Posterior pituitary bright spot in large adenomas: MR assessment of its disappearance or relocation along the stalk

• Published in: Radiology Vol. 226; no. 2; p. 359
• Main Authors: Saeki, Naokatsu, Hayasaka, Michihiro, Murai, Hisayuki, Kubota, Motoo, Tatsuno, Ichiro, Takanashi, Jun-Ichi, Uno, Takashi, Iuchi, Toshihiko, Yamaura, Akira
• Format: Journal Article
• Language: English
• Published: United States 01.02.2003
• Subjects: Adenoma - pathology; Adenoma - surgery; Adult; Chi-Square Distribution; Diabetes Insipidus - etiology; Female; Humans; Hypothalamo-Hypophyseal System - pathology; Magnetic Resonance Imaging - methods; Male; Middle Aged; Pituitary Neoplasms - pathology; Pituitary Neoplasms - surgery
• ISSN: 0033-8419
• DOI: 10.1148/radiol.2262011616

To evaluate the disappearance or relocation patterns of posterior pituitary bright spot (PPBS) in the infundibuloneurohypophyseal (INH) system and endocrinologic implications in large pituitary adenomas. Sixty-nine patients with adenoma and supradiaphragmatic extension were classified into PPBS-visible and PPBS-nonvisible groups on the basis of findings at preoperative T1-weighted magnetic resonance (MR) imaging. The adenoma shapes were classified into hourglass type with indentation and barrel type without indentation at the diaphragmatic level. The PPBS-visible group included 55 (80%) patients. PPBS most commonly occurred at the distal pituitary stalk immediately above the diaphragm in 48 patients with hourglass-type adenoma. In the remaining seven patients with barrel-type adenoma, PPBS occurred in the sella or in varying sites along the pituitary stalk. Postoperatively, two patients, whose PPBS became nonvisible, developed persistent diabetes insipidus. The PPBS-nonvisible group included 14 (20%) patients. Five had hourglass-type and nine had barrel-type adenoma. Occurrence of the barrel type was marked. In these patients, four developed postoperative permanent diabetes insipidus. The diaphragm, a probable major anatomic determinant of indentation, may serve as a transportation blockade and facilitate proximal accumulation of PPBS material, as evidenced in the hourglass-type adenoma. PPBS was more commonly nonnvisible in the barrel-type adenoma. The presence of PPBS in the INH system indicates its functional maintenance in large adenomas.