Hyponatremia is a common electrolyte disturbance usually observed in neurosurgical patients undergoing surgical management of traumatic, as well as, nontraumatic intracranial pathology. The spinal cord trauma is also associated with occasional development of such hyponatremia; it usually occurs within the first two-weeks of the injury. Hyponatremia can lead to alterations of consciousness, convulsions, coma, cardiac arrhythmias and on rare occasions, death. Authors present a practical oriented review of the literature.