title: Air-bone gap component of inner-ear origin in audiograms of cochlear implant candidates.
abstract: BACKGROUND
  Experimental studies have shown that creating a window in the bony cover of the cochlea and vestibular parts of the inner ear, with preservation of membranous and middle-ear functions, induces an air-bone gap (ABG). This study sought to determine if a similar mechanism explains the ABG frequently observed in audiograms of cochlear implant candidates.
  
  
  METHODS
  The study group included 47 candidates for a cochlear implant (94 ears) attending a university-affiliated tertiary medical center who had an ABG component in the audiogram in the absence of external or middle-ear abnormalities. Air- and bone-conduction thresholds on pure-tone audiometry were analyzed for 250 to 8,000 Hz and 250 to 4,000 Hz, respectively. In the 25 patients operated on during the study period, differences in the ABG and in cerebrospinal fluid (CSF) leak were compared between those with and without anomalies on computed tomography.
  
  
  RESULTS
  Imaging revealed an abnormal inner-ear structure in 46% of cases, mostly a large vestibular aqueduct, alone or combined with other cochlear or vestibular malformations. ABG was evident over high and low frequencies and was significantly larger at low frequencies and in ears with structural anomalies. A high rate of CSF leak was observed in patients with an ABG and structural anomalies imaging as well as in those with an ABG and normal imaging findings.
  
  
  CONCLUSIONS
  In cochlear implant candidates, the presence of a third window could cause an ABG because of stapes motion-induced shunting of acoustic energy outside the cochlear duct in response to air-conducted stimuli while bone conduction is preserved.
authors.affiliation: Department of Communication Sciences and Disorders, University of Haifa, Haifa, Israel. attiasj@netvision.net.il
authors.forename: Joseph
authors.initials: J
authors.lastname: Attias
authors.forename: David
authors.initials: D
authors.lastname: Ulanovski
authors.forename: Rafael
authors.initials: R
authors.lastname: Shemesh
authors.forename: Liora
authors.initials: L
authors.lastname: Kornreich
authors.forename: Benny
authors.initials: B
authors.lastname: Nageris
authors.forename: Michal
authors.initials: M
authors.lastname: Preis
authors.forename: Miriam
authors.initials: M
authors.lastname: Peled
authors.forename: Michal
authors.initials: M
authors.lastname: Efrati
authors.forename: Eyal
authors.initials: E
authors.lastname: Raveh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D001844:Bone Conduction / Q000502:physiology*; D065634:Cerebrospinal Fluid Leak; D002559:Cerebrospinal Fluid Rhinorrhea / Q000453:epidemiology / Q000209:etiology; D002648:Child; D019929:Cochlear Implantation / Q000009:adverse effects; D003054:Cochlear Implants; D007758:Ear, Inner / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006314:Hearing Loss, Conductive / Q000473:pathology / Q000503:physiopathology; D006319:Hearing Loss, Sensorineural / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed; D014723:Vestibular Aqueduct / Q000502:physiology; D055815:Young Adult