Extrapontine myelinolysis after correction of chronic hyponatraemia with isotonic saline.

Rapid correction of severe chronic hyponatraemia with hypertonic saline can cause central pontine myelinolysis. Less well appreciated are the dangers of rapid correction with isotonic saline. A case is reported in which correction of severe hyponatraemia by 11 mmol/l in 24 hours with isotonic saline produced extensive extrapontine myelinolysis, one of the manifestations of the osmotic demyelination syndrome.