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What are Microtia and Atresia?
Microtia means “small ear” and is a relatively rare deformity that occurs in about one in every 10,000 births. Microtia can occur with other congenital syndromes, but most often it is an isolated abnormality where cartilage and tissues did not fully develop. It typically affects the right ear and occurs more in Hispanic and Asian populations.
Microtia is classified in four degrees of severity:
- Grade I: A slightly small ear, shaped much like a normal ear, and often accompanied by a small, narrow ear canal.
- Grade II: A partial ear usually with an absent ear canal.
- Grade III: Absence of most of the external ear with a small peanut-shaped remnant ear lobule, an absent ear canal and absent ear drum. This is the most common presentation of microtia.
- Grade IV: Total absence of the ear, or what’s called anotia.
Some patients with microtia may also have atresia, or the absence or underdevelopment of the ear canal. About 90% of these patients experience conductive hearing loss, where sounds may still reach the inner ear, but they are extremely muffled. A few children also experience sensorineural hearing loss, which happens when the inner ear structures are too narrow. In both cases, hearing can be restored.
Causes of Microtia and Atresia
The exact cause of microtia is unknown but it is most likely a genetic condition. Some kids have microtia and atresia as part of a genetic disorder, such as Treacher Collins or Nager syndrome. Parents who have a child with microtia have an increased risk of 1 in 20 for having future children with microtia. The risk of a child with microtia eventually having a child of their own with microtia is also 1 in 20.