title: Preoperative versus postoperative role of vestibular-evoked myogenic potentials in cerebellopontine angle tumor.
abstract: OBJECTIVE
  Vestibular-evoked myogenic potential (VEMP) examination was performed on patients with a cerebellopontine angle (CPA) tumor to evaluate its clinical role.
  
  
  METHODS
  Patients with a CPA tumor were subjected to caloric test and VEMP examination. Follow-up study was performed 1 year after the surgery.
  
  
  RESULTS
  Six (69%) of the 9 tumors did not exhibit either caloric response or VEMP on the lesioned side. Three patients received tumor excision and all tumors involved both the superior and inferior vestibular nerves. Two (22%) of the 9 tumors had normal caloric responses but no VEMP. One underwent surgical excision, and the tumor originated from the inferior vestibular nerve. In the follow-up study, only 1 patient with epidermoid cyst presented complete recovery of caloric response and VEMP, whereas in the other 3 patients with vestibular schwannoma, the responses were all absent persistently.
  
  
  CONCLUSIONS
  Before surgery, VEMP test can be used to predict the nerve of origin and to formulate the best surgical approach. After surgery, VEMP test can be used to define the nature of the tumor (compressing or infiltrating the nerve) and disclose the residual function of the inferior vestibular nerve.
authors.affiliation: Department of Otolaryngology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Cheng-Wei
authors.initials: CW
authors.lastname: Chen
authors.forename: Yi-Ho
authors.initials: YH
authors.lastname: Young
authors.forename: Ham-Min
authors.initials: HM
authors.lastname: Tseng
mesh_terms: D000328:Adult; D001301:Audiometry, Pure-Tone; D002150:Caloric Tests; D002528:Cerebellar Neoplasms / Q000175:diagnosis* / Q000601:surgery*; D002530:Cerebellopontine Angle / Q000473:pathology*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000175:diagnosis* / Q000601:surgery*; D011184:Postoperative Period; D011300:Preoperative Care; D011446:Prospective Studies; D012680:Sensitivity and Specificity