Displacement of the facial nerve course by vestibular schwannoma: preoperative visualization using diffusion tensor tractography.
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.
Taoka
Toshiaki
T
Department of Radiology, Nara Medical University, Nara, and Higashiosaka City General Hospital, Osaka, Japan. ttaoka@naramed-u.ac.jp
Hirabayashi
Hidehiro
H
Nakagawa
Hiroyuki
H
Sakamoto
Masahiko
M
Myochin
Kaoru
K
Hirohashi
Shinji
S
Iwasaki
Satoru
S
Sakaki
Toshisuke
T
Kichikawa
Kimihiko
K
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