Symmetric CTA Collaterals Identify Patients with Slow-progressing Stroke Likely to Benefit from Late Thrombectomy

Trans-Clot MAP gradient: A novel innovative technique during thrombectomy for acute ischemic stroke with potential applications for assessing collateral circulation, determining clot etiology, informing device selection, and predicting first-pass success

Endovascular mechanical thrombectomy has significantly improved recovery in acute ischemic stroke (AIS). While traditional patient selection has relied on factors such as last known well and penumbra volume, emerging research highlights the importance of collateral circulation in influencing thrombectomy success. However, current methods to assess collateral circulation are often unreliable and lack standardization, limiting their integration into clinical decision-making and prompting the need for innovative approaches. This study introduces trans-clot manometry as a promising approach for quantitatively assessing collateral blood flow before thrombectomy. Two patients were included in this study: a 64-year-old female with a left M1 near-complete occlusion and an 81-year-old male with a left P1 occlusion. After receiving intravenous tenecteplase, each patient underwent emergent thrombectomy where intraoperative trans-clot manometry revealed significant trans-clot mean arterial pressure (MAP) gradients (66.7% for Patient 1 and 96.9% for Patient 2). Both patients had successful first-pass thrombectomy (Patient 1: TICI 3; Patient 2: TICI 3), with substantial clinical improvement (Patient 1: NIHSS 11 to 1; Patient 2: NIHSS 19 to 8). Intraoperative trans-clot manometry offers a simple yet powerful, objective, and generalizable measure of collateral circulation, applicable to a wide range of AIS cases regardless of clot location or vessel size. In addition, real-time correlations with heart-rate variability and radial artery pressures provide an intrinsic quality control, ensuring proper execution of the technique and accuracy of the resulting MAP gradient. Future research will focus on validating this approach, determining its generalizability, and establishing MAP gradient thresholds to enhance device selection and predict first-pass success.

High relative cerebral blood volume is associated with good long term clinical outcomes in acute ischemic stroke: a retrospective cohort study

BACKGROUND

Endovascular therapy for acute ischemic stroke has been shown to be highly effective in selected patients. However, the ideal criteria for patient selection are still debated. It is well known that collateral flow is an important factor, but the assessment is often subjective and time-consuming. Relative cerebral blood volume (rCBV) is a putative indicator of collateral capacity and can be quickly and easily determined by automated quantitative analysis. We investigated the relationship between rCBV of the affected region and clinical outcome in patients with acute ischemic stroke after endovascular therapy.

METHODS

We conducted a retrospective study on consecutive patients between January 2017 and May 2019. Patients with acute ischemic stroke of the anterior circulation who underwent imaging including computed tomography perfusion and were treated with mechanical thrombectomy (MT) were eligible for inclusion. rCBV was calculated automatically with RAPID software by dividing the average cerebral blood volume (CBV) of the affected region (time-to-maximum (Tmax) > 6 s) by the CBV of the unaffected contralateral side. The primary outcome was determined by the modified Rankin Scale (mRS) after 90 days. Good clinical outcome was defined as mRS ≤ 2. We compared means, performed mono- and multivariate logistical regression and calculated a receiver operating characteristic (ROC)-analysis to determine the ideal cutoff value to predict clinical outcomes.

RESULTS

155 patients were enrolled in this study. 66 patients (42.58%) had good clinical outcomes. Higher rCBV was associated with good clinical outcome (p < 0.001), even after adjustment for the patients' status according to mRS and National Institute of Health Stroke Scale (NIHSS) age and Alberta stroke program early computed tomography score (ASPECTS) at baseline (p = 0.006). ROC-analysis revealed 0.650 (confidence interval: 0.616-0.778) as the optimal cutoff value.

CONCLUSION

Higher rCBV at baseline is associated with good clinical long-term outcomes in patients with acute ischemic stroke treated by MT. In this study we provide the biggest collective so far that gives evidence that rCBV can be a valuable tool to identify patients who might benefit from MT and are able give a threshold to help to offer patients MT in borderline cases.

Multi-phase CT-Angiography outperforms angiographic careggi collateral score and predicts functional outcome in acute ischemic stroke

BACKGROUND

Collaterals are a strong determinant of clinical outcome in acute ischemic stroke (AIS) patients undergoing Endovascular Treatment (EVT). Careggi Collateral Score (CCS) is an angiographic score that demonstrated to be superior to the widely suggested ASITN/SIR score. Multi-phase CT-Angiography (mCTA) could be alternatively adopted for collateral assessment. We investigated whether mCTA had an equivalent predictive performance for functional outcome compared to CCS.

METHODS

Consecutive AIS patients undergoing EVT for large vessel occlusion within 24 h from onset were analyzed. Receiver operating characteristic curves and multivariable logistic regression were investigated to evaluate the predictive performance of mCTA collateral score (range 0-5) and CCS (range 0-4) for good functional outcome (three-months modified Rankin Scale 0-2).

RESULTS

We included 201 subjects (59.7% females, mean age 75), of whom 96 (47.7%) had good outcome at three-months. Both CCS (OR = 14.4, 95% CI = 6.3-33.8) and mCTA (OR = 23.8, 95% CI = 10.1-56.4) collateral scores were independent predictors of outcome. The AUC of CCS was 0.80 (95% CI 0.73-0.86) and the best cut-off was ≥ 3 (87% sensitivity, 71% specificity), while the AUC of mCTA collateral score was 0.84 (95% CI 0.78-0.90) with an optimal cut-off of ≥ 4 (85% sensitivity, 87% specificity). Patients with good mCTA collaterals experienced smaller (16.6 vs. 63.7 mL, p < 0.001) infarct lesion as compared to those with mCTA poor collaterals.

CONCLUSION

mCTA discriminative ability for three-months 0-2 mRS was found to be comparable to CCS. mCTA appears a valid, non-invasive imaging modality for evaluating collaterals of AIS patients potentially eligible for EVT.

Colour-coded collateral and venous outflow patterns in estimating infarct progression and predicting functional independence for stroke patients in late time window

OBJECTIVES

To investigate whether cerebral collateral and venous outflow (VO) patterns on colour-coded multi-phase computed tomography angiography (mCTA) can estimate ischaemic core growth rate (IGR) and predict 90-day functional independence for patients with late-presenting acute ischaemic stroke (AIS).

METHODS

The retrospective analysis included 127 AIS patients with a late time window. All patients underwent baseline mCTA with colour-coded reconstruction and computed tomography perfusion. Both collateral score and VO score on colour-coded mCTA maps were analysed and recorded. The IGR was calculated as ischaemic core volume divided by the time from onset to imaging. A 90-day modified Rankin Scale score of 0-2 was defined as functional independence. Kendall's Tau-b analysis was used for nonparametric correlation analysis. Propensity scores, logistic regressions, and receiver operator characteristic (ROC) curves were applied to construct the prediction model.

RESULTS

Moderate correlations were found between collateral delay and IGR (Tau-b = -0.554) and between VO and IGR (Tau-b = -0.501). High collateral score (odds ratio = 3.01) and adequate VO (odds ratio = 4.89) remained independent predictors for 90-day functional independence after adjustment. The joint predictive model, which integrated the VO score and clinical features, demonstrated an area under the ROC curve (AUC) of 0.878. The AUCs of collateral score and VO score were 0.836 and 0.883 for outcome prediction after adjustment.

CONCLUSIONS

Cerebral collateral and VO patterns based on colour-coded mCTA can effectively predict infarct progression and 90-day clinical outcomes, even for AIS patients beyond the routine time window.

ADVANCES IN KNOWLEDGE

Colour-coded mCTA is a readily understandable post-processing technique for the rapid assessment of collateral circulation and VO status in stroke imaging. A moderate correlation was observed between the characteristics of collateral delay/VO on colour-coded mCTA and IGR in patients with AIS. Both high-quality collateral circulation and "red superficial middle cerebral vein sign" can predict 90-day functional independence even for patients beyond the routine time window.

Impact and determinants of door in-door out time for stroke thrombectomy transfers in a large hub-and-spoke network

INTRODUCTION

The mantra "time is brain" cannot be overstated for patients suffering from acute ischemic stroke. This is especially true for those with large vessel occlusions (LVOs) requiring transfer to an endovascular thrombectomy (EVT) capable center. We sought to evaluate the spoke hospital door in-door out (DIDO) times for patients transferred to our hub center for EVT.

METHODS

Individuals who first presented with LVO to a spoke hospital and were then transferred to the hub for EVT were retrospectively identified from a prospectively maintained database from January 2019 to November 2022. DIDO was defined as the time between spoke hospital door in arrival and door out exit. Baseline characteristics, treatments, and outcomes were compared, dichotomizing DIDO at 90 minutes based in the American Heart Association goal for DIDO ≤90 minutes for 50% of transfers. Multivariable regression analyses were performed for determinants of the 90-day ordinal modified Rankin Scale (mRS) and DIDO.

RESULTS

We identified 194 patients transferred for EVT with available DIDO. The median age was 67 years (IQR 57-80), and 46% were female. The median National Institutes of Health Stroke Scale (NIHSS) was 16 (10-20), 50% were treated with intravenous thrombolysis at a spoke, and TICI 2B-3 reperfusion was achieved in 87% at the hub. The median DIDO was 120 minutes (97-149), with DIDO ≤90 minutes achieved in 18%. DIDO was a significant determinant of 90-day ordinal mRS (B = 0.007, 95% CI = 0.001-0.012, p = 0.013), even when accounting for the last known well-to-spoke door in, spoke door out-to-hub arrival, hub arrival-to-puncture, puncture-to-first pass, age, NIHSS, intravenous thrombolysis, TICI 2B-3, and symptomatic intracranial hemorrhage. Importantly, determinants of DIDO included Black race or Hispanic ethnicity (B = 0.918, 95% CI = 0.010-1.826, p = 0.048), atrial fibrillation or heart failure (B = 0.793, 95% CI = 0.257-1.329, p = 0.004), and basilar LVO location (B = 2.528, 95% CI = 1.154-3.901, p < 0.001).

CONCLUSION

Spoke DIDO was the most important period of time for long-term outcomes of LVO stroke patients treated with EVT. Targets were identified to reduce DIDO and improve patient outcomes.

White matter hyperintensity burden and collateral circulation in acute ischemic stroke with large artery occlusion

OBJECTIVE

This study aimed to investigate the association between white matter hyperintensity (WMH) burden and pial collaterals in acute strokes caused by intracranial large artery occlusion treated with mechanical thrombectomy in the anterior circulation, focusing on stroke subtypes.

METHODS

Consecutive patients undergoing mechanical thrombectomy between December 2019 and June 2022 were retrospectively screened. The Fazekas scale assessed WMH burden. Pial collaterals were categorized as either poor (0-2) or good (3-4) based on the Higashida score. A multivariable analysis was used to determine the relationship between WMH burden and pial collaterals. Subgroup analyses delved into associations stratified by stroke subtypes, namely cardioembolism (CE), tandem lesions (TLs), and intracranial atherosclerosis (ICAS).

RESULTS

Of the 573 patients included, 274 (47.8%) demonstrated poor pial collaterals. Multivariable regression indicated a strong association between extensive WMH burden (Fazekas score of 3-6) and poor collaterals [adjusted OR 3.04, 95% CI 1.70-5.46, P < 0.001]. Additional independent predictors of poor collaterals encompassed ICAS-related occlusion (aOR 0.26, 95% CI 0.09-0.76, P = 0.014), female sex (aOR 0.63, 95% CI 0.41-0.96, P = 0.031), and baseline Alberta Stroke Program Early Computed Tomography scores (aOR 0.80, 95% CI 0.74-0.88, P < 0.001). Notably, an interaction between extensive WMH burden and stroke subtypes was observed in predicting poor collaterals (P = 0.001), being pronounced for CE (adjusted OR 2.30, 95% CI 1.21-4.37) and TLs (adjusted OR 5.09, 95% CI 2.32-11.16), but was absent in ICAS (adjusted OR 1.24, 95% CI 0.65-2.36).

CONCLUSIONS

Among patients treated with mechanical thrombectomy for anterior circulation large artery occlusion, extensive WMH burden correlates with poor pial collaterals in embolic occlusion cases (CE and TLs), but not in ICAS-related occlusion.

Factors influencing the reliability of a CT angiography-based deep learning method for infarct volume estimation

Objectives

CT angiography (CTA)-based machine learning methods for infarct volume estimation have shown a tendency to overestimate infarct core and final infarct volumes (FIV). Our aim was to assess factors influencing the reliability of these methods.

Methods

The effect of collateral circulation on the correlation between convolutional neural network (CNN) estimations and FIV was assessed based on the Miteff system and hypoperfusion intensity ratio (HIR) in 121 patients with anterior circulation acute ischaemic stroke using Pearson correlation coefficients and median volumes. Correlation was also assessed between successful and futile thrombectomies. The timing of individual CTAs in relation to CTP studies was analysed.

Results

The strength of correlation between CNN estimated volumes and FIV did not change significantly depending on collateral status as assessed with the Miteff system or HIR, being poor to moderate (r = 0.09-0.50). The strongest correlation was found in patients with futile thrombectomies (r = 0.61). Median CNN estimates showed a trend for overestimation compared to FIVs. CTA was acquired in the mid arterial phase in virtually all patients (120/121).

Conclusions

This study showed no effect of collateral status on the reliability of the CNN and best correlation was found in patients with futile thrombectomies. CTA timing in the mid arterial phase in virtually all patients can explain infarct volume overestimation.

Advances in knowledge

CTA timing seems to be the most important factor influencing the reliability of current CTA-based machine learning methods, emphasizing the need for CTA protocol optimization for infarct core estimation.

Interaction between intravenous thrombolysis and clinical outcome between slow and fast progressors undergoing mechanical thrombectomy: a post-hoc analysis of the SWIFT-DIRECT trial

BACKGROUND

In proximal occlusions, the effect of reperfusion therapies may differ between slow or fast progressors. We investigated the effect of intravenous thrombolysis (IVT) (with alteplase) plus mechanical thrombectomy (MT) versus thrombectomy alone among slow versus fast stroke progressors.

METHODS

The SWIFT-DIRECT trial data were analyzed: 408 patients randomized to IVT+MT or MT alone. Infarct growth speed was defined by the number of points of decay in the initial Alberta Stroke Program Early CT Score (ASPECTS) divided by the onset-to-imaging time. The primary endpoint was 3-month functional independence (modified Rankin scale 0-2). In the primary analysis, the study population was dichotomized into slow and fast progressors using median infarct growth velocity. Secondary analysis was also conducted using quartiles of ASPECTS decay.

RESULTS

We included 376 patients: 191 IVT+MT, 185 MT alone; median age 73 years (IQR 65-81); median initial National Institutes of Health Stroke Scale (NIHSS) 17 (IQR 13-20). The median infarct growth velocity was 1.2 points/hour. Overall, we did not observe a significant interaction between the infarct growth speed and the allocation to either randomization group on the odds of favourable outcome (P=0.68). In the IVT+MT group, odds of any intracranial hemorrhage (ICH) were significantly lower in slow progressors (22.8% vs 36.4%; OR 0.52, 95% CI 0.27 to 0.98) and higher among fast progressors (49.4% vs 26.8%; OR 2.62, 95% CI 1.42 to 4.82) (P value for interaction <0.001). Similar results were observed in secondary analyses.

CONCLUSION

In this SWIFT-DIRECT subanalysis, we did not find evidence for a significant interaction of the velocity of infarct growth on the odds of favourable outcome according to treatment by MT alone or combined IVT+MT. However, prior IVT was associated with significantly reduced occurrence of any ICH among slow progressors whereas this was increased in fast progressors.

Early and late infarct growth rate in ischemic stroke patients after successful endovascular treatment in early time window: correlation of imaging and clinical factors with clinical outcome

Background

The prospective study assessed infarct growth rate (IGR) in acute ischemic stroke (AIS) with large vessel occlusion (LVO) after recanalization in early time window. Early IGR (EIGR) and late IGR (LIGR) were correlated with imaging and clinical data; we searched for outcome predictors.

Methods

We included 71 consecutive patients. Subjects underwent computed tomography perfusion (CTP) for ischemic core volume assessment at 99.0 minutes (median) from stroke onset, recanalization was performed at 78.0 minutes (median) from CTP. Final infarct volume (FIV) was measured on 24±2 hours imaging follow-up. EIGR was calculated as the core volume/time between stroke onset and CTP; LIGR was calculated as FIV/time between CTP and imaging follow-up. Twenty-two subjects were assessed as poor outcome, 49 as good outcome. Group differences were tested by Mann-Whitney test and χ2 test. Bayesian logistic regression models were used to predict clinical outcome, Pearson correlations for the log-transformed predictors.

Results

Subjects with poor outcome were older, median age 78.0 [interquartile range (IQR): 71.8, 83.8] versus 68.0 (IQR: 57.0, 73.0) years; 95% confidence interval (CI): 6.00 to 16.00; P<0.001. Their stroke severity scale was higher, median 19.0 (IQR: 16.0, 20.0) versus 15.5 (IQR: 10.8, 18.0); 95% CI: 1.00 to 6.00; P<0.001. They had higher EIGR, median 23.9 (IQR: 6.4, 104.0) versus 6.7 (IQR: 1.7, 13.0) mL/h; 95% CI: 3.26 to 53.68; P=0.002; and larger core, median 52.5 (IQR: 13.1, 148.5) versus 10.0 (IQR: 1.4, 20.0) mL; 95% CI: 11.00 to 81.00; P<0.001. In subjects with poor outcome, infarct growth continued after thrombectomy with LIGR 2.0 (IQR: 1.2, 9.7) versus 0.3 (IQR: 0.0, 0.7) mL/h; 95% CI: 1.10 to 6.10; P<0.001; resulting in larger FIV, median 186.5 (IQR: 49.3, 280.8) versus 18.5 (IQR: 8.0, 34.0) mL; 95% CI: 55.30 to 214.00; P<0.001. Strong correlations among predictors were found e.g., core and EIGR (r=0.942), LIGR and FIV (r=0.779), core and FIV (r=0.761). Clinical outcome was best predicted using data from later measurements as FIV and LIGR.

Conclusions

Data from later measurements were more predictive, there was no major benefit to use growth over volume data.

Preliminary experience of CT imaging of the ischaemic brain penumbra through spectral processing of multiphasic CTA datasets

To assess ischaemic penumbra through the post-processing of the spectral multiphasic CT Angiography (mCTA) data in acute ischaemic stroke (AIS) patients. Thirty one consecutive patients strongly suspected of severe Middle Cerebral Artery AIS presenting less than 6 h after onset of symptoms or with unknown time of onset of symptoms underwent a standardized CT protocol in spectral mode including Non Contrast CT, mCTA, and Perfusion CT (CTP) on a dual-layer MDCT system. Areas disclosing delayed enhancement on iodine density (ID) maps were highlighted by subtraction of the serial mCTA datasets. Two neuroradiologists independently rated the correspondence between delayed enhancing areas at mCTA and the penumbral/infarcted areas delineated by two validated CTP applications using a 5-levels scoring scale. Interobserver agreement between observers was evaluated by kappa statistics. Dose delivery was recorded for each acquisition. Averaged correspondence score between penumbra delineation using subtracted mCTA-derived ID maps and CTP ones was 2.76 for one application and 2.9 for the other with best interobserver agreement kappa value at 0.59. All 6 stroke mimics out of the 31 patients' cohort were correctly identified. Average dose delivery was 7.55 mSv for the whole procedure of which CTP accounted for 39.7%. Post-processing of spectral mCTA data could allow clinically relevant assessment of the presence or absence of ischaemic penumbra in AIS-suspected patients if results of this proof-of-concept study should be confirmed in larger patients'series.

Effect of leukoaraiosis on collateral circulation in acute ischemic stroke treated with endovascular therapy: a meta-analysis

BACKGROUND AND OBJECTIVE

The recruitment of collateral circulation correlates with a balance of the microvasculature. Uncertainty remains to be made about the association of leukoaraiosis with leptomeningeal collaterals. To explore the effect of leukoaraiosis on leptomeningeal collaterals in patients treated with endovascular therapy.

METHODS

Observational studies exploring the correlation between leukoaraiosis and leptomeningeal collaterals in large vessel occlusion treated with endovascular therapy were searched from PubMed, EMBASE, and Cochrane Libraries databases. Two independent reviewers retrieved eligible literature, extracted purpose-related data, and utilized the Newcastle-Ottawa Scale to evaluate the risk of bias. A Mantel-Haenszel method was used to calculate the odds ratio (OR). Meta-regression and subgroup analyses were conducted to clarify heterogeneity.

RESULTS

Data from 10 studies with 1606 patients were extracted for pooled analysis. Compared to non-severe leukoaraiosis, patients with severe leukoaraiosis showed significant relevance to poor leptomeningeal collaterals (OR, 2.13; 95% confidence interval [1.27-3.57]; P = 0.004). Meta-regression indicated that sample size (coefficient = -0.007299, P = 0.035) and the number of female patients (coefficient = -0.0174709, P = 0.020) were sources of heterogeneity. Furthermore, all of the countries (USA versus France versus China, Q = 3.67, P = 0.159), various assessment scales of leukoaraiosis (the Fazekas scale versus Non-Fazekas scales, Q = 0.77, P = 0.379), and different imaging methods of leukoaraiosis (computed tomography versus magnetic resonance imaging, Q = 2.12, P = 0.146) and leptomeningeal collaterals (computed tomography angiography versus digital subtraction angiography, Q = 1.21, P = 0.271) showed no contribution to the effect size.

CONCLUSION

Severe leukoaraiosis is associated with poor leptomeningeal collaterals in patients treated with endovascular therapy. Further studies may focus on whether the finding applies to different stroke subtypes.

Advanced Imaging for Acute Stroke Treatment Selection: CT, CTA, CT Perfusion, and MR Imaging

There is constant evolution in the diagnosis and treatment of acute ischemic stroke due to advances in treatments, imaging, and outreach. Two major revolutions were the advent of intravenous thrombolysis in the 1990s and endovascular thrombectomy in 2010s. Neuroimaging approaches have also evolved with key goals-detect hemorrhage, augment thrombolysis treatment selection, detect arterial occlusion, estimate infarct core, estimate viable penumbra, and augment thrombectomy treatment selection. The ideal approach to diagnosis and treatment may differ depending on the system of care and available resources. Future directions include expanding indications for these treatments, including a shift from time-based to tissue-based selection.

Collateral Status and Outcomes after Thrombectomy

Endovascular treatment (EVT) using novel mechanical thrombectomy devices has been the gold standard for patients with acute ischemic stroke caused by large vessel occlusion. Selection criteria of randomized control trials commonly include baseline infarct volume with or without penumbra evaluation. Although the collateral status has been studied and is known to modify imaging results and clinical course, it has not been commonly used for trials. Many post hoc studies, however, revealed that collateral status can help predict infarct growth, recanalization success, decreased hemorrhagic transformation after EVT, and extension of the therapeutic time window for revascularization. Here, we systematically review the recent literature and summarized the outcomes of EVT according to the collateral status of patients with acute ischemic stroke caused by large vessel occlusion. The studies reviewed indicate that pretreatment collateral circulation is associated with both clinical and imaging outcomes after EVT in patients with acute ischemic stroke due to large vessel occlusion although most patients were already selected by other imaging or clinical criteria. However, treatment decisions using information on patients' collateral status have not progressed in clinical practice. Further randomized trials are needed to evaluate the risks and benefits of EVT in consideration of collateral status.

Symmetric collateral pattern on CTA predicts favorable outcomes after endovascular thrombectomy for large vessel occlusion stroke

Endovascular thrombectomy (EVT) has revolutionized large vessel occlusion (LVO) stroke management, but often requires advanced imaging. The collateral pattern on CT angiograms may be an alternative because a symmetric collateral pattern correlates with a slowly growing, small ischemic core. We tested the hypothesis that such patients will have favorable outcomes after EVT. Consecutive patients (n = 74) with anterior LVOs who underwent EVT were retrospectively analyzed. Inclusion criteria were available CTA and 90-day modified Rankin Scale (mRS). CTA collateral patterns were symmetric in 36%, malignant in 24%, or other in 39%. Median NIHSS was 11 for symmetric, 18 for malignant, and 19 for other (p = 0.02). Ninety-day mRS ≤2, indicating independent living, was achieved in 67% of symmetric, 17% of malignant, and 38% of other patterns (p = 0.003). A symmetric collateral pattern was a significant determinant of 90-day mRS ≤2 (aOR = 6.62, 95%CI = 2.24,19.53; p = 0.001) in a multivariable model that included age, NIHSS, baseline mRS, thrombolysis, LVO location, and successful reperfusion. We conclude that a symmetric collateral pattern predicts favorable outcomes after EVT for LVO stroke. Because the pattern also marks slow ischemic core growth, patients with symmetric collaterals may be suitable for transfer for thrombectomy. A malignant collateral pattern is associated with poor clinical outcomes.

Structural and functional imaging of brains

Analyzing the complex structures and functions of brain is the key issue to understanding the physiological and pathological processes. Although neuronal morphology and local distribution of neurons/blood vessels in the brain have been known, the subcellular structures of cells remain challenging, especially in the live brain. In addition, the complicated brain functions involve numerous functional molecules, but the concentrations, distributions and interactions of these molecules in the brain are still poorly understood. In this review, frontier techniques available for multiscale structure imaging from organelles to the whole brain are first overviewed, including magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), serial-section electron microscopy (ssEM), light microscopy (LM) and synchrotron-based X-ray microscopy (XRM). Specially, XRM for three-dimensional (3D) imaging of large-scale brain tissue with high resolution and fast imaging speed is highlighted. Additionally, the development of elegant methods for acquisition of brain functions from electrical/chemical signals in the brain is outlined. In particular, the new electrophysiology technologies for neural recordings at the single-neuron level and in the brain are also summarized. We also focus on the construction of electrochemical probes based on dual-recognition strategy and surface/interface chemistry for determination of chemical species in the brain with high selectivity and long-term stability, as well as electrochemophysiological microarray for simultaneously recording of electrochemical and electrophysiological signals in the brain. Moreover, the recent development of brain MRI probes with high contrast-to-noise ratio (CNR) and sensitivity based on hyperpolarized techniques and multi-nuclear chemistry is introduced. Furthermore, multiple optical probes and instruments, especially the optophysiological Raman probes and fiber Raman photometry, for imaging and biosensing in live brain are emphasized. Finally, a brief perspective on existing challenges and further research development is provided.

Understanding Delays in MRI-based Selection of Large Vessel Occlusion Stroke Patients for Endovascular Thrombectomy

PURPOSE

Given the efficacy of endovascular thrombectomy (EVT), optimizing systems of delivery is crucial. Magnetic resonance imaging (MRI) is the gold standard for evaluating tissue viability but may require more time to obtain and interpret. We sought to identify determinants of arrival-to-puncture time for patients who underwent MRI-based EVT selection in a real-world setting.

METHODS

Patients were identified from a prospectively maintained database from 2011-2019 that included demographics, presentations, treatments, and outcomes. Process times were obtained from the medical charts. MRI times were obtained from time stamps on the first sequence. Linear and logistic regressions were used to infer explanatory variables of arrival-to-puncture times and effects of arrival-to-puncture time on functional outcomes.

RESULTS

In this study 192 patients (median age 70 years, 57% women, 12% non-white) underwent MRI-based EVT selection. 66% also underwent computed tomography (CT) at the hub before EVT. General anesthesia was used for 33%. Among the entire cohort, the median arrival-to-puncture was 102 min; however, among those without CT it was 77 min. Longer arrival-to-puncture times independently reduced the odds of 90-day good outcome (∆mRS ≤ 2 from pre-stroke, aOR = 0.990, 95%CI = 0.981-0.999, p = 0.040) when controlling for age, NIHSS, and good reperfusion (TICI 2b-3). Independent determinants of longer arrival-to-puncture were CT plus MRI (β = 0.205, p = 0.003), non-white race/ethnicity (β = 0.162, p = 0.012), coronary disease (β = 0.205, p = 0.001), and general anesthesia (β = 0.364, p < 0.0001).

CONCLUSION

Minimizing arrival-to-puncture time is important for outcomes. Real-world challenges exist in an MRI-based EVT selection protocol; avoiding double imaging is key to saving time. Racial/ethnic disparities require further study. Understanding variables associated with delay will inform protocol changes.

Direct to angio-suite large vessel occlusion transfers achieve faster arrival-to-puncture times and improved outcomes

Introduction

For patients with large vessel occlusion (LVO) stroke, time to treatment with endovascular thrombectomy (EVT) is crucial to prevent infarction and improve outcomes. We sought to evaluate the hub arrival-to-puncture times and outcomes for transferred patients accepted directly to the angio-suite (LVO2OR) versus those accepted through the emergency department (ED) in a hub-and-spoke telestroke network.

Methods

Consecutive patients transferred for EVT with spoke CTA-confirmed LVO, spoke ASPECTS >6, and LKW-to-hub arrival <6 hours were identified. Our LVO2OR protocol began implementation in January 2017. The LVO2OR cohort includes patients who underwent EVT from July 2017 to October 2020; the ED cohort includes those from January 2011 to December 2016. Hub arrival-to-puncture time and 90-day modified Rankin Scale (mRS) were prospectively recorded.

Results

The LVO2OR cohort was comprised of 91 patients and the ED cohort 90. LVO2OR patients had more atrial fibrillation (AF, 51% vs 32%, p=0.02) and more M2 occlusions (27% vs 10%, p=0.01). LVO2OR patients had faster median hub arrival-to-puncture time (11 vs 92 minutes, p<0.001), faster median telestroke consult-to-puncture time (2.4 vs 3.6 hours, p<0.001), greater TICI 2b-3 reperfusion (92% vs 69%, p<0.001), and greater 90-day mRS <2 (35% vs 21%, p=0.04). In a multivariable model, LVO2OR significantly increased the odds of 90-day mRS <2 (aOR 2.77, 95%CI 1.07,7.20; p=0.04) even when controlling for age, baseline mRS, AF, NIHSS, M2 location, and TICI 2b-3.

Conclusion

In a hub-and-spoke telestroke network, accepting transferred patients directly to the angio-suite was associated with dramatically reduced hub arrival-to-puncture time and may lead to improved 90-day outcomes. Direct-to-angio-suite protocols should continue to be evaluated in other regions and telestroke models.

Postoperative neutrophil-lymphocyte ratio predicts unfavorable outcome of acute ischemic stroke patients who achieve complete reperfusion after thrombectomy

Purpose

Only approximately half of anterior circulation large vessel occlusion (LVO) patients receiving endovascular treatment (EVT) have a favorable outcome. The aim of this study was to explore the association of dynamic inflammatory markers (i.e., neutrophil to lymphocyte ratios, NLR, measured at different times after EVT) as well as other potential influencing factors with unfavorable outcome among acute ischemic stroke (AIS) patients who achieved complete reperfusion after EVT.

Methods

Patients treated with EVT for LVO between January 2019 to December 2021 were prospectively enrolled. Complete reperfusion was defined as modified thrombolysis in cerebral infarction (mTICI) grade 3. A modified Rankin scale at 90 days (mRS90) of 3-6 was defined as unfavorable outcome (i.e., futile reperfusion). A logistic regression analysis was performed with unfavorable outcome as a dependent variable. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) were then used to determine the diagnostic values of NLR and other relevant factors.

Results

170 patients with complete reperfusion (mTICI 3) were included in this study. Unfavorable outcome was observed in 70 (41.2%). Higher NLR within 24h (p=0.017) and at 3-7d (p=0.008) after EVT were an independent risk factors for unfavorable outcome at 3 months. In addition, older age, higher NIHSS scores, poor collaterals, and general anesthesia were independent predictors of unfavorable outcomes. When accounting for NLR, the diagnostic efficiency improved compared to conventional characteristics.

Conclusion

Our findings suggest that advanced age, increased stroke severity, poor collaterals, general anesthesia, and NLR are independent predictors for an unfavorable clinical outcome following complete reperfusion after EVT. Neuroinflammation may merit particular attention in future studies.

Association between Early Ischemic Changes and Collaterals in Acute Stroke: A Retrospective Study

BACKGROUND AND PURPOSE

The quality of leptomeningeal collaterals may influence the speed of infarct progression in acute stroke. Our main objective was to evaluate the association of leptomeningeal collateral score and its interaction with time with ischemic changes on CT in patients with acute stroke.

MATERIALS AND METHODS

Adult patients with acute stroke symptoms and anterior circulation large-vessel occlusion on CTA from 2015 to 2019 were included. Routinely performed NCCT and multiphase CTA were reviewed to assess ASPECTS and the leptomeningeal collateral score. We built multivariate regression models to assess the association between leptomeningeal collateral score and its interaction with time and ASPECTS. Performance measures to predict poor ASPECTS at different time thresholds (identified with receiver operating characteristic curve analysis) were estimated in a subgroup of patients with poor leptomeningeal collateral scores.

RESULTS

Leptomeningeal collateral scores 0-1 were associated with lower ASPECTS, and the model with dichotomized and trichotomized leptomeningeal collateral score showed a significant multiplicative interaction between time and the leptomeningeal collateral score. The negative predictive value for poor ASPECTS was >0.9 for at least the first 3 hours from stroke onset to imaging, and the positive predictive value was <0.5 for every time threshold tested in the subgroup of patients with leptomeningeal collateral scores 0-3.

CONCLUSIONS

Poor (0-1) leptomeningeal collateral scores were associated with lower ASPECTS, and an increase in time has a multiplicative interaction with the leptomeningeal collateral score on ASPECTS.

Characterizing reasons for stroke thrombectomy ineligibility among potential candidates transferred in a hub-and-spoke network

Background

Access to endovascular thrombectomy (EVT) is relatively limited. Hub-and-spoke networks seek to transfer appropriate large vessel occlusion (LVO) candidates to EVT-capable hubs. However, some patients are ineligible upon hub arrival, and factors that drive transfer inefficiencies are not well described. We sought to quantify EVT transfer efficiency and identify reasons for EVT ineligibility.

Methods

Consecutive EVT candidates presenting to 25 spokes from 2018-2020 with pre-transfer CTA-defined LVO and ASPECTS ≥6 were identified from a prospectively maintained database. Outcomes of interest included hub EVT, reasons for EVT ineligibility, and 90-day modified Rankin Scale (mRS) ≤2.

Results

Among 258 patients, the median age was 70 years (IQR 60-81); 50% were female. 56% were ineligible for EVT after hub arrival. Cited reasons were large established infarct (49%), mild symptoms (33%), recanalization (6%), distal occlusion (5%), sub-occlusive lesion (3%), and goals of care (3%). Late window patients [last known well (LKW) >6 hours] were more likely to be ineligible (67% vs 43%, P<0.0001). EVT ineligible patients were older (73 vs 68 years, p=0.04), had lower NIHSS (10 vs 16, p<0.0001), longer LKW-hub arrival time (8.4 vs 4.6 hours, p<0.0001), longer spoke Telestroke consult-hub arrival time (2.8 vs 2.2 hours, p<0.0001), and received less intravenous thrombolysis (32% vs 45%, p=0.04) compared to eligible patients. EVT ineligibility independently reduced the odds of 90-day mRS≤2 (aOR=0.26, 95%CI=0.12,0.56; p=0.001) when controlling for age, NIHSS, and LKW-hub arrival time.

Conclusions

Among patients transferred for EVT, there are multiple reasons for ineligibility upon hub arrival, with most excluded for infarct growth and mild symptoms. Understanding factors that drive transfer inefficiencies is important to improve EVT access and outcomes.

Diffusion MR Imaging of Large Vessel Occlusion Ischemic Stroke for Treatment Selection

The role of MR imaging in the evaluation and management of ischemic stroke patients is large, and to cover it all is far beyond the scope of one article. Thus, the focus will be on the role of MR imaging in the great leap forward in stroke therapy: endovascular thrombectomy of large vessel occlusions (LVOs). Diffusion MR imaging has played a key role in the research leading to the current standard of care for LVO stroke because it is the most sensitive and reliable method for the early delineation of the ischemic core.

Diagnosis of Ischemic Stroke: As Simple as Possible

The absolute majority of strokes in high-income countries, roughly 91%, are of ischemic origin. This review is focused on acute ischemic stroke (AIS) with large vessel occlusion (LVO) in the anterior circulation, which is considered the most devastating subtype of AIS. Moreover, stroke survivors impose substantial direct and indirect costs of care as well as costs due to productivity loss. We review of diagnostic possibilities of individual imaging methods such as computed tomography and magnetic resonance imaging, and discuss their pros and cons in the imaging of AIS. The goals of non-invasive imaging in AIS are as follows: (a) to rule out intracranial hemorrhage and to quickly exclude hemorrhagic stroke and contraindications for intravenous thrombolysis; (b) to identify potential LVO and its localization and to quickly provide guidance for endovascular treatment; (c) to assess/estimate the volume or size of the ischemic core. We suggest fast diagnostic management, which is able to quickly satisfy the above-mentioned diagnostic goals in AIS with LVO.

Benefits of Endovascular Treatment in Late Window for Acute Ischemic Stroke Selected without CT Perfusion: A Real-World Study

Objective

This study examined the functional outcomes and safety of endovascular treatment (EVT) in acute ischemic stroke (AIS) patients owing to large vessel occlusion of the anterior circulation, presented during a late-time window (6–24 hours after last seen well (LSW)) in a real-world practice.

Methods

This was a retrospective analysis from a bi-center prospective cohort. According to the stroke treatment, patients with continuous Alberta Stroke Plan Early Aspect score (ASPECTS) ≥6 on non-contrast CT (NCCT) and moderate to good collateral state on CT angiography (CTA) were divided into EVT group and standard medical treatment (SMT) group. The primary outcome was the rate of functional independence (90-day mRS ≤2). Safety outcomes were the occurrence of symptomatic intracranial hemorrhage (sICH) and the 90-day mortality.

Results

Among the 288 enrolled patients (53.5% male, median age 64 years), there were 167 patients in the EVT group and 121 in the SMT group. After multivariable adjustments for potential confounders, EVT was associated with functional independence (adjusted OR: 3.052; 95% confidence interval (CI): 1.553–5.997; p = 0.001). In the PSM cohort, 44.2% (42/95) of patients in the EVT group versus 18.9% (18/95) in the SMT group achieved functional independence (OR: 3.39, 95% CI: 1.763–6.517), and there was a significant difference favoring EVT over the SMT in the overall distribution of mRS (OR: 2.170, 95% CI: 1.302–3.618) at 90 days. The rate of sICH did not differ between the EVT and SMT groups (10.5% vs 8.4%, p = 0.804) nor did 90-day mortality (18.9% vs 22.1%, p = 0.719). No interaction was found in p-values with statistical significance in subgroup analysis.

Conclusion

This real-world experience suggests that EVT for late-presenting stroke patients, based on small core on NCCT and moderate to good collaterals on CTA, is associated with better outcomes than SMT alone, with no increase in sICH and 90-day mortality rates.