title: Collision tumor of the facial nerve:  a synchronous seventh nerve schwannoma and neurofibroma.
abstract: OBJECTIVE
  To report a novel case of a collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma.
  
  
  METHODS
  Clinical capsule report.
  
  
  METHODS
  Tertiary academic referral center.
  
  
  METHODS
  A 29-year-old woman with a 2-year history of an asymptomatic enlarging left infraauricular mass and normal FN function presented to a tertiary care referral center. Computed tomography and magnetic resonance imaging demonstrated a cystic lesion in the deep portion of the parotid gland extending into the stylomastoid foramen.
  
  
  METHODS
  The patient underwent superficial parotidectomy, and a cystic parotid mass was found to be intrinsic to the intraparotid facial nerve. A portion of the mass was biopsied, and intraoperative frozen section pathology was consistent with a neurofibroma. A mastoidectomy with FN decompression was then performed until a normal-appearing segment was identified just proximal to the second genu. After biopsy, proximal facial nerve stimulation failed to elicit evoked motor potentials, and en bloc resection was performed.
  
  
  RESULTS
  Final pathology demonstrated a schwannoma involving the mastoid segment and a neurofibroma involving the proximal intraparotid facial nerve.
  
  
  CONCLUSIONS
  We report the first case of a facial nerve collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma. Benign FN sheath tumors of the parotid gland are rare but should be considered in the differential diagnosis of a parotid mass.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, Minnesota, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Gross
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Carlson
authors.forename: Colin L
authors.initials: CL
authors.lastname: Driscoll
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Moore
mesh_terms: D000328:Adult; D003390:Cranial Nerve Neoplasms / Q000473:pathology* / Q000556:secondary / Q000601:surgery; D019054:Evoked Potentials, Motor / Q000502:physiology; D005155:Facial Nerve Diseases / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008416:Mastoid / Q000473:pathology; D009442:Neurilemmoma / Q000473:pathology* / Q000556:secondary / Q000601:surgery; D009455:Neurofibroma / Q000473:pathology* / Q000601:surgery; D013506:Otologic Surgical Procedures / Q000379:methods; D010307:Parotid Neoplasms / Q000473:pathology; D014057:Tomography, X-Ray Computed