title: Parapharyngeal space schwannomas: preoperative imaging determination of the nerve of origin.
abstract: OBJECTIVE
  To determine if preoperative radiographic cross-sectional images can predict the nerve of origin of a parapharyngeal schwannoma and, specifically, whether it originates from the vagus nerve or the cervical sympathetic chain.
  
  
  METHODS
  A retrospective review.
  
  
  METHODS
  Academic medical center.
  
  
  METHODS
  The study population comprised 12 patients who underwent surgical resection of schwannomas of the parapharyngeal space. The nerve of origin was identified based on operative findings and postoperative physical examinations. Of the 12 patients, 11 underwent preoperative magnetic resonance imaging and 1 underwent preoperative contrast-enhanced computed tomography. A CAQ (Certificate of Added Qualification)-certified neuroradiologist reviewed the imaging studies, blinded to the surgically determined nerve of origin. For each case, it was predicted whether the tumor arose from the vagus nerve or sympathetic chain based on the location of the schwannoma with reference to the carotid sheath vessels.
  
  
  METHODS
  Identification of the nerves of origin using the displacement of vessels as a marker.
  
  
  RESULTS
  At the time of operation, it was determined that 5 patients (42%) had schwannomas from the cervical sympathetic chain and 7 patients (58%) had schwannomas of the cervical vagus nerve. By imaging, the nerve of origin was successfully determined in 4 of 5 cases of sympathetic chain schwannoma (80%) and in 7 of 7 cases of vagal nerve schwannoma (100%). Schwannomas of the cervical sympathetic chain were found to displace both the carotid and jugular vessels without separating them. Vagal nerve schwannomas were found to separate the carotid arteries from the internal jugular vein. A vagal nerve schwannoma may also displace the sheath vessels posteriorly, without splaying them.
  
  
  CONCLUSIONS
  Carotid and jugular vessel displacement, as determined by cross-sectional imaging, can predict the likely nerve of origin of a parapharyngeal space schwannoma. This determination allows for effective preoperative counseling regarding the expected sequelae of surgical resection.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, University of California, San Francisco, 400 Parnassus Ave, Seventh Floor, Box 0342, San Francisco, CA 94143, USA. dsaito@ohns.ucsf.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Saito
authors.forename: Christine M
authors.initials: CM
authors.lastname: Glastonbury
authors.forename: Ivan H
authors.initials: IH
authors.lastname: El-Sayed
authors.forename: David W
authors.initials: DW
authors.lastname: Eisele
mesh_terms: D000293:Adolescent; D000328:Adult; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D005728:Ganglia, Sympathetic / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000473:pathology* / Q000601:surgery; D010610:Pharyngeal Neoplasms / Q000473:pathology* / Q000601:surgery; D011300:Preoperative Care; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014630:Vagus Nerve / Q000473:pathology
chemical_list: D003287:Contrast Media