The knowledge about nutritional, toxic, and metabolic causes of dementia is particularly important, because they may be reversible. Central pontine myelinolysis(CPM) is one of these causes. CPM is a well known but rare metabolic disease of unknown etiology linked to overly aggressive correction of hyponatremia. We report a 74-year-old woman who developed disorientation, memory disturbance, and behavioral problem following intensive care unit management for pneumonia. Mini-mental status examination-Korean version(MMSE-K) study revealed severe cognitive dysfunction. Brain magnetic resonance imaging showed changes consistent with CPM and extrapontine myelinolysis. After supportive care, patient's clinical status was significantly improved. We suggest that a metabolic problem such as CPM should be considered in the diagnosis of acute or subacute cognitive deterioration in elderly patients.