External auditory canal atresia
Updates to Article Attributes
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 presentationEpidemiology
The incidence is 1 in 10,000-20,000 births 2, with associated abnormal .
Clinical presentation
Abnormal appearance of the external ear and conductive hearing loss present from birth.
Pathology
Bilateral involvement is seen in approximately 1/3one-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.
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
CT
The EAC may be completely absent (see cases 1 and 2) or incompletely atretic with further narrowing contributed to by soft tissue bands.
Findings inHigh resolution bony CT reformats is the middle ear are variable andmodality of choice for assessing the inner ear and inner auditoryexternal acoustic canal are typically normal.
EAC atresia may be complicated by congenital cholesteatoma formation behind the atresia plate or in the middle ear.
A 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)
-
incudomallearincudomalleolar 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 and prognosis
Surgical reconstruction requires formation of a new EAC and new tympanic membrane (usually with temproalis faciatemporalis fascia). The ossicles often need to be mobilized.
Differential diagnosis
- EAC exostosis (surfer's ear)
-<p><strong>External auditory canal atresia (EACA)</strong> is characterised by complete or incomplete bony atresia of the <a href="/articles/external-auditory-canal">external auditory canal (EAC)</a> and, especially when seen in the setting of an associated syndrome, a dysplastic <a href="/articles/external-ear">auricle</a> and abnormal <a href="/articles/middle-ear-cavity">middle ear cavity</a>.</p><h4>Demographics and clinical presentation</h4><p>The incidence is 1 in 10,000-20,000 births <sup>2</sup>, with associated abnormal external ear and conductive hearing loss present from birth. Bilateral involvement is seen in approximately 1/3 of patients <sup>2</sup>. </p><h5>Associations</h5><p>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 <sup>2</sup>. These include:</p><ul>- +<p><strong>External auditory canal atresia (EACA)</strong> is characterised by complete or incomplete bony atresia of the <a href="/articles/external-auditory-canal">external auditory canal (EAC)</a> and, especially when seen in the setting of an associated syndrome, a dysplastic <a href="/articles/external-ear">auricle</a> and abnormal <a href="/articles/middle-ear-cavity">middle ear cavity</a>.</p><h4>Epidemiology</h4><p>The incidence is 1 in 10,000-20,000 births <sup>2</sup>.</p><h4>Clinical presentation </h4><p>Abnormal appearance of the <a href="/articles/external-ear">external ear</a> and <a href="/articles/conductive-hearing-loss">conductive hearing loss</a> present from birth.</p><h4>Pathology</h4><p>Bilateral involvement is seen in approximately one-third of patients <sup>2</sup>. The EAC may be completely absent or incompletely atretic with further narrowing contributed to by soft tissue bands.</p><p>Findings in the middle ear are variable and the inner ear and inner auditory canal are typically normal (due to forming earlier in gestation). </p><p>EAC atresia may be complicated by <a href="/articles/congenital-cholesteatoma">congenital cholesteatoma</a> formation behind the atresia plate or in the middle ear.</p><h5>Associations</h5><p>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 <sup>2</sup>:</p><ul>
-</ul><h4>Radiographic features</h4><p>The EAC may be completely absent (see cases 1 and 2) or incompletely atretic with further narrowing contributed to by soft tissue bands.</p><p>Findings in the middle ear are variable and the inner ear and inner auditory canal are typically normal. </p><p>EAC atresia may be complicated by <a href="/articles/congenital-cholesteatoma">congenital cholesteatoma</a> formation behind the atresia plate or in the middle ear.</p><p>A number or key points should be looked for and specifically mentioned in reports as it impacts on surgical reconstruction.</p><ul>- +</ul><h4>Radiographic features</h4><h5>CT</h5><p>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.</p><ul>
-<li>incudomallear joint: usually normal</li>- +<li>incudomalleolar joint: usually normal</li>
-<li>course of facial nerve: often abnormally anterior and can be damaged during reconstruction</li>-</ul><h4>Treatment</h4><p>Surgical reconstruction requires formation of a new EAC and new tympanic membrane (usually with <a href="/articles/temproalis-facia">temproalis facia</a>). The ossicles often need to be mobilized.</p><p> </p>- +<li>course of <a href="/articles/facial-nerve">facial nerve</a>: often abnormally anterior and can be damaged during reconstruction</li>
- +</ul><h4>Treatment and prognosis</h4><p>Surgical reconstruction requires formation of a new EAC and new tympanic membrane (usually with <a href="/articles/temproalis-facia">temporalis fascia</a>). The ossicles often need to be mobilized.</p><h4>Differential diagnosis</h4><ul><li>
- +<a href="/articles/exostosis-of-the-external-auditory-canal">EAC exostosis</a> (surfer's ear)</li></ul>
References changed:
- 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. <a href="http://dx.doi.org/10.4103/0971-3026.107181">doi:10.4103/0971-3026.107181</a> - <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3624742">Free text at pubmed</a> - <a href="http://www.ncbi.nlm.nih.gov/pubmed/23599567">Pubmed citation</a><span class="auto"></span>
Image 7 CT (bone window) ( create )
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