Mohammed A Almekhlafi

The University of Calgary | HBI · Department of Clinical Neurosciences

Selective brain cooling is a promising advent for reducing final infarct volume and improving outcomes in ischemic stroke victims. Despite the robust body of evidence from animal studies, evidence supporting the use of selective hypothermia in stroke patients is lacking. A recent study provided promising results on the safety and possible efficacy...

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...

We report chronic histopathological features in thrombi mechanically retrieved from five acute ischemic stroke patients with a median age of 68 years and a median pretreatment National Institutes of Health Stroke Scale score of 13. Early endothelialization occurred over and within the thrombus, and calcifications were seen, in addition to the usual...

Background and Purpose— The benefit that endovascular thrombectomy offers to patients with stroke with large vessel occlusions depends strongly on reperfusion grade as defined by the expanded Thrombolysis in Cerebral Infarction (eTICI) scale. Our aim was to determine the lifetime health and cost consequences of the quality of reperfusion for patien...

Background and aims: Recent evidence from thrombolysis trials indicate the non-inferiority of the Tenecteplase (TNK) to the Alteplase (TPA) with respect to functional outcomes in acute stroke patients. This study examines the predictors of patient-reported health-related quality of life (HRQOL) in acute stroke patients who received thrombolysis the...

Background: Understanding clot composition may allow for better technical planning and improved outcomes in mechanical thrombectomy (MT). We sought to correlate clot composition with reperfusion outcomes in MT. Methods: Clinical, imaging, and clot data from patients enrolled in the STRIP Registry from September 2016 to September 2020 were analyzed....

Introduction: Brain-selective hypothermia is a promising neuroprotectant in acute ischemic stroke. However, a non-invasive bedside method to monitor brain temperature during cooling is lacking. We tested the feasibility and accuracy of measuring brain temperature non-invasively using sensors designed to monitor core body temperature. Methods: In th...

Background: Subgroup analyses are widely used to evaluate heterogeneity of treatment effects in randomized clinical trials. However, there is a limited investigation of the quality of prespecified and reported subgroup analyses in stroke trials. This study evaluated the credibility of subgroup analyses in stroke trials. Methods and Analysis: We sea...

Background The relationship between duration of transient neurological events and presence of diffusion‐weighted lesions by symptom type is unclear. Methods and Results This was a substudy of SpecTRA (Spectrometry for Transient Ischemic Attack Rapid Assessment), a multicenter prospective cohort of patients with minor ischemic cerebrovascular event...

BACKGROUND First‐pass effect (FPE), that is, achieving reperfusion with a single thrombectomy device pass, is associated with better clinical outcomes in patients with acute stroke. FPE is therefore increasingly used as a marker of device and procedural efficacy. We aimed to evaluate the ability of thrombus‐based radiomics models to predict FPE in...

Introduction: Distal embolization (DE) is a common complication of endovascular treatment (EVT). We aimed to investigate the association of radiological thrombus characteristics and treatment details with distal embolization (DE). Methods: Patients with thin-slice (≤2.5 mm) baseline non-contrast CT and CT-angiography from the ESCAPE-NA1 trial (Eff...

Background Intravenous thrombolysis with alteplase is widely used in patients with acute ischemic stroke 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 with alteplase. This study investigates whether intravenous ten...

Introduction It remains unclear whether incomplete reperfusion caused by multiple small occlusions or slow flow after mechanical thrombectomy (MT) results in infarction on follow-up imaging.¹ Aim We investigated whether small peripheral thrombi or slow flow was associated with infarction on follow-up scan. Methods Patients from the ESCAPE-NA1 tri...

Introduction The degree of mTICI 2b reperfusion varies from 51%-89% in acute stroke patients treated with mechanical thrombectomy(MT)¹. Incomplete reperfusion could be due to either focal occlusion (residual thrombus, fragmented/migrated thrombus) or slow flow². With advancing endovascular techniques, residual distal/medium vessel occlusions can be...

Selective therapeutic hypothermia in the setting of mechanical thrombectomy (MT) is promising to further improve the outcomes of large vessel occlusion stroke. A significant limitation in applying hypothermia in this setting is the lack of real-time non-invasive brain temperature monitoring mechanism. Non-invasive brain temperature monitoring would...

Background and purpose There is much uncertainty in endovascular treatment (EVT) decisions in patients with acute large vessel occlusion (LVO) and mild neurological deficits. Methods From a prospective, nationwide stroke registry, all patients with LVO and baseline NIHSS <6 presenting within 24 h from the time last known well (LKW) were included....

Background The benefit of endovascular thrombectomy (EVT) in stroke patients with a low baseline Alberta Stroke Program Early CT Score (ASPECTS, ≤5) is uncertain. We aim to use random forest regression modeling to predict 90 day home time in patients with low ASPECTS. Methods We used the Quality Improvement and Clinical Research (QuICR) provincial...

Background Endovascular treatment (EVT) for stroke due to medium vessel occlusion (MeVO) can be technically challenging and specific endovascular tools are needed to safely and effectively recanalize these relatively small and fragile vessels. We aimed to gain insight into availability and desired qualities of endovascular devices used in MeVO stro...

Introduction Delays have a negative impact on successful reperfusion with endovascular thrombectomy (EVT) in early-window strokes. Late window patients may be further disadvantaged due to their late presentation. We assessed the impact of delays on reperfusion success in late window stroke patients. Materials and Methods We pooled data from seven...

Background and Purpose Radial arterial access has been shown to improve overall safety in patients undergoing angiography and endovascular therapy. This approach, widely adopted in Cardiology, has recently also been validated for neuroendovascular procedures. Distal trans-radial access via the anatomical snuffbox is a further refinement of this tec...

Background Endovascular treatment (EVT) for stroke due to medium vessel occlusion (MeVO) can be technically challenging and specific endovascular tools are needed to safely and effectively recanalize these relatively small and fragile vessels. We aimed to gain insight into availability and desired qualities of endovascular devices used in MeVO stro...

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...

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...

Background: Trials of endovascular thrombectomy (EVT) for acute stroke have excluded patients with pre-morbid disability. We performed a meta-analysis to assess the effectiveness and safety of EVT in patients with pre-morbid disability. Methods: According to PRISMA guidelines, we searched for studies describing outcomes in patients with pre-morbid...

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...

Background: Platelets and von Willebrand factor (vWF) are key components of acute ischemic stroke (AIS) emboli. We aimed to investigate the CD42b (platelets)/vWF expression, its association with stroke etiology and the impact these components may have on the clinical/procedural parameters. Methods: CD42b/vWF immunostaining was performed on 288 e...

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...

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...

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...

Intracerebral hemorrhage (ICH) accounts for 10–15% of all strokes and leaves most survivors with impairments. Fever, a rise in the thermoregulatory set point, complicates ICH. This review summarizes ICH fever studies and employs meta-analytic techniques to explore the relationship between fever and ICH. We discuss methodological considerations for...

Background and purpose Given recent evidence suggesting the clot composition may be associated with revascularization outcomes and stroke etiology, clot composition research has been a topic of growing interest. It is currently unclear what effect, if any, pre-thrombectomy thrombolysis has on clot composition. Understanding this association is impo...

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...

Background Trials of endovascular thrombectomy (EVT) for acute stroke have excluded patients with pre-morbid disability. Observational studies may help inform consideration of EVT in this population. We aimed to assess the effectiveness and safety of EVT in patients with pre-morbid disability. Methods According to Preferred Reporting Items for Sys...

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...

Purpose The clinical significance of iatrogenic diffusion-weighted imaging lesions following endovascular procedures is currently not well understood, partly because they do not result in immediate clinical deficits (“silent brain infarcts” [SBI]) and often remain undiagnosed. Conversely, access site complications are well-documented. With the SILE...

Background and purpose: There are limited data on the prevalence and outcome of intracranial atherosclerotic disease in patients with low-risk transient or persistent minor neurologic events. We sought to determine the prevalence and risk factors associated with intracranial atherosclerotic disease in patients with low-risk transient or persistent...

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...

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...

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:...

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...

Background: The outcome in stroke patients with ASPECTS of ≤5 who undergo Endovascular Thrombectomy(EVT) in Large Vessel Occlusion (LVO) is uncertain. We used machine learning models to predict 90-day home-time in these patients. Methods: We used the QuICR provincial stroke registry and administrative data from Southern Alberta to identify patients...

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...

Background and Purpose: Sex-related differences exist in many aspects of 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 treatment (...

Background: 90-day home-time, the number of days a patient is back at their premorbid living situation without an increase in level of care in the first 90 days post stroke, is routinely collected in administrative data. We evaluated the prediction of 90-day home-time using machine learning modelling in patients undergoing endovascular treatment (E...

Introduction: First-pass effect (FPE), i.e., achieving reperfusion with a single thrombectomy device pass, is associated with better clinical outcomes in patients with acute stroke. FPE is therefore increasingly being used as a marker of device and procedural efficacy. We evaluated the ability of thrombus-based radiomics models to predict FPE in pa...

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...

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...

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...

Background Compositional and structural features of retrieved clots by thrombectomy can provide insight into improving the endovascular treatment of ischemic stroke. Currently, histological analysis is limited to quantification of compositions and qualitative description of the clot structure. We hypothesized that heterogeneous clots would be prone...

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...

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...

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...

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...

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...

Background: Stroke is the second leading cause of death and a major cause of serious, long-term disability worldwide. The approximately 15 million people each year who experience stroke are at risk of developing depression. Poststroke depressive symptoms affect one third of survivors of stroke. Patients who develop poststroke depressive symptoms e...

Introduction: The optimal anaesthesia approach for endovascular treatment (EVT) in acute ischaemic stroke is currently unknown. In stroke due to medium vessel occlusions (MeVO), the occluded vessels are particularly small and more difficult to access, especially in restless or uncooperative patients. In these patients, general anaesthesia (GA) may...

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...

Background: Endovascular treatment (EVT) for stroke due to medium vessel occlusion (MeVO) can be technically challenging. Devices and tools are rapidly evolving. We aimed to gain insight into preferences and global perspectives on the usage of endovascular tools in treating MeVOs. Methods: We conducted an international survey with seven scenarios o...

Therapeutic hypothermia (TH) has applications dating back millennia. In modern history, however, TH saw its importation into medical practice where investigations have demonstrated that TH is efficacious in ischemic insults, notably cardiac arrest and hypoxic-ischemic encephalopathy. As well, studies have been undertaken to investigate whether TH c...

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...

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...

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...

Intra-carotid cold infusion (ICCI) appears as a promising method for hypothermia-mediated brain protection from ischemic stroke. Recent clinical pilot studies indicate easy implementation of ICCI into endovascular acute ischemic stroke treatment. Current rodent ICCI-in-stroke models limit ICCI to the post-reperfusion phase. To establish a method fo...

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...

Background Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disab...