Osmotic Demyelination Unrelated to Hyponatremia.

Osmotic demyelination unrelated to hyponatremia is rarely reported. We present a case of osmotic demyelination in a patient with hypernatremia in the absence of preceding hyponatremia and review previously reported cases of osmotic demyelination in nonhyponatremic patients. We conclude that a rapid increase in serum sodium concentration and plasma tonicity even in the absence of preceding hyponatremia may surpass the brain's capacity for adaptation to hypertonicity and lead to osmotic demyelination in predisposed individuals. Risk factors for osmotic demyelination in patients with chronic hyponatremia and without hyponatremia are probably similar and are usually associated with states of limited brain osmolyte response, such as alcoholism, liver disease (including those undergoing orthotopic liver transplantation), malnutrition, malignancy, pregnancy/postpartum state, severe illness/sepsis, adrenal insufficiency, and metabolic derangements. Clinicians should be vigilant in identifying individuals who may, even in the absence of hyponatremia, have increased susceptibility to osmotic demyelination and avoid rapid fluctuations in serum sodium concentrations in such patients.