Microtia: Birth Defects of the Ear

Everything you need to know about this birth defect

Normal Ear Versus Microtia
Normal Ear Versus Ear Affected By Microtia. Photo © Millicent Odunze, M.D., M.P.H.

Microtia (my-kro-shuh) is a birth defect of a baby's ear. It happens when the external ear is small and not formed into a normal ear in the fetus during the first few weeks of pregnancy. The earlier the problem occurs while the baby is in the womb, the more severe the deformity. Plastic surgeons can surgically correct these ear deformities.

One to five babies per 10,000 births have microtia. It affects males more than females, and is more common in Asians and Hispanics, than Caucasians and African-Americans.

The highest occurrence is among the Navajo tribe Native Americans. The right ear is affected more often than the left ear or both ears.

What Microtia Looks Like

Microtia can take on different forms. Sometimes a bump of skin may be present where the ear should be. Sometimes parts of the lower ear are present, but the upper ear is absent. The most severe form is when the outer ear is completely missing, also known as anotia (an-o-shuh). There may be a lack of an opening into the ear canal.

What Causes Microtia

No one knows the exact reason microtia occurs. In some cases, genetics are the reason, either because of changes in their genes, or because of abnormality in a single gene that cause a genetic syndrome. Certain drugs, such as Accutane (isotretinoin), taken during pregnancy, decreased blood flow to the fetus, and environmental factors are all possible causes of microtia.

Some factors that increase the risk of having a baby with microtia are diabetes and maternal diet, according to the Centers for Disease Control and Prevention.

Specifically, if a woman has diabetes prior to getting, she has a higher risk of having of baby with microtia, compared to women who don't have diabetes. In addition, pregnant women eat a diet low in carbohydrates and low in folic acid may also increase their risk of birthing a baby with microtia.

Other Defects Associated With Microtia

Even though it is the outer ear that has the noticeable deformity in microtia, other parts of the ear system are affected.

The inside of the ear, specifically the ear canal and the middle ear, often have defects as well. Sometimes the ear canal does not develop. In these individuals there is no visible hole that leads to the ear drum and the middle ear. These abnormalities can cause hearing loss.

People with bilateral microtia — microtia in both ears — are in a totally different situation than people with a unilateral microtia. Those with unilateral microtia have normal hearing in the normal ear, whereas those with bilateral microtia may be functionally deaf.

Repairing the Microtia Ear

The main goal of restoring the outer ear is to improve hearing, since it catches sounds and directs them into the ear canal towards the eardrum and the hearing apparatus. Improved hearing helps with speech. A hearing aid may still be needed. What's more: an improvement in appearance is an additional benefit that can boost self-esteem and social acceptance. Reconstruction of the ear canal is performed by an otologist (oh-tall-uh-jist).

When to Repair the Ear

The ear reaches the majority of its growth — 85 percent — by the age of four. The ear continues to increase in width until age ten. The two factors that influence when ear reconstruction occur are:

  • Availability of enough rib cartilage to make the structure of the ear: It is not until age five or six that a child’s rib cage is large enough to provide adequate donor cartilage for an ear framework.
  • Psychological effect of having abnormal/no ear(s): Reconstruction is done around school age in order to minimize/avoid teasing from peers.

The best results occur when the reconstruction is delayed until after the age of ten.

Treatment of Microtia

The outer ear can be reconstructed with synthetic (man-made) materials or from rib cartilage. There are advantages and disadvantages to both options:

Synthetic Materials

Some of the advantages to using synthetic material to rebuild a microtia ear are that there are no issues, such as scars and pain, from harvesting rib cartilage; can be done in one procedure; and the result is excellent cosmetic appearance.

The disadvantages of using these materials are that the ear is susceptible to minor trauma and infection; as well as the possibility of the body rejecting the new ear because of the materials used. 

Cartilage Graft

Harvested from the rib cartilage, the disadvantages of using this treatment option is there can be pain and a scar associated with getting the material. Also, there is more than one surgery. However, it is the best long-term option and because it uses a person's own materials, there isn't the possibility of the body rejecting the ear.

A Prosthetic Ear

In cases where there is not enough skin to cover either a synthetic framework or a cartilage framework due to trauma, burns, radiation, etc., a prosthetic ear can be used. A prosthetic ear has its advantages and shortcomings as well. While a prosthetic ear can look very much like a real ear, the quality of the device depends on the skills of the maker and available technology. Additionally, a prosthetic ear can be quite expensive. How long the device lasts depends on the care rendered by the owner.

In half of microtia cases, there is enough of the middle ear that can be reconstructed to improve or restore hearing.

Potential Complications of Treatment

As with any surgical procedure, there are potential complications when it comes to ear reconstruction. Infection is a potential complication with either the synthetic or cartilage framework. Hematoma, otherwise known as a blood collection, can also compromise the cartilage framework. Skin loss in the ear area is also a possibility. Additionally, in cases where rib cartilage is used, lung problems, chest wall contour deformities, and unsightly scarring can occur. Complications involving the framework can result in needing to perform the procedure again.

Sources:

Division of Birth Defects and Developmental Disabilities, NCBDDD,  Birth Defects: Facts About Anotia/Mirotia. Centers for Disease Control and Prevention. November 9, 2015.

LeBlanc DM. Microtia. In: Janis JE, ed. Essentials of Plastic Surgery. St. Louis: Quality Medical Publishing, Inc., 2007.

Thorne CH. The External Ear. In: McCarthy JG, RD Galiano, Boutros SG, eds. Current Therapy in Plastic Surgery, 1st Ed. Philadelphia: Elsevier, Inc, 2006.

Thorne CH. Otoplasty and Ear Reconstruction. In: Thorne CH, Beasely RW, Aston SJ, Bartlett SP, Gurtner GC, Spear S, eds. Grabb and Smith’s Plastic Surgery, 6th ed. Philadelphia: Lippincott, 2007.

Continue Reading