title: Hypertrophic olivary degeneration following surgical resection or gamma knife radiosurgery of brainstem cavernous malformations: an 11-case series and a review of literature.
abstract: BACKGROUND
  We describe 11 patients with hypertrophic olivary degeneration (HOD) after surgical resection or gamma knife radiosurgery for brainstem cavernous malformations. In addition, we statistically analyzed the predicting factors associated with the development of HOD.
  
  
  METHODS
  From January 2001 to May 2011, a total of 73 patients (30 in the surgical group and 43 in the radiosurgery group) with brainstem cavernous malformations were treated in our institute. Of them, 11 patients (incidence: 15 %) developed HOD with high signal intensity on T2-weighted MRI during follow-up. The predicting factors (location, size, age, and treatment method) associated with the development of HOD were statistically analyzed.
  
  
  RESULTS
  Among the 11 HOD patients, seven patients received surgical resection and four patients received gamma knife radiosurgery. Six patients had bilateral HOD and the remaining five patients had unilateral HOD. Overall HOD-associated symptoms presented in four patients, including three palatal tremors and one ataxia. In all four patients with symptoms, these symptoms disappeared incompletely within the clinical follow-up period. The size of the cavernous malformation, age of patient, and treatment methods were not significantly correlated with the development of HOD. A significantly higher incidence of HOD was associated with midbrain cavernous malformations than with pontine or medulla cavernous malformations.
  
  
  CONCLUSIONS
  HOD should be recognized as a non-infrequent complication of surgical resection or gamma knife radiosurgery within the brainstem, especially for midbrain cavernous malformations. In addition, to the best of our knowledge, this is the first report on HOD development after radiosurgery.
authors.affiliation: Department of Neurological Surgery, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Pungnap-2 dong, Songpa-gu, Seoul, 138-736, South Korea.
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Yun
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Ahn
authors.forename: Jung Cheol
authors.initials: JC
authors.lastname: Park
authors.forename: Do Hoon
authors.initials: DH
authors.lastname: Kwon
authors.forename: Byung Duk
authors.initials: BD
authors.lastname: Kwun
authors.forename: Chang Jin
authors.initials: CJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D020295:Brain Stem Neoplasms / Q000601:surgery*; D002648:Child; D005260:Female; D020786:Hemangioma, Cavernous, Central Nervous System / Q000601:surgery*; D006801:Humans; D006984:Hypertrophy; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000473:pathology*; D009847:Olivary Nucleus / Q000473:pathology*; D011183:Postoperative Complications / Q000473:pathology*; D011379:Prognosis; D016634:Radiosurgery; D012307:Risk Factors; D055815:Young Adult