Chronicity of hyponatremia as a factor in experimental myelinolysis.

A recent analysis of hyponatremic patients disclosed that those who were chronically hyponatremic prior to rapid correction subsequently developed central pontine myelinolysis. To test the view that chronicity of hyponatremia is a factor in myelinolysis, we studied a group of rats that were hyponatremic for 1 day and compared it with another group of animals maintained in a hyponatremic state for 3 days prior to the administration of hypertonic saline solution. The 3-day hyponatremic rats developed more numerous and more severe demyelinative lesions than the 1-day rats. The findings support the view that duration of hyponatremia is a factor in myelinolysis and that the electrolyte disturbance of chronically hyponatremic patients should be corrected cautiously and relatively slowly.