Birth Defects Other Anotia Microtia

Anotia and microtia are congenital defects affecting the ears. If a person has one of these conditions, the outer structure of the ear, called the pinna or auricle, does not form properly, or at all. These birth defects can affect hearing as well as the outward appearance of the ear. In many cases, certain treatments can improve ear function.

The Human Ear and Hearing

Each of the human ear’s three sections has its own functions:

  • The outer ear takes in sound.
  • The middle ear contains the eardrum and several small bones that are moved by sound waves that have entered the ear. These vibrations are transmitted to the inner ear.
  • The inner ear has a structure called the cochlea, which contains small hair cells that respond to sound information and send nerve impulses along the auditory nerve to the brain, where they can be interpreted.

The outer ear acts as a funnel to concentrate the sound waves in the ear canal as they move toward the eardrum. This information from the eardrum is then transmitted along the rest of the hearing chain.

Defects of the Outer Ear

Anotia is the complete absence of the external ear and auditory canal. Microtia is the abnormal formation of the external ear. These congenital defects are usually unilateral; that is, they affect a single ear. Both anotia and microtia are usually associated with atresia of the ear canal, meaning the ear canal is underdeveloped or absent.

Anotia and microtia are associated with severe hearing loss in the affected ear. The inner ear functions properly, but sound cannot be transmitted to the inner ear because of structural abnormalities in the outer ear that block sound from entering the hearing system.

Causes of Anotia and Microtia

Development of the outer ear occurs during the first trimester of pregnancy. When the ear tissue fails to develop properly, anotia or microtia results. Anotia and microtia are usually isolated conditions, but in some cases may be associated with other birth defects or syndromes. For example, the ears and kidneys develop at the same time, so children with ear defects are often checked for kidney defects at birth.

Treatment for Congenital Defects of the Outer Ear

Surgery can be performed to open the ear canal and facilitate hearing. In addition, an external ear can be created through surgery, using either cartilage from the individual’s ribs, or artificial materials. A prosthetic ear may also be made. Both surgical procedures and prostheses improve the cosmetic appearance of the ear, and allow for better hearing.

Some families may choose a bone-anchored hearing aid (BAHA) over surgery. This allows sound vibrations to travel through bones in the head to the inner ear. Surgery is becoming increasingly safe and more refined, but families and doctors can work together to determine the best course of treatment for an individual child.

Resources

IN.gov (n.d.). Anotia and microtia.Retrieved April 24, 2010, from: http://www.in.gov/isdh/files/anotia.pdf.

KidsHealth.org (n.d.). Your ears.Retrieved April 28, 2010, from: http://kidshealth.org/kid/htbw/ears.html.

Microtia-Atresia. (n.d.). Important FAQs about microtia