Third mobile window associated with suspected otosclerotic foci in two patients with an air-bone gap

J Laryngol Otol. 2011 Jan;125(1):89-92. doi: 10.1017/S0022215110001544. Epub 2010 Aug 23.


Objective: To demonstrate the need for computed tomography imaging of the temporal bone in patients clinically suspected of otosclerosis who present with atypical symptoms or audiological findings.

Case reports: We present two patients with bilateral conductive hearing loss and suspected otosclerosis in whom third mobile window lesions were revealed. The first patient had bilateral large vestibular aqueducts and bilateral fenestral otosclerotic foci. Computed tomography imaging of the second case revealed bilateral superior semicircular canal dehiscence and bilateral cochlear clefts, mimicking an otosclerotic focus in the fissula ante fenestram.

Conclusion: Differentiating third mobile window lesions from otosclerosis as the cause of a conductive hearing loss is essential before considering stapes surgery, as such treatment would be unnecessary and potentially harmful.

Publication types

  • Case Reports

MeSH terms

  • Acoustic Impedance Tests
  • Adult
  • Audiometry
  • Diagnosis, Differential
  • Female
  • Hearing Loss, Bilateral / etiology
  • Hearing Loss, Conductive / etiology
  • Humans
  • Labyrinth Diseases / complications
  • Labyrinth Diseases / diagnostic imaging*
  • Middle Aged
  • Otosclerosis / complications
  • Otosclerosis / diagnostic imaging*
  • Temporal Bone / diagnostic imaging*
  • Tomography, X-Ray Computed