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External auditory canal atresia

External auditory canal atresia (EACA) is characterised by complete or incomplete bony atresia of the external auditory canal (EAC) and, especially when seen in the setting of an associated syndrome, a dysplastic auricle and abnormal middle ear cavity.

Demographics and clinical presentation

The incidence is 1 in 10,000-20,000 births 2, with associated abnormal external ear and conductive hearing loss present from birth. Bilateral involvement is seen in approximately 1/3 of patients 2

Associations

Although frequently isolated (in which case the abnormality is less severe and isolated to the EAC) a number of syndromes are associated with external auditory canal atresia 2. These include:

Radiographic features

The EAC may be completely absent (see cases 1 and 2) or incompletely atretic with further narrowing contributed to by soft tissue bands.

Findings in the middle ear are variable and the inner ear and inner auditory canal are typically normal. 

EAC atresia may be complicated by congenital cholesteatoma formation behind the atresia plate or in the middle ear.

A number or key points should be looked for and specifically mentioned in reports as it impacts on surgical reconstruction.

  • middle ear cavity volume: a width of greater than 3 mm is usually needed for successful surgery
  • ossicles 2
    • malleus: usually has a rudimentary handle (as there is no normal tympanic membrane)
    • incudomallear joint: usually normal
    • incus: usually normal
    • stapes: important to note as an abnormal or absent stapes needs to be replaced with a prosthetic
  • inner ear structure
    • both the oval and round window need to be present for successful surgery
  • course of internal carotid artery, and location of the jugular bulb: if abnormal can be hazardous during surgery
  • course of facial nerve: often abnormally anterior and can be damaged during reconstruction

Treatment

Surgical reconstruction requires formation of a new EAC and new tympanic membrane (usually with temproalis facia). The ossicles often need to be mobilized.

 

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