Paediatric Arteriopathy Steroid Aspirin Project

Inclusion Criteria: \-- Aged 6 months to \<15 years * AIS ≤ 48 hours * Newly acquired focal neurological deficit with confirmation by magnetic resonance imaging (MRI) of ischaemic lesion in an arterial territory corresponding with the clinical features (definition of Arterial ischemic stroke). * Magnetic resonance arteriography showing unilateral proximal stenosis or irregularities of the corresponding carotid trifurcation (i.e. terminal carotid and/or M1-M2 and/or A1 segments) or of the posterior circulation (P1-P2 segments). * No evidence of an underlying systemic disorder (e.g. lupus erythematodes) explaining the features. * Informed and signed consent of parents or legal guardians. * French Social Security (Sécurité sociale; i.e. national health coverage) affiliation Exclusion Criteria: * Children with secondary central nervous system angiitis due to infections (meningitis, endocarditis, borreliosis), rheumatic or other systemic inflammatory diseases (e.g. lupus erythematodes). These children are already under immune suppression or need other co-medications regarding their underlying disease. * Children with known syndromal and/or genetic vasculopathies such as phaces syndrome, Neurofibromatosis type 1, trisomy 21. * Children with moyamoya or sickle cell disease. * Children with a progressive large to medium vessel childhood primary angiitis of the central nervous system with two out of the following three criteria : Children with progressive neurocognitive dysfunction; Children with bilateral lesions/vessel involvement; Children with distal arterial stenosis (beyond the M2, A1 or P2 segment). \- Children already on steroid treatment at disease onset or with a contraindication to receive steroid treatment (e.g. congenital or acquired immunodeficiency). * Children with delayed diagnosis ≥3 days as treatment start is not allowed to be more ≥5 day-delayed. * Contraindications to steroids (see also summary of product characteristics in chapter 1.1) and notably: Not-manageable infectious, hydro-electrolytic or metabolic (e.g. diabetes mellitus) disorders, or elevated blood pressure, Serious behavioral disorders, Current vaccination with live or attenuated live strains, Allergy/sensibility to any ingredient, Association with some medications such as antiarrhythmic drugs.