title: Gamma knife stereotactic radiosurgery of Nelson syndrome.
abstract: OBJECTIVE
  Gamma knife radiosurgery (GKR) can be used as primary or adjuvant therapy for the treatment of an ACTH-producing pituitary tumor after bilateral adrenalectomy, called Nelson syndrome (NS). We have examined the effect of GKR on tumor growth and ACTH-hypersecretion, and characterized the adverse events of this treatment in patients with NS.
  
  
  METHODS
  Cross-sectional follow-up study. First, retrospective data pre- and post-GKR were collected. Patients then underwent a predefined survey including radiological, endocrinological, ophthalmological, and neurosurgical evaluation.
  
  
  METHODS
  Ten patients treated with GKR for NS after previous bilateral adrenalectomy. The mean follow-up was 7 years. No patient was lost to follow-up.
  
  
  RESULTS
  Tumor growth was stopped in all patients. The ACTH levels declined in eight patients, and normalized in one patient. There was a significant drop in ACTH levels, with a half-time of 2.8 years. No patient developed visual field defects or any other cranial nerve dysfunction as a result of treatment. Four patients started hormone substitution therapy during the follow-up period. The substitution therapy of three pituitary axes present at GKR treatment could be stopped during the same period. One patient developed a glioblastoma in the left parieto-occipital region 14 years after GKR, far from the field of treatment. As the radiation level was below 1Gy to this area, it is unlikely that the GKR treatment itself induced the malignant tumor.
  
  
  CONCLUSIONS
  In patients with NS, GKR is an effective adjuvant treatment, carrying relatively few adverse effects. Although the risk of developing a secondary neoplasia after GKR is present, it is probably extremely low.
authors.affiliation: Department of Neurosurgery, Haukeland University Hospital, 5053 Bergen, Norway. e.o.vik-mo@medisin.uio.no
authors.forename: Einar Osland
authors.initials: EO
authors.lastname: Vik-Mo
authors.forename: Marianne
authors.initials: M
authors.lastname: Øksnes
authors.forename: Paal-Henning
authors.initials: PH
authors.lastname: Pedersen
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Eyvind
authors.initials: E
authors.lastname: Rødahl
authors.forename: Frits
authors.initials: F
authors.lastname: Thorsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Schreiner
authors.forename: Sylvi
authors.initials: S
authors.lastname: Aanderud
authors.forename: Morten
authors.initials: M
authors.lastname: Lund-Johansen
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000328:Adult; D001932:Brain Neoplasms / Q000175:diagnosis; D003430:Cross-Sectional Studies; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D005909:Glioblastoma / Q000175:diagnosis; D006801:Humans; D007018:Hypopituitarism / Q000175:diagnosis / Q000517:prevention & control; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009347:Nelson Syndrome / Q000097:blood / Q000473:pathology / Q000601:surgery*; D010902:Pituitary Gland / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis / Q000517:prevention & control; D016634:Radiosurgery / Q000009:adverse effects; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000324:Adrenocorticotropic Hormone