Early immunosuppressive treatment guided by vessel wall enhancement on MRI for primary angiitis of the central nervous system in childhood.

We aimed to report a case presenting with abrupt onset of acute right hemiplegia and severe headache, which was diagnosed as primary angiitis of the central nervous system in childhood (cPACNS). MRI revealed an acute cerebral infarction and long-segment concentric vessel wall enhancement in the left middle cerebral artery, with the enhancement resolving within 26 days following prompt steroid therapy, earlier than in previous reports. Laboratory and cerebrospinal fluid findings were unremarkable, except for transient elevations in lactate and pyruvate levels. Other potential causes were excluded. Early immunosuppressive treatment with intravenous methylprednisolone, followed by oral steroids, caused gradual clinical improvement without cognitive decline. This case highlights the significance of contrast-enhanced MRI during the acute phase in patients presenting with cerebral infarction accompanied by headaches. In patients with cPACNS, early therapeutic intervention may cause the prompt resolution of contrast enhancement, reduce long-term sequelae and improve clinical outcomes.