MYELINOLYSIS AFTER CORRECTION OF HYPONATREMIA

Myelinolysis is a neurologic disorder that can occur after rapid corre ction of hyponatremia. Initially named ''central pontine myelinolysis, '' this disease is now known to also affect extrapontine brain areas. Manifestations of myelinolysis usually evolve several days after corre ction of hyponatremia. Typical features are disorders of upper motor n eurons, spastic quadriparesis and pseudobulbar palsy, and mental disor ders ranging from mild confusion to coma. Death may occur. The motor a nd localizing signs of myelinolysis differ from the generalized enceph alopathy that is caused by untreated hyponatremia. Experiments have du plicated the clinical and pathologic features of myelinolysis by rapid ly reversing hyponatremia in animals. Myelinolysis is more likely to o ccur after the treatment of chronic rather than acute hyponatremia and is more likely to occur with a rapid rate of correction. The exact pa thogenesis of myelinolysis has not been determined. Optimal management of hyponatremic patients involves weighing the risk for illness and d eath from untreated hyponatremia against the risk for myelinolysis due to correction of hyponatremia. Experiments in animals and clinical ex perience suggest that correction of chronic hyponatremia should be kep t at a rate less than 10 mmol/L in any 24-hour period.