The occurrence of severe hyponatremia is an unusual complication in patients with a mild head injury. Between December 2001 and January 2003, 1147 patients with a mild head injury were reviewed. Only patients who presented with deterioration of consciousness or seizure due to hyponatremia, confirmed by serum investigation, were further evaluated, presenting features and clinical courses. The results revealed only 3 patients developed severe hyponatremia following a mild head injury. Surprisingly, all of them had a recent history of ecstasy (MDMA) use, as well as hyponatremia which didn’t develope until the episode of a
mild head injury. In the present report, the associated mechanisms of both conditions of severe hyponatremia are discussed and the literature is reviewed.

Keywords: Ecstasy, MDMA, Hyponatremia, Mild head injury