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Background and Purpose: Understanding the mechanisms underlying progression/regression of symptomatic intracranial atherosclerotic stenosis (sICAS) will inform secondary prevention of the patients. Focal wall shear stress (WSS) may play an important role, which, however, had seldom been investigated. Methods: Patients with acute ischemic stroke or transient ischemic attack (TIA) attributed to 50% to 99% intracranial atherosclerotic stenosis were recruited. All patients underwent cerebral computed tomography angiography at baseline, and a computational fluid dynamics model was built based on computed tomography angiography to simulate blood flow and quantify WSS in the vicinity of the sICAS lesion. All patients received optimal medical treatment and a second computed tomography angiography at 1 year. The change in the luminal stenosis from baseline to 1 year in sICAS was defined as progression (increased >10%), quiescence (±10%), or regression (decreased >10%). Associations between baseline WSS metrics and sICAS regression were analyzed. Results: Among 39 patients (median age 62 years; 27 males), sICAS luminal stenosis progressed, remained quiescent and regressed in 6 (15.4%), 15 (38.5%), and 18 (46.2%) cases, respectively. A higher maximum WSS and larger high-WSS area, throughout the sICAS lesion or obtained separately in the proximal and distal parts of the lesion, were independently associated with regression of luminal stenosis in sICAS over 1 year. Conclusions: A majority of sICAS lesions regress or stay quiescent in the luminal stenosis over 1 year after stroke under optimal medical treatment, when higher focal WSS may facilitate stenosis regression. Further studies of the effects of hemodynamics including WSS in altering plaque vulnerability and stroke risks are needed.

Objective As Hong Kong faced the 5 th wave of the COVID‐19 pandemic, the facilitators and hurdles towards effective vaccination is important for healthcare professionals to understand the vaccination gap among patients with epilepsy. Methods A cross‐sectional, pragmatic study of COVID‐19 vaccination was performed at a tertiary epilepsy centre with regards to patterns of vaccination and any unusually high rate of adverse events. Patients having recent visits at the epilepsy centre (4 months) had their anonymized electronic linkage records examined 12 months after the inception of vaccination program for types of vaccines, seizure demographics, and adverse events following immunization(AEFI). Results 200 patients with epilepsy and their anonymized data were analyzed. The vaccine uptake was approximately 60% of that of the general population. Twice as many patients with epilepsy chose to receive mRNA vaccine as compared with inactivated vaccine. The proportion of patients who kept up‐to‐date with all available dosing was 7%. Patients with epilepsy with genetic aetiology were least likely to receive vaccination (13/38, 34%, p=0.02). There was no unreasonably high rate of unacceptable side effects after vaccination among patients with epilepsy. Only 3 patients reported worsening of seizures without meeting the criteria for AEFI. Refractory epilepsy, allergy to antiseizure medications and elder age (>=65) did not confer any significant difference in vaccination patterns or adverse effects. Significance A vaccination gap exists among epilepsy patients which calls for actionable strategies for improving vaccine uptake, including education and outreach programs.

Background and Objectives:Ischemic stroke despite direct oral anticoagulant (DOAC) is increasingly common and portends high risk of subsequent ischemic stroke. Efficacy and safety of antithrombotic regimens following the condition are unclear. We aimed to compare the outcomes of patients with ischemic stroke despite DOAC with and without an alternative antithrombotic regimen, and determine the risk factors of recurrent ischemic stroke while on anticoagulation.Methods:In a population-based, propensity-score weighted, retrospective cohort study, we compared the clinical outcomes of DOAC-to-warfarin switch, DOAC-to-DOAC switch (DOACswitch) or addition of antiplatelet agents, with unchanged DOAC regimen (DOACsame) among non-valvular atrial fibrillation (NVAF) patients who developed the first ischemic stroke despite DOAC from 1stJanuary 2015 to 31stDecember 2020 in Hong Kong. Primary outcome was recurrent ischemic stroke. Secondary outcomes were intracranial hemorrhage, acute coronary syndrome and death. We performed competing risk regression analyses to compare the clinical endpoints, and determined the predictors of recurrent ischemic stroke in an unweighted multivariable logistic regression model.Results:During the 6-year study period, among 45,946 AF patients on DOAC as stroke prophylaxis, 2,908 patients developed ischemic stroke despite DOAC. 2,337 NVAF patients were included in the final analyses. Compared to DOACsame, warfarin (aHR 1.96, 95%CI 1.27-3.02, p=0.002) and DOACswitch(aHR 1.62, 95%CI 1.25-2.11, p-value <0.001) were associated with increased risk of recurrent ischemic stroke. In DOACsamegroup, adjunctive antiplatelet agent was not associated with reduced risk of recurrent ischemic stroke. Diabetes mellitus, concurrent cytochrome P450/P-glycoprotein (CYP/P-gp) modulators and large artery atherosclerotic disease (LAD) were predictors of recurrent ischemic stroke.Discussion:In NVAF patients with ischemic stroke despite DOAC, the increased risk of recurrent ischemic stroke with switching to warfarin called for caution against such practice, while the increased ischemic stroke with DOAC-to-DOAC switch demands further studies. Adjunctive antiplatelet agent did not appear to reduce ischemic stroke relapse. As diabetes mellitus, use of CYP/P-gp modulators and LAD were predictors of recurrent ischemic stroke, further investigations should evaluate if strict glycemic control, DOAC level monitoring and routine screening for carotid and intracranial atherosclerosis may reduce ischemic stroke recurrence in these patients.Classification of Evidence:This study provides Class II evidence that in patients with non-valvular atrial fibrillation suffering an ischemic stroke while being treated with a DOAC, continuing treatment with that DOAC is more effective at preventing recurrent ischemic stroke than switching to a different DOAC or to warfarin.