Microtia & Aural Atresia
What is Microtia?
Microtia refers to a small, abnormally shaped ear, which can range from a minimally deformed small ear to a complete absence of the ear. This occurs in about one in 7,000 births and is more common in males and on the right side. Most cases (90%) are on just one side (unilateral), but this can affect both ears as well (bilateral). It is very often associated with absence of the ear canal (aural atresia) or a narrow ear canal (ear canal stenosis).
What Are the Types of Microtia?
There are four main types of microtia. Grade 1 is an ear that is smaller than normal, but still looks mostly like an ear. In Grade 2, portions of the ear are missing, often the upper third, and is referred to as “concha type microtia.” The ear canal is usually very narrow or missing.
Typical microtia, referred to as Grade 3, is a peanut-shaped remnant of skin and cartilage where the ear should be and is also referred to as “lobule type microtia.” This is almost always associated with an absent ear canal (known as aural atresia). Grade 4 microtia is complete absence of the external ear, also referred to as anotia.
What Causes Microtia? Is it Genetic?
In the majority of cases (95%), the condition not genetically inherited, and there is no family history of microtia or other ear abnormalities. It is usually a random event where the portions of the body designated to become the ear are abnormally “shut off,” and the ear and ear canal do not form. This is not the fault of the mother, and there is nothing that could have been done differently during pregnancy. It is not often found on the prenatal ultrasound. The exact molecular and genetic causes of microtia are still under investigation.
What Medical Issues Are Associated with Microtia?
Microtia is usually an isolated condition, and the child has no other medical issues. However, it can be associated with other facial malformations such as a small jaw or craniofacial syndromes. These include Treacher-Collins Syndrome, and forms of Oculoauricularvertebral dysplasia (OAVS, Goldenhar syndrome, hemifacial microsomia).
How Are Microtia and Aural Atresia Diagnosed?
Microtia and aural atresia are usually first noticed when the child is born. The ear will be abnormally small or malformed, and the ear canal absent. Due to the missing ear canal, the child will fail the initial newborn hearing screening, and will be referred for further audiologic testing. Once the microtia is recognized, some children undergo a kidney ultrasound or a referral to a craniofacial team if there are other facial abnormalities.
What is the Workup for a Child with Microtia?
We believe that children with microtia and/or aural atresia should be followed from an early age, and a plan developed for hearing rehabilitation, further testing, and cosmetic reconstruction. The exact workup and plan depend on the age of the child. We do not generally recommend a CT scan at an early age, as it is usually not helpful and exposes the newborn of infant to radiation. Typically, we will obtain an audiogram early, and possibly fit the child with a bone conduction hearing device. As they get older, there are more hearing options, including implantable devices. Ear reconstruction surgery is typically offered around age 10.
What is Aural Atresia?
Aural atresia is the absence of the ear canal. The outer ear and ear canal develop at the same time, which means that microtia and atresia are commonly found together. This causes a hearing loss (what is called a “maximal conductive loss”) because the sound waves cannot get through to the eardrum/inner ear. Usually, the nerve for hearing and inner ear is normal, and this can be determined with a hearing test (audiogram).
How Does Aural Atresia or Stenosis Affect Hearing?
Children with aural atresia or a severely narrow ear canal (stenosis) will have hearing loss in that ear because sound waves cannot get to the inner ear. This can cause issues with hearing in noisy situations, and localizing where sound is coming from, particularly if the aural atresia is on both sides. Studies have shown that children with hearing loss even just on one side can have increased difficulties in school. This can also affect interactions with friends and family. Some children with hearing loss on one side do very well without intervention, but we strive to achieve the highest potential for each child and monitor their hearing status very closely.
Aural Atresia and Hearing Loss Management
Children with unilateral or bilateral aural atresia and/or microtia will obtain an audiological evaluation to diagnose the degree and type of hearing loss. The type of audiological evaluation will vary depending on the age of the child. Information obtained on the audiological evaluation will be used to determine candidacy for a bone conduction hearing device(s). Bone conduction hearing devices pick up sound and convert it into vibration. The vibration of sound is transferred to the cochlea.
Infants and young children with aural atresia and an associated conductive hearing loss are typically fitted with non-surgical transcutaneous bone conduction hearing device(s). These devices are worn on a softband or coupled to a medical grade adhesive.
Older children may explore surgical candidacy for bone conduction hearing devices. Lurie Children’s was one of the first centers in the U.S. to implant the Baha® Attract system. This is a passive transcutaneous system that uses a sound processor coupled to a magnetic baseplate. The device converts sound into vibrations that are transferred through an external magnet. The magnet is attracted to a surgically implanted magnet and titanium implant. The implant transfers sound through vibrations to the inner ear and cochlea.
Other surgical options include active transcutaneous systems. Active transcutaneous systems use a sound processor connected to surgically implanted magnet and transducer. Sound vibrations are sent directly to the implant which transfers the sound to the inner ear and cochlea. Lurie Children’s is currently implanting the Cochlear Osia® and MEDEL BONEBRIDGE® systems.
These surgically implanted devices are safe and implanted with one surgery. Activation of the device will be completed by your audiologist approximately one month after surgery. Bone conduction hearing devices are expected to improve a child’s ability to hear and develop spoken language, while also improving understanding in difficult listening situations such as a classroom or noisy environment.
What are the Options for Microtia and Ear Reconstruction?
There are several treatment options for microtia: reconstruction of the ear, a prosthetic ear, or leaving it alone. Lurie Children’s Microtia and Aural Atresia Program staff counsel parents on all of the options during the initial visit.
Dr. Akira Yamada is an expert in ear reconstruction, creating a three-dimensional framework of the ear to ensure an exceptional appearance following surgery. If surgical intervention is needed, he will discuss the best surgical option for each patient with their families.
One way it is treated surgically is to perform ear reconstructions using cartilage, which is sculpted into a new ear and placed under the skin on the microtia side. The cartilage is from the child’s own ribs. This method is preferred rather than using synthetic implants because the cartilage is part of the child’s own body, and after surgery and the ear heals, there are no restrictions on activity. Reconstruction with rib cartilage has been a proven technique for 60 years. Most children do not undergo surgery to treat microtia until the ear has stopped growing usually around 10 years of age. Age 10 is best time to do cartilage surgery because enough amount rib cartilage is available to make a full ear shape framework, and rib cartilage does not become rigid until age 15. Even after 15 years of age, rib cartilage surgery is still possible for some patients.
At Lurie Children’s, a two-stage surgery method is used. The first stage to create the ear shape and the second stage is for ear elevation. If there is redundant skin left over after stage two surgery, the abundant skin can be trimmed surgically. Although our preferred method is to use your child’s own rib cartilage for the ear framework because of its proven sustainability, synthetic framework (known as Medpor) is an option if a family does not wish to use rib cartilage for the ear framework, or wishes to have the ear shaped earlier than age 10. The timing of this surgery is a little bit earlier -- around 6-9 years of age -- when fascia (connective tissue around an organ) is thinner to cover the framework. This method is one-stage surgery that spares rib cartilage harvest. However, this method needs more skin harvest and may leave more skin scars.
Rib Cartilage Framework v. Synthetic Framework
Cartilage framework placed under the original skin has best sensation of the new ear. Medpor framework is covered with less sensate skin. Both secondary ear construct with cartilage framework, and Medpor construct take time to obtain ear definition: it may take 6- 12 months to obtain the shape.
Both cartilage and Medpor surgery may be associated with some complications. Infection is not common but can happen immediately after surgery or months later. Infection of cartilage framework is typically localized, unlikely to need replacement of the framework, but may require clean-up procedure. Infection of Medpor may be either a localized infection or may need to replace with new framework.