Dehiscence of bone overlying the superior canal as a cause of apparent conductive hearing loss

Otol Neurotol. 2003 Mar;24(2):270-8. doi: 10.1097/00129492-200303000-00023.


Objective: To identify patients with superior semicircular canal dehiscence and apparent conductive hearing loss and to define the cause of the air-bone gap.

Study design: Prospective study of patients with superior canal dehiscence. SETTING Tertiary referral center.

Patients: Vestibular and/or auditory findings indicative of canal dehiscence and demonstration of superior canal dehiscence on computed tomography of the temporal bone.

Intervention: Vestibular-evoked myogenic potentials, three-dimensional eye movement recordings, and surgical resurfacing of the superior canal.

Outcome measure: Association of superior canal dehiscence with an air-bone gap on audiometry.

Results: Four patients with dehiscence of bone overlying the superior canal were found to have air-bone gaps in the affected ears that were greatest at lower frequencies and averaged 24 +/- 7 dB over the frequency range of 250 to 4,000 Hz. Three of these patients had undergone stapedectomy before the identification of superior canal dehiscence. The air-bone gap was unchanged postoperatively. Each patient had an intact vestibular-evoked myogenic potential (VEMP) response from the affected ear, a finding that would not have been expected based on a middle ear cause of conductive hearing loss. One patient underwent resurfacing of the superior canal through a middle fossa approach. Postoperatively, his vestibular symptoms were relieved, and his air conduction thresholds were improved by 20 dB.

Conclusions: Superior canal dehiscence can result in apparent conductive hearing loss. The third mobile window created by the dehiscent superior canal results in dissipation of acoustic energy and is a cause of inner ear conductive hearing loss.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Aged
  • Audiometry, Pure-Tone
  • Auditory Threshold / physiology
  • Bone Conduction / physiology
  • Eye Movements / physiology
  • Female
  • Hearing Loss, Conductive / diagnosis
  • Hearing Loss, Conductive / physiopathology*
  • Humans
  • Male
  • Middle Aged
  • Perceptual Masking / physiology
  • Prospective Studies
  • Reflex, Vestibulo-Ocular / physiology
  • Semicircular Canals / diagnostic imaging
  • Semicircular Canals / physiopathology*
  • Temporal Bone / diagnostic imaging
  • Temporal Bone / pathology*
  • Time Factors
  • Tomography, X-Ray Computed