Ronen Leker

• Professor
• Director Stroke Unit at Hadassah Medical Center

Background and Aims: Cervical arterial dissections (CeAD) are a common cause of stroke in young adults across both sexes. Whether biological sex plays a role in the pathogenesis and outcome of CeAD remains unclear. Methods: In this retrospective analysis of a cohort of patients with CeAD, clinical, imaging, treatment, and outcome data were compared...

Background Imaging biomarkers obtained on computed tomography perfusion (CTP) have proven effective in predicting outcomes after endovascular thrombectomy (EVT) in patients with large vessel occlusion stroke. However, the association of CTP imaging biomarkers with outcomes in medium-size vessel occlusion (MeVO) stroke patients remains unknown. Obj...

Background Acute symptomatic seizures (ASYS) is a common presentation in cerebral sinus venous thrombosis (CSVT) patients. Objectives We aimed to characterize CSVT patients experiencing ASYS within 7 days from presentation. Additionaly, we aimed to find predictors for ASYS within CSVT patients. Methods Prospective CSVT databases from six academic...

BACKGROUND Patients presenting with cervical artery dissection (CAD) are at risk for subsequent ischemic events. We aimed to identify characteristics that are associated with increased risk of ischemic stroke after initial presentation of CAD and to evaluate the differential impact of anticoagulant versus antiplatelet therapy in these high-risk ind...

Background: There is an unmet need for high-quality data from prospective studies on the safety and effectiveness of direct oral anticoagulants (DOACs) for the treatment of cerebral venous thrombosis (CVT). We aimed to compare the safety and effectiveness of DOACs versus vitamin K antagonists (VKAs) for the treatment of CVT in a setting that reflec...

Background/Objectives: Previously undiagnosed atrial fibrillation (PUAF) is a significant cause of embolic stroke of undetermined source (ESUS). This study aimed to determine whether early heart rhythm monitoring with a Holter ECG after acute stroke enhances the detection of PUAF compared to standard ambulatory monitoring in ESUS patients, assuming...

Introduction Evidence regarding the benefit of endovascular therapy (EVT) in patients with acute ischemic stroke (AIS) due to isolated cervical internal carotid artery occlusion (c-ICA-O) is lacking. We assessed the outcomes and safety of EVT in patients with isolated c-ICA-O. Methods Retrospective multicenter cohort study of patients with an AIS...

Background: Endovascular treatment (EVT) of stroke with large-vessel occlusion is known to be safe and effective. The effect of EVT for occlusion of medium or distal vessels is unclear. Methods: We randomly assigned participants with an isolated occlusion of medium or distal vessels (occlusion of the nondominant or codominant M2 segment of the m...

Background: Cervical artery dissection (CAD) is a leading cause of stroke in young adults, accounting for up to 25% of strokes in this population. Despite its prevalence, there is considerable variability in the management of CAD due to the lack of large-scale randomized trials and inconsistent findings in existing literature. This study aims to as...

Introduction: In patients with large vessel occlusion stroke of the anterior circulation who are treated with mechanical thrombectomy (MT) and intravenous thrombolysis (IVT), there is no clear evidence that prior antiplatelet therapy (APT) significantly influences functional outcomes, successful reperfusion rates or the risk of symptomatic intracra...

Background: The optimal endovascular management of cervical carotid dissection causing tandem occlusion remains uncertain. We investigated the impact of emergent carotid stenting during endovascular treatment (EVT) for acute ischemic stroke (AIS) in patients with tandem occlusion secondary to cervical carotid artery dissection. Methods: This was a...

Background and aims Previous observational data indicate that young adults treated with intravenous thrombolysis (IVT) for acute ischemic stroke have more favorable outcomes and less complications when compared to older adults. Given the limited data on this topic, we aimed to provide more evidence on clinical outcomes and safety in such patients,...

Background Acute intracranial occlusion of the internal carotid artery (ICA) can be distinguished into (a) occlusion of the terminal ICA, involving the proximal segments of the middle or anterior cerebral artery (ICA-L/-T) and (b) non-terminal intracranial occlusions of the ICA with patent circle of Willis (ICA-I). While patients with ICA-L/-T occl...

Importance One of 10 patients develop epilepsy in the late phase after cerebral venous thrombosis (CVT) diagnosis but predicting the individual risk is difficult. Objective To develop and externally validate a prognostic score to estimate the individual risk of post-CVT epilepsy. Design, Setting, and Participants This observational cohort study i...

Objectives: Cervical artery dissection (CeAD) accounts for 25% of ischemic strokes in young adults. This study evaluated the benefits and harms of intravenous thrombolysis (IVT) in patients presenting with spontaneous CeAD and acute ischemic stroke symptoms. Methods: This analysis used data from the retrospective STOP-CAD study and included pati...

Introduction After positive findings in clinical trials the time window for endovascular thrombectomy (EVT) for patients with an acute ischemic stroke has been expanded up to 24 h from symptom onset or last seen well (LSW). We aimed to compare EVT patients’ characteristics and outcomes in the early versus extended time window and to compare outcome...

Objective Patients with cervical artery dissection (CAD) are at increased ischemic stroke risk. We aimed to identify characteristics that are associated with increased risk of ischemic stroke following initial presentation of CAD and to evaluate the differential impact of anticoagulant versus antiplatelet therapy in these high-risk individuals. Me...

(1) Background: Cervical arterial dissections (CeAD) are a common cause of stroke in young adults. CeAD can be spontaneous (sCeAD) or traumatic (tCeAD). Whether CeAD subtypes differ in clinical, radiological, and outcome characteristics remains unexplored. (2) Methods: Patients with CeAD were identified and divided between sCeAD and tCeAD. Demograp...

Importance Whether infarct size modifies the treatment effect of early vs late direct oral anticoagulant (DOAC) initiation in people with ischemic stroke and atrial fibrillation is unknown. Objective To assess whether infarct size modifies the safety and efficacy of early vs late DOAC initiation. Design, Setting, and Participants Post hoc analysi...

Background Information regarding the safety and efficacy of specific direct oral anticoagulants (DOAC) in the treatment of cerebral sinus and venous thrombosis (CSVT) is scarce. Apixaban is one of the most frequently prescribed DOACs. Therefore, we aimed to compare the safety and efficacy of Apixaban with those of vitamin k antagonists (VKA) in pat...

Rationale Whether endovascular therapy (EVT) in addition to best medical treatment (BMT) in people with acute ischemic stroke (AIS) due to a medium distal vessel occlusion (MDVO) is beneficial remains unclear. Aim To determine if people experiencing an AIS due to an isolated MDVO (defined as the co- or non-dominant M2 segment, the M3 or M4 segment...

Background: Due to the rarity of cerebral venous thrombosis (CVT), performing high-quality scientific research in this field is challenging. Providing answers to unresolved research questions will improve prevention, diagnosis, and treatment, and ultimately translate to a better outcome of patients with CVT. We present an international research age...

BACKGROUND Small, randomized trials of patients with cervical artery dissection showed conflicting results regarding optimal stroke prevention strategies. We aimed to compare outcomes in patients with cervical artery dissection treated with antiplatelets versus anticoagulation. METHODS This is a multicenter observational retrospective internationa...

(1) Background: The mechanism responsible for stroke in patients younger than 50 often remains unknown. This study was designed to assess whether high-resolution intracranial vessel wall MR imaging (icVWI) may be instrumental in determining stroke cause. (2) Methods: Young stroke patients with and without an identified cause of stroke despite an ex...

Background The role of intravenous thrombolysis (IVT) as bridging treatment prior to endovascular thrombectomy (EVT) is under debate and better patient selection is needed. Objectives As the efficacy and safety of IVT diminish with time, we aimed to examine the impact of bridging treatment within different time frames from symptom onset. Design A...

We present our experience with the implantation of flow diverter stents (FDSs) for the management of internal carotid artery (ICA) dissections in tortuous tonsillar loop segments. A total of 16 patients (10 women, 62.5%; mean age 39 ± 8 years; median baseline NIHSS 13; median ASPECTS 8.5) with acute ischemic stroke due to ICA dissection in a tortuo...

Introduction Current guidelines recommend that patients with cerebral venous thrombosis (CVT) should be treated with vitamin K antagonists (VKAs) for 3–12 months. Direct oral anticoagulants (DOACs), however, are increasingly used in clinical practice. An exploratory randomized controlled trial including 120 patients with CVT suggested that the effi...

BACKGROUND: AND OBJECTIVES Intravenous thrombolysis (IVT) for suspected ischemic stroke in patients with intracranial neoplasms is off-label. However, data on risks of intracranial hemorrhage (ICH) is scarce. METHODS In a multicenter registry-based analysis within the European Thrombolysis in Ischemic Stroke Patients (TRISP) collaboration, we asse...

Background: Large vessel occlusions (LVO) stroke is associated with cancer. Whether this association differs among patients with LVO that undergo endovascular thrombectomy (EVT) according to cancer type remains unknown. Patients and methods: Data from consecutive patients that underwent EVT for LVO at three academic centers were pulled and analy...

Background and objectives: Intravenous thrombolysis (IVT) for suspected ischemic stroke in patients with intracranial neoplasms is off-label. However, data on risks of intracranial hemorrhage (ICH) is scarce. Methods: In a multicenter registry-based analysis within the European Thrombolysis in Ischemic Stroke Patients (TRISP) collaboration, we a...

Background: Direct oral anticoagulants (DOAC) are advocated as equally effective to vitamin K antagonists (VKA) for the treatment of patients with cerebral sinus and venous thrombosis (CSVT). However, data concerning the real-life management practices in CSVT patients are is lacking. Methods: Prospective CSVT databases from four large academic m...

Background Cancer is associated with an increased risk of acute ischemic stroke, including large vessel occlusions. Whether cancer status affects outcomes in patients with large vessel occlusions that undergo endovascular thrombectomy remains unknown. Methods and Results All consecutive patients undergoing endovascular thrombectomy for large vesse...

Background Retinal artery occlusion (RAO) may lead to irreversible blindness. For acute RAO, intravenous thrombolysis (IVT) can be considered as treatment. However, due to the rarity of RAO, data about IVT safety and effectiveness is limited. Methods From the multicenter database ThRombolysis for Ischemic Stroke Patients (TRISP), we retrospectivel...

We present our experience with the implantation of flow diverter stents (FDSs) for the management of intern carotid artery (ICA) dissections in tortuous tonsillar loop segments. 16 patients (10 women, 62.5%; mean age 39±8 years; median baseline NIHSS 13; median ASPECTS 8.5) with acute ischemic stroke due to ICA dissection in a tortuous tonsillar lo...

(1) Background: Multiple acute concomitant cerebral infarcts (MACCI) are relatively uncommon. Data regarding the characteristics and outcomes of patients with MACCI are lacking. We, therefore, aimed to characterize the clinical features of MACCI. (2) Methods: Patients with MACCI were identified from a prospective registry of stroke patients admitte...

Objective To investigate the safety and effectiveness of intravenous thrombolysis (IVT) >4.5–9 hours after stroke onset, and the relevance of advanced neuroimaging for patient selection. Methods Prospective multicenter cohort study from the ThRombolysis in Ischemic Stroke Patients (TRISP) collaboration. Outcomes were symptomatic intracranial hemor...

Background: We developed a prognostic score to predict dependency and death after cerebral venous thrombosis (CVT) to identify patients for targeted therapy in future clinical trials.. Methods: We used data from the International CVT Consortium. We excluded patients with pre-existent functional dependency. We used logistic regression to predict...

Background: Cancer is associated with an increased risk of acute ischemic stroke (AIS) including large vessel occlusions (LVO). Whether cancer status affects outcomes in patients with LVO that undergo endovascular thrombectomy (EVT) remains unknown. Methods and Results: All consecutive patients undergoing EVT for LVO were recruited into a prospecti...

Objectives. Cerebral sinus venous thrombosis (CSVT) is a rare stroke subtype and data regarding prognostic factors to predict outcomes are lacking. Thus, we aimed to identify predictors for outcome among CSVT patients. Materials and Methods. Prospective CSVT databases from four academic medical centers were retrospectively studied. Demographics, cl...

Importance International guidelines recommend avoiding intravenous thrombolysis (IVT) in patients with ischemic stroke who have a recent intake of a direct oral anticoagulant (DOAC). Objective To determine the risk of symptomatic intracranial hemorrhage (sICH) associated with use of IVT in patients with recent DOAC ingestion. Design, Setting, and...

Introduction We aimed to assess the clinical significance of M1-MCA occlusion with visualization of both MCA-M2 segments [“Tilted-V sign” (TVS)] on initial CT angiography (CTA) in patients with acute ischemic stroke (AIS) undergoing endovascular thrombectomy (EVT). Methods Data for patients with consecutive AIS undergoing EVT for large vessel occl...

Background Patients with stroke secondary to isolated anterior cerebral artery (ACA) occlusions have poor outcomes. Whether tandem occlusions (TO) of the extracranial internal carotid (ICA) and the ACA carry even worse outcomes that remain unknown. Methods Patients with TO involving ICA and ACA occlusions were identified from 14 participating cent...

Background Thrombotic complications including stroke were previously described following Covid-19. We aim to describe the clinical and radiological characteristics of Covid-19 related with acutely symptomatic carotid stenosis (aSCS). Method All patients presenting with an aSCS were prospectively enrolled in an ongoing institutional database. Inclu...

Background: The probability to receive intravenous thrombolysis (IVT) for treatment of acute ischemic stroke declines with increasing age and is consequently the lowest in very elderly patients. Safety concerns likely influence individual IVT treatment decisions. Using data from a large IVT registry, we aimed to provide more evidence on safety of...

Introduction The use of endovascular thrombectomy (EVT) has dramatically increased in recent years. However, most existing studies used an upper age limit of 80 and data regarding the safety and efficacy of EVT among nonagenarians is still lacking. Methods 767 consecutive patients undergoing EVT for large vessel occlusion (LVO) in three participat...

Objectives: Janus kinase 2 (JAK2-V617F) mutations can cause thrombocytosis, polycythemia and hyper viscosity leading to cerebral sinus venous thrombosis (CSVT). However, data regarding the characteristics and prevalence of JAK2-V617F mutation in patients with CSVT are currently lacking. We aimed to evaluate the characteristics of CSVT patients tha...

Current guidelines advocate intravenous thrombolysis (IVT) prior to endovascular thrombectomy (EVT) for all patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO). We evaluated outcomes with and without IVT pretreatment. Our institutional protocols allow AIS patients presenting early (<4 h from onset or last seen normal) who...

Although embolism is the predominant mechanism affecting the middle cerebral artery (MCA), primary atherosclerosis plays a significant role in MCA occlusive disease, especially in African Americans and Asians. Many patients with this disease have recurrent cerebral ischemic events despite standard medical therapy with antiplatelet agents or oral an...

Intracerebral hemorrhages (ICH) characteristics reportedly differ between different ethnic groups. We aimed to compare the characteristics of Jewish and Arab ICH patients in Israel. Consecutive patients with primary ICH were included in a prospective institutional database. Demographics, vascular risk factors, clinical and radiological parameters w...

Purpose: Hemorrhagic transformation (HT) following cerebral endovascular thrombectomy (EVT) for large vessel occlusion (LVO) in acute ischemic stroke is associated with poor outcome. Recent studies have shown that EVT can be efficacious in imaging-selected patients as late as 6-24 h from onset (late time window; LTW). We sought to determine predic...

Background and Purpose The etiology of transient global amnesia (TGA) remains unclear in a large subset of patients. We aimed to determine the clinical and radiological characteristics of TGA-patients with suspected acute micro-embolic stroke on diffusion-weighted imaging (DWI). Methods TGA-patients that had new DWI hippocampal lesions (DWI+) were...

Patients with cerebral venous sinus thrombosis (CVST) occasionally present with intracerebral hemorrhage (ICH). In this study, we aimed to identify predictors for ICH in CVST patients. Prospective CVST databases from three academic centers were retrospectively analyzed. CVST patients with and without ICH upon presentation were compared. Among the 4...

Background Patients with stroke secondary to occlusions of the anterior cerebral artery (ACA) often have poor outcomes. The optimal acute therapeutic intervention for these patients remains unknown. Methods Patients with isolated ACA-stroke were identified from 10 centers participating in the EndoVascular treatment And ThRombolysis in Ischemic Str...

Flow diversion is a promising option in selected patients with acutely ruptured microaneurysms. In this article, we reviewed our experience. Patients with acute spontaneous subarachnoid hemorrhage (SAH) after rupture of a blister-like or saccular microaneurysm (≤2 mm maximal diameter) at a nonbranching ICA site treated from January 2016 to June 201...

Carotid endarterectomy is usually preferred over carotid artery stenting (CAS) for patients with atrial fibrillation (AF). We present our experience with short-course periprocedural triple antithrombotic therapy in 32 patients aged >18 years with nonvalvular AF undergoing CAS. There were no deaths, cardiac events, embolic strokes, hyperperfusion sy...

Importance: Thrombosis with thrombocytopenia syndrome (TTS) has been reported after vaccination with the SARS-CoV-2 vaccines ChAdOx1 nCov-19 (Oxford-AstraZeneca) and Ad26.COV2.S (Janssen/Johnson & Johnson). Objective: To describe the clinical characteristics and outcome of patients with cerebral venous sinus thrombosis (CVST) after SARS-CoV-2 vacc...

Purpose The Thrombolysis in Ischemic Stroke Patients (TRISP) collaboration was a concerted effort initiated in 2010 with the purpose to address relevant research questions about the effectiveness and safety of intravenous thrombolysis (IVT). The collaboration also aims to prospectively collect data on patients undergoing endovascular treatment (EVT...

Introduction: The COVID-19 pandemic overwhelmed health-care systems worldwide, and medical care for other acute diseases was negatively impacted. We aimed to investigate the effect of the COVID-19 outbreak on admission rates and in-hospital care for acute stroke and transient ischemic attack (TIA) in Israel, shortly after the start of the pandemic...

Objectives Cerebral sinus venous thrombosis (CSVT) is a rare stroke subtype that is more common in women, yet data regarding sex‐specific characteristics are sparse. We aimed to study male‐specific characteristics among patients with CSVT. Materials & methods Data of consecutive patients with CSVT, admitted to a single medical centre between 2005...

Purpose: Infarct growth and final infarct volume are established outcome modifiers following endovascular thrombectomy (EVT) for patients with large vessel occlusion stroke (LVO). Simple techniques for final infarct volume measurement are lacking, and therefore, we tested whether post-EVT ASPECTS can be used for prognostic evaluation after EVT. M...

BACKGROUND AND PURPOSE: Stroke is reported as a consequence of severe acute respiratory syndrome coronavirus-2 (SARSCoV- 2) infection in several reports. However, data are sparse regarding the details of these patients in a multinational and large scale. METHODS: We conducted a multinational observational study on features of consecutive acute isch...

Background: Superficial temporal artery-middle cerebral artery microvascular bypass (STA-MCA MVB) is an important strategy for the management for selected patients. Objectives: To present our 19-year experience with STA-MCA MVB. Methods: Data for consecutive patients who underwent STA-MCA MVB from 2000-2019 due to moyamoya/moyamoya-like diseas...

Objective: Flow-diverter stents (FDSs) are not generally used for the management of acutely ruptured aneurysms with associated subarachnoid hemorrhage (SAH). Herein, the authors present their experience with FDSs in this scenario, focusing on the antiplatelet regimen, perioperative management, and outcome. Methods: The authors retrospectively re...

Background and Purpose: Timely reperfusion is an important goal in treatment of eligible patients with acute ischemic stroke. However, during the coronavirus disease 2019 (COVID-19) pandemic, prehospital and in-hospital emergency procedures faced unprecedented challenges, which might have caused a decline in the number of acute reperfusion therapy...

Background Clopidogrel is commonly used for secondary stroke prevention in patients with large vessel stenosis. Reduced Clopidogrel high on treatment platelet reactivity (CR) can lead to Clopidogrel underactivity (CU) causing acute thrombosis. However, the prevalence of CU among patients with acute symptomatic carotid disease remains unknown. There...

Background Symptomatic carotid stenosis is responsible for 10% of all strokes. Currently, CT angiography (CTA) is the main diagnostic tool for carotid stenosis. It is frequently the only diagnostic test preceding recommendations for carotid angioplasty and stenting (CAS) or carotid endarterectomy (CEA). However, the specificity of CTA, especially i...

Background: Accumulating evidence from randomized-controlled clinical trials (RCTs) suggest that tenecteplase may represent an effective treatment alternative to alteplase for acute ischemic stroke (AIS). In the present systematic review and meta-analysis we sought to compare the efficacy and safety outcomes of intravenous tenecteplase to intraveno...

Background According to the latest reported data from the National Acute Stroke Israeli Survey (NASIS), around 18,000 strokes occur annually in Israel. Data regarding disparities in stroke care between the Jewish and the Arab populations in Israel are lacking. Aims We wished to compare demographics, comorbidities, stroke characteristics and outcom...

Background and aims. Stent retriever based thrombectomy is the mainstay of treatment of acute ischemic stroke caused by large vessel occlusion. However, recanalization is sometimes not achieved even after multiple passes of the thrombectomy device. Whether revascularization becomes futile or harmful with an increasing number of passes as well as cr...

Background and Purpose Accumulating evidence from randomized controlled clinical trials suggests that tenecteplase may represent an effective treatment alternative to alteplase for acute ischemic stroke. In the present systematic review and meta-analysis, we sought to compare the efficacy and safety outcomes of intravenous tenecteplase to intraveno...

Background Cardiac emboli secondary to atrial fibrillation (AF) commonly cause large vessel occlusions (LVO) that require endovascular thrombectomy (EVT) to restore cerebral circulation. Whether the outcome of patients with AF diagnosed after the index stroke (newAF) differs from that of AF-patients in which AF was known before stroke (kAF) remains...

Background and aimsClot extraction is associated with favorable outcome in patients with large vessel occlusions (LVO) undergoing endovascular thrombectomy (EVT). However, whether revascularization becomes futile or harmful with an increasing number of passes remains unknown.Methods We performed a retrospective analysis of 271 consecutive patients...

Objective Risk of early recurrent ischemic stroke in patients with atrial fibrillation may be high. ASA/AHA guidelines provide imprecise recommendations on the timing and anticoagulant choice for this indication. We assessed current opinions of stroke neurologists. Methods Case scenarios describing patients with acute ischemic stroke (AIS) due to...

Background and objectivesEndovascular thrombectomy (EVT) is efficacious in patients with large vessel occlusion stroke (LVO). We explored whether internal carotid (ICA) tortuosity increases the technical difficulty of EVT thereby lowering the chances of successful recanalization and favorable outcomes.Patients and methodsConsecutive patients with L...

Background: Stroke is reported as a consequence of SARS-CoV-2 infection. However, there is a lack of regarding comprehensive stroke phenotype and characteristics Methods: We conducted a multinational observational study on features of consecutive acute ischemic stroke (AIS), intracranial hemorrhage (ICH), and cerebral venous or sinus thrombosis (CV...

Background: Pathological changes in the cerebral white matter can be determined both in small vessel disease and in cerebral amyloid angiopathy. The pattern of involvement may be different depending on the etiology and severity of the process. Objective of the study: Determination and analysis of the pattern of cerebral white matter changes in pati...

Background Atrial fibrillation (AF) often leads to large vessel occlusions (LVO) which may necessitate endovascular thrombectomy (EVT). Whether the adequacy of treatment with oral anticoagulants (OAC) prior to LVO modifies outcomes remains unknown. Patients and Methods Consecutive EVT-treated LVO patients were recruited and the data was analyzed r...

We examined to what extent clinical assessment alone can predict subtle acute cerebral infarction on magnetic resonance imaging (MRI). Of the 72 patients presented to the emergency department (ED) with transient neurological deficits, 26 (36.1%) were predicted to be “positive” and 46 (63.9%) “negative” for transient ischemic attack/minor stroke by...

Background and purpose: We investigated the effectiveness of intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients with large vessel or distal occlusions and mild neurological deficits, defined as National Institutes of Health Stroke Scale scores <6 points. Methods: The primary efficacy outcome was three-month functional indepen...