of ischemic lesions, and excessive cerebrospinal fluid drainage. Maintaining stable blood pressure during the perioperative period and avoiding excessive and rapid loss of cerebrospinal fluid after operation can reduce the occurrence of this complication.

Endovascular treatment of distal anterior cerebral artery aneurysms using flow modulation devices: mid- and long-term results from a two-center study

Purpose

Flow-diverter (FD) stents have become an established treatment for intracranial aneurysms in recent years, but their use for aneurysms in distal cerebral vessels with small carrier vessel diameters remains controversial. This study describes the method and mid- and long-term outcomes of FD treatment of distal anterior cerebral artery aneurysms (DACAAs) at two neurointerventional centers, to elucidate this topic and provide more in-depth data.

Methods

Data for all patients at two neurointerventional centers who were treated with FDs for DACAAs in the pericallosal and supracallosal segment of the anterior cerebral artery were retrospectively analyzed. Data on periprocedural complications, and short-, mid- and long-term follow-up findings were recorded.

Results

Forty-one patients were eligible for inclusion in the study. Three FD models were used, one of which had an anti-thrombotic coating. Two periprocedural complications (5%) occurred but did not cause a change in the mRS. In the long-term follow-up, at 29 months and beyond, 83% of assessable patients showed complete occlusion of the aneurysms without new neurological deficits.

Conclusion

FDs are a safe and effective treatment approach for DACAAs. This study indicated a low risk of complications, and high closure rates in short-, mid- and long-term follow-up.

Classification and hemodynamic characteristics of delayed intracerebral hemorrhage following stent-assisted coil embolism in unruptured intracranial aneurysms

Background and objective

Stent-assisted coil (SAC) embolization is a commonly used endovascular treatment for unruptured intracranial aneurysms (UIAs) but can be associated with symptomatic delayed intracerebral hemorrhage (DICH). Our study aimed to investigate the hemodynamic risk factors contributing to DICH following SAC embolization and to establish a classification for DICH predicated on hemodynamic profiles.

Methods

This retrospective study included patients with UIAs located in the internal carotid artery (ICA) treated with SAC embolization at our institution from January 2021 to January 2022. We focused on eight patients who developed postoperative DICH and matched them with sixteen control patients without DICH. Using computational fluid dynamics, we evaluated the hemodynamic changes in distal arteries [terminal ICA, the anterior cerebral artery (ACA), and middle cerebral artery (MCA)] pre-and post-embolization. We distinguished DICH-related arteries from unrelated ones (ACA or MCA) and compared their hemodynamic alterations. An imbalance index, quantifying the differential in flow velocity changes between ACA and MCA post-embolization, was employed to gauge the flow distribution in distal arteries was used to assess distal arterial flow distribution.

Results

We identified two types of DICH based on postoperative flow alterations. In type 1, there was a significant lower in the mean velocity increase rate of the DICH-related artery compared to the unrelated artery (-47.25 ± 3.88% vs. 42.85 ± 3.03%; p < 0.001), whereas, in type 2, there was a notable higher (110.58 ± 9.42% vs. 17.60 ± 4.69%; p < 0.001). Both DICH types demonstrated a higher imbalance index than the control group, suggesting an association between altered distal arterial blood flow distribution and DICH occurrence.

Conclusion

DICH in SAC-treated UIAs can manifest as either a lower (type 1) or higher (type 2) in the rate of velocity in DICH-related arteries. An imbalance in distal arterial blood flow distribution appears to be a significant factor in DICH development.

Endoluminal flow diversion as a primary treatment strategy for pediatric traumatic intracranial aneurysms: a case-based review of literature

BACKGROUND

Traumatic intracranial aneurysms (TICAs) constitute a notable portion of pediatric intracranial aneurysms. Their unstable structure dictates a high incidence of rupture or mass effect from enlarging unruptured aneurysms, necessitating prompt diagnosis and treatment. TICAs often lack a true neck or are wide-necked, making them unsuitable for coil embolization and surgical clipping, and their fragile nature poses a risk of rupture during surgical and intrasaccular interventions. Endoluminal flow diverters (FD), deployed without requiring direct access to the aneurysmal sac, have emerged as an appealing sole treatment modality for TICAs. However, the clinical experience with this technique remains limited in the pediatric population.

METHOD

We describe the successful treatment of a paraclinoid TICA in a 4-year-old female using an endoluminal FD alone. Additionally, we conducted a literature review to assess the safety and effectiveness of this treatment modality in pediatric TICAs.

RESULTS

Endoluminal flow diversion led to complete aneurysm obliteration in our case, with no observed complication, at the 9-month follow-up. Our review of the previously reported pediatric TICAs managed by standalone flow diversion highlights this technique as safe, efficient, and promising as a sole treatment modality, particularly in the anterior circulation, with a high rate of persistent total obliteration and a low rate of complications. However, the requirement for long-term antiplatelet therapy with the possibility of frequent dose monitoring and adjustments warrants special attention when using endoluminal FDs. Until guidelines specifically addressing optimal antiplatelet therapy in children with intracranial FDs are formulated, adherence to existing protocols is imperative to avoid in-stent thrombosis.

CONCLUSION

Our literature review and personal experience indicate that endoluminal flow diversion can be a viable treatment approach for pediatric TICAs. However, prospective studies with extensive follow-ups are required to assess the durability of endoluminal FDs in treating pediatric TICAs, considering the long life expectancy of this demographic.

Quantitative Evaluation of Hemodynamic Changes After Multiple Intracranial Aneurysms Occlusion Using Computational Fluid Dynamics

OBJECTIVE

Multiple intracranial aneurysms (MIA) are prevalent. This study conducted hemodynamic calculations on MIA to analyze the effects of occlusion of the internal carotid artery (ICA) and middle cerebral artery (MCA) aneurysms on the hemodynamics of other arteries, as well as the issue of the treatment order for these aneurysms.

METHODS

The models of 9 patients with MIA were selected for the study. A computational fluid dynamics model combining 1-dimension and 3-dimension was used to obtain the vascular flow pattern and wall pressure.

RESULTS

There was increased pressure at the MCA and anterior cerebral artery (ACA) after occlusion of the aneurysm at the ICA. However, the pressure at the ICA has hardly changed after the aneurysm occlusion at the MCA. Occlusion of the aneurysm of different sizes at the MCA had almost no impact on the pressure at the ICA and ACA. For small aneurysm, the pressure of the ACA and MCA increases with decreasing size of the aneurysm at the ICA. After occlusion of a large aneurysm at the ICA, the impact on the pressure of the ACA and MCA is almost the same as after occlusion of a medium-sized aneurysm.

CONCLUSIONS

If the treatment order of ICA and MCA aneurysms cannot be determined based on patient factors and aneurysm characteristics, the MCA aneurysm should be treated as a priority.

Endovascular treatment of unruptured intracranial aneurysms with flow diverters: A retrospective long-term single center analysis

PURPOSE

The introduction of flow diverters (FDs) in 2007 greatly enhanced the treatment of intracranial aneurysms. Here, we present our long-term clinical experience in treating unruptured intracranial aneurysms with FDs.

METHODS

107 patients with unruptured aneurysms and treated with an FD between 2010 and 2019 were retrospectively reviewed. Aneurysm occlusion, procedural complications, and clinical outcome were evaluated.

RESULTS

Angiographic follow-up was available for 93 patients with a mean long-term follow-up time of 28.4 ± 21.6 months. Additional coiling was performed in 15.1% of patients (n = 14). Adequate aneurysm occlusion (Kamran grades 3 and 4) at long-term follow-up was achieved in 94.6% of patients (n = 88). 3.2% (n = 3) required endovascular retreatment since the last follow-up showed a lack of aneurysm occlusion (Kamran grade 0) due to a foreshortening of the FD. Incomplete opening of the FD and parent vessel occlusion was seen in 1.1% (n = 1) and 3.2% (n = 3) of patients, respectively. In-stent stenosis was observed in 57% (n = 53) of cases at short-term follow-up and 22.6% (n = 21) at long-term, which were moderate and asymptomatic overall. In-stent stenosis decreased significantly between short- and long-term follow-ups (31.4 ± 17.0% vs 9.7 ± 13.6%, respectively; p ≤ 0.001). Thromboembolic and hemorrhagic events occurred in 7.5% (n = 7) and 1.1% (n = 1) of patients, respectively. Good clinical outcome (modified Rankin scale: 0-2) was obtained in 97.8% (n = 91) leading to an overall treatment-related morbidity of 2.2% (n = 2). There was no procedural mortality.

CONCLUSION

Our study shows that FD treatment of unruptured intracranial aneurysms is effective and safe with high occlusion rates and low rates of permanent morbidity at long-term follow-up.

The Pipeline Embolization Device: a decade of lessons learned in the treatment of posterior circulation aneurysms in a multicenter cohort

OBJECTIVE

The Pipeline Embolization Device (PED) has prompted a paradigm shift in the approach to posterior circulation aneurysms. The year 2021 marks a decade since FDA approval of this flow diverter, and during this time operators have adapted to its off-label uses. The authors examined whether case selection, practice trends, and patient outcomes have changed over this 10-year period.

METHODS

This study is a retrospective review of consecutive posterior circulation aneurysms managed with the PED at four academic institutions in the US between January 1, 2011, and January 1, 2021. Factors related to case selection, rates of aneurysm occlusion, or complications were identified and evaluated. Angiographic outcomes as well as thromboembolic and hemorrhagic complications were investigated.

RESULTS

This study included 117 patients (median age 60 years). At a median follow-up of 12 months, adequate occlusion (> 90%) was attained in 73.2% of aneurysms. Aneurysm occlusion rates were similar over the study interval. Thromboembolic and hemorrhagic complications were reported in 12.0% and 6.0% of the procedures, respectively. There was a nonsignificant trend toward a decline in the rate of thromboembolic (14.1% in 2011-2015 vs 9.4% in 2016-2021, p = 0.443) and hemorrhagic (9.4% in 2011-2015 vs 1.9% in 2016-2021, p = 0.089) complications.

CONCLUSIONS

The authors observed a trend toward a decline in the rate of thromboembolic and hemorrhagic complications with improved operator experience in using the PED for posterior circulation aneurysms. The use of single-device PED flow diversion significantly increased, as did the tendency to treat smaller aneurysms and observe large unruptured fusiform/dolichoectatic lesions. These findings reflect changes attributable to evolving judgment with maturing experience in PED use.

Predictors of flow diverter stent in large and giant unruptured intracranial aneurysms, single-center experience

Background

Flow diversion with or without coiling has been established as the treatment of choice for large unruptured aneurysms. This study aims to assess possible predictors for radiological and clinical outcome such as location of the aneurysm (anterior or posterior circulation), complexity by a branching artery, bifurcation, and adjuvant coiling.

Methods

This study was conducted on 65 consecutive patients with 65 large, unruptured intracranial aneurysms (size ≥ 10 mm) treated with flow diverters. Follow-up angiography was done for 60 patients (92.3%) at 12 ± 8.6 months range from 3 to 36 months.

Results

Complete occlusion was achieved in 50 from 60 aneurysms (83.4%), while 8 aneurysms (13.3%) had neck remnant, and another two aneurysms (3.3%) remained with aneurysmal remnant. Periprocedural complications were encountered in 14 patients (21.5%) with morbidity in six patients (9.2%) and mortality in one patient (1.5%). In a multivariate logistic regression, anterior versus posterior location was less likely associated with worse outcome; adjusted OR (95% CI) of 0.16 (0.07–0.01), p = 0.006. Complete occlusion in complex aneurysms with branching artery was 60% versus 88% in simple aneurysms without branching artery (p-value = 0.04).

Conclusions

Flow diverter deployment of a large, unruptured aneurysm in the anterior circulation might have a better outcome than one in the posterior circulation. Flow diverter of aneurysms with branching artery or at bifurcation might be associated with aneurysm persistence and complications respectively.

Critical Angiographic and Sonographic Analysis of Intra Aneurysmal and Downstream Hemodynamic Changes After Flow Diversion

Introduction

Successful treatment of intracranial aneurysms after flow diversion (FD) is dependent on the flow modulating effect of the device. We aimed to investigate the intra-aneurysmal and parent vessel hemodynamic changes, as well as the incidence of silent emboli following treatment with various FD devices.

Methods

We evaluated the appearance of the eclipse sign in nine distinct phases of cerebral angiography before and immediately after FD placement in correlation with aneurysm occlusion. Angiographic and clinical data of consecutive procedures were analyzed retrospectively. Patients who had successful FD procedure without adjunctive coiling, visible eclipse sign on post embolization angiography, and reliable follow-up angiographic data were included in the analysis. Detailed analysis of hemodynamic data from transcranial doppler after FD was performed in selected patients, such as monitoring for silent emboli.

Results

Among all patients (N = 65) who met inclusion criteria, complete aneurysm occlusion at 12 months was achieved in 89% (58/65). Eclipse sign prior to FD was observed in 42% (27/65) with unchanged appearance in 4.6% (3/65) of the treated patients. None of these three patients achieved complete aneurysm occlusion. Among all analyzed variables, such as aneurysm size, device type used, age, and appearance of the eclipse sign pre- and post-FD, the most reliable predictor of permanent aneurysm occlusion at 12 months was earlier, prolonged, and sustained eclipse sign visibility in more than three angiographic phases in comparison to the baseline (p &lt; 0.001). Elevation in flow velocities within the ipsilateral vascular territory was noted in 70% (9/13), and bilaterally in 54% (7/13) of the treated patients. None of the patients had silent emboli.

Conclusions

Intra-aneurysmal and parent vessel hemodynamic changes after FD can be reliably assessed by the cerebral angiography and transcranial doppler with important implications for the prediction of successful treatment.

Giant Aneurysm Management

The treatment of giant aneurysms has always been a challenge in the field of neurovascular disease. Giant aneurysms are larger in size and are associated with thrombosis development and the calcification of the aneurysmal wall and neck, which often interfere with direct clipping. Most giant aneurysms have a wide neck with an incomplete thrombus, making complete embolization almost impossible. Giant aneurysms of different sites have entirely different hemodynamic characteristics. Moreover, aneurysms at the same site may exhibit very different hemodynamics among different individuals. Therefore, careful assessment of each case is required before and during treatment to develop and carry out an individualized treatment plan.

Comprehensive review of the recent advances in devices for endovascular treatment of complex brain aneurysms

The International Subarachnoid Aneurysm Trial (ISAT) showed superiority for endovascular treatment of ruptured aneurysms and technology has since moved on rapidly. Many approaches and technology now exist for the endovascular management of ruptured and unruptured intracranial aneurysms, which reflects their varied nature - there is no one-size-fits-all technique. We aim to provide an overview of the various classes of device and the major developments over the past decade. Coiling is the oldest of the technology and continues to demonstrate high levels of occlusion and acceptable risks, making it the default treatment choice, particularly in the acutely ruptured aneurysm setting. Advances on coiling include the use of adjuncts such as balloons, stents and fully retrievable temporary neck-bridging devices, which have facilitated the treatment of more complex aneurysms. Flow divertors have also revolutionised complex aneurysm treatment with small added risk in acute aneurysm treatment and seek to remodel the aneurysm-vessel interface without accessing the aneurysm sac. The latest development and most promising avenue appears to be intrasaccular flow disrupting devices like WEB, Contour and Neqstent that provide excellent opportunities to treat wide neck complex aneurysm with minimal mortality and morbidity and good occlusion rates and may in future replace a significant number of stent-assisted coiling too.

The Combination of Stent and Antiplatelet Therapy May Be Responsible of Parenchymal Magnetic Susceptibility Artifacts after Endovascular Procedure

The aim was to assess the occurrence of magnetic susceptibility artifacts (MSA) following endovascular treatment of intracranial aneurysm by stent using susceptibility weighted imaging (SWI). Imaging and clinical data of 46 patients who underwent stent placement in the case of intracranial aneurysm endovascular treatment (S-Group) were retrospectively analyzed and compared to a control group (C-Group) in which 46 patients had coiling alone. The mean number of MSA was higher in the S-group than in the C-group on postprocedural SWI sequence (8.76, 95%CI [5.76; 11.76] vs. 0.78 [0.32; 1.25], respectively, p < 0.001) with a higher frequency of the appearance of MSA also in the S-group (78.26% vs. 21.74% in the C-group, p < 0.001). In the S-group, in the vascular territory of the treated artery, there was a higher number of MSA than in other vascular territories (mean of 5.18 [3.43; 6.92] vs. 3.08 [1.79; 4.36], p = 0.001). An odds ratio (OR) of 20.98 [5.24; 83.95] suggested a higher proportion of onset of MSA in the S-group than in the C-group (p < 0.001). The appearance of MSA after a treatment by stenting for intracranial aneurysm in patients under antiplatelet therapy was common, particularly in the treated artery territory.

Utility of quantitative magnetic resonance angiography and non-invasive optimal vessel analysis for identification of complications and long-term hemodynamic changes in post-pipeline embolization patients

INTRODUCTION

Quantitative magnetic resonance angiography and non-invasive optimal vessel analysis serve as powerful tools to collect and analyze hemodynamic data from pipeline embolization patients. At our institution, patients receive post-embolization quantitative magnetic resonance angiography within 24 h of treatment and within 6 months for follow-up to evaluate pipeline patency. Here, we aim to elucidate the long-term hemodynamic changes following pipeline embolization device placement and report two cases in which in-stent stenosis was detected.

METHODS

Medical records of patients who underwent pipeline embolization device placement for an internal carotid artery aneurysm between 2017 and 2019 were reviewed. Patients who received post-procedure NOVA and follow-up NOVA were included in the study (n = 32). Location and size of aneurysm, number of pipeline embolization device deployed, and complications were collected along with the non-invasive optimal vessel analysis report (flow volume rate (ml/min), mean, systolic, and diastolic flow velocities (cm/s), and vessel diameter (mm)). Internal carotid artery vessel flow rate was measured proximal to the pipeline embolization device. Derivations of hemodynamic parameters (pulsatility index, Lindegaard ratio, and wall shear stress) were calculated.

RESULTS

The middle cerebral artery mean and diastolic flow velocities were significantly lower on the follow-up NOVA compared to the post-procedure NOVA. Moreover, follow-up NOVA demonstrated lower middle cerebral artery wall shear stress on the side with flow diversion compared to the post-procedure NOVA. In-stent stenosis, requiring intervention, was detected in two patients on follow-up NOVA. One patient had a successful balloon angioplasty of the stented internal carotid artery that resolved her stenosis. However, the second patient developed progressive stenosis and expired despite intervention.

CONCLUSION

Long-term hemodynamic adaptations post-pipeline embolization device demonstrate decreased wall shear stress and decreased mean and diastolic flow velocities in the distal middle cerebral artery, which suggest decreasing velocity of blood flow with endothelialization of the device. Furthermore, follow-up NOVA is a useful tool for detecting potential flow-related complications such as in-stent stenosis.

Endovascular Treatment of Posterior Circulation Saccular Aneurysms With the p64 Flow Modulation Device: Mid-and Long-Term Results in 54 Aneurysms From a Single Center

Objective: Flow diverter (FD) stents have become one of the most common tools for treating intracranial aneurysms; however, their role in treating posterior circulation aneurysms is still discussed with controversy. In this study, we evaluated the safety and effectiveness of p64 FD for the treatment of saccular, unruptured aneurysms in the posterior circulation over a long-term follow-up period in a single center. Methods: From our prospectively maintained database, we retrospectively identified patients who underwent treatment of an intracranial saccular aneurysm arising from the posterior circulation with ≥1 p64 FD implanted or attempted between October 2012 and December 2019. Aneurysms could have been treated with prior or concomitant saccular treatment (e.g., coiling, intra-aneurysmal flow diversion). Aneurysms with parent vessel implants other than p64, fusiform aneurysms, and dissections were excluded. Peri- and postprocedural complications, clinical outcome, and clinical and angiographic follow-up results were evaluated. Results: In total, 54 patients (45 female, 9 male; mean age 55.1 years) with 54 intracranial aneurysms met the inclusion criteria. In 51 cases (94.4%), one p64 was implanted; in 2 cases (3.7 %), two p64s were implanted; in one case, deployment of the p64 was not feasible. Procedural complications occurred in 3.7% and postprocedural complications in 9.3 %, respectively. Hemorrhagic complications occurred in 2/54 patients (3.7%), thereof one fatal parenchymal hemorrhage. Ischemic complications were observed in 5/54 patients (9.3%). Early, mid-term, and long-term angiographic follow-up examinations showed complete or near-complete aneurysm occlusion, defined according to the O'Kelly -Marotta (OKM) scale as OKM C + D in 56, 75.6, and 82.9 %, respectively. Asymptomatic side vessel occlusions occurred in 3.8%, each during the first follow-up. Conclusions: The implantation of a p64 FD is a safe and effective device for endovascular treatment of posterior circulation saccular aneurysms with a high success rate and low morbi-mortality.

Quantitative magnetic resonance angiography to assess post embolization hemodynamics following pipeline embolization

INTRODUCTION

Delayed intraparenchymal hemorrhage is a known complication of the Pipeline Embolization device (PED); however, its etiology is unclear and some have suggested it is a flow related phenomenon. Quantitative magnetic resonance angiography (QMRA) serves as a powerful tool to collect and analyze hemodynamic data. We report a detailed characterization of short-term hemodynamics after PED placement.

METHODS

Patients who underwent PED placement for a distal internal carotid artery (ICA) aneurysm between 2017 to 2019 with post embolization QMRA were reviewed. Aneurysm characteristics, flow volume rate (ml/min), mean, systolic, and diastolic flow velocities (cm/s), vessel diameter (mm), pulsatility index, Lindegaard ratio, and wall shear stress (WSS) were collected.

RESULTS

A total of 67 patients were included. Post-procedure patients were found to have a significantly lower ICA flow on the side with flow diversion when compared to the side without flow diversion (218 vs. 236.3; P < 0.05). Average ICA flow after flow diversion for aneurysms >2 cm was significantly lower when compared to the untreated side (187.7 vs. 240.4; P < 0.05). There was no difference in MCA or ACA flow or velocity. WSS was significantly lower in the treated ICA (8.2 vs. 9.0; P < 0.05). Lindegaard ratio was not different in the treated vs. contralateral untreated sides.

CONCLUSION

PED placement for distal ICA aneurysms results in lower flow, mean velocity, and WSS when compared to the contralateral untreated ICA. This is not demonstrated distal to the Pipeline device in the ACA or MCA territories. Ultimately these findings suggest hemodynamic changes are not a cause of PED complications.

Quantitative Assessment of Changes in Hemodynamics After Obliteration of Large Intracranial Carotid Aneurysms Using Computational Fluid Dynamics

Background: It was speculated that the alteration of the geometry of the artery might lead to hemodynamic changes of distal arteries. This study was to investigate the hemodynamic changes of distal arterial trees, and to identify the factors accounting for hyperperfusion after the obliteration of large intracranial aneurysms.

Methods: We retrospectively reviewed data of 12 patients with intracranial carotid aneurysms. Parametric models with intracranial carotid aneurysm were created. Patient-specific geometries were generated by three-dimensional rotational angiography. To mimic the arterial geometries after complete obliteration of the aneurysms, the aneurysms were virtually removed. The Navier–Stokes equations were solved using ANSYS CFX 14. The average wall shear stress, pressure and flow velocity were measured.

Results: Pressure ratio values were significantly higher in A1 segments, M1 segments, and M2 + M3 segments after obliteration of the aneurysms (p = 0.048 in A1 segments, p = 0.017 in M1 segments, p = 0.001 in M2 + M3 segments). Velocity ratio values were significantly higher in M1 segments and M2 + M3 segments after obliteration of the aneurysms (p = 0.047 in M1 segments, p = 0.046 in M2 + M3 segments). The percentage of pressure ratio increase after obliteration of aneurysms was significantly correlated with aneurysmal angle (r = 0.739, p = 0.006 for M2 + M3).

Conclusions: The pressure and flow velocity of distal arterial trees became higher after obliteration of aneurysms. The angle between the aneurysm and the parent artery was the factor accounting for pressure increase after treatment.

Imbalanced flow changes of distal arteries: An important factor in process of delayed ipsilateral parenchymal hemorrhage after flow diversion in patients with cerebral aneurysms

BACKGROUND AND OBJECTIVE

Hemodynamic forces may play a role in symptomatic delayed ipsilateral parenchymal hemorrhage (DIPH) of intracranial aneurysm (IA) after flow diverter placement. We aimed to investigate the hemodynamic risk factors in the postsurgical DIPH process.

METHODS

Six patients with internal carotid artery (ICA) aneurysm developed to DIPH and 12 patients without DIPH (1:2 matched controls) after flow diverter were included between January 2015 to January 2019. Postsurgical hemodynamics of distal arteries (terminal ICA, middle cerebral artery (MCA), anterior cerebral artery (ACA)) were investigated using computational fluid dynamics, as well as the hemodynamic alteration between pre- and post-treatment. The DIPH related and unrelated distal arteries (either MCA or ACA) were discriminated and compared. Definition of imbalance index is the difference in increased velocity post-flow diverter between MCA and ACA and was used to evaluate the blood flow distribution of distal arteries.

RESULTS

The mean and maximum flow velocities in the terminal ICA increased significantly after treatment in both groups. In DIPH group, the increase rate of mean velocity in the DIPH-related artery was significantly higher than that in DIPH-unrelated artery after the treatment (20.98 ± 15.38% vs -6.40 ± 7.74%; p = 0.028). Between the DIPH and control group, the baseline characteristics were well matched. However, a higher imbalance index of mean velocity was found in DIPH group (27.38 ± 13.03% vs 10.85 ± 14.12%; p = 0.031).

CONCLUSION

The mean velocity of DIPH related artery increased more, and the imbalance in increased blood flow distribution of distal arteries might play an important role in DIPH after flow diverter of IAs.

Pipeline Embolization Device for Intracranial Aneurysms in a Large Chinese Cohort: Complication Risk Factor Analysis

During intracranial aneurysm embolization with the Pipeline embolization device (PED), ischemic and hemorrhagic complications have been observed in cases among Western populations. The postmarket multicenter registry study on the embolization of intracranial aneurysms with the PED in China, i.e., the PLUS study, was performed to assess real-world predictors of complications and functional outcomes in patients treated with the PED in a Chinese population. All patients with intracranial aneurysms who underwent embolization using the PED between November 2014 and October 2019 across 14 centers in China were included. The study endpoints included preoperative and early postoperative (< 30 days) functional outcomes (modified Rankin scale [mRS] scores) and complications related to PED treatment at early postoperative and follow-up time points (3-36 months). Multivariate analysis was performed to identify risk factors for complications. A total of 1171 consecutive patients (mean age, 53.9 ± 11.4; female, 69.6% [813/1171]) with 1322 aneurysms were included in the study. Hypertension, basilar artery aneurysms, and successful deployment after adjustment or unsuccessful device deployment were found to be independent predictors of ischemic stroke, while the use of the Flex PED and incomplete occlusion immediately after treatment were protective factors. An aneurysm size > 10 mm, distal anterior circulation aneurysms, and adjunctive coiling were found to be independent predictors of delayed aneurysm rupture, distal intraparenchymal hemorrhage, and neurological compression symptoms, respectively. The rate of PED-related complications in the PLUS study was similar to that in Western populations. The PLUS study identified successful deployment after adjustment or unsuccessful device deployment and the degree of immediate postoperative occlusion as novel independent predictors of PED-related ischemic stroke in a Chinese population. ClinicalTrial.gov Identifier: NCT03831672.

Hydrophilic polymer embolization following flow diversion of cerebral aneurysms

Foreign body embolization is a rare and potentially under-recognized complication of neuroendovascular procedures. This complication should be considered in the differential diagnosis for clinical or radiological deterioration following neurovascular interventions. We report a case of foreign body hydrophilic coating embolization that occurred following an attempted flow diversion of an intracranial aneurysm with dramatic flare-up after repeat exposure. We also provide a literature review of all reported cases of hydrophilic polymer embolization following flow diversion procedures.

Factors associated with the new appearance of cerebral microbleeds after endovascular treatment for unruptured intracranial aneurysms

PURPOSE

Endovascular treatment of unruptured intracranial aneurysms may increase cerebral microbleeds (CMBs) in postprocedural T2*-weighted MRIs, which may be a risk for future intracerebral hemorrhage. This study examined the characteristics of postprocedural CMBs and the factors that cause their increase.

METHODS

The patients who underwent endovascular treatment for unruptured intracranial aneurysms from April 2016 to February 2018 were retrospectively analyzed. Treatment techniques for endovascular treatment included simple coiling, balloon-assisted coiling, stent-assisted coiling, or flow diverter placement. To evaluate the increase in CMBs, a head MRI including diffusion-weighted imaging and T2*-weighted MRIs was performed on the preprocedural day; the first postprocedural day; and at 1, 3, and 6 months after the procedure.

RESULTS

Among the 101 aneurysms that were analyzed, 38 (37.6%) showed the appearance of new CMBs. In the multivariate analysis examining the causes of the CMB increases, chronic kidney disease, a higher number of preprocedural CMBs, and a higher number of diffusion-weighted imaging-positive lesions on the first postprocedural day were independent risk factors. Furthermore, a greater portion of the increased CMBs was found in cortical and subcortical lesions of the treated vascular perfusion area within 1 month after the procedure.

CONCLUSION

In endovascular treatment for unruptured intracranial aneurysms, CMBs tended to increase in patients with small vessel disease before the procedure, and it was also implicated in hemorrhagic changes after periprocedural microinfarction.

Risk Factor Analysis of Delayed Intracerebral Hemorrhage After Coil Embolization of Unruptured Cerebral Aneurysms

Background: We sought to analyze diffusion-weighted imaging (DWI) and dual antiplatelet therapy (DAPT) for risk factors of delayed intracerebral hemorrhage (d-ICH) after coil embolization for an unruptured intracranial aneurysm (UIA).

Methods: A total of 539 aneurysms were analyzed in this study. Ruptured and flow diverter cases were excluded. All aneurysms enrolled in this study were treated with stent-assisted or simple coiling techniques. Before the procedure, all patients administered (DAPT). After the procedure, patients who underwent stent-assisted coil embolization were given DAPT, and patients who underwent simple coiling were given single antiplatelet therapy (SAPT) only during their admission. The response of the antiplatelet agent was assessed the day before the procedure with The VerifyNow assay. DWI MRI and CT were obtained routinely the next day after the procedure. d-ICH was defined as an intracerebral hemorrhagic lesion identified in follow up CT at least 48 h after the procedure.

Results: A larger positive lesion on day 1 DWI MRI (p = 0.001), the value of PRU (p = 0.002), and the inhibition rate (p = 0.025) were considered meaningful risk factors for d-ICH in univariate analysis. Accordingly, larger DWI positivity (OR = 83.73, 95% CI = 11.132–712.886, P = 0.001) and PRU (OR = 0.98, 95% CI = 0.972–0.999, P = 0.033) reached statistical significance in multivariate analysis.

Conclusions: Thromboembolic infarction may work as an initiating factor, and antiplatelet medication may work as an aggravating factor. We might suggest that a tailored reduction in antiplatelet agents could help reduce d-ICH when a larger volume of post-procedural thromboembolic infarction is seen on 1-day follow-up DWI MRI.

Computational Fluid Dynamics Using a Porous Media Setting Predicts Outcome after Flow-Diverter Treatment

BACKGROUND AND PURPOSE

Knowledge about predictors of the outcome of flow-diverter treatment is limited. The aim of this study was to predict the angiographic occlusion status after flow-diverter treatment with computational fluid dynamics using porous media modeling for decision-making in the treatment of large wide-neck aneurysms.

MATERIALS AND METHODS

A total of 27 patients treated with flow-diverter stents were retrospectively analyzed through computational fluid dynamics using pretreatment patient-specific 3D rotational angiography. These patients were classified into no-filling and contrast-filling groups based on the O'Kelly-Marotta scale. The patient characteristics, morphologic variables, and hemodynamic parameters were evaluated for understanding the outcomes of the flow-diverter treatment.

RESULTS

The patient characteristics and morphologic variables were similar between the 2 groups. Flow velocity, wall shear stress, shear rate, modified aneurysmal inflow rate coefficient, and residual flow volume were significantly lower in the no-filling group. A novel parameter, called the normalized residual flow volume, was developed and defined as the residual flow volume normalized by the dome volume. The receiver operating characteristic curve analyses demonstrated that the normalized residual flow volume with an average flow velocity of ≥8.0 cm/s in the aneurysmal dome was the most effective in predicting the flow-diverter treatment outcomes.

CONCLUSIONS

It was established in this study that the hemodynamic parameters could predict the angiographic occlusion status after flow-diverter treatment.

Outcome of flow diverter placement for intracranial aneurysm with dual antiplatelet therapy and oral anticoagulant therapy

PURPOSE

Antiplatelet therapy initiated before flow diverter placement is effective for the prevention of ischemic complications. However, the effectiveness of oral anticoagulant treatment is unclear. This retrospective study evaluated the complications and obliteration rates after flow diverter placement in patients taking anticoagulants.

METHODS

A total of 155 cases were treated by Pipeline Flex placement for unruptured large and giant cerebral aneurysms in our hospital between October 2015 and June 2019. The groups of 8 patients taking anticoagulants before operation and 147 patients not taking anticoagulants were compared.

RESULTS

Clopidogrel oral dose (P = 0.002) was significantly lower in the anticoagulant group. Delayed aneurysm rupture (P = 0.002) and additional treatment (P = 0.009) rates were significantly higher and complete obliteration rate (P = 0.011) was lower in the anticoagulant group.

CONCLUSIONS

Additional oral anticoagulant administration before flow diverter placement does not reduce ischemic complications compared to dual antiplatelet therapy, but does increase hemorrhagic complications, especially delayed aneurysm rupture. Complete obliteration of the cerebral aneurysm is difficult to achieve in patients taking anticoagulants.

The Pipeline Embolization Device: Changes in Practice and Reduction of Complications in the Treatment of Anterior Circulation Aneurysms in a Multicenter Cohort

BACKGROUND

The Pipeline Embolization Device (PED; Medtronic, Dublin, Ireland) has become an important tool for the treatment of cerebral aneurysms. Since FDA approval, there are ongoing efforts to increase aneurysm occlusion rates and reduce the incidence of complications.

OBJECTIVE

To assess aneurysm occlusion and complication rates over time.

METHODS

Retrospective analysis of consecutive anterior circulation aneurysms treated with a single PED between 2011 and 2016 at 3 academic institutions in the US was performed. Factors contributing to changes in aneurysm occlusion and complication rates over time were identified and evaluated.

RESULTS

A total of 284 procedures were performed on 321 anterior circulation aneurysms in 284 patients. At a median follow-up of 13 mo (mean 18 mo), complete or near complete occlusion (>90%) was achieved in 85.9% of aneurysms. There was no significant change in aneurysm occlusion rate or procedure length over time. Thromboembolic complication occurred in 8.1% of procedures, and there was a trend toward decreased incidence from 16.3% in 2011/2012 to 3.3% in 2016 (P = .14). Hemorrhagic complications significantly decreased from 8.2% in 2011/2012 to 0 to 1.0% in 2014-2016 (P = .1).

CONCLUSION

We report a notable drop in the rate of hemorrhagic and to a lesser extent thromboembolic complications with increased experience with PED in a multicenter cohort. Multiple factors are believed to contribute to this drop, including the evolved interpretation of platelet function testing, the switching of clopidogrel nonresponders to ticagrelor, and the reduced use of adjunctive coiling.

Delayed Remote Intracerebral Hemorrhage after Wingspan Stenting for Internal Carotid Artery Stenosis Following the On-Label Usage Guidelines

Remote intracerebral hemorrhage (ICH) is defined as an ICH that occurs at a distant site from the treated lesion and is a considerable post-neurointerventional complication. Because such a life-threatening complication should not be neglected, we report our experience with delayed remote ICH in a patient with symptomatic intracranial atherosclerotic stenosis (ICAS) treated by Wingspan stenting following on-label usage guidelines. A middle-aged person suffered a lobar-type subcortical hemorrhage on the left temporal lobe 22 days after Wingspan stenting in the left internal carotid artery. The present case seemed to correspond with a previous report in which remote ICH tended to occur as an ipsilateral lobar-type hemorrhage in patients with unruptured intracranial aneurysm on the internal carotid artery undergoing treatment with stents or flow diverters. Delayed remote ICH should be considered as a potential risk of using a Wingspan stent covering the carotid siphon for ICAS.

Multicenter Study of Pipeline Flex for Intracranial Aneurysms

BACKGROUND

The Pipeline Flex (PED Flex; Medtronic, Dublin, Ireland) was designed to facilitate deployment and navigation compared to its previous iteration to reduce the rate of technical events and complications.

OBJECTIVE

To assess the neurological morbidity and mortality rates of the PED Flex at 30 d.

METHODS

Information from 9 neurovascular centers was retrospectively obtained between July 2014 and March 2016. Data included patient/aneurysm characteristics, periprocedural events, clinical, and angiographic outcomes. Multivariate logistic regression was performed to determine predictors of unfavorable clinical outcome (modified Rankin Scale [mRS] > 2).

RESULTS

A total of 205 patients harboring 223 aneurysms were analyzed. The 30-d neurological morbidity and mortality rates were 1.9% (4/205) and 0.5% (1/205), respectively. The rate of intraprocedural events without neurological morbidity was 6.8% (14/205), consisting of intraprocedural ischemic events in 9 patients (4.5%) and hemorrhage in 5 (2.4%). Other technical events included difficulty capturing the delivery wire in 1 case (0.5%) and device migration after deployment in another case (0.5%). Favorable clinical outcome (mRS 0-2) was achieved in 186 patients (94.4%) at discharge and in 140 patients (94.5%) at 30 d. We did not find predictors of clinical outcomes on multivariate analysis.

CONCLUSION

The 30-d rates of neurological morbidity and mortality in this multicenter cohort using the PED Flex for the treatment of intracranial aneurysms were low, 1.9% (4/205) and 0.5% (1/205), respectively. In addition, technical events related to device deployment were also low, most likely due to the latest modifications in the delivery system.

The Evolution of Flow-Diverting Stents for Cerebral Aneurysms; Historical Review, Modern Application, Complications, and Future Direction

In spite of the developing endovascular era, large (15–25 mm) and giant (>25 mm) wide-neck cerebral aneurysms remained technically challenging. Intracranial flow-diverting stents (FDS) were developed to address these challenges by targeting aneurysm hemodynamics to promote aneurysm occlusion. In 2011, the first FDS approved for use in the United States market. Shortly thereafter, the Pipeline of Uncoilable or Failed Aneurysms (PUFS) study was published demonstrating high efficacy and a similar complication profile to other intracranial stents. The initial FDA instructions for use (IFU) limited its use to patients 22 years old or older with wide-necked large or giant aneurysms of the internal carotid artery (ICA) from the petrous segment to superior hypophyseal artery/ophthalmic segment. Expanded IFU was tested in the Prospective Study on Embolization of Intracranial Aneurysms with PipelineTM Embolization Device (PREMIER) trial. With further post-approval clinical data, the United States FDA expanded the IFU to include patients with small or medium, wide-necked saccular or fusiform aneurysms from the petrous ICA to the ICA terminus. However, IFU is more restrictive in South Korea than in United States. Several systematic reviews and meta-analyses have sought to evaluate the overall efficacy of FDS for the treatment of cerebral aneurysms and consistently identify FDS as an effective technique for the treatment of aneurysms broadly with complication rates similar to other traditional techniques. A growing body of literature has demonstrated high efficacy of FDS for small aneurysms; distal artery aneurysms; non-saccular aneurysms posterior circulation aneurysms and complication rates similar to traditional techniques. In the short interval since the Pipeline Embolization Device was first introduced, FDS has been firmly entrenched as a powerful tool in the endovascular armamentarium. As new FDS are developed, established FDS are refined, and delivery systems are improved the uses for FDS will only expand further. Researchers continue to work to optimize the mechanical characteristics of the FDS themselves, aiming to optimize deploy ability and efficacy. With expanded use for small to medium aneurysms and posterior circulation aneurysms, FDS technology is firmly entrenched as a powerful tool to treat challenging aneurysms, both primarily and as an adjunct to coil embolization. With the aforementioned advances, the ease of FDS deployment will improve and complication rates will be further minimized. This will only further establish FDS deployment as a key strategy in the treatment of cerebral aneurysms.

Mechanism of Action and Biology of Flow Diverters in the Treatment of Intracranial Aneurysms

Flow diverters have drastically changed the landscape of intracranial aneurysm treatment and are now considered first-line therapy for select lesions. Their mechanism of action relies on intrinsic alteration in hemodynamic parameters, both at the parent artery and within the aneurysm sac. Moreover, the device struts act as a nidus for endothelial cell growth across the aneurysm neck ultimately leading to aneurysm exclusion from the circulation. In silico computational analyses and investigations in preclinical animal models have provided valuable insights into the underlying biological basis for flow diverter therapy. Here, we review the present understanding pertaining to flow diverter biology and mechanisms of action, focusing on stent design, induction of intra-aneurysmal thrombosis, endothelialization, and alterations in hemodynamics.

Predictors of Complications, Functional Outcome, and Morbidity in a Large Cohort Treated With Flow Diversion

BACKGROUND

A dramatic improvement in obliteration rates of large, wide-necked aneurysms has been observed after the FDA approved the Pipeline Embolization Device (PED) in 2011.

OBJECTIVE

To assess the predictors of complications, morbidity, and unfavorable outcomes in a large cohort of patients with aneurysms treated with PED.

METHODS

A retrospective chart review of a prospectively maintained database for subjects treated with flow diversion from 2010 to 2019.

RESULTS

A total of 598 aneurysms were treated during a period extending from 2010 to 2019 (84.28% females, mean age 55.5 yr, average aneurysm size 8.49 mm). Morbidity occurred at a rate of 5.8% and mortality at a rate of 2.2%. Ischemic stroke occurred at a rate of 3%, delayed aneurysmal rupture (DAR) at 1.2%, and distal intraparenchymal hemorrhage (DIPH) at 1.5%. On multivariate analysis, the predictor of stroke was aneurysm size &gt;15 mm. Predictors of DAR were previous subarachnoid hemorrhage (SAH), increasing aneurysm size, and posterior circulation aneurysm. Predictors of DIPH were using more than 1 PED and baseline P2Y12 value. Predictors of in-stent stenosis were the increasing year of treatment and balloon angioplasty, whereas increasing age and previous treatment were negatively associated with in-stent stenosis. Predictors of morbidity were posterior circulation aneurysms, increasing aneurysm size, and hypertension, and incidental aneurysm diagnosis was protective for morbidity.

CONCLUSION

Flow diversion is a safe and effective treatment option for aneurysms. A better understanding of predictive factors of complications, morbidity, and functional outcomes is of high importance for a more accurate risk assessment.

Factors influencing blood flow resistance from a large internal carotid artery aneurysm revealed by a computational fluid dynamics model

Hyperperfusion syndrome occurs after treatment of a large or giant cerebral aneurysm. Recently, flow-diverter stent placement has emerged as an effective treatment method for a large cerebral aneurysm, but postoperative ipsilateral delayed intraparenchymal hemorrhage occurs in a minority of cases. The mechanism underlying delayed intraparenchymal hemorrhage is not established, but one possibility is hyperperfusion syndrome. The incidence of delayed intraparenchymal hemorrhage appears to be higher for giant aneurysms; hence, we speculated that large/giant aneurysms may create flow resistance, and mitigation by flow-diverter stent deployment leads to hyperperfusion syndrome and delayed intraparenchymal hemorrhage. The purpose of this study was to identify aneurysm characteristics promoting flow resistance by the analysis of pressure loss in an internal carotid artery paraclinoid aneurysm model using computational fluid dynamics. A virtual U-shaped model of the internal carotid artery siphon portion was created with a spherical aneurysm of various angles, body diameters, and neck diameters. Visualization of streamlines, were calculated of pressure loss between proximal and distal sides of the aneurysm, and vorticity within the aneurysm were calculated. The pressure loss and vorticity demonstrated similar changes according to angle, peaking at 60°. In contrast, aneurysm diameter had little influence on pressure loss. Larger neck width, however, increases pressure loss. Our model predicts that aneurysm location and neck diameter can increase the flow resistance from a large internal carotid artery aneurysm. Patients with large aneurysm angles and neck diameters may be at increased risk of hyperperfusion syndrome and ensuing delayed intraparenchymal hemorrhage following flow-diverter stent treatment.

Endovascular Treatment of Large and Giant Carotid Aneurysms with Flow-Diverter Stents Alone or in Combination with Coils: A Multicenter Experience and Long-Term Follow-up

BACKGROUND

Although flow diverters (FDs) have been widely accepted by neurointerventionists, their safety has yet to be fully defined. Stratification by aneurysm size and location is essential for correct evaluation of treatment outcomes and risks of flow diversion.

OBJECTIVE

To compare neurological and anatomic outcomes and evaluate the risk of complications after endovascular treatment of large or giant internal carotid artery (ICA) aneurysms with FD/FDs alone or together with coil embolization.

METHODS

We reviewed all patients with large or giant, ruptured or unruptured ICA aneurysms who underwent endovascular treatment with flow diversion alone (group A) or with concomitant coiling (group B) in 4 international institutions between 2010 and 2015. Anatomic outcome was evaluated using the Byrne scale on digital subtraction angiography and/or angioMRI and/or angioCT scans 3, 6, 12, and 24 months postoperatively.

RESULTS

We collected 44 patients with large or giant ICA aneurysms. Four patients (9%) presented with aneurysmal subarachnoid hemorrhage (SAH). FD/FDs were used alone in 26 patients and in combination with coil embolization in the 18 remaining patients. The mortality rate due to procedure-related and/or neurological complications was 2.2%. Twelve months after the procedure, 88.6% (n = 39) of patients had a favorable neurological outcome. One year after the procedure, the aneurysm was completely occluded in 72.7% of patients: 61.5% (16/18) in group A and 88.9% (16/26) in group B.

CONCLUSION

Clinical outcomes and rates of intraoperative and postoperative complications did not differ significantly between the groups. Better anatomic results using FD/FDs combined with coils were documented 6 months after the procedure; this option seems to provide a higher aneurysm occlusion rate and reduce the need for retreatment.

Microhemorrhagic transformation of ischemic lesions on T2*-weighted magnetic resonance imaging after Pipeline embolization device treatment

OBJECTIVE

The authors sought to demonstrate that hemorrhagic transformation of ischemic lesions is the main cause of delayed intracerebral hemorrhage (ICH) after Pipeline embolization device (PED) treatment and to estimate the rate of hemorrhagic transformation of new postprocedure ischemic lesions.

METHODS

Patients who underwent PED placement (PED group) from November 2015 to March 2017 or stent-mediated embolization (EN group) from December 2010 to October 2015 were retrospectively analyzed. Pre- and postprocedural MR images and 6-month follow-up MR images for each patient were scored for the presence of postprocedural bland ischemic and hemorrhagic lesions using diffusion-weighted MRI (DWI) and T2*-weighted MRI (T2*WI), respectively.

RESULTS

The PED group comprised 28 patients with 30 intracranial aneurysms, and the EN group comprised 24 patients with 27 intracranial aneurysms. The mean number of ischemic lesions on DWI 1 day postprocedure was higher in the PED group than in the EN group (5.2 vs 2.7, p = 0.0010). The mean number of microbleeds detected on T2*WI 6 months postprocedure was higher in the PED group than in the EN group (0.6 vs 0.15, p = 0.028). A total of 36.7% of PED-treated patients exhibited new microbleeds on T2*WI at 6 months postprocedure, with at least 77.8% of these lesions representing hemorrhagic transformations of the new ischemic lesions observed on day 1 postprocedure. The rate of adjunctive coil embolization (27.3% vs 0.0%, p = 0.016) and the mean number of ischemic lesions observed 1 day postprocedure (6.6 vs 4.3, p = 0.020) were predictors of subsequent microbleeds in the PED group.

CONCLUSIONS

New microbleeds detected using T2*WI at 6 months postprocedure were more common after PED treatment than after stent-mediated embolization. Approximately three-quarters of these lesions were hemorrhagic transformations of new ischemic lesions observed on day 1 postprocedure. Prevention of intraprocedural or postprocedural infarcts is necessary to reduce the risk of hemorrhagic complications following PED placement.

Single-center experience with the new-generation Derivo embolization device for ruptured and unruptured intracranial aneurysms

BACKGROUND

The aim of this study is to evaluate safety and efficacy of the new-generation Derivo embolization device in complex ruptured (RIA) and unruptured (UIA) intracranial aneurysms.

METHODS

Retrospective analysis of 32 patients with complex RIAs and UIAs treated with Derivo at our hospital from November 2015 to December 2018. Clinical safety was defined as absence of death, transient attack, absence of minor and major stroke, and Derivo associated hemorrhage. Treatment efficacy was assessed angiographically (DSA) immediately after treatment and at 6-month follow-up according to the O'Kelly-Marotta (OKM) Grading Scale (from A=total filling to D=no filling; prolongation of stasis 1=arterial to 3=venous phase).

RESULTS

Thirty-two patients with 39 aneurysms were treated with 42 Derivos. In five aneurysms, additional coiling was performed. Deployment was technically successful in all cases. Two patients developed a procedure related minor stroke (one transient). In one patient bleeding due to an inflammatory aneurysmatic wall process occurred 20 days after retreatment and in one patient a stroke due to in-stent thrombosis occurred when dual platelet inhibition (PI) was switched to permanent single PI 12 month after FD treatment. No treatment related deaths were observed. Initial DSA revealed three OKM D, six OKM C, five OKM B, and 25 OKM A. Six-month follow-up for DSA and clinical evaluation was available in 20/32 patients (62.5%), 26 of 39 aneurysms (66.7%) and revealed 73.1% complete and 3.8% subtotal occlusion (OKM D: 19 of 26, OKM C3: one of 26).

CONCLUSIONS

Treatment of complex RIAs and UIAs with the new-generation Derivo appeared to be safe and effective in this single-center case series for ruptured and unruptured intracranial aneurysms. Immediate DSA revealed a significant flow modulation; and 6-month follow-up showed a high occlusion rate.

Usefulness of Silent MR Angiography for Intracranial Aneurysms Treated with a Flow-Diverter Device

BACKGROUND AND PURPOSE

The flow-diverter device has been established as a treatment procedure for large unruptured intracranial aneurysms. The purpose of this study was to compare the usefulness of Silent MR angiography and time-of-flight MRA to assess the parent artery and the embolization state of the aneurysm after a flow-diverter placement.

MATERIALS AND METHODS

Seventy-eight large, unruptured internal carotid aneurysms in 78 patients were the subjects of this study. After 6 months of treatment, they underwent follow-up digital subtraction angiography, Silent MRA, and TOF-MRA, performed simultaneously. All images were independently reviewed by 2 neurosurgeons and 1 radiologist and rated on a 4-point scale from 1 (not visible) to 4 (excellent) to evaluate the parent artery. The aneurysmal embolization status was assessed with 2 ratings: complete or incomplete occlusion.

RESULTS

The mean scores of Silent MRA and TOF-MRA regarding the parent artery were 3.18 ± 0.72 and 2.31 ± 0.86, respectively, showing a significantly better score with Silent MRA (P < .01). In the assessment of the embolization of aneurysms on Silent MRA and TOF-MRA compared with DSA, the percentages of agreement were 91.0% and 80.8%, respectively.

CONCLUSIONS

Silent MRA is superior for visualizing blood flow images inside flow-diverter devices compared with TOF-MRA. Furthermore, Silent MRA enables the assessment of aneurysmal embolization status. Silent MRA is useful for assessing the status of large and giant unruptured internal carotid aneurysms after flow-diverter placement.

Patency of anterior choroidal artery after flow diverter deployment with assessment of magnetic resonance imaging follow-up

PURPOSE

We aimed to analyse the patency rate of the anterior choroidal artery, and presented imaging and neurological findings, after deployment of a flow diverter in the anterior choroidal artery in the treatment of patients with intracranial aneurysms.

METHODS

Among the 139 patients who underwent a flow diverter deployment from December 2012 to September 2017 in our hospital, there were 21 patients (15.1%) for whom their anterior choroidal artery was covered for the procedure with a flow diverter. The patients' age, sex, size of aneurysm and the presence or absence of an anterior choroidal artery occlusion, neurological findings and postoperative infarction in the anterior choroidal artery region were analysed retrospectively.

RESULTS

The mean age of the six male and 15 female patients was 61.5 years (range 32-77 years). The mean maximal diameter of the aneurysms was 16.4 mm (range 10.0-29.4 mm). The anterior choroidal artery was patent in all 21 patients; however, a haemodynamic alteration in the anterior choroidal artery was detected in one patient. Postoperatively, hemiparesis was observed in two patients (9.5%) and a visual field defect in one patient (4.8%), both of which were the symptoms of infarction of the cortical branch of the middle cerebral artery or retinal artery ischaemia. However, no patients had symptoms due to ischaemia of the anterior choroidal artery confirmed with magnetic resonance imaging.

CONCLUSIONS

In all patients who underwent flow diverter deployment, the anterior choroidal artery was patent and no ischaemia was detected in the imaging or evidenced by neurological findings. Therefore, flow diverter deployment in the anterior choroidal artery was considered to be a safe procedure.

Downstream vascular changes after flow-diverting device deployment in a rabbit model

BACKGROUND

Flow diverters (FDs) are increasingly used in the treatment of intracranial aneurysms, and carry the risk of thromboembolic complications, even in patients treated with dual antiplatelet therapy. The effect of FDs on the downstream vascular is unknown. The aim of the study was to investigate vascular wall pulse wave velocity (PWV) and contractility changes following FD treatment in a rabbit model.

METHODS

FDs (Pipeline Embolic Device, Medtronic Inc., Irvine, California, USA) were implanted in the aorta of normal rabbits and sham-operated aorta were used as controls (n=6 per group). Pulse wave imaging with ultra-fast ultrasound at 1600 frames per second (Vantage, Verasonics, Inc., Kirkland, WA) was performed in the vessel wall distal to FD prior to device implantation and at 8- week follow-up to measure the PWV. Force contraction vascular reactivity studies were conducted in the aortic rings using an organ bath.

RESULTS

The difference in mean PWV in the follow-up compared with pre-implantation was significantly higher in the distal vessels compared with sham controls (1.18 m/s [SD=0.54] vs. 0.37 m/s [SD=1.09], P=0.03). Conversely, the aortic segments distal to the FD exhibited a 55% increase in vascular contractility compared with proximal segments (P=0.002). We observed a significant positive correlation between mean PWV and mean vascular contractility.

CONCLUSION

Implantation of FD was associated with increased PWV and vascular contractility, suggesting that FD implantation causes changes to the vascular wall. Further studies are needed to understand the clinical implication of changes in vascular PWV and contractility.

Bailout Strategies and Complications Associated with the Use of Flow-Diverting Stents for Treating Intracranial Aneurysms

Background

Flow-diverting stents (FDS) have revolutionized the endovascular management of unruptured, complex, wide-necked, and giant aneurysms. There is no consensus on management of complications associated with the placement of these devices. This review focuses on the management of complications of FDS for the treatment of intracranial aneurysms.

Summary

We performed a systematic, qualitative review using electronic databases MEDLINE and Google Scholar. Complications of FDS placement generally occur during the perioperative period.

Key Message

Complications associated with FDS may be divided into periprocedural complications, immediate postprocedural complications, and delayed complications. We sought to review these complications and novel management strategies that have been reported in the literature.

Reconsiderations on the use of pipeline embolization device in the treatment of intracerebral aneurysms with special angioarchitecture: fetal PCA, AVM, V-B junction and DAVF

Background

Pipeline embolization device (PED) has proved its safety and efficacy in the treatment of intracranial large and giant side-wall aneurysms. With the accumulation of treatment experience, it is an inevitable trend to expand its off-label use on aneurysms. Whether flow diversion is safe and efficient in cases with special angioarchitecture has rarely been explored.

Methods

We performed a retrospective analysis of 210 consecutive patients treated by PED for intracerebral aneurysms in our center. Except for aneurysm, those patients also presented with special angioarchitecture: Fetal PCA, AVM, V-B junction and DAVF.

Results

Nine patients were qualified for the study. 1 was with fetal PCA, the aneurysm remained patent on 4-month follow-up. 2 with ipsilateral AVMs, one patient died due to brain hemorrhage 20 days after the operation, the other one was only partially embolised on 6 month follow up. 3 aneurysms located at V-B junction, angiographic follow up on 3 months demonstrated no complete occlusion of both the aneurysms, the other patients were still on follow up. All of the 3 cases with concomitant DAVF are completely occluded during short to midterm follow up.

Conclusions

PED for aneurysms incorporated the fetal PCA and V-B junction might meet a high propensity for incomplete occlusion during short term follow up. Aneurysm with ipsilateral AVM is not suitable for PED treatment due to the risk of hemorrhage and incomplete occlusion during midterm follow up. For aneurysm with concurrent DAVF, PED treatment is safe and efficient relatively in one session or by staged operation.

Validation of parametric mesh generation for subject-specific cerebroarterial trees using modified Hausdorff distance metrics

Accurate subject-specific vascular network reconstruction is a critical task for the hemodynamic analysis of cerebroarterial circulation. Vascular skeletonization and computational mesh generation for large sections of cerebrovascular trees from magnetic resonance angiography (MRA) is an error-prone, operator-dependent, and very time-consuming task. Validation of reconstructed computational models is essential to ascertain their accuracy and precision, which directly relates to the confidence of CFD computations performed on these meshes. The aim of this study is to generate an imaging segmentation pipeline to validate and quantify the spatial accuracy of computational models of subject-specific cerebral arterial trees. We used a recently introduced parametric structured mesh (PSM) generation method to automatically reconstruct six subject-specific cerebral arterial trees containing 1364 vessels and 571 bifurcations. By automatically extracting sampling frames for all vascular segments and bifurcations, we quantify the spatial accuracy of PSM against the original MRA images. Our comprehensive study correlates lumen area, pixel-based statistical analysis, area overlap and centerline accuracy measurements. In addition, we propose a new metric, the pointwise offset surface distance metric (PSD), to quantify the spatial alignment between dimensions of reconstructed arteries and bifurcations with in-vivo data with the ability to quantify the over- and under-approximation of the reconstructed models. Accurate reconstruction of vascular trees can a practical process tool for morphological analysis of large patient data banks, such as medical record files in hospitals, or subject-specific hemodynamic simulations of the cerebral arterial circulation.

Quantification of near-wall hemodynamic risk factors in large-scale cerebral arterial trees

Detailed hemodynamic analysis of blood flow in pathological segments close to aneurysm and stenosis has provided physicians with invaluable information about the local flow patterns leading to vascular disease. However, these diseases have both local and global effects on the circulation of the blood within the cerebral tree. The aim of this paper is to demonstrate the importance of extending subject-specific hemodynamic simulations to the entire cerebral arterial tree with hundreds of bifurcations and vessels, as well as evaluate hemodynamic risk factors and waveform shape characteristics throughout the cerebral arterial trees. Angioarchitecture and in vivo blood flow measurement were acquired from healthy subjects and in cases with symptomatic intracranial aneurysm and stenosis. A global map of cerebral arterial blood flow distribution revealed regions of low to high hemodynamic risk that may significantly contribute to the development of intracranial aneurysms or atherosclerosis. Comparison of pre-intervention and post-intervention of pathological cases further shows large angular phase shift (~33.8°), and an augmentation of the peak-diastolic velocity. Hemodynamic indexes of waveform analysis revealed on average a 16.35% reduction in the pulsatility index after treatment from lesion site to downstream distal vessels. The lesion regions not only affect blood flow streamlines of the proximal sites but also generate pulse wave shift and disturbed flow in downstream vessels. This network effect necessitates the use of large-scale simulation to visualize both local and global effects of pathological lesions.

Symptomatic periprocedural intracranial hemorrhage unrelated to coil embolization in 1287 patients with intracranial aneurysms

PURPOSE

Periprocedural symptomatic intracranial hemorrhage (sICH) unrelated to coil embolization of intracranial aneurysm has been rarely reported. The incidence and characteristics of this complication remain unclear. This study was designed to elucidate the incidence and characteristics of periprocedural sICH unrelated to coiling of intracranial aneurysm, and to explore the possible mechanisms underlying this complication.

METHODS

Included in this retrospective study were 1287 patients with 1394 aneurysms who were treated with coil embolization (476 patients with stent assistance and 811 patients without stents) between May 2008 and August 2017. All procedure-unrelated sICHs that occurred within 30 days after coiling were selected. The technical details of the procedure, clinical characteristics, and medical therapy were recorded.

RESULTS

A total of 6 patients developed periprocedural sICH unrelated to coil embolization. All these six patients underwent stent-assisted coiling (SAC). Therefore, there was a 1.3% (6/476) procedure-unrelated sICH rate of SAC and 0% (0/811) in patients underwent coiling without stent during the periprocedural period (P = 0.005, RR 0.987; 95% CI, 0.977-0.997). These phenomena occurred more often in patients who received SAC for ruptured aneurysms vs patients underwent this technique for unruptured aneurysms (2.0 vs 0.7%, P = 0.390, RR 2.896; 95% CI, 0.525-15.968). All these phenomena occurred within 7 days after coiling, and resulted in one mortality, one unfavorable outcome (mRS Score 3), and other four favorable outcomes (mRS Scores 0-2) at 90 days after procedure.

CONCLUSION

Our findings suggest that the procedure-unrelated sICH, though less frequent, may exist following stent-assisted coiling of intracranial aneurysm during the periprocedural period. Extra caution may be warranted in patients who were treated with SAC for ruptured aneurysms.

Rescue Therapy for Procedural Complications Associated With Deployment of Flow-Diverting Devices in Cerebral Aneurysms

Flow diverting devices (FDDs) have revolutionized the treatment of morphologically complex intracranial aneurysms such as wide-necked, giant, or fusiform aneurysms. Although FDDs are extremely effective, they carry a small yet significant risk of intraprocedural complications. As the implementation of these devices increases, the ability to predict and rapidly treat complications, especially those that are iatrogenic or intraprocedural in nature, is becoming increasingly more necessary.

Our objective in this paper is to provide a descriptive summary of the various types of intraprocedural complications that may occur during FDDs deployment and how they may best be treated. A systematic and qualitative review of the literature was conducted using electronic databases MEDLINE and Google Scholar. Searches consisted of Boolean operators “AND” and “OR” for the following terms in different combinations: “aneurysm,” “endovascular,” “flow diverter,” “intracranial,” and “pipeline.”

A total of 94 papers were included in our analysis; approximately 87 of these papers dealt with periprocedural endovascular (mainly related to FDDs) complications and their treatment; 7 studies concerned background material. The main categories of periprocedural complications encountered during deployment of FDDs are failure of occlusion, parent vessel injury and/or rupture, spontaneous intraparenchymal hemorrhage, migration or malposition of the FDDs, thromboembolic or ischemic events, and side branch occlusion

Periprocedural complications occur mainly due to thromboembolic events or mechanical issues related to device deployment and placement. With increasing use and expanding versatility of FDDs, the understanding of these complications is vital in order to effectively manage such situations in a timely manner.

Effect of flow diversion with silk on aneurysm size: A single center experience

Alterations in aneurysm size and mass effect can result in alleviation or aggravation of symptoms. We assessed the effects of flow diversion with SILK stents on aneurysm sac size and associated factors. A retrospective evaluation of 14 aneurysms treated with SILK stents alone with MRI follow-up was performed. Aneurysm sac size was measured using the sequence best demonstrating the sac. Aneurysm characteristics and flow-related enhancement on time of flight images were documented. Clinical histories were reviewed for evolution of symptoms. Complete collapse of the aneurysm sac was demonstrated at three and 18 months in 2/14 aneurysms. Increase in size was observed in 2/14 aneurysms with associated persistent flow on time of flight MRA. Blister formation with aggravation of symptoms was observed in one aneurysm, and subsequent decrease in size occurred after treatment with a second SILK. The other aneurysm which increased in size initially continued to enlarge asymptomatically despite retreatment with a second SILK, however at 24 months thrombosis of the sac and decrease in size was observed. The remaining 10/14 aneurysms decreased in size. Nine had corresponding MRA occlusion and the tenth demonstrated decreased but persistent flow on the time of flight MRA. No aneurysm with MRA occlusion increased in size. Decrease in sac size was associated with MRA occlusion in our study. Persistence of flow and blistering were associated with increased sac size. As previously demonstrated flow diversion may be effective in the treatment of large aneurysms presenting with mass effect, however rates of sac obliteration in this small series were not as high as previously reported.

Periprocedural safety of Pipeline therapy for unruptured cerebral aneurysms: Analysis of 279 Patients in a multihospital database

The relative safety of unruptured aneurysm treatment with coiling versus flow diversion therapy is unknown. Most data available on flow diversion reflect highly focused patient groups and very experienced operators. We evaluated a national, multihospital patient database to examine periprocedural morbidity and mortality in patients treated with endovascular flow diversion therapy. The Premier Perspective database was used to identify patients hospitalized between May 2011 and March 2013 for unruptured aneurysm who underwent flow diversion therapy with a Pipeline embolization device. The risk of in-hospital mortality and morbidity was determined using ICD 9 codes. A total of 279 unruptured aneurysm patients at 18 medical centers underwent endovascular therapy with a Pipeline device. Adverse outcomes included in-hospital mortality in two cases (0.7%), discharge to long-term care in 22 cases (7.9%), ischemic complications in 14 cases (5.0%), hemorrhagic complications in four cases (1.4%), and postoperative neurological complications in nine cases (3.2%). This study of a large cohort of patient hospitalizations in the United States provides preliminary data on flow diversion in a "real world" scenario and demonstrates that the periprocedural morbidity and mortality is not negligible and must be considered in the context of the natural history of the aneurysms that are being treated.