title: Identification of cranial nerves near large vestibular schwannomas using superselective diffusion tensor tractography: experience with 23 cases.
abstract: BACKGROUND
  The preservation of the facial nerve (FN) and acoustic function in large vestibular schwannoma (VS) surgery is challenging because of nerve course uncertainties and morphological deviations. Preoperative diffusion tensor tractography (DTT) has been proposed to predict the FN location. This study was conducted to evaluate the effectiveness of this technique for identifying the FN, cochlear nerve (CN) and trigeminal nerve (TN) in large VSs.
  
  
  METHODS
  The study included 23 consecutive patients with VS of Hannover classification T3b to T4b from November 2013 through May 2014. Diffusion tensor images and anatomical images were acquired. The DTT images of the cranial nerves were extracted before surgery for each patient to determine the relationships of these nerves with the tumor. The results were then validated during the tumorectomy.
  
  
  RESULTS
  In 21 (91.30%) patients, the location of the FN on the DTT images agreed with the intraoperative findings, including in 2 patients in whom the FN passed through the interface between the parenchyma and the cystic changes and in 3 patients with a membranoid FN. The CN or fibers of unclear function were observed on DTT images in four patients with functional hearing. One penetrating fiber of unknown function was effectively constructed. The TN was accurately detected on the DTT images for all patients.
  
  
  CONCLUSIONS
  DTT effectively revealed the location of the FN, including cases in which the FN was membranoid or passed through the interface between an area exhibiting cystic changes and the tumor nodule. Fibers aside from the FN and the TN were revealed by DTT in patients who retained functional hearing. Penetrating fibers were also found using DTT. This technique can be useful during VS resection.
authors.affiliation: Department of Neurosurgery, Xuan Wu Hospital, Capital Medical University, No. 45 Changchun Street, Xuanwu District, Beijing, 100053, China.
authors.forename: Peng-Hu
authors.initials: PH
authors.lastname: Wei
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Qi
authors.forename: Ge
authors.initials: G
authors.lastname: Chen
authors.forename: Peng
authors.initials: P
authors.lastname: Hu
authors.forename: Ming-Chu
authors.initials: MC
authors.lastname: Li
authors.forename: Jian-Tao
authors.initials: JT
authors.lastname: Liang
authors.forename: Hong-Chuan
authors.initials: HC
authors.lastname: Guo
authors.forename: Feng
authors.initials: F
authors.lastname: Ling
authors.forename: Yu-Hai
authors.initials: YH
authors.lastname: Bao
mesh_terms: D000328:Adult; D003056:Cochlear Nerve / Q000033:anatomy & histology* / Q000502:physiology; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005154:Facial Nerve / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D014276:Trigeminal Nerve / Q000033:anatomy & histology* / Q000502:physiology