title: Posterior pituitary bright spot in large adenomas: MR assessment of its disappearance or relocation along the stalk.
abstract: 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.
authors.affiliation: 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
authors.forename: Naokatsu
authors.initials: N
authors.lastname: Saeki
authors.forename: Michihiro
authors.initials: M
authors.lastname: Hayasaka
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Murai
authors.forename: Motoo
authors.initials: M
authors.lastname: Kubota
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tatsuno
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Takanashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Uno
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iuchi
authors.forename: Akira
authors.initials: A
authors.lastname: Yamaura
mesh_terms: 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