Nannoni S, Youma ASM, Amiguet M, et al. - Since certain patients with acute ischemic stroke (AIS) do not exhibit established vascular risk factors (EVRFs), researchers sought to evaluate their clinical features, stroke subtype etiological classification, and long‐term outcome. All consecutive AIS patients from the Acute Stroke Registry of Lausanne (2003‐2018) were retrospectively analyzed with a complete assessment of the following EVRFs: hypertension, diabetes, major cardioembolic sources, dyslipidemia, smoking, obesity, alcohol abuse, previous stroke/TIA and depression/psychosis. Only 2% reported no EVRF in a consecutive AIS cohort. There was a strong correlation between patent foramen ovale and contraceptive use with the absence of EVRFs in younger patients, and female sex and active cancer in elderly patients. The results illustrate the significance of identifying previously unknown risk factors and/or uncommon stroke mechanisms in patients without EVRF.