Objective To analyze the clinical features of hyponatremia associated with traumatic brain injury (TBI) and investigate the experience in the diagnosis and treatment of central hyponatremia.Methods A retrospective analysis was performed on the clinical data of 118 TBI patients with hyponatremia admitted to the Department of Neurosurgery in our hospital from January 2005 to January 2011. The diagnosis was confirmed through clinical manifestations and laboratory examinations, and the effective treatment strategy was explored.Results Among the 118 cases, 103 (87.3%) were cured, and 15 (12.7%) died, including 2 cases due to abandoning treatment and 13 cases due to various complications ( without hyponatremia). The incidence rates of moderate or severe hyponatremia in patients with mild or moderate TBI, severe TBI, and extremely severe TBI were 37.0%, 54.3%, and 76.2%, respectively (χ²=7.296, P=0.026); the proportions of individuals with a duration of hyponatremia more than 8 days in the three groups of patients were 48.1%, 50.0%, and 85.7%, respectively (χ²=9.220, P=0.010). Twenty-two cases (18.6%) were diagnosed as cerebral salt wasting syndrome (CSWS), 7 cases (5.9%) as syndrome of inappropriate antidiuretic hormone secretion (SIADH), and 89 cases (75.5%) as nutritional hyponatremia. There was no significant difference in serum sodium concentration between patients with nutritional hyponatremia and those with CSWS or SIADH (t=-0.896, P=0.609); compared with those with nutritional hyponatremia, patients with CSWS or SIADH had significantly different plasma antidiuretic hormone (ADH) level and plasma osmotic pressure (t≥130.31, P<0.05).Conclusions The risk of developing moderate or severe hyponatremia and the duration of hyponatremia rise as the severity of TBI increases. The plasma ADH level of patients with CSWS is significantly lower than that of patients with nutritional hyponatremia, but the plasma ADH level of patients with SIADH is significantly higher than that of patients with nutritional hyponatremia. The plasma osmotic pressure of patients with CSWS or SIADH is lower than that of patients with nutritional hyponatremia. CSWS and SIADH are the main factors leading to hyponatremia associated with TBI, and the pathogenesis, clinical diagnosis, and treatment differ significantly between CSWS and SIADH. Early diagnosis, timely typing, and symptomatic comprehensive treatment can reduce the disability rate and mortality in patients and improve their prognosis.