What Is Aural Atresia?
Aural atresia refers to absence of the ear canal. It is a birth defect that may occur on its own or in the presence of other defects. It frequently occurs with other defects of the ear. The auricle (external ear), ossicles (hearing bones), and cochlea (inner ear) all may be deformed or absent. It may occur in both ears.
What Causes Aural Atresia?
Aural atresia occurs in 1 in 10,000 live births. It is more common in boys. It more commonly only effects one ear.
Although the exact cause is not known, when the fetus is developing something causes the ear to stop growing before it is complete. The earlier the arrest in development, the more severe the defect. Deformities of the auricle (microtia), ossicles, and facial nerve are common. Deformity of the cochlea is much less common.
Although it usually occurs in isolation, atresia may be a part of certain syndromes of facial development such as Treacher Collins syndrome, branchial-oto-renal syndrome or others.
What Symptoms Does Aural Atresia Cause?
The effect that atresia has on hearing depends on the severity of a given case. For example, in a mild case of only one ear, there will be a unilateral conductive hearing loss. This is essentially like have an ear plug in one ear and normal hearing in the other. However, in a severe bilateral case with cochlear deformities, profound hearing impairment may be present.
In order to evaluate aural atresia, the hearing impairment is typically the first thing evaluated. Hearing screening will detect a hearing loss in the affected ear. Further hearing tests such as auditory brainstem response and behavior audiometry will delineate the severity.
What Options Are Available to Treat Aural Atresia?
Treatment is needed to optimize hearing function and the cosmetic appearance of the ear. If the other ear is normal, simply relying on it without treating the atresia is a reasonable option. If the atretic ear has a functioning inner ear, a bone conducting hearing aid is an option. Surgery to create and ear canal and working ossicles attempts to restore the hearing function by rebuilding the anatomy of the ear.
Prior to making a decision about which option is best the surgeon and patient have to consider two things. First, is a cosmetic procedure needed? If so, the repair of the ear canal should occur after the cosmetic procedure. Second, are the ossicles in condition for repair. A CT scan will allow the surgeon to determine if reconstruction of the ear canal and ossicles is a reasonable option and if there is danger to the facial nerve.
Cosmetic procedures usually occur after 5 years of age. This is because rib cartilage is used to rebuild the external ear and it has to grow to sufficient size. Cosmetic procedures are done first due to the extensive nature of grafting needed. These procedures rely heavily on the undisturbed blood supply. If repair of the ear canal is done, the blood supply becomes less reliable to support a cosmetic graft.
An alternative to plastic surgery is a prosthetic ear. The prosthesis is a silicon mirror image of the opposite ear. It is held in place by surgically placed magnets. Cosmetic outcome is very good. A prosthetic ear is used in combination with a bone anchored hearing aid if desired.
Because there are many treatment options, the appropriate option is determined on a case by case basis. The ideal solution for each patient is customized to meet the cosmetic and hearing goals of the patient. In the planning phase, patient have the option of wearing a bone conducting head band to temporarily treat the hearing loss associated with atresia.