Hyponatraemia secondary to cerebral salt wasting syndrome following routine pituitary surgery.

A female aged 53 years was found to have a suprasellar lesion, which was shown to be a Rathke's cyst after removal by transsphenoidal surgery. She presented 16 days postoperatively, and following two grand mal seizures was found to be profoundly hyponatraemic (sodium 101 nmol/l). She was initially thought to have the syndrome of inappropriate antidiuretic hormone and was treated accordingly, but central venous pressure measurement revealed the hypovolaemia of cerebral salt wasting syndrome. The patient subsequently developed severe neurological sequelae after the correction of her hyponatraemia, following the development of extrapontine myelinolysis. Cerebral salt wasting syndrome is a rare cause of hyponatraemia following pituitary transsphenoidal surgery, which may mimic the syndrome of inappropriate antidiuretic hormone secretion. This case emphasizes the poor prognosis that may result from the rapid correction of profound hyponatraemia.