Background: Cerebral salt wasting syndrome (CSWS) is one of several possible causes of the development of hyponatraemia in patients with severe cranial trauma associated with intracranial bleeding and brain oedema. Other possible causes of post-traumatic hyponatraemia include the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Methods: The authors present the case of a twenty-five-year-old polytraumatized female patient who was treated in our department and who was diagnosed with cerebral salt wasting syndrome.

Conclusions: In patients with severe cranial trauma and subsequent hyponatraemia, CSWS should be considered. It is crucial to distinguish between CSWS and SIADH as wrongly selected treatment can have serious or even fatal impacts for a gravely injured patient.