Pontine myelinolysis also called Osmotic demyelination syndrome (ODS) is a rare, acute noninflammatory neurologic disorder that is usually occurred by rapid correction of hyponatremia. It can involve the pons (central pontine myelinolysis, CPM) and other locations in the central nervous system (extrapontine myelinolysis, EPM). When osmotic demyelination occurs, it can be irreversible and has no proper management. Thus, prevention is most important. Almost all cases of Pontine myelinolysis were adult and old age in Korea. A sixteen year old girl was consulted from orthopedic surgery because of mental confusion and seizure. She had pelvic fracture and brain trauma by fall down. She recovered from hyponatremia, and it was corrected rapidly. Her brain MRI showed EPM (extrapontine myelinolysis) in Putamen and Internal capsular area. Clinical manifestations were tremor, catatonia, dysphagia, dysarthria and dysphasia. We present a young girl in whom osmotic demyelination occurred in the extrapontine area (EPM) after head trauma.