What is hemifacial microsomia?

Hemifacial microsomia is a common congenital (present at birth) facial difference that causes asymmetric development of the face. Hemifacial microsomia can be associated with syndromes, including Goldenhar syndrome (also known as oculo-auriculo-vertebral spectrum). This condition can affect all structures of the face, but most commonly causes asymmetry of the eyes, jaws, ears, soft tissues of the face, and the muscles and nerves that allow a person to smile.

What causes hemifacial microsomia?

The cause of hemifacial microsomia is not known. The leading theory is that an abnormality or injury to an artery in the head during fetal development leads to abnormal development of the affected structures. Most cases of hemifacial microsomia are not genetic or inherited, though there are some inherited syndromes that do present with hemifacial microsomia.

What are the symptoms of hemifacial microsomia?

The most obvious symptom of hemifacial microsomia is facial asymmetry. While both sides of the face can be affected by symptoms (this is called craniofacial microsomia), it’s more typical that one side is more severely affected than the other.

Asymmetry of the lower jaw. The most common abnormality in hemifacial microsomia, asymmetry of the jaw causes a cant of the teeth that is visible with smiling, asymmetry in the lower face, and pointing of the chin to one side. Children with significant deformities of the jaw, particularly bilateral cases, may develop sleep apnea due to airway obstruction.

Asymmetric development or absence of the ears. The second most common abnormality in hemifacial microsomia, children may have one ear that is slightly smaller and/or more prominent than the other ear. In more severe cases, the ear may be underdeveloped or not developed at all, a condition known as microtia. Children without an ear canal may not have a fully functioning middle ear and often require a hearing aid or surgery to assist with hearing. Children with hearing loss in one ear often have difficulty locating sound sources. 

Other symptoms can include:

• Asymmetry in the size or position of the eyes (in severe cases).
• Asymmetries of the face caused by less-than-typical levels of fat in the tissues of the cheeks.
• Asymmetries of the muscles and in the nerves that move the face. Sometimes, the muscles of the palate do not work symmetrically and this can affect speech.
• More severe cases of hemifacial microsomia may present with abnormalities outside of the head and neck. These most commonly include abnormalities of the bones of the spine, kidneys and heart.

How is hemifacial microsomia evaluated?

Evaluation and treatment of hemifacial microsomia requires a coordinated team of specialists, including:

• Plastic surgeon
• ENT specialist
• Pediatrician
• Geneticist
• Ophthalmologist
• Dentist
• Orthodontist
• Audiologist
• Speech therapist
• Social worker

All of these specialists will evaluate the child and coordinate a comprehensive care plan.

As the child grows or when surgery is being considered, it will be necessary to determine the underlying anatomy that is causing their deformity. A surgeon, dentist or orthodontist will order appropriate X-rays or a CT scan to obtain the information needed.

Children with microtia will require regular testing by an audiologist to make sure they are hearing appropriately and that equipment, such as hearing aids, is working. 

Children with significant deformities of their jaws, problems with hearing or malfunctions of their palate may have difficulties feeding or speaking. A thorough evaluation by a speech therapist can help identify these problems and determine which treatments are necessary to improve function.

How is hemifacial microsomia treated?

Hemifacial microsomia often requires surgical procedures to treat the child’s facial difference. The technique and time when it should be performed are determined by the severity of the deformity and the child’s medical condition. 

Mandibular Reconstruction

Deformities affecting the jaws cover a broad spectrum. Some children have minor asymmetry that is not noticeable during conversation. Minor cases may not require surgery. 

The best time to treat jaw asymmetry is in a child’s teenage years, after they are done growing.  Orthognathic surgery, also called corrective jaw surgery, on the upper and lower jaws allows the surgeon to place the jaws where they should be located without the risk of a child outgrowing the correction. Surgeons use 3D imaging techniques and computer-assisted planning to prepare for this operation.

In children with more significant jaw deformities, waiting until they are fully grown may not be an option. Children born without a temporomandibular joint need to have one created. This is typically done between the ages of 8 and 12. The surgeon may use distraction osteogenesis (a technique separating two bone segments that allows new bone to fill the separation), or use a rib bone or leg bone (fibula) to create a new joint.

Children will often require orthognathic surgery after they have finished growing, however, Pre-teen surgery may also be preferred for children with sleep apnea or those who have significant stress due to bullying or peer pressure. These operations are typically done with a technique called mandibular distraction, in which the bone is gradually stretched using either an external or internally buried device. Mandibular distraction is performed in children 8 to 12 years old, although evidence now suggests that children tend to outgrow these corrections by the time they are teenagers and will require additional surgery. 

The surgeon will discuss these options to determine the treatment that is best for the child.

Ear Reconstruction or Construction

Ear deformities in hemifacial microsomia are variable. Children with an ear that is slightly asymmetric or prominent may benefit from an otoplasty procedure to create normal folds and reduce the ear’s prominence when they are old enough to discuss their desire for this surgery. Those with significant asymmetry or microtia may require construction of a new ear. 

Most children with microtia can have an ear created for them in early childhood. Children must be old enough to have sufficient cartilage in the ribs to create an entire ear, and mentally mature enough to undergo the process. Synthetic materials can sometimes be used for ear reconstruction. 

In most cases of microtia, an ear can be reconstructed in two operations. Many children benefit from a small follow-up operation to maximize the result. More complex cases require three or four operations to complete construction of a new ear.

• The first operation in microtia surgery requires the surgeon to carve an ear from rib cartilage and place it where the missing ear should be located.
• The second operation is performed 6 to 12 months later and involves elevating the ear so that it sticks out from the head. This is done using tissue taken from the scalp (TPF flap) or behind the ear, and a skin graft taken from another location.

Most children with microtia will require additional surgery to help them hear. Headband hearing aids are useful in small children, but eventually most families consider placing a bone-anchored hearing aid as a more permanent solution. Some children may be candidates for canalplasty, or creation of a new ear canal.  This is performed by an otology specialist, who can help determine if the child is a candidate for this surgery.

Consideration of these procedures should also be discussed with a plastic surgeon. If they are performed before ear reconstruction surgery, they may increase the risk of complications or compromise the outcome of ear reconstruction.

Facial Reanimation

Some children with hemifacial microsomia are born with congenital facial nerve palsy. These children may have difficulty closing the eye of the affected side or might have asymmetric smiles. These conditions should be discussed with a surgeon, who can determine if a procedure is appropriate to improve these conditions. Those who have more significant facial nerve palsy may not be able to move their face or smile. 

Several operations are available to improve this condition. Most commonly, the gracilis muscle is taken from the leg and transferred to the face. This small muscle is connected either to the facial nerve on the other side of the face or to a nerve used for chewing, and then to the corner of the mouth to allow a patient to move their cheek and create a smile. Alternative procedures use other muscles in the head and neck to assist with facial reanimation.

A surgeon will assess the child thoroughly and help select the best operation. Surgery for facial reanimation is typically performed when children are age 7 or older. Children must be mature enough to perform the exercises needed in order to create their new smile.

Fat Grafting

Children with hemifacial microsomia often have asymmetry of the soft tissues in their face. Structural fat grafting allows for fat to be harvested from other parts of the body using liposuction and transferred to the face. Typically, 60% to 80% of the transferred fat survives. However, repeated procedures are often necessary to achieve an optimal outcome.