Microtia is a common birth defect where the outer and middle ear does not develop fully. The literal meaning comes from the Latin words micro and otia, or “little ear”. At birth, a normal ear includes a fully formed external ear and a middle ear that transmits sound waves to the inner ear and brain.
Microtia patients do not have a normal external ear, but have a small protrusion or nub where the ear should be. The level of severity is graded according to the amount of deformity to the outer and middle ear.
It occurs approximately in 1 in every 7,500 births in the U.S. but the numbers vary greatly depending upon ethnicity. Hispanics and Asians have a higher rate of occurrence than African-Americans and Caucasians.
The four grades of Microtia are:
- Grade 1: Minimal deformity, only a slightly smaller ear than normal and ear canal is present
- Grade 2: A partial, miniature ear with a closed off ear canal that results in hearing loss.
- Grade 3: Only a small, peanut-like trace of an external ear and an absence of an ear canal and ear drum. This is the most common type of microtia and can be corrected by surgery.
- Grade 4: Complete absence of the ear also known as anotia, which is Latin for “no ear”.
In only 10% of microtia cases both ears are affected and patients are twice as likely to have the right side affected over the left side. As for gender differences, the majority of patients are boys at 65%.
Microtia is part of a range of facial asymmetry deformities known as Hemifacial Microsomia or HFM. Patient with HFM almost always have microtia but may have other craniofacial deformities involving the skull, ear, jaws, soft tissues and nerves of the face. Depending on the severity of the deformity, hearing may be minimally or majorly affected.