Magnetic resonance imaging in acute ischemic stroke treatment

SDS-Net: A Synchronized Dual-Stage Network for Predicting Patients Within 4.5-h Thrombolytic Treatment Window Using MRI

Timely and precise identification of acute ischemic stroke (AIS) within 4.5 h is imperative for effective treatment decision-making. This study aims to construct a novel network that utilizes limited datasets to recognize AIS patients within this critical window. We conducted a retrospective analysis of 265 AIS patients who underwent both fluid attenuation inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) within 24 h of symptom onset. Patients were categorized based on the time since stroke onset (TSS) into two groups: TSS ≤ 4.5 h and TSS > 4.5 h. The TSS was calculated as the time from stroke onset to MRI completion. We proposed a synchronized dual-stage network (SDS-Net) and a sequential dual-stage network (Dual-stage Net), which were comprised of infarct voxel identification and TSS classification stages. The models were trained on 181 patients and validated on an independent external cohort of 84 patients using metrics of area under the curve (AUC), sensitivity, specificity, and accuracy. A DeLong test was used to statistically compare the performance of the two models. SDS-Net achieved an accuracy of 0.844 with an AUC of 0.914 in the validation dataset, outperforming the Dual-stage Net, which had an accuracy of 0.822 and an AUC of 0.846. In the external test dataset, SDS-Net further demonstrated superior performance with an accuracy of 0.800 and an AUC of 0.879, compared to the accuracy of 0.694 and AUC of 0.744 of Dual-stage Net (P = 0.049). SDS-Net is a robust and reliable tool for identifying AIS patients within a 4.5-h treatment window using MRI. This model can assist clinicians in making timely treatment decisions, potentially improving patient outcomes.

Ischemic Stroke in Patients Under Oral Anticoagulation: The Achilles Heel of Atrial Fibrillation Management

Oral anticoagulation (OAC) is essential for preventing ischemic stroke events in patients with atrial fibrillation (AF), and leads to a significant ischemic prophylaxis, when appropriately used. However, there is still a risk of experiencing stroke events, despite being under anticoagulation. Stroke despite OAC is an increasingly common diagnosis, and pathophysiologically, it can be associated with several etiologies, ranging from AF competing mechanisms to true anticoagulation failure. While the cardioembolic origin of stroke is the most frequently identified etiology, other factors also have to be considered, as there is a significance risk of coexistence. This highlights the need for thorough diagnostic testing, evaluating each stroke etiology independently, with the use of imaging, biomarker and blood tests. Treating such patients, however, is more complex, as there is still uncertainty regarding the selection of OAC post-stroke, with data showing a superiority of direct OAC (DOAC), compared to vitamin K antagonists, in recurrent ischemic stroke prevention and conflicting results regarding OAC switch. Finally, the additive value of cardiac interventions, such as left atrial appendage occlusion (LAAO), in secondary prevention of stroke, is being explored, as it could potentially lead to significant stroke risk reduction. This review, therefore, provides an updated summary of the pathophysiology, diagnostics and therapeutics of stroke under OAC, while also discussing the future direction on the Achilles heel of AF management.

Artificial intelligence in stroke rehabilitation: From acute care to long-term recovery

Stroke is a leading cause of disability worldwide, driving the need for advanced rehabilitation strategies. The integration of Artificial Intelligence (AI) into stroke rehabilitation presents significant advancements across the continuum of care, from acute diagnosis to long-term recovery. This review explores AI's role in stroke rehabilitation, highlighting its impact on early diagnosis, motor recovery, and cognitive rehabilitation. AI-driven imaging techniques, such as deep learning applied to CT and MRI scans, improve early diagnosis and identify ischemic penumbra, enabling timely, personalized interventions. AI-assisted decision support systems optimize acute stroke treatment, including thrombolysis and endovascular therapy. In motor rehabilitation, AI-powered robotics and exoskeletons provide precise, adaptive assistance, while AI-augmented Virtual and Augmented Reality environments offer immersive, tailored recovery experiences. Brain-Computer Interfaces utilize AI for neurorehabilitation through neural signal processing, supporting motor recovery. Machine learning models predict functional recovery outcomes and dynamically adjust therapy intensities. Wearable technologies equipped with AI enable continuous monitoring and real-time feedback, facilitating home-based rehabilitation. AI-driven tele-rehabilitation platforms overcome geographic barriers by enabling remote assessment and intervention. The review also addresses the ethical, legal, and regulatory challenges associated with AI implementation, including data privacy and technical integration. Future research directions emphasize the transformative potential of AI in stroke rehabilitation, with case studies and clinical trials illustrating the practical benefits and efficacy of AI technologies in improving patient recovery.

Impact of Small Vessel Disease on Patient Outcomes After Intravenous Thrombolysis for Acute Ischemic Stroke

Individual cerebral small vessel disease (SVD) markers independently predict poor prognosis after stroke. However, the impact of a single SVD, especially cumulative SVD burden, on outcomes in acute ischemic stroke (AIS) after intravenous thrombolysis remains unclear. This study evaluated the occurrence of SVD in patients with AIS who were treated with intravenous thrombolytic therapy using multimodal magnetic resonance imaging. The study involved patients with AIS who received multimodal magnetic resonance imaging scans before receiving intravenous thrombolytic treatment with recombinant tissue plasminogen activator (rt-PA). Validated scales were used to document each SVD characteristic and measure the overall impact of SVD using an extensive scoring method. Functional outcomes were evaluated using the modified Rankin scale score within a 3-month time frame, with poor outcomes categorized as a modified Rankin scale score of ≥2. Using a logistic regression model while accounting for potential confounding variables, we examined the relation among individual SVD characteristics, the overall SVD impact, and patient outcomes. In total, 282 patients were included. Severe white matter hyperintensities and lacunas were linked to negative clinical results in patients with SVD, even after accounting for age, National Institutes of Health Stroke Scale score at admission, onset to treatment time, and hypertension (odds ratio 2.394, 95% confidence interval 1.246 to 4.6; odds ratio 2.3, 95% confidence interval 1.214 to 4.36, respectively). When evaluating the SVD global burden, a strong association between the SVD score and negative clinical results was observed, except for cases with an SVD score of 2 points. The findings suggest that the presence of pre-existing SVD, particularly characterized by the severity of white matter changes and lacunes, has a detrimental impact on the clinical outcomes of patients with ischemic stroke receiving intravenous rt-PA treatment. In conclusion, this information could be useful for predicting the prognosis of patients with stroke who underwent intravenous rt-PA therapy.

Metrology for MRI: the field you've never heard of

Quantitative MRI has been an active area of research for decades and has produced a huge range of approaches with enormous potential for patient benefit. In many cases, however, there are challenges with reproducibility which have hampered clinical translation. Quantitative MRI is a form of measurement and like any other form of measurement it requires a supporting metrological framework to be fully consistent and compatible with the international system of units. This means not just expressing results in terms of seconds, meters, etc., but demonstrating consistency to their internationally recognized definitions. Such a framework for MRI is not yet complete, but a considerable amount of work has been done internationally towards building one. This article describes the current state of the art for MRI metrology, including a detailed description of metrological principles and how they are relevant to fully quantitative MRI. It also undertakes a gap analysis of where we are versus where we need to be to support reproducibility in MRI. It focusses particularly on the role and activities of national measurement institutes across the globe, illustrating the genuinely international and collaborative nature of the field.

Beyond conventional imaging: A systematic review and meta-analysis assessing the impact of computed tomography perfusion on ischemic stroke outcomes in the late window

BACKGROUND

Non-contrast cranial computed tomography (NCCT) and CT angiogram (CTA) have become essential for endovascular treatment (EVT) in acute stroke. Patient selection may improve when CT perfusion (CTP) imaging is also added for patient selection. We aimed to analyze the effects of implementing CTP in acute ischemic stroke (AIS) patients' treatment to assess whether stroke outcomes differ in the late window.

METHODS

We searched the PubMed, Embase, and Web of Sciences databases to obtain articles related to CTA and CTP in EVT. Collected patient data were split into two groups: the CTP and control (NCCT + CTA) cohorts. Primary outcomes evaluated were modified Rankin Scale (mRS) scores, symptomatic intracranial hemorrhages (sICHs), mortality, and successful recanalization.

RESULTS

There were 14 studies with 5809 total patients in the final analysis: 2602 received CTP and 3202 were in the control group. CTP/CTA patients showed significantly lower rates of 90-day stroke-related mortality (odds ratio (OR) = 0.72, 95% confidence interval (CI) = 0.60-0.87, p < 0.01) and significantly higher successful recanalization (OR = 1.42, 95% CI = 1.06-1.94, p < 0.01) compared with CTA-only patients. Analysis of other outcomes including functional independence (mRS = 0-2), critical times, and intracranial hemorrhages was non-significant (p > 0.05).

CONCLUSION

The study highlights the usefulness of CTP-guided therapy as a supplementary tool in EVT selection in the late window. Although the addition of CTP resulted in lower mortality, the favorable outcomes did not improve. Further evidence is required to establish a clearer understanding of the potential advantages or limitations of incorporating CTP in stroke imaging.

Predictive Value of Hyperintense Acute Reperfusion Marker in Transient Ischemic Attacks: Stroke Recurrence and TOAST Classification

BACKGROUND

Transient ischemic attack (TIA) is a recognized precursor of stroke that also indicates a high risk of recurrence. The Hyperintense Acute Reperfusion Marker (HARM), which is linked to blood-brain barrier disruption, may serve as a novel imaging biomarker for TIA.

METHODS

A retrospective cohort study of 715 patients with TIA evaluated the predictive value of HARM for stroke recurrence and its association with TOAST subtype. Imaging findings, including those of diffusion-weighted imaging, were analyzed using logistic regression.

RESULTS

HARM-positive patients had significantly higher recurrence rates at 3 months (20.9%; odds ratio [OR] = 5.3) and 1 year (30.2%; OR = 5.8) compared to HARM-negative patients, relative to other imaging markers (p < 0.001). HARM was significantly associated with the cardioembolic stroke (p < 0.001).

CONCLUSIONS

HARM is a promising imaging biomarker for predicting stroke recurrence and etiology in patients experiencing TIA. Incorporating HARM into clinical frameworks may enhance diagnostic and prognostic accuracy.

A wrapper method for finding optimal subset of multimodal Magnetic Resonance Imaging sequences for ischemic stroke lesion segmentation

Multimodal data, while being information-rich, contains complementary as well as redundant information. Depending on the target problem some modalities are more informative and thus relevant for decision-making. Identifying the optimal subset of modalities best suited to solve a particular task significantly reduces the complexity of acquisition without compromising performance. In this work, we propose a wrapper method for examining the importance of Magnetic Resonance Imaging (MRI) sequences for ischemic stroke lesion segmentation using a deep neural network trained for segmentation. Importance score for each modality is computed through a combinatorial dropout of input modalities at inference coupled with a systematic evaluation its impact on the model's performance. Experimental evaluation of the proposed method is performed on two publicly available datasets: (i) ISLES15 - comprising seven MRI sequences for 30 cases and (ii) ISLES22 - comprising of three MRI sequences for 250 cases. We identified DWI, Tmax and T1c as the optimal set of MRI sequences for core-penumbra delineation and Tmax as the optimal sequence for lesion segmentation in ISLES15 dataset. In ISLES22 dataset, DWI was identified as the optimal sequence for lesion segmentation. In addition to the exhaustive experimental validation, visually interpretable evidence for accuracy of the identified optimal subset is provided in the form of saliency maps.

Transcranial Cortex-Wide Imaging of Murine Ischemic Perfusion With Large-Field Multifocal Illumination Microscopy

BACKGROUND

Ischemic stroke is a common cause of death worldwide and a main cause of morbidity. Presently, laser speckle contrast imaging, x-ray computed tomography, and magnetic resonance imaging are the mainstay for stroke diagnosis and therapeutic monitoring in preclinical studies. These modalities are often limited in terms of their ability to map brain perfusion with sufficient spatial and temporal resolution, thus calling for development of new brain perfusion techniques featuring rapid imaging speed, cost-effectiveness, and ease of use.

METHODS

We report on a new preclinical high-resolution angiography technique for murine ischemic stroke imaging based on large-field high-speed multifocal illumination fluorescence microscopy. We subsequently showcase the proposed method by monitoring therapeutic effects of thrombolysis in stroke (n=6), further performing cross-strain comparison of perfusion dynamics (n=6) and monitoring the therapeutic effects of sensory stimulation-based treatment (n=11).

RESULTS

Quantitative readings of hemodynamic and structural changes in cerebral vascular network and pial vessels were attained with 14.4-µm spatial resolution at 80-Hz frame rate fully transcranially. The in vivo perfusion maps accurately delineated the ischemic core and penumbra, further exhibiting a strong correlation (86.1±4.5%) with ex vivo triphenyl tetrazolium chloride staining, significantly higher than for the conventional laser speckle contrast imaging method. Monitoring of therapeutic effects of thrombolysis confirmed that early recanalization could effectively save the penumbra while reducing the infarct area. Cross-strain comparison of perfusion dynamics affirmed that C57BL/6 mice feature a larger penumbra and smaller infarct core as compared with BALB/c mice, which have few or no collaterals. Sensory stimulation-based treatment could effectively enhance blood flow and abolish perfusion deficits in the ischemic core and penumbra regions.

CONCLUSIONS

A high-speed fluorescence-based angiography method for transcranial stroke imaging in mice is introduced, which is capable of localizing brain perfusion changes and accurately assessing the ischemic penumbra. Compared with the whole-brain x-ray computed tomography and magnetic resonance imaging methods, which are conventionally used for stroke diagnosis and therapeutic monitoring, the new approach is simple and cost-effective, further offering high resolution and speed for in vivo studies. It thus opens new venues for brain perfusion research under various disease conditions such as stroke, neurodegeneration, or epileptic seizures.

Non-Contrast MRI Sequences for Ischemic Stroke: A Concise Overview for Clinical Radiologists

Ischemic stroke is the second leading cause of mortality and morbidity worldwide. Due to the urgency of implementing immediate therapy, acute stroke necessitates prompt diagnosis. The current gold standards for vascular imaging in stroke include computed tomography angiography (CTA), digital subtraction angiography (DSA) and magnetic resonance angiography (MRA). However, the contrast agents used in these methods can be costly and pose risks for patients with renal impairment or allergies. The aim of this paper is to provide a comprehensive overview of current MRI techniques and sequences for evaluating ischemic stroke, emphasizing the importance of non-contrast options and their clinical implications for radiologists in the diagnosis and management of ischemic stroke. Standard MRI sequences-such as T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), DWI-FLAIR mismatch, and apparent diffusion coefficient (ADC)-are essential for determining infarct location, volume, and age. Additionally, incorporating susceptibility-weighted imaging (SWI) sequence aids in identifying signs of hemorrhagic transformation within the infarcted region. Advanced techniques like arterial spin labeling (ASL) can serve as a non-contrast alternative for mapping cerebral blood flow (CBF) and allowing for comparison between infarcted and healthy brain areas. Adding ASL to the routine sequence allows ASL-DWI mismatch analysis that is useful for quantifying salvageable tissue volume and facilitate timely recanalization, while time-of-flight (TOF) MRA and magnetic resonance venography (MRV) help assess venous thrombosis, stenosis, or arterial occlusions. Finally, MR spectroscopy can provide insights into critical brain metabolites, including N-acetylaspartate (NAA), and lactate (Lac) to determine patient prognosis. Current MRI technology provides a myriad of sequence options for the comprehensive evaluation of ischemic stroke without the need for contrast material. A thorough understanding of the advantages and limitations of each sequence is crucial for its optimal implementation in diagnosis and treatment.

Assessment of Deep Learning-Based Triage Application for Acute Ischemic Stroke on Brain MRI in the ER

RATIONALE AND OBJECTIVES

To assess a deep learning application (DLA) for acute ischemic stroke (AIS) detection on brain magnetic resonance imaging (MRI) in the emergency room (ER) and the effect of T2-weighted imaging (T2WI) on its performance.

MATERIALS AND METHODS

We retrospectively analyzed brain MRIs taken through the ER from March to October 2021 that included diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences. MRIs were processed by the DLA, and sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve (AUROC) were evaluated, with three neuroradiologists establishing the gold standard for detection performance. In addition, we examined the impact of axial T2WI, when available, on the accuracy and processing time of DLA.

RESULTS

The study included 947 individuals (mean age ± standard deviation, 64 years ± 16; 461 men, 486 women), with 239 (25%) positive for AIS. The overall performance of DLA was as follows: sensitivity, 90%; specificity, 89%; accuracy, 89%; and AUROC, 0.95. The average processing time was 24 s. In the subgroup with T2WI, T2WI did not significantly impact MRI assessments but did result in longer processing times (35 s without T2WI compared to 48 s with T2WI, p < 0.001).

CONCLUSION

The DLA successfully identified AIS in the ER setting with an average processing time of 24 s. The absence of performance acquire with axial T2WI suggests that the DLA can diagnose AIS with just axial DWI and FLAIR sequences, potentially shortening the exam duration in the ER.

Study of Time-Resolved Dynamics in Turbid Medium Using a Single-Cavity Dual-Comb Laser

In measuring cerebral blood flow (CBF) noninvasively using optical techniques, diffusing-wave spectroscopy is often combined with near-infrared spectroscopy to obtain a reliable blood flow index. Measuring the blood flow index at a determined depth remains the ultimate goal. In this study, we present a simple approach using dual-comb lasers where we simultaneously measure the absorption coefficient (μa), the reduced scattering coefficient (μs '), and dynamic properties. This system can also effectively differentiate dynamics from various depths, which is crucial for analyzing multilayer dynamics. For CBF measurements, this capability is particularly valuable as it helps mitigate the influence of the scalp and skull, thereby enhancing the specificity of deep tissue.

Atypical Sensory Loss Pattern in an Isolated Thalamic Stroke: A Case Report

This case report discusses a 51-year-old male who presented to the emergency department (ED) with left-sided hemiparesthesia and left leg incoordination. The initial brain computed tomography (CT) scan was negative, and the follow-up brain CT three days after the onset of symptoms was also negative. Although sensitivity and specificity are not 100%, CT remains the first-line diagnostic test for detecting a cerebrovascular accident (CVA). In this unique case, CT was not sufficient. Following two negative CT scans, magnetic resonance imaging (MRI) finally revealed the cause of this patient's symptoms, an ischemic incident in the right thalamus. Thalamic strokes typically present with contralateral hemiparesis and hemisensory loss, unreactive pupils, and gaze palsy with gaze deviation away from the side of the infarct. It is unusual to see a thalamic lesion present with pure hemiparesthesia without facial involvement. This patient's clinical presentation is discussed, as well as future investigations and ways to prevent this diagnostic delay. This case demonstrates the importance of follow-up imaging based on the clinical presentation of potentially subtle imaging findings.

Brain Diffusion Changes in Perinatal Asphyxia Cases

BACKGROUND

Prolonged perinatal asphyxia (PA) may cause hypoxic-ischemic damage to the brain. The aim of this study was to investigate the brain diffusion changes of patients with PA and examine the relationship with brain damage.

METHODS

This retrospective study included 55 patients diagnosed with PA, separated into mild and severe PA groups. For the evaluation of brain damage in all the study neonates, brain and diffusion MRI scans were performed using a 3T device. The scans were taken between 5 and 10 days postnatal, after completion of hypothermia treatment, in accordance with the standard clinical protocol of our institution. Apparent diffusion coefficient (ADC) values of the lentiform nucleus, thalamus, frontal white matter, and posterior limbs of the internal capsule were measured. Minitab package programs and SPSS version 20.0 software were used for statistical analysis and graphic drawing. Spearman's rank correlation analysis was used.

RESULTS

The bilateral lentiform nucleus, thalamus, frontal white matter, and posterior limbs of the internal capsule ADC values were significantly higher in the severe PA group than in the mild PA group.

CONCLUSIONS

In neonates with severe perinatal asphyxia, brain damage can be evaluated on diffusion-weighted imaging (DWI) of the cerebral deep white matter and basal ganglia. DWI, imaging with conventional brain MRI comes to the fore in clinical importance in PA patients.

Comparison of Bilateral Versus Unilateral 5 Hz or 1 Hz Repetitive Transcranial Magnetic Stimulation in Subacute Stroke: Assessment of Motor Function in a Randomized Controlled Study

PURPOSE

Repetitive transcranial magnetic stimulation (rTMS) can enhance brain plasticity after stroke. At low frequencies, rTMS has an inhibitory effect, whereas at high frequencies, it has an excitatory effect. Combining both frequencies in bilateral stimulation is a new rTMS protocol under investigation, especially in the subacute stage.

METHODS

Fifty-five patients with subacute stroke were divided into four groups according to the rTMS protocol delivered: bilateral, inhibitory, excitatory, and control groups. All groups received concomitant task-oriented physiotherapy. Pretreatment to posttreatment assessment was performed twice, immediately after sessions and 1 month later. Volitional motor control was evaluated by Fugl-Meyer and Wolf motor function tests, and for spasticity, the Ashworth scale was used.

RESULTS

All groups showed significant improvement. Bilateral, inhibitory, and excitatory groups showed same efficacy, but the bilateral protocol was superior in spasticity. No correlations were found between improvement and stroke duration and site except for spasticity.

CONCLUSIONS

Bilateral rTMS shows a comparable effect to inhibitory and excitatory rTMS in improving motor disability in subacute stroke. However, it is superior for spasticity.

Current State of Evidence for Neuroimaging Paradigms in Management of Acute Ischemic Stroke

Stroke is the chief differential diagnosis in patient presenting to the emergency room with abrupt onset focal neurological deficits. Neuroimaging, including non-contrast computed tomography (CT), magnetic resonance imaging (MRI), vascular and perfusion imaging, is a cornerstone in the diagnosis and treatment decision-making. This review examines the current state of evidence behind the different imaging paradigms for acute ischemic stroke diagnosis and treatment, including current recommendations from the guidelines. Non-contrast CT brain, or in some centers MRI, can help differentiate ischemic stroke and intracerebral hemorrhage (ICH), a pivotal juncture in stroke diagnosis and treatment algorithm, especially for early window thrombolytics. Advanced imaging such as MRI or perfusion imaging can also assist making a diagnosis of ischemic stroke versus mimics such as migraine, Todd's paresis, or functional disorders. Identification of medium-large vessel occlusions with CT or MR angiography triggers consideration of endovascular thrombectomy (EVT), with additional perfusion imaging help identify salvageable brain tissue in patients who are likely to benefit from reperfusion therapies, particularly in the ≥6 h window. We also review recent advances in neuroimaging and ongoing trials in key therapeutic areas and their imaging selection criteria to inform the readers on potential future transitions into use of neuroimaging for stroke diagnosis and treatment decision making. ANN NEUROL 2024;95:1017-1034.

Estimating the volume of penumbra in rodents using DTI and stack-based ensemble machine learning framework

BACKGROUND

This study investigates the potential of diffusion tensor imaging (DTI) in identifying penumbral volume (PV) compared to the standard gadolinium-required perfusion-diffusion mismatch (PDM), utilizing a stack-based ensemble machine learning (ML) approach with enhanced explainability.

METHODS

Sixteen male rats were subjected to middle cerebral artery occlusion. The penumbra was identified using PDM at 30 and 90 min after occlusion. We used 11 DTI-derived metrics and 14 distance-based features to train five voxel-wise ML models. The model predictions were integrated using stack-based ensemble techniques. ML-estimated and PDM-defined PVs were compared to evaluate model performance through volume similarity assessment, the Pearson correlation analysis, and Bland-Altman analysis. Feature importance was determined for explainability.

RESULTS

In the test rats, the ML-estimated median PV was 106.4 mL (interquartile range 44.6-157.3 mL), whereas the PDM-defined median PV was 102.0 mL (52.1-144.9 mL). These PVs had a volume similarity of 0.88 (0.79-0.96), a Pearson correlation coefficient of 0.93 (p < 0.001), and a Bland-Altman bias of 2.5 mL (2.4% of the mean PDM-defined PV), with 95% limits of agreement ranging from -44.9 to 49.9 mL. Among the features used for PV prediction, the mean diffusivity was the most important feature.

CONCLUSIONS

Our study confirmed that PV can be estimated using DTI metrics with a stack-based ensemble ML approach, yielding results comparable to the volume defined by the standard PDM. The model explainability enhanced its clinical relevance. Human studies are warranted to validate our findings.

RELEVANCE STATEMENT

The proposed DTI-based ML model can estimate PV without the need for contrast agent administration, offering a valuable option for patients with kidney dysfunction. It also can serve as an alternative if perfusion map interpretation fails in the clinical setting.

KEY POINTS

• Penumbral volume can be estimated by DTI combined with stack-based ensemble ML. • Mean diffusivity was the most important feature used for predicting penumbral volume. • The proposed approach can be beneficial for patients with kidney dysfunction.

Ketamine-induced prevention of SD-associated late infarct progression in experimental ischemia

Spreading depolarizations (SDs) occur frequently in patients with malignant hemispheric stroke. In animal-based experiments, SDs have been shown to cause secondary neuronal damage and infarct expansion during the initial period of infarct progression. In contrast, the influence of SDs during the delayed period is not well characterized yet. Here, we analyzed the impact of SDs in the delayed phase after cerebral ischemia and the potential protective effect of ketamine. Focal ischemia was induced by distal occlusion of the left middle cerebral artery in C57BL6/J mice. 24 h after occlusion, SDs were measured using electrocorticography and laser-speckle imaging in three different study groups: control group without SD induction, SD induction with potassium chloride, and SD induction with potassium chloride and ketamine administration. Infarct progression was evaluated by sequential MRI scans. 24 h after occlusion, we observed spontaneous SDs with a rate of 0.33 SDs/hour which increased during potassium chloride application (3.37 SDs/hour). The analysis of the neurovascular coupling revealed prolonged hypoemic and hyperemic responses in this group. Stroke volume increased even 24 h after stroke onset in the SD-group. Ketamine treatment caused a lesser pronounced hypoemic response and prevented infarct growth in the delayed phase after experimental ischemia. Induction of SDs with potassium chloride was significantly associated with stroke progression even 24 h after stroke onset. Therefore, SD might be a significant contributor to delayed stroke progression. Ketamine might be a possible drug to prevent SD-induced delayed stroke progression.

Automated Ischemic Stroke Classification from MRI Scans: Using a Vision Transformer Approach

Background: This study evaluates the performance of a vision transformer (ViT) model, ViT-b16, in classifying ischemic stroke cases from Moroccan MRI scans and compares it to the Visual Geometry Group 16 (VGG-16) model used in a prior study. Methods: A dataset of 342 MRI scans, categorized into 'Normal' and 'Stroke' classes, underwent preprocessing using TensorFlow's tf.data API. Results: The ViT-b16 model was trained and evaluated, yielding an impressive accuracy of 97.59%, surpassing the VGG-16 model's 90% accuracy. Conclusions: This research highlights the ViT-b16 model's superior classification capabilities for ischemic stroke diagnosis, contributing to the field of medical image analysis. By showcasing the efficacy of advanced deep learning architectures, particularly in the context of Moroccan MRI scans, this study underscores the potential for real-world clinical applications. Ultimately, our findings emphasize the importance of further exploration into AI-based diagnostic tools for improving healthcare outcomes.

Association of Bovine Arch Anatomy With Incident Stroke After Transcatheter Aortic Valve Replacement

BACKGROUND

Acute ischemic stroke complicates 2% to 3% of transcatheter aortic valve replacements (TAVRs). This study aimed to identify the aortic anatomic correlates in patients after TAVR stroke.

METHODS AND RESULTS

This is a single-center, retrospective study of patients who underwent TAVR at the Mayo Clinic between 2012 and 2022. The aortic arch morphology was determined via a manual review of the pre-TAVR computed tomography images. An "a priori" approach was used to select the covariates for the following: (1) the logistic regression model assessing the association between a bovine arch and periprocedural stroke (defined as stroke within 7 days after TAVR); and (2) the Cox proportional hazards regression model assessing the association between a bovine arch and long-term stroke after TAVR. A total of 2775 patients were included (59.6% men; 97.8% White race; mean±SD age, 79.3±8.4 years), of whom 495 (17.8%) had a bovine arch morphology. Fifty-seven patients (1.7%) experienced a periprocedural stroke. The incidence of acute stroke was significantly higher among patients with a bovine arch compared with those with a nonbovine arch (3.6% versus 1.7%; P=0.01). After adjustment, a bovine arch was independently associated with increased periprocedural strokes (adjusted odds ratio, 2.16 [95% CI, 1.22-3.83]). At a median follow-up of 2.7 years, the overall incidence of post-TAVR stroke was 6.0% and was significantly higher in patients with a bovine arch even after adjusting for potential confounders (10.5% versus 5.0%; adjusted hazard ratio, 2.11 [95% CI, 1.51-2.93]; P<0.001).

CONCLUSIONS

A bovine arch anatomy is associated with a significantly higher risk of periprocedural and long-term stroke after TAVR.

Unlocking the Potential of Stroke Blood Biomarkers: Early Diagnosis, Ischemic vs. Haemorrhagic Differentiation and Haemorrhagic Transformation Risk: A Comprehensive Review

Stroke, a complex and heterogeneous disease, is a leading cause of morbidity and mortality worldwide. The timely therapeutic intervention significantly impacts patient outcomes, but early stroke diagnosis is challenging due to the lack of specific diagnostic biomarkers. This review critically examines the literature for potential biomarkers that may aid in early diagnosis, differentiation between ischemic and hemorrhagic stroke, and prediction of hemorrhagic transformation in ischemic stroke. After a thorough analysis, four promising biomarkers were identified: Antithrombin III (ATIII), fibrinogen, and ischemia-modified albumin (IMA) for diagnostic purposes; glial fibrillary acidic protein (GFAP), micro RNA 124-3p, and a panel of 11 metabolites for distinguishing between ischemic and hemorrhagic stroke; and matrix metalloproteinase-9 (MMP-9), s100b, and interleukin 33 for predicting hemorrhagic transformation. We propose a biomarker panel integrating these markers, each reflecting different pathophysiological stages of stroke, that could significantly improve stroke patients' early detection and treatment. Despite promising results, further research and validation are needed to demonstrate the clinical utility of this proposed panel for routine stroke treatment.

Comparing the predictive value of quantitative magnetic resonance imaging parametric response mapping and conventional perfusion magnetic resonance imaging for clinical outcomes in patients with chronic ischemic stroke

Predicting clinical outcomes after stroke, using magnetic resonance imaging (MRI) measures, remains a challenge. The purpose of this study was to investigate the prediction of long-term clinical outcomes after ischemic stroke using parametric response mapping (PRM) based on perfusion MRI data. Multiparametric perfusion MRI datasets from 30 patients with chronic ischemic stroke were acquired at four-time points ranging from V2 (6  weeks) to V5 (7  months) after stroke onset. All perfusion MR parameters were analyzed using the classic whole-lesion approach and voxel-based PRM at each time point. The imaging biomarkers from each acquired MRI metric that was predictive of both neurological and functional outcomes were prospectively investigated. For predicting clinical outcomes at V5, it was identified that PRMTmax-, PRMrCBV-, and PRMrCBV+ at V3 were superior to the mean values of the corresponding maps at V3. We identified correlations between the clinical prognosis after stroke and MRI parameters, emphasizing the superiority of the PRM over the whole-lesion approach for predicting long-term clinical outcomes. This indicates that complementary information for the predictive assessment of clinical outcomes can be obtained using PRM analysis. Moreover, new insights into the heterogeneity of stroke lesions revealed by PRM can help optimize the accurate stratification of patients with stroke and guide rehabilitation.

Changes in Cerebral Blood Flow and Diffusion-Weighted Imaging Lesions After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a common subtype of stroke and places a great burden on the family and society with a high mortality and disability rate and a poor prognosis. Many findings from imaging and pathologic studies have suggested that cerebral ischemic lesions visualized on diffusion-weighted imaging (DWI) in patients with ICH are not rare and are generally considered to be associated with poor outcome, increased risk of recurrent (ischemic and hemorrhagic) stroke, cognitive impairment, and death. In this review, we describe the changes in cerebral blood flow (CBF) and DWI lesions after ICH and discuss the risk factors and possible mechanisms related to the occurrence of DWI lesions, such as cerebral microangiopathy, cerebral atherosclerosis, aggressive early blood pressure lowering, hyperglycemia, and inflammatory response. We also point out that a better understanding of cerebral DWI lesions will be a key step toward potential therapeutic interventions to improve long-term recovery for patients with ICH.

Research and application advances in rehabilitation assessment of stroke

Stroke has a high incidence and disability rate, and rehabilitation is an effective means to reduce the disability rate of patients. To systematize rehabilitation assessment, which is the foundation for rehabilitation therapy, we summarize the assessment methods commonly used in research and clinical applications, including the various types of stroke rehabilitation scales and their applicability, and related biomedical detection technologies, including surface electromyography (sEMG), motion analysis systems, transcranial magnetic stimulation (TMS), magnetic resonance imaging (MRI), and combinations of different techniques. We also introduce some assessment techniques that are still in the experimental phase, such as the prospective application of artificial intelligence (AI) with optical correlation tomography (OCT) in stroke rehabilitation. This review provides a useful bibliography for the assessment of not only the severity of stroke injury, but also the therapeutic effects of stroke rehabilitation, and establishes a solid base for the future development of stroke rehabilitation skills.

Systolic blood pressure and recurrent stroke in patients with different lesion patterns on diffusion weighted imaging

Little is known about the relationship between baseline systolic blood pressure (SBP) and subsequent clinical events in patients with different lesion patterns on diffusion weighted imaging (DWI). We analyzed the Acute Non‐disabling Cerebrovascular Events (CHANCE) trial dataset. Patients were categorized into negative DW imaging (no detectable lesions), lacunar infarction (single lesion ≤15 mm) and non‐lacunar infarction (single lesion >15 mm or multiple lesions) based on lesion patterns on DWI. The primary outcome was recurrent stroke within 90 days. Cox proportional hazards models were used to assess the association between SBP levels and stroke outcomes in patients with different lesion patterns. A total of 1089 patients were analyzed. We found 258 cases (23.7%) with negative DW imaging, 392 (36.0%) with lacunar infarction and 439 (40.3%) with non‐lacunar infarction. Patients with non‐lacunar infarction had the highest incidence of stroke at 90‐day (P < .001). In non‐lacunar infarction group, compared with SBP < 160 mmHg, patients with SBP ≥ 160 mmHg had significantly higher risk of 90‐day recurrent stroke (20.3% vs. 10.7%; adjusted hazard ratio 1.81, 95% confidence interval 1.09–3.00). No significant association was found between SBP and clinical outcomes in patients with negative DWI and lacunar stroke groups. The result at 1 year was similar as at 90‐day. Therefore, non‐lacunar infarction, the most common lesion pattern in CHANCE study, had the highest risk of recurrent stroke and combined vascular events both in 90 days and 1 year. High baseline SBP was significantly associated with increased risk of short‐ and long‐term recurrent strokes in patients with non‐lacunar infarction.

Magnetic Resonance Imaging in Acute Ischemic Stroke

Ischemic stroke is one of the leading causes of mortality and disability. The only effective non-surgical treatment for acute ischemic stroke within three to four and a half hours of the onset of symptoms is thrombolytic therapy. Time is of the essence when diagnosing and treating an acute ischemic stroke. After evaluating the advantages and disadvantages of thrombolysis, selecting the ideal patient for the indication is essential. Magnetic Resonance Imaging (MRI) is more sensitive and specific than Computed Tomography (CT) scans when identifying acute ischemic stroke. In approximately 80% of cases, infarcts are detectable within the first 24 hours. MRI can detect an ischemic stroke within a few hours of its onset. Multimodal imaging provides information for the diagnosis of ischemic stroke, patient selection for thrombolytic therapy, and prognosis estimation.

Application of Multimodal Magnetic Resonance Imaging in Green Channel of Acute and Hyperacute Ischemic Stroke

The purpose of this study was to observe the effects of multimodal magnetic resonance imaging (MRI) in the green channel of acute and hyperacute ischemic strokes, in order to better guide clinical treatment. The clinical data of 126 patients with acute and hyperacute ischemic stroke who received interventional treatment in the emergency green channel was collected retrospectively. The patients who received multimodal computed tomography (CT) were included in the CT group. Patients who underwent multimodal MRI examinations were included in the MRI group, and the door-to-needle time (DNT), neurological function, and prognosis of the two groups were compared. The result turned out that among the 126 patients included, 40 patients underwent CT examination (CT group) and 86 patients underwent MRI examination (MRI group). A comparison of general data between the CT group and the MRI group showed $P>0.05$ . The MRI group’s DNT time (61.23 ± 9.32) min was shorter than that of the CT group (87.22 ± 14.26) min, $P<0.05$ . Through comparison, the $P$ values of mRS scores and NIHSS scores in both groups were greater than 0.05. After treatment, the mRS score and NIHSS score of the MRI group was lower, with $P<0.05$ . According to the results of this study, it can be concluded that emergency multimodal MRI could shorten the DNT time of patients with acute and hyperacute ischemic stroke, reduce the degree of neurological impairment, and improve the prognosis.

Anti-Inflammatory Effect of Beta-Caryophyllene Mediated by the Involvement of TRPV1, BDNF and trkB in the Rat Cerebral Cortex after Hypoperfusion/Reperfusion

We have previously shown that bilateral common carotid artery occlusion followed by reperfusion (BCCAO/R) is a model to study early hypoperfusion/reperfusion-induced changes in biomarkers of the tissue physiological response to oxidative stress and inflammation. Thus in this study, we investigate with immunochemical assays if a single dose of beta-caryophyllene (BCP), administered before the BCCAO/R, can modulate the TRPV1, BDNF, and trkB receptor in the brain cortex; the glial markers GFAP and Iba1 were also examined. Frontal and temporal-occipital cortical regions were analyzed in two groups of male rats, sham-operated and submitted to BCCAO/R. Six hours before surgery, one group was gavage fed a dose of BCP (40 mg/per rat in 300 μL of sunflower oil), the other was pre-treated with the vehicle alone. Western blot analysis showed that, in the frontal cortex of vehicle-treated rats, the BCCAO/R caused a TRPV1 decrease, an increment of trkB and GFAP, no change in BDNF and Iba1. The BCP treatment caused a decrease of BDNF and an increase of trkB levels in both sham and BCCAO/R conditions while inducing opposite changes in the case of TRPV1, whose levels became higher in BCCAO/R and lower in sham conditions. Present results highlight the role of BCP in modulating early events of the cerebral inflammation triggered by the BCCAO/R through the regulation of TRPV1 and the BDNF-trkB system.

Selecting the Appropriate First-Line Strategy Based on Hyperdense Vessel Sign in Acute Ischemic Stroke Increases First Pass Recanalization: A Tertiary Center Experience

Background:  The data pertaining to selecting an optimal first-line strategy (stent retriever [SR] vs. contact aspiration [CA]) based on noncontrast computed tomography (NCCT) in cases of acute ischemic stroke consequent to large vessel occlusion (LVO) is lacking.

Aims:  This article studies the influence of hyperdense vessel sign (HVS) in selecting optimal first-line strategy, with intention of increasing first-pass recanalization (FPR).

Methods:  Upfront approach at our center is SR technique with rescue therapy (CA) adoption consequent to three failed SR attempts to achieve successful recanalization. Data of patients with acute LVO who underwent mechanical thrombectomy from June 2017 to May 2020 was retrospectively analyzed. Patients were classified into HVS (+) and HVS (−) cohort. Rate of successful recanalization (first pass, early, and final) and efficacy of rescue therapy was assessed between the two cohorts.

Results:  Of 52 patients included, 28 and 24 were assigned to the HVS (+) and HVS (−) cohort, respectively. FPR was observed in 50% of HVS (+) and 20.9% of HVS (−) ( p  = 0.029). Early recanalization was documented in 64.2% of HVS (+) and 37.5% of HVS (−) ( p  = 0.054). Rescue therapy need was higher in patients not demonstrating HVS ( p  = 0.062). Successful recanalization was achieved with rescue therapy in 50% of HVS (−) group.

Conclusion:  A higher FPR is achievable following individualized first-pass strategy (based on NCCT appearance of clot), instead of a generalized SR first-pass approach. This CT imaging-based strategy is a step closer to achieving primary angiographic goal of FPR.

Contemporary Neuroprotection Strategies during Cardiac Surgery: State of the Art Review

Open-heart surgery is the leading cause of neuronal injury in the perioperative state, with some patients complicating with cerebrovascular accidents and delirium. Neurological fallout places an immense burden on the psychological well-being of the person affected, their family, and the healthcare system. Several randomised control trials (RCTs) have attempted to identify therapeutic and interventional strategies that reduce the morbidity and mortality rate in patients that experience perioperative neurological complications. However, there is still no consensus on the best strategy that yields improved patient outcomes, such that standardised neuroprotection protocols do not exist in a significant number of anaesthesia departments. This review aims to discuss contemporary evidence for preventing and managing risk factors for neuronal injury, mechanisms of injury, and neuroprotection interventions that lead to improved patient outcomes. Furthermore, a summary of existing RCTs and large observational studies are examined to determine which strategies are supported by science and which lack definitive evidence. We have established that the overall evidence for pharmacological neuroprotection is weak. Most neuroprotective strategies are based on animal studies, which cannot be fully extrapolated to the human population, and there is still no consensus on the optimal neuroprotective strategies for patients undergoing cardiac surgery. Large multicenter studies using universal standardised neurological fallout definitions are still required to evaluate the beneficial effects of the existing neuroprotective techniques.

Current approaches and advances in the imaging of stroke

A stroke occurs when the blood flow to the brain is suddenly interrupted, depriving brain cells of oxygen and glucose and leading to further cell death. Neuroimaging techniques, such as computed tomography and magnetic resonance imaging, have greatly improved our ability to visualise brain structures and are routinely used to diagnose the affected vascular region of a stroke patient's brain and to inform decisions about clinical care. Currently, these multimodal imaging techniques are the backbone of the clinical management of stroke patients and have immensely improved our ability to visualise brain structures. Here, we review recent developments in the field of neuroimaging and discuss how different imaging techniques are used in the diagnosis, prognosis and treatment of stroke.

Summary: Stroke imaging has undergone seismic shifts in the past decade. Although magnetic resonance imaging (MRI) is superior to computed tomography in providing vital information, further research on MRI is still required to bring its full potential into clinical practice.

Detection and vascular territorial classification of stroke on diffusion-weighted MRI by deep learning

PURPOSE

Rapid detection and vascular territorial classification of stroke enable the determination of the most appropriate treatment. In this study, we aimed to investigate the performance of convolutional neural network (CNN) models in the detection and vascular territorial classification of stroke on diffusion-weighted images (DWI).

METHODS

DWI of 421 cases (271 acute ischemic stroke patients and 150 cases without any ischemia findings on DWI) obtained between January 2017 to April 2020 were reviewed. We created two custom datasets. A stroke detection dataset was created with 1800 slices (900 S and 900 normal) consisting of 1400 for training, 200 for validation, 200 for test. A vascular territorial type dataset was created with 1717 slices (883 middle cerebral artery stroke, 416 posterior circulatory stroke, and 418 watershed stroke) consisting of 1117 slices for training, 300 for validation, 300 for test. A transfer learning approach based on MobileNetV2 and EfficientNet-B0 CNN architecture was used. The performance of the models was evaluated.

RESULTS

Modified MobileNetV2 and EfficientNet-B0 models achieved 96% (κ: 0.92) and 93% (κ: 0.86) accuracy in stroke detection, respectively. In vascular territorial classification of stroke as middle cerebral artery, posterior circulation, or watershed infarction, an accuracy of 93% (κ: 0.895) was achieved with modified MobileNetV2 model and 87% (κ: 0.805) with modified EfficientNet-B0 CNN model.

CONCLUSION

Transfer learning approach with custom top CNN models achieve sufficiently high performance for both the detection of ischemic stroke and the classification of its vascular territorial type on DWI.

Atrial Fibrillation Related and Unrelated Stroke Recurrence Among Ischemic Stroke Patients With Atrial Fibrillation

Background: Ischemic stroke with atrial fibrillation (AF) may recur despite appropriate treatment. It may be AF-related or AF-unrelated. We compared the factors associated with AF-related and AF-unrelated recurrences among ischemic stroke patients with AF. Methods: Patients with ischemic stroke and AF were enrolled from 11 centers in Korea. Ischemic stroke recurrence was classified as AF-related if the lesion pattern was compatible with cardioembolism without significant stenosis or as AF-unrelated if the lesion was more likely due to small vessel disease or arterial stenosis. Factors associated with stroke recurrence (AF-related and AF-unrelated) were investigated. Results: Among the 2,239 patients, 115 (5.1%) experienced recurrence (75 AF-related and 40 AF-unrelated). Factors independently associated with any stroke recurrence included AF diagnosed before stroke, small subcortical infarctions, and small scattered lesions in a single vascular territory. Type of AF was associated with the type of stroke recurrence, with persistent AF being associated with AF-related stroke [hazard ratio (HR) = 2.94, 95% confidence interval (CI) 1.69-5.26; p < 0.001]. By contrast, paroxysmal AF (HR = 3.76, 95% CI 1.56-9.04; p = 0.003), AF diagnosed before stroke (HR = 2.38, 95% CI 1.19-4.55; p = 0.014), small scattered lesions in a single vascular territory (reference: corticosubcortical lesion, HR = 3.19, 95% CI 1.18-8.63; p = 0.022), and the use of antiplatelet agents (HR = 2.11, 95% CI 1.11-4.03; p = 0.024) were independently associated with AF-unrelated stroke. Conclusion: Persistent AF was more associated with AF-related stroke recurrence, whereas paroxysmal AF was more associated with AF-unrelated stroke recurrence. A scattered lesion in a single vascular territory may predict AF-unrelated stroke recurrence.

Developing a model for estimating infarction onset time based on computed tomography radiomics in patients with acute middle cerebral artery occlusion

BACKGROUND

Radiomics analysis is a newly emerging quantitative image analysis technique. The aim of this study was to extract a radiomics signature from the computed tomography (CT) imaging to determine the infarction onset time in patients with acute middle cerebral artery occlusion (MCAO).

METHODS

A total of 123 patients with acute MCAO in the M1 segment (85 patients in the development cohort and 38 patients in the validation cohort) were enrolled in the present study. Clinicoradiological profiles, including head CT without contrast enhancement and computed tomographic angiography (CTA), were collected. The time from stroke onset (TFS) was classified into two subcategories: ≤ 4.5 h, and > 4.5 h. The middle cerebral artery (MCA) territory on CT images was segmented to extract and score the radiomics features associated with the TFS. In addition, the clinicoradiological factors related to the TFS were identified. Subsequently, a combined model of the radiomics signature and clinicoradiological factors was constructed to distinguish the TFS ≤ 4.5 h. Finally, we evaluated the overall performance of our constructed model in an external validation sample of ischemic stroke patients with acute MCAO in the M1 segment.

RESULTS

The area under the curve (AUC) of the radiomics signature for discriminating the TFS in the development and validation cohorts was 0.770 (95% confidence interval (CI): 0.665-0.875) and 0.792 (95% CI: 0.633-0.950), respectively. The AUC of the combined model comprised of the radiomics signature, age and ASPECTS on CT in the development and validation cohorts was 0.808 (95% CI: 0.701-0.916) and 0.833 (95% CI: 0.702-0.965), respectively. In the external validation cohort, the AUC of the radiomics signature was 0.755 (95% CI: 0.614-0.897), and the AUC of the combined model was 0.820 (95% CI: 0.712-0.928).

CONCLUSIONS

The CT-based radiomics signature is a valuable tool for discriminating the TFS in patients with acute MCAO in the M1 segment, which may guide the use of thrombolysis therapy in patients with indeterminate stroke onset time.

Diffusion-Weighted Imaging Reveals Distinct Patterns of Cytotoxic Edema in Patients with Subdural Hematomas

Subdural hematomas (SDHs) are increasingly common and can cause ischemic brain injury. Previous work has suggested that this is driven largely by vascular compression from herniation, although this work was done before the era of magnetic resonance imaging (MRI). We thus sought to study SDH-related ischemic brain injury by looking at patterns of cytotoxic edema on diffusion-weighted MRI. To do so, we identified all SDH patients at a single institution from 2015 to 2019 who received an MRI within 2 weeks of presentation. We reviewed all MRIs for evidence of restricted diffusion consistent with cytotoxic edema. Cases were excluded if the restricted diffusion could have occurred as a result of alternative etiologies (e.g., cardioembolic stroke or diffuse axonal injury). We identified 450 SDH patients who received an MRI within 2 weeks of presentation. Twenty-nine patients (∼6.5% of all MRIs) had SDH-related cytotoxic edema, which occurred in two distinct patterns. In one pattern (N = 9), patients presented as comatose with severe midline shift and were found to have cytotoxic edema in the vascular territories of the anterior and posterior cerebral artery, consistent with herniation-related vascular compression. In the other pattern (N = 19), patients often presented as awake with less midline shift and developed cytotoxic edema in the cortex adjacent to the SDH outside of typical vascular territories (peri-SDH cytotoxic edema). Both patterns occurred in 1 patient. The peri-SDH cytotoxic edema pattern is a newly described type of secondary injury and may involve direct toxic effects of the SDH, spreading depolarizations, or other mechanisms.

Study of correlations between CT properties of retrieved cerebral thrombi with treatment outcome of stroke patients

Background

All the patients with suspected stroke are directed to whole-brain CT scan. The purpose of this scan is to look for early features of ischemia and to rule out alternative diagnoses than stroke. In case of ischemic stroke, CT diagnostics (including CT angiography) is used mainly to locate the occlusion and its size, while the Hounsfield Units (HU) values of the thrombus causing the stroke are usually overlooked on CT scan or considered not important. The aim of this study was to demonstrate that the HU value is relevant and can help in better treatment planning.

Patients and methods

There were 25 patients included in the study, diagnosed with ischemic stroke in the middle cerebral artery (MCA) territory. In all patients, systemic thrombolysis was not successful and the mechanical recanalization was needed. The retrieved thrombi were also analyzed histologically for the determination of red blood cells (RBC) proportion. CT of the proximal MCA (M1) segment was analyzed for average HU value and its variability both in the occluded section and the symmetrical normal site. These CT parameters were then statistically studied for the possible correlations with different clinical, histological and procedure parameters using the Linear Regression and the Pearson correlation coefficient.

Results

Relevant positive correlations were found between average HU value of thrombus and outcome modified Rankin Scale (mRS), initial mRS, number of passes with thrombectomy device as well as RBC proportion.

Conclusions

Results of the present study suggest that measured HU values in CT images of the cerebral thrombi may help in the assessment of thrombus compaction and therefore better treatment planning.

Finger Exoskeleton in Simple Motor Rehabilitation Therapy on Arm and Hand Muscle Ability of Post-Stroke Sufferers

Post-stroke sufferers will generally experience weakness on one side of the body, balance, vision, sensory, motor, and cognitive. In West Kalimantan, the estimated stroke sufferer in 2013 was 25,195 people. Based on data from the Public Hospital of  Dr. Soedarso Pontianak shows a significant increase from January 2018 to December 2018 totaling 722 people. The research objective was to assess the effectiveness of the finger exoskeleton tool in simple motor therapy on the ability of the client's arm and hand muscles after a stroke. This study used a quantitative approach with a quasi-experimental design. Pre-test and Post-test Nonequivalent Control Group with two groups, which were the control group of 12 people and the intervention group of 12 people with finger exoskeleton tools. The statistical test used was the independent t test and paired t test. Measurement of muscle ability with the Action Research Arm Test. Analysis of the difference in total scores between before and after treatment in the intervention group using Paired T-Test obtained a p-value of 0.000 (p value <0.05) and in the control group using the Wilcoxon test a p-value of  0.016 (p value <0.05). It shows that there is a significant difference in the total score between before and after finger exoskeleton therapy and range of motion. Intervention of finger exoskeleton assistive devices in simple motor rehabilitation therapy is effective in increasing the ability of the client's arm and hand muscles after stroke. It is recommended to make another finger rehabilitation tool with a more optimal design according to the parameters, which are the severity of the client after stroke, subject kinematics, control of movement torque and adaptation between the subject and the robotic device used.

Biocompatible BSA-MnO2 nanoparticles for in vivo timely permeability imaging of blood-brain barrier and prediction of hemorrhage transformation in acute ischemic stroke

Hemorrhage transformation (HT) is a frequent but maybe fatal complication following acute ischemic stroke due to severe damage of the blood-brain barrier (BBB). Quantitative BBB permeability imaging is a promising method to predict HT in stroke patients for a favorable prognosis. However, clinical gadolinium chelate-based magnetic resonance (MR) imaging of the stroke suffers from a relatively low sensitivity and potential side effects of nephrogenic systemic fibrosis and intracranial gadolinium deposition. Herein, BSA-MnO2 nanoparticles (BM NPs) fabricated by a facile disinfection-mimic method were employed for the permeability imaging of BBB in the stroke for the first time. The BM NPs showed a high T1 relaxivity (r1 = 5.9 mM-1 s-1), remarkable MR imaging ability, and good biocompatibility, allowing the noninvasive timely visualization of BBB permeability in the model rats of middle cerebral artery occlusion (MCAO). Furthermore, increased peak intensity, extended imaging duration, and expanded imaging region indicated by BM NPs in MR imaging showed a good prediction for the onset of HT in MCAO rats. Therefore, BM NPs hold an attractive potential to be an alternative biocompatible MR contrast agent for the noninvasive BBB permeability imaging in vivo, benefiting the fundamental research of diverse neurological disorders and the clinical treatment for stroke patients.

23 Na MRI in ischemic stroke: Acquisition time reduction using postprocessing with convolutional neural networks

Quantitative ²³ Na magnetic resonance imaging (MRI) provides tissue sodium concentration (TSC), which is connected to cell viability and vitality. Long acquisition times are one of the most challenging aspects for its clinical establishment. K-space undersampling is an approach for acquisition time reduction, but generates noise and artifacts. The use of convolutional neural networks (CNNs) is increasing in medical imaging and they are a useful tool for MRI postprocessing. The aim of this study is ²³ Na MRI acquisition time reduction by k-space undersampling. CNNs were applied to reduce the resulting noise and artifacts. A retrospective analysis from a prospective study was conducted including image datasets from 46 patients (aged 72 ± 13 years; 25 women, 21 men) with ischemic stroke; the ²³ Na MRI acquisition time was 10 min. The reconstructions were performed with full dataset (FI) and with a simulated dataset an image that was acquired in 2.5 min (RI). Eight different CNNs with either U-Net-based or ResNet-based architectures were implemented with RI as input and FI as label, using batch normalization and the number of filters as varying parameters. Training was performed with 9500 samples and testing included 400 samples. CNN outputs were evaluated based on signal-to-noise ratio (SNR) and structural similarity (SSIM). After quantification, TSC error was calculated. The image quality was subjectively rated by three neuroradiologists. Statistical significance was evaluated by Student's t-test. The average SNR was 21.72 ± 2.75 (FI) and 10.16 ± 0.96 (RI). U-Nets increased the SNR of RI to 43.99 and therefore performed better than ResNet. SSIM of RI to FI was improved by three CNNs to 0.91 ± 0.03. CNNs reduced TSC error by up to 15%. The subjective rating of CNN-generated images showed significantly better results than the subjective image rating of RI. The acquisition time of ²³ Na MRI can be reduced by 75% due to postprocessing with a CNN on highly undersampled data.

Tissue Sodium Concentration within White Matter Correlates with the Extent of Small Vessel Disease

INTRODUCTION

Sodium MRI (23Na MRI) derived biomarkers such as tissue sodium concentration (TSC) provide valuable information on cell function and brain tissue viability and has become a reliable tool for the assessment of brain tumors and ischemic stroke beyond pathoanatomical morphology. Patients with major stroke often suffer from different degrees of underlying white matter lesions (WMLs) attributed to chronic small vessel disease. This study aimed to evaluate the WM TSC in patients with an acute ischemic stroke and to correlate the TSC with the extent of small vessel disease. Furthermore, the reliability of relative TSC (rTSC) compared to absolute TSC in these patients was analyzed.

METHODOLOGY

We prospectively examined 62 patients with acute ischemic stroke (73 ± 13 years) between November 2016 and August 2019 from which 18 patients were excluded and thus 44 patients were evaluated. A 3D 23Na MRI was acquired in addition to a T2-TIRM and a diffusion-weighted image. Coregistration and segmentation were performed with SPM 12 based on the T2-TIRM image. The extension of WM T2 hyperintense lesions in each patient was classified using the Fazekas scale of WMLs. The absolute TSC in the WM region was correlated to the Fazekas grades. The stroke region was manually segmented on the coregistered absolute diffusion coefficient image and absolute, and rTSC was calculated in the stroke region and compared to nonischemic WM region. Statistical significance was evaluated using the Student t-test.

RESULTS

For patients with Fazekas grade I (n = 25, age: 68.5 ± 15.1 years), mean TSC in WM was 55.57 ± 7.43 mM, and it was not statistically significant different from patients with Fazekas grade II (n = 7, age: 77.9 ± 6.4 years) with a mean TSC in WM of 53.9 ± 6.4 mM, p = 0.58. For patients with Fazekas grade III (n = 9, age: 81.4 ± 7.9 years), mean TSC in WM was 68.7 ± 10.5 mM, which is statistically significantly higher than the TSC in patients with Fazekas grade I and II (p < 0.001 and p = 0.05, respectively). There was a positive correlation between the TSC in WM and the Fazekas grade with r = 0.48 p < 0.001. The rTSC in the stroke region was statistically significant difference between low (0 and I) and high (2 and 3) Fazekas grades (p = 0.0353) whereas there was no statistically significant difference in absolute TSC in the stroke region between low (0 and I) and high (2 and 3) Fazekas grades.

CONCLUSION

The significant difference in absolute TSC in WM in patients with severe small vessel disease; Fazekas grade 3 can lead to inaccuracies using rTSC quantification for evaluation of acute ischemic stroke using 23 Na MRI. The study, therefore, emphasizes the importance of absolute tissue sodium quantification.

Exploring the predictive value of lesion topology on motor function outcomes in a porcine ischemic stroke model

Harnessing the maximum diagnostic potential of magnetic resonance imaging (MRI) by including stroke lesion location in relation to specific structures that are associated with particular functions will likely increase the potential to predict functional deficit type, severity, and recovery in stroke patients. This exploratory study aims to identify key structures lesioned by a middle cerebral artery occlusion (MCAO) that impact stroke recovery and to strengthen the predictive capacity of neuroimaging techniques that characterize stroke outcomes in a translational porcine model. Clinically relevant MRI measures showed significant lesion volumes, midline shifts, and decreased white matter integrity post-MCAO. Using a pig brain atlas, damaged brain structures included the insular cortex, somatosensory cortices, temporal gyri, claustrum, and visual cortices, among others. MCAO resulted in severely impaired spatiotemporal gait parameters, decreased voluntary movement in open field testing, and higher modified Rankin Scale scores at acute timepoints. Pearson correlation analyses at acute timepoints between standard MRI metrics (e.g., lesion volume) and functional outcomes displayed moderate R values to functional gait outcomes. Moreover, Pearson correlation analyses showed higher R values between functional gait deficits and increased lesioning of structures associated with motor function, such as the putamen, globus pallidus, and primary somatosensory cortex. This correlation analysis approach helped identify neuroanatomical structures predictive of stroke outcomes and may lead to the translation of this topological analysis approach from preclinical stroke assessment to a clinical biomarker.

Prevalence of Imaging Targets in Patients With Minor Stroke Selected for IV tPA Treatment Using MRI: The Treatment of Minor Stroke With MRI Evaluation Study (TIMES)

OBJECTIVE

To determine the IV tissue plasminogen activator (tPA) treatment rate of patients with minor acute ischemic stroke (mAIS) at our centers and compare the frequency of MRI targets by treatment stratification and clinical severity, we evaluated clinical characteristics and baseline MRIs for tPA-treated and untreated patients.

METHODS

Patients with ischemic stroke from 2015 to 2017 with admit NIH Stroke Scale (NIHSS) <6 were considered. The treated cohort received standard IV tPA and was screened with baseline MRI. The untreated cohort received no acute intervention and baseline MRI was <4 hours from onset. Patients were stratified into "clearly" and "not clearly" disabling deficits by NIHSS elements. Baseline MRI was evaluated by independent raters for AIS targets, with frequencies compared between groups.

RESULTS

Of 255 patients with mAIS ≤4.5 hours from onset, 140 (55%) received IV tPA, accounting for 46% of all IV tPA patients (n = 305). Eighty-five percent (n = 119) were screened with baseline MRI and had significantly more frequent imaging targets compared to those untreated (n = 90). Of this treated cohort, 75% (n = 89) were not clearly disabling. Except for perfusion-diffusion mismatch (81% clearly disabling vs 56% not clearly disabling [p = 0.036]), there were no significant differences in the frequency of imaging targets across the treated cohort stratified by clinical severity.

CONCLUSIONS

In MRI-screened mAIS, imaging targets were more frequently seen in patients treated with IV tPA, with similar frequencies even in those without clearly disabling deficits. MRI targets could be used to guide thrombolytic therapy in patients with mAIS; however, a randomized trial is needed to demonstrate efficacy.

Association between stroke occurrence and changes in atmospheric circulation

Background

The impact of weather on morbidity from stroke has been analysed in previous studies. As the risk of stroke was mostly associated with changing weather, the changes in the daily stroke occurrence may be associated with changes in atmospheric circulation. The aim of our study was to detect and evaluate the association between daily numbers of ischaemic strokes (ISs) and haemorrhagic strokes (HSs) and the teleconnection pattern.

Methods

The study was performed in Kaunas, Lithuania, from 2000 to 2010. The daily numbers of ISs, subarachnoid haemorrhages (SAHs), and intracerebral haemorrhages (ICHs) were obtained from the Kaunas Stroke Register. We evaluated the association between these types of stroke and the teleconnection pattern by applying Poisson regression and adjusting for the linear trend, month, and other weather variables.

Results

During the study period, we analysed 4038 cases (2226 men and 1812 women) of stroke. Of these, 3245 (80.4%) cases were ISs, 533 (13.2%) cases were ICHs, and 260 (6.4%) cases were SAHs. An increased risk of SAH was associated with a change in mean daily atmospheric pressure over 3.9 hPa (RR = 1.49, 95% CI 1.14–1.96), and a stronger El Niño event had a protective effect against SAHs (RR = 0.34, 95% CI 0.16–0.69). The risk of HS was positively associated with East Atlantic/West Russia indices (RR = 1.13, 95% CI 1.04–1.23). The risk of IS was negatively associated with the Arctic Oscillation index on the same day and on the previous day (RR = 0.97, p < 0.033). During November–March, the risk of HS was associated with a positive North Atlantic Oscillation (NAO) (RR = 1.29, 95% CI 1.03–1.62), and the risk of IS was negatively associated with the NAO index (RR = 0.92, 95% CI 0.85–0.99).

Conclusions

The results of our study provide new evidence that the North Atlantic Oscillation, Arctic Oscillation, East Atlantic/West Russia, and El Niño-Southern Oscillation pattern may affect the risk of stroke. The impact of these teleconnections is not identical for various types of stroke. Emergency services should be aware that specific weather conditions are more likely to prompt calls for more severe strokes.

Endovascular Treatment of Acute Ischemic Stroke

PURPOSE OF REVIEW

This article reviews the actual indications for mechanical thrombectomy in patients with acute ischemic stroke and how the opportunities for endovascular therapy can be expanded by using the concept of clinical-imaging or perfusion-imaging mismatch (as a surrogate for salvageable tissue) rather than time of ischemia.

RECENT FINDINGS

Six randomized controlled trials undoubtedly confirmed the benefits of using endovascular thrombectomy on the clinical outcome of patients with stroke with large vessel occlusion within 6 hours from symptom onset compared with those receiving only standard medical care. In a meta-analysis of individual patient data, the number needed to treat with endovascular thrombectomy to reduce disability by at least one level on the modified Rankin Scale for one patient was 2.6. Recently, the concept of "tissue window" versus time window has proved useful for selecting patients for mechanical thrombectomy up to 24 hours from symptom onset. The DAWN (DWI or CTP Assessment With Clinical Mismatch in the Triage of Wake-Up and Late Presenting Strokes Undergoing Neurointervention) trial included patients at a median of 12.5 hours from onset and showed the largest effect in functional outcome ever described in any acute stroke treatment trial (35.5% increase in functional independence). In DEFUSE 3 (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution 3), patients treated with mechanical thrombectomy at a median of 11 hours after onset had a 28% increase in functional independence and an additional 20% absolute reduction in death or severe disability.

SUMMARY

For patients with acute ischemic stroke and a large vessel occlusion in the proximal anterior circulation who can be treated within 6 hours of stroke symptom onset, mechanical thrombectomy with a second-generation stent retriever or a catheter aspiration device should be indicated regardless of whether the patient received treatment with intravenous (IV) recombinant tissue plasminogen activator (rtPA) in patients with limited signs of early ischemic changes on neuroimaging. Two clinical trials completely disrupted the time window concept in acute ischemic stroke, showing excellent clinical outcomes in patients treated up to 24 hours from symptom onset. Time of ischemia is, on average, a good biomarker for tissue viability; however, the window of opportunity for treatment varies across different individuals because of a range of compensatory mechanisms. Adjusting time to the adequacy of collateral flow leads to the concept of tissue window, a paradigm shift in stroke reperfusion therapy.

Mechanism of Stroke According to the Severity and Location of Atherosclerotic Middle Cerebral Artery Disease

BACKGROUND AND PURPOSE

Strategy for secondary prevention of ischemic stroke depends on the mechanism of stroke. The aim of this study was to compare the stroke mechanism according to the location and severity of middle cerebral artery (MCA) disease.

METHODS

We analyzed acute ischemic stroke patients within 7 days of onset with symptomatic MCA disease. The location of MCA disease was classified into proximal MCA M1 (pMCA) and distal MCA M1/proximal M2 (dMCA). The mechanism of stroke was categorized according to the pattern of ischemic lesion: local branch occlusion, artery-to-artery embolism/hemodynamic infarction, in situ-thrombosis, or a combined mechanism. The mechanism and imaging characteristics of stroke were compared according to the location and severity. The factors associated with the stroke mechanism were also investigated.

RESULTS

A symptomatic MCA disease was observed in 126 patients (74 pMCA and 52 dMCA). The mechanism of stroke differed according to the location (p < 0.001); the combined mechanism was most common in pMCA disease (54.1%), especially in those who presented with MCA occlusion and with a susceptible vessel sign. Artery-to-artery embolism/hemodynamic infarction was most common in dMCA disease (46.2%). A longer length of stenosis was observed in local branch occlusion than in other mechanisms (p = 0.04) and was an independent factor associated with local branch occlusion (OR=1.631, 95% CI=1.161-2.292; p = 0.005).

CONCLUSIONS

The mechanism of stroke differed according to the location of MCA disease: occlusion caused by plaque rupture with combined mechanism of stroke type was predominant in pMCA. Longer length of stenosis was associated with local branch occlusion.

Pathophysiologic mechanisms, neuroimaging and treatment in wake-up stroke

Wake-up stroke (WUS) or ischemic stroke occurring during sleep accounts for 14%-29.6% of all ischemic strokes. Management of WUS is complicated by its narrow therapeutic time window and attributable risk factors, which can affect the safety and efficacy of administering intravenous (IV) tissue plasminogen activator (t-PA). This manuscript will review risk factors of WUS, with a focus on obstructive sleep apnea, potential mechanisms of WUS, and evaluate studies assessing safety and efficacy of IV t-PA treatment in WUS patients guided by neuroimaging to estimate time of symptom onset. The authors used PubMed (1966 to March 2018) to search for the term "Wake-Up Stroke" cross-referenced with "pathophysiology," ''pathogenesis," "pathology," "magnetic resonance imaging," "obstructive sleep apnea," or "treatment." English language Papers were reviewed. Also reviewed were pertinent papers from the reference list of the above-matched manuscripts. Studies that focused only on acute Strokes with known-onset of symptoms were not reviewed. Literature showed several potential risk factors associated with increased risk of WUS. Although the onset of WUS is unknown, a few studies investigated the potential benefit of magnetic resonance imaging (MRI) in estimating the age of onset which encouraged conducting clinical trials assessing the efficacy of MRI-guided thrombolytic therapy in WUS.

Liquid biopsy markers for stroke diagnosis

INTRODUCTION

There is a short time window (4.5 h) for the effective treatment of acute ischemic stroke (AIS), which uses recombinant tissue plasminogen activator (rt-PA). Unfortunately, this short therapeutic timeframe is a contributing factor to the relatively small number of patients (~7%) that receive rt-PA. While neuroimaging is the major diagnostic for AIS, more timely decisions could be made using a molecular diagnostic.

AREAS COVERED

In this review, we survey neuroimaging techniques used to diagnose stroke and their limitations. We also highlight the potential of various molecular/cellular biomarkers, especially peripheral blood-based (i.e. liquid biopsy) biomarkers, for diagnosing stroke to allow for precision decisions on managing stroke in a timely manner. Both protein and nucleic acid molecular biomarkers are reviewed. In particular, mRNA markers are discussed for AIS and hemorrhagic stroke diagnosis sourced from both cells and extracellular vesicles.

EXPERT OPINION

While there are a plethora of molecular markers for stroke diagnosis that have been reported, they have yet to be FDA-cleared. Possible reasons include the inability for these markers to appear in sufficient quantities for highly sensitive clinical decisions within the rt-PA therapeutic time.