title: How obliteration of petrosal air cells by vestibular schwannoma influences the risk of postoperative CSF fistula.
abstract: BACKGROUND
  For postoperative CSF-fistula prevention a better understanding of its origins and risk factors is necessary. To identify the role of the tumor growth for the risk to develop CSF-fistula we performed a retrospective analysis.
  
  
  METHODS
  519 patients between the years 2000 and 2007 had a retrosigmoidal surgical removal of vestibular schwannoma in a standardized procedure. 22 CSF-fistula-patients were chosen for evaluation. 78 patients were randomly selected as control group in four equally sized cohorts: male/female with small/large tumors. Preoperative CT-scans were analyzed regarding IAC-length, diameter of the IAC porus (IAP), tumor size and pneumatization of the posterior wall (PW) of the IAC.
  
  
  RESULTS
  The mean length of the IAC was 1.2 cm, SD 0.17. There was a significant difference between the diameter of the IAP in cases of small tumors and those of large tumors. Patients with small tumors also showed a larger fraction with visible pneumatization of the PW (34.88%) in the CT-scan than patients with large tumors (24.07%). There is a positive correlation between tumor grade and diameter of the IAP. At the same time there is an inverse correlation between tumor grade and pneumatization of the PW.
  
  
  CONCLUSIONS
  Widening of the IAC by tumor growth may leads to obliteration of air cells in the PW and therefore can be protective concerning CSF-fistula. At the same time patients with small tumors and a visible pneumatization in the PW must be expected to have a higher risk of CSF-fistula.
authors.affiliation: Department of Neurosurgery, University Hospital of Bern, 3010 Bern, Switzerland.
authors.forename: Lennart Henning
authors.initials: LH
authors.lastname: Stieglitz
authors.forename: Mario
authors.initials: M
authors.lastname: Giordano
authors.forename: Venelin Miroslav
authors.initials: VM
authors.lastname: Gerganov
authors.forename: Amir
authors.initials: A
authors.lastname: Samii
authors.forename: Madjid
authors.initials: M
authors.lastname: Samii
authors.forename: Wolf Olaf
authors.initials: WO
authors.lastname: Lüdemann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002559:Cerebrospinal Fluid Rhinorrhea / Q000453:epidemiology / Q000209:etiology*; D015331:Cohort Studies; D003392:Cranial Sinuses / Q000473:pathology*; D003399:Craniotomy; D004424:Ear Canal / Q000473:pathology; D005260:Female; D005402:Fistula / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000150:complications* / Q000473:pathology / Q000601:surgery*; D019635:Neurosurgical Procedures; D010579:Petrous Bone / Q000000981:diagnostic imaging / Q000473:pathology; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology*; D012189:Retrospective Studies; D012306:Risk; D014057:Tomography, X-Ray Computed; D055815:Young Adult