What is Ear Microtia?
Ear microtia is a birth defect where the outer part of the ear, known as the pinna, is underdeveloped, varying from being slightly smaller than normal to completely missing. The most severe form is called anotia; in this case, the entire ear and earlobe are completely absent. Usually, microtia affects only one ear, causing an imbalance in appearance. Various causes are associated with this condition, including issues with the baby’s blood vessels or if the mother takes certain medications during pregnancy.
Birth defects like this often cause trouble in hearing because of the malformed or missing outer ear. What adds to this problem could be ‘aural atresia’, a condition involving a failure in the development of the middle ear and the external ear canal. The abnormalities within the ear often correspond to the severity of the visible deformities. As microtia’s treatment often revolves around fixing the features of the outer and middle ear, teamwork between plastic surgeons and ear specialists is crucial.
Children born with this type of physical difference may feel self-conscious and face bullying from their peers. For this reason, it’s common to try and correct the problem before the child begins school, to reduce the risk of any negative social experiences. Treatments can range from simple observation to more complex ones like hearing aids, prosthetic ear attachments for aesthetic improvements, or even surgical interventions, such as using an artificial implant or grafting cartilage harvested from the ribs.
Technological advances have allowed surgeons to postpone invasive treatments until the child is about 10 years old. This delay allows for enough rib cartilage to be available for reconstruction and ensures the child can actively participate in their own aftercare. Some implants can be used in younger children, usually between ages 3 to 5, although there is a higher risk of infection and implant malfunction. Performing the ear reconstruction is challenging and may lead to complications, so it should only be done by an experienced medical team.
A clear understanding of the ear’s anatomy is essential to assess and manage microtia. The visible part of the ear, the auricle or pinna, plays a critical role in collecting sounds and directing them into the ear canal. The rigid structure under the skin, known as cartilage, is often underdeveloped in microtia cases, leading to abnormalities in the ear’s appearance. The different parts of the ear, like the helix (the outer rim), the antihelix (the inner curved ridge), the tragus (a small triangular projection near the ear canal), and more contribute to the ear’s overall shape and function.
In the instance of an underdeveloped or missing ear structure in microtia, these parts are recreated. Surgeons aim to improve both the ear’s looks and its ability to channel sounds to the eardrum. A thorough grasp of the ear’s anatomy helps surgeons plan and carry out these procedures more effectively.
What Causes Ear Microtia?
The development of the ear is a complex process that involves different layers of tissue developing into the inner, middle, and outer ear. The outer part of the ear develops from a layer of tissue called the ectoderm and forms six small hills-like structures, known as the hillocks of His, by the sixth week of pregnancy.
Scientists have had discussions about exactly how the hillocks contribute to the final shape of the outer ear, but recent research suggests that the first three hillocks (which comes from the 1st branch of the ectoderm) form parts of the ear such as the tragus, the helical crus, and the helix. Other parts of the ear, like the antihelical crura, antihelix, and the lobule, form from the 2nd branch.
An artery in the ear, called the stapedial artery, also develops from the 2nd branch. If this artery doesn’t develop properly, it can result in a condition called microtia, which affects the size of the ear. By the 22nd week of pregnancy, the six hillocks merge to form the auricle, or the visible part of the ear. The ear grows to 85% of its adult size by age five and is usually fully developed by age eight.
Microtia can occur by itself, or it can be related to certain genetic facial conditions like Goldenhar, Treacher Collins, Nager, Crouzon, Pierre-Robin sequence, and CHARGE syndromes. Some drugs, including isotretinoin, thalidomide, alcohol, and mycophenolate mofetil, can also cause microtia. Other factors that might increase the risk include the mother’s age and the number of pregnancies, the father’s age, high altitude (above 8,200 feet), and low birth weight.
Risk Factors and Frequency for Ear Microtia
Microtia is a condition that usually affects one ear (77% to 93% of cases), and most often it is the right ear (60% of cases). This condition happens more frequently in males than females with a ratio of 2.5 to 1. In the United States, for every 10,000 births, between 1.8 and 3.5 babies are born with Microtia. The numbers worldwide vary from 0.4 to 8.3. In the United States, Microtia is more commonly seen among Asians, Pacific Islanders, and Hispanic individuals.
Signs and Symptoms of Ear Microtia
Microtia is a condition that people are usually diagnosed with just after they’re born or while they are still infants. This condition, which affects the ear and is usually present at birth, can be spotted during normal newborn check-ups. There might be a genetic component to microtia, especially if it runs in the family, but it can occur randomly without any family history too.
Microtia can occur alone, or alongside other birth defects, such as problems with hearing, uneven facial features, inner ear disorders, heart defects, or kidney malformations. The presence of these associated conditions can influence medical decisions and the prognosis. Patients with this condition may have been through various medical tests and treatments. They may also face challenges related to body image, self-confidence, and acceptance by their peers.
When a baby is born, a normal, fully developed human ear is about 6 cm in height, slopes 20° backwards from vertical, and has a distance of about 2 to 2.5 cm from the edge of the ear to the bone behind the ear. In the case of microtia, the ear is not fully developed. In some cases, only parts of the lower ear and outer edge are visible. Doctors performing a medical examination will not only look at the ear but also consider the jaw bone, mouth, palate, eyes, facial nerve, and the color and quality of the skin. They should also note the position of the hairline on the sides of the head and the remaining ear structure.
If microtia is associated with genetic syndromes, doctors should also examine and document any other features related to these syndromes. It’s not uncommon to see issues such as uneven facial features, preauricular pits (small holes in front of the ears), extra parts of the ear, or a closed or absent ear canal. They also compare the size and form of the two ears.
A common issue for patients with microtia is that they often have conductive hearing loss. Age-appropriate tests using a tuning fork may be performed to confirm this.
Testing for Ear Microtia
Microtia is a condition where the outer ear or ‘auricle’ isn’t formed properly. It’s graded based on severity using different classification systems like the widely-used Marx Classification, which has four grades:
* Grade I: Here, the ear seems slightly smaller than average, but all its parts are usually present.
* Grade II: The ear is visibly smaller, and some parts of it are severely underdeveloped or missing. Usually, the top part of the ear is less developed than the bottom part.
* Grade III: In this grade, there’s a small piece of cartilage left in the top part of the ear, and the lobule (the bottom, fleshy part of the ear) is shifted forward and upward. This is sometimes referred to as a ‘peanut ear’ and is the most common form of microtia.
* Grade IV: This is the most severe grade, where the outer part of the ear and the lobule are completely missing.
Another classification, called the Nagata Classification, is used to guide the approach to surgical ear reconstruction. The categories in this system are: lobule type (ear looks like a ‘sausage’, with many structures missing, similar to Marx Grade III); concha-type deformity (lobule, concave area, a pointy projection and gap are present, but the ear canal and top part of the ear might be missing); small-concha type (similar to lobule type but with an extra tiny indented area), and anotia (most severe form, where the outer ear is entirely absent).
Infants with microtia or aural atresia (an ear abnormality that can lead to hearing loss) should have their hearing checked early on. These conditions can result in 50 to 65 dB hearing loss, though some may also have simultaneous damage in the inner ear parts responsible for hearing.
One should not assume that the unaffected ear is normal. A type of high-resolution CT scan of the ear bone is usually done when the child turns six (before this age, the exposure to radiation may be risky), this scan helps grade the severity of aural atresia and assess the child’s suitability for surgery.
The Jahrsdoerfer grading scale is used here. Patients scoring seven or more have better chances of improved hearing after surgery. Points are given for the presence and condition of specific ear structures. For example, 2 points for the presence of a stapes (one of the tiny bones in the ear), and 1 point each for various other structures, including a normal outer ear. The scale ranges from 10 (excellent) to less than 6 (poor candidate for surgery).
Treatment Options for Ear Microtia
Managing a microtic ear, a condition where the ear is underdeveloped, can range from simple observation and prosthetic ear placement to surgical reconstruction using implants. If the abnormality is minor, correction might not be necessary. However, when improvements in appearance or function (like wearing glasses or hearing aids) are desired, parents usually opt for intervention.
A prosthetic ear, which matches the color and appearance of the other ear, can be attached to the head with adhesive, clips, or magnets. However, it can be expensive, and there’s a risk of a young child losing it. In certain conditions like changing skin color between seasons, two prosthetics may be required, and they generally wear out after a few years.
One surgical method uses HDPE (High-Density Polyethylene) implants, a technique gaining popularity due to its significant advantages like natural-looking ear contours, shorter surgery time, less postoperative discomfort to the patient, and no need for cartilage harvesting. This procedure also allows for earlier surgery as it doesn’t need time for cartilage maturation.
Another surgical approach is autologous rib cartilage grafting, which involves creating an ear framework from rib cartilage. This technique was first described by Tanzer, then modified by Brent and later by Satoru Nagata. They all involved different stages and techniques, but the concept remained the same. However, this approach requires multiple donor sites for grafting, which may include the groin, scalp, or the other ear.
Nagata’s method involved reconstructing the ear in just two stages. He harvests and implants the cartilage framework almost exactly like Tanzer and Brent. But, at the same time, he positions the lobule (the ear’s fleshy lower part) and shapes the tragus (the small pointed part of the external ear) because, in his method, the tragus is part of the cartilaginous construct instead of a separate piece.
Some revised versions of Nagata’s 2-step technique, like those proposed by Kurabayashi et al. and Fisher, aimed to be less invasive, more effective, and avoid the need for follow-up surgery. It involved creating a small pocket through a TPF incision, which avoids complications linked with extended incision.
When deciding upon surgical repair, surgeons must consider whether the patient had previous surgery or trauma to the area. Also, the patient must be willing to participate in postoperative care and have adequate rib growth for the procedure. Certain patients, like those with collagen or vascular diseases and limited tolerance for long surgeries, might be better suited for prosthetics rather than autologous reconstruction.
For patients with congenital aural atresia, or a birth defect that causes the ear canal to be underdeveloped or absent, the timing of atresiaplasty (a surgical procedure to correct this defect) depends on the type of reconstruction. In all cases, decisions must be tailored to suit the patient’s unique situation.
What else can Ear Microtia be?
Microtia, a condition where the ear is underdeveloped, is often linked with birth defects. It can occur as part of certain syndromes like Goldenhar, Treacher-Collins, and Melnick-Fraser. Sometimes, typical defects such as prominauris (protruding ear), cryptotia (hidden ear), cup or lop ear deformity, Stahl’s ear (pointed ear), and lobule deformities (earlobe issues) may be confused with microtia.
However, the soft cartilage of a newborn’s ear still retains flexibility due to the influence of the mother’s estrogen present in their system. As a result, this allows these conditions to be treated effectively within the first 3 weeks after birth using a technique that reshapes the outer ear. It’s important to note that severe cases of microtia, specifically grades 3 and 4, often come with aural atresia, a condition where the ear canal is underdeveloped or absent. This should be evaluated by a health professional accordingly.
What to expect with Ear Microtia
The future outcome of microtia – a condition in which the ear is underdeveloped – varies based on when treatment begins, the procedure used, and how the patient responds to treatment. Bone-anchored hearing aids can be successfully used to treat hearing loss associated with this condition. Sometimes, if the underdeveloped ear is small, it can be hidden with the patient’s hair, or a prosthetic ear could be used, creating a normal-looking ear that won’t attract attention and can even hold glasses.
A study led by Chunxiao found that following a specific procedure known as ACC, patients were most pleased with the appearance of the outer folded part of the ear, known as the helix, but were less satisfied with another part of the ear, the tragus. Due to the possible complications with ACC, it’s important for doctors to discuss the outcomes and problems that may arise before the surgery. This can help manage patients’ expectations and enhance their satisfaction. Regardless, most people are usually happy with their surgically-reconstructed ears, as they often feel that the reconstructed ear is a part of them – a feeling they don’t usually get with a prosthetic ear.
Possible Complications When Diagnosed with Ear Microtia
Complications specific to ACC reconstruction include problems such as pneumothorax (a type of collapsed lung) caused by costal cartilage harvesting, cartilage infection (usually by Pseudomonas aeruginosa bacteria), cartilage framework extrusion (pushing out of the frame), changes in framework size, lobule necrosis (tissue death), and construct displacement (shifting of the cartilage framework). The cartilage framework often extrudes over the top of the ear and is usually treated with different techniques that involve skin or tissue flaps. The top of the ear tends to have a weaker blood supply on the reconstructed ear, and this usually needs to be fixed with surgery.
On the other hand, procedures involving HDPE (a type of plastic) implants can cause compression ischemia, which can result in skin loss and issues with skin flaps. Although usually strong in the long term, these implants can be more susceptible to extrusion (coming out of the skin) or infection, particularly after minor injuries, compared to constructs made from the patient’s own cartilage.
Generally, both ACC reconstruction and HDPE implantation procedures can share typical post-surgical complications such as:
- Pain
- Bleeding
- Swelling
- Infection
- Scaring
- Damage to surrounding structures
- Secondary (follow-up) surgeries
In addition, the facial nerve might get damaged due to unpredictability of the anatomical structure in a maldeveloped ear, especially during ear canal repair. Both cartilage constructs and HDPE implants can shift after placement, usually in the bottom front direction, although it could also be hard to determine the right location for the initial placement. Some patients with ear malformation conditions also have facial malformation conditions and lower hairline on the side of the affected ear, leading to hair growth on top of the reconstructed ear, which might require laser removal.
As for prosthetic ears, they usually have a limited lifespan and may need to be replaced overtime due to wear and tear, changes in skin tone or texture, or damage from external elements. Frequent replacements may be costly, particularly if the prostheses are misplaced or damaged.
Preventing Ear Microtia
Preventing microtia, a condition affecting the ear, can involve several steps. To stop it from happening in the first place, you can take actions like getting good prenatal care during pregnancy to identify and address any potential risks, avoiding exposure to harmful substances known to cause birth defects, and seeking genetic advice if your family has a history of this condition.
Even after the condition has occurred, it can still be managed early and its effects minimized. This involves efforts such as detecting the condition before birth using ultrasound, quickly diagnosing and treating it after birth, and proper management to reduce its impact on the person’s health and quality of life.
Those with microtia and their families need to be guided through the available treatment options. Regular check-ups with various specialists can help alleviate the physical and emotional strain it can inflict. It’s critical to discuss when interventions should take place. Also, surgical options for related conditions, like blocked ear canals, should be taken into account.