Conductive hearding loss due to facial nerve aberrant canal and oval window dysplasia

Case contributed by Fabien Ho


Conductive hearing loss on the right side.

Patient Data

Age: 25 years
Gender: Female

An abnormal course of the facial nerve canal, overlying stapes and oval window:

  • blue arrow: expected location of the facial nerve canal, tympanic portion, below the lateral semicircular canal, and superior and lateral to the oval window
  • orange arrow: actual aberrant location

The 1st and 3rd portions of the facial nerve canal are normal.

No external ear anomalies, no ossicular chain ankylosis nor disruption, no inflammatory changes, no internal ear anomalies which could have caused conductive hearing loss are seen.

There is associated oval window and stapes dysplasia.

Case Discussion

Facial nerve overlying the stapes footplate is a rare cause of congenital conductive hearing loss.
Stapes and oval window dysplasia are often associated and can be explained on an embryologic basis.

Possible differential diagnoses leading to misdiagnose of oval window dysplasia:

  • Fenestral otosclerosis: different clinical history and a different evolutive course on imaging
  • tympanosclerosis due to inflammatory changes: inflammatory changes are the main findings

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