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diagnosis and imaging

Large Core at Presentation Does Not Essentially Translate Into Poor Outcomes, May Be Amenable to Treatment in Select Patients

Kaustubh Limaye, MD

Gautheron V, Xie Y, Tisserand M, Raoult H, Soize S, Naggara O, et al. Outcome After Reperfusion Therapies in Patients With Large Baseline Diffusion-Weighted Imaging Stroke Lesions: A THRACE Trial (Mechanical Thrombectomy After Intravenous Alteplase Versus Alteplase Alone After Stroke) Subgroup Analysis. Stroke. 2018

The treatment landscape of acute ischemic stroke secondary to large vessel occlusion changed significantly in 2015 with the publication of 5 clinical trials that compared intravenous alteplase (IV t-pA) with IV t-pA and intra-arterial therapy (IAT). These clinical trials showed unequivocal benefit in reducing morbidity with the ESCAPE trial even showing mortality benefit. A similar trial conducted at 26 centers in France, THRACE (mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke) randomized 414 acute stroke patients with large vessel occlusion in either arm (IV t-PA vs IV tPA + IAT). 42 % of patients (IV tPA alone) vs. 53% (IV tPA +IAT) achieved functional independence [OR-1.55,95%CI 1.05-2.30; p-0.028], supporting data from the previous clinical trials. As this study was designed before the results of the IMS-III were published, it included patients treated within 4 hours of symptom onset. Other inclusion criteria were age 18-80 years, NIHSS 10-25, both anterior and posterior circulation and initiation of IAT within 5 hours.

Optical Coherence Tomography: New Insights into Cerebral Vasculature

Aristeidis H. Katsanos, MD

Chen CJ, Kumar JS, Chen SH, Ding D, Buell TJ, Sur S, et al. Optical Coherence Tomography: Future Applications in Cerebrovascular Imaging. Stroke. 2018

Optical coherence tomography (OCT) uses low-coherence interferometry to produce two-dimensional images of optical scattering with promising clinical and research applications in the evaluation of vasculature in different regions and settings. Despite an imaging depth of only a few millimeters, OCT can produce significantly higher resolution images than ultrasound due to the inherent properties of light waves to provide higher quality transverse imaging compared to sonic waves.

A Non-Invasive Approach to Monitor Mechanical Thrombectomy Patients Using Near-Infrared Spectroscopy

Shashank Shekhar MD, MS

Ritzenthaler T, Cho T-H, Mechtouff L, Ong E, Turjman F, Robinson P, et al. Cerebral Near-Infrared Spectroscopy: A Potential Approach for Thrombectomy Monitoring. Stroke. 2017

The recently published article in Stroke highlights a rather novel and non-invasive way to monitor thrombectomy patients after large vessel occlusion. Monitoring recanalization and reperfusion during and after mechanical thrombectomy is a therapeutic and diagnostic challenge. In the past, the use of ultrasound and Electroencephalogram devices has been explored with some success. Using functional imaging like Near-infrared spectroscopy (NIRS) allows us to monitor the cerebral regional oxygen saturation continuously. This study is an attempt to answer the question if NIRS could be a better way to monitor mechanical thrombectomy patients.

This pilot study was performed in France using NIRS to find a correlation between regional brain oxygen saturation (rSO2) and MRI perfusion based parameters, reperfusion and clinical outcome. A total of 17 patients were included in the study out of 749 consecutive ischemic admissions. The selection was based on occlusion in the anterior circulation on multimodal MRI with perfusion-weighted imaging. Patients were treated with standard thrombolysis and mechanical thrombectomy with successful recanalization defined as TICI score 2B and 3. NIRS optodes were placed on the bilateral forehead immediately after MRI and kept during mechanical thrombectomy and up to 24 hours. The NIRS device measures the interhemispheric differences (IHD) during this period.

Improved Diagnostic Accuracy of Non-Occlusive Intracranial Vasculopathies With the Use of Vessel Wall Imaging

Sami Al Kasab, MD

Mossa-Basha M, Shibata DK, Hallam DK, de Havenon A, Hippe DS, Becker KJ, et al. Added Value of Vessel Wall Magnetic Resonance Imaging for Differentiation of Nonocclusive Intracranial Vasculopathies. Stroke. 2017

The term intracranial vasculopathy denotes any disease affecting the blood vessels of the brain and meninges. This includes vascular abnormalities due to inflammatory, metabolic, or hereditary conditions; coagulopathy-related disorders; and functional disorders of the blood vessels. Differentiating the type of vasculopathy is important, as treatment is different depending on the type of vasculopathy. Most common intracranial vasculopathies include intracranial atherosclerosis (ICAD), reversible cerebral vasoconstriction syndrome (RCVS), and infectious/inflammatory vasculopathies (IVas).

Recently, intracranial vessel imaging with magnetic resonance imaging (MRI) has emerged as a promising modality to characterize intracranial vasculopathies. Intracranial vessel imaging with MRI has been used to characterize vessel wall as well as vessel lumen. In this study, Mossa-Basha and colleagues compare the diagnostic accuracy of intracranial vessel wall MRI (IVWI) with luminal imaging to luminal imaging alone in non-occlusive vasculopathy differentiation such as ICAD, RCVS, and IVas.

Intracerebral Hemorrhage Shape Predicts the Risk of Intracerebral Hematoma Expansion

Andrea Morotti, MD

Li Q, Liu Q-J, Yang W-S, Wang X-C, Zhao L-B, Xiong X, et al. Island Sign: An Imaging Predictor for Early Hematoma Expansion and Poor Outcome in Patients With Intracerebral Hemorrhage. Stroke. 2017

Intracerebral Hemorrhage (ICH) is a dynamic disease, with up to half of the patients experiencing active bleeding in the acute phase. Hematoma growth represents a potential therapeutic target to improve patients’ outcome. Rapid identification of subjects at high risk of hematoma growth is, therefore, crucial in clinical practice and in the setting of clinical trials testing anti-expansion treatments. The CT angiography (CTA) spot sign is a robust marker of ICH expansion. However, CTA is not available in many institutions, and a large proportion of ICH patients do not receive a CTA as part of their diagnostic workup 1. This highlights the need for novel markers of hematoma growth that do not require a CTA.

Using a well-characterized cohort including 252 ICH patients, Qi Li and colleagues described the island sign, a novel marker of hematoma growth that can be evaluated on baseline non-contrast CT (NCCT). The island sign was defined as presence of at least 3 scattered small hematomas all separate from the main hemorrhage or at least 4 small hematomas, some or all of which may be connected with the main hemorrhage. An illustrative example of the island sign is provided in Figure 1. ICH expansion was defined as hematoma growth > 6mL or > 33% from baseline hematoma volume.

Figure 1. Illustration of island sign. Axial noncontrast computed tomography (CT) images of 4 patients with CT island sign.

Figure 1. Illustration of island sign. Axial noncontrast computed tomography (CT) images of 4 patients with CT island sign.

Peri-Procedural Silent and Clinical Infarctions in Cardiovascular Procedures

Gurmeen Kaur, MBBS

Cho S-M, Deshpande A, Pasupuleti V, Hernandez AV, Uchino K. Radiographic and Clinical Brain Infarcts in Cardiac and Diagnostic Procedures: A Systematic Review and Meta-Analysis. Stroke. 2017

Cardiovascular procedures including Aortic Valve Replacement (AVR), coronary artery bypass grafting (CABG), and cardiac and cerebral catheterization have been associated with increased prevalence of peri-procedural acute ischemic brain lesions on magnetic resonance imaging (MRI).

In this systematic review, Cho et al compared the ratio of radiographic brain infarcts (RBI) to strokes and transient ischemic attacks across cardiac and vascular procedures. RBIs are common after invasive vascular procedures and are encountered a lot more frequently than clinical strokes or TIAs. Literature suggests that peri-procedural ischemic events might serve as a potential surrogate marker for optimizing invasive procedures, which is why an effort was made to compare the rates of RBIs to clinical events.

Using CT Perfusion to Predict Hemorrhagic Transformation

Brian Marcus, MD

Li Q, Gao X, Yao Z, Feng X, He H, Xue J, et al. Permeability Surface of Deep Middle Cerebral Artery Territory on Computed Tomographic Perfusion Predicts Hemorrhagic Transformation After Stroke. Stroke. 2017

The authors of this study utilized CT perfusion (CTP) to assess blood brain barrier integrity and to help predict which patients are at risk of hemorrhagic transformation after receiving tPA and/or mechanical thrombectomy. They note that patients who have proximal MCA-M1/distal ICA occlusions are at an increased susceptibility of hemorrhagic transformation, particularly in the deep MCA territory supplied by the lenticulostriate arteries. They aimed to explore the relationship and potential risk factors between permeability and hemorrhagic transformation in the deep MCA territory by utilizing CT perfusion imaging.

The authors performed a multisite retrospective study, specifically looking at patients that were found to have a deep MCA territory hemorrhagic transformation at 24 hours (and had received CT perfusion and CT angiography on admission). In their study, they noted that patients with a proximal MCA/distal ICA and poor collateral circulation had increased permeability in the deep MCA territory.

Hide and Seek: Using Cardiac MRI to Find a Hidden Clot in ESUS

Kevin S. Attenhofer, MD

Takasugi J, Yamagami H, Noguchi T, Morita Y, Tanaka T, Okuno Y, et al. Detection of Left Ventricular Thrombus by Cardiac Magnetic Resonance in Embolic Stroke of Undetermined Source. Stroke. 2017.

As has been reviewed in this blog many times before, embolic stroke of undetermined source (ESUS) is a novel clinical construct that is a hot topic for emerging diagnostic and therapeutic strategies. While many studies are evaluating methods to increase the detection rate of covert atrial fibrillation in this population, the authors of this paper demonstrate improved detection of left ventricular (LV) thrombi in ESUS patients using cardiac MRI versus TTE.

Currently, echocardiography is the test of choice when evaluating for intra-cardiac thrombus. Transesophageal echocardiography (TEE) is the gold standard technique for detecting left atrial or left atrial appendage thrombi. Transthoracic echocardiography (TTE) is used to evaluate the presence of LV thrombus, patent foramen ovale, depressed ejection fraction, etc. Recently, contrast enhanced cardiac magnetic resonance imaging (CE-CMR) has shown significantly better sensitivity than TTE for the diagnosis of LV thrombus (cardiac studies suggesting sensitivity of TTE was 40%, compared with 88% for CE-CMR) in patients with a history of myocardial infarction (MI) or LV dysfunction (LVEF < 30%).

Author Interview: Ramin Zand, MD, and Vida Abedi, PhD

A conversation with Ramin Zand, MD, Neurology Director of Clinical Stroke Operations, Northeastern Regional Stroke Director, Geisinger Health System, and Associate Professor of Neurology, University of Tennessee Health Science Center, and Vida Abedi, PhD, Research Scientist, Geisinger Health System, and Adjunct Professor, Virginia Tech, about using an artificial neural network to screen for stroke.

Interviewed by José G. Merino, MD, Associate Professor of Neurology, University of Maryland School of Medicine.

They will be discussing the paper “Novel Screening Tool for Stroke Using Artificial Neural Network,” published in the June issue of Stroke.

Dr. Merino: Could you please briefly summarize the key findings and put them in context of what was known before you did the study (i.e. an “elevator pitch” about your research)?

Vida Abedi, PhD

Vida Abedi, PhD

Drs. Zand and Abedi: We have developed ​a new computational method based on artificial intelligence to screen for the stroke in an emergency setting. Previous studies have shown that up to 25% of strokes can be initially misdiagnosed in the emergency department. The failure to recognize stroke in the emergency department is a missed opportunity for intervention. The goal of our study was to test if a supervised learning method could recognize and differentiate stroke from stroke mimics based on the patient demographics, risk factors, and certain clinical elements. Our results showed that in 6 out of the 10 data sets, the precision of our tool for the diagnosis of stroke was >90%. We believe that these methods can serve as a clinical decision support system and assist the emergency providers with early recognition of stroke.

Ramin Zand, MD

Ramin Zand, MD

Author Interview: Seung-Hoon Lee, MD, PhD

Seung-Hoon Lee

Seung-Hoon Lee

A conversation with Seung-Hoon Lee, MD, PhD, Professor of Neurology, Seoul National University Hospital, about the role of the susceptibility vessel sign on SWI to predict stroke subtype and recanalization.

Interviewed by José G. Merino, MD, Associate Professor of Neurology, University of Maryland School of Medicine.

They will be discussing the paper, “Prediction of Stroke Subtype and Recanalization Using Susceptibility Vessel Sign on Susceptibility-Weighted Magnetic Resonance Imaging,” published in the June 2017 issue of Stroke.

Dr. Merino: Could you please briefly describe the study and summarize the key findings, putting them into context of what was known before you did the study?

Dr. Lee: I’m glad to talk about our research in this interview. Thrombi in the cerebral arteries appear hypointense on susceptibility-weighted MRI (SWMRI). We call them “the susceptibility vessel sign” (SVS). The methodological strength of this study is that SWI MRI is much more sensitive than GRE and thus can quantify the size of the SVS. In this study, we analyzed the relationship between the size of the SVS, the stroke mechanism, and whether successful recanalization occurred in patients receiving endovascular treatment. Cardiac emboli are large but fragile because they are rich in RBCs but have scant platelets. We hypothesized that because the SVS reflects the red blood cell component of the clot, patients with larger SVS are more likely to have a cardioembolic source and thus more likely to have successful recanalization. We found that as the SVS size increased, the probability of cardioembolic stroke was higher, but that SVS size did not show any positive or negative correlation with successful recanalization. This is probably due to the high recanalization rate with the stent-retrievers, irrespective of stroke etiology. No association between SVS size and recanalization can be partly explained by clot fragility in cardioembolic stroke.