Osmotic demyelination syndrome
Background
Osmotic demyelination syndrome (ODS; also formerly called central pontine myelinolysis or CPM) is a neurologic condition caused by rapid correction of hyponatremia, and is characterized by dysarthria, dysphagia, lethargy, paraparesis or quadriparesis, seizures, coma, and death.(2) Osmotic demyelination syndrome was first described in a 1959 paper by Adams, Victor, and Mancall, who described rapidly evolving quadriplegia and pseudobulbar palsy in 3 alcoholic men.
Risk Factors
Osmotic demyelination syndrome is caused by rapid correction of hyponatremia (>12 mEq/L/24 h) as water moves from cells to extracellular fluid, yielding intracellular dehydration. Starting serum sodium concentration is almost always 120 meq/L or less. Risk factors for osmotic demyelination syndrome include: chronic heart failure, alcoholism, cirrhosis, hypokalemia, malnutrition, and treatment with vasopressin antagonists such as tolvaptan.(1)
Clinical Features
Both men and women are equally affected. Symptoms can be present two to six days after inappropriately rapid correction of the serum sodium concentration has occurred. Symptoms are often irreversible or only partially reversible, and include dysarthria, dysphagia, paraparesis or quadriparesis, behavioral disturbances, movement disorders, seizures, lethargy, confusion, disorientation, obtundation, and coma. Severely affected patients may develop "locked in" syndrome. (3)
MRI can be used to visualize the pontine lesion with a characteristic "batwing" lesion of the pons appearing in typical cases.(2)
Prevention
In patients with chronic severe hyponatremia (Na <120mEq), the correction rate of sodium should not exceed 6 mEq/24 hours for patients with other ODS risk factors, or 12 mEq/24 hours for those without other risk factors (1). Hypertonic (3%) saline should be given at a low infusion rate, 0.5 to 1 mL/kg/h, with frequent serum sodium checks to ensure that the correction rate does not exceed the above limits.
References
1.) Petrino R, Marino R. Fluids and Electrolytes. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e New York, NY: McGraw-Hill; 2016.
2.) Ropper AH, Samuels MA, Klein JP. eds. Adams & Victor's Principles of Neurology, 10e New York, NY: McGraw-Hill; 2014.
3.) Sterns RH, Riggs JE, Schochet SS. Osmotic demyelination syndrome following correction of hyponatremia. N Engl J Med. 1986;314(24):1535-42.