Background: The extrapontine myelinolysis (EPM) of osmotic demyelination syndrome (ODS) is a rare and dangerous disorder of the central nervous system. The mechanism is not fully understood and the treatment is controversial. There are few reports of EPM occurred after endonasal endoscopic resection of pediatric craniopharyngioma. Case presentation: We report two unusual cases of such a rare condition. Both are procedured uneventful endonasal endoscopical craniopharyngioma resection, after operation, the patients suffered serious diabetic insipidus with remarkable fluctuation of serum sodium though we applied pitutrin continual management to maintain everyday normal urine and correct serum sodium disorder. MR images occured caudal and lentiform nuclei myelinolysis following these serious conditions. Conclusions: In this study relevant literatures are reviewed in order to further understand this complication and contribute to the prevention and treatment of EPM caused by inappropriate correction of serum sodium disorder.