Proper Indication of Decompressive Craniectomy for the Patients with Massive Brain Edema after Intra-arterial Thrombectomy

OBJECTIVE

Numerous studies have indicated that early decompressive craniectomy (DC) for patients with major infarction can be life-saving and enhance neurological outcomes. However, most of these studies were conducted by neurologists before the advent of intra-arterial thrombectomy (IA-Tx). This study aims to determine whether neurological status significantly impacts the final clinical outcome of patients who underwent DC following IA-Tx in major infarction.

METHODS

This analysis included 67 patients with major anterior circulation major infarction who underwent DC after IA-Tx, with or without intravenous tissue plasminogen activator. We retrospectively reviewed the medical records, radiological findings, and compared the neurological outcomes based on the "surgical time window" and neurological status at the time of surgery.

RESULTS

For patients treated with DC following IA-Tx, a Glasgow coma scale (GCS) score of 7 was the lowest score correlated with a favorable outcome (p=0.013). Favorable outcomes were significantly associated with successful recanalization after IA-Tx (p=0.001) and perfusion/diffusion (P/D)-mismatch evident on magnetic resonance imaging performed immediately prior to IA-Tx (p=0.007). However, the surgical time window (within 36 hours, p=0.389; within 48 hours, p=0.283) did not correlate with neurological outcomes.

CONCLUSION

To date, early DC surgery after major infarction is crucial for patient outcomes. However, this study suggests that the indication for DC following IA-Tx should include neurological status (GCS ≤7), as some patients treated with early DC without considering the neurological status may undergo unnecessary surgery. Recanalization of the occluded vessel and P/D-mismatch are important for long-term neurological outcomes.

Automatic triaging of acute ischemic stroke patients for reperfusion therapies using Artificial Intelligence methods and multiple MRI features: A review

BACKGROUND

The selection of appropriate treatments for Acute Ischemic Stroke (AIS), including Intravenous (IV) tissue plasminogen activator (tPA) and Mechanical thrombectomy, is a critical aspect of clinical decision-making. Timely treatment is essential, with recommended administration of therapies within 4.5 h of symptom onset. However, patients with unknown Time Since Stroke (TSS), are often excluded from thrombolysis, even if the stroke onset exceeds 6 h. Current clinical guidelines propose using multimodal Magnetic Resonance Imaging (MRI) to assess various mismatches.

METHODS

The review explores the significance of automatic methods based on Artificial Intelligence (AI) algorithms that utilize multiple MRI features to identify patients who are most likely to benefit from acute reperfusion therapies. These AI methods include TSS classification and patient selection for therapies in the late time window (>6 h) using MRI images to provide detailed stroke information.

RESULTS

The review discusses the challenges and limitations in the existing mismatch methods, which may lead to missed opportunities for reperfusion therapy. To address these limitations, AI approaches have been developed to enhance accuracy and support clinical decision-making. These AI methods have shown promising results, outperforming traditional mismatch assessments and providing improved sensitivity and specificity in identifying patients eligible for reperfusion therapies.

DISCUSSION

In summary, the integration of AI algorithms utilizing multiple MRI features has the potential to enhance accuracy, improve patient outcomes, and positively influence the decision-making process in AIS. However, ongoing research and collaboration among clinicians, researchers, and technologists are vital to realize the full potential of AI in optimizing stroke management.

Theta Frequency Electromagnetic Stimulation Enhances Functional Recovery After Stroke

Extremely low-frequency, low-intensity electromagnetic field (ELF-EMF) therapy is a non-invasive brain stimulation method that can modulate neuroprotection and neuroplasticity. ELF-EMF was recently shown to enhance recovery in human stroke in a small pilot clinical trial (NCT04039178). ELF-EMFs encompass a wide range of frequencies, typically ranging from 1 to 100 Hz, and their effects can vary depending on the specific frequency employed. However, whether and to what extent the effectiveness of ELF-EMFs depends on the frequency remains unclear. In the present study, we aimed to assess the efficacy of different frequency-intensity protocols of ELF-EMF in promoting functional recovery in a mouse cortical stroke model with treatment initiated 4 days after the stroke, employing a series of motor behavior tests. Our findings demonstrate that a theta-frequency ELF-EMF (5 Hz) effectively enhances functional recovery in a reach-to-grasp task, whereas neither gamma-frequency (40 Hz) nor combination frequency (5-16-40 Hz) ELF-EMFs induce a significant effect. Importantly, our histological analysis reveals that none of the ELF-EMF protocols employed in our study affect infarct volume, inflammatory, or glial activation, suggesting that the observed beneficial effects may be mediated through non-neuroprotective mechanisms. Our data indicate that ELF-EMFs have an influence on functional recovery after stroke, and this effect is contingent upon the specific frequency used. These findings underscore the critical importance of optimizing the protocol parameters to maximize the beneficial effects of ELF-EMF. Further research is warranted to elucidate the underlying mechanisms and refine the protocol parameters for optimal therapeutic outcomes in stroke rehabilitation.

Quantitative assessment of collateral time on perfusion computed tomography in acute ischemic stroke patients

Background and aim

Good collateral circulation is recognized to maintain perfusion and contribute to favorable clinical outcomes in acute ischemic stroke. This study aimed to derive and validate an optimal collateral time measurement on perfusion computed tomography imaging for patients with acute ischemic stroke.

Methods

This study included 106 acute ischemic stroke patients with complete large vessel occlusions. In deriving cohort of 23 patients, the parasagittal region of the ischemic hemisphere was divided into six pial arterial zones according to pial branches of the middle cerebral artery. Within the 85 arterial zones with collateral vessels, the receiver operating characteristic analysis was performed to derive the optimal collateral time threshold for fast collateral flow on perfusion computed tomography. The reference for fast collateral flow was the peak contrast delay on the collateral vessels within each ischemic arterial zone compared to its contralateral normal arterial zone on dynamic computed tomography angiography. The optimal perfusion collateral time threshold was then tested in predicting poor clinical outcomes (modified Rankin score of 5-6) and final infarct volume in the validation cohort of 83 patients.

Results

For the derivation cohort of 85 arterial zones, the optimal collateral time threshold for fast collateral flow on perfusion computed tomography was a delay time of 4.04 s [area under the curve = 0.78 (0.67, 0.89), sensitivity = 73%, and specificity = 77%]. Therefore, the delay time of 4 s was used to define the perfusion collateral time. In the validation cohort, the perfusion collateral time showed a slightly higher predicting power than dynamic computed tomography angiography collateral time in poor clinical outcomes (area under the curve = 0.72 vs. 0.67; P < 0.001). Compared to dynamic computed tomography angiography collateral time, the perfusion collateral time also had better performance in predicting final infarct volume (R-squared values = 0.55 vs. 0.23; P < 0.001).

Conclusion

Our results indicate that perfusion computed tomography can accurately quantify the collateral time after acute ischemic stroke.

Magnetic resonance imaging of hypoxia in acute stroke compared with fluorine-18 fluoromisonidazole-positron emission tomography: A cross-validation study?

Acute ischemic stroke results in an ischemic core surrounded by a tissue at risk, named the penumbra, which is potentially salvageable. One way to differentiate the tissues is to measure the hypoxia status. The purpose of the current study is to correlate the abnormal brain tissue volume derived from magnetic resonance-based imaging of brain oxygen saturation (S_t O₂ -MRI) to the fluorine-18 fluoromisonidazole ([¹⁸ F]FMISO) positron emission tomography (PET) volume for hypoxia imaging validation, and to analyze the ability of S_t O₂ -MRI to depict the different hypoxic tissue types in the acute phase of stroke. In a pertinent model of stroke in the rat, the volume of tissue with decreased S_t O₂ -MRI signal and that with increased uptake of [¹⁸ F]FMISO were equivalent and correlated (r = 0.706; p = 0.015). The values of S_t O₂ in the tissue at risk were significantly greater than those quantified in the core of the lesion, and were less than those for healthy tissue (52.3% ± 2.0%; 43.3% ± 1.9%, and 67.9 ± 1.4%, respectively). A threshold value for S_t O₂ of ≈60% as the cut-off for the identification of the tissue at risk was calculated. Tissue volumes with reduced S_t O₂ -MRI correlated with the final lesion (r = 0.964, p < 0.0001). The findings show that the S_t O₂ -MRI approach is sensitive for the detection of hypoxia and for the prediction of the final lesion after stroke. Once validated in acute clinical settings, this approach might be used to enhance the stratification of patients for potential therapeutic interventions.

Recanalization Rate and Clinical Outcomes of Intravenous Tissue Plasminogen Activator Administration for Large Vessel Occlusion Stroke Patients

OBJECTIVE

Stroke caused from large vessel occlusion (LVO) has emerged as the most common stroke subtype worldwide. Intravenous tissue plasminogen activator administration (IV-tPA) and additional intraarterial thrombectomy (IA-Tx) is regarded as standard treatment. In this study, the authors try to find the early recanalization rate of IV-tPA in LVO stroke patients.

METHODS

Total 300 patients undertook IA-Tx with confirmed anterior circulation LVO, were analyzed retrospectively. Brain computed tomography angiography (CTA) was the initial imaging study and acute stroke magnetic resonance angiography (MRA) followed after finished IV-tPA. Early recanalization rate was evaluated by acute stroke MRA within 2 hours after the IV-tPA. In 167 patients undertook IV-tPA only and 133 non-recanalized patients by IV-tPA, additional IA-Tx tried (IV-tPA + IA-Tx group). And 131 patients, non-recanalized by IV-tPA (IV-tPA group) additional IA-Tx recommend and tried according to the patient condition and compliance.

RESULTS

Early recanalization rate of LVO after IV-tPA was 12.0% (36/300). In recanalized patients, favorable outcome (modified Rankin Scale, 0-2) was 69.4% (25/36) while it was 32.1% (42/131, p<0.001) in non-recanalized patients. Among 133 patients, nonrecanalized after intravenous recombinant tissue plasminogen activator and undertook additional IA-Tx, the clinical outcome was better than not undertaken additional IA-Tx (favorable outcome was 42.9% vs. 32.1%, p=0.046). Analysis according to the perfusion/diffusion (P/D)-mismatching or not, in patient with IV-tPA with IA-Tx (133 patients), favorable outcome was higher in P/ D-mismatching patient (52/104; 50.0%) than P/D-matching patients (5/29; 17.2%; p=0.001). Which treatment tired, P/D-mismatching was favored in clinical outcome (iv-tPA only, p=0.008 and IV-tPA with IA-Tx, p=0.001).

CONCLUSION

The P/D-mismatching influences on the recanalization and clinical outcomes of IV-tPA and IA-Tx. The authors would like to propose that we had better prepare IA-Tx when LVO is diagnosed on initial diagnostic imaging. Furthermore, if the patient shows P/D-mismatching on MRA after IV-tPA, additional IA-Tx improves treatment results and lessen the futile recanalization.

Pre-stroke Physical Activity and Cerebral Collateral Circulation in Ischemic Stroke: A Potential Therapeutic Relationship?

Favorable cerebral collateral circulation contributes to hindering penumbral tissue from progressing to infarction and is associated with positive clinical outcomes after stroke. Given its clinical importance, improving cerebral collateral circulation is considered a therapeutic target to reduce burden after stroke. We provide a hypothesis-generating discussion on the potential association between pre-stroke physical activity and cerebral collateral circulation in ischemic stroke. The recruitment of cerebral collaterals in acute ischemic stroke may depend on anatomical variations, capacity of collateral vessels to vasodilate, and individual risk factors. Physical activity is associated with improved cerebral endothelial and vascular function related to vasodilation and angiogenic adaptations, and risk reduction in individual risk factors. More research is needed to understand association between cerebral collateral circulation and physical activity. A presentation of different methodological considerations for measuring cerebral collateral circulation and pre-stroke physical activity in the context of acute ischemic stroke is included. Opportunities for future research into cerebral collateral circulation, physical activity, and stroke recovery is presented.

A New NF-κB Inhibitor, MEDS-23, Reduces the Severity of Adverse Post-Ischemic Stroke Outcomes in Rats

Aim: Nuclear factor kappa B (NF-κB) is known to play an important role in the inflammatory process which takes place after ischemic stroke. The major objective of the present study was to examine the effects of MEDS-23, a potent inhibitor of NF-κB, on clinical outcomes and brain inflammatory markers in post-ischemic stroke rats. Main methods: Initially, a Toxicity Experiment was performed to determine the appropriate dose of MEDS-23 for use in animals, as MEDS-23 was analyzed in vivo for the first time. We used the middle cerebral artery occlusion (MCAO) model for inducing ischemic stroke in rats. The effects of MEDS-23 (at 10 mg/kg, ip) on post-stroke outcomes (brain inflammation, fever, neurological deficits, mortality, and depression- and anxiety-like behaviours) was tested in several efficacy experiments. Key findings: MEDS-23 was found to be safe and significantly reduced the severity of some adverse post-stroke outcomes such as fever and neurological deficits. Moreover, MEDS-23 significantly decreased prostaglandin E2 levels in the hypothalamus and hippocampus of post-stroke rats, but did not prominently alter the levels of interleukin-6 and tumor necrosis factor-α. Significance: These results suggest that NF-κB inhibition is a potential therapeutic strategy for the treatment of ischemic stroke.

Multimodal CT Imaging Characteristics in Predicting Prognosis of Wake-Up Stroke

Background: Multimodal CT imaging can evaluate cerebral hemodynamics and stroke etiology, playing an important role in predicting prognosis. This study aimed to summarize the comprehensive image characteristics of wake-up stroke (WUS), and to explore its value in prognostication.

Methods: WUS patients with anterior circulation large vessel occlusion were recruited into this prospective study. According to the 90-day modified Rankin Scale (mRS), all patients were divided into good outcome (mRS 0–2) or bad (mRS 3–6). Baseline clinical information, multimodal CT imaging characteristics including NECT ASPECTS, clot burden score (CBS), collateral score, volume of penumbra and ischemic core on perfusion were compared. Multivariate logistic regression analysis was further used to analyze predictive factors for good prognosis. Area under curve (AUC) was calculated from the receiver operating characteristic (ROC) curve to assess prognostic value.

Results: Forty WUS were analyzed in this study, with 20 (50%) achieving good outcome. Upon univariable analysis, the good outcome group demonstrated higher ASPECTS, higher CBS, higher rate of good collateral filling and lower penumbra volume when compared with the poor outcome group. Upon logistic regression analysis, poor outcome significantly correlated with penumbra volume (OR: 1.023, 95% CI = 1.003–1.043) and collateral score (OR: 0.140, 95% CI = 0.030–0.664). AUC was 0.715 for penumbra volume (95% CI, 0.550–0.846) and 0.825 for good collaterals (95% CI, 0.672–0.927) in predicting outcome.

Conclusions:Penumbra volume and collateral score are the most relevant baseline imaging characters in predicting outcome of WUS patients. These imaging characteristics might be instructive to treatment selection. As the small sample size of current study, further studies with larger sample size are needed to confirm these observations.

Four Decades of Ischemic Penumbra and Its Implication for Ischemic Stroke

The ischemic penumbra defined four decades ago has been the main battleground of ischemic stroke. The evolving ischemic penumbra concept has been providing insight for the development of vascular and cellular approaches as well as diagnostic tools for the treatment of ischemic stroke. rt-PA thrombolytic therapy to prevent the transition of ischemic penumbra to core has been approved for acute ischemic stroke within 3 h and was later recommended to extend to 4.5 h after symptom onset. Mechanical thrombectomy was introduced for the treatment of acute ischemic stroke with a therapeutic window of up to 24 h after stroke onset. Multiple modalities brain imaging techniques have been developed that provide guidance to define ischemic penumbra for reperfusion therapy in clinical practice. Cellular and molecular dissection of ischemic penumbra has been providing targets for the development of neuroprotective therapy for ischemic stroke. However, the dynamic nature of ischemic penumbra implicates that infarct core eventually expands into penumbra over time without reperfusion, dictating relative short therapeutic windows and limiting the impact of current reperfusion intervention. Entering the 5^th decade since the introduction, ischemic penumbra remains the main focus of ischemic stroke research and clinical practice. In this review, we summarized the evolving ischemic penumbra concept and its implication in the development of vascular and cellular interventions as well as diagnostic tools for acute ischemic stroke. In addition, we discussed future perspectives on expansion of the campaign beyond ischemic penumbra to develop treatment for ischemic stroke.

Advances in imaging acute ischemic stroke: evaluation before thrombectomy

Recent advances in neuroimaging have demonstrated significant assessment benefits and appropriate triage of patients based on specific clinical and radiological features in the acute stroke setting. Endovascular thrombectomy is arguably the most important aspect of acute stroke management with an extended time window. Imaging-based physiological information may potentially shift the treatment paradigm from a rigid time-based model to a more flexible and individualized, tissue-based approach, increasing the proportion of patients amenable to treatment. Various imaging modalities are routinely used in the diagnosis and management of acute ischemic stroke, including multimodal computed tomography (CT) and magnetic resonance imaging (MRI). Therefore, these imaging methods should provide information beyond the presence or absence of intracranial hemorrhage as well as the presence and extent of the ischemic core, collateral circulation and penumbra in patients with neurological symptoms. Target mismatch may optimize selection of patients with late or unknown symptom onset who would potentially be eligible for revascularization therapy. The purpose of this study was to provide a comprehensive review of the current evidence about efficacy and theoretical basis of present imaging modalities, and explores future directions for imaging in the management of acute ischemic stroke.

Pertussis Toxin Ameliorates Microglial Activation Associated With Ischemic Stroke

Objective: To investigate the effect and the underlying mechanism of Pertussis toxin (PTX) on microglia in the setting of cerebral ischemia. Methods: We tested the effect of PTX 400 ng/days on middle cerebral artery occlusion stroke model by evaluating the neurologic function, infarct size, microglial distribution, and activation. In parallel, we also tested the effect of PTX on primary cultured microglia by evaluating microglial proliferation, activation, cytokine release, and CX3CR1 expression. Results: PTX reduced the poststroke infarct size, improved the neurologic function as evaluated by Longa score, and reduced microglial aggregation and activation in the infarcted area. Further, PTX significantly decreased lipopolysaccharide-stimulated microglial proliferation, the release of interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α), and the expression of CX3CR1. Interpretation: PTX treatment in stroke reduced microglial accumulation and activation in the infarct zone, resulting in a better functional outcome. The benefits of PTX treatment may be attributed to the reduced production of proinflammatory cytokine such as IL-1β and TNF-α and reduced expression of chemokine CX3CR1.

Cerebral haemodynamics with head position changes post-ischaemic stroke: A systematic review and meta-analysis

The effects of upright postures on the cerebral circulation early post-ischaemic stroke are not fully understood. We conducted a systematic review and meta-analysis to investigate the effects of head positioning on cerebral haemodynamics assessed by imaging methods post-ischaemic stroke. Of the 21 studies included (n = 529), 15 used transcranial Doppler. Others used near-infrared, diffuse correlation spectroscopy and nuclear medicine modalities. Most tested head positions between 0° and 45°. Seventeen studies reported changes in CBF parameters (increase at lying-flat or decrease at more upright) in the ischaemic hemisphere with position change. However, great variability was found and risk of bias was high in many studies. Pooled data of two studies ≤24 h (n = 28) showed a mean increase in cerebral blood flow (CBF) velocity of 8.5 cm/s in the ischaemic middle cerebral artery (95%CI,-2.2-19.3) from 30° to 0°. The increase found ≤48 h (n = 50) was of 2.3 cm/s (95%CI,-4.6-9.2), while ≤7 days (n = 38) was of 8.4 cm/s (95%CI, 1.8-15). Few very early studies (≤2 days) tested head positions greater than 30° and were unable to provide information about the response of acute stroke patients to upright postures (sitting, standing). These postures are part of current clinical practice and knowledge on their effects on cerebral haemodynamics is required.

Intravenous thrombolysis in a peripheral primary stroke center without advanced imaging, a retrospective 2016-2017 cohort study

PURPOSE OF THE STUDY

The hyperacute care of ischemic stroke has evolved markedly. It is unclear to which level stroke centre patients should primarily be taken so information of intravenous thrombolysis (IVT) outcomes in smaller centres are needed.

METHODS

All IVT episodes in North Karelia Central hospital in 2016-2017 were analysed retrospectively using hospital registries and individual medical records.

RESULTS

IVT had been given to 75 patients (47% women) whose median age was 74 years [IQR 64, 81; no gender difference (p = 0.70)]. Median NIHSS on admission was 6 (IQR 4, 10) and onset-to-treatment time (OTT) 125 min (95% CI 112-138 min). Two intracranial bleeding complications were observed. Clinical status improved following IVT and 53.4% were independent at six months (85% were independent before the stroke). In a multivariate analysis the NIHSS score was the only predictor (B = 0.12, R²=0.34, p = 0.0001) of modified Rankin Scale (mRS). Large-vessel occlusion (LVO) was identified in 27% (35% women). Their median mRS was 2.0 (25% had died). Endovascular thrombectomy had followed IVT in 30% of the LVO-patients.

CONCLUSIONS

IVT results were generally in this peripheral PSC-level hospital without advanced imaging capabilities, but LVO outcomes need improvement. A mothership strategy should be evaluated.

Prediction contribution of the cranial collateral circulation to the clinical and radiological outcome of ischemic stroke

BACKGROUND AND AIM

The extent of penumbra tissue and outcome in stroke patients depend on the collateral cranial vasculature. To provide optimal individualized care for stroke patients in the emergency room setting we investigated the predictive capability of a stringent evaluation of the collateral vessels in ischemic stroke on clinical outcome and infarct size.

METHODS

We retrospectively studied uniform clinical and radiological data of 686 consecutive patients admitted to the emergency department with suspected acute ischemic stroke. Cranial collateral vasculature status was graded using the initial CT-angiography. Outcome was measured by mRS, NIHSS and final infarct size at hospital discharge. All data were used to build a linear regression model to predict the patients´ outcome.

RESULTS

Univariate and multivariate analyses showed significant effects of the whole brain collateral vessel score on all outcome variables. Atherosclerosis and piale collateral status were associated with the final infarct volume (FIV). Atherosclerosis and age were associated with the NIHSS at discharge. The presence of atherosclerosis, glucose level on admission and age were associated with the mRS at discharge. The multivariate models were able to predict 29% of the variance of the mRS at discharge, 24% of the variance in FIV and 17% of the variance of the NIHSS at discharge. The whole brain collateral status and the presence of atherosclerosis were the most relevant predictors for the clinical and radiological outcome.

CONCLUSION

The whole brain collateral vasculature status is clearly associated with clinical and radiological outcome but in a multivariate model seems not sufficiently predictive for FIV, mRS and NIHSS outcome at discharge in non-preselected patients admitted to the emergency department with ischemic stroke.

Penumbra-based radiomics signature as prognostic biomarkers for thrombolysis of acute ischemic stroke patients: a multicenter cohort study

BACKGROUND AND PURPOSE

This study aimed at developing a radiomics signature (R score) as prognostic biomarkers based on penumbra quantification and to validate the radiomics nomogram to predict the clinical outcomes for thrombolysis for acute ischemic stroke (AIS) patients.

METHODS

In total, 168 patients collected from seven centers were retrospectively included. A score of mismatch was defined as MIS. Based on a short-term clinical label, 456 radiomics features were evaluated with feature selection methods. R score was constructed with the selected features. To compare the predictive capabilities of the clinical factors, MIS, and R score, three nomograms were developed and evaluated, according to the short-term clinical assessment on day 7. Finally, the radiomics nomogram was validated by predicting the 3-month clinical outcomes of AIS patients, in an external cohort.

RESULTS

R scores were found to be significantly higher in patients with favorable clinical outcomes in both training and validation datasets. The predictive value of the radiomics nomogram estimating favorable clinical outcomes was modest, with a concordance index (C-index) of 0.695 [95% confidence interval (CI) 0.667-0.723) in an external validation dataset. In addition, the area under curve (AUC) of the radiomics nomogram predicting favorable clinical outcome reached 0.886 (95% CI 0.809-0.963) on day 7 and 0.777 (95% CI 0.666-0.888) at 3 months.

CONCLUSIONS

The radiomics signature is an independent biomarker for estimating the clinical outcomes in AIS patients. By improving the individualized prediction of the clinical outcome for AIS patients 3 months after onset, the radiomics nomogram adds more value to the current clinical decision-making process.

Small Vessels Are a Big Problem in Neurodegeneration and Neuroprotection

The cerebral microcirculation holds a critical position to match the high metabolic demand by neuronal activity. Functionally, microcirculation is virtually inseparable from other nervous system cells under both physiological and pathological conditions. For successful bench-to-bedside translation of neuroprotection research, the role of microcirculation in acute and chronic neurodegenerative disorders appears to be under-recognized, which may have contributed to clinical trial failures with some neuroprotectants. Increasing data over the last decade suggest that microcirculatory impairments such as endothelial or pericyte dysfunction, morphological irregularities in capillaries or frequent dynamic stalls in blood cell flux resulting in excessive heterogeneity in capillary transit may significantly compromise tissue oxygen availability. We now know that ischemia-induced persistent abnormalities in capillary flow negatively impact restoration of reperfusion after recanalization of occluded cerebral arteries. Similarly, microcirculatory impairments can accompany or even precede neural loss in animal models of several neurodegenerative disorders including Alzheimer's disease. Macrovessels are relatively easy to evaluate with radiological or experimental imaging methods but they cannot faithfully reflect the downstream microcirculatory disturbances, which may be quite heterogeneous across the tissue at microscopic scale and/or happen fast and transiently. The complexity and size of the elements of microcirculation, therefore, require utilization of cutting-edge imaging techniques with high spatiotemporal resolution as well as multidisciplinary team effort to disclose microvascular-neurodegenerative connection and to test treatment approaches to advance the field. Developments in two photon microscopy, ultrafast ultrasound, and optical coherence tomography provide valuable experimental tools to reveal those microscopic events with high resolution. Here, we review the up-to-date advances in understanding of the primary microcirculatory abnormalities that can result in neurodegenerative processes and the combined neurovascular protection approaches that can prevent acute as well as chronic neurodegeneration.

Collaterals are a major determinant of the core but not the penumbra volume in acute ischemic stroke

PURPOSE

Determinants of early loss of ischemic tissue (core) or its prolonged survival (penumbra) in acute ischemic stroke (AIS) are poorly understood. We aimed to identify radiological associations of core and penumbra volumes on CT perfusion (CTP) in a large cohort of AIS.

METHODS

In the ASTRAL registry (2003-2016), we identified consecutive AIS patients with proximal middle cerebral artery (MCA) occlusion. We calculated core and penumbra volumes using established thresholds and the mismatch ratio (MR). We graded collaterals into three categories on CT-angiography. We used clot burden score (CBS) to quantify the clot length. We related CTP volumes to radiological variables in multivariate regression analyses, adjusted for time from stroke onset to first imaging.

RESULTS

The median age of the 415 included patients was 69 years (IQR = 21) and 49% were female. Median admission NIHSS was 16 (11) and median delay to imaging 2.2 h (1.9). Lower core volumes were associated with higher ASPECTS (hazard ratio = 1.08), absence of hyperdense MCA sign (HR = 0.70), higher CBS (i.e., smaller clot, HR = 1.10), and better collaterals (HR = 1.95). Higher penumbra volumes were related to lower CBS (i.e., longer clot, HR = 1.08) and proximal intracranial occlusion (HR = 1.47), but not to collaterals. Higher MR was found in absence of hyperdense MCA sign (HR = 1.28), absence of distal intracranial occlusion (HR = 1.39), and with better collaterals (HR = 0.52).

CONCLUSIONS

In AIS, better collaterals were associated with lower core volumes, but not with higher penumbra volumes. This suggests a major role of collaterals in early tissue loss and their limited significance as marker of salvageable tissue.

Extension of therapeutic window in ischemic stroke by selective mismatch imaging

The concept of the ischemic penumbra was formulated on the basis of animal experiments showing functional impairment and electrophysiologic disturbances with decreasing flow to the brain below defined values (the threshold for function) and irreversible tissue damage with blood supply further decreased (the threshold for infarction). The perfusion range between these thresholds was termed the “penumbra,” and restitution of flow above the functional threshold was able to reverse the deficits without permanent damage. In further experiments, the dependency of the development of irreversible lesions on the interaction of the severity and the duration of critically reduced blood flow was established, proving that the lower the flow, the shorter the time for efficient reperfusion. As a consequence, infarction develops from the core of ischemia to the areas of less severe hypoperfusion. The translation of this experimental concept as the basis for the efficient treatment of stroke requires methods by which regional flow and energy metabolism can be repeatedly investigated to demonstrate penumbra tissue, which can benefit from therapeutic interventions. Positron emission tomography allows the quantification of regional cerebral blood flow, the regional oxygen extraction fraction, and the regional metabolic rate for oxygen. With these variables, clear definitions of irreversible tissue damage and of critically hypoperfused but potentially salvageable tissue (i.e. the penumbra) in stroke patients can be achieved. However, positron emission tomography is a research tool, and its complex logistics limit clinical routine applications. Perfusion-weighted or diffusion-weighted magnetic resonance imaging is a widely applicable clinical tool, and the “mismatch” between perfusion-weighted and diffusion-weighted abnormalities serves as an indicator of the penumbra. Also computed tomography angiography and computed tomography perfusion imaging can be used to detect areas suspicious of penumbra. The findings with both methods should be validated by positron emission tomography measurements. Several studies included the selection of patients for intravenous thrombolysis on the basis of a perfusion-weighted imaging–diffusion-weighted imaging mismatch or computed tomography perfusion studies. A meta-analysis of several mismatch-based thrombolysis studies of delayed treatment from the DIAS, DIAS-2, DEDAS, EPITHET, and DEFUSE trials revealed increased recanalization. However, this analysis did not confirm an improvement in clinical outcome with delayed thrombolysis. Randomized controlled trials that did enroll patients based on the presence of a target mismatch on multimodal imaging demonstrated a higher benefit of revascularization treatment by comparison with those who did not and demonstrated for the first time that revascularization treatment for occlusion of an internal carotid artery (ICA) or a proximal middle cerebral artery (MCA) was still beneficial from 6 to 24 h after onset among patients in whom the clinical examination and the multimodal brain imaging indicate a persistent penumbra. On this background, the yield of imaging for the selection of patients for a revascularization therapy will be discussed.

Imaging Diagnosis of Transient Ischemic Attack in Clinic and Traditional Chinese Medicine

Neuroimaging plays a pivotal role in Transient Ischemic Attack (TIA). Generally, clinicians focus on the specific changes in morphology and function, but the diagnosis of TIA often depends on imaging evidence. Whereas Traditional Chinese Medicine (TCM) is concerned with the performance of clinical symptoms, they began to use imaging methods to diagnose TIA. CT and MRI are the recommended modality to diagnose TIA and image ischemic lesions. In addition, Transcranial Doppler sonography (TCD) and Digital Subtraction Angiography (DSA) are two acceptable alternatives for diagnosing TIA patients. This article elaborates the update of imaging modalities in clinic and the development of imaging modalities in TCM. Besides, multiple joint imaging technologies also will be evaluated whether enhanced diagnostic yields availably.

Hyperacute changes in blood mRNA expression profiles of rats after middle cerebral artery occlusion: Towards a stroke time signature

Stroke evolution is a highly dynamic but variable disease which makes clinical decision making difficult. Biomarker discovery programs intended to aid clinical decision making have however largely ignored the rapidity of stroke evolution. We have used gene array technology to determine blood mRNA expression changes over the first day after stroke in rats. Blood samples were collected from 8 male spontaneously hypertensive rats at 0, 1, 2, 3, 6 and 24h post stroke induction by middle cerebral artery occlusion. RNA was extracted from whole blood stabilized in PAXgene tubes and mRNA expression was detected by oligonucleotide Affymetrix microarray. Using a pairwise comparison model, 1932 genes were identified to vary significantly over time (p≤0.5x10^-7) within 24h after stroke. Some of the top20 most changed genes are already known to be relevant to the ischemic stroke physiopathology (e.g. Il-1R, Nos2, Prok2). Cluster analysis showed multiple stereotyped and time dependent profiles of gene expression. Direction and rate of change of expression for some profiles varied dramatically during these 24h. Profiles with potential clinical utility including hyper acute or acute transient upregulation (with expression peaking from 2 to 6h after stroke and normalisation by 24h) were identified. We found that blood gene expression varies rapidly and stereotypically after stroke in rats. Previous researchers have often missed the optimum time for biomarker measurement. Temporally overlapping profiles have the potential to provide a biological “stroke clock” able to tell the clinician how far an individual stroke has evolved.

Development and validation of a penumbra-based predictive model for thrombolysis outcome in acute ischemic stroke patients

The use of thrombolysis in acute ischemic stroke is restricted to a small proportion of patients because of the rigid 4·5-h window. With advanced imaging-based patient selection strategy, rescuing penumbra is critical to improving clinical outcomes. In this study, we included 155 acute ischemic stroke patients (84 patients in training dataset, age from 43 to 80, 59 males; 71 patients in validation dataset, age from 36 to 80, 45 males) who underwent MR scan within the first 9-h after onset, from 7 independent centers. Based on the mismatch concept, penumbra and core area were identified and quantitatively analyzed. Moreover, predictive models were developed and validated to provide an approach for identifying patients who may benefit from thrombolytic therapy. Predictive models were constructed, and corresponding areas under the curve (AUC) were calculated to explore their performances in predicting clinical outcomes. Additionally, the models were validated using an independent dataset both on Day-7 and Day-90. Significant correlations were detected between the mismatch ratio and clinical assessments in both the training and validation datasets. Treatment option, baseline systolic blood pressure, National Institutes of Health Stroke Scale score, mismatch ratio, and three regional radiological parameters were selected as biomarkers in the combined model to predict clinical outcomes of acute ischemic stroke patients. With the external validation, this predictive model reached AUCs of 0·863 as short-term validation and 0·778 as long-term validation. This model has the potential to provide quantitative biomarkers that aid patient selection for thrombolysis either within or beyond the current time window.

Paradigm Shift to Neuroimmunomodulation for Translational Neuroprotection in Stroke

The treatment of acute ischemic stroke is still an unresolved clinical problem since the only approved therapeutic intervention relies on early blood flow restoration through pharmacological thrombolysis, mechanical thrombus removal, or a combination of both strategies. Due to their numerous complications and to the narrow time-window for the intervention, only a minority of stroke patients can actually benefit from revascularization procedures, highlighting the urgent need of identifying novel strategies to prevent the progression of an irreversible damage in the ischemic penumbra. During the past three decades, the attempts to target the pathways implicated in the ischemic cascade (e.g., excitotoxicity, calcium channels overactivation, reactive oxygen species (ROS) production) have failed in the clinical setting. Based on a better understanding of the pathobiological mechanisms and on a critical reappraisal of most failed trials, numerous findings from animal studies have demonstrated that targeting the immune system may represent a promising approach to achieve neuroprotection in stroke. In particular, given the dualistic role of distinct components of both the innate and adaptive arms of the immune system, a strategic intervention should be aimed at establishing the right equilibrium between inflammatory and reparative mechanisms, taking into consideration their spatio-temporal recruitment after the ischemic insult. Thus, the application of immunomodulatory drugs and their ability to ameliorate outcomes deserve validation in patients with acute ischemic stroke.

Discovery and Longitudinal Evaluation of Candidate Biomarkers for Ischaemic Stroke by Mass Spectrometry-Based Proteomics

Application of acute therapies such as thrombolysis for ischaemic stroke (IS) is constrained because of diagnostic uncertainty and the dynamic nature of stroke biology. To investigate changes in blood proteins after stroke and as a result of thrombolysis treatment we performed label-free quantitative proteomics on serum samples using high-resolution mass spectrometry and long high-performance liquid chromatography gradient (5 hours) combined with a 50-cm column to optimise the peptide separation. We identified (false discovery rate [FDR]: 1%) and quantified a total of 574 protein groups from a total of 92 samples from 30 patients. Ten patients were treated by thrombolysis as part of a randomised placebo-controlled trial and up to 5 samples were collected from each individual at different time points after stroke. We identified 26 proteins differently expressed by treatment group (FDR: 5%) and significant changes of expression over time for 23 proteins (FDR: 10%). Molecules such as fibrinogen and C-reactive protein showed expression profiles with a high-potential clinical utility in the acute stroke setting. Protein expression profiles vary acutely in the blood after stroke and have the potential to allow the construction of a stroke clock and to have an impact on IS treatment decision making.

Refining the ischemic penumbra with topography

It has been 40 years since the ischemic penumbra was first conceptualized through work on animal models. The topography of penumbra has been portrayed as an infarcted core surrounded by penumbral tissue and an extreme rim of oligemic tissue. This picture has been used in many review articles and textbooks before the advent of modern imaging. In this paper, we review our understanding of the topography of the ischemic penumbra from the initial experimental animal models to current developments with neuroimaging which have helped to further define the temporal and spatial evolution of the penumbra and refine our knowledge. The concept of the penumbra has been successfully applied in clinical trials of endovascular therapies with a time window as long as 24 h from onset. Further, there are reports of “good” outcome even in patients with a large ischemic core. This latter observation of good outcome despite having a large core requires an understanding of the topography of the penumbra and the function of the infarcted regions. It is proposed that future research in this area takes departure from a time-dependent approach to a more individualized tissue and location-based approach.

Magnetic Resonance Perfusion Imaging Provides a Significant Tool for the Identification of Cardioembolic Stroke

Despite advances in imaging techniques and detailed examinations to determine the etiology of a stroke, the cause still remains undetermined in about one fourth of all ischemic strokes. The aim of this prospective study was to determine whether perfusion magnetic resonance imaging (MRI) can differentiate cardioembolic stroke from large artery atherosclerosis (LAA). We recruited 17 cardioembolic stroke and 22 LAA stroke patients, who were classified according to the Trial of Org 10172 in Acute Stroke Treatment and underwent perfusion MRI within 24 hours after the onset of stroke. The patients with cardioembolic stroke had more severe initial stroke severity and larger volumes of initial and final infarct compared to those with LAA stroke. Receiver operating characteristic curve analysis showed that the ratio of time to maximum of the residual curve (T_max) volume for a 2-, 3-, 4- or 5-s lag over T_max volume for a 8s lag all had excellent area under the curve values (> 0.9) to predict cardioembolic stroke. After adjusting for initial National Institute of Health Stroke Scale scores, a threshold of 3.73 for (T_max > 4s volume)/(T_max > 8s volume) had the highest odds ratio to predict cardioembolic stroke (p=0.012; odds ratio: 58.5; 95% confident interval: 2.5-1391.1), with 87.5% sensitivity and 94.4% specificity. In conclusion, perfusion MRI could be a reliable tool to identify cardioembolic stroke with its lower collateral. This is important as it could be used to reveal the exact mechanism and provide supportive evidence to classify a stroke.

Is age a key factor contributing to the disparity between success of neuroprotective strategies in young animals and limited success in elderly stroke patients? Focus on protein homeostasis

Neuroprotection strategies to improve stroke outcome have been successful in the laboratory but not in clinical stroke trials, and thus have come under scrutiny by the medical community. Experimental stroke investigators are therefore under increased pressure to resolve this problem. Acute ischemic stroke represents a severe form of metabolic stress that activates many pathological processes and thereby impairs cellular functions. Traditionally, neuroprotection strategies were designed to improve stroke outcome by interfering with pathological processes triggered by ischemia. However, stroke outcome is also dependent on the brain's capacity to restore cellular functions impaired by ischemia, and this capacity declines with age. It is, therefore, conceivable that this age-dependent decline in the brain's self-healing capacity contributes to the disparity between the success of neuroprotective strategies in young animals, and limited success in elderly stroke patients. Here, prosurvival pathways that restore protein homeostasis impaired by ischemic stress should be considered, because their capacity decreases with increasing age, and maintenance of proteome fidelity is pivotal for cell survival. Boosting such prosurvival pathways pharmacologically to restore protein homeostasis and, thereby, cellular functions impaired by ischemic stress is expected to counterbalance the compromised self-healing capacity of aged brains and thereby help to improve stroke outcome.

Deep learning guided stroke management: a review of clinical applications

Stroke is a leading cause of long-term disability, and outcome is directly related to timely intervention. Not all patients benefit from rapid intervention, however. Thus a significant amount of attention has been paid to using neuroimaging to assess potential benefit by identifying areas of ischemia that have not yet experienced cellular death. The perfusion-diffusion mismatch, is used as a simple metric for potential benefit with timely intervention, yet penumbral patterns provide an inaccurate predictor of clinical outcome. Machine learning research in the form of deep learning (artificial intelligence) techniques using deep neural networks (DNNs) excel at working with complex inputs. The key areas where deep learning may be imminently applied to stroke management are image segmentation, automated featurization (radiomics), and multimodal prognostication. The application of convolutional neural networks, the family of DNN architectures designed to work with images, to stroke imaging data is a perfect match between a mature deep learning technique and a data type that is naturally suited to benefit from deep learning's strengths. These powerful tools have opened up exciting opportunities for data-driven stroke management for acute intervention and for guiding prognosis. Deep learning techniques are useful for the speed and power of results they can deliver and will become an increasingly standard tool in the modern stroke specialist's arsenal for delivering personalized medicine to patients with ischemic stroke.

False ischaemic penumbras in CT perfusion in patients with carotid artery stenosis and changes following angioplasty and stenting

INTRODUCTION

Carotid artery stenosis influences CT perfusion (CTP) studies, sometimes manifesting as a false ischaemic penumbra (FIP). This study aims to estimate the incidence of FIP in patients with carotid artery stenosis, establish their relationship with the degree of stenosis, and measure quantitative and qualitative changes in CTP after carotid angioplasty and stenting (CAS).

METHODS

Between October 2013 and June 2015, we prospectively selected 26 patients with carotid stenosis who underwent CAS, with CTP being performed 2-10 days before and after CAS.

RESULTS

Sixteen patients had unilateral stenosis (11 in the subgroup displaying < 90% stenosis and 5 in the subgroup with ≥ 90% stenosis) and 10 patients had bilateral stenosis. The incidence of FIP in patients with carotid artery stenosis was 38.5%. Risk of FIP increased in direct relation to degree of stenosis, with a relative risk of 11 in the subgroup with ≥ 90% stenosis with respect to the subgroup displaying < 90% stenosis (95% CI, 1.7-71.3; P=.0005). There were statistically significant changes in the parameters CBF, TTP, MTT, and Tmax CTP, which reverted after angioplasty. No significant changes were found in CBV.

CONCLUSIONS

Carotid artery stenosis involves changes in CTP parameters. Patients with ≥ 90% stenosis carry a high risk of FIP; CTP studies may therefore be misinterpreted in these cases. Changes in CTP parameters are reverted after CAS.

Optimizing Cardiac Out-Put to Increase Cerebral Penumbral Perfusion in Large Middle Cerebral Artery Ischemic Lesion-OPTIMAL Study

INTRODUCTION

In unsuccessful vessel recanalization, clinical outcome of acute stroke patients depends on early improvement of penumbral perfusion. So far, mean arterial blood pressure (MAP) is the target hemodynamic parameter. However, the correlations of MAP to cardiac output (CO) and cerebral perfusion are volume state dependent. In severe subarachnoid hemorrhage, optimizing CO leads to a reduction of delayed ischemic neurological deficits and improvement of clinical outcome. This study aims to investigate the effect of standard versus advanced cardiac monitoring with optimization of CO on the clinical outcome in patients with large ischemic stroke.

METHODS AND ANALYSIS

The OPTIMAL study is a prospective, multicenter, open, into two arms (1:1) randomized, controlled trial. Sample size estimate: sample sizes of 150 for each treatment group (300 in total) ensure an 80% power to detect a difference of 16% of a dichotomized level of functional clinical outcome at 3 months at a significance level of 0.05. Study outcomes: the primary endpoint is the functional outcome at 3 months. The secondary endpoints include functional outcome at 6 months follow-up, and complications related to hemodynamic monitoring and therapies.

DISCUSSION

The results of this trial will provide data on the safety and efficacy of advanced hemodynamic monitoring on clinical outcome.

ETHICS AND DISSEMINATION

The trial was approved by the leading ethics committee of Freiburg University, Germany (438/14, 2015) and the local ethics committees of the participating centers. The study is performed in accordance with the Declaration of Helsinki and the guidelines of Good Clinical Practice. It is registered in the German Clinical Trial register (DRKS; DRKS00007805). Dissemination will include submission to peer-reviewed professional journals and presentation at congresses. Hemodynamic monitoring may be altered in a specific stroke patient cohort if the study shows that advanced monitoring is safe and improves the functional outcome.

Total mismatch of diffusion-weighted imaging and susceptibility-weighted imaging in patients with acute cerebral ischemia

BACKGROUND AND PURPOSE

Multiple hypointense vessels (MHV) on susceptibility-weighted imaging (SWI) is associated with an increased oxygen demand in acute cerebral ischemia. Occasionally, some patients exhibit extensive MHV on SWI despite of negative diffusion-weighted imaging (DWI), which is a phenomenon called total mismatch DWI-SWI. We analyzed the clinical characteristics and imaging findings in patients with the total DWI-SWI mismatch.

MATERIALS AND METHODS

We selected patients with total DWI-SWI mismatch who underwent MRI within 12hours from onset. To evaluate the degree of collateral flow, we graded vessels on post-contrast time-of-flight MR angiography as 3 groups. Perfusion lesion volume was measured using threshold of>6seconds of mean transit time on perfusion-weighted imaging.

RESULTS

Total DWI-SWI mismatch was found in 10 (2.7%) out of 370 patients. Four out of 10 patients were excluded due to lack of data on perfusion studies. Hence 6 patients were finally selected in the study. Two patients with internal carotid artery dissection were treated with emergent stenting, one patient with intravenous thrombolysis and mechanical thrombectomy, and two patients with drug-induced hypertension. All of the enrolled patients exhibited extensive MHV on SWI and good collateral flows. The mean perfusion lesion volume was 72.6±15.3ml (range 0-325.0ml). Clinical outcome was favorable in all of the patients (mRS at 3 months, 0).

CONCLUSIONS

Our results demonstrate that total mismatch of DWI-SWI is associated with good collateral flow and may be a predictor of good response to treatment in patients with acute cerebral ischemia.

Wake-Up Stroke: Current Understanding

Patients with wake-up strokes account for approximately 1 in 5 individuals presenting with an acute ischemic stroke. However, they are commonly excluded from acute stroke treatment. This article reviews the current understanding of wake-up strokes. A comparison of wake-up and awake-onset strokes demonstrated that they are physiologically, clinically, and radiologically similar. Use of advanced CT and MRI techniques may help extend acute stroke treatment options to patients with wake-up stroke.

Monitoring Pressure Augmentation in Patients With Ischemic Penumbra Using Continuous Electroencephalogram: Three Cases and a Review of the Literature

BACKGROUND

Continuous electroencephalography (CEEG) is a sensitive, noninvasive surrogate monitor of cerebral blood flow (CBF). Changes in CBF can be seen as changes in the frequencies on the CEEG. This case series suggests that increase in CEEG frequencies may be used to detect improved CBF following pressure augmentation such as with treatment of vasospasm from subarachnoid hemorrhage (SAH) or acute thrombosis from ischemic stroke. The application of this observation to clinical decision-making has not been clearly defined and requires further study.

METHODS

Case series and imaging.

RESULTS

We present 3 patients with ischemic penumbras either from vasospasm from SAH or thrombosis from acute ischemic stroke. All patients were monitored on CEEG and found to have lateralized slowing. During pressure augmentation, the lateralized slowing improved in frequency, which corresponded with improvement in the patients' neurological examinations.

CONCLUSION

Continuous electroencephalography may be used as a noninvasive monitor to allow for individualization of pressure augmentation in cases of vasospasm from SAH or in cases of acute ischemic strokes. This customized approach may allow for less morbidity associated with pressure augmentation in patients who otherwise may have dysfunction of their intracerebral autoregulation.

Tmax Determined Using a Bayesian Estimation Deconvolution Algorithm Applied to Bolus Tracking Perfusion Imaging: A Digital Phantom Validation Study

PURPOSE

The Bayesian estimation algorithm improves the precision of bolus tracking perfusion imaging. However, this algorithm cannot directly calculate Tmax, the time scale widely used to identify ischemic penumbra, because Tmax is a non-physiological, artificial index that reflects the tracer arrival delay (TD) and other parameters. We calculated Tmax from the TD and mean transit time (MTT) obtained by the Bayesian algorithm and determined its accuracy in comparison with Tmax obtained by singular value decomposition (SVD) algorithms.

METHODS

The TD and MTT maps were generated by the Bayesian algorithm applied to digital phantoms with time-concentration curves that reflected a range of values for various perfusion metrics using a global arterial input function. Tmax was calculated from the TD and MTT using constants obtained by a linear least-squares fit to Tmax obtained from the two SVD algorithms that showed the best benchmarks in a previous study. Correlations between the Tmax values obtained by the Bayesian and SVD methods were examined.

RESULTS

The Bayesian algorithm yielded accurate TD and MTT values relative to the true values of the digital phantom. Tmax calculated from the TD and MTT values with the least-squares fit constants showed excellent correlation (Pearson's correlation coefficient = 0.99) and agreement (intraclass correlation coefficient = 0.99) with Tmax obtained from SVD algorithms.

CONCLUSIONS

Quantitative analyses of Tmax values calculated from Bayesian-estimation algorithm-derived TD and MTT from a digital phantom correlated and agreed well with Tmax values determined using SVD algorithms.

Optimized Flat-Detector CT in Stroke Imaging: Ready for First-Line Use?

Background: Using flat-detector CT (FD-CT) for stroke imaging has the advantage that both diagnostic imaging and endovascular therapy can be performed directly within the Angio Suite without any patient transfer and time delay. Thus, stroke management could be speeded up significantly, and patient outcome might be improved. But as precondition for using FD-CT as primary imaging modality, a reliable exclusion of intracranial hemorrhage (ICH) has to be possible. This study aimed to investigate whether optimized native FD-CT, using a newly implemented reconstruction algorithm, may reliably detect ICH in stroke patients. Additionally, the potential to identify ischemic changes was evaluated. Methods: Cranial FD-CT scans were obtained in 102 patients presenting with acute ischemic stroke (n = 32), ICH (n = 45) or transient ischemic attack (n = 25). All scans were reconstructed with a newly implemented half-scan cone-beam algorithm. Two experienced neuroradiologists, unaware of clinical findings, evaluated independently the FD-CTs screening for hemorrhage or ischemic signs. The findings were correlated to CT, and rater and inter-rater agreement was assessed. Results: FD-CT demonstrated high sensitivity (95-100%) and specificity (100%) in detecting intracerebral and intraventricular hemorrhage (IVH). Overall, interobserver agreement (κ = 0.92) was almost perfect and rater agreement to CT highly significant (r = 0.81). One infratentorial ICH and 10 or 11 of 22 subarachnoid hemorrhages (SAHs) were missed of whom 7 were perimesencephalic. The sensitivity for detecting acute ischemic signs was poor in blinded readings (0 or 25%, respectively). Conclusions: Optimized FD-CT, using a newly implemented reconstruction algorithm, turned out as a reliable tool for detecting supratentorial ICH and IVH. However, detection of infratentorial ICH and perimesencephalic SAH is limited. The potential of FD-CT in detecting ischemic changes is poor in blinded readings. Thus, plain FD-CT seems insufficient as a standalone modality in acute stroke, but within a multimodal imaging approach primarily using the FD technology, native FD-CT seems capable to exclude reliably supratentorial hemorrhage. Currently, FD-CT imaging seems not yet ready for wide adoption, replacing regular CT, and should be reserved for selected patients. Furthermore, prospective evaluations are necessary to validate this approach in the clinical setting.

Catalpol stimulates VEGF production via the JAK2/STAT3 pathway to improve angiogenesis in rats' stroke model

ETHNOBOTANICAL RELEVANCE

Catalpol is the main active component of the radix from Rehmannia glutinosa Libosch, which has pleiotropic protective effects in neurodegenerative diseases, ischemic stroke, metabolic disorders and others

AIM

Catalpol has been shown to have neuroprotective, neurorepair, and angiogenesis effects following ischemic brain injury. However, its molecular mechanisms are still poorly understood. In previous studies, the JAK2/STAT3 signaling pathway was found to play a role in neuroprotection and angiogenesis. This study investigated the role of catalpol in stimulating angiogenesis via the JAK2/STAT3 pathway after permanent focal cerebral ischemia (pMCAO).

METHODS

Rats were subjected to right middle cerebral artery occlusion through electrocoagulation and were treated with catalpol (5mg/kg), AG490 was also used to inhibit STAT3 phosphorylation (pSTAT3).

RESULTS

Following stroke, Catalpol improved the neuroethology deficit, increased the cerebral blood flow (CBF) of infarcted brain and upregulated EPO and EPOR. AG490 suppressed the phosphorylation of signal transducer and activator of transcription 3 (STAT3), ultimately inhibited VEGF mRNA expression, which reduced VEGF protein expression and inhibited stroke-induced angiogenesis. However, Catalpol enhanced stroke-induced STAT3 activation and subsequently restored STAT3 activity through the recovery of STAT3 binding to VEGF. Moreover, Catalpol reversed the effect of AG490 on STAT3 activation and nuclear translocation, restored the transcriptional activity of the VEGF promoter by recruiting STAT3 to the VEGF promoter, improved VEGF mRNA and protein expression, increased angiogenesis, reduced the difference in CBF between the infarcted and intact brain and ameliorated the neuroethology behaviors after stroke.

CONCLUSION

Catalpol affects neuroprotection and angiogenesis via the JAK2/STAT3 signaling pathway, which is mediated by STAT3 activation and VEGF expression. Catalpol may be used as a potential therapeutic drug for stroke.

Update on the effects of treatment with recombinant tissue-type plasminogen activator (rt-PA) in acute ischemic stroke

INTRODUCTION

Acute ischemic stroke (AIS) represents a major cause of death and disability all over the world. The recommended therapy aims at dissolving the clot to re-establish quickly the blood flow to the brain and reduce neuronal injury. Intravenous administration of recombinant tissue-type plasminogen activator (rt-PA) is clinically used with this goal.

AREAS COVERED

A description of beneficial and detrimental effects of rt-PA treatment is addressed. An overview of new therapies against AIS, such as new thrombolytics, sonolysis and sonothrombolysis, endovascular procedures, and association therapies is provided. Updates on the pathophysiological process leading to intracranial hemorrhage (ICH) is also discussed.

EXPERT OPINION

rt-PA treatment in AIS patients is beneficial to recovery outcomes. To weaken risks and improve benefits, it might be relevant to consider: i) a definitive identification of risk factors for symptomatic ICH; ii). a better organization of the health care system to reduce time-to-treatment and enhance discharge management. The pharmacological improvement of new thrombolytic drugs (such as tenecteplase and desmoteplase) targeting harmful and maximally exploiting beneficial effects might further reduce mortality and disability in AIS.

Human endothelial progenitor cells rescue cortical neurons from oxygen-glucose deprivation induced death

BACKGROUND AND AIM

Cerebral ischemia is characterized by both acute and delayed neuronal injuries. Neuro-protection is a major issue that should be properly addressed from a pharmacological point of view, and cell-based treatment approaches are of interest due to their potential pleiotropic effects. Endothelial progenitor cells have the advantage of being mobilized from the bone marrow into the circulation, but have been less studied than other stem cells, such as mesenchymal stem cells. Therefore, the comparison between human endothelial progenitor cells (hEPC) and human mesenchymal progenitor cells (hMSC) in terms of efficacy in rescuing neurons from cell death after transitory ischemia is the aim of the current study, in the effort to address further directions.

MATERIALS AND METHODS

In vitro model of oxygen-glucose deprivation (OGD) on a primary culture of rodent cortical neurons was set up with different durations of exposure: 1, 2 and 3hrs with assessment of neuron survival. The 2hrs OGD was chosen for the subsequent experiments. After 2hrs OGD neurons were either placed in indirect co-culture with hMSC or hEPC or cultured in hMSC or hEPC conditioned medium and cell viability was evaluated by MTT assay.

RESULTS

At day 2 after 2hrs OGD exposure, mean neuronal survival was 47.9±24.2%. In contrast, after treatment with hEPC and hMSC indirect co-culture was 74.1±27.3%; and 69.4±18.8%, respectively. In contrast, treatment with conditioned medium did not provide any advantage in terms of survival to OGD neurons

CONCLUSION

The study shows the efficacy of hEPC in indirect co-culture to rescue neurons from cell death after OGD, comparable to that of hMSC. hEPC deserve further studies given their potential interest for ischemia.

The 3 Rs of Stroke Biology: Radial, Relayed, and Regenerative

Stroke not only causes initial cell death, but also a limited process of repair and recovery. As an overall biological process, stroke has been most often considered from the perspective of early phases of ischemia, how these inter-relate and lead to expansion of the infarct. However, just as the biology of later stages of stroke becomes better understood, the clinical realities of stroke indicate that it is now more a chronic disease than an acute killer. As an overall biological process, it is now more important to understand how early cell death leads to the later, limited recovery so as develop an integrative view of acute to chronic stroke. This progression from death to repair involves sequential stages of primary cell death, secondary injury events, reactive tissue progenitor responses, and formation of new neuronal circuits. This progression is radial: from the tissue that suffers the infarct secondary injury signals, including free radicals and inflammatory cytokines, radiate out from the stroke core to trigger later regenerative events. Injury and repair processes occur not just in the local stroke site, but are also triggered in the connected networks of neurons that had existed in the stroke center: damage signals are relayed throughout a brain network. From these relayed, distributed damage signals, reactive astrocytosis, inflammatory processes, and the formation of new connections occur in distant brain areas. In short, emerging data in stroke cell death studies and the development of the field of stroke neural repair now indicate a continuum in time and in space of progressive events that can be considered as the 3 Rs of stroke biology: radial, relayed, and regenerative.

Improving Outcomes Achieved by a New Stroke Program in Hungary

Background

Stroke is a devastating disease with increasing incidence and prevalence due to population aging. Even with the best care, a proportion of patients dies or is left with significant neurological and cognitive disability. Organization of stroke centers markedly improved outcomes worldwide. We initiated a ‘lysis alarm’ program in September 2013 at our medical center.

Methods

This is a retrospective review of electronic data from patients with acute ischemic stroke before (October 2012-June 2013) and after (October 2013-June 2014) the ‘lysis alarm’ program was introduced at our medical center.

Results

Prior to the introduction of the stroke program, there were only 19 thrombolysis procedures in 777 acute stroke patients in 9 months, while this figure rose to 32 thrombolysis procedures in 737 acute stroke patients after the initiation of the program. The ‘door-to-needle’ time decreased from 88 to 71 min when the two study periods were compared. These changes were associated with decreased stroke mortality in patients receiving thrombolytic treatment (16% prior to the program and 9% during the program). In 2013, there were 1,439 thrombolysis procedures, representing 3.2% of all stroke cases throughout Hungary. After the introduction of the ‘lysis alarm’ program, we have reached a 4% thrombolysis rate at our medical center.

Conclusions

Our thrombolysis rate is higher than the national average, but still low compared to the rates of Western European countries. We are continuously working to enhance our stroke program. Here, we discuss those components that need to be further refined in order to improve stroke intervention and outcome.

Focal cerebral ischemia and neurovascular protection: a bench-to-bedside update

PURPOSE OF REVIEW

To date, many pharmacological approaches, or combination of approaches, have been applied to experimental models of focal cerebral ischemia (FCI), but their translation to clinically effective agents has proved unsuccessful. To date, only thrombolysis with recombinant tissue-type plasminogen activator, or other 'clot-breaking' or 'clot-removal' approaches, have proved effective for acute stroke. This review, therefore, focuses on the 'vascular' phenomena involved in the development of FCI.

RECENT FINDINGS

Recent advances in the experimental literature on FCI describe the microvascular characteristics of the ischemic penumbra, the consequences of cortical spreading depression on impairing cerebral perfusion, and the potential neuroprotective mechanisms of ischemic preconditioning via antithrombotic effects on the neurovascular unit.

SUMMARY

This review provides a perspective about the neurovascular components contributing to the pathophysiology of FCI, and some relevant clinical strategies available on the horizon that hold promise for improved cerebral perfusion in FCI.

Critical early thrombolytic and endovascular reperfusion therapy for acute ischemic stroke victims: a call for adjunct neuroprotection

Today, there is an enormous amount of excitement in the field of stroke victim care due to the recent success of MR. CLEAN, SWIFT PRIME, ESCAPE, EXTEND-IA, and REVASCAT endovascular trials. Successful intravenous (IV) recombinant tissue plasminogen activator (rt-PA) clinical trials [i.e., National Institute of Neurological Disorders and Stroke (NINDS) rt-PA trial, Third European Cooperative Acute Stroke Study (ECASSIII), and Third International Stroke study (IST-3)] also need to be emphasized. In the recent endovascular and thrombolytic trials, there is statistically significant improvement using both the National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Score (mRS) scale, but neither approach promotes complete recovery in patients enrolled within any particular NIHSS or mRS score tier. Absolute improvement (mRS 0-2 at 90 days) with endovascular therapy is 13.5-31 %, whereas thrombolytics alone also significantly improve patient functional independence, but to a lesser degree (NINDS rt-PA trial 13 %). This article has 3 main goals: (1) first to emphasize the utility and cost-effectiveness of rt-PA to treat stroke; (2) second to review the recent endovascular trials with respect to efficacy, safety, and cost-effectiveness as a stroke treatment; and (3) to further consider and evaluate strategies to develop novel neuroprotective drugs. A thesis will be put forth so that future stroke trials and therapy development can optimally promote recovery so that stroke victims can return to "normal" life.

Is CT-Based Perfusion and Collateral Imaging Sensitive to Time Since Stroke Onset?

Purpose

CT-based perfusion and collateral imaging is increasingly used in the assessment of patients with acute stroke. Time of stroke onset is a critical factor in determining eligibility for and benefit from thrombolysis. Animal studies predict that the volume of ischemic penumbra decreases with time. Here, we evaluate if CT is able to detect a relationship between perfusion or collateral status, as assessed by CT, and time since stroke onset.

Materials and methods

We studied 53 consecutive patients with proximal vessel occlusions, mean (SD) age of 71.3 (14.9) years, at a mean (SD) of 125.2 (55.3) minutes from onset, using whole-brain CT perfusion (CTp) imaging. Penumbra was defined using voxel-based thresholds for cerebral blood flow (CBF) and mean transit time (MTT); core was defined by cerebral blood volume (CBV). Normalized penumbra fraction was calculated as Penumbra volume/(Penumbra volume + Core volume) for both CBF and MTT (Pen_CBF and Pen_MTT, respectively). Collaterals were assessed on CT angiography (CTA). CTp ASPECTS score was applied visually, lower scores indicating larger lesions. ASPECTS ratios were calculated corresponding to penumbra fractions.

Results

Both Pen_CBF and Pen_MTT showed decremental trends with increasing time since onset (Kendall’s tau-b = −0.196, p = 0.055, and −0.187, p = 0.068, respectively). The CBF/CBV ASPECTS ratio, which showed a relationship to Pen_CBF (Kendall’s tau-b = 0.190, p = 0.070), decreased with increasing time since onset (Kendall’s tau-b = −0.265, p = 0.006). Collateral response did not relate to time (Kendall’s tau-b = −0.039, p = 0.724).

Conclusion

Even within 4.5 h since stroke onset, a decremental relationship between penumbra and time, but not between collateral status and time, may be detected using perfusion CT imaging. The trends that we demonstrate merit evaluation in larger datasets to confirm our results, which may have potential wider applications, e.g., in the setting of strokes of unknown onset time.