[Symptomatic Rathke's cleft cyst presenting with hyponatremia: a case report].

A case of symptomatic Rathke's cleft cyst, showing symptoms due to hyponatremia, is reported. The patient was a 68-year-old woman with complaints of vomiting, diarrhea and somnolence. She had severe hyponatremia (109 mEq/l). Magnetic resonance image showed a cystic mass in the intra- and suprasellar region. A right fronto-temporal craniotomy was performed and the cyst was partially resected through the pterional approach. The cyst compressed the chiasma and anterior hypothalamus upward. In the cyst, there was xanthomatous fluid and hematoma. On histopathological examination, the cyst epithelium was diagnosed as Rathke's cleft cyst with craniopharyngioma component. These findings suggested that rapid compression to the anterior hypothalamus by intracystic hemorrhage caused hyponatremia.