Serum sodium determinations were studied prospectively in 69 children with febrile convulsions followed in the Department of Paediatrics, Zuiderziekenhuis, Rotterdam, the Netherlands. Levels <135 mmol/1 were found in 52%, and the mean level (134.4 mmol/1) was significantly lower compared to a group of children without fever (140.6 mmol/1) and a group with fever but no convulsions (137.6 mmol/1). Febrile seizure recurrence appeared to be correlated with a lowered serum sodium. 
COMMENT. The authors acknowledge previous demonstration of a lowered threshold to febrile convulsions in animals with hyponatremia , but overlook the previous clinical report of hyponatremia (130 mEg/1 or lower) in 4 (24%) of 17 children with febrile seizures, and serum sodium of 131 - 138 mEq/1 in the remaining 13 patients examined [3, 4]. Serum sodium determination is important in a child with a febrile convulsion.