MR imaging of intrasellar meningiomas simulating pituitary adenomas.

Over 3 1/2 years, 401 magnetic resonance studies were performed for suspected sellar-parasellar masses. Twenty-nine pituitary macroadenomas and 12 meningiomas were detected. Among the meningiomas there were three whose MR appearance simulated that of a pituitary tumor. In none of these cases was the diaphragma sellae visualized. Furthermore, in one case the prolactin level was elevated. A preoperative diagnosis of pituitary tumor resulted in an inappropriate surgical approach being used initially for its removal (transsphenoidal). Thus, nonvisualization of the diaphragma sellae and elevated prolactin levels do not exclude a nonpituitary origin of a sellar-parasellar tumor. Other methods for preoperative differentiation are discussed.