title: Morphological changes of vestibular schwannomas after radiosurgical treatment: pitfalls and diagnosis of failure.
abstract: BACKGROUND
  Evaluate the morphological changes following radiosurgery in order to better define failure parameters.
  
  
  METHODS
  332 non-neurofibromatosis type 2 vestibular schwannomas not previously treated surgically or radiosurgically were subjected to Gamma Knife radiosurgery between 1992 and 2004 at the Gamma Knife Center in Marseille with at least three sequential MRI scans after radiosurgery. Five length measurements were systematically obtained.
  
  
  RESULTS
  Mean follow-up was 4.6 years. Transient loss of contrast enhancement appeared in 213 patients (68%). Significant increase was present at 6 months in 178 patients. In 74 patients, the volume at 3 years was still higher than on the day of radiosurgery but remained stable. Failure occurred in 16 patients. Most showed progressive growth at all MRI controls after radiosurgery but late failure after initial response was possible.
  
  
  CONCLUSIONS
  Sequential MRI scans after radiosurgery are necessary. A progressive and continuous growth at 3 years is essential to make diagnosis of failure.
authors.affiliation: Service de Neurochirurgie, Hôpital Sainte-Marguerite, bFédération d'Oto-Rhino-Laryngologie, et cService de eurochirurgie Stéréotaxique et Fonctionnelle, Hôpital la Timone, Assistance Publique-Hôpitaux de Marseille, arseille, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Delsanti
authors.forename: Pierre-Hughes
authors.initials: PH
authors.lastname: Roche
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Thomassin
authors.forename: Jean
authors.initials: J
authors.lastname: Régis
mesh_terms: D015331:Cohort Studies; D003951:Diagnostic Errors; D005260:Female; D005602:France; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D017410:Practice Guidelines as Topic; D016634:Radiosurgery; D012189:Retrospective Studies; D013997:Time Factors; D017211:Treatment Failure; D047368:Tumor Burden