Premonitory symptoms of cerebral edema occur in as few as 50% and include severe headache, declining mental status, seizures, and papilledema. Cerebral edema typically occurs 6 to 12 hours after initiating therapy and presents as headache, mental status changes, seizure, or coma. Although the etiology of this complication is unknown, it is felt that several factors may contribute, including overly aggressive fluid therapy, rapid correction of blood glucose levels, bicarbonate therapy, and failure of the serum sodium level to increase with therapy.