Embryology (development) of the ear
The formation of the ear occurs during the first trimester of pregnancy. It arises from six lumps of tissue called “hillocks” on each side of the embryo’s head. These then develop into the various parts of the external ear.
A child’s ear reaches 95% of adult size by the age of six.
What is microtia?
Microtia is an incomplete or abnormally formed ear. It literally comes from the words “micro” (small) and “otia” (ear). Microtia may affect one side only (unilateral) or affect both ears (bilateral). Eighty percent of the time it is unilateral. Some people may have microtia as part of a syndrome known as craniofacial (or hemifacial) microsomia. In this condition, there may also be a small jaw and weakness of some of the facial muscles on the affected side. Treacher Collins syndrome, in which the eyes and facial bones are affected, is also another rare condition that may be associated with microtia.
How common is microtia?
Microtia occurs in around 1 in 6000 births. The chance of an affected parent transmitting this to their children is usually small (less than 6%), but there are some families who carry a gene for microtia.
Other ear conditions
Cryptotia literally means “hidden ear”. In this condition the upper part of the ear is buried beneath the skin of the scalp. Usually the cartilage is normal. Reconstruction involves lifting the ear out from under the skin, creating a groove behind the upper ear and using flaps of the surround•ing skin to cover the ear cartilage. This is usually done as a day procedure in a single stage.
A lop ear is one in which the upper part of the ear is bent over. There is often a relative shortage of skin and the cartilage framework may also be smaller than the other side. Surgery involves correction of the cartilage using either the cartilage already in the ear, or sometimes a cartilage graft from the other ear. Skin cover involves using local skin flaps. When severe, this condition occasionally requires correction with the use of a rib graft, similar to the procedure for microtia.
(Adapted from Microtia and Ear Anomalies in Children, Royal Children’s Hospital Melbourne)