Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped pinna is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Microtia can be unilateral (one side only) or bilateral (affecting both sides). Microtia occurs in 1 out of about 8,000–10,000 births. In unilateral microtia, the right ear is most commonly affected. It may occur as a complication of taking Accutane (isotretinoin) during pregnancy. Classification
According to the Altman-classification, there are four grades of microtia:
Grade I: A less than complete development of the external ear with identifiable structures and a small but present external ear canal
Grade II: A partially developed ear (usually the top portion is underdeveloped) with a closed stenotic external ear canal producing a conductive hearing loss. Grade III: Absence of the external ear with a small peanut-like vestige structure and an absence of the external ear canal and ear drum. Grade III microtia is the most common form of microtia. Grade IV: Absence of the total ear or anotia. Causes and risk factors
The etiology of microtia in children remains uncertain but there are some cases that associate the cause of microtia with genetic defects in multiple or single genes, altitude, and gestational diabetes. Risk factors gathered from studies include infants born underweight, male sex, women gravidity and parity, and medication use while pregnant. Genetic inheritance has not been fully studied but in the few studies available, it has shown to occur during the early stages of pregnancy.
Age for BAHA implantation depends on whether the child is in Europe (18 months) or the US (age 5). Until then it is possible to fit a BAHA on a softbandIt is important to note that not all children with aural atresia are candidates for atresia repair. Candidacy for atresia surgery is based on the hearing test (audiogram) and CT scan imaging. If a canal is built where one does not exist, minor complications can arise from the bodys natural tendency to heal an open wound closed. Repairing aural atresia is a very detailed and complicated surgical procedure which requires an expert in atresia repair. While complications from this surgery can arise, the risk of complications is greatly reduced when using a highly experienced otologist. Atresia patients who opt for surgery will temporarily have the canal packed with gelatin sponge and silicone sheeting to prevent closure. The timing of ear canal reconstruction (canalplasty) depends on the type of external ear (Microtia) repair desired by the patient and family. Two surgical teams in the USA are currently able to reconstruct the canal at the same time as the external ear in a single surgical stage (one stage ear reconstruction). In cases where a later surgical reconstruction of the external ear of the child might be possible, positioning of the BAHA implant is critical. It may be necessary to position the implant further back than usual to enable successful reconstructive surgery – but not so far as to compromise hearing performance.