What is microtia?
Microtia is a congenital defect of the child's ear. A baby's ears begin
to form in the womb during the second trimester. They usually end at 28 weeks.
Sometimes one or both ears do not form completely. When the outer part of the
ear is small or missing, it is called microtia. The word itself means
"little ear". When the outer ear is completely absent, this condition
is called anotia.
Microtia is rare. It affects only 1 to 5 out of 10,000 children.
Usually affects only one ear - most often the right. This is called unilateral
microtia. When it affects both ears, it is bilateral.
Children with this condition often have hearing loss in the affected
ear. This can prevent them from learning to speak. Surgery can help with this
and the appearance of the ear.
Degrees of microtia
Microtia has four degrees:
- Grade 1: The ear looks normal, but it’s smaller than usual.
- Grade 2: The outer ear is only partly formed and 50% to 66% smaller than the outer ear on the other side. The ear canal, which runs from the outer ear to the middle ear, is narrow or closed off.
- Grade 3: The outside part of the ear is a tiny piece of cartilage shaped like a peanut. There’s no ear canal or eardrum to send sound to the middle ear.
- Grade 4: Anotia: The outer ear is missing.
Causes of microtia and risk factors
In most cases, doctors cannot find the cause. Usually affects boys.
Sometimes the disease is inherited and results from a gene change, but this
only happens in about 5% of cases and may skip generations.
Microtia can also be part of the syndrome, for example:
- Hemifacial microsomia -- the lower half of the face doesn't grow correctly on one side
- Goldenhar syndrome -- the ear, nose, lip, and jaw don't form completely
- Treacher Collins syndrome -- a condition that affects development of the cheek, jaw, and chin bones
Some things might increase the risk, for instance if the mother:
- Has diabetes
- Eats a diet low in folic acid and carbohydrates during pregnancy
- Takes the acne drug isotretinoin in pregnancy
- Has rubella during the first trimester of pregnancy
- Drinks alcohol during pregnancy.
Microtia and hearing loss
If a child has hearing loss due to microtia, it is usually a type called
conductive hearing loss. Sound cannot travel from the outer ear to the inner
ear.
Sensorineural hearing loss occurs in fewer children with the disease.
This can happen when the tiny hairs that carry sound from the inner ear to the
brain are damaged. This type of hearing loss is usually irreversible.
Diagnosis of microtia
The doctor will want to check if your child hears well. One of the most
common tests is the brainstem auditory response test. The doctor will place
small stickers on the child's head and around the ears. The computer then
measures how their auditory nerve responds to sound.
The test is not painful, but your child should remain still. If they are
under 6 months old, your doctor may do the test while they are sleeping. If
they are between 6 months and 7 years old, they may need medication to help
them sleep.
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