Microtia

Microtia
Unilateral Grade III microtia (left side).
ICD-10	Q17.2
ICD-9	744.23
OMIM	600674
DiseasesDB	29876
eMedicine	ped/3003

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Overview

Microtia (meaning 'Small ear') is a congenital deformity of the pinna] (outer ear). It can be unilateral (one side only) or bilateral (affecting both sides). It occurs in 1 out of about 8,000-10,000 births. In unilateral microtia, the right ear is most typically affected.

Grading

There are four grades of microtia ^[3]:

• Grade I: A slightly small ear with identifiable structures and a small but present external ear canal
• Grade II: A partial or hemi-ear with a closed off or stenotic external ear canal producing a conductive hearing loss
• Grade III: Absence of the external ear with a small peanut vestige structure and an absence of the external ear canal and ear drum
• Grade IV: Absence of the total ear or anotia.

Grade III is most common, and can be corrected by surgery. Typically, testing is first done to determine if the inner ear is intact and hearing is normal. If hearing is normal, the next step (if a canal is not visible externally) will be to determine if a canal exists, by CT scan. For younger patients, this is done under sedation. Age when outer ear surgery can be attempted depends on the technique chosen (see below). The earliest age surgery can be attempted is age 3 for Medpor and 5 1/2 for Rib Graft. Less experienced surgeons may recommend waiting until a later age, such as 8-10 when the ear is full adult size.

Options

There are two separate issues in microtia surgery:

1. Auricular reconstruction to restore the visual appearance and form of the outer ear
2. Repair of atresia or application of a bone-anchored hearing aid BAHA to restore hearing.

Unilateral deafness is not generally considered a serious disability, especially when the person is able to adjust to it from birth. In some areas the benefits of intervention to enable hearing in the microtic ear are not considered to outweigh the risks, except in bilateral microtia. However, children with untreated unilateral hearing loss are eight to ten times more likely to have to repeat a grade in school. If surgery or aids are 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. Age for BAHA implantation depends on whether you are in Europe (18 months) or the US (age 5). If the child is under the age for surgical implantation, the BAHA can be worn on a headband

For auricular reconstruction, there are four different options:

1. Rib-Graft Reconstruction. Because the implant is the patient's own living cartilage, the ear continues to grow as the child does. The procedure is usually performed after age 6, one reason being to ensure that the rib cage is large enough to provide the donor material necessary. This is a three to five stage surgery. The number of surgeries can vary.
2. Reconstruct the ear using a Medpor polyethylene plastic implant. This is a two stage surgery which can start around age 3. Note that for patients with both Microtia and Atresia, that when using Medpor for the outer ear reconstruction the atresia repair must be done FIRST (as mentioned above with the rib graft reconstruction, the atresia repair is done AFTER).
3. Ear Prosthesis. A craniofacial prosthesis or auricular (ear) prosthesis is custom made by an anaplastologist to mirror the other ear. Prosthetic ears can appear very realistic yet they do require a few minutes of daily care. They are typically made of silicone which is colored to match your individual skin and can be attached using 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 optimal age to begin wearing an ear prosthesis is between the age of 6 and 9. The child should be mature enough to want and help care for the prosthesis. A person with grade I & II microtia need not consider an ear prosthesis. A person with grade IV (anotia) is best suited for an ear prosthesis. A person with grade III construction has three options for reconstruction.
   1. Leave the skin tags for future surgical reconstructive purposes and make an adhesive retained prosthesis over the top of the existing ear. The advantage is that you can keep your reconstructive options open and you get more definition in the ear than a surgical approach. This allows you to try out the prosthetic approach without burning any bridges. It is also the least expensive approach. The disadvantage is that the ear is typically placed lower and more forward and tends to appear more bulky than the other ear. It will give you a good outline though. Placement is more difficult than prosthetics option '2'. If you like the look of the prosthesis and want to make it more permanent, you can proceed with option '3'.
   2. Remove the skin tags and use an adhesive retained ear. The advantage over prosthetic option '1' is that your prosthetic ear can be a near identical mirror image of your other ear. Placement is much easier as well because the skin is flat. The disadvantage is that you remove the skin tags which are necessary for surgical reconstruction. You always have the option of placing the implants in the future.
   3. Remove the skin tags and simultaneously place the implants for a prosthesis. The visual results are very similar to prosthetic option '2'. The advantage is that placement of the ear becomes even easier and you eliminate the costs of adhesive and the associated daily care. The disadvantage is again that you limit your surgical reconstructive options.
4. Soft tissue reconstruction: The reasoning for soft tissue reconstruction is that surgically reconstructed ears using rib-graft or implants are sensitive, though the sensation is not the same as for normal ears due to the transplant of skin from other areas of the body.

Complications

Aural atresia is commonly associated with microtia. Atresia occurs because patients with microtia may not have an external opening to the ear canal, though the cochlea and inner ear are usually present. The grade of microtia correlates to the development of the middle ear^[4].

Microtia is usually isolated, but may occur in conjunction with hemifacial microsoma or Treacher-Collins Syndrome^[5].

Microtia can cause difficulties with wearing headphones and glasses^[6]. It is also occasionally associated with syndromes that can cause balance problems, kidney problems, and jaw problems, and more rarely, heart defects and vertebral deformities.

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. 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.

There are several organizations which provide information and support to affected people.

In some countries, the outer ear reconstruction is considered as a prosthetic surgery, which means that it is not necessary, and hence is not covered by the insurance or support groups help.

Some patients may opt to not pursue surgery. This is usually because the child has already adapted to the condition, and unless is driven by self-esteem or cosmetic issues, may prefer to leave the condition unchanged.

Diagnosis

Physical Examination

Ear Nose and Throat

• 

  Congenital microtia (small, malformed auricle / pinna)and external canal atresia.

• 

  Congenital atresia of the external auditory canal. The pinna is rather well formed.

• 

  Congenital microtia without canal atresia.

• 

  Supernumerary auricle.

• 

  Bifid earlobe.

• 

  Incomplete fusion of the incisura intertragica. A probe is inserted in the resulting fistula. The rest of the pinna is well formed. The external canal is open.

References

da:Mikroti