title: Electrocochleography as a diagnostic and intraoperative adjunct in superior semicircular canal dehiscence syndrome.
abstract: OBJECTIVE
  To determine the electrocochleographic characteristics of ears with superior semicircular canal dehiscence (SSCD) and to examine its use for intraoperative monitoring in canal occlusion procedures.
  
  
  METHODS
  Case series.
  
  
  METHODS
  Academic medical center.
  
  
  METHODS
  Thirty-three patients (45 ears) had clinical and computed tomographic evidence of SSCD; 8 patients underwent intraoperative electrocochleography (ECoG) during superior canal occlusion; 9 patients underwent postoperative ECoG after SSCD occlusion.
  
  
  METHODS
  Diagnostic, intraoperative, and postoperative extratympanic ECoG; middle fossa or transmastoid occlusion of the superior semicircular canal.
  
  
  METHODS
  Summating potential (SP) to action potential (AP) ratio, as measured by ECoG, and alterations in SP/AP during canal exposure and occlusion.
  
  
  RESULTS
  Using computed tomography as the standard, elevation of SP/AP on ECoG demonstrated 89% sensitivity and 70% specificity for SSCD. The mean SP/AP ratio among ears with SSCD was significantly higher than that among unaffected ears (0.62 versus 0.29, p < 0.0001). During occlusion procedures, SP/AP increased on exposure of the canal lumen (mean change ± standard deviation, 0.48 ± 0.30). After occlusion, SP/AP dropped below the intraoperative baseline in most cases (mean change, -0.23 ± 0.52). All patients experienced symptomatic improvement. All patients who underwent postoperative ECoG 1 to 3 months after SSCD repair maintained SP/AP of 0.4 or lesser.
  
  
  CONCLUSIONS
  These findings expand the differential diagnosis of abnormal ECoG. In conjunction with clinical findings, ECoG may support a clinical diagnosis of SSCD. Intraoperative ECoG facilitates dehiscence documentation and allows the surgeon to confirm satisfactory canal occlusion.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Minnesota, Minneapolis, Minnesota 55455, USA. meadams@umn.edu
authors.forename: Meredith E
authors.initials: ME
authors.lastname: Adams
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kileny
authors.forename: Steven A
authors.initials: SA
authors.lastname: Telian
authors.forename: Hussam K
authors.initials: HK
authors.lastname: El-Kashlan
authors.forename: Katherine D
authors.initials: KD
authors.lastname: Heidenreich
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Mannarelli
authors.forename: H Alexander
authors.initials: HA
authors.lastname: Arts
mesh_terms: D000328:Adult; D000368:Aged; D001300:Audiometry, Evoked Response / Q000379:methods*; D005260:Female; D006314:Hearing Loss, Conductive / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007759:Labyrinth Diseases / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D012665:Semicircular Canals / Q000601:surgery*; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology