Inclusion Criteria:  Informed consent of the legal representative of the trial participant documented by signature Age > 6 months & < 18 years at time of stroke Randomisation possible within 48 hours of diagnosis and maximum 96 hours after stroke onset  Unilateral arteriopathy according to the following criteria:  Newly acquired neurologic deficits  Specific neuroimaging (MRA) features of either  unilateral stenosis, or unilateral vessel irregularities within the Central Nervous System (CNS) Female participants age ≥ 13: Negative pregnancy test (blood)  Exclusion Criteria:  Previous stroke Known syndromal disorders, as e.g. Trisomy 21, Neurofibromatosis type 1 Known genetic vasculopathies as e.g. PHACES syndrome, ACTA II Moyamoya or sickle cell disease Small vessel cerebral vasculitis (primary CNS vasculitis) Bilateral arteriopathy Arterial dissection(s) Evidence of underlying systemic disorders, as e.g. lupus, rheumatoid problems Secondary CNS angiitis due to infections (meningitis, endocarditis, borreliosis), or generalised angiitis due to rheumatic or other autoimmune problems  Progressive large to medium childhood primary angiitis of the CNS (cPACNS ) with 2 of the following 3 criteria:  pre-existing progressive neurocognitive dysfunction bilateral MRI lesions/vessel involvement small vessel arterial stenosis On steroid treatment at disease onset Contraindication to steroid treatment as e.g. a congenital or acquired immunodeficiency Inability to follow the procedures of the study, e.g. due to language problems Participation in another interventional study within the 30 days preceding the indication stroke and during the present study