Acute severe hypernatremia complicated by osmotic demyelination syndrome in a 13-day-old infant

This clinical case reports a neonatal osmotic demyelination syndrome associated with iatrogenic hypernatremia. A 13-day-old neonate initially admitted to the hospital with poorly tolerated fever due to enterovirus meningitis developed severe hypernatremia (184 mmol/L) following an error in fluid therapy, which was complicated by extra-pontine demyelination syndrome (subtype of osmotic demyelination syndrome). The child presented with nonspecific neurological symptoms of irritability, tremors and convulsions. Natremia was slowly corrected by hyperhydration within 26.5 h. Brain imaging revealed lesions consistent with extra-pontine demyelination. At 3 months, both clinical signs and MRI lesions had markedly regressed. Sudden osmolar variations can induce osmotic demyelination syndrome. Few cases have been reported in the pediatric population but none in the neonatal period to our knowledge. Measures to prevent sudden changes in osmolarity are critical to prevent poor neurological outcomes. Dysnatremia correction rates must be strictly controlled and customized according to the presence of neurological symptoms, the severity of sodium fluctuation, and the course of tonicity imbalance.