Extrapontine myelinolysis with involvement of the hippocampus in three children with severe hypernatremia

Central pontine myelinolysis is a disorder of unknown etiology linked to ov erly aggressive correction of hyponatremia. In addition to the typical loca tion of demyelination with preservation of neurons and axon cylinders in th e basis pontis, similar lesions have been described in extrapontine locatio ns. Central pontine myelinolysis and extrapontine myelinolysis usually occu r together, and are identified at autopsy rather than in life because sympt oms of extrapontine myelinolysis are often masked in the critically ill pat ient. Central pontine myelinolysis is described in children, usually in the clinical setting of hyponatremic dehydration. Extrapontine myelinolysis ha s not been described in children previously. We report three children with severe hypernatremia and extrapontine myelinolysis involving various combin ations of thalamus, basal ganglia, external and extreme capsules, and cereb ellar vermis. All three had additional involvement of the hippocampus seen on T-2-weighted magnetic resonance imaging. None of the three had detectabl e pontine lesions. Clinical features of the three cases were dehydration in a 28-month-old girl, respiratory syncytial virus bronchiolitis in a 14-mon th-old girl, and acute respiratory failure due to anaphylaxis after consump tion of walnuts in a 3-year-old boy. Peak sodium values in each child were 195, 168, and 177 mmol/L, respectively; each received aggressive treatment for hypernatremia. We believe this to be the first report of extrapontine m yelinolysis in children, the first report; of extrapontine myelinolysis wit hout central pontine myelinolysis in children, and the first report hl chil dren of hippocampal formation involvement. The patho genesis of the central and extrapontine myelinolysis complex in children is more complicated than previously believed, and might differ significantly from that of adults.