Cerebral Collateral Circulation: A Review in the Context of Ischemic Stroke and Mechanical Thrombectomy

A one-dimensional computational model for blood flow in an elastic blood vessel with a rigid catheter

Strokes are one of the leading causes of death in the United States. Stroke treatment involves removal or dissolution of the obstruction (usually a clot) in the blocked artery by catheter insertion. A computer simulation to systematically plan such patient-specific treatments needs a network of about 105 blood vessels including collaterals. The existing computational fluid dynamic (CFD) solvers are not employed for stroke treatment planning as they are incapable of providing solutions for such big arterial trees in a reasonable amount of time. This work presents a novel one-dimensional mathematical formulation for blood flow modeling in an elastic blood vessel with a centrally placed rigid catheter. The governing equations are first-order hyperbolic partial differential equations, and the hypergeometric function needs to be computed to obtain the characteristic system of these hyperbolic equations. We employed the Discontinuous Galerkin method to solve the hyperbolic system and validated the implementation by comparing it against a well-established 3D CFD solver using idealized vessels and a realistic truncated arterial network. The results showed clinically insignificant differences in steady flow cases, with overall variations between 1D and 3D models remaining below 10%. Additionally, the solver accurately captured wave reflection phenomena at domain discontinuities in unsteady cases. A primary advantage of this model over 3D solvers is its ease in obtaining a discretized geometry of complex vasculatures with multiple arterial branches. Thus, the 1D computational model offers good accuracy and applicability in simulating complex vasculatures, demonstrating promising potential for investigating patient-specific endovascular interventions in strokes.

A Deep Learning Approach to Predict Recanalization First-Pass Effect following Mechanical Thrombectomy in Patients with Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Following endovascular thrombectomy in patients with large-vessel occlusion stroke, successful recanalization from 1 attempt, known as the first-pass effect, has correlated favorably with long-term outcomes. Pretreatment imaging may contain information that can be used to predict the first-pass effect. Recently, applications of machine learning models have shown promising results in predicting recanalization outcomes, albeit requiring manual segmentation. In this study, we sought to construct completely automated methods using deep learning to predict the first-pass effect from pretreatment CT and MR imaging.

MATERIALS AND METHODS

Our models were developed and evaluated using a cohort of 326 patients who underwent endovascular thrombectomy at UCLA Ronald Reagan Medical Center from 2014 to 2021. We designed a hybrid transformer model with nonlocal and cross-attention modules to predict the first-pass effect on MR imaging and CT series.

RESULTS

The proposed method achieved a mean 0.8506 (SD, 0.0712) for cross-validation receiver operating characteristic area under the curve (ROC-AUC) on MR imaging and 0.8719 (SD, 0.0831) for cross-validation ROC-AUC on CT. When evaluated on the prospective test sets, our proposed model achieved a mean ROC-AUC of 0.7967 (SD, 0.0335) with a mean sensitivity of 0.7286 (SD, 0.1849) and specificity of 0.8462 (SD, 0.1216) for MR imaging and a mean ROC-AUC of 0.8051 (SD, 0.0377) with a mean sensitivity of 0.8615 (SD, 0.1131) and specificity 0.7500 (SD, 0.1054) for CT, respectively, representing the first classification of the first-pass effect from MR imaging alone and the first automated first-pass effect classification method in CT.

CONCLUSIONS

Results illustrate that both nonperfusion MR imaging and CT from admission contain signals that can predict a successful first-pass effect following endovascular thrombectomy using our deep learning methods without requiring time-intensive manual segmentation.

Communicating Arteries and Leptomeningeal Collaterals: A Synergistic but Independent Effect on Patient Outcomes after Stroke

The collateral system is a compensatory mechanism activated in the acute phase of an ischemic stroke. It increases brain perfusion to the hypoperfused area. Arteries of the Willis' circle supply antegrade blood flow, while pial (leptomeningeal) arteries direct blood via retrograde flow. The aim of our retrospective study was to investigate the relationship between both collateral systems, computed tomography perfusion (CTP) values, and functional outcomes in acute stroke patients. Overall, 158 patients with anterior circulation stroke who underwent mechanical thrombectomy were included in the study. We analyzed the presence of communicating arteries and leptomeningeal arteries on computed tomography angiography. Patients were divided into three groups according to their collateral status. The main outcomes were the rate of functional independence 3 months after stroke (modified Rankin scale score, mRS) and mortality rate. Our study suggests that the collateral status, as indicated by the three groups (unfavorable, intermediate, and favorable), is linked to CT perfusion parameters, potential recuperation ratio, and stroke outcomes. Patients with favorable collateral status exhibited smaller core infarct and penumbra volumes, higher mismatch ratios, better potential for recuperation, and improved functional outcomes compared to patients with unfavorable or intermediate collateral status.

Remote Ischemic Conditioning Enhances Collateral Circulation Through Leptomeningeal Anastomosis and Diminishes Early Ischemic Lesions and Infarct Volume in Middle Cerebral Artery Occlusion

Remote ischemic conditioning (RIC) has attracted much attention as a protective strategy for the heart and brain, although the underlying mechanisms remain unclear. We hypothesized that RIC enhances collateral circulation during cerebral ischemia through endothelial function and mitigates both early ischemic change and final infarct volume. We tested the RIC and sham procedure 30 min after permanent middle cerebral artery occlusion (MCAO) in male mice. Collateral circulation was examined during the procedure with 2D color-coded ultrasound imaging. Immediately after four cycles of RIC, early ischemic lesions on magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), and development of pial collateral vessels were examined. The neurological signs and infarct volume with TTC were examined until 48 h after daily RIC. As compared with sham procedure, RIC enhanced collateral circulation, diminished early ischemic lesions, enlarged pial collaterals, and mitigated infarct volume. Next, we examined the effect of inhibitor of nitric oxide synthase (NOS) and Akt on the beneficial effect of RIC in MCAO. Both allosteric Akt inhibitor, 8-[4-(1-Aminocyclobutyl)phenyl]-9-phenyl[1,2,4]triazolo[3,4-f][1,6]naphthyridin-3(2H)-one (MK2206), and two NOS inhibitors, N5-(1-Iminoethyl)-L-ornithine dihydrochloride (L-NIO) and NG-Nitro-L-arginine methyl ester hydrochloride (L-NAME), counteracted the beneficial effect of RIC on collateral circulation, early lesions, pial anastomosis, and infarct volume. In permanent MCAO, RIC could enhance collateral circulation through leptomeningeal anastomosis with Akt-eNOS pathway and diminish early lesion and final infarct volume.

Prognostic value of the baseline magnetic resonance score in patients with acute posterior circulation ischaemic stroke after mechanical thrombectomy

AIM

To investigate the prognostic value of the composite posterior circulation Acute Stroke Prognosis Early Computed tomography (CT) Score (ASPECTS)-Collaterals (pcASCO) score, which combines diffusion-weighted imaging (DWI) posterior circulation ASPECTS (pcASPECTS) and the magnetic resonance angiography (MRA)-collateral circulation score at baseline among patients with acute posterior circulation ischaemic stroke after mechanical thrombectomy.

MATERIALS AND METHODS

Patients with acute posterior circulation ischaemic stroke who underwent mechanical thrombectomy were analysed retrospectively. The DWI-pcASPECTS and MRA-collateral circulation score before treatment and the modified Rankin Scale (mRS) at 90 days after treatment were used as the endpoints. An mRS ≤2 was defined as a good prognosis, and an mRS ≥3 was defined as a poor prognosis. Multivariate logistic regression was used to analyse independent predictors of functional outcome 90 days after mechanical thrombectomy.

RESULTS

Mechanical thrombectomy was performed in 57 patients; 38 patients had a good prognosis, 19 patients had a poor prognosis, and 33 patients were successfully recanalised. Univariate logistic regression found that National Institute of Health Stroke Scale (NIHSS) score (OR: 1.18, p<0.001), pcASPECTS (OR: 1.91, p=0.028) and pcASCO score (OR: 0.51, p=0.001) were factors of good functional outcome. Receiver operating characteristic curve (ROC curve) analysis showed that the diagnostic efficiency of the NIHSS and pcASCO was better (AUC = 0.88, 0.83, p<0.05) than that of the pcASPECTS (AUC = 0.65). The prediction model was established by age, NIHSS, and pcASCO, and the diagnostic efficiency of the prediction model was better (AUC = 0.94).

CONCLUSIONS

The composite MR-pcASCO score can be used as an important predictor of the prognosis of patients with acute posterior circulation ischaemic stroke after mechanical thrombectomy.

Effect of arteriosclerotic intracranial arterial vessel wall enhancement on downstream collateral flow

BACKGROUND

The effect of arteriosclerotic intracranial arterial vessel wall enhancement (IAVWE) on downstream collateral flow found in vessel wall imaging (VWI) is not clear. Regardless of the mechanism underlying IAVWE on VWI, damage to the patient's nervous system caused by IAVWE is likely achieved by affecting downstream cerebral blood flow. The present study aimed to investigate the effect of arteriosclerotic IAVWE on downstream collateral flow.

METHODS

The present study recruited 63 consecutive patients at the Second Hospital of Hebei Medical University from January 2021 to November 2021 with underlying atherosclerotic diseases and unilateral middle cerebral artery (MCA) M1-segment stenosis who underwent an magnetic resonance scan within 3 days of symptom onset. The patients were divided into 4 groups according to IAVWE and the stenosis ratio (Group 1, n = 17; Group 2, n = 19; Group 3, n = 13; Group 4, n = 14), and downstream collateral flow was analyzed using three-dimensional pseudocontinuous arterial spin labeling (3D-pCASL) and RAPID software. The National Institutes of Health Stroke Scale (NIHSS) scores of the patients were also recorded. Two-factor multivariate analysis of variance using Pillai's trace was used as the main statistical method.

RESULTS

No statistically significant difference was found in baseline demographic characteristics among the groups. IAVWE, but not the stenosis ratio, had a statistically significant significance on the late-arriving retrograde flow proportion (LARFP), hypoperfusion intensity ratio (HIR), and NIHSS scores ( F = 20.941, P <0.001, Pillai's trace statistic = 0.567). The between-subject effects test showed that IAVWE had a significant effect on the three dependent variables: LARFP ( R2 = 0.088, F = 10.899, P = 0.002), HIR ( R2 = 0.234, F = 29.354, P <0.001), and NIHSS ( R2 = 114.339, F = 33.338, P <0.001).

CONCLUSIONS

Arteriosclerotic IAVWE significantly reduced downstream collateral flow and affected relevant neurological deficits. It was an independent factor affecting downstream collateral flow and NIHSS scores, which should be a focus of future studies.

TRIAL REGISTRATION

ChiCTR.org.cn, ChiCTR2100053661.

Computational modeling of multiscale collateral blood supply in a whole-brain-scale arterial network

The cerebral arterial network covering the brain cortex has multiscale anastomosis structures with sparse intermediate anastomoses (O[102] μm in diameter) and dense pial networks (O[101] μm in diameter). Recent studies indicate that collateral blood supply by cerebral arterial anastomoses has an essential role in the prognosis of acute ischemic stroke caused by large vessel occlusion. However, the physiological importance of these multiscale morphological properties-and especially of intermediate anastomoses-is poorly understood because of innate structural complexities. In this study, a computational model of multiscale anastomoses in whole-brain-scale cerebral arterial networks was developed and used to evaluate collateral blood supply by anastomoses during middle cerebral artery occlusion. Morphologically validated cerebral arterial networks were constructed by combining medical imaging data and mathematical modeling. Sparse intermediate anastomoses were assigned between adjacent main arterial branches; the pial arterial network was modeled as a dense network structure. Blood flow distributions in the arterial network during middle cerebral artery occlusion simulations were computed. Collateral blood supply by intermediate anastomoses increased sharply with increasing numbers of anastomoses and provided one-order-higher flow recoveries to the occluded region (15%-30%) compared with simulations using a pial network only, even with a small number of intermediate anastomoses (≤10). These findings demonstrate the importance of sparse intermediate anastomoses, which are generally considered redundant structures in cerebral infarction, and provide insights into the physiological significance of the multiscale properties of arterial anastomoses.

Stroke imaging modality for endovascular therapy in the extended window: systematic review and meta-analysis

BACKGROUND

In anterior circulation large vessel occlusion (LVO) in the extended time window, the guidelines recommend advanced imaging (ADVI) to select patients for endovascular therapy (EVT). However, questions remain regarding its availability and applicability in the real world. It is unclear whether an approach to the extended window EVT that does not use ADVI would be equivalent.

METHODS

In April 2022, a literature search was performed to identified randomized controlled trials (RCT) and observational studies describing 90-day outcomes. We performed a meta-analysis of the proportion of aggregate using a random effect to estimate rates of functional independence, defined as modified Rankin Scale (mRS) score ≤2 at 90 days, mean mRS, mortality and symptomatic intracranial hemorrhage (sICH) stratified by imaging modality.

RESULTS

Four RCTs and 28 observational studies were included. The pooled proportion of functional independence among patients selected by ADVI was 44% (95% CI 39% to 48%; I2=80%) and 48% (95% CI 41% to 55%; I2=75%) with non-contrast CT/CT angiography (NCCT/CTA) (p=0.36). Mean mRS with ADVI was 2.88 (95% CI 2.36 to 3.41; I2=0.0%) and 2.79 (95% CI 2.31 to 3.27; I2=0.0%) with NCCT (p=0.79). Mortality in patients selected by ADVI was 13% (95% CI 10% to 17%; I2=81%) and 16% (95% CI 12% to 22%; I2=69%) with NCCT (p=0.29). sICH with ADVI was 4% (95% CI 3% to 7%; I2=73%) and 6% with NCCT/CTA (95% CI 4% to 8%; I2=6%, p=0.27).

CONCLUSIONS

Our study suggests that, in anterior circulation LVO, the rates of functional independence may be similar when patients are selected using ADVI or NCCT for EVT in the extended time window. A simplified triage protocol does not seem to increase mortality or sICH. PROTOCOL REGISTRATION NUMBER: (PROSPERO ID: CRD42021236092).

Case report: Flow changes in routes of collateral circulation in patients with LVO and low NIHSS: a point favor to treat

The effectiveness of endovascular thrombectomy in patients presenting low National Institutes of Health Stroke Scale (NIHSS) scores remains controversial, and the acquisition of additional evidence is required to refine the selection of candidates who may benefit the most from this therapeutic modality. In this study, we present the case of a 62-year-old individual, with left internal carotid occlusion stroke and low NIHSS, who had compensatory collateral flow from Willis polygon via the anterior communicating artery. The patient subsequently exhibited neurological deterioration and collateral flow failure from Willis polygon, indicating the need for urgent intervention. The study of collaterals in patients with large vessel occlusion stroke has garnered considerable attention, with research suggesting that individuals with low NIHSS scores and poor collateral profiles may be at a heightened risk of early neurological deterioration. We postulate that such patients may derive significant benefits from endovascular thrombectomy, and may posit that an intensive transcranial Doppler monitoring protocol could facilitate the identification of suitable candidates for such intervention.

Association of pre-mechanical thrombectomy collateral scores with functional outcomes in the early versus extended window for thrombectomy

Introduction: Cerebral collateral circulation refers to the anastomoses that reroute the blood flow to the ischemic penumbra in the event of a large vessel occlusion (LVO). We aim to determine the utility of pre-mechanical-thrombectomy (MT) collateral scores in the early (<6 h from onset) versus extended (6-24 h from onset) window for MT with respect to a 3-month functional outcome, 3-month mortality, and early neurological improvement. Methods: We performed a retrospective chart review of patients who underwent MT for an anterior circulation LVO at a comprehensive stroke center from 7/2014 to 12/2020. A board-certified neuroradiologist, who was blinded to the clinical outcomes, used the collateral grading scales of Miteff (ordinal), Maas (ordinal), and modified-Tan (dichotomous) to designate collateral scores on the pre-MT CT Angiogram. The patients were divided into early (<6 h from onset) versus extended (6-24 h from onset) window groups depending on their timing of presentation to the emergency department. A regression analysis was performed, controlling for the baseline parameters, with the pre-MT collateral grading scores as predictors. The outcome measures were a good functional outcome (3-month mRS 0-2), mortality, and early neurological improvement. Results: A total of 220 patients met the inclusion criteria. In the overall cohort, the pre-MT scale of Maas was associated with a good functional outcome (OR, 0.58; 95% CI, 0.34-0.99; P 0.047) and mortality (OR, 0.55; 95% CI, 0.31-0.97; P 0.036). For the 162 patients who presented in the early window for MT, all of three pre-MT scales of Maas (OR, 0.39; 95% CI, 0.2-0.77; P 0.006), Miteff (OR, 0.43; 95% CI, 0.19-0.97; P 0.042) and modified-Tan (OR, 5.62; 95% CI, 1.16-27.37; P 0.033) were associated with a good functional outcome, whereas the Maas (OR, 0.48; 95% CI, 0.26-0.9; P 0.021) and the Miteff scale (OR, 0.4; 95% CI, 0.22-0.74; P 0.003) were associated with mortality. For the 58 patients who presented in the extended window for MT, none of the collateral grades were associated with functional outcome, mortality, or early neurological improvement. Conclusions: Our study demonstrates that while several collateral grades are helpful to predict outcomes in patients presenting in the early window, none of the pre-MT collateral scores were associated with outcomes in patients who presented in the extended window for MT. Thus, the current strategy of using perfusion imaging for the selection of patients for MT in the extended window should continue.

Association between Cerebrovascular Risk Factors and Collateral Compensation in Chronic Symptomatic Intracranial Vertebrobasilar Stenosis

INTRODUCTION

The level of collateral compensation plays a pivotal role in chronic symptomatic intracranial vertebrobasilar stenosis (IVBS). This study aimed to evaluate the association between cerebrovascular risk factors and collateral compensation in chronic symptomatic IVBS.

METHODS

This single-center cross-sectional study retrospectively reviewed 238 patients with angiographically demonstrated IVBS and divided them into good collateral compensation (GCC) group (collateral grade: 3-4, n = 110) and poor collateral compensation (PCC) group (collateral grade: 0-2, n = 128). The demographic information, laboratory tests, and clinical data of the two groups were compared and assessed using univariate logistic regression. Multivariate logistic regression was employed to analyze the independent related factors of collateral compensation.

RESULTS

Hyperlipidemia, high-density lipoprotein (HDL), and fasting blood glucose (FBG) were significantly different between the two groups. Multivariate logistic regression analysis revealed that HDL (odds ratio [OR]: 1.134, 95% confidence interval [CI]: 1.081-1.190), FBG (OR: 0.945, 95% CI: 0.925-0.964), and hyperlipidemia (OR: 0.261, 95% CI: 0.129-0.527) were statistically independent related factors of collateral compensation. The receiver-operating characteristic (ROC) analysis provided cutoff values of 34 mg/dL and 135 mg/dL for HDL and FBG associated with GCC and PCC.

CONCLUSION

Higher HDL levels are associated with higher incidence of GCC, whereas higher FBG levels and hyperlipidemia are associated with higher incidence of PCC.

Cavitation-assisted sonothrombolysis by asymmetrical nanostars for accelerated thrombolysis

Sonothrombolysis with recombinant tissue plasminogen activator (rtPA) and microbubbles has been widely studied to enhance thrombolytic potential. Here, we report different sonothrombolysis strategy in nanoparticles using microbubbles cavitation. We found that different particles in shape exhibited different reactivity toward the cavitation, leading to a distinct sonothrombolytic potential. Two different gold nanoparticles in shape were functionalized with the rtPA: rtPA-functionalized gold nanospheres (NPt) and gold nanostars (NSt). NPt could not accelerate the thrombolytic potential with a sole acoustic stimulus. Importantly, NSt enhanced the potential with acoustic stimulus and microbubble-mediated cavitation, while NPt were not reactive to cavitation. Coadministration of NSt and microbubbles resulted in a dramatic reduction of the infarcts in a photothrombotic model and recovery in the cerebral blood flow. Given the synergistic effect and in vivo feasibility of this strategy, cavitation-assisted sonothrombolysis by asymmetrical NSt might be useful for treating acute ischemic stroke.

Cerebral small vessel disease combined with cerebral collaterals to predict the prognosis of patients with acute large artery atherosclerotic stroke

Background and purpose

Besides cerebral collaterals, few studies have examined other additional factors affecting the prognosis of patients with large artery atherosclerotic (LAA) stroke. Our study aims to explore the effect of the cerebral small vessel disease (SVD) and the effects of its interaction with cerebral collaterals on the prognosis of patients with acute LAA stroke.

Method

Patients aged 18 years or older with LAA stroke within 24 h after stroke onset were consecutively enrolled. The functional outcome was determined using the modified Rankin Scale (mRS) at 3 months after stroke onset. Logistic multivariate analyses were used to identify the risk factors for stroke prognosis. Receiver operating characteristic (ROC) curves were constructed to compare the effects of cerebral collaterals and SVD on predicting the prognosis.

Results

Of the 274 enrolled patients, 174 (63.50%) were identified as having a favorable prognosis, and 100 (36.50%) were identified as having an unfavorable prognosis. After adjusting for covariates, the logistic regression analysis identified that unfavorable prognosis was related to the total SVD score (Model 1, adjusted odds ratio = 1.73, 95% CI: 1.15–2.61, P < 0.01; Model 2, adjusted odds ratio = 1.85, 95% CI: 1.23–2.79, P < 0.01) and Tan score (Model 1, adjusted odds ratio = 0.38, 95% CI: 0.23–0.64, P < 0.01; Model 2, adjusted odds ratio = 0.52, 95% CI: 0.33–0.82, P < 0.01). Compared with cerebral collaterals (AUC = 0.59; 95% CI: 0.52–0.67; P < 0.01) or SVD (AUC = 0.62; 95% CI: 0.56–0.69; P < 0.01) alone, the combination of collaterals and SVD (AUC = 0.66; 95% CI: 0.59–0.73; P < 0.01) had higher diagnostic value for an unfavorable prognosis, and the optimal sensitivity and specificity were 77.01 and 53.00%, respectively.

Conclusions

The total SVD burden was related to the prognosis of patients with LAA stroke. Compared with cerebral collaterals or SVD alone, cerebral collaterals combined with total SVD burden are better at predicting the prognosis of patients with acute LAA stroke.

Interplay between anemia parameters and collateral status in patients who undergo mechanical thrombectomy

INTRODUCTION

Anemia is associated with higher morbidity and mortality, but its association with acute ischemic stroke (AIS) is not well established. We aim to determine the association of five-day anemia parameters with clinical outcomes in patients with an AIS, depending on their pre-mechanical thrombectomy (MT) collateral status.

METHODS

We performed a retrospective chart review of patients who underwent MT at a comprehensive stroke center from 7/2014 to 12/2020. The patients were divided into good and poor collateral groups depending on their pre-MT collateral status. A blinded board-certified neuroradiologist used collateral grading scale of Maas ≥ 3 to designate good collaterals on the pre-MT CT Angiogram. A binary logistic regression analysis was performed, controlling for the baseline parameters, with the five-day anemia parameters as predictors. The outcomes were functional independence (mRS 0-2), mortality, and early neurological improvement.

RESULTS

A total of 220 met the inclusion criteria. 94 (42.72 %) patients had good collaterals, while 126 (57.27 %) patients had poor collaterals. In the multivariable analysis, for patients with good collaterals, the higher values of five-day mean Hb (12.41 ± 1.87 vs 11.32 ± 1.95; OR, 0.72; 95 % CI, 0.54-0.95; P 0.018), five-day mean HCT (37.43 ± 5.1 vs 34.35 ± 5.5; OR, 0.89; 95 % CI, 0.81-0.98; P 0.018) and lower values of the difference between peak and trough values of Hb (1.75 ± 1.15 vs 2.41 ± 1.35; OR, 1.71; 95 % CI, 1.07-2.74; P 0.025) were associated with functional independence. For patients with poor collaterals, there was no association between five-day mean Hb, mean HCT parameters with functional independence, lower mortality, and early neurological improvement.

CONCLUSION

Our study was suggestive of an association between higher mean values of Hb and HCT over a five-day period and good clinical outcomes in patients with good collaterals who undergo MT for an anterior circulation LVO. This association was not found in the poor collateral group.

Identifying 'fast progressors' likely to benefit from mechanical thrombectomy

OBJECTIVES

Although the effect of mechanical thrombectomy in large vessel occlusions has been clearly demonstrated, there are different opinions about the treatment of patients with low ASPECT scores. We conducted this research to explore the utility of mechanical thrombectomy for the fast progressor patients.

METHODS

We evaluated 394 patients with large vessel occlusion (LVO) who applied to our center between 2012 and 2020 retrospectively. Patients with posterior system stroke and who admitted 6 h after the onset of symptoms, were not included in the study. The remaining 256 patients were divided into two groups as computed tomography angiography source image Alberta stroke program early computer tomography score (CTA-SI ASPECT) ≤ 6 and > 6. Modified rankin scale (mRS) 0-2 defined as good clinical outcome. Thrombolysis in cerebral infarction (TICI) score 2c-3 was accepted as successful recanalization.

RESULTS

The mean age of the patients in the fast-progressive group (23.4%; n = 60) was 66.3 ± 11.6 years, whereas the mean age of the CTA-SI ASPECTS > 6 group (76.6%; n = 196) was 62.4 ± 12.8 years (p = 0.034) A statistically significant difference was found between the groups regarding 90-day mRS (p < 0.001). Whereas 61.7% of the patients with a CTA-SI ASPECTS > 6 had a 90-day mRS 0-2, this rate was 28.3% for patients with a CTA-SI ASPECTS ≤ 6.

CONCLUSION

According to our study, approximately 1/3 of patients with ASPECTS ≤ 6 benefit from mechanical thrombectomy. In this patient group, age emerged as a determinant of good clinical outcome.

Nomogram to predict 3-month unfavorable outcome after thrombectomy for stroke

Background

Mechanical thrombectomy (MT) is an effective treatment for large-vessel occlusion in acute ischemic stroke, however, only some revascularized patients have a good prognosis. For stroke patients undergoing MT, predicting the risk of unfavorable outcomes and adjusting the treatment strategies accordingly can greatly improve prognosis. Therefore, we aimed to develop and validate a nomogram that can predict 3-month unfavorable outcomes for individual stroke patient treated with MT.

Methods

We analyzed 258 patients with acute ischemic stroke who underwent MT from January 2018 to February 2021. The primary outcome was a 3-month unfavorable outcome, assessed using the modified Rankin Scale (mRS), 3–6. A nomogram was generated based on a multivariable logistic model. We used the area under the receiver-operating characteristic curve to evaluate the discriminative performance and used the calibration curve and Spiegelhalter’s Z-test to assess the calibration performance of the risk prediction model.

Results

In our visual nomogram, gender (odds ratio [OR], 3.40; 95%CI, 1.54–7.54), collateral circulation (OR, 0.46; 95%CI, 0.28–0.76), postoperative mTICI (OR, 0.06; 95%CI, 0.01–0.50), stroke-associated pneumonia (OR, 5.76; 95%CI, 2.79–11.87), preoperative Na (OR, 0.82; 95%CI, 0.72–0.92) and creatinine (OR, 1.02; 95%CI, 1.01–1.03) remained independent predictors of 3-month unfavorable outcomes in stroke patients treated with MT. The area under the nomogram curve was 0.8791 with good calibration performance (P = 0.873 for the Spiegelhalter’s Z-test).

Conclusions

A novel nomogram consisting of gender, collateral circulation, postoperative mTICI, stroke-associated pneumonia, preoperative Na and creatinine can predict the 3-month unfavorable outcomes in stroke patients treated with MT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02633-1.

The Overexpression of Sonic Hedgehog Associates with Collateral Development and Amelioration of Oxidative Stress in Stroke Patients

PURPOSE

Sonic hedgehog (SHH) signaling pathway in oxidative stress condition has been acknowledged as a key trigger for angiogenesis and collateral vessel growth in the ischemic brain, and it exerts a protective effect on neuronal cells during oxidative stress.

METHODS

A total of sixty patients (n = 30 good collateral profile and n = 30 poor collateral profile) diagnosed with acute cerebral ischemia were enrolled in this study. qRT-PCR was performed to analyze the expression levels of SHH, Gli1, and superoxide dismutase (SOD), genes. Also, the serum levels of oxidative stress markers were determined in experimental groups.

RESULTS

The expression levels of SHH and Gli1 genes were significantly (p < 0.05) higher in stroke patients with good collateral circulation compared with those with poor collateral circulation, while SOD gene expression was similar between two groups (p > 0.05). A significantly positive correlation was found between the gene expression of SHH and Gli1 (r = 0.604, p < 0.001), SOD and Gli1 (r = 0.372, p < 0.003) genes. Our findings showed that the serum level of total antioxidant capacity (TAC) and Glutathione (GSH) and SOD enzyme activity was significantly (p < 0.05) increased, while serum total oxidant status (TOS) and malondialdehyde (MDA) levels were significantly (p < 0.05) decreased in patients with good collateral circulation as compared with those with poor collateral circulation.

CONCLUSION

Our observations shed light on the association of the SHH/Gli1 signaling pathway with cerebral collateral vessel development following ischemia. Oxidative stress in stroke patients with poor collateral circulation may result in the overexpression of SHH/Gli1 signaling pathway which possibly contribute to oxidative stress attenuation, as well as modulate angiogenesis and collateral vessels development.

Leptomeningeal anastomoses: Mechanisms of pial collateral remodeling in ischemic stroke

Arterial collateralization, as determined by leptomeningeal anastomoses or pial collateral vessels, is a well‐established vital player in cerebral blood flow restoration and neurological recovery from ischemic stroke. A secondary network of cerebral collateral circulation apart from the Circle of Willis, exist as remnants of arteriole development that connect the distal arteries in the pia mater. Recent interest lies in understanding the cellular and molecular adaptations that control the growth and remodeling, or arteriogenesis, of these pre‐existing collateral vessels. New findings from both animal models and human studies of ischemic stroke suggest a multi‐factorial and complex, temporospatial interplay of endothelium, immune and vessel‐associated cell interactions may work in concert to facilitate or thwart arteriogenesis. These valuable reports may provide critical insight into potential predictors of the pial collateral response in patients with large vessel occlusion and may aid in therapeutics to enhance collateral function and improve recovery from stroke.

This article is categorized under:

Neurological Diseases > Molecular and Cellular Physiology

Evolution of Hypodensity on Non-Contrast CT in Correlation with Collaterals in Anterior Circulation Stroke with Successful Endovascular Reperfusion

Introduction: The aim of the study was to assess the impact of collaterals on the evolution of hypodensity on non-contrast CT (NCCT) in anterior circulation stroke with reperfusion by mechanical thrombectomy (MT). Methods: We retrospectively included stroke patients with middle cerebral artery occlusion who were reperfused by MT in early and late time window. Artificial intelligence (AI)-based software was used to calculate of hypodensity volumes at baseline NCCT (V1) and at follow-up NCCT 24 h after MT (V2), along with the difference between the two volumes (V2-V1) and the follow-up (V2)/baseline (V1) volume ratio (V2/V1). The same software was used to classify collateral status by using a 4-point scale where the score of zero indicated no collaterals and the score of three represented contrast filling of all collaterals. The volumetric values were correlated with the collateral scores. Results: Collateral scores had significant negative correlation with V1 (p = 0.035), V2, V2− V1 and V2/V1 (p < 0.001). In cases with collateral score = 3, V2 was significantly smaller or absent compared to V1; in those with collateral score 2, V2 was slightly larger than V1, and in those with scores 1 and 0 V2 was significantly larger than V1. These relationships were observed in both early and late time windows. Conclusions: The collateral status determined the evolution of the baseline hypodensity on NCCT in patients with anterior circulation stroke who had MT reperfusion. Damage can be stable or reversible in patients with good collaterals while in those with poor collaterals tissues that initially appear normal will frequently appear as necrotic after 24 h. With good collaterals, it is stable or can be reversible while with poor collaterals, normal looking tissue frequently appears as necrotic in follow-up exam. Hence, acute hypodensity represents different states of the ischemic brain parenchyma.

Obstructive sleep apnea confers lower mortality risk in acute ischemic stroke patients treated with endovascular thrombectomy: National Inpatient Sample analysis 2010-2018

BackgroundObstructive sleep apnea (OSA) portends increased morbidity and mortality following acute ischemic stroke (AIS). Evaluation of OSA in the setting of AIS treated with endovascular mechanical thrombectomy (MT) has not yet been evaluated in the literature.

METHODS

The National Inpatient Sample from 2010 to 2018 was utilized to identify adult AIS patients treated with MT. Those with and without OSA were compared for clinical characteristics, complications, and discharge disposition. Multivariable logistic regression analysis and propensity score adjustment (PA) were employed to evaluate independent associations between OSA and clinical outcome.

RESULTS

Among 101 093 AIS patients treated with MT, 6412 (6%) had OSA. Those without OSA were older (68.5 vs 65.6 years old, p<0.001), female (50.5% vs 33.5%, p<0.001), and non-caucasian (29.7% vs 23.7%, p<0.001). The OSA group had significantly higher rates of obesity (41.4% vs 10.5%, p<0.001), atrial fibrillation (47.1% vs 42.2%, p=0.001), hypertension (87.4% vs 78.5%, p<0.001), and diabetes mellitus (41.2% vs 26.9%, p<0.001). OSA patients treated with MT demonstrated lower rates of intracranial hemorrhage (19.1% vs 21.8%, p=0.017), treatment of hydrocephalus (0.3% vs 1.1%, p=0.009), and in-hospital mortality (9.7% vs 13.5%, p<0.001). OSA was independently associated with lower rate of in-hospital mortality (aOR 0.76, 95% CI 0.69 to 0.83; p<0.001), intracranial hemorrhage (aOR 0.88, 95% CI 0.83 to 0.95; p<0.001), and hydrocephalus (aOR 0.51, 95% CI 0.37 to 0.71; p<0.001). Results were confirmed by PA.

CONCLUSIONS

Our findings suggest that MT is a viable and safe treatment option for AIS patients with OSA.

Predictive Value of CT Perfusion Imaging on the Basis of Automatic Segmentation Algorithm to Evaluate the Collateral Blood Flow Status on the Outcome of Reperfusion Therapy for Ischemic Stroke

Our objective was to study the predictive value of CT perfusion imaging based on automatic segmentation algorithm for evaluating collateral blood flow status in the outcome of reperfusion therapy for ischemic stroke. All data of 30 patients with ischemic stroke reperfusion in our hospital were collected and examined by CT perfusion imaging. Convolutional neural network (CNN) algorithm was used to segment perfusion imaging map and evaluate the results. The patients were grouped by regional leptomeningeal collateral score (rLMCs). Binary logistic regression was used to analyze the independent influencing factors of collateral blood flow on brain CT perfusion. The modified Scandinavian Stroke Scale was used to evaluate the prognosis of patients, and the effects of different collateral flow conditions on prognosis were obtained. The accuracy of CNN segmentation image is 62.61%, the sensitivity is 87.42%, the similarity coefficient is 93.76%, and the segmentation result quality is higher. Blood glucose (95% CI = 0.943, P=0.028) and ischemic stroke history (95% CI = 0.855, P=0.003) were independent factors affecting the collateral blood flow status of stroke patients. CBF (95% CI = 0.818, P=0.008) and CBV (95% CI = 0.796, P=0.016) were independent influencing factors of CT perfusion parameters. After 3 weeks of onset, the prognostic function defect score of the good collateral flow group (11.11%) was lower than that of the poor group (41.67%) (P < 0.05). The automatic segmentation algorithm has more accurate segmentation ability for stroke CT perfusion imaging and plays a good auxiliary role in the diagnosis of clinical stroke reperfusion therapy. The collateral blood flow state based on CT perfusion imaging is helpful to predict the treatment outcome of patients with ischemic stroke and further predict the prognosis of patients.

Cystatin C predicts futile recanalization in patients with acute ischemic stroke after endovascular treatment

BACKGROUND

A previous study reported that cystatin C was related to acute ischemic stroke. The association between cystatin C and the clinical outcome in acute ischaemic stroke patients with successful recanalization after endovascular thrombectomy has rarely been reported. This study aimed to evaluate the association between cystatin C and futile recanalization in AIS patients who underwent endovascular thrombectomy.

METHODS

We carried out a retrospective study of acute ischaemic stroke patients with anterior circulation proximal arterial occlusion who achieved complete arterial recanalization after mechanical thrombectomy from May 2017 to April 2020. The patients with complete recanalization were divided into a useful recanalization group and a futile recanalization group according to their 3-month modified Rankin scale score. FR was defined as a modified mRS score of 3-6 at 3 months. Logistic regression analysis was used to identify the risk factors for FR. Receiver operating characteristic curves were used to assess the predictive value of cystatin C for FR.

RESULTS

Of 241 patients, 125 underwent futile recanalization and 116 underwent useful recanalization. Baseline serum cystatin C levels were higher in the futile recanalization group than in the useful recanalization group. After adjustment for potential confounding factors, multivariable adjusted regression models showed that cystatin C was an independent predictor of futile recanalization (odds ratio, 4.111 [95% CI 1.427-11.840], P = 0.009). Receiver operator characteristic (ROC) curve analysis indicated that the model combining cystatin C with other factors model effectively predicted unfavourable outcomes at 3 months (area under the curve = 0.782, p < 0.01).

CONCLUSIONS

A higher level of cystatin C is associated with unfavourable outcomes at 3 months in anterior circulation acute ischaemic stroke patients with endovascular thrombectomy.

The core/penumbra model: implications for acute stroke treatment and patient selection in 2021

Despite major advances in prevention, ischaemic stroke remains one of the leading causes of death and disability worldwide. After centuries of nihilism and decades of failed neuroprotection trials, the discovery, initially in non-human primates and subsequently in man, that ischaemic brain tissue termed the ischaemic penumbra can be salvaged from infarction up to and perhaps beyond 24 h after stroke onset has underpinned the development of highly efficient reperfusion therapies, namely intravenous thrombolysis and endovascular thrombectomy, which have revolutionized the management of the acute stroke patient. Animal experiments have documented that how long the penumbra can survive depends not only on time elapsed since arterial occlusion ('time is brain'), but also on how severely perfusion is reduced. Novel imaging techniques allowing the penumbra and the already irreversibly damaged core in the individual subject to be mapped have documented that the time course of core growth at the expense of the penumbra widely differs from patient to patient, and hence that individual physiology should be considered in addition to time since stroke onset for decision-making. This concept has been implemented to optimize patient selection in pivotal trials of reperfusion therapies beyond 3 h after stroke onset and is now routinely applied in clinical practice, using computed tomography or magnetic resonance imaging. The notion that, in order to be both efficient and harmless, treatment should be tailored to each patient's physiological characteristics represents a radical move towards precision medicine.

Susceptibility-diffusion mismatch correlated with leptomeningeal collateralization in large vessel occlusion stroke

Objective

To investigate the relationship between asymmetric prominent hypointense vessels (prominent vessel sign, PVS) on susceptibility-weighted imaging (SWI) and leptomeningeal collateralization in patients with acute ischemic stroke due to large vessel occlusion.

Methods

We retrospectively enrolled patients with M1 segment occlusion of the middle cerebral artery who underwent emergency magnetic resonance imaging and digital subtraction angiography within 24 hours from stroke onset. The extent of PVS on SWI was assessed using the Alberta Stroke Program Early CT Score (ASPECTS). Leptomeningeal collateralization on digital subtraction angiography images was assessed using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) scale. Spearman’s rank correlation test was performed to explore the correlation of ASITN/SIR scores with SWI-ASPECTS and SWI-diffusion-weighted imaging (DWI) mismatch scores.

Results

Thirty-five patients were enrolled. There was no significant correlation between SWI-ASPECTS and ASITN/SIR scores. However, SWI-DWI mismatch scores were positively correlated with ASITN/SIR scores.

Conclusion

The range of PVS on SWI did not closely reflect the collateral status, while the range of SWI-DWI mismatch was significantly correlated with the leptomeningeal collateralization. In patients with acute anterior circulation stroke due to large vessel occlusion, larger SWI-DWI mismatch was associated with better leptomeningeal collaterals.

A murine photothrombotic stroke model with an increased fibrin content and improved responses to tPA-lytic treatment

The Rose Bengal (RB) dye-based photothrombotic stroke (PTS) model has many methodological advantages including consistent location and size of infarct, low mortality, and relatively simple surgical procedures. However, the standard PTS has the caveat of poor responses to tissue-type plasminogen activator (tPA)-mediated lytic treatment, likely as a result of the platelet-rich, fibrin-poor content of the blood clots. Here we tested whether the admixture of thrombin (80 U/kg) and RB dye (50 mg/kg) in the proximal middle cerebral artery (MCA)-targeted PTS will modify the clot composition and elevate the responsiveness to tPA-lytic treatment (Alteplase, 10 mg/kg). Indeed, intravital imaging, immunostaining, and immunoblot analyses showed less-compacted platelet aggregates with a higher fibrin content in the modified thrombin (T) plus RB photothrombotic stroke (T+RB-PTS) model compared with the standard RB-PTS-induced clots. Both RB-PTS and T+RB-PTS showed steady recovery of cerebral blood flow (CBF) in the ischemic border from 1 day after infarction, but without recanalization of the proximal MCA branch. Intravital imaging showed high potency of restoring the blood flow by tPA after single vessel-targeted T+RB-PTS. Further, although intravenous tPA failed to restore CBF or attenuate infarction in RB-PTS, it conferred 25% recovery of CBF and 55% reduction of the infarct size in T+RB-PTS (P < .05) if tPA was administered within 2 hours postphotoactivation. These results suggest that T+RB-PTS produces mixed platelet:fibrin clots closer to the clinical thrombus composition and enhanced the sensitivity to tPA-lytic treatment. As such, the modified photothrombosis may be a useful tool to develop more effective thrombolytic therapies of cerebral ischemia.

High-altitude rodents have abundant collaterals that protect against tissue injury after cerebral, coronary and peripheral artery occlusion

Collateral number/density varies widely in brain and other tissues among strains of Mus musculus mice due to differences in genetic background. Recent studies have shown that prolonged exposure to reduced atmospheric oxygen induces additional collaterals to form, suggesting that natural selection may favor increased collaterals in populations native to high-altitude. High-altitude guinea pigs (Cavia) and deer mice (Peromyscus) were compared with lowland species of Peromyscus, Mus and Rattus (9 species/strains examined). Collateral density, diameter and other morphometrics were measured in brain where, importantly, collateral abundance reflects that in other tissues of the same individual. Guinea pigs and high-altitude deer mice had a greater density of pial collaterals than lowlanders. Consistent with this, guinea pigs and highlander mice evidenced complete and 80% protection against stroke, respectively. They also sustained significantly less ischemia in heart and lower extremities after arterial occlusion. Vessels of the circle of Willis, including the communicating collateral arteries, also exhibited unique features in the highland species. Our findings support the hypothesis that species native to high-altitude have undergone genetic selection for abundant collaterals, suggesting that besides providing protection in obstructive disease, collaterals serve a physiological function to optimize oxygen delivery to meet oxygen demand when oxygen is limiting.

Hypoperfusion Index Ratio as a Surrogate of Collateral Scoring on CT Angiogram in Large Vessel Stroke

Background: This study was to evaluate the correlation of the hypoperfusion intensity ratio (HIR) with the collateral score from multiphase computed tomography angiography (mCTA) among patients with large vessel stroke. Method: From February 2019 to May 2020, we retrospectively reviewed the patients with large vessel strokes (intracranial carotid artery or proximal middle cerebral artery occlusion). HIR was defined as a Tmax > 10 s lesion volume divided by a Tmax > 6 s lesion volume, which was calculated by automatic software (Syngo.via, Siemens). The correlation between the HIR and mCTA score was evaluated by Pearson’s correlation. The cutoff value predicting the mCTA score was evaluated by receiver operating characteristic analysis. Result: Ninety-four patients were enrolled in the final analysis. The patients with good collaterals had a smaller core volume (37.3 ± 24.7 vs. 116.5 ± 70 mL, p < 0.001) and lower HIR (0.51 ± 0.2 vs. 0.73 ± 0.13, p < 0.001) than those with poor collaterals. A higher HIR was correlated with a poorer collateral score by Pearson’s correlation. (r = −0.64, p < 0.001). The receiver operating characteristic (ROC) analysis suggested that the best HIR value for predicting a good collateral score was 0.68 (area under curve: 0.82). Conclusion: HIR is a good surrogate of collateral circulation in patients with acute large artery occlusion.

Improving Collateral Circulation: A Potential Adjunctive Strategy to Prevent or Slow the Progression of Vascular Dementia

Vascular dementia (VaD), a cognitive disorder caused by cerebrovascular pathologies, is the most common cause of dementia in the elderly, being second only to Alzheimer's disease. Researches have shown that adequate cerebral blood flow (CBF) is the first condition for maintaining the structural integrity and normal function of the brain, and VaD is generally considered to be resulted from neuronal loss due to reduced CBF. Collateral circulation, a compensation mechanism for CBF, provides an alternative vascular pathway for blood to reach ischemic tissues, which has been confirmed to be associated with better clinical outcomes of ischemic diseases. At present, considerable effort has been devoted to enhancing the functional prognosis of acute ischemic stroke by improving collateral circulation. Since ischemic stroke is the primary contributor to VaD, it is necessary to explore whether improving collateral circulation is beneficial to prevent or slow the progression of VaD. This article reviews the compensatory characteristics of different levels of cerebral collateral circulation, addresses the relationship between collateral circulation and VaD, and highlights that improving collateral circulation may be a potential adjunctive strategy in preventing and slowing the progression of VaD.

Hemodynamics in acute stroke: Cerebral and cardiac complications

Hemodynamics is the study of blood flow, where parameters have been defined to quantify blood flow and the relationship with systemic circulatory changes. Understanding these perfusion parameters, the relationship between different blood flow variables and the implications for ischemic injury are outlined in the ensuing discussion. This chapter focuses on the hemodynamic changes that occur in ischemic stroke, and their contribution to ischemic stroke pathophysiology. We discuss the interaction between cardiovascular response and hemodynamic changes in stroke. Studying hemodynamic changes has a key role in stroke prevention, therapeutic implications and prognostic importance in acute ischemic stroke: preexisting hemodynamic and autoregulatory impairments predict the occurrence of stroke. Hemodynamic failure predisposes to the formation of thromboemboli and accelerates infarction due to impairing compensatory mechanisms. In ischemic stroke involving occlusion of a large vessel, persistent collateral circulation leads to preservation of ischemic penumbra and therefore justifying endovascular thrombectomy. Following thrombectomy, impaired autoregulation may lead to reperfusion injury and hemorrhage.

The impact of native leptomeningeal collateralization on rapid blood flow recruitment following ischemic stroke

The leptomeningeal collateral status is an independent predictor of stroke outcome. By means of optical coherent tomography angiography to compare two mouse strains with different extent of native leptomeningeal collateralization, we determined the spatiotemporal dynamics of collateral flow and downstream hemodynamics following ischemic stroke. A robust recruitment of leptomeningeal collateral flow was detected immediately after middle cerebral artery (MCA) occlusion in C57BL/6 mice, with continued expansion over the course of seven days. In contrast, little collateral recruitment was seen in Balb/C mice during- and one day after MCAO, which coincided with a greater infarct size and worse functional outcome compared to C57BL/6, despite a slight improvement of cortical perfusion seven days after MCAO. Both strains of mice experienced a reduction of blood flow in the penetrating arterioles (PA) by more than 90% 30-min after dMCAO, although the decrease of PA flow was greater and the recovery was less in the Balb/C mice. Further, Balb/C mice also displayed a prolonged greater heterogeneity of capillary transit time after dMCAO in the MCA territory compared to C57BL/6 mice. Our data suggest that the extent of native leptomeningeal collaterals affects downstream hemodynamics with a long lasting impact in the microvascular bed after cortical stroke.

Computer Modeling of Clot Retrieval-Circle of Willis

Endovascular clot retrieval, often referred to as mechanical thrombectomy, has transformed the treatment of patients with ischemic stroke based on an underlying large cerebral vessel occlusion, ranging from the extracranial internal carotid artery (ICA) to the M1 (proximal) segment of the middle cerebral artery (MCA). The aim of this study was to evaluate the effect of a progressive occlusion of the extracranial portion of the ICA on the cerebral blood flow either with a conventional guiding catheter or a balloon-guiding catheter, which enables the operator to completely occlude the parent artery by inflating the balloon around the tip of this type of guiding catheter. We evaluated the impact of flow reduction in the ICA in the setting of ipsilateral MCA occlusion given the different configurations of the circle of Willis (CoW). The computer model of cerebral arteries was based on anatomical works by Rhoton (1) and van der Eecken (2). The interactive experimental results are available on the web at https://gntem3.shinyapps.io/ecrsim. In the setting of left MCA occlusion, compensation from the anterior and posterior communicating artery preserved the flow in the left anterior cerebral artery (ACA) but not the left MCA branches. Under selected CoW configurations, such as classic, missing Acom, or missing A1 segment of the ACA and concurrent right ICA occlusion, there was a progressive decrease of flow in the left ACA to a minimum of 78% when the simulated catheter fully occluded the left ICA. Flow collapsed (<10%) in the left ACA and MCA branches under CoW configurations, such as bilateral fetal PCA. In summary, compensatory flow collapsed under certain clot retrieval scenarios and unusual configurations of CoW.

An increase in AMPK/e-NOS signaling and attenuation of MMP-9 may contribute to remote ischemic perconditioning associated neuroprotection in rat model of focal ischemia

Remote ischemic perconditioning (RIPerC) results in collateral enhancement and a reduction in middle cerebral artery occlusion (MCAO) induced ischemia. RIPerC likely activates multiple metabolic protective mechanisms, including effects on matrix metalloproteinases (MMPs) and protein kinases. Here we explore if RIPerC improves neuroprotection and collateral flow by modifying the activities of MMP-9 and AMPK/e-NOS. Age matched adult male Sprague Dawley rats were subjected to MCAO followed one hour later by RIPerC (3 cycles of 15 min ischemia). Animals were euthanized 24 h post-MCAO. Haematoxylin and Eosin (H&E) staining 24 h post-MCAO revealed a significant (p < 0.02) reduction in the infarction volume in RIPerC treated animals (24.9 ± 5.4%) relative to MCAO controls (42.5 ± 4.2, %). TUNEL staining showed a 42.6% reduction in the apoptotic cells with RIPerC treatment (p < 0.01). Immunoblotting in congruence with RT-PCR and Zymography showed that RIPerC significantly reduced MMP-9 expression and activity in RIPerC + MCAO group compared to MCAO group (218.3 ± 19.1% vs. 148.9 ± 12.05% (p < 0.01). Immunoblotting revealed that RIPerC was associated with a significant 2.5-fold increase in activation of p-AMPK compared to the MCAO group (p < 0.01) which was also associated with a significant increase in the e-NOS activity (p < 0.01). RIPerC resulted in reduction of infarction volume, decreased apoptotic cell death and attenuated MMP-9 activity. This together with the increased activity of p-AMPK and increase in p-eNOS may, in part explain the neuroprotection and sustained increase in blood flow observed with RIPerC following acute stroke.

Improved collateral flow and reduced damage after remote ischemic perconditioning during distal middle cerebral artery occlusion in aged rats

Circulation through cerebral collaterals can maintain tissue viability until reperfusion is achieved. However, collateral circulation is time limited, and failure of collaterals is accelerated in the aged. Remote ischemic perconditioning (RIPerC), which involves inducing a series of repetitive, transient peripheral cycles of ischemia and reperfusion at a site remote to the brain during cerebral ischemia, may be neuroprotective and can prevent collateral failure in young adult rats. Here, we demonstrate the efficacy of RIPerC to improve blood flow through collaterals in aged (16-18 months of age) Sprague Dawley rats during a distal middle cerebral artery occlusion. Laser speckle contrast imaging and two-photon laser scanning microscopy were used to directly measure flow through collateral connections to ischemic tissue. Consistent with studies in young adult rats, RIPerC enhanced collateral flow by preventing the stroke-induced narrowing of pial arterioles during ischemia. This improved flow was associated with reduced early ischemic damage in RIPerC treated aged rats relative to controls. Thus, RIPerC is an easily administered, non-invasive neuroprotective strategy that can improve penumbral blood flow via collaterals. Enhanced collateral flow supports further investigation as an adjuvant therapy to recanalization therapy and a protective treatment to maintain tissue viability prior to reperfusion.

Automatic collateral circulation scoring in ischemic stroke using 4D CT angiography with low-rank and sparse matrix decomposition

PURPOSE

Sufficient collateral blood supply is crucial for favorable outcomes with endovascular treatment. The current practice of collateral scoring relies on visual inspection and thus can suffer from inter and intra-rater inconsistency. We present a robust and automatic method to score cerebral collateral blood supply to aid ischemic stroke treatment decision making. The developed method is based on 4D dynamic CT angiography (CTA) and the ASPECTS scoring protocol.

METHODS

The proposed method, ACCESS (Automatic Collateral Circulation Evaluation in iSchemic Stroke), estimates a target patient's unfilled cerebrovasculature in contrast-enhanced CTA using the lack of contrast agent due to clotting. To do so, the fast robust matrix completion algorithm with in-face extended Frank-Wolfe optimization is applied on a cohort of healthy subjects and a target patient, to model the patient's unfilled vessels and the estimated full vasculature as sparse and low-rank components, respectively. The collateral score is computed as the ratio of the unfilled vessels to the full vasculature, mimicking existing clinical protocols.

RESULTS

ACCESS was tested with 46 stroke patients and obtained an overall accuracy of 84.78%. The optimal threshold selection was evaluated using a receiver operating characteristics curve with the leave-one-out approach, and a mean area under the curve of 85.39% was obtained.

CONCLUSION

ACCESS automates collateral scoring to mitigate the shortcomings of the standard clinical practice. It is a robust approach, which resembles how radiologists score clinical scans, and can be used to help radiologists in clinical decisions of stroke treatment.

Neuroanatomy of the middle cerebral artery: implications for thrombectomy

Our perspective on anatomy frequently depends on how this anatomy is utilized in clinical practice, and by which methods knowledge is acquired. The thrombectomy revolution, of which the middle cerebral artery (MCA) is the most common target, is an example of a clinical paradigm shift with a unique perspective on cerebrovascular anatomy. This article reviews important features of MCA anatomy in the context of thrombectomy. Recognizing that variation, frequently explained by evolutionary concepts, is the rule when it comes to branching pattern, vessel morphology, territory, or collateral potential is key to successful thrombectomy strategy.

From "Time is Brain" to "Imaging is Brain": A Paradigm Shift in the Management of Acute Ischemic Stroke

Arterial recanalization to restore the blood supply and limit the brain damage is the primary goal in the management of acute ischemic stroke (AIS). Since the publication of pivotal randomized clinical trials in 2015, endovascular thrombectomy has become part of the standard of care in selected cases of AIS from large-vessel occlusions up to 6 hours after the onset of symptoms. However, the association between endovascular reperfusion and improved functional outcome is not strictly time dependent. Rather than on rigid time windows, candidates should be selected based on vascular and physiologic information. This approach places imaging data at the center of treatment decisions. Advances in imaging-based management of AIS provide crucial information about vessel occlusion, infarct core, ischemic penumbra, and degree of collaterals. This information is invaluable in identifying patients who are likely to benefit from reperfusion therapies and excluding those who are unlikely to benefit or are at risk of adverse effects. The approach to reperfusion therapies continues to evolve, and imaging is acquiring a greater role in the diagnostic work-up and treatment decisions as shown in recent clinical trials with extended time window. The 2018 American Heart Association/American Stroke Association guidelines reflect a paradigm shift in the management of AIS from "Time is Brain" to "Imaging is Brain." This review discusses the essential role of multimodal imaging developing from recent trials on therapy for AIS.

Predictors of malignant brain edema after mechanical thrombectomy for acute ischemic stroke

BACKGROUND

Malignant brain edema (MBE) is a devastating complication in ischemic stroke. Data on MBE in patients who have had mechanical thrombectomy (MT) are relatively scarce.

OBJECTIVE

To investigate the incidence, predictors, and clinical outcomes of MBE in patients after MT.

METHODS

We included 130 consecutive patients after MT caused by anterior circulation large vessel occlusion stroke, treated with MT. MBE was defined as a midline shift of ≥5 mm on the follow-up imaging within 72 hours after MT. Characteristics of patients at admission and details of treatment were collected. The 90-day modified Rankin scale score was used as a measure of functional outcomes.

RESULTS

Of the 130 patients (age, 68.6±10.9 years; male, 50%), 35 (26.9%) patients developed MBE. The patients with MBE had a lower rate of functional independence (OR=7.831; 95% CI 1.731 to 35.427; p=0.008) and significantly higher mortality at 90 days (OR=7.958; 95% CI 2.274 to 27.848; p=0.001) than patients without MBE. In 104 (80%) patients with successful recanalization (modified Thrombolysis in Cerebral Infarction score of 2b-3), 24 (23.1%) patients exhibited MBE. After adjustment for confounding, ICA occlusion (OR=3.746; 95% CI 1.169 to 12.006; p=0.026) and worse collateral score (grade 1 vs grade 0: OR=0.727; 95% CI 0.192 to 2.753; p=0.638; grade 2 vs grade 0: OR=0.130; 95% CI 0.021 to 0.819; p=0.030) were significantly associated with the development of MBE, despite successful recanalization.

CONCLUSIONS

MBE after MT is not uncommon and was related to poor functional outcomes. Localization of a vessel occlusion and collateral status may play a role in the development of MBE.