A 9-year-old girl presented with an acute right-sided hemiparesis. Initially, the clinical presentation and stable vasculopathic abnormalities on MR and conventional angiography were suspicious of a so-called "transient cerebral arteriopathy". Mild but persistent pleocytosis and an elevated CSF IgG index led to an extensive search for infectious and immunological causes of cerebral vasculitis, eventually revealing neuroborreliosis. Although rare, infectious and potentially treatable causes of arterial ischemic stroke should be considered in every child with a documented cerebral arteriopathy.