Microtia is a spectrum of ear deformities that ranges from, literally, a “small ear” to a complete absence of the external ear. Very early in the fetus’s life, the face begins to form from different growth centers. During this time, it is speculated that something occurs that leads to the lack of growth of the ear and possibly other parts of the face. Depending on the timing of the event that occurs during the fetus’ development, Microtia and other facial deformities can vary in severity.
Epidemiology
Microtia is thought to occur in approximately 1:7000 to 1:8000 births, with the right side being twice as likely to be deformed, and deformities occurring on both sides of the face in 10% of cases. The male:female ratio is variously reported as 2:1 to 3:1.
Classification
Grade 1 – all anatomical units are present but may be small or partially misshaped
Grade 2 – Some or most of the anatomic units are deficient or absent
Grade 3 – The ear is absent or near absent (lobular pattern Microtia)
Associated Pathology
The external ear deformity that is present may be part of a syndrome called hemifacial microsomia. For the same reasons that the ear failed to form normally, other portions of the face may also fail to form. This can be deficiencies in the maxilla, mandible, facial soft tissues, the eye, and the nerves that move the face. There can be many different manifestations of these issues, and a strong understanding of all of the variations and combinations, and the best course of action to take in each case, is essential for treatment.
Work up:
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Craniofacial Exam-Like all congenital facial deformities, a thorough exam by a trained craniofacial surgeon is the first and most important step. This should be done as soon as possible.
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Hearing Evaluation – Because the external auditory canal and the middle ear structures are often affected or absent, a formal hearing evaluation should take place early in life. In some cases, a hearing evaluation may be followed by specific exams such as a CT scan to assess the inner ear anatomy, or an ABI which will measure the degree of sensorineural or conductive hearing loss.
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Related Issues Evaluation-Comprehensive evaluations by an Oral Maxillofacial Surgeon, Ophthalmologist, Geneticist, and a Pediatrician round out the remaining exams to rule out related issues.
Options for Reconstruction:
The ear reaches 85% of adult size by age 6 and 95% by age 8. So, most reconstructive efforts are performed in this age range. There are three accepted forms of Microtia reconstruction. Each technique has its advantages and disadvantages, but the application of each technique needs to consider the individual patients’ case and the experience of the surgeon with the given procedure.
Autologous Rib Cartilage Reconstruction — This is the most commonly used technique utilized by craniofacial surgeons. This technique takes portions of the child’s ribs to create the ear framework. After this surgery, there are 2 to 3 additional procedures where the ear construct is elevated and the earlobe is rotated into the correct position.
Medpore Implant with TPF Flap — This is a technique where a preformed implant is utilized and covered with tissue beneath the scalp. This procedure does not require the harvesting of the tissue from the child, and may lead to a sharper, more anatomically correct reconstruction, with the additional advantage that it can be completed in only one surgery. The disadvantages of this operation are that it has a higher rate of implant infection, exposure and extrusion, and it eliminates the option of rib graft reconstruction.
Ear Prosthesis Reconstruction — This is an excellent option when the first two options have failed or as a first option in a person that has a procedure done later in life. With this technique, a metal post is surgically placed in the auricular bone. (“Auris” is Latin for ear. That’s where we get the name for the auricular bone.) A replica of the normal ear is made out of a prosthetic material, and it is attached to the metal post. The major advantage of this technique is that is the most aesthetically normal option and it has a lower instance of complications. The disadvantages are that it is less durable, and it will need to be replaced or repaired at some point in time. Also, since this implant is removable, there is a fair degree of potential loss and damage in the active life of a child.
