Osmotic demyelination syndrome (ODS) happens in osmotic stress. Thiamine deficiency causes Wernicke-Korsakoff syndrome (WKS). A 39-year-old woman with anorexia nervosa presented with impaired consciousness. Sodium was 179, MRI showed signs of ODS and WKS. Hypernatremia is argued as a rare ODS cause. In malnutrition, WKS might overlap with ODS.