Hemifacial Microsomia

What is hemifacial microsomia?

Hemifacial microsomia (HFM) is a congenital condition, meaning that it is present at birth, as opposed to being acquired during or after birth. Hemifacial microsomia is the second most common facial birth defect after cleft lip and cleft palate. It occurs in approximately one in 3500-4000 live births.

In children with HFM, part of one side of the face is small or underdeveloped. It usually affects the ear, mouth and jaw – and sometimes also the eye, cheek and neck. In 10-15 per cent of cases, both sides of the face are affected. HFM can be associated with facial palsy.

Hemifacial microsomia (also known as craniofacial microsomia, oculo-auriculo-vertebral spectrum, or oculoauricular dysplasia) is a generic term covering many variants, such as Goldenhar syndrome, facio-auriculo vertebral syndrome, branchial arch syndrome, otomandibular dysostosis and lateral facial dysplasia. All the different names are used for historical reasons and refer to different severities of the same condition.

What causes hemifacial microsomia?

Scientists do not know yet what causes HFM. We now know that it involves abnormal cell formation and migration during development of the face. It may be induced by a vascular problem leading to a poor supply of blood to the face of the fetus. The process starts in the first three months of pregnancy. Research has established that HFM is not triggered by something the pregnant mother did or did not do.

In a vast majority of cases, HFM is not inherited and occurs by chance. However, if a couple has had a child with HFM, the risk that they will have another child with this condition increases to about two to three per cent. An adult born with HFM has approximately a three per cent chance of having a child with HFM.

What are the symptoms of hemifacial microsomia?

Symptoms of HFM range from barely noticeable to severe. For instance, some babies with HFM may be born with a slightly smaller jaw, with a skin tag (small growth of skin) in front of an otherwise normal-looking ear. In other babies, one side of the face will look much smaller than the other, with a very small, abnormally shaped or even absent ear. There are many ways to describe and classify the appearance and function in HFM; one such system is the OMENS classification. The letters in OMENS stand for:

• Orbit (or eye socket): the cavity in the skull that contains the eye
• Mandible: the jawbones
• Ear
• Nerve
• Soft tissues (in anatomy, this refers to skin, muscle, fat, tendons and ligaments – amongst other tissues that are not bone).

Common features of hemifacial microsomia include:

Orbit:

• Normal
• Small orbit and eye with normal vision
• Small, underdeveloped eye (microphthalmos) with impaired vision
• Absence of the eye (anophthalmic orbit)
• Benign growths on the eye (epibulbar dermoids)

Mandible:

• Underdevelopment of the upper and lower jaws on the affected side. They may be short and/or crooked.
• Missing or overcrowding of teeth
• Cleft lip and/or palate
• Limited opening of the mouth (trismus)
• Non-opposing bite (malocclusion)

Ears:

• Small tags of skin in front of the ear
• External ear misshapen, very small, or even missing
• Ear canal abnormally developed, or absent (aural atresia), resulting in partial or complete hearing loss

Nerve:

• Partial or complete facial paralysis due to the facial nerve being affected

Soft tissues:

• Flat cheekbone and unequal cheek fullness (underdeveloped bone, muscle and fat)
• Flattened forehead
• Asymmetric mouth with wide lateral cleft (macrostomia)

Other parts of the body:

Most babies with HFM have facial differences, but no other medical problems. In a minority of cases, babies with HFM may also have malformed vertebrae (bones of the spine), heart defects and abnormally shaped kidneys.

How is hemifacial microsomia diagnosed?

Doctors will examine the child’s face and head carefully, paying particular attention to their ears, jaws and teeth. This will help them determine is your child has HFM or may be suffering from another condition.

X-rays, Magnetic resonance imaging (MRI) and computed tomography imaging (CT scan) will be used for a more accurate diagnosis. X-rays produce images of internal tissues and bones of the head. Magnetic resonance imaging show very accurate cross-sectional views (slices) and 3D views of soft tissue and do not expose the patient to X-ray radiation. CT scans take cross-sectional views (‘slices’) of the body, showing the bones, organs, muscle and fat in great detail. And, as appropriate, these can also be viewed in 3D. CT Scans are particularly helpful in showing detail relating to bony structures.

In some cases, additional tests may be required, such as a renal ultrasound to make sure that the kidneys were formed normally; X-rays of the top part of the spine (cervical spine) to look for differences in the way that the bones fit together; and/or an echocardiogram (ultrasound picture of the heart) to check for abnormalities, if heart problems are suspected. (An ultrasound scan uses high frequency sound waves to create images of organs and structures inside the body.)

What are the treatments for hemifacial microsomia?

Hemifacial microsomia is a complex condition, requiring the skills of several specialists working together: plastic and/or maxillofacial surgeons, ENT (ear, nose and throat) doctor, neurosurgeon, orthodontist, ophthalmologist, speech therapist… Not all children with HFM have the same medical problems, so the treatment options vary widely. They will also depend on how much the child is affected, and on their age: the timing of the treatments is crucial because a child’s face keeps growing. All children with HFM require long-term follow-up.

Below is a list of possible medical problems, and the treatment options:

• Ears: skin tags can be easily removed at around one year of age. Surgery can improve the malformed ear, after the child is at least six years old. Ear reconstruction using cartilage from the rib is a multiple-stage process, with several months in between procedures. In some cases an artificial (prosthetic) ear made of silicone can be fitted.
• Mouth: a cleft lip can be surgically repaired when a baby is about four months old. A cleft palate is usually operated on when the child is one year old. Children with macrostomia (‘wide mouth’) will need surgery to make a complete ring of muscle around their mouth.
• Eyes: epibulbar dermoids (growths on the eye) should be monitored by an ophthalmologist to make sure they do not interfere with the child’s sight. A small eye socket may be enlarged. If there is no eye, it may be necessary to make an eye socket for an artificial eye.
• Jaw and teeth: in the more severe cases, when the child is at least four years old, a bone graft using a piece of bone taken from the ribs may be considered to lengthen the jaw. Another procedure called ‘distraction osteogenesis’ is another option to increase the size of a child’s lower jaw: it involves moving two segments of the jawbone slowly apart in such a way that new bone fills in the gap. General dental health and crowding of the teeth should be regularly monitored by a dentist and/or orthodontist. Some children may need a dental appliance or braces. For moderate jaw asymmetry (the most common situation), orthognathic surgery to straighten the jaw can be performed in their late teens. As facial growth continues until the late teens, surgeons generally try to leave surgery until this time otherwise surgery may need to be repeated as the face continues to grow after surgery.
• Facial palsy: when present, facial paralysis may improve during the first few years of life. Various medical treatments, therapies, and surgeries can help with facial palsy.
• Facial contour: if the tissue of the face is underdeveloped, it can be replaced with skin, fat and sometimes muscle taken from another part of the body. Bone grafts taken from the skull or the hip may improve the facial shape. Fat injection is becoming a very common method of improving facial contour.
• Feeding and breathing problems: babies who have a small jaw and/or a cleft palate, or macrostomia (‘wide mouth’) may have difficulty feeding. It will be essential to check that they are gaining weight appropriately. If breathing is a problem, some options are available to manage and correct the cause, such as positioning devices, tubes and jaw advancement procedures.
• Hearing impairment: after thorough hearing testing, an audiologist and an ENT doctor will determine the best ways of managing the child’s hearing, and whether hearing aids are needed. When the growth of the ear is nearly complete (at about four years old), a CT scan to examine the middle and inner ear may be helpful to find out whether surgery to restore hearing is likely to be successful.
• Speech problems: some children with HFM have abnormalities in the muscles in the back of the mouth, which can lead to differences in the way they speak. In other cases, speech problems are caused by the loss of hearing. In these instances, speech therapy is indicated.