Development and Treatment of Outer Ear Malformations

Microtia is a congenital malformation of the ear that can exist as an isolated anomaly or as a comorbidity to a congenital syndrome. The severity of microtia is classified using grading systems, with the most common one being the Marx classification system. Severe grades of microtia (grades III and IV) will include aural atresia, which is the absence of the external ear canal. There is a lack of consensus on the point of origin of microtia, but research suggests that family history, genetic syndromes, teratogens, and maternal factors can pose as risks during fetal development. Aural atresia can be congenital or acquired from otologic surgery, blunt or penetrating trauma, or inflammation. Infants with severe cases of microtia with atresia are immediately identified during their newborn physical examinations. Grades III and IV of microtia with atresia will typically present with a conductive hearing loss, and it procures the need for early intervention hearing services. Audiologic testing is recommended within the first month to determine the degree of hearing loss and assess cochlear function prior to rehabilitation. Following audiologic assessment, there are two primary treatment options. Many children will start with soft-band bone-conducted amplification and may switch to osseointegrated devices once their skull is developed to support it. Others may undergo surgical reconstruction and receive a new auricular framework and ear canal. Researchers have reported significantly favorable outcomes with each treatment method. This manuscript also addresses current knowledge surrounding various aspects of outer ear anomalies and the gaps in existing literature. The evidence supporting the development of the auricle in utero is a topic in ongoing debates, which leads to further questioning of the current theories of when microtia is evident. Studies investigating teratogenic exposure have also identified inaccuracies in self-reports from mothers when assessing potential agents that were introduced during pregnancy. Additionally, there is limited information available for current and future audiologists on the protocols for assessing children with microtia and atresia. This comprehensive overview aims to bring awareness to the missing pieces and the need to create new resources to ensure that healthcare professionals are following best practices for this population.