Computational fluid dynamics with stents: quantitative comparison with particle image velocimetry for three commercial off the shelf intracranial stents

Background and purpose

Validation of computational fluid dynamics (CFD) in stented intracranial aneurysms (IAs) is still lacking, to reliably predict prone to occlusion hemodynamics, probing, in particular, velocity reduction, and flow pattern changes. This study compares CFD outcome with particle imaging velocimetry (PIV) for three commercial off the shelf (COTS) stents of different material densities.

Material and methods

The recently developed uniform and high precision multi-time lag PIV method was applied to a sidewall aneurysm before and after implantation of three COTS stents with high, intermediate, and low material densities. The measured laser sheet flow patterns and velocity reductions were compared with CFD results and correlated with stent material density.

Results

Velocity reduction was in good agreement for unstented high and low porosity stented IA, while flow pattern change was fully matched for unstented and high porosity stented IA. Poor CFD–PIV matching in IA was found for intermediate porosity stents.

Conclusions

CFD reproduced fully PIV measurements in unstented and high porosity stented IAs. With low porosity stents, CFD reproduced velocity reduction and high velocities close to the neck, while a marked mismatch on sluggish flow was found at the dome. CFD was unable to match PIV with intermediate porosity stents for which hemodynamic transition occurred.

State-of-the-art endovascular treatment of acute ischemic stroke

Stroke is the third leading cause of death in the USA. An estimated 795,000 new or recurrent stroke events occur annually, mostly ischemic in nature. Arterial recanalization and subsequent reperfusion performed shortly after symptom onset can help to restore brain function in acute ischemic stroke (AIS). The only treatment currently approved by the United States Food and Drug Administration is intravenous tissue plasminogen activator, administered within 4.5 h of symptom onset. However, this short window often precludes effective intervention. Mechanical neurothrombectomy devices offer many potential advantages over pharmacologic thrombolysis, including more rapid achievement of recanalization, enhanced efficacy in treating large-vessel occlusions, and a potentially lower risk of hemorrhagic events. The goal of this chapter is to describe the state-of-the-art neurothrombectomy devices and stenting techniques for endovascular treatment of acute ischemic stroke, as well as to highlight recent advances in reperfusion therapies. Ongoing clinical trials, some with randomized, controlled designs, are included.

Impact of age and baseline NIHSS scores on clinical outcomes in the mechanical thrombectomy using solitaire FR in acute ischemic stroke study

BACKGROUND AND PURPOSE

Age and stroke severity are inversely correlated with the odds of favorable outcome after ischemic stroke. A previously proposed score for Stroke Prognostication Using Age and NIHSS Stroke Scale (SPAN) indicated that SPAN-100-positive patients (ie, age + NIHSS score = 100 or more) do not benefit from IV-tPA. If this finding holds true for endovascular therapy, this score can impact patient selection for such interventions. This study investigated whether a score combining age and NIHSS score can improve patients' selection for endovascular stroke therapy.

MATERIALS AND METHODS

The SPAN index was calculated for patients in the prospective Solitaire FR Thrombectomy for Acute Revascularization study: an international single-arm multicenter cohort for anterior circulation stroke treatment by using the Solitaire FR. The proportion with favorable outcome (90-day mRS score ≤2) was compared between SPAN-100-positive versus-negative patients.

RESULTS

Of the 202 patients enrolled, 196 had baseline NIHSS scores. Fifteen (7.7%) patients were SPAN-100-positive. There was no difference in the rate of successful reperfusion (Thrombolysis In Cerebral Infarction 2b or 3) between SPAN-100-positive versus -negative groups (93.3% versus 82.8%, respectively; P = .3). Stroke SPAN-100-positive patients had a significantly lower proportion of favorable clinical outcomes (26.7% versus 60.8% in SPAN-100-negative, P = .01). In a multivariable analysis, SPAN-100-positive status was associated with lower odds of favorable outcome (OR, 0.3; 95% CI, 0.1-0.9; P = .04). A higher baseline Alberta Stroke Program Early CT Score and a short onset to revascularization time also predicted favorable outcome in the multivariable analysis.

CONCLUSIONS

A significantly lower proportion of patients with a positive SPAN-100 achieved favorable outcome in this cohort. SPAN-100 was an independent predictor of favorable outcome after adjusting for time to treatment and the extent of preintervention tissue damage according to the Alberta Stroke Program Early CT Score.

Optimal Workflow and Process-Based Performance Measures for Endovascular Therapy in Acute Ischemic Stroke

Background and Purpose—

We report on workflow and process-based performance measures and their effect on clinical outcome in Solitaire FR Thrombectomy for Acute Revascularization (STAR), a multicenter, prospective, single-arm study of Solitaire FR thrombectomy in large vessel anterior circulation stroke patients.

Methods—

Two hundred two patients were enrolled across 14 centers in Europe, Canada, and Australia. The following time intervals were measured: stroke onset to hospital arrival, hospital arrival to baseline imaging, baseline imaging to groin puncture, groin puncture to first stent deployment, and first stent deployment to reperfusion. Effects of time of day, general anesthesia use, and multimodal imaging on workflow were evaluated. Patient characteristics and workflow processes associated with prolonged interval times and good clinical outcome (90-day modified Rankin score, 0–2) were analyzed.

Results—

Median times were onset of stroke to hospital arrival, 123 minutes (interquartile range, 163 minutes); hospital arrival to thrombolysis in cerebral infarction (TICI) 2b/3 or final digital subtraction angiography, 133 minutes (interquartile range, 99 minutes); and baseline imaging to groin puncture, 86 minutes (interquartile range, 24 minutes). Time from baseline imaging to puncture was prolonged in patients receiving intravenous tissue-type plasminogen activator (32-minute mean delay) and when magnetic resonance–based imaging at baseline was used (18-minute mean delay). Extracranial carotid disease delayed puncture to first stent deployment time on average by 25 minutes. For each 1-hour increase in stroke onset to final digital subtraction angiography (or TICI 2b/3) time, odds of good clinical outcome decreased by 38%.

Conclusions—

Interval times in the STAR study reflect current intra-arterial therapy for patients with acute ischemic stroke. Improving workflow metrics can further improve clinical outcome.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01327989.

Abstract T MP6: Angiographic Arteriovenous Shunting in Large Vessel Occlusion Strokes: Not an Ominous Sign

Background: The angiographic visualization of arteriovenous shunting (AVS) in large vessel occlusion strokes (LVOS) is thought to be a consequence of microcirculatory collapse in the setting of irreversible tissue injury and therefore may represent an ominous prognostic sign. We sought to establish the relationship between the presence of AVS on CT imaging characteristics and clinical outcomes in the Solitaire Flow Restoration Thrombectomy for Acute Revascularization (STAR) trial.

Methods: STAR Trial patients with complete angiographic images were categorized according to the presence (AVS+) or absence (AVS-) of AVS at the end of the thrombectomy procedure. Baseline variables were compared to assess for any significant differences amongst the two groups. The impact of AVS on pre- and post-treatment CT imaging and in the rates of revascularization (TICI 2b-3), symptomatic intracranial hemorrhage (sICH), good functional outcomes (90-day mRS≤2), and 90-day mortality was subsequently analyzed.

Results: There was no significant differences in terms of age, baseline NIHSS, gender, time to treatment, or glucose levels between the AVS+ (n=52) and the AVS- (n=116) patients (Table 1). AVS+ patients had a non-significant trend towards more proximal occlusions. The presence of AVS did not have any significant impact on the rates of favorable CT imaging on either pre-treatment (AVS- vs. AVS+ ASPECTS>7: 65.5 vs. 72%;p=0.47) or post-treatment (ASPECTS>7:45.6 vs. 51%;p=0.61) scans. Similarly, AVS was not associated with any significant differences in the rates of good outcome (58.6 vs. 65.4%;p=0.49), mortality (8.6 vs. 3.8%;p=0.35), sICH (1.7 vs. 1.9%;p=0.92), or recanalization (89.7 vs. 92.3%;p=0.78).

Conclusions: In contrast to the current belief, the angiographic visualization of AVS in LVOS patients does not appear to have any meaningful consequences in terms of infarct size or clinical outcomes and therefore should not influence treatment decisions.

Abstract T P50: ASTRAL-R score Predicts absence of Recanalization after Intravenous Thrombolysis in Acute Ischemic Stroke

Background: Intravenous thrombolysis (IVT) is the best proven recanalization treatment in acute ischemic stroke (AIS), but may be insufficient or of little value in certain patients. By predicting the probability of absence of recanalization after IVT, the decision for more aggressive revascularization treatment can be individualized with the goal to improve clinical outcome.

Aim: To derive and internally validate a predictive scoring system for absence of recanalization with IVT, using readily available variables in the prehospital and emergency room phase.

Methods: Data from prospective thrombolysis registries of four academic stroke centers were examined. Patients with arterial occlusion on acute imaging and repeat arterial assessment at 24hours were selected. Based on a logistic regression analysis, an integer-based score for each covariate of the fitted multivariate model was generated. The overall score was calculated as the sum of the weighted scores. In a patient with an ASTRAL-R score > 3, the likelihood of absence of recanalization was > 50%. The area under the receiver-operator curve was 0.65 in the derivation cohort.

Results: In 534 thrombolyzed AIS patients, five variables were identified as independent predictors of absence of recanalization: Acute glucose >7mmol/L (A), significant extracranial vessel STenosis (ST), decreased Range of visual fields (R), proximal Arterial occlusion (A) and altered Level of consciousness (L). An altered level of consciousness was weighted 2 and all other variables 1 point based on β-coefficients. In a patient with an ASTRAL-R score > 3, the likelihood of absence of recanalization was >50%. The score was highly predictive (OR 0.65, 95%CI 0.55-0.76) in the derivation cohort.

Conclusions: A simple 5-item ASTRAL-R score shows high prediction for absence of recanalization at 24hours in thrombolyzed AIS patients. If confirmed by external validation, planning for more aggressive revascularization strategies may facilitate through this tool.

Abstract T P26: Predictors of Clinical and Angiographic Outcomes in Acute Stroke Treatment: Subgroup Analysis From the Star Study

Endovascular acute stroke treatment (AIS) has changed dramatically last years. Stent retrievers are progressively substituting other devices and old practices like intra-arterial thrombolysis. We present the subgroup analysis of the largest prospective multicentre study using stent retrievers on the treatment of AIS. The study was realized in 14 high volume and experienced stroke centres in Europe, Canada and Australia. 202 patients harbouring anterior circulation occlusions were included within 8 hours after onset. All procedures were performed with balloon guiding catheter. We observed that the occlusion location did not change the successful (TICI 2b or 3) recanalization rates (ICA - 76.5% and MCA - 86.4%: p=0.187) or good clinical outcomes (mRS 0-2) (ICA - 47.2% and MCA - 61.3%: p=0.137). However, it was significant when we considered excellent (mRS 0-1) outcomes only (ICA - 25% and MCA - 47.5%: p=0.016). There were no differences concerning the previous use of rtPA on the angiographic (TICI scores) (p=1.0) or clinical (mRS) (p=0.564) outcomes. The anaesthetic management also did not influence the revascularization (p=0.7) or patient’s status (p=0.343). Angiographic collateral status determined using the ASITN/SIR grading system was significantly correlated to good clinical outcomes (Grades 0-2 and Grades3-4, p=0.034). Also the time from the stroke onset to groin puncture influence clinical progress (0-3h, 3-4.5h, over 4.5h: p=0.002). Multivariate regression analysis on prediction of good outcomes was significant for age (OR-0.93 (0.89, 0.97)), baseline NIHSS (OR-0.87(0.79, 0.96)), absence of haemorrhage (OR-5.01 (1.65, 15.16)), time to treatment (OR-0.62(0.45-0.83)) procedure performed under conscious sedation (OR4.83(1.78,13.11)) and successful recanalization (OR-3.37(1.12,10.14)). Early and efficient revascularization is ideal situation for AIS. Conscious sedation can save time for endovascular procedure using a stent retriever in experienced centers.

Abstract T MP8: The Thrive Score Strongly Predicts Outcomes in Patients Treated With the Solitaire Device in the Swift and Star Trials

Introduction: The THRIVE score strongly predicts clinical outcome, mortality, and risk of thrombolytic hemorrhage in ischemic stroke patients, and performs similarly well in patients receiving IV tPA, endovascular stroke treatment (EST), or no acute treatment. We recently validated the performance of the THRIVE score in the TREVO-2 trial of a third generation EST device, the Trevo device

Methods: We examined the relationship between THRIVE and clinical outcomes (good outcome [mRS 0-2] or death at 90 days) among patients in SWIFT and STAR. Receiver-Operator Characteristics (ROC) curve analysis was used to compare THRIVE score performance to other stroke prediction scores. Multivariable logistic regression was used to confirm the independence of THRIVE score from procedure-specific predictors (target vessel recanalization or device used in SWIFT) of outcome.

Results: THRIVE score strongly predicted good outcome (Figure, A) and death (Figure, B) among patients treated with the Solitaire device in SWIFT and STAR (Mantel-Haenztel Chi-square test for trend P<0.001 for good outcome, P=0.01 for death). In ROC curve comparisons, THRIVE was superior to SPAN-100 (P<0.001) and performed similarly to HIAT (P=0.98) and HIAT-2 (P=0.54). In logistic regression, THRIVE’s prediction of good outcome was not altered after controlling for recanalization (in all Solitaire patients) or after controlling for device used (in the SWIFT RCT).

Conclusions: The THRIVE score strongly predicts clinical outcome and mortality in patients treated with the Solitaire device in the SWIFT and STAR trials. The lack of interaction between THRIVE and procedure-specific elements such as vessel recanalization or device choice supports the use of the THRIVE score as an a priori selection criterion in stroke clinical trials.

Interventional neuroradiology of stroke, still not dead

Since the National Institute of Neurological Disorders and Stroke trial, intravenous thrombolysis has been gaining wide acceptance as the modality of treatment for acute embolic stroke, with a current therapeutic window of up to 4.5 h. Both imaging [with either magnetic resonance imaging (MRI) or computed tomography (CT)] and interventional techniques (thrombolysis and/or thrombectomy) have since improved and provided us with additional imaging of the penumbra using CT or MRI and more advanced thrombolysis or thrombectomy strategies that have been embraced in many centers dealing with patients with acute cerebral ischemia. These techniques, however, have come under scrutiny due to their accrued healthcare costs and have been questioned following major recent studies. These studies basically showed that interventional techniques were not superior to the traditional intravenous thrombolysis techniques and that penumbra imaging could not determine what patients would benefit from more aggressive (i.e., interventional) treatment. We discuss this in the light of the latest developments in both diagnostic and interventional neuroradiology and point out why further studies are needed in order to define the right choices for patients with acute stroke. Indeed, these studies were in part conducted with suboptimal patient recruitment strategies and did not always use the latest interventional techniques available today. So, while these studies may have raised some relevant questions, at the same time, definitive answers have not been given, in our opinion.

Diagnostic neuroradiology for the interventional neuroradiologist

In order to further improve the impact of the continuously evolving neurointerventional techniques, the interventional neuroradiologist needs to have at his disposal more powerful techniques to image the central nervous system. With the recent development of diagnostics techniques that are computed tomography and magnetic resonance based we are now able to assess not just morphology, but also physiology, physiopathology and function. This review discusses the place of diagnostic techniques in the evaluation that the interventional neuroradiologist hast to make when confronted with patients. We provide an overview of current techniques for the brain and spine.

Wall shear stress distribution of small aneurysms prone to rupture: a case-control study

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage after intracranial aneurysm rupture remains a serious condition. We performed a case-control study to evaluate the use of computed hemodynamics to detect cerebral aneurysms prone to rupture.

METHODS

Four patients with incidental aneurysms that ultimately ruptured (cases) were studied after initially being included in a prospective database including their 3-dimensional imaging before rupture. Ruptures were located in different arterial segments: M1 segment of the middle cerebral artery; basilar tip; posterior inferior cerebellar artery; and anterior communicating artery. For each case, 5 controls matched by location and size were randomly selected. An empirical cumulative distribution function of aneurysm wall shear stress percentiles was evaluated for every case and used to define a critical prone-to-rupture range. Univariate logistic regression analysis was then used to assess the individual risk of rupture.

RESULTS

A cumulative wall shear stress distribution characterizing a hemodynamic prone-to-rupture range for small-sized aneurysms was identified and fitted independent of the location. Sensitivity and specificity of the preliminary tests were 90% and 93%, respectively.

CONCLUSIONS

The wall shear stress cumulative probability function may be a potential predictor of small-sized aneurysm rupture.

Risk of Rupture of Small Anterior Communicating Artery Aneurysms Is Similar to Posterior Circulation Aneurysms

Background and Purpose—

According to the International Study of Unruptured Intracranial Aneurysms (ISUIA), anterior circulation (AC) aneurysms of <7 mm in diameter have a minimal risk of rupture. It is general experience, however, that anterior communicating artery (AcoA) aneurysms are frequent and mostly rupture at <7 mm. The aim of the study was to assess whether AcoA aneurysms behave differently from other AC aneurysms.

Methods—

Information about 932 patients newly diagnosed with intracranial aneurysms between November 1, 2006, and March 31, 2012, including aneurysm status at diagnosis, its location, size, and risk factors, was collected during the multicenter @neurIST project. For each location or location and size subgroup, the odds ratio (OR) of aneurysms being ruptured at diagnosis was calculated.

Results—

The OR for aneurysms to be discovered ruptured was significantly higher for AcoA (OR, 3.5 [95% confidence interval, 2.6–4.5]) and posterior circulation (OR, 2.6 [95% confidence interval, 2.1–3.3]) than for AC excluding AcoA (OR, 0.5 [95% confidence interval, 0.4–0.6]). Although a threshold of 7 mm has been suggested by ISUIA as a threshold for aggressive treatment, AcoA aneurysms <7 mm were more frequently found ruptured (OR, 2.0 [95% confidence interval, 1.3–3.0]) than AC aneurysms of 7 to 12 mm diameter as defined in ISUIA.

Conclusions—

We found that AC aneurysms are not a homogenous group. Aneurysms between 4 and 7 mm located in AcoA or distal anterior cerebral artery present similar rupture odds to posterior circulation aneurysms. Intervention should be recommended for this high-risk lesion group.

Intraoperative angiography reloaded: a new hybrid operating theater for combined endovascular and surgical treatment of cerebral arteriovenous malformations: a pilot study on 25 patients

BACKGROUND

Multimodality treatment suites for patients with cerebral arteriovenous malformations (AVM) have recently become available. This study was designed to evaluate feasibility, safety and impact on treatment of a new intraoperative flat-panel (FP) based integrated surgical and imaging suite for combined endovascular and surgical treatment of cerebral AVM.

METHODS

Twenty-five patients with AVMs to treat with combined endovascular and surgical interventions were prospectively enrolled in this consecutive case series. The hybrid suite allows combined endovascular and surgical approaches with intraoperative scanner-like imaging (XperCT®) and intraoperative 3D rotational angiography (3D-RA). The impact of intraoperative multimodal imaging on feasibility, workflow of combined interventions, surgery, and unexpected imaging findings were analyzed.

RESULTS

Twenty-five patients (mean age 38 ± 18.6 year) with a median Spetzler-Martin grade 2 AVM (range 1-4) underwent combined endovascular and surgical procedures. Sixteen patients presented with a ruptured AVM and nine with an unruptured AVM. In 16 % (n = 4) of cases, intraoperative imaging visualized AVM remnants ≤3 mm and allowed for completion of the resections in the same sessions. Complete resection was confirmed in all n = 16 patients who had follow-up angiography one year after surgery so far. All diagnostic and therapeutical steps, including angiographic control, were performed without having to move the patients

CONCLUSION

The hybrid neurointerventional suite was shown to be a safe and useful setup which allowed for unconstrained combined microsurgical and neuroradiological workflow. It reduces the need for extraoperative angiographic controls and subsequent potential surgical revisions a second time, as small AVM remnants can be detected with high security.

The role of unenhanced CT alone for the management of headache in an emergency department. A feasibility study

OBJECTIVE

To determine whether unenhanced CT alone could be sufficient for the screening of patients admitted with a suspicion of secondary headache in an emergency center.

MATERIAL AND METHODS

A feasibility study including consecutive patients admitted to our emergency department for acute non-traumatic headache, in whom a brain CT was required by the emergency physician, was conducted over a 3-month period of time. Patients with a suspicion of intracranial pathology, which can only be depicted by i.v. images (arterial dissection, venous thrombosis, or postoperative complication) were recorded but excluded from analysis. All patients underwent both unenhanced and i.v. enhanced cerebral CT, including CT angiography. Unenhanced CTs were reviewed by two radiologists, blinded to the clinical data, to the radiological reports and to the i.v. enhanced images. Unenhanced CT were sorted by the radiologists into three groups: (1) normal CT, (2) benign finding that could explain headache without need of injection of contrast media, (3) evidence of an intracranial pathology, requiring further imaging. Results were compared to i.v. enhanced CT images.

RESULTS

A brain CT was required in 105 patients (34 males, 71 females) during the study period, 74 (70%) of them met our inclusion criteria. Fifty-nine (80%) were sorted in group 1 (normal), four (5%) in group 2, 11 (15%) in group 3. No further finding that could explain acute headache was found on i.v. CT images in patients of group 1 or 2. A significant pathology was confirmed by i.v. CT in all patients of group 3.

CONCLUSION

This feasibility study suggests that a normal unenhanced CT might be sufficient to exclude the cause of headache in the initial screening of a selected group of patients admitted with cephalalgia. It compels researchers to perform further prospective studies to confirm the current data on a larger amount of patients.

Descriptor selection for banana accessions based on univariate and multivariate analysis

Our objective was to establish a minimum number of morphological descriptors for the characterization of banana germplasm and evaluate the efficiency of removal of redundant characters, based on univariate and multivariate statistical analyses. Phenotypic characterization was made of 77 accessions from Bahia, Brazil, using 92 descriptors. The selection of the descriptors was carried out by principal components analysis (quantitative) and by entropy (multi-category). Efficiency of elimination was analyzed by a comparative study between the clusters formed, taking into consideration all 92 descriptors and smaller groups. The selected descriptors were analyzed with the Ward-MLM procedure and a combined matrix formed by the Gower algorithm. We were able to reduce the number of descriptors used for characterizing the banana germplasm (42%). The correlation between the matrices considering the 92 descriptors and the selected ones was 0.82, showing that the reduction in the number of descriptors did not influence estimation of genetic variability between the banana accessions. We conclude that removing these descriptors caused no loss of information, considering the groups formed from pre-established criteria, including subgroup/subspecies.

Transvenous embolization of a ruptured deep cerebral arteriovenous malformation. A technical note

Ruptured cerebral arteriovenous malformations (AVMs) usually require treatment to avoid re-bleeding. Depending on the angioarchitecture and center strategy, the treatment can be surgical, endovascular, radiosurgical or combined methods. The classic endovascular approach is transarterial, but sometimes it is not always applicable. The transvenous approach has been described as an alternative for the endovascular treatment of small AVMs when arterial access or another therapeutic method is not possible. This approach can be considered when the nidus is small and if there is a single draining vein. We present a technical note on a transvenous approach for the treatment of a ruptured AVM in a young patient.

Diagnostic approach to cerebral aneurysms

Cerebral aneurysms are an important cause of morbidity and mortality due to their causal effect in non-traumatic subarachnoid hemorrhage. Neurosurgical progress in the 20th century helped to improve patient outcomes greatly. In recent years, techniques such as intravascular treatment by coiling and/or stenting have found an additional place in the management of the disease. With the development of less and less invasive surgical and endovascular techniques, there has also been a continuous development in imaging techniques that have led to our current situation where we dispose of CT and MR techniques that can help improve treatment planning greatly. CT is able to detect and together with its adjunct techniques CT angiography and CT perfusion, it can allow us to provide the physicians in charge with a detailed image of the aneurysm, the feeding vessels as well as the status of blood flow to the brain. Angiography has evolved by becoming the standard tool for guidance during decision making for whatever therapy is being envisioned be it endovascular procedures and or surgery and has even progressed more recently due to the development of so-called flat panel technology that now allows to acquire CT-like images during and directly after an intervention. Thus nowadays, the diagnostic and interventional techniques and procedures have become so much entwined as to be considered a whole.

Flow-diverting stent for ruptured intracranial dissecting aneurysm of vertebral artery

BACKGROUND

The treatment of ruptured dissecting aneurysms of the intracranial vertebral artery (VA) with parent vessel preservation is a challenge for neurosurgeons and interventional neuroradiologists.

OBJECTIVE

To propose an indication for flow-diverting treatment for reconstruction of a dissecting VA with acute subarachnoid hemorrhage.

METHODS

Two male patients transferred after acute subarachnoid hemorrhage and dissecting aneurysm on the V4 segment of the dominant VA. An occlusion test was not performed because of their poor clinical state. A flow-diverting stent represented by the Pipeline embolization device was suggested to both patients.

RESULTS

Three Pipeline embolization devices were deployed in each VA. One dissecting aneurysm was excluded immediately after 3 stents, and 1 patient had complete exclusion demonstrated at the 48-hour control. No morbidity directly related to the procedure was observed. No recanalization and no rebleeding occurred during the 3 months of follow-up.

CONCLUSION

A flow-diverting stent may be considered an option to treat ruptured dissecting aneurysms of the VA, providing remodeling of the parent vessel and complete exclusion of the aneurysm.

A DSA-based method using contrast-motion estimation for the assessment of the intra-aneurysmal flow changes induced by flow-diverter stents

BACKGROUND AND PURPOSE

Flow-diverter stents modify intra-aneurysmal blood flow and induce the progressive thrombosis of intracranial aneurysms followed by stable vascular reconstruction. The aim of this study was to report a new method for the appraisal of intracranial blood flow from DSA performed during endovascular treatment procedures.

MATERIALS AND METHODS

A cohort of 24 patients with unruptured IAs who underwent FDS implantation was prospectively recruited. Pre- and post-DSA sequences in combination with 3D rotational angiography were acquired. The quantification of arterial and intra-aneurysmal flow was accomplished by using an optical flow approach. Flow reduction was assessed by using a new metric termed the mean aneurysm flow amplitude ratio. The correlation between the MAFA ratio and the incidence of aneurysm thrombosis was assessed by using receiver operating characteristic analysis and the Fisher exact test when the optimum Youden index was found.

RESULTS

The quantification of flow was successfully achieved in 21 of 24 patients (87.5%). On the imaging follow-up, 18 aneurysms developed complete thrombosis (87.5%) and 3 displayed residual circulation (12.5%). The threshold analysis of the MAFA ratio significantly predicted thrombosis at 12 months below a threshold of 1.03 (P=.035). There was no significant correlation between the time for complete occlusion of the aneurysm and contrast stagnation inside the aneurysm after treatment (P>.05).

CONCLUSIONS

The MAFA ratio based on DSA flow quantification appears to be a reliable predictor for the assessment of stent treatment outcomes in this small study. These results open the door for perioperative flow quantification and provide indices that may help clinicians make appropriate intraprocedural decisions.

Diagnostic neuroradiology: Ready for the neuro-interventional age?

Acute cerebral ischemia or stroke is currently considered an emergency for which therapeutic options are available if the therapeutic window of 4.5 h is respected. Imaging modalities have progressed greatly over the last few decades, rendering ischemia detectable in the first hours after the event. However, in order for treatment to be efficacious it is necessary to speed up all the processes before the start of therapy. Thus, one must decrease the time to arrival at the hospital and to the radiological method that is to be employed (be it computed tomography or magnetic resonance imaging); only then will the medical or interventional techniques available fulfill their potential.

Use of stentrievers in acute stroke: tips, tricks, and current results

Stentrievers are stent-like devices used in the treatment of acute ischemic stroke. They have demonstrated efficacy in restoring the intracranial blood flow with low procedural times. This article is a synopsis of the available devices and different techniques. An extensive review of the literature summarizing all the data that have been published demonstrating their clinical impact and complications is also presented.

Retrospective multicenter study of Solitaire FR for revascularization in the treatment of acute ischemic stroke

BACKGROUND AND PURPOSE

The purpose of this study was to evaluate safety and efficacy of the Solitaire FR device in the treatment of patients with acute ischemic stroke secondary to large artery occlusion.

METHODS

We conducted a retrospective study of consecutive patients presenting with acute ischemic stroke treated with Solitaire FR as the first-line device to restore blood flow in 6 experienced European centers. This study was entirely funded and supported by Coviden Neurovascular. An independent Corelab determined modified Thrombolysis in Cerebral Infarction scores on the preprocedure and postprocedure angiograms. Complete revascularization was defined as modified Thrombolysis in Cerebral Infarction 2b or 3 post-Solitaire FR device use. Symptomatic intracranial hemorrhage was defined as parenchymal hemorrhage Type 2 associated with a decline of ≥ 4 points in the National Institutes of Health Stroke Scale score within 24 hours or causing death. Favorable functional outcome was considered as modified Rankin Scale score ≤ 2 at Day 90.

RESULTS

We studied 141 patients (mean age, 66 years; median National Institutes of Health Stroke Scale, 18); 74 patients received intravenous tissue-type plasminogen activator before endovascular treatment. Complete revascularization was achieved in 120 of 142 occlusion sites (85%) and good outcome in 77 of 141 (55%) patients. Good outcome was more frequent in patients treated with intravenous tissue-type plasminogen activator than in those without (66% versus 42%; P<0.01). Symptomatic intracranial hemorrhage was reported in 5 patients (4%) and 29 of 141 (20%) patients died or were lost during follow-up (3 cases).

CONCLUSIONS

This retrospective study with centralized evaluation shows that the use of Solitaire FR is safe and achieves good revascularization rates and functional outcomes in patients with acute ischemic stroke and large artery occlusion.

Stroke: high-field magnetic resonance imaging

Diagnostic modalities for the diagnosis of acute stroke have increased in number and quality. Magnetic resonance imaging has increasingly become a central tool for the management of patients with stroke. New sequences, such as diffusion and perfusion, provide insight into the infarcted core and the hypoperfused brain. The use of higher magnetic fields allows us to gain in signal strength, which can be used to improve imaging speed and/or resolution. Recent additional sequences allow perfusion without contrast and susceptibility-weighted imaging can help identify early bleeding. These new techniques should provide more information about the on going ischemic process.

Clipping of MCA aneurysms: how I do it

INTRODUCTION

Aneurysms located at the middle cerebral artery bifurcation remain a clear neurosurgical indication. We detail here the steps necessary to enable safe surgery for Sylvian fissure aneurysms.

METHODS

An angiogram with 3D reconstruction is obtained and reviewed intraoperatively, just prior to the skin incision. During the exposure, the cistern is kept open by small cottonoids, thereby avoiding brain retraction. Continuous monitoring of MEPs along with ICG microscopic angio-fluorescence allows for detection of vascular compromise. Intraoperative angiography with 3D reconstruction allows for immediate correction of less than satisfactory surgical outcome.

CONCLUSIONS

Careful planning of surgical strategy followed by a minimally invasive technique (with continuous neuro-monitoring) ensures safe surgery. The availability of intra-operative radiological guidance allows for optimal management.

Acute Spinal Epidural Hematoma and Cranial Interdural Hematoma Due to a Rupture of a Posterior Communicating Artery Aneurysm: Case Report

BACKGROUND AND IMPORTANCE:

We describe an unusual presentation of a ruptured aneurysm of the posterior communicating artery with an acute intracranial hematoma between the dural layers associated with an acute spinal epidural hematoma descending to L1.

CLINICAL PRESENTATION:

A 35-year-old woman presented 3 hours after ictus with a postcoital headache, neck stiffness, and bilateral abducens cranial nerve palsy. No other neurological deficits were present. Clinically, she had a subarachnoid hemorrhage World Federation of Neurosurgical Societies grade 1. CT scan demonstrates an acute subdural hematoma, extending from the right parasellar region, around the clivus, tentorium, and falx. Angio-CT showed a posterior communicating artery aneurysm and an anterior communicating artery aneurysm and an extension of the hematoma to the cervical spine. This justified a spinal and cerebral MRI that confirmed an extension of the hematoma to the epidural space at the cervical, thoracic, and lumbar levels. Three-dimensional digital subtraction angiography confirmed aneurysms on the right posterior communicating artery and on the anterior communicating artery. Both aneurysms were completely occluded by coiling. With reference to the concept of the cranial subdural compartment described in studies conducted using an electron microscope, this group of hematomas was classified as interdural.

CONCLUSION:

Ruptured aneurysm of the posterior communicating artery may cause cranial acute interdural hematoma with a typical subarachnoid hemorrhage clinical presentation, and it rarely can extend to spinal epidural space.

Combined use of pulsed arterial spin-labeling and susceptibility-weighted imaging in stroke at 3T

BACKGROUND AND PURPOSE

In acute stroke it is no longer sufficient to detect simply ischemia, but also to try to evaluate reperfusion/recanalization status and predict eventual hemorrhagic transformation. Arterial spin labeling (ASL) perfusion may have advantages over contrast-enhanced perfusion-weighted imaging (cePWI), and susceptibility weighted imaging (SWI) has an intrinsic sensitivity to paramagnetic effects in addition to its ability to detect small areas of bleeding and hemorrhage. We want to determine here if their combined use in acute stroke and stroke follow-up at 3T could bring new insight into the diagnosis and prognosis of stroke leading to eventual improved patient management.

METHODS

We prospectively examined 41 patients admitted for acute stroke (NIHSS >1). Early imaging was performed between 1 h and 2 weeks. The imaging protocol included ASL, cePWI, SWI, T2 and diffusion tensor imaging (DTI), in addition to standard stroke protocol.

RESULTS

We saw four kinds of imaging patterns based on ASL and SWI: patients with either hypoperfusion and hyperperfusion on ASL with or without changes on SWI. Hyperperfusion was observed on ASL in 12/41 cases, with hyperperfusion status that was not evident on conventional cePWI images. Signs of hemorrhage or blood-brain barrier breakdown were visible on SWI in 15/41 cases, not always resulting in poor outcome (2/15 were scored mRS = 0-6). Early SWI changes, together with hypoperfusion, were associated with the occurrence of hemorrhage. Hyperperfusion on ASL, even when associated with hemorrhage detected on SWI, resulted in good outcome. Hyperperfusion predicted a better outcome than hypoperfusion (p = 0.0148).

CONCLUSIONS

ASL is able to detect acute-stage hyperperfusion corresponding to luxury perfusion previously reported by PET studies. The presence of hyperperfusion on ASL-type perfusion seems indicative of reperfusion/collateral flow that is protective of hemorrhagic transformation and a marker of favorable tissue outcome. The combination of hypoperfusion and changes on SWI seems on the other hand to predict hemorrhage and/or poor outcome.

Carotid artery stenting: rationale, technique, and current concepts

Carotid stenosis is a major risk factor for stroke. With the aging of the general population and the availability of non-invasive vascular imaging studies, the diagnosis of a carotid plaque is commonly made in medical practice. Asymptomatic and symptomatic carotid stenoses need to be considered separately because their natural history is different. Two large randomized controlled trials (RCTs) showed the effectiveness of carotid endarterectomy (CEA) in preventing ipsilateral ischemic events in patients with symptomatic severe stenosis. The benefit of surgery is much less for moderate stenosis and harmful in patients with stenosis less than 50%. Surgery has a marginal benefit in patients with asymptomatic stenosis. Improvements in medical treatment must be taken into consideration when interpreting the results of these previous trials which compared surgery against medical treatment available at the time the trials were conducted. Carotid artery stenting (CAS) might avoid the risks associated with surgery, including cranial nerve palsy, myocardial infarction, or pulmonary embolism. Therefore and additionally to well-established indications of CAS, this endovascular approach might be a valid alternative particularly in patients at high surgical risk. However, trials of endovascular treatment of carotid stenosis have failed to provide enough evidence to justify routine CAS as an alternative to CEA in patients suitable for surgery. More data from ongoing randomized trials of CEA versus CAS will be soon available. These results will help determining the role of CAS in the management of patients with carotid artery stenosis.

[Hemorrhagic strokes in children: etiology and management]

Pediatric particularities and management of pediatric hemorrhagic strokes are reviewed. Etiologies of hemorrhagic strokes in children are quite different than in adults. Arterio-venous malformations are much more frequently encountered than aneurysms, cavernous malformations and other non structural causes. Modem imagery allows to diagnose the cause of the hemorrhage with a good security and the management is based on the association of neurosurgery, interventional neuroradiology and radiosurgery. These cases must be handled in specialized tertiary care hospital where these three modalities of treatment are available 24 hours/day.

Penumbra system: a novel mechanical thrombectomy device for large-vessel occlusions in acute stroke

BACKGROUND AND PURPOSE

Large IC artery occlusion is often resistant to recanalization. We present our initial experience with the PS.

MATERIALS AND METHODS

Presenting with a severe acute ischemic stroke, the first 27 consecutive patients were considered for thromboaspiration therapy and retrospective data base analysis. All patients received standard thrombectomy treatment as monotherapy or in combination with thrombolysis or IC stent placement. The primary end point was revascularization of the target vessel to grade 2 or 3 on the TICI scale. Secondary end points were improvement of >4 points on the NIHSS score at discharge and favorable outcome, and improvement in overall mortality at 3 months and in sICH- and procedure-related adverse events.

RESULTS

At baseline, the mean age was 66 +/- 14 years and the mean NIHSS score was 14 +/- 7. The anterior circulation was affected in 23 patients, and there were 4 basilar artery occlusions. Intracranial stent placement was performed in 4 patients. A recanalization to TICI 2 or 3 was achieved in 25 patients (93%). None of the patients developed sICH. At hospital discharge, 15 patients (56%) had an NIHSS improvement of >4 and 13 patients (48%) had an mRS score of <2 at 3 months. There was a significant correlation between complete vessel recanalization and favorable outcome. The all-cause mortality at 3 months was 11%.

CONCLUSIONS

The PS showed a high potential for recanalization of acute thromboembolic occlusions of the large cerebral arteries. Complete recanalization was strongly correlated with good clinical outcome.

Magnetic resonance imaging of infections of the white matter

Infections of the nervous system are a common and serious occurrence. Neuroimaging has allowed to improve early detection and thus to initiate treatment earlier. Magnetic resonance (MR) imaging has become the method of choice in investigating a patient with suspicion of an infection of the central nervous system. Newer modalities such as MR spectroscopy and MR diffusion and perfusion will further help to improve diagnostic accuracy of the technique. For the investigation of infections of white matter, techniques such as diffusion imaging are essential.

Magnetic resonance imaging in multiple sclerosis

OBJECTIVES

multiple sclerosis (MS) is an inflammatory disease of unknown origin affecting the central nervous system. Magnetic resonance imaging (MRI) plays an increasingly important role in its diagnosis and further monitoring of disease progress.

METHODS

the typical MRI appearance of MS on conventional MRI sequences and current diagnostic criteria for MS are discussed. Advanced imaging techniques are reviewed with respect to application in MS. Finally, the atypical variants of MS are briefly reviewed.

CONCLUSIONS

although MRI is not intended and will not replace clinical assessment in MS, the recognized MRI criteria may aid in establishing an earlier and more accurate diagnosis of MS in the context of a clinical suspicion or clinically isolated syndrome. In addition, MRI might contribute to rule out differential diagnoses for MS. Moreover, MRI may be used to monitor the evolution of MS and in pharmaceutical trials. Advanced imaging techniques might, in the future, further characterize MS lesion subtypes and potentially guide tailored therapy.

Dural arteriovenous fistulas draining into the petrosal vein or bridging vein of the medulla: possible homologs of spinal dural arteriovenous fistulas. Clinical article

OBJECT

Dural arteriovenous fistulas (DAVFs) with leptomeningeal venous reflux generally pose a high risk of aggressive manifestations including hemorrhage. Among DAVFs, there is a peculiar type that demonstrates direct drainage into the bridging vein rather than the dural venous sinus. The purpose of this study was to investigate the characteristics of DAVFs that drain directly into the petrosal vein or the bridging vein of the medulla oblongata.

METHODS

Eleven consecutive cases of DAVFs that drained directly into the petrosal vein and 6 that drained directly into the bridging vein of the medulla were retrospectively reviewed. These cases were evaluated and/or treated at Hospital de Bicêtre in Paris, France, over a 27-year period. A review of previously reported cases was also performed.

RESULTS

Both of these "extrasinusal"-type DAVFs demonstrated very similar characteristics. There was a significant male predominance (p < 0.001) for this lesion, and a significantly higher incidence of aggressive neurological manifestations including hemorrhage or venous hypertension than in DAVFs of the transverse-sigmoid or cavernous sinus (p < 0.001). This finding was considered to be attributable to leptomeningeal venous reflux. Regarding treatment, endovascular embolization (either transarterial or transvenous) is frequently difficult, and surgery may be an effective therapeutic choice in many instances.

CONCLUSIONS

Embryologically, both the petrosal vein and the bridging vein of the medulla are cranial homologs of the spinal cord emissary bridging veins that drain the pial venous network. The authors believe that DAVFs in these locations may be included in a single category with spinal DAVFs because of their similar clinical characteristics.

Arterial spin-labeling MRI perfusion in tuberous sclerosis: correlation with PET

Neuroimaging using magnetic resonance imaging (MRI) is required for the investigation of surgically intractable epilepsy. In addition to the standard MRI techniques, perfusion sequences can be added to improve visualization of the underlying pathological changes. Also, as arterial spin-labeling (ASL) MRI perfusion does not require contrast administration, it may even be advantageous in these patients. We report here on three patients with epilepsy and tuberous sclerosis who underwent brain MRI with ASL and positron emission tomography (PET), both of which were found to correlate with each other and with electrophysiological data.

Extracranial vertebral artery involvement in neurofibromatosis type I. Report of four cases and literature review

SUMMARY

Neurofibromatosis type 1 (NF-1) is one of the most common inherited diseases and as an autosomal dominant genetic disorder results from NF-1 gene mutation with 100% penetration and wide phenotypic variability. The disease can involve a wide variety of tissues derived from all three embryonic layers. NF-1 vasculopathy has been described primarily in peripheral arteries, but arteries supplying the CNS may also be involved. Of those, extracranial vertebral involvement is the commonest and most important. A series of four patients with NF-1 and vascular disease of the vertebral artery is described with a review of the pathophysiology, vascular phenotypes, their management and the pertinent literature.

Magneto-optical evidence of double exchange in a percolating lattice

Substituting Eu by Ca in ferromagnetic EuB6 leads to a percolation limited magnetic ordering. We present and discuss magneto-optical data of the Eu(1-x)Ca(x)B6 series, based on measurements of the reflectivity R(omega) from the far infrared up to the ultraviolet, as a function of temperature and magnetic field. Via the Kramers-Kronig transformation of R(omega) we extract the complete absorption spectra of samples with different values of x. The change of the spectral weight in the Drude component by increasing the magnetic field agrees with a scenario based on the double-exchange model, and suggests a crossover from a ferromagnetic metal to a ferromagnetic Anderson insulator upon increasing Ca content at low temperatures.

Colloidal carriers for benzathine penicillin G: nanoemulsions and nanocapsules

The main purpose of this work is to formulate benzathine penicillin G nanoemulsion and nanocapsules, to evaluate their physicochemical and stabilising characteristics, and to determine their antimicrobial activity and penicillin in vitro release kinetics. Nanoemulsions were produced by the spontaneous emulsification approach and nanocapsules of poly (D,L-lactic acid-co-glycolic acid) polymer (PLGA) were prepared by the method of interfacial deposition of a pre-formed polymer. A 207+/-8 nm mean diameter nanoemulsion formulation maintained stability for more than 5 months at 4 degrees C. Stable nanocapsules with 224+/-58 nm mean diameter were obtained, which remained stabilised over 120 days at 4 degrees C. The penicillin encapsulation ratio in the nanocapsules was 85%. The in vitro release profiles indicated that penicillin released from the nanoemulsion was similar to the one observed from nanocapsules. However it can be clearly deduced from the in vitro kinetic analysis that the antibiotic cannot be protected in colloidal delivery systems. Nevertheless, stable formulations obtained in this investigation supply a potential dosage form to encapsulate more easily soluble drugs.