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.
The incidence is 1 in 10,000-20,000 births 2.
Bilateral involvement is seen in approximately one-third of patients 2. The EAC may be completely absent 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 (due to forming earlier in gestation).
EAC atresia may be complicated by congenital cholesteatoma formation behind the atresia plate or in the middle ear.
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:
High resolution bony CT reformats is the modality of choice for assessing the external acoustic canal. 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
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 and prognosis
Surgical reconstruction requires formation of a new EAC and new tympanic membrane (usually with temporalis fascia). The ossicles often need to be mobilized.
- EAC exostosis (surfer's ear)
- 1. Chakeres DW, Kapila A, LaMasters D. Soft-tissue abnormalities of the external auditory canal: subject review of CT findings. Radiology. 1985;156 (1): 105-9. Pubmed citation
- 2. Gassner EM, Mallouhi A, Jaschke WR. Preoperative evaluation of external auditory canal atresia on high-resolution CT. AJR Am J Roentgenol. 2004;182 (5): 1305-12. doi:10.2214/ajr.182.5.1821305 - Pubmed citation
- 3. Patil AR, Bhalla A, Gupta P et-al. HRCT evaluation of microtia: A retrospective study. Indian J Radiol Imaging. 2012;22 (3): 188-94. doi:10.4103/0971-3026.107181 - Free text at pubmed - Pubmed citation