This clinical trial deals with focal cerebral arteriopathy and childhood stroke, a rare but devastating condition. Focal cerebral arteriopathy (FCA) is an inflammatory vessel wall disease provoked by infection and there is increasing evidence that inflammatory processes play a crucial role in childhood stroke, influencing the outcome of the disease. Analysis of existing data suggests that outcomes are improved and that there is less stroke recurrence in children treated with steroids to reduce the acute inflammatory processes. This clinical trial will be conducted in over 20 hospitals in several countries in order to investigate this. Participants will be randomly separated into two groups. The first group will be treated with standard of care (including aspirin) combined with high dose steroids. The second group will be treated with standard of care (including aspirin) but without steroid treatment. The objective is to investigate if children treated with a combination of high dose steroid and aspirin will have a better and quicker recovery of FCA, better clinical functional outcome, and less recurrence compared to children treated with aspirin alone. This project has been identified by international pediatric stroke experts as the most important topic for a clinical trial in the field and is as well one of the most important research priorities identified by parents. The study results will also provide insight into the evolution of inflammatory vessel disease.