What is microtia?
Microtia is also known as an underdeveloped ear. In its most severe form, it is called anotia, or absence of the ear. The condition occurs when several primitive embryologic structures fail to fuse at around 6 weeks of gestation. When this happens, various degrees of microtia are possible, from mild underdevelopment to complete absence of the external and middle ear components. Hearing loss can be present. Microtia and anotia are typically grouped into 4 grades:
- Grade I: the overall ear is small but all components are present, including the auditory canal.
- Grade II: the external ear is moderately misshapen, taking on an “S” or question mark-shaped appearance; the auditory canal may be narrowed or absent.
- Grade III: the external ear is severely misshapen, small, and usually contains no cartilage; the auditory canal may be narrowed or absent.
- Grade IV: anotia or complete absence of all portions of the external ear, usually with complete absence of the auditory canal as well.
It is important to distinguish microtia from other ear deformities, including cryptotia, constricted, lop ear, prominent ear, and Stahl’s ear deformities.
Why does microtia occur?
Microtia occurs in roughly 1 in 6,000-10,000 infants. Certain ethnicities seem to have a higher incidence such as in people of Japanese or Native American descent. It also appears to affect more boys than girls, and most often on the right side. There is NO consistent cause of microtia or anotia, although there is some thought that it may occur in association with decreased blood supply to the area in utero. Nonetheless, it is mostly a random event. Certain causative associations have been found to increase the risk of having microtia. In the past, rubella (or, German measles) in the first trimester of pregnancy was associated strongly with deafness and microtia. Several medications have also been implicated, including thalidomide, accutane, clomid, or retinoic acid. Although certain genetic syndromes may have associated microtia, the majority seem to have a multifactorial inheritance pattern, meaning that multiple environmental and genetic factors are acting at a critical time during development to produce the appearance.
What are some associated problems with microtia?
The majority of patients with microtia have no other associated problems other than the appearance of the ear. As mentioned previously, hearing loss can occur with microtia or anotia. In addition, various named syndromes can present with microtia as well, including oculo-auriculo-vertebral spectrum (OAV), Treacher-Collins, Nager, and CHARGE syndromes. Goldenhar syndrome, trisomy 21, trisomy 13, and other chromosomal abnormalities can produce microtia. Eye problems, cardiac defects, jaw deformities, renal problems, and limb or vertebral defects can occur. In the setting of hemifacial microsomia (most commonly associated with microtia), facial nerve palsy or varying degrees of facial paralysis can occur. Minor deformities such as preauricular pits or skin tags may also occur.
Can microtia be passed on?
Although there does appear to be a genetic component to microtia, the predictability of transferring the condition to offspring is poor. It is thought that an individual with microtia has approximately less than 5 percent chance of passing it on to a child. The risk increases with more individuals in the family having the condition.
How is microtia treated?
There are two major framework options for reconstructing the external ear: rib cartilage or Medpor. Whereas rib cartilage comes from the patient, Medpor is a hard, artificial porous implant. Both types of framework are implanted into the tissues where the natural ear would sit. However, reconstruction will usually proceed in multiple smaller stages in rib cartilage reconstruction, while Medpor reconstruction can be done often in a single stage. There are also other differences with respect to timing of reconstruction (4-5 years of age using the Medpor option; greater than 8 years of age for rib cartilage). Modern techniques in ear reconstruction have improved results dramatically in both cases. Each type of reconstruction carries its own set of pros and cons, which will need to be discussed.
Hearing loss can be treated with a bone-anchored hearing aid (BAHA). This can sometimes be performed at the time of ear reconstruction.
What is the recovery from microtia reconstruction?
Recovery from ear reconstruction is highly dependent on the method used. Harvesting rib cartilage in the initial surgery may require an overnight hospital stay, but the majority of subsequent stages and Medpor options are now available as outpatient surgery. Ear dressings are worn continuously during the first week and will be changed in the office or surgery suite. During the initial dressing change, stitches are removed and the ear is washed gently. New dressings are reapplied for an additional week. Thereafter, a removable cup dressing is worn for two weeks, then at nighttime only for an additional eight weeks. During the first eight weeks, rough play, contact sports, and heavy lifting are to be avoided. The child may bathe regularly with soap and water after the first two weeks. Additional restrictions are guided by the patient’s progress and type of surgery performed.
What are the risks and complications of microtia surgery?
Reconstruction for microtia is generally a safe process. Appropriate preoperative screening is performed to ensure that no existing health issues will interfere with surgery. The risk profiles are different slightly between rib cartilage options and those for Medpor. Standard surgical risks apply such as bleeding, infection, or complications from anesthesia but are rare in isolated microtia. The initial rib cartilage harvest can carry a small risk of a punctured lung (ie, pneumothorax), requiring a temporary chest tube in a very small number of cases. In addition, rib cartilage frameworks can potentially fracture or lose definition. Medpor ear reconstructions have a risk of early or late exposure of the implant or breakage of the implant. In both cases, surgery to remove and replace the implant is necessary.