Unruptured intracranial aneurysm growth trajectory: occurrence and rate of enlargement in 520 longitudinally followed cases

OBJECTIVE

As imaging technology has improved, more unruptured intracranial aneurysms (UIAs) are detected incidentally. However, there is limited information regarding how UIAs change over time to provide stratified, patient-specific UIA follow-up management. The authors sought to enrich understanding of the natural history of UIAs and identify basic UIA growth trajectories, that is, the speed at which various UIAs increase in size.

METHODS

From January 2005 to December 2015, 382 patients diagnosed with UIAs (n = 520) were followed up at UCLA Medical Center through serial imaging. UIA characteristics and patient-specific variables were studied to identify risk factors associated with aneurysm growth and create a predicted aneurysm trajectory (PAT) model to differentiate aneurysm growth behavior.

RESULTS

The PAT model indicated that smoking and hypothyroidism had a large effect on the growth rate of large UIAs (≥ 7 mm), while UIAs < 7 mm were less influenced by smoking and hypothyroidism. Analysis of risk factors related to growth showed that initial size and multiplicity were significant factors related to aneurysm growth and were consistent across different definitions of growth. A 1.09-fold increase in risk of growth was found for every 1-mm increase in initial size (95% CI 1.04-1.15; p = 0.001). Aneurysms in patients with multiple aneurysms were 2.43-fold more likely to grow than those in patients with single aneurysms (95% CI 1.36-4.35; p = 0.003). The growth rate (speed) for large UIAs (≥ 7 mm; 0.085 mm/month) was significantly faster than that for UIAs < 3 mm (0.030 mm/month) and for males than for females (0.089 and 0.045 mm/month, respectively; p = 0.048).

CONCLUSIONS

Analyzing longitudinal UIA data as continuous data points can be useful to study the risk of growth and predict the aneurysm growth trajectory. Individual patient characteristics (demographics, behavior, medical history) may have a significant effect on the speed of UIA growth, and predictive models such as PAT may help optimize follow-up frequency for UIA management.

Abstract TMP62: Emergency Triage to Predict Collaterals in Acute Ischemic Stroke: Imaging Bests Clinical Factors in the STRATIS Registry

Background: Collateral grade is an established determinant of outcomes in acute ischemic stroke (AIS). The triage, workflow and therapeutic options for AIS may be tailored to collaterals and identifying key predictors of collateral status may therefore be crucial. We hypothesized that degree of collateral circulation prior to endovascular therapy in AIS may be predicted at the time of initial patient evaluation and triage.

Methods: The STRATIS Registry showed that timelines, technical, and functional outcomes could be effectively attained in a large real-world cohort of endovascular therapy. Baseline clinical and imaging predictors of core lab adjudicated collateral grade (ASITN) by conventional angiography were determined, using multivariate modeling.

Results: 586 STRATIS subjects (67.5 ± 15.2 years, 52.7% male) presenting with AIS at 147.4 ± 101.8 min from symptom onset (TFSO) and median NIHSS score 17.0 (range 8.0,30.0) were analyzed. Collateral grade was poor (ASITN 0-1) in 81, moderate (ASITN 2) in 297 and good (ASITN 3-4) in 208. Baseline stroke severity inversely correlated with collaterals (NIHSS per point, OR 0.946, 0.916-0.977, p=0.001), yet no clinical variables such as age, sex or co-morbidities were predictive of collateral status. Less severe ASPECTS at imaging triage (median 9, range 2-10) was associated with better collateral grade (ASITN 0-1, median 7 (2-10); ASITN 2, 8 (3-10); ASITN 3-4, 9 (5-10), p<0.001) and the strongest predictor of collaterals during triage (per point, OR 1.608, 1.399-1.849, p<0.001). Interestingly, the predictive nature of ASPECTS was not modified by TFSO (p=NS). Specific ASPECTS regions (all cortical M1-M6, but no subcortical) affected by early ischemia were also predictive of collateral grade. In particular, insular ASPECTS changes at imaging triage was the strongest predictor of collateral grade (ASITN 0-1, 53/66 (80.3%); ASITN 2, 139/258 (53.9%); ASITN 3-4, 41/194 (21.1%), p<0.001).

Conclusions: Imaging, using only ASPECTS, during triage strongly predicts collateral grade, irrespective of time from symptom onset. Clinical variables, however, may not be used to accurately predict collaterals in the real-world practice of endovascular therapy.

Abstract TP287: Efficient Multimodal-MRI versus CT Selection for Anterior Circulation Large Vessel

Background: Prompt diagnosis and revascularization of large vessel occlusion ischemic stroke is associated with better functional outcome. While both MRI and CT modalities are current standard of care options for initial imaging, and MR imaging provides greater lesion conspicuity and spatial resolution to inform management, few series have yet demonstrated that multimodal MR may be performed speedily and efficiently in AIS-LVO patients.

Methods: In a prospectively maintained Comprehensive Stroke Center Registry, we analyzed all anterior circulation LVO thrombectomy patients: 1) arriving directly by EMS transport from the field, 2) with initial NIHSS ≥6, between 2012-2017. Throughout this period, imaging policy was multimodal MRI (including DWI/GRE/MRA w/wo PWI) as the initial evaluation in all patients without contraindications, and multimodal CT (including CT with CTA, w/wo CTP) in the remainder. Achieved process times were compared with national recommendations for door-to-needle (45m, AHA/ASA Target Stroke) and door-to-puncture (90m, SVIN).

Results: Among 106 LVO thrombectomy patients, MRI was used in 62.3% and CT in 37.7%. MRI and CT patients were similar in age, 72.5 v 71.3y; severity (NIHSS) 16.4 v 18.2); and IV tPA door-to-needle times, median 45 vs 46 mins. However, MRI patients had longer onset-to-door times, median 100 vs 50 mins. From Jan 2012-Dec2014, in MRI vs CT groups, median door-to-imaging times were 20 min vs 18 min, p=0.88 and door-to-puncture times 102 vs 93 min, p=0.39. From Jan 2015-Dec2017, after the publication of the positive thrombectomy trials and endorsement of endovascular stroke treatment in US guidelines, in MRI vs CT groups, median door-to-imaging times were 17 min vs 17 min (p=0.93) and door-to-groin puncture 86 vs 71 min (p=0.02). There was no difference in functional outcome (mRS 0-2) between groups.

Conclusions: Optimized imaging processes enable acute AIS-LVO patients to be evaluated by multimodal MR with care speeds faster than national recommendations for door-to-needle and door-to-puncture times. While some patients have absolute contraindications to high magnetic fields, MRI, with its greater pathophysiologic insight, remains a highly viable primary imaging strategy in acute ischemic stroke patients.

Abstract WP62: Imaging With CT Perfusion Prior to Endovascular Therapy in STRATIS: Time to Rethink?

Background: Different neuroimaging triage strategies, including CT perfusion (CTP), are commonly used prior to endovascular therapy, often tailoring imaging approaches based on time from symptom onset. We analyzed whether the acquisition of CTP prior to endovascular therapy in STRATIS was related to clinical outcomes and if any possible link was noted based on time duration from symptom onset.

Methods: The STRATIS Core Lab analyzed all pre-procedural imaging in STRATIS, including the use of CTP. Acquisition of pre-procedural CTP was analyzed with respect to 90-day modified Rankin Score (mRS) clinical outcomes. Subgroup analyses explored whether this relationship was different in the 0-6 versus 6-8 hour interval from symptom onset.

Results: Among 984 subjects analyzed in STRATIS, 264 had pre-procedural CTP acquired by the imaging Core Laboratory. No association between CTP acquisition and mRS outcomes at 90 days was observed in the overall study cohort. However, among subjects treated over 6 hours from onset (n=119), a trend toward better outcomes was observed in those with CTP acquisition compared to those without (adjusted common odds ratio 1.86, p=0.092). This association was not present in subjects treated within 6 hours from onset (adjusted common odds ratio 1.10, p=0.498) (Figure).

Conclusions: Real-world data from STRATIS reveal that good clinical outcomes after endovascular therapy are not directly contingent on obtaining pre-procedural CTP. Subgroup analyses provide novel data that CTP may not be necessary 0-6 hours from onset, yet CTP may be linked with better outcomes in patients presenting after 6 hours.

Abstract TP73: Perfusion Values in Ischemic Core Depend on Time from Onset in Acute Stroke

Introduction: Infarct core in perfusion imaging is defined by rCBF regardless of time from onset.

Hypothesis: Perfusion values and optimal perfusion thresholds for ischemic core depend on onset-to-imaging time.

Methods: Prospectively collected date for consecutive patients treated with IV t-PA and/or endovascular thrombectomy was analyzed retrospectively. Inclusion criteria were (1) patients with ICA or M1 occlusion (2) underwent both DWI and PWI (3) onset time was clear. Ten places of ROI were set in the same place of ADC and PWI images. These ROI were separated into two groups; low ADC (ADC<620) and normal ADC area (ADC>620). In each area we investigated relationship between time to imaging from onset and each PWI values (rCBF, rCBV, MTT and Tmax). ROC curve analysis for ADC<620 was also performed and compared AUC of early (time from onset to imaging <180 min) and late group (>180 min).

Results: Sixty-six patients meet inclusion criteria and 660 ROI was analyzed. 164 ROI were low ADC and 496 ROI were normal ADC. There were statistically significant relationships between time from onset to imaging and rCBF (p=0.0051), rCBV (p<0.0001), MTT (p=0.0001) and Tmax (p<0.0001) in low ADC area. In contrast, no relationship was found in normal ADC area between time and each MRP values. ROC analysis for ADC<620 showed rCBF had the highest AUC. However, AUC in late group was significantly higher than early group (0.927 vs 0.850, p=0.0055) and optimal thresholds was different between early and late group.

Conclusions: Perfusion values on PWI depend on time only in low ADC area. The accuracy and optimal thresholds for ischemic core in perfusion image depend on time.

Abstract WP174: Frequency, Predicators, and Outcomes of Pre-Intervention Thrombus Migration in Patients With Acute Ischemic Stroke Due to Large Vessel Occlusion

Background: In patients presenting with acute ischemic stroke (AIS) due to large vessel occlusion (LVO), between initial CTA/MRA and catheter angiography performed for intervention, the occlusive thrombus may persist unchanged, fragment and migrate distally, or resolve completely, with or without bridging intravenous fibrinolytic treatment. The frequency, predictors, and outcomes of pre-intervention thrombus migration not been well delineated.

Methods: We analyzed a prospectively maintained registry of AIS-LVO patients at an academic medical center over a 2.8 year period (Dec 2014-Oct 2017). Comparing occlusion sites on arrival CTA/MRA with immediately following interventional angiogram, patients were classified as having: 1) thrombus persistence (TP), 2) thrombus migration (TM), or 3) thrombus resolution (TR).

Results: In the 220 patients, mean age was 70.7, 42.7% were female, NIHSS was 13.8, onset to first imaging was 156 minutes, and initial occlusion sites on MRA/CTA were: ICA-20.5%; MCA-67.3%; VA/BA-12.3%. Frequencies of thrombus evolution patterns were: TP-59.5%; TM-30.5%; TR-10.0%. On multivariate analysis, independent predictors of TM were: higher NIHSS (OR 1.06 per 1 pt), cardioembolic mechanism (OR 2.40), and longer time from last known well to first CTA/MRA imaging (OR 1.08 per 60 min). While rates of substantial reperfusion (TICI 2b-3) were similar (85.2% vs 83.7%), patients with TM rather than TP had lower rates of excellent reperfusion (TICI 2C-3), 24.1% vs 44.2%, p = 0.02. Symptomatic intracranial hemorrhage occurred more often in TM than TP, 17.9% vs 8.4%, p = 0.05. In multivariate analysis, TM was independently associated with reduced rates of good functional outcome (mRS 0-2), both at discharge (OR 0.41, 95% CI 0.19 to 0.90; p=0.03) and at 3 months (OR 0.43, 95% CI 0.19 to 0.94; p=0.03).

Conclusions: Early TM between initial noninvasive imaging and interventional angiography occurs in nearly one-third of patients, is paradoxically associated with poorer outcomes, including more symptomatic hemorrhage and reduced final functional independence. Better understanding of dynamic clot changes early after arrival and their effects on outcome may aid further development of reperfusion therapeutics.

Abstract WP13: Time to Treatment With Endovascular Reperfusion Therapy and Outcome From Acute Ischemic Stroke in the National US GWTG-Stroke Population

Background: Randomized trials have shown the benefit of endovascular reperfusion therapy (ERT) in acute ischemic stroke (AIS) is time dependent. However, generalizability to routine practice is uncertain; and modest sample sizes have limited characterization of the degree to which onset to treatment time influences outcome from ERT.

Methods: We analyzed data of 6756 AIS patients treated with ERT at 231 hospitals between January 2015 to December 2016. Multivariable logistic regression modeling was conducted to evaluate the independent impact of onset to puncture (OTP) and door to puncture (DTP) time on efficacy and safety outcomes.

Results: Among the 6756 patients, median age was 71, 51.2% were female, and NIHSS was 17 (IQR 12-22). Median OTP was 230m (IQR 170-305) and DTP 87m (IQR 62-116). Substantial reperfusion (TICI 2b-3) was in 85.9%. At discharge, 36.9% had independent ambulation, 27.8% were discharged to home, and 23.0% were functionally independent (mRS 0-2). Symptomatic intracranial hemorrhage (sICH) occurred in 6.7% and in-hospital mortality/hospice in 19.6%. For OTP, time-outcome relationships were nonlinear, with steeper slope in 0-270m than 271-480m (see Table and Figure). DTP showed a similar nonlinear time-outcome relationship, with steeper benefit decline in the 30-120m than 121-180m period.

Conclusions: In this national registry, faster endovascular therapy start, after onset and after arrival, was associated with better ambulation and functional independence at discharge, and reduced sICH and mortality/hospice. These findings support intensive efforts to accelerate hospital presentation and endovascular treatment in patients with stroke.

Abstract TP272: Air versus Ground Transport for Interhospital Transfer Prior to Endovascular Stroke Treatment

Introduction: Interhospital transfer for endovascular treatment of large vessel occlusion (LVO) stroke results in significant delays and worse outcomes. We hypothesized that interhospital patient transfer using air transport would result in shorter transit times compared to ground ambulance.

Methods: Subjects from the STRATIS registry that underwent interhospital transfer for endovascular treatment were separated by air transport vs. ground ambulance transport and analyzed by transfer distance. The primary endpoint was transfer-time, calculated as the time from imaging at the initial hospital to arrival at the treating hospital. Also assessed was travel-time, calculated as time of departure from the initial hospital to arrival at the treating hospital.

Results: There were 232 subjects from 41 sites. Mean transfer-time for all air subjects (n=118) was 147.1 min, and for all ground subjects (n=114) was 130.0 min (p=0.019). Mean travel-time was 45.0 min for air transport and 40.2 min for ground transport (p=0.239); though the average travel distance was longer for air (65.5 miles) vs. ground (27.6 miles; p<0.001). When analyzed by distance, there was no difference between air and ground transfer-time except transfers less than 20 miles, which favored ground transportation (154.4 min vs. 119.5 min; p=0.015; see table). The lack of advantage for air transport may be accounted for by the time between imaging and departure from the initial hospital (mean 89.4 vs. 101.6 min; p=0.075), reflecting additional logistics and/or reduced availability of air transport.

Conclusions: In this large, real-world study, interhospital transfer via air transport did not result in faster transfer times compared to ground ambulance. In fact, there was an advantage to ground transportation for distances of less than 20 miles. These results suggest that ground ambulance should routinely be used for interhospital transfer of stroke patients for travel less than 20 miles.

Selective middle cerebral artery occlusion in the rabbit: Technique and characterization with pathologic findings and multimodal MRI

BACKGROUND

A reliable animal model of ischemic stroke is vital for pre-clinical evaluation of stroke therapies. We describe a reproducible middle cerebral artery (MCA) embolic occlusion in the French Lop rabbit characterized with multimodal MRI and histopathologic tissue analysis.

NEW METHOD

Fluoroscopic-guided microcatheter placement was performed in five consecutive subjects with angiographic confirmation of MCA occlusion with autologous clot. Multimodal MRI was obtained prior to occlusion and up to six hours post after which repeat angiography confirmed sustained occlusion. The brain was harvested for histopathologic examination.

RESULTS

Angiography confirmed successful MCA catheterization and durable (>6 h) MCA occlusion in all animals. There was increase of ADC volume over time and variable final core volume presumably related to individual variation in collateral flow. FLAIR hyperintensity indicative of cytotoxic edema and parenchymal contrast enhancement reflective of blood brain barrier disruption was observed over time. Tissue staining of the ischemic brain showed edema and structural alterations consistent with infarction.

COMPARISON WITH EXISTING METHODS

This study describes a technique of selective catheterization and embolic occlusion of the MCA in the rabbit with MRI characterization of evolution of ischemia in the model.

CONCLUSIONS

We demonstrate the feasibility of a rabbit model of embolic MCA occlusion with angiographic documentation. Serial MR imaging demonstrated changes comparable to those observed in human ischemic stroke, confirmed histopathologically.

Meso-Scale Particle Image Velocimetry Studies of Neurovascular Flows In Vitro

Particle image velocimetry (PIV) is used in a wide variety of fields, due to the opportunity it provides for precisely visualizing and quantifying flows across a large spatiotemporal range. However, its implementation typically requires the use of expensive and specialized instrumentation, which limits its broader utility. Moreover, within the field of bioengineering, in vitro flow visualization studies are also often further limited by the high cost of commercially sourced tissue phantoms that recapitulate desired anatomical structures, particularly for those that span the mesoscale regime (i.e., submillimeter to millimeter length scales). Herein, we present a simplified experimental protocol developed to address these limitations, the key elements of which include 1) a relatively low-cost method for fabricating mesoscale tissue phantoms using 3-D printing and silicone casting, and 2) an open-source image analysis and processing framework that reduces the demand upon the instrumentation for measuring mesoscale flows (i.e., velocities up to tens of millimeters/second). Collectively, this lowers the barrier to entry for nonexperts, by leveraging resources already at the disposal of many bioengineering researchers. We demonstratethe applicability of this protocol within the context of neurovascular flow characterization; however, it is expected to be relevant to a broader range of mesoscale applications in bioengineering and beyond.

Penumbral imaging and functional outcome in patients with anterior circulation ischaemic stroke treated with endovascular thrombectomy versus medical therapy: a meta-analysis of individual patient-level data

BACKGROUND

CT perfusion (CTP) and diffusion or perfusion MRI might assist patient selection for endovascular thrombectomy. We aimed to establish whether imaging assessments of irreversibly injured ischaemic core and potentially salvageable penumbra volumes were associated with functional outcome and whether they interacted with the treatment effect of endovascular thrombectomy on functional outcome.

METHODS

In this systematic review and meta-analysis, the HERMES collaboration pooled patient-level data from all randomised controlled trials that compared endovascular thrombectomy (predominantly using stent retrievers) with standard medical therapy in patients with anterior circulation ischaemic stroke, published in PubMed from Jan 1, 2010, to May 31, 2017. The primary endpoint was functional outcome, assessed by the modified Rankin Scale (mRS) at 90 days after stroke. Ischaemic core was estimated, before treatment with either endovascular thrombectomy or standard medical therapy, by CTP as relative cerebral blood flow less than 30% of normal brain blood flow or by MRI as an apparent diffusion coefficient less than 620 μm²/s. Critically hypoperfused tissue was estimated as the volume of tissue with a CTP time to maximum longer than 6 s. Mismatch volume (ie, the estimated penumbral volume) was calculated as critically hypoperfused tissue volume minus ischaemic core volume. The association of ischaemic core and penumbral volumes with 90-day mRS score was analysed with multivariable logistic regression (functional independence, defined as mRS score 0-2) and ordinal logistic regression (functional improvement by at least one mRS category) in all patients and in a subset of those with more than 50% endovascular reperfusion, adjusted for baseline prognostic variables. The meta-analysis was prospectively designed by the HERMES executive committee, but not registered.

FINDINGS

We identified seven studies with 1764 patients, all of which were included in the meta-analysis. CTP was available and assessable for 591 (34%) patients and diffusion MRI for 309 (18%) patients. Functional independence was worse in patients who had CTP versus those who had diffusion MRI, after adjustment for ischaemic core volume (odds ratio [OR] 0·47 [95% CI 0·30-0·72], p=0·0007), so the imaging modalities were not pooled. Increasing ischaemic core volume was associated with reduced likelihood of functional independence (CTP OR 0·77 [0·69-0·86] per 10 mL, p_interaction=0·29; diffusion MRI OR 0·87 [0·81-0·94] per 10 mL, p_interaction=0·94). Mismatch volume, examined only in the CTP group because of the small numbers of patients who had perfusion MRI, was not associated with either functional independence or functional improvement. In patients with CTP with more than 50% endovascular reperfusion (n=186), age, ischaemic core volume, and imaging-to-reperfusion time were independently associated with functional improvement. Risk of bias between studies was generally low.

INTERPRETATION

Estimated ischaemic core volume was independently associated with functional independence and functional improvement but did not modify the treatment benefit of endovascular thrombectomy over standard medical therapy for improved functional outcome. Combining ischaemic core volume with age and expected imaging-to-reperfusion time will improve assessment of prognosis and might inform endovascular thrombectomy treatment decisions.

FUNDING

Medtronic.

Reperfusion after ischemic stroke is associated with reduced brain edema

Rapid revascularization is highly effective for acute stroke, but animal studies suggest that reperfusion edema may attenuate its beneficial effects. We investigated the relationship between reperfusion and edema in patients from the Echoplanar Imaging Thrombolysis Evaluation Trial (EPITHET) and Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE) cohorts. Reperfusion percentage was measured as the difference in perfusion-weighted imaging lesion volume between baseline and follow-up (day 3-5 for EPITHET; day 6-8 for MR RESCUE). Midline shift (MLS) and swelling volume were quantified on follow-up MRI. We found that reperfusion was associated with less MLS (EPITHET: Spearman ρ = -0.46; P < 0.001, and MR RESCUE: Spearman ρ = -0.49; P < 0.001) and lower swelling volume (EPITHET: Spearman ρ = -0.56; P < 0.001, and MR RESCUE: Spearman ρ = -0.27; P = 0.026). Multivariable analyses performed in EPITHET and MR RESCUE demonstrated that reperfusion independently predicted both less MLS (ß coefficient = -0.056; P = 0.025, and ß coefficient = -0.38; P = 0.028, respectively) and lower swelling volumes (ß coefficient = -4.7; P = 0.007, and ß coefficient = -10.7; P = 0.009, respectively), after adjusting for age, sex, NIHSS, admission glucose and follow-up lesion size. Taken together, our data suggest that even modest improvement in perfusion is associated with less brain edema in EPITHET and MR RESCUE.

Relative cerebral blood volume is associated with collateral status and infarct growth in stroke patients in SWIFT PRIME

We aimed to evaluate how predefined candidate cerebral perfusion parameters correlate with collateral circulation status and to assess their capacity to predict infarct growth in patients with acute ischemic stroke (AIS) eligible for endovascular therapy. Patients enrolled in the SWIFT PRIME trial with baseline computed tomography perfusion (CTP) scans were included. RAPID software was used to calculate mean relative cerebral blood volume (rCBV) in hypoperfused regions, and hypoperfusion index ratio (HIR). Blind assessments of collaterals were performed using CT angiography in the whole sample and cerebral angiogram in the endovascular group. Reperfusion was assessed on 27-h CTP; infarct volume was assessed on 27-h magnetic resonance imaging/CT scans. Logistic and rank linear regression models were conducted. We included 158 patients. High rCBV ( p = 0.03) and low HIR ( p = 0.03) were associated with good collaterals. A positive association was found between rCBV and better collateral grades on cerebral angiography ( p = 0.01). Baseline and 27-h follow-up CTP were available for 115 patients, of whom 74 (64%) achieved successful reperfusion. Lower rCBV predicted a higher infarct growth in successfully reperfused patients ( p = 0.038) and in the endovascular treatment group ( p = 0.049). Finally, rCBV and HIR may serve as markers of collateral circulation in AIS patients prior to endovascular therapy.

CLINICAL TRIAL REGISTRATION

Unique identifier: NCT0165746.

eTICI reperfusion: defining success in endovascular stroke therapy

Background

Revascularization after endovascular therapy for acute ischemic stroke is measured by the Thrombolysis In Cerebral Infarction (TICI) scale, yet variability exists in scale definitions. We examined the degree of reperfusion with the expanded TICI (eTICI) scale and association with outcomes in the HERMES collaboration of recent endovascular trials.

Methods

The HERMES Imaging Core, blind to all other data, evaluated angiography after endovascular therapy in HERMES. A battery of TICI scores (mTICI, TICI, TICI2C) was used to define reperfusion of the initial target occlusion defined by non-invasive imaging and conventional angiography.

Results

Angiography of 801 subjects was available, including 797 defined by non-invasive imaging (154 internal carotid artery (ICA), 583 M1, 60 M2) and 748 by conventional angiography (195 ICA, 459 M1, 94 M2). Among 729 subjects in whom the reperfusion grade could be established, using eTICI (3=100%, 2C=90–99%, 2b67=67–89%, 2b50=50–66%) of the conventional angiography target occlusion, there were 63 eTICI 3 (9%), 166 eTICI 2c (23%), 218 eTICI 2b67 (30%), 103 eTICI 2b50 (14%), 100 eTICI 2a (14%), 19 eTICI 1 (3%), and 60 eTICI 0 (8%). Modified Rankin Scale shift analyses from baseline to 90 days showed that increasing TICI grades were linked with better outcomes, with significant distinctions between TICI 0/1 versus 2a (p=0.028), 2a versus 2b50 (p=0.017), and 2b50 versus 2b67 (p=0.014).

Conclusions

The benefit of endovascular therapy in HERMES was strongly associated with increasing degrees of reperfusion defined by eTICI. The eTICI metric identified meaningful distinctions in clinical outcomes and may be used in future studies and routine practice.

Regional Contributions to Poststroke Disability in Endovascular Therapy

Background and Purpose

The relative contribution of each Alberta Stroke Program Early CT Score (ASPECTS) region to poststroke disability likely varies across regions. Determining the relative weights of each ASPECTS region may improve patient selection for endovascular stroke therapy (EST).

Methods

In the combined Solitaire Flow Restoration with the Intention for Thrombectomy (SWIFT), Solitaire Flow Restoration Thrombectomy for Acute Revascularization (STAR), and Solitaire Flow Restoration with the Intention for Thrombectomy as Primary Endovascular Treatment (SWIFT PRIME) databases, we identified patients treated with the Solitaire stent retriever. Using 24-h CT scan, a multivariate ordinal regression was used to determine the relative contribution of each ASPECTS region to clinical outcome separately in each hemisphere. The coefficients from the regression were used to create a weighted ASPECTS (wASPECTS), which was compared with the original ASPECTS to predict 90-day modified Rankin Scale disability outcomes in an independent validation cohort.

Results

Among 342 patients treated with EST, the average age was 67 years, 57% were female, and the median National Institutes of Health Stroke Scale (NIHSS) score was 17 (IQR 13-20). The median ASPECTS at presentation was 8 (IQR 7-10). The most commonly involved ASPECTS regions on 24-h CT were the lentiform nuclei (70%), insula (55%), and caudate (52%). In multivariate analysis, preservation of M6 (β = 9.7) and M4 (β = 4.4) regions in the right hemisphere was most strongly predictive of good outcome. For the left hemisphere, M6 (β = 5.5), M5 (β = 4.1), and M3 (β = 3.1) generated the greatest parameter estimates, though they did not reach statistical significance. A wASPECTS incorporating all 20 parameter estimates resulted in improved discrimination against the original ASPECTS in the independent cohort (C-statistic 0.78 vs. 0.67, right hemisphere).

Conclusions

For both right and left hemisphere, preservation of the high cortical regions was more strongly associated with improved outcomes compared to the deep regions. Our findings support taking into consideration the location and relative weightings of the involved ASPECTS regions when evaluating a patient for EST.

Impact of Anesthetic Management on Safety and Outcomes Following Mechanical Thrombectomy for Ischemic Stroke in SWIFT PRIME Cohort

Background and purpose: The optimal anesthetic management of acute ischemic stroke patients during mechanical thrombectomy (MT) remains controversial. In this post-hoc analysis, we investigated the impact of anesthesia type on clinical outcomes in patients included in SWIFT PRIME trial.

Methods: Ninety-seven patients treated with MT were included. Patients treated in centers with general anesthesia (GA) policy (n = 32) were compared with those treated in centers with conscious sedation (CS) policy (n = 65). Primary outcomes studied included times to treatment initiation (TTI), rates of successful recanalization (TICI 2b/3), and functional independence (mRS 0–2 at 90 days). Secondary outcomes were adverse events, lowest systolic and diastolic blood pressures (LSBP and LDBP) during MT. Univariate analysis and multivariate regression logistic modeling were conducted.

Results: The GA-policy and CS-policy groups presented comparable TTI (94 ± 36 min vs. 102 ± 48 min; p = 0.44), rates of TICI 2b/3 recanalization (22/32 [68.8%] vs. 51/65 [78.5%]; p = 0.32). CS-policy was associated to higher rate of functional independence than GA-policy, but the difference was not significant (43/65 [66.2%] vs. 16/32 [50.0%]; p = 0.18). GA-policy patients had a higher rate of postoperative pneumonia (11/32 [34.4%] vs. 8/65 [12.3%]; p = 0.02) and lower LSBP (110 [30,160] mmHg vs. 119 [77,170] mmHg; p = 0.03) and LDBP (55 (15,75) mmHg vs. 67 [40,121]; p < 0.001). When corrected for differences in baseline characteristics, GA-policy was associated with lower rate of functional independence (OR 0.32; p = 0.05). A 10-point increase in perprocedural LDBP was associated with an increased likelihood of favorable outcome (OR 1.51; p = 0.01).

Conclusions: GA-policy for MT presented comparable TTI and rates of successful revascularization to CS-policy. However, GA-policy was associated with lower rates of functional independence and with higher incidence of perprocedural hypotension and postoperative pneumonia.

Clinical Trial Registration: URL—http://www.clinicaltrials.gov. Unique identifier: NCT01657461

The Frequency of Substantial Salvageable Penumbra in Thrombectomy-ineligible Patients with Acute Stroke

BACKGROUND AND PURPOSE

Endovascular therapy (ET) has become the standard of care for selected patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO). However, many LVO or medium vessel occlusion (MVO) patients are ineligible for ET, including some who harbor salvageable tissues. To develop complementary therapies for these patients, it is important to delineate their prevalence, clinical features, and outcomes.

METHODS

In a prospectively maintained database, we reviewed consecutive AIS patients between December 2015 and September 2016. Based on the first multimodal computed tomography or magnetic resonance imaging, patients were categorized as having substantial penumbra if perfusion lesion volume (Tmax >6 seconds) exceeded ischemic core volume (relative cerebral blood flow <30% on CT perfusion or apparent diffusion coefficient <620 on diffusion weighted image) by ≥20%.

RESULTS

Among 174 consecutive AIS patients presenting within 24 hours of last known well time, 29 (17%) had LVO or MVO and substantial penumbra, but were deemed ET ineligible. Among these patients, mean age was 81 (±13), 45% were female, and median National Institute of Health Stroke Scale score was 11 (interquartile range [IQR]: 5-19). The most common reasons for not pursuing ET were: distal occlusion (28%), mild neurologic deficit (16%), and temporally advanced core injury (16%). Ischemic core volume was 20 mL (±31), penumbral volume was 54 mL (±63), and mismatch ratio median was 5.6 (IQR: 2-infinite). Severe disability or death at discharge (modified Rankin scale: 4-6) occurred in 72% of the patients.

CONCLUSION

Even in the modern stent retriever era, 1 in 6 AIS patients presents with substantial penumbra judged not appropriate for ET. This population may benefit from the development of alternative therapies, including collateral enhancement, neuroprotection, and thrombectomy devices deployable in distal arteries.

The Meningioma Vascularity Index: a volumetric analysis of flow voids to predict intraoperative blood loss in nonembolized meningiomas

OBJECTIVE

Meningiomas that appear hypervascular on neuroimaging could be amenable to preoperative embolization. However, methods for measuring hypervascularity have not been described, nor has the benefit of preoperative embolization been adjudicated. The objective of this study was to show a relationship between flow void volume (measured on MRI) and intraoperative estimated blood loss (EBL) in nonembolized meningiomas.

METHODS

The authors performed volumetric analyses of 51 intracranial meningiomas (21 preoperatively embolized) resected at their institution. Through the use of image segmentation software and a voxel-based segmentation method, flow void volumes were measured on T2-weighted MR images. This metric was named the Meningioma Vascularity Index (MVI). The primary outcomes were intraoperative EBL and perioperative blood transfusion.

RESULTS

In the nonembolized group, the MVI correlated with intraoperative EBL when controlling for tumor volume (r = 0.55, p = 0.002). The MVI also correlated with perioperative blood transfusion (point-biserial correlation [rpb] = 0.57, p = 0.001). A greater MVI was associated with an increased risk of blood transfusion (odds ratio [OR] 5.79, 95% confidence interval [CI] 1.15-29.15) and subtotal resection (OR 7.64, 95% CI 1.74-33.58). In the embolized group, those relationships were not found. There were no significant differences in MVI, intraoperative EBL, or blood transfusion across groups.

CONCLUSIONS

This study clearly shows a relationship between MVI and intraoperative EBL in nonembolized meningiomas when controlling for tumor volume. The MVI is a potential biomarker for tumors that would benefit from embolization.

A review of the diagnosis and management of vertebral basilar (posterior) circulation disease

We have reviewed the English literature published in the last 70 years on Diseases of the Vertebral Basilar Circulation, or Posterior Circulation Disease (PCD). We have found that errors have been made in the conduct and interpretation of these studies that have led to incorrect approaches to the management of PCD. Because of the difficulty in evaluating the PC, the management of PCD has been incorrectly applied from anterior circulation disease (ACD) experience to PCD. PCD is a common form of stroke affecting 20-40% patients with stroke. Yet, the evidence is strong that the Anterior Circulation (AC) and Posterior Circulations (PC) differ in their pathology, in their clinical presentations, in the rapidity of development of symptoms, in optimal imaging methods, and in available treatments. There appears to be two categories of patients who present with PCD. The first, acute basilar artery occlusion has a more rapid onset. The diagnosis must be made quickly and if imaging proves a diagnosis of Basilar Artery Occlusion (BAO), the treatment of choice is Interventional removal of the basilar artery thrombosis or embolus. The second category of PCD and the most commonly seen PCD disease process presents with non-specific symptoms and early warnings of PCD that now can be related to ischemic events in the entire PC vessels. These warning symptoms and signs occur much earlier than those in the AC. IA angiography is still the gold standard of diagnosis and is superior in definition to MR and CT angiography which are commonly used as a convenient screening imaging tool to evaluate PCD but are both inferior to IA angiography in definition for lesions below 3-4 mm. In at least two reported studies 7T MR angiography appears superior to other imaging modalities and will become the gold standard of imaging of PCD in the future. Medical treatments applied to the ACD have not been proven of value in specific forms of PCD. Interventional therapy was promising but of unproven value in Randomized Controlled Trials (RCT) except for the treatment of Basilar Artery Occlusion (BAO). Surgical revascularization has been proved to be highly successful in patients, who are refractory to medical therapy. These studies have been ignored by the scientific community basically because of an incorrect interpretation of the flawed EC-IC Bypass Trial in 1985 as applying to all stroke patients. Moreover, the EC-IC Bypass Study did not include PCD patients in their study population, but the study results were extrapolated to patients with PCD without any scientific basis. This experience led clinicians to an incorrect bias that surgical treatments are of no value in PCD. Thus, incorrectly, surgical treatments of PCD have not been considered among the therapeutic possibilities for PCD. QMRA is a new quantitative MR technique that measures specific blood flow in extra and intracranial vessels. QMRA has been used to select those patients who may benefit from medical, or interventional, or surgical treatment for PCD based on flow determinations with a high success rate. QMRA accurately predicts the flows in many large and small vessels in the PC and AC and clearly indicates that both circulations are intimately related. From medical and surgical studies, the longer one waits for surgical treatment the higher the risk of a poor outcome results. This observation becomes obvious when the rapidity of development of PCD is compared with ACD. Recent advances in endovascular therapy in the treatment of acute basilar thrombosis is a clear sign that early diagnosis and treatment of PCD will reduce the morbidity and mortality of these diseases. In this review it is evident that there are multiple medical and surgical treatments for PCD depending upon the location of the lesion(s) and the collateral circulation demonstrated. It is clear that the AC and PC have significant differences. With the exception of the large population studies from Oxford England, the reported studies on the management of PCD in the literature represent small selected subsets of the universe of PC diseases, the information from which is not generalizable to the universe of PCD patients. At this point in the history of PCD, there are not large enough databases of similar patients to provide a basis for valid randomized studies, with the exception of the surgical studies. Thus, a high index of suspicion of the early warning symptoms of PCD should lead to a rapid individual clinical assessment of patients selecting those with PCD. Medical, interventional, and/or surgical treatments should be chosen based on knowledge presented in this review. Recording the results in a national Registry on a continuing basis will provide the data that may help advance the management of PCD based on larger data bases of well documented patient information to guide the selection of future therapies for PCD treatments. It is also clear that the management of patients within the complex of diseases that comprise PCD should be performed in centers with expertise in the imaging, medical, interventional and surgical approaches to diseases of the PCD.

Apparent Diffusion Coefficient Signal Intensity Ratio Predicts the Effect of Revascularization on Ischemic Cerebral Edema

BACKGROUND

Apparent diffusion coefficient (ADC) imaging is a biomarker of cytotoxic injury that predicts edema formation and outcome after ischemic stroke. It therefore has the potential to serve as a "tissue clock" to describe the extent of ischemic injury and potentially predict response to therapy. The goal of this study was to determine the relationship between baseline ADC signal intensity, revascularization, and edema formation.

METHODS

We examined the ADC signal intensity ratio (ADCr) of the stroke lesion (defined as the baseline DWI hyperintense region) compared to the contralateral normal hemisphere in 65 subjects from the Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy trial. The associations between ADCr, neurologic outcome, and cerebral edema were examined. Finally, we explored the interaction between baseline ADCr and vessel recanalization at day 7 on post-stroke edema.

RESULTS

We found that lower initial ADCr was associated with a worse outcome on the modified Rankin Scale (mRS) at 90 days (52.2% of those with ADCr <64% were mRS 5-6 vs. 19.1% with ADCr ≥64%, p = 0.006). Those subjects with reconstitution of flow distal to the initial vessel occlusion showed greater normalization of ADCr on follow-up scan (increase in ADCr of 16.4 ± 2.07 vs. 1.99 ± 4.33%, p = 0.0039). In those patients with low baseline ADCr, successful revascularization was associated with reduced edema (median swelling volume 164 mL [interquartile range (IQR) 53.3-190 mL] vs. 20.7 mL [IQR 3.20-55.1 mL], p = 0.024).

CONCLUSIONS

This study reaffirms the association of ADCr with outcome after stroke, supports the idea that reperfusion may attenuate rather than enhance post-stroke edema, and indicates that the degree of edema with and without revascularization may be predicted by ADCr.

ASPECTS-based reperfusion status on arterial spin labeling is associated with clinical outcome in acute ischemic stroke patients

The purpose of this study was to develop and evaluate a scoring system for assessing reperfusion status based on arterial spin labeled (ASL) perfusion MRI in acute ischemic stroke (AIS) patients receiving thrombolysis and/or endovascular treatment. Pseudo-continuous ASL with background suppressed 3D GRASE was acquired along with DWI in 90 patients within 24 h post-treatment. An automatic reperfusion scoring system (auto-RPS) was devised based on the Alberta Stroke Program Early CT Score (ASPECTS) template, and compared with manual RPS and DWI-ASPECTS. TICI (thrombolysis in cerebral infarction) scores were graded in 48 patients who received endovascular treatment. Favorable outcomes were defined by a modified Rankin Scale score of 0-2 at three months. Auto-RPS was positively correlated with DWI-ASPECTS (ρ = 0.6, P < 0.001) and was on average 1 point lower than DWI-ASPECTS ( P < 0.001). The area under the receiver operating characteristic curve for discriminating poor functional outcome (n = 90) was 0.75 (95% CI, 0.64-0.86) for manual RPS, 0.85 (95% CI, 0.76-0.94) for auto-RPS, and 0.81 (95% CI, 0.71-0.90) for DWI-ASPECTS. Multiple logistic regression analysis in the TICI-graded patients (n = 48) showed that auto-RPS is highly associated with functional outcome (OR = 25.2, 95% CI 4.02-496, P < 0.01). Post treatment auto-RPS within 24 h provides a useful tool to predict functional outcome in AIS patients.