Anotia / Microtia

Condition Description

Anotia means absence of the external ear. Microtia is the term for an incompletely formed external ear. Aural atresia is the absence of the ear canal.

Early in fetal life (about the 5th week) the complex process of development causes cells to move to the correct position for ear formation. If this process is interrupted for any reason, then the ear will not form correctly.

There are 4 types of microtia. ranging from Type 1 to Type 4. Type 1 microtia is the mildest, usually with a smaller-than-normal ear that has most of the components of a non-affected ear. Type 4 (anotia) is the most severe, with the external ear structures missing. Within the range of types, the ear canal may or may not be present and functional, and some to most of the features of the external ear are underdeveloped. If the ear canal is closed, conductive hearing loss is also present. Type 3 is the most common form of microtia.

In most instances the children with microtia will have normal inner ears and sensory structures, causing conductive (rather than sensory) hearing loss. Hearing testing with bone conduction is necessary to see if sensory hearing loss is also present.

This is a relatively common group of disorders, occurring in 1 of every 6,000-12,000 live births. Our program has been tracking anotia/microtia among live births in select counties since 2005 and are gradually expanding statewide.

• Using data from births to Hennepin and Ramsey county residents 2010-2014, we found that 3 babies were born with anotia/microtia per 10,000 births.
• Using this data, we estimate about 21 babies are born with anotia/microtia every year in Minnesota.

Treatment may depend on the severity of the condition. Early intervention for hearing loss is important for maximizing communication outcomes.

Parental education and support are essential, and local, regional and national organizations may be very helpful.

Condition specific organizations

• Minnesota Department of Health - Hearing Loss
• CDC Hearing Loss in Infants and Children
• CDC Facts about Anotia/Microtia