Background: A 37-year-old woman without important previous medical history presented to an emergency room with acute onset of left-sided weakness and numbness. Examination revealed left-sided hemiparesis (in the arm greater than in the leg) and hypoesthesia. Investigations: Routine laboratory testing, lumbar puncture, dynamic susceptibility contrast perfusion study, longitudinal brain MRI, and magnetic resonance spectroscopy were performed. Diagnosis: Baló's concentric sclerosis. Management: Intravenous methylprednisolone followed by oral steroid taper.