External Auditory Canal Atresia
- Author: Rahul K Shah; Chief Editor: Glenn C Isaacson, MD, FACS, FAAP more...
Background
External auditory canal atresia (EACA) is a rare congenital disorder. Accurate counseling and referral for these children and their families demands an appreciation of the range of management options and indications for intervention. This article reviews the history, etiology, and epidemiology of EACA, as well as the clinical care of children with this condition.
Unilateral auditory canal atresia is shown in the image below.
Photograph of the right ear in a patient with unilateral external auditory canal atresia is shown. Note the relatively normal pinna and thumb print concha. EACA was first described in Western medicine by Paulus of Aegina in the seventh century AD. Paulus recommended simple incision for opening the atresia. Later, physicians used a hot iron probe to maintain canal patency after incising the atresia. The first operation to correct an atresia of the external auditory canal (EAC) was performed in 1882 by Kiesselbach. Unfortunately, the operation left the child with a facial nerve paralysis. In 1914, Page reported on a series of 8 patients who underwent operation. Of these 8 patients, 5 had a subjective improvement in their hearing after surgery.
In the early 20th century, techniques for correction of the atretic external canal have involved opening the antrum and aditus of the ear and lining the cavities with a skin graft. In these surgeries, the atretic bony plate was untouched, and the resulting hearing improvement was poor. In the past 50 years, improved radiologic and audiologic assessments coupled with improvements in surgical technology, such as the operating microscope and facial nerve monitoring, have resulted in good surgical success rates for properly chosen patients with EACA.
The future of medical and surgical interventions for patients with EACA is exciting and includes such novel approaches as computer-aided surgery as well as critical reviews of past surgical results, with further attempts to increase success rates and minimize morbidity.
Pathophysiology
The EAC is comprised of medial bony and lateral cartilaginous portions. The bony component changes from half of the length of the tubular EAC in children to two thirds of the length of the tubular EAC in adults.
The lateral soft tissue portion of the EAC begins to form at 26-28 weeks' gestation, when the epithelial plug arising from the first branchial cleft begins to canalize. During the sixth month of development, the medial bony portion is created out of the temporal bone's mesenchymal condensation. As canalization occurs, the mastoid separates from the mandible and grows posteriorly and inferiorly. The posteroinferior growth of the mastoid brings the facial nerve from the middle ear and brings the facial nerve and middle ear into its position at birth (ie, posterior and inferior to the EAC).
Congential atresia of the EAC is caused by a failure of canalization of the epithelial plug portion of the first branchial cleft. Persistence of the tympanic ring results in a bony atresia plate at the level of the tympanic membrane. Ossicular malformations may be seen as they arise from the first branchial cartilage (ie, Meckel cartilage).
Failure of the EAC to canalize means that sound cannot reach the tympanic membrane; thus, a conductive hearing loss results (see images below). Concomitant ossicular malformations may result in additional conductive hearing loss. In addition, 11-47% of patients also have a sensorineural hearing loss in the affected ear.
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. EACA may be seen with microtia (ie, maldevelopment of the external ear). The auricle develops from ectodermal condensations and mesodermal condensations (referred to as the hillocks of His) at 5 weeks' gestation.
Case reports have detailed duplication anomalies of the first branchial cleft occurring in conjunction with a congenital aural atresia. The implication for the evaluating physician is to keep in mind that EACA and duplication anomalies can be present in the same patient, and both may need to be simultaneously addressed (surgically).
Epidemiology
Frequency
United States
According to Jahrsdoerfer, the incidence of ear malformations in New York City from 1952-1962 was 1 in 5800 births.[1] In one year of this study, the incidence of EACA was 1 in 8000 births.
International
EACA is rare in persons with a normal pinna. The incidence of EACA with concurrent microtia is 1 in 10,000-20,000 live births. Unilateral EACA is 3-6 times more likely to occur than bilateral atresia. The right ear is more often involved than the left ear. Family histories positive for EACA are noted in 14% of patients.
Mortality/Morbidity
Intervention to treat bilateral EACA is important for hearing and language development. Social stigma may be experienced because of cosmetic or developmental issues, especially as grade school begins.
- Otitis media (OM) is a common pediatric diagnosis that is difficult to identify and manage in children with EACA. EACA complicates the diagnosis of OM. Symptoms of pain, fever, irritability, and worsening hearing loss or imbalance warrant evaluation. The contralateral ear may also show otitis. Oral antibiotics may be started presumptively. Although CT scanning is not a routine screening test for these children, it reveals soft tissue density in the middle ear cleft. Clinical management of OM is not significantly different, and complications of mastoiditis, facial nerve palsy, and intracranial complications must be monitored.
- Once complications have been encountered, CT scanning to examine the interrelationships of the otologic structures is certainly warranted. OM refractory to oral antibiotics may require insertion of tympanostomy tubes. However, these ventilation tubes should only be inserted in the normal ear and not the affected contralateral ear. The need for middle-ear ventilation to treat OM may prompt earlier correction of EACA as the diagnosis is made earlier. Recurrent OM is an age-limited problem that resolves with time.
- Canal cholesteatoma (epithelial inclusion cyst) may occur medial to the atretic ear canal. Canal cholesteatomas may be identified radiographically before symptoms begin because of widening of the EAC. Patients with infection of the cholesteatoma present with pain and fever. Treatment is primarily surgical with adjunctive use of oral or systemic antibiotics.
- Traditionally, unilateral EACA was not believed to limit children's language. Recently, therapies for hearing loss have appreciated the importance of bilateral hearing for optimal speech and language development. In addition to long-term development, bilateral hearing is important for hearing in a noisy environment (eg, in groups, with background noise) and for sound localization (eg, knowing from which side a car is approaching).
Sex
EACA occurs more often in males than in females.
Age
EACA occurs with a normal pinna or with an abnormal pinna (ie, concomitant microtia). When the atresia occurs in the setting of a normal pinna, the average age of diagnosis is 2.5 years. However, when EACA occurs with abnormal development of the pinna, the average age of diagnosis is 3.5 years.
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