The role of serum sodium in susceptibility to complicated febrile convulsions was studied in 115 children admitted with simple or complicated febrile convulsions to the Kuopio University Hospital, Finland. Sodium levels were lower in children with complex FC in comparison with those having simple convulsions. The means were 136.07 (n= 42) and 137.62 mmol l-1(n=71), respectively. Sodium levels were lowest in children with repeated seizures. Levels <135 occurred in 47% of children with repeated FC and only in 8% of those with simple FC, but 50% of these simple FC cases had later complicated, repeated seizures, status epilepticus, or they developed epilepsy within 3 years. Serum potassium concentrations showed no significant changes between simple and complicated FC groups. 
COMMENT. Hyponatremia may increase the risk for complicated and multiple FC during the same febrile illness.
A further study by the above investigators concerns “osmolality and electrolytes in cerebrospinal fluid and serum of febrile children with and without seizures .” CSF osmolality was lower in 60 febrile children than in 30 nonfebrile controls. The febrile groups, 36 with and 24 without seizures, did not differ, but those with repeated FC had lower CSF osmolality than the simple FC group. Differences in serum osmolality between groups were smaller than those in the CSF. Serum and CSF osmolalities showed a positive correlation. The body temperature and osmolality values were negatively correlated. Decreases in CSF sodium concentration with increasing body temperature paralleled those of CSF osmolality. Age was used as a covariant in group comparisons, since osmolality and sodium concentration in CSF correlated with age in nonfebrile children. For further reference to hyponatremia in febrile convulsions, see Ped Neur Briefs June 1995;9:48.