Bijoy K Menon

Bijoy K Menon
The University of Calgary | HBI · Department of Clinical Neurosciences, Radiology and Community Health Sciences

MBBS, M.D, D.M, MSc, FRCPC

About

589
Publications
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20,590
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Introduction
My current research interests are in developing easy to use imaging tools that aid in understanding acute ischemic stroke pathophysiology and help in patient selection. I am also passionate about understanding leptomeningeal collateral physiology, processes around hyperacute stroke treatment, biostatistics and clinical trials methodology.
Additional affiliations
January 2009 - December 2012
The University of Calgary
June 2003 - August 2006
Madras Medical College
Position
  • Medical Doctor

Publications

Publications (589)
Article
Background: Previous studies suggest that the mechanisms and outcomes in COVID-19-associated stroke differ from those with non-COVID-19 strokes, but there is limited comparative evidence focusing on these populations. Therefore, we aimed to determine if a significant association exists between COVID-19 status with revascularization and functional...
Article
Background: Intravenous thrombolysis with alteplase bolus followed by infusion is a global standard of care for patients with acute ischaemic stroke. We aimed to determine whether tenecteplase given as a single bolus might increase reperfusion compared with this standard of care. Methods: In this multicentre, open-label, parallel-group, registry...
Article
Background- The CHANCE-2 study compared three weeks of aspirin-ticagrelor to aspirin-clopidogrel in CYP2C19 loss-of-function (LOF) allele carriers following a TIA/minor stroke and demonstrated a modestly lower risk of stroke recurrence with aspirin-ticagrelor. This stroke protection was largely for minor stroke and came at an increased risk of blee...
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BACKGROUND Although the association between cortical venous opacification (VO) and clinical outcomes has been shown in previous studies, little is known about the relationship between parenchymal hemorrhage (PH) and VO in patients with acute stroke. We aimed to determine whether cortical VO assessed on computed tomography angiography correlates wit...
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PurposeInfarct lesion volume (ILV) may serve as an imaging biomarker for clinical outcomes in the early post-treatment stage in patients with acute ischemic stroke. The aim of this study was to evaluate the inter- and intra-rater reliability of manual segmentation of ILV on follow-up non-contrast CT (NCCT) scans.Methods Fifty patients from the Prov...
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Background: There are uncertainties regarding the optimal management of acutely symptomatic carotid stenosis (“hot carotids”). We sought to explore the approaches of stroke physicians to anti-thrombotic management, imaging, and revascularization in patients with “hot carotids”. Methods: We used a qualitative descriptive methodology to examine decis...
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Purpose CT angiography (CTA) is the imaging standard for large vessel occlusion (LVO) detection in patients with acute ischemic stroke. StrokeSENS LVO is an automated tool that utilizes a machine learning algorithm to identify anterior large vessel occlusions (LVO) on CTA. The aim of this study was to test the algorithm’s performance in LVO detecti...
Article
The AcT trial (Alteplase Compared to Tenecteplase) compares alteplase or tenecteplase for patients with acute ischemic stroke. All eligible patients are enrolled by deferral of consent. Although the use of deferral of consent in the AcT trial meets the requirements of Canadian policy, we sought to provide a more explicit and rigorous approach to th...
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Introduction: This study aimed to develop and validate a 3-year dementia risk score in individuals with mild cognitive impairment (MCI) based on variables collected in routine clinical care. Methods: The prediction score was trained and developed using data from the National Alzheimer's Coordinating Center (NACC). Selection criteria included age...
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Background : Intravenous thrombolysis with alteplase is widely used in acute ischemic stroke patients presenting early after symptom onset. Recent phase II trials have suggested that intravenous tenecteplase may be safer and associated with higher early reperfusion rates as compared to alteplase. This study investigates whether intravenous tenectep...
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PurposeMedium vessel occlusions (MeVOs) can be challenging to detect on imaging. Multiphase computed tomography angiography (mCTA) has been shown to improve large vessel occlusion (LVO) detection and endovascular treatment (EVT) selection. The aims of this study were to determine if mCTA-derived tissue maps can (1) accurately detect MeVOs and (2) p...
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PurposeCortical vein opacification is not routinely assessed in patients presenting with acute ischemic stroke (AIS), and the value of temporal assessment of venous outflow is not known. We evaluated the utility of assessing cortical venous drainage over time using multiphase CT angiography (mCTA).Methods Cortical venous drainage was assessed in pa...
Article
Background: Cerebral edema after large hemispheric infarction is associated with poor functional outcome and mortality. Net water uptake (NWU) quantifies the degree of hypoattenuation on unenhanced-computed tomography (CT) and is increasingly used to measure cerebral edema in stroke research. Hemorrhagic transformation and parenchymal contrast sta...
Article
Background: Cervico-cephalic arterial dissections (CeAD) are an important cause of stroke in young patients. This study aimed to determine the frequency and predictors of recanalization in spontaneous CeAD and to study the effect of recanalization on functional outcomes. Methods: We identified patients presenting with acute ischemic stroke secon...
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Importance: Tenecteplase is being evaluated as an alternative thrombolytic agent for the treatment of acute ischemic stroke (AIS) within ongoing randomized clinical trials (RCTs). In addition, nonrandomized clinical experiences with off-label use of tenecteplase vs alteplase for AIS treatment are being published. Objective: To evaluate the avail...
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BACKGROUND In light of evidence from recent trials that endovascular thrombectomy (EVT) alone may potentially be noninferior to combined treatment, that is, with intravenous thrombolysis (IVT) with alteplase and EVT, we sought to understand physician and patient preferences around this issue. METHODS We conducted a 2‐stage mixed methods study that...
Article
Background: The mechanisms and outcomes in coronavirus disease (COVID-19)-associated stroke are unique from those of non-COVID-19 stroke. Objective: To describe the efficacy and outcomes of acute revascularization of large vessel occlusion (LVO) in the setting of COVID-19 in an international cohort. Methods: We conducted an international multi...
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Objective: To explore the utility of Tmax-based target mismatch on CT perfusion (CTP) in predicting radiological and clinical outcomes in acute ischemic stroke (AIS) patients with anterior circulation large vessel occlusion (LVO) selected for endovascular treatment (EVT). Methods: AIS patients underwent CTP within 24 hours from onset followed by...
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Background Strokes are a longstanding complication of acute type A aortic dissection (ATAAD) repair. Understanding the neuroanatomy, mechanism, and severity of stroke will facilitate efforts to improve prediction, prevention, and treatment strategies. Methods Retrospective review of patients who sustained stroke from a consecutive series of patien...
Article
Background: Trials’ data are increasingly re-analyzed to identify treatment effect heterogeneity: that is, subgroups of patients who have either enhanced or adverse effects in a trial. This study investigates the robustness of subgroup identification methods in an acute stroke trial. Methods and Analysis: The Model-based recursive partitioning (MOB...
Article
Background: Maternal and newborn stroke occur during the same period when physiological and anatomic connections between mother and infant may provide a rationale for common pathogenetic mechanisms. The similarities and differences between maternal and newborn stroke remain poorly understood. We created the International Maternal Newborn Stroke Reg...
Article
Introduction: Embolic stroke of undetermined source (ESUS) comprises a heterogenous group. There is a need to further identify etiologies within this group to guide management strategies. We examined the prevalence of aortic arch atherosclerosis (AAA) in ESUS patients on CT angiography (CTA) to characterize high-risk plaque features. Methods: All p...
Article
Introduction: Leptomeningeal collaterals help maintain cerebral perfusion after the large vessel occlusion (LVO), potentially regulated by systemic blood pressure (BP). We hypothesized that the association between BP and endovascular treatment (EVT) outcomes would differ by the baseline perfusions status and before and after recanalization. Method:...
Article
Background: Efficient healthcare workflow leads to faster reperfusion and better functional outcomes of stroke in the early-time window. We investigated the impact of care delays on the outcomes of stroke patients treated with endovascular thrombectomy (EVT) in the late window. Methods: Pooled data from seven randomized clinical trials and registri...
Article
Purpose: To validate the performance of a 3D convolutional neural network (CNN) based algorithm i.e. Stroke SENS LVO, in automatically detecting the presence of large vessel occlusions (LVO) on computed tomography angiography (CTA) images of the head. Method: A total of 400 studies (217 LVO, 183 non-LVO) were used in the analysis. The LVO group inc...
Article
Background: In acute ischemic stroke (AIS), Computed Tomography Perfusion (CT, CTP) is the most widely used technique for determining extent of tissue likely to die even after successful reperfusion. However, CTP results in higher radiation dose to the patient, is affected by motion, and is not widely available. Multiphase CT Angiography (mCTA), by...
Article
Background and Purpose: Tenecteplase is being evaluated as an alternative intravenous (IV) thrombolytic agent for the treatment of acute ischemic stroke (AIS) within ongoing randomized controlled clinical trials. However, several research teams have published their real-world experience with tenecteplase for the treatment of AIS. Methods: We search...
Poster
Background: Atrial fibrillation (AF) is a common cause of ischemic stroke; however, it is often difficult to detect. It is unclear whether specific infarct topography on magnetic resonance imaging (MRI) is associated with underlying AF. We aimed to objectively assess the infarct patterns on MRI in patients with acute ischemic stroke and determine i...
Article
Introduction: Outcome prediction tools for large vessel occlusion (LVO) stroke patients receiving endovascular treatment (EVT) focus on patients treated within 6h from onset. We aimed to apply a validated tool to EVT-treated patients in the late window (beyond 6h from onset) and to investigate any outcome differences according to the imaging paradi...
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Mechanical thrombectomy (MT) is the most effective treatment for selected patients with an acute ischemic stroke due to emergent large vessel occlusions (LVOs). There is an urgent need to identify and address challenges in access to MT to maximize the numbers of patients who can benefit from this treatment. Barriers in access to MT include delays i...
Article
Objective: Delayed neointima formation over a neurovascular stent is associated with thrombotic complications that can lead to stroke. The purpose of this study was to evaluate whether an intra-arterial injection of mesenchymal stem cells (MSCs) after stent placement leads to improved neointima and reduced thrombus formation over the device. Meth...
Article
Background and purpose Collateral assessment using CT angiography is a promising modality for selecting patients for endovascular thrombectomy (EVT) in the late window (6–24 hours). The outcome of these patients compared with those selected using perfusion imaging is not clear. Methods We pooled data from seven trials and registries of EVT-treated...
Article
Background To analyse the clinical characteristics of COVID-19 with acute ischaemic stroke (AIS) and identify factors predicting functional outcome. Methods Multicentre retrospective cohort study of COVID-19 patients with AIS who presented to 30 stroke centres in the USA and Canada between 14 March and 30 August 2020. The primary endpoint was poor...
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Background Successful reperfusion determines the treatment effect of endovascular thrombectomy. We evaluated stent-retriever characteristics and their relation to reperfusion in the ESCAPE-NA1 trial. Methods Independent re-scoring of reperfusion grade for each attempt was conducted. The following characteristics were evaluated: stent-retriever len...
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Background and purpose: Sex-related differences exist in many aspects of acute stroke and were mainly investigated in the early time window with conflicting results. However, data regarding sex disparities in late presenters are scarce. Therefore, we sought to investigate differences in outcomes between women and men treated with endovascular trea...
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Background Evidence informing the choice between carotid endarterectomy and carotid artery stenting for acutely symptomatic carotid stenosis (“hot carotid”) is dated and does not factor in contemporary therapies or techniques. The optimal imaging modality is also uncertain. We explored the attitudes of stroke physicians regarding imaging and revasc...
Article
Background and purpose: Accurate and reliable detection of medium-vessel occlusions is important to establish the diagnosis of acute ischemic stroke and initiate appropriate treatment with intravenous thrombolysis or endovascular thrombectomy. However, medium-vessel occlusions are often challenging to detect, especially for unexperienced readers....
Article
BACKGROUND Statistical models to predict outcomes after endovascular therapy for acute ischemic stroke often incorporate baseline (pretreatment) variables only. We assessed the performance of stroke outcome prediction models for endovascular therapy in stroke in an iterative fashion using baseline, treatment‐related, and posttreatment variables. M...
Article
Background and Objectives New imaging techniques have advanced our ability to capture thrombus characteristics and burden in real time. An improved understanding of recanalization rates with thrombolysis and endovascular thrombectomy based on thrombus characteristics has spurred interest in new therapies for acute stroke. Methods and Results This...
Article
Background and Purpose Early neurological deterioration occurs in one-third of mild strokes primarily due to the presence of a relevant intracranial occlusion. We studied vascular occlusive patterns, thrombus characteristics, and recanalization rates in these patients. Methods Among patients enrolled in INTERRSeCT (Identifying New Approaches to Op...
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Importance Some patients have poor outcomes despite small infarcts after endovascular therapy (EVT), while others with large infarcts do well. Understanding why these discrepancies occur may help to optimize EVT outcomes. Objective To validate exploratory findings from the Endovascular Treatment for Small Core and Anterior Circulation Proximal Occ...
Article
Background The DAWN and DEFUSE-3 trials showed the benefit of endovascular treatment (EVT) in acute ischemic stroke patients presenting beyond 6 hours from last known well (LKW) and selected by perfusion imaging criteria. The ESCAPE NA1-trial selected patients based on non-contrast CT (NCCT) Alberta Stroke Program Early CT Score (ASPECTS) and multi...
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Background and purposeEndovascular treatment (EVT) is a powerful treatment for large vessel occlusion (LVO) stroke if reperfusion can be achieved, while in cases with failed reperfusion, EVT may cause harm, as procedure-related complications may occur. We hypothesized that EVT with failed recanalization does not result in worse outcomes compared to...
Article
Background Trials examining the benefit of thrombectomy in anterior circulation proximal large vessel occlusion stroke have enrolled patients considered to have salvageable brain tissue, who were randomly assigned beyond 6 h and (depending on study protocol) up to 24 h from time last seen well. We aimed to estimate the benefit of thrombectomy overa...
Article
Identifying the presence and extent of early ischemic changes (EIC) on Non-Contrast Computed Tomography (NCCT) is key to diagnosing and making time-sensitive treatment decisions in patients that present with Acute Ischemic Stroke (AIS). Segmenting EIC on NCCT is however a challenging task. In this study, we investigated a 3D CNN based on nnU-Net, a...
Article
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Background: Patients with acutely symptomatic carotid stenosis (“hot carotid”) have high up-front risk of recurrent strokes. Uncertainties remain regarding optimal anti-thrombotic management, particularly while awaiting revascularization with endarterectomy or stenting (CEA/CAS). Methods: We administered a worldwide electronic survey through Neurol...
Article
Background: Thrombus embolization during endovascular treatment (EVT) occurs in up to 9% of cases, making secondary medium-vessel occlusions (MeVOs) of particular interest to neurointerventionalists. We sought to gain insight into the current EVT approaches for secondary MeVO stroke in an international case-based survey as there are currently no cl...
Article
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Background: Whereas the beneficial effect of antiplatelet therapy for recurrent stroke prevention is well-established, uncertainties remain regarding the optimal anti-thrombotic regimen for acutely symptomatic carotid stenosis (“hot carotid”), particularly as patients await revascularization. We sought to explore the approaches of stroke physicians...
Article
Full-text available
Background: Some patients do poorly despite small infarcts after endovascular therapy(EVT) whilst others with large infarcts do well. We validated exploratory findings from the ESCAPE trial regarding factors associated with such discrepancies, in the ESCAPE-NA1 trial(NCT02930018). Methods: We identified “discrepant cases” with modified Rankin Scale...
Article
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Background: Decisions to treat large-vessel occlusion with endovascular therapy(EVT) or intravenous alteplase depend on how physicians weigh benefits against risks when considering patients’ pre-stroke comorbidities. Methods: In an international survey, experts chose treatment approaches under current resources and under assumed ideal conditions fo...
Article
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Background: Evidence informing the choice between endarterectomy and stenting for acutely symptomatic carotid stenosis (“hot carotid”) is dated, and uncertainties remain regarding the optimal imaging modality. We sought to explore the thoughts of stroke physicians regarding the perioperative management of patients with acute symptomatic carotid ste...
Article
Full-text available
Background: Predicting outcomes after endovascular treatment (EVT) for acute ischemic stroke with baseline variables remains a challenge. We assessed the performance of stroke outcome prediction models for EVT in acute ischemic stroke in an iterative fashion using baseline, treatment-related and post-treatment variables. Methods: Data from the ESCA...
Article
Full-text available
Background and purpose: Thrombus embolization during mechanical thrombectomy occurs in up to 9% of cases, making secondary medium vessel occlusions of particular interest to neurointerventionalists. We sought to gain insight into the current endovascular treatment approaches for secondary medium vessel occlusion stroke in an international case-bas...
Article
Full-text available
Recombinant tissue plasminogen activator improves outcomes in acute ischemic stroke. Alteplase may result in thrombus migration distally to a critical arterial supply that can worsen perfusion to eloquent brain tissue. Alteplase related stroke recanalization and clot migration in vertebral artery occlusion whereby the clot migrates to the basilar a...
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The hyperdense sign is a marker of thrombus in non-contrast computed tomography (NCCT) datasets. The aim of this work was to determine optimal Hounsfield unit (HU) thresholds for thrombus segmentation in thin-slice non-contrast CT (NCCT) and use these thresholds to generate 3D thrombus models. Patients with thin-slice baseline NCCT (≤2.5 mm) and MC...
Article
Full-text available
Endovascular therapy (EVT) is an effective treatment for ischemic stroke due to large vessel occlusion (LVO). Unlike intravenous thrombolysis, EVT enables visualization of the restoration of blood flow, also known as successful reperfusion in real time. However, until successful reperfusion is achieved, the survival of the ischemic brain is mainly...
Article
Background and purpose: Various imaging paradigms are used for endovascular treatment (EVT) decision-making and outcome estimation in acute ischemic stroke (AIS). We aim to compare how these imaging paradigms perform for EVT patient selection and outcome estimation. Methods: Prospective multi-center cohort study of patients with AIS symptoms wit...
Article
Background: Collateral status is an indicator of favorable outcome in stroke. Leptomeningeal collaterals provide alternative routes for brain perfusion following an arterial occlusion or flow-limiting stenosis. Using a large cohort of ischemic stroke patients, we examined the relative contribution of various demographic, laboratory and clinical var...
Article
Background Determining infarct progression rate in acute ischemic stroke (AIS) is important for patient triage, treatment decision-making, and outcome prognostication. Objective To estimate infarct progression rate in patients with AIS with large vessel occlusion (LVO) and determine its predictors and impact on clinical outcome. Methods Data are...
Article
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Background: Multiphase CTA (mCTA) is an established tool for endovascular treatment decision-making and outcome prediction in acute ischemic stroke, but its interpretation requires some degree of experience. We aimed to determine whether mCTA-based prediction of clinical outcome and final infarct volume can be improved by assessing collateral stat...
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PurposeThere are few data on the prevalence and impact of isolated deep grey matter infarction in acute stroke. In this study, we aimed to investigate the prevalence of isolated deep grey matter infarcts and their impact on the outcome.Methods Infarcts on 24-h follow-up imaging (non-contrast head CT or diffusion-weighted MRI) in the ESCAPE-NA1 tria...
Article
Background and purpose: Patients with acute ischemic stroke due to medium vessel occlusion (MeVO) make up a substantial part of the acute stroke population, though guidelines currently do not recommend endovascular treatment (EVT) for them. A growing body of evidence suggests that EVT is effective in MeVOs, including observational data but no rand...
Article
Full-text available
Background and Purpose Whether reperfusion into infarcted tissue exacerbates cerebral edema has treatment implications in patients presenting with extensive irreversible injury. We investigated the effects of endovascular thrombectomy and reperfusion on cerebral edema in patients presenting with radiological evidence of large hemispheric infarction...
Conference Paper
Background Medium-vessel occlusions (MeVOs) account for 25%-40% of all acute ischemic stroke (AIS) cases. With peri-procedural embolization occurring in up to 9% of all EVT cases, secondary MeVOs are of particular interest to neurointerventionalists. There is currently no reliable evidence regarding whether EVT is safe and effective for MeVO stroke...
Conference Paper
Full-text available
Background Medium-vessel occlusions (MeVOs) are the second most frequent cause of acute ischemic stroke (AIS) and patients often have poor clinical outcome if treated with best medical management alone. Alteplase recanalization rates have been shown to range from 21-43% in primary (de-novo occurring) MeVOs, indicating a need for a more effective th...
Conference Paper
Full-text available
Background Collateral assessment using CT angiography (CTA) is promising to increase the eligibility for endovascular thrombectomy (EVT) in the late window (6–24 hours). The outcome of these patients compared to those selected using perfusion imaging is not clear. We aimed to describe the outcomes of EVT in patients selected using collateral vs per...