Microtia is a congenital deformity where the pinna (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 asmicrotia-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.

Variabale degrees of penetrance of the gene responsible for hypoplasia account for the different sizes of microtic remnants seen. Even with extremely small microtic remnants, a lobular component is almost present, although vertically oriented and superiorly displaced.

Anotia, the severest of ear deformities, is extremely rare and probably represents complete failure of development of the auricular helix through a lack of mesenchymal proliferation. Other severe form of microtia probably represent arrests in embryonic development occurring at approximately 6-8 weeks of gestation. Less extreme forms of microtia are likely the result of embryonic accidents at a later stage, around the third month of fetal development.

Many attempts have been made to classify microtia based on embryologic development and severity of deformity.

Current system (Nagata, Tanzer) divides categories based on surgical correction of the deformity.

●Anotia: absence of auricular tissue

●Lobular type: remnant ear with lobule and helix but without concha, acoustic meatus, or tragus.

●Conchal type: remnant ear and lobule with concha, acoustic meatus, and tragus.

●Small conchal type: remnant ear and lobule with small indentation of concha.

●Atypical microtia: cases that do not fall into the previous categories.

Atresia of the cartilaginous or bony external canal is commonly associated with microtia. The atresia ranges from complete absence to several degrees of narrowing, blind pouches, or tracts. In Tanzer's series all patients had some deformity of the ear canal, middle ear, or both, and 50% had overt evidence of the first and second branchial arch syndrome (hemifacial microsomia).

Studies suggest that isolated microtia may represent the mildest phenotypic expression of hemifacial microsomia. In addition, there is increasing evidence that hemifacial microsomia, Goldenhar's syndrome, and oculoauriculovertebral dysplasia (OAV) are variants of the same condition, with a phenotypic spectrum of severity including various degrees of microtia.

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.

The goal of medical intervention is to provide the best form and function to the underdeveloped ear.

Typically, testing is first done to determine the quality of hearing. This can be done as early as in the first two weeks with a BAER test (Brain Auditory Evoked Response Test). At age 5-6, CT or “CAT Scans” of the middle ear can be done to elucidate its development and clarify which patients are appropriate candidates for surgery to improve hearing. For younger individuals, this is done under sedation.

The hearing loss associated with congenital aural atresia is a conductive hearing loss—hearing loss caused by inefficient conduction of sound to the inner ear. Essentially, children with aural atresia have hearing loss because the sound cannot travel into the (usually) healthy inner ear—there is no ear canal, no eardrum, and the small ear bones (malleus/hammer, incus/anvil, and stapes/stirrup) are underdeveloped. “Usually” is in parentheses because rarely, a child with atresia also has a malformation of the inner ear leading to a sensorineural hearing loss (as many as 19% in one study). Sensorineural hearing loss is caused by a problem in the inner ear, the cochlea. Sensorineural hearing loss is not correctable by surgery, but properly fitted and adjusted hearing amplification (hearing aids) generally provide excellent rehabilitation for this hearing loss. If the hearing loss is severe to profound in both ears, the child may be a candidate for a cochlear implant (beyond the scope of this discussion).

Unilateral sensorineural hearing loss was not generally considered a serious disability by the medical establishment before the nineties; it was thought that the afflicted person was able to adjust to it from birth. In general, there are exceptional advantages to gain from an intervention to enable hearing in the microtic ear, especially in bilateral microtia. Children with untreated unilateral sensorineural hearing loss are more likely to have to repeat a grade in school and/or need supplemental services than their peers.

Children with unilateral sensorineural hearing loss often require years of speech therapy in order to learn how to enunciate and understand spoken language. What is truly unclear, and the subject of an ongoing research study, is the effect of unilateral conductive hearing loss (in children with unilateral aural atresia) on scholastic performance. If atresia surgery or some form of amplification is not used, special steps should be taken to ensure that the child is accessing and understanding all of the verbal information presented in school settings. Recommendations for improving a child's hearing in the academic setting include preferential seating in class, an FM system (the teacher wears a microphone, and the sound is transmitted to a speaker at the child's desk or to an ear bud or hearing aid the child wears), a bone conducting hearing aid, or conventional hearing aids. Age for BAHA implantation depends on whether you are in Europe (18 months) or the US (age 5). Until then it is possible to fit a Baha on a softband.

It 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 body's 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. It must be stressed that many surgeons believe that ear canal reconstruction is unnecessary and overcomplicated and that very good hearing is possible with modern hearing aids which can be hidden under the skin.

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. If the reconstruction is ultimately successful, it is easy to remove the percutaneous BAHA abutment. If the surgery is unsuccessful, the abutment can be replaced and the implant re-activated to restore hearing.

Aural atresia is the underdevelopment of the middle ear and canal and usually occurs in conjunction with microtia. Atresia occurs because patients with microtia may not have an external opening to the ear canal, though. However, the cochlea and other inner ear structures are usually present. The grade of microtia usually correlates to the degree of development of the middle ear. Microtia is usually isolated, but may occur in conjunction with hemifacial microsomia, Goldenhar Syndrome or Treacher-Collins Syndrome. It is also occasionally associated with kidney abnormalities (rarely life-threatening), and jaw problems, and more rarely, heart defects and vertebral deformities.

For auricular reconstruction, there are several different options:

This surgery may be performed by specialists in the technique. It involves sculpting the patient's own rib cartilage into the form of an ear. Because the cartilage is the patient's own living tissue, the reconstructed ear continues to grow as the child does. This surgery varies from two to four stages depending on the surgeon's preferred method. The major advantage of this surgery is that the patient's own tissue is used for the reconstruction.

Middle ear and auricular reconstructive procedures are planned jointly by the otologist and the plastic surgeon, and the timing of the surgery takes into account the hearing status of the patient as well as cosmetic considerations with its psychological sequelae. As plastic surgeons, we will focus on factors that determine the appropriate time for reconstructing the external ear, namely (a) rate at with costal cartilage develops; (b) risk of the child's becoming a target of ridicule; and (c) corresponding size between the fabricated framework and the normal ear.

It is generally agreed that by about age 6 affected children become targets of ridicule by their peers. At that age the child is aware of being different and is motivated to conform, which will make him/her more cooperative with the surgery and the restrictions it entails. Before age 6 there may not be sufficient rib cartilage to build an ear framework of the proper vertical dimension and horizontal projection. The ear reaches approximately 85% of its full size by age 6, 90% by age 9, and 95% by age 14. Approximately 88%-94% of the adult ear width is reached in the first year of life, and girl's ears grow faster than boys'. With respect to ear length, the figure is 75% by the end of year 1 and 93% by age 10. The ear continues to grow longer over the next decade, although for practical purposes the ear is considered to be almost fully developed at age 6. According to the facts above, the generally recommended time for surgery is 6-7 age.

Reconstruct the ear using a polyethylene plastic implant (also called Medpor): This is a 1-2 stage surgery that can start at age 3 and can be done as an outpatient without hospitalization. Using the porous framework, which allows the patient's tissue to grow into the material and the patient's own tissue flap, a new ear is constructed in a single surgery. A small second surgery is performed in 3-6 months if needed for minor adjustments. This surgery should only be performed by experts in the techniques involved.

An auricular (ear) prosthesis is custom made by an anaplastologist to mirror the other ear. Prosthetic ears can appear very realistic. They require a few minutes of daily care. They are typically made of silicone, which is colored to match the surrounding skin and can be attached using either adhesive or with titanium screws inserted into the skull to which the prosthetic is attached with a magnetic or bar/clip type system. These screws are the same as the BAHA (bone anchored hearing aid) screws and can be placed simultaneously. The biggest advantage over any surgery is having a prosthetic ear that allows the affected ear to appear as normal as possible to the natural ear. The biggest disadvantage is the daily care involved and knowing that the prosthesis is not real.

The possible complications of microtia surgery are as follows:skin loss, infection, hematoma, chest wall donor site complications such as pneumothorax, atelectasis, hypertrophic scar.

abutment [ə'bʌtmənt] n.邻接

accutane ['ækjuːtein] n.（青春痘特效药）异维甲酸

anotia [æ'nəʊtə] n.无耳,无耳畸形

atresia [eit'riːziə] n.闭锁畸形

concha ['kɒŋkə] n.外耳，耳甲

cochlea ['kɒkliə] n.耳蜗

hypoplasia [,haipəʊ'pleizjə] n.发育不全

isotretinoin [aisətriti'nɔin] n.异维甲酸

lobular ['lɔbjulə] adj.有小叶的

microtia ['maikrətiːə] n.小耳症

mesenchymal [mes'eŋkiməl] adj.间叶细胞的

percutaneous [,pɜːkjuː'teiniəs] adj.经由皮肤的

pinna ['pinə] n.耳廓

polyethylene [,pɒli'eθəliːn] n.聚乙烯

prosthesis [prɒs'θiːsis] n.假体

scholastic [skə'læstik] adj.学术的

tragus ['treigəs] n.耳屏

acoustic meatus 听道

auricular helix 耳轮

ear bones:malleus/hammer, incus/anvil, stapes/stirrup 耳骨：锤骨，砧骨，镫骨

ear drum 耳鼓膜

hemifacial microsomia 半侧面部发育不良