Embryology and epidemiology of microtia.

The auricle derives from six hillocks arising from the first and second branchial arches. Different hillocks give rise to different parts of the pinna. In the course of embryonic development, the auricle migrates postero-cranially as the mandible enlarges. Auricular malformations, such as microtia, are thought to be related to cell death of the first and second arch derivatives. The prevalence and characteristics of microtia vary in different populations. The prevalence ranges from 0.83 to 17.4 per 10,000. Microtia is more common in males, and right-sided dominance varies from 57 to 67%. The prevalence of aural atresia or stenosis varies from 55 to 93%. Microtia has been associated with numerous risk factors including race and gender. Genetic factors are likely to have an effect at least in some patients with microtia.