下垂体腺腫との鑑別が困難であったトルコ鞍内髄膜腫の1例

A Case of Intrasellar Meningioma Mimicking Pituitary Adenoma

I．はじめに

　トルコ鞍内髄膜腫（intrasellar meningioma）はトルコ鞍近傍に発生する髄膜腫のなかでもきわめて稀な疾患であるが，手術法の選択に当たっては術前に本疾患と非機能性下垂体腺腫を鑑別することが重要である．われわれは汎下垂体機能低下症で発症し，非機能性下垂体腺腫の診断のもとに経蝶形骨洞法による手術を行い，病理学的に髄膜腫と診断し得た1例を経験した．症例を呈示し，特にそのMRI上の画像診断の特徴について検討を加えて報告する．

The authors report a patient with a rare intrasellar meningioma mimicking pituitary adenoma. A 60-year-old man was admitted to our hospital for evaluation of general fatigue. He had no neurological deficit in-cluding visual function. Endocrinological tests revealed panhypopituitarism. The craniogram showed slightenlargement of the sella turcica with thinning of the dorsum sellae. CT scan and MR imaging demons-trated a homogeneously enhanced intrasellar mass with slight suprasellar extension. Partial removal of themass was performed via the transsphenoidal approach because it was extremely firm and hemorrhagic.Histological diagnosis was transitional meningioma. The patient has been well for two years after surgerywithout tumor progression on MR imaging.

It is mandatory to distinguish intrasellar meningioma from pituitary adenoma preoperatively because ofmarked difference in their treatment strategies. Despite recent advances in neurodiagnostic imaging, it maystill be difficult to differentiate pituitary adenoma from intrasellar meningioma. When we re-evaluated theMR imaging, we recognized that the tumor had demonstrated specific findings, ruling out pituitary adeno-ma, namely bright and homogeneous enhancement, dense enhancement in the early phase on the dynamicMR study, and flow void signal within the mass.

The authors emphasize that careful evaluations of MR imaging will allow the correct preoperative di-agnosis in patients with intrasellar meningioma mimicking pituitary macroadenoma.