Formerly called "central pontine myelinolysis"
A neurologic condition caused by rapid correction of hyponatremia, with starting serum sodium normally 120 meq/L or less
Caused by rapid correction of hyponatremia (>12 mEq/L/24 h), as water moves from cells to extracellular fluid, yielding intracellular dehydration.
Symptoms are often irreversible or only partially reversible
Chronic heart failure
Alcoholism
Cirrhosis
Hypokalemia
Malnutrition
Treatment with vasopressin antagonists (e.g. tolvaptan)
Lower initial sodium
Schizophrenia
Lower baseline urine sodium
Osmotic demyelination syndrome
Hypoxic encephalopathy
Limbic encephalitis
Acute toxic-metabolic encephalopathy 
Neoplastic meningitis
Hypoglycemia
Posterior reversible encephalopathy syndrome
Hyperosmolar state 