In a patient with chronic severe hyponatremia, the correction of the serum sodium must not exceed 10 mmol/L per day to avoid osmotic demyelination syndrome (ODS). ODS is a neurologic disorder caused by severe damage to the myelin sheath of neurons in the brainstem, resulting in paralysis. First-line treatment for patients with chronic severe hyponatremia due to SIADH is fluid restriction. Hypertonic saline may be used in cases of severe symptomatic hyponatremia but must be administered slowly to prevent too rapid correction of the serum sodium. Aggressive fluid resuscitation with normal saline also runs the risk of too rapid changes in the serum sodium. Uncontrolled oral rehydration is not recommended because effects on the electrolyte balance cannot be controlled.