External Auditory Canal Atresia Workup

• Localization tests (eg, lacrimation, salivation, gustatory testing) for facial nerve function have a limited role.
• Genetic testing for chromosomal or other genetic defects is not currently routine for nonsyndromic external auditory canal atresia (EACA). However, the likelihood of future work to identify genetic etiologies for craniofacial disorders makes the discussion of genetic etiologies and banking of blood important.

Radiologic imaging is critical for accurate counseling of the family and surgical decision making.

• CT scanning (without contrast) of the temporal bones in axial and coronal direct sections (not reconstructions) obtained in thin 1-mm cuts is required (see the following images). CT scan in the axial plane of right unilateral external auditory canal atresia (EACA) is shown. The right external auditory canal (EAC), to the left of this photo, is not developed compared to the normally developed left EAC. The image is slightly tilted in the horizontal plane. CT scan showing unilateral auditory canal atresia in coronal section of the right ear. No ear canal is seen to the left of this picture (patient's right).
• Radiologic assessment as close to the planned operation as possible, usually within 3-6 months of surgery, is ideal. Several scans may be obtained to determine the relationship to the temporomandibular joint and monitor development of critical structures, specifically mastoid tip and middle-ear structures. Some surgeons prefer to perform CT scanning soon after birth to ensure that no congenital cholesteatoma is present. This was demonstrated in a rare case report of a congenital cholesteatoma in a patient with congential aural atresia.^[2]
• CT scan review focuses on external-ear, middle-ear, and inner-ear development and on the boundaries of the EACA, specifically the middle cranial fossa superiorly, the carotid artery and jugular bulb, and the intratemporal fossa.
• Relation of the pinna to the EACA and temporomandibular joint can be appreciated.
• Development of the ossicles and presence of a cholesteatoma and possibility of middle ear fluid are evaluated. Mastoid development and facial nerve location are also assessed.

• Literature based on children with OM has shown that parents and physicians are not able to reliably predict hearing loss due to ear infections. Objective audiologic assessment is therefore required.

  • Audiologic evaluation (see images shown below) with age-appropriate audiometric evaluation by an audiologist with pediatric expertise is optimal. Periodic testing at regular intervals is best. Audiogram of a 5-year-old girl with right unilateral external auditory canal atresia (EACA) is shown. The audiogram demonstrates a right conductive hearing loss seen by the difference in hearing levels between the red triangles and the black brackets. The left ear hearing levels shown by the blue line are normal. This child demonstrated good function at home and in preschool and did not require intervention at this point. Audiogram 1 year later of the same child as in the image above. Her functioning in kindergarten continues to be excellent, and she has noticed hearing improvement at home. Her physical examination shows a pinpoint opening at the external auditory canal (EAC) now, and this audiogram confirms improved hearing in the right ear compared to the prior audiogram (see image above). Her right conductive hearing loss is shown by the distance between the black brackets and the red triangles.
  • Behavioral testing is possible when children are able to sit upright and turn to stimuli, usually around 6 months of age.
  • Auditory brainstem response (ABR) audiometry may be used in children unable to undergo behavioral testing and for validation of abnormal behavioral results.
• Formal vestibular testing may be required when symptoms of dizziness warrant. Sheykholeslami et al (2005) used vestibular-evoked myogenic potentials (VEMPs), a promising vestibular evaluation, to test children with bilateral EACA.^[3] The VEMP in neonates with audio-vestibular problems was successfully obtained and generated information about vestibular function. The advantage in testing vestibular function in this cohort of patients is that care and rehabilitative potential can be improved.
• Facial nerve testing using electroneuronography (ENog) or electromyography (EMG) may be indicated for weak or nonfunctioning facial nerves, particularly before surgery is planned, and occasionally after surgery.
• Note that audiologic function most closely correlates with formation and development of the oval/round windows and ossicular development.^[4] Inner ear anomalies occur with aural atresia, and, as such, care should be taken to identify these in patients.^[5]

Many classification systems exist for the staging of the degree of atresia of the EAC. The more commonly used systems are noted below. All these categorize the development and relations of the external canal, the tympanic membrane, middle ear development, and ossicular structures.

• Altmann classification

  • Type I
    • Small external canal
    • Hypoplastic temporal bone/tympanic membrane
    • Normal/contracted middle ear
    • Normal/malformed ossicles
  • Type II
    • Absent external canal with atretic plate
    • Small middle ear
    • Fixed/malformed malleus and incus
  • Type III
    • Absent external canal
    • Contracted/absent middle ear
    • Present/absent ossicles
• De la Cruz classification

  • Minor
    • Mastoid pneumatization normal
    • Normal oval window
    • Normal inner ear
    • Facial nerve/oval window relationship acceptable
  • Major
    • Mastoid poorly pneumatized
    • Oval window absent or abnormal
    • Inner ear malformations
    • Facial nerve aberration
• Ombredanne classification

  • Minor
    • Normal/small external canal
    • Normal middle ear
    • Fixed/deformed ossicles
    • Microtia (possibly)
  • Major
    • External canal and tympanic membrane absent
    • Aberrant/dehiscent facial nerve
    • Microtia