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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Saeki
Naokatsu
N
Department of Neurological Surgery, Chiba University School of Medicine, Inohana 1-8-1, Chuo-ku, Chiba 260-8670, Japan. saeki@med.m.chiba-u.ac.jp
Hayasaka
Michihiro
M
Murai
Hisayuki
H
Kubota
Motoo
M
Tatsuno
Ichiro
I
Takanashi
Jun-Ichi
J
Uno
Takashi
T
Iuchi
Toshihiko
T
Yamaura
Akira
A
D000236:Adenoma / Q000473:pathology* / Q000601:surgery; D000328:Adult; D016009:Chi-Square Distribution; D003919:Diabetes Insipidus / Q000209:etiology; D005260:Female; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000473:pathology* / Q000601:surgery