Microtia

microtia.jpg
Microtia.

Microtia is an ear deformity that occurs one in every 6,000-12,000 births. There are several degrees of microtia, ranging from a portion of the external ear missing to complete absence of an external ear. When there is a microtia present, there is usually no ear canal present. This is called atresia.

A child with a microtia and atresia will usually have normal sensorineural hearing and moderate to severe conductive hearing loss.

All this means is that the child’s inner ear is normal (normal sensorineural status), but because there is no ear canal, there is no way for sound to “conduct” to the inner ear via the ear canal. When hearing loss occurs because of an outer or middle ear problem, this is called conductive hearing loss. When hearing loss occurs because of an inner ear problem, this is called sensorineural hearing loss.

It is felt that microtia may be caused by ischemia or decreased blood flow during development.

Luckily, the inner ear (the location of the hearing and balance organs) forms at a different time as the outer and middle ears. As a result, the inner ear will function at a normal level, even in a child with a microtia. The kidneys develop about the same time as the ears, so an evaluation is commonly done prior to leaving the hospital after birth. Microtia is more common in Japanese and Navaho American Indians, and also more common in males.

If only one ear is affected, it is more typically the right ear that is affected. About 10% of the time, both ears are involved. The chances of this condition recurring in a future pregnancy is less than 6%.

The first priority will be to test the child's hearing. In all cases, it is urgent to give the child maximum sound input to maximize brain development and speech development.

A BAER (brain auditory evoked response) test will be recommended, with behavioral hearing test when the baby is a bit older. A CT (computerized tomography) scan will also be done to determine the anatomy of the bony structures and middle and inner ears.

Parents with microtia tend to have guilt over their child's condition. It is not the parent's fault!

It is important to see a Genetics specialist in order to evaluate family history. Some children with microtia will have other conditions such as Goldenhar syndrome, Treacher-Collins syndrome, and hemifacial microsomia (under-development of the structures on one side of the face). Children can have middle ear abnormalities as well. Dental and jaw abnormalities can also be associated with microtia.

There are various options to help the hearing status on children with microtia and atresia.

A bone-anchored hearing aid (BAHA) is an option to ear canal surgery to improve the hearing.

Treatment plans will be unique to each child because of the variation in this condition.

An interdisciplinary team will need to work together to give the child the best-coordinated care. This team will consist of an otolaryngologist (ear, nose and throat specialist), a plastic surgeon, an audiologist (hearing specialist), genetic specialist, a dentist, a speech therapist, and a pediatrician or pediatric nurse practitioner. In some cases, a social worker or psychologist can help support the family in coping with this condition and making decisions.

Even if one ear is unaffected and hearing well, a bone conduction hearing aid is recommended to provide auditory stimulation and promote auditory brain development on the affected side. Until the child is old enough for surgery, a bone conduction hearing aid can be worn on a headband-like strap.

Video Clip: 6-month-old boy with right-sided microtia and atresia hearing clear sound in his right ear for the first time. The change in his demeanor shows the second that he begins to hear clear sound in his right ear. https://www.youtube.com/watch?v=-hhnlOiYxMc

Typically the child will be about 4-10 years of age if ear reconstruction surgery is done. The external ear will typically be reconstructed, sometimes using a piece of rib bone to form the structure of the ear. This external ear is allowed to heal for several months before the second-stage surgery to create the ear canals.

If children also have defects of the middle ear (such as Treacher-Collins Syndrome) the reconstructive surgery of the ear canal may not improve hearing. An option may be a bone-anchored hearing aid that is ideal for a child who has middle-ear problems but an intact inner ear and nerve structure to the brain.

Sources

CDC Congenital Birth Defects Info http://www.cdc.gov/ncbddd/birthdefects/index.html 

CDC Hearing Loss in Infants and Children http://www.cdc.gov/ncbddd/hearingloss/index.html 

Diseases and Conditions Identified in Children and Youth with Special Health Needs (CYSHN). Minnesota Department of Health. http://www.health.state.mn.us/divs/cfh/topic/diseasesconds/anotia.cfm 

Bonilla, Arturo. Microtia Congenital Deformity Institute. http://www.microtia.net/hearing.htm

Continue Reading