RESUMO
OBJECTIVE: To report a pediatric case of central pontine and extrapontine myelinolysis, a rare neurological disease often associated with rapid correction of hyponatremia. DESCRIPTION: A 15 year-old female adolescent developed locked-in syndrome during severe hyponatremia. Brain magnetic resonance imaging was consistent with the diagnosis of central pontine and extrapontine myelinolysis. COMMENTS: Serum sodium correction should proceed slowly and cautiously, based upon a careful calculation of sodium deficit, in order to minimize metabolic stress and avoid the occurrence of this dreadful complication, which has a tragic outcome in most cases. There is no scientifically proved effective treatment for myelinolysis, and severe cases usually have a dismal prognosis.