[Central and extrapontine myelinolysis following correction of extreme hyponatremia. Case report and review of the literature].

We report a case of a 43-year-old woman who developed osmotic demyelination syndrome following correction of extreme hyponatremia that was considered to be of chronic nature. The serum sodium level was 91 mmol/L on admission to hospital. It was decided to correct the serum sodium slowly with the goal that the rate of correction would be no more than 12 mmol/l per 24 hours. This was achieved during the first two days of treatment but during the third day the rise in serum sodium was 13 mmol/l. On the 11th day of admission the patient had developed manifestations of pseudobulbar palsy and spastic quadriparesis. Magnetic resonance imaging study confirmed central and extrapontine myelonolysis. The patient received supportive therapy and eventually made full recovery. Current concepts in the pathophysiology of osmotic demyelination syndrome and the treatment of hyponatremia are reviewed. We recommend that the rate of correction of chronic hyponatremia should not exceed 8 mmol/l per 24 hours.