A 65-year-old man was admitted with a sudden onset of dyspnea. Severe mitral 
regurgitation due to torn chordae tendinae was revealed on UCG. Mitral valve 
replacement was undergone. The postoperative course was complicated with a low 
cardiac output syndrome which was successfully treated with IABP, catecholamines 
and vasodilators. However, stupor developed on the 4 th postoperative day, 
following by tetrapregia on the 8 th day, and deep coma on the 15 th day 
respectively. Laboratory studies of the 4 th day disclosed the following values, 
serum sodium 150 mEq/l, blood urea nitrogen 84.7 mg/dl, blood sugar 184 mg/dl 
and calculated serum osmolality 354 mOsm/l. Cranial CT of the 15 th day showed 
an obscure low density area in the central pons which was strongly suggestive of 
central pontine myelinolysis (CPM). His CNS symptoms improved dramatically after 
administration of thyrotropin-releasing hormone tartrate (TRH-T). A diagnosis of 
CPM was made on MRI of the 41 st day. He discharged without any neurological 
deficit on the 62 nd day.