title: Displacement of the facial nerve course by vestibular schwannoma: preoperative visualization using diffusion tensor tractography.
abstract: OBJECTIVE
  To preoperatively visualize the course of the facial nerve, which is displaced by vestibular schwannoma, using diffusion tensor (DT) tractography, and to evaluate the agreement with surgical findings.
  
  
  METHODS
  The subjects were eight patients with vestibular schwannoma who had undergone removal surgery. DT MR images were obtained and tracts that were considered to represent the facial nerve were constructed. We assessed the success rate for tract construction and evaluated the agreement between tractography findings and surgery.
  
  
  RESULTS
  We obtained a tract that connected the internal auditory meatus and brainstem, and was considered to represent the facial nerve in seven of eight cases. The course of the constructed tract agreed with surgical findings in five of these seven cases. One exception was a case in which the tumor was too large to enable intraoperative observation of the facial nerve; however, the facial nerve appeared to be displaced anteriorly at intracapsular resection, in agreement with tractography. In the other case, the schwannoma was mostly cystic.
  
  
  CONCLUSIONS
  Tractographs constructed using MR tensor images enabled us to identify tracts considered to represent facial nerves. We consider DT tractography to be a useful tool for preoperatively predicting facial nerve displacement in vestibular schwannoma.
authors.affiliation: Department of Radiology, Nara Medical University, Nara, and Higashiosaka City General Hospital, Osaka, Japan. ttaoka@naramed-u.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taoka
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Hirabayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Masahiko
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Kaoru
authors.initials: K
authors.lastname: Myochin
authors.forename: Shinji
authors.initials: S
authors.lastname: Hirohashi
authors.forename: Satoru
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Toshisuke
authors.initials: T
authors.lastname: Sakaki
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kichikawa
mesh_terms: D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005154:Facial Nerve / Q000473:pathology*; D020220:Facial Nerve Injuries / Q000473:pathology / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009442:Neurilemmoma / Q000473:pathology* / Q000601:surgery; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome