NEFL and Stroke: 2 independent cohorts of patients with IS: cohort 1: serial serum sampling at hospital arrival (n = 196), at days 2, 3, and 7 (n = 89), and up to 6 months post stroke; Cohort 2: standardized MRI at baseline and at 6 months post stroke, and with cross-sectional serum sampling at 6 months (n = 95). The best association among clinical outcome and serum NF-L is measured at 7 days or within 48 h after symptom onset.