Microtia is a birth deformity that results in a “small ear.” On average it occurs in 1 in 5,000-7,000 births, with up to 1 in 1000 in the native populations of North and South America, 1 in 2100 in Japanese and Korean communities and 1 in 20,000 in Caucasian populations.
In 90% of cases only one ear is affected, known as unilateral microtia, however bilateral microtia can occur as well and requires more immediate attention. Typically, 65% of cases are seen in boys, only 35% in girls. Nearly twice as many microtia cases occur with the right ear compared to the left.
Four grades of microtia:
Grade 1: A minimally deformed ear with identifiable structure and an external ear canal present.
Grade 2: A partial ear that appears miniature, with a closed off, or stenotic, external ear canal that causes conductive hearing loss.
Grade 3: The most common form, with an ear looking like a sausage shaped wrinkle of skin and lacking an external ear canal and ear drum.
Grade 4: A total absence of the ear, also known as anotia.
In the 95% of cases, atresia presents with cases of microtia. This condition results in the absence or underdevelopment of the ear canal and middle ear structures. The outer and middle ears develop at the same time from the same progenitor tissue in the womb, therefore any defect in one will most likely be accompanied by defects in the other. However, it is important to note that in the vast majority of cases the inner ear, the part that translates air vibrations into sound signals for the brain, is still fully functional. With proper hearing aid devices and corrective surgery full hearing can be restored.