​Hemifacial Microsomia


What is it?

Hemifacial microsomia is a condition where the bones and soft tissues of the face do not grow and develop appropriately. This can happen on one (“hemifacial”) or both sides of the face. Asymmetry between the two sides of the face can cause problems with the bite, eating, movement of the face, and appearance. Hemifacial microsomia is actually fairly common, occurring in 1/5,600 births. We don’t know exactly what causes it, only that something happens during pregnancy to disrupt the normal formation of the structures of the face and skull. It also occurs with a wide spectrum of severity. Some patients are affected so mildly that they will not need significant treatment. In general, there are several different structures of the face which may or may not be affected in each individual. We classify these by the acronym “OMENS”. OMENS stands for: Orbit, Mandible, Ear, Nerve, and Soft tissue. In patients with hemifacial microsomia, the eye may be small or malpositioned, and the upper or lower jaw may be small, or parts of them may even be missing. Often the external ear is poorly formed with just a small piece of tissue and cartilage present (microtia) or absent (anotia), and the hearing can be affected as well. The facial nerve may be weak or non-functional in 15-30 % of children, which will affect facial expression. Additionally, the soft tissues may be underdeveloped (including muscles and fat), further adding to the small and gaunt appearance of that side of the face. All of this can cause dental problems, difficulty eating, speaking, and even breathing. Generally, the appearance of the face is also very uneven.

What are the treatment options?

Treatment varies depending on what structures are affected, as well as the severity. Eye abnormalities are generally not severe enough to warrant surgery, and can be followed by an ophthalmologist. When the mandible is affected, orthodontics will be required to straighten the teeth and the bite. If the abnormality is more severe, surgery may be needed. The goal of surgery is to lengthen the short side of the mandible so that the chin and jaw are more symmetric and the bite is straight. In some cases, this can be done by distraction. However, if a significant amount of bone and/or the joint is missing, reconstructing the mandible will require taking bone from the rib or the leg. Your child will be followed by an ENT physician who will determine what therapies are available for any hearing loss that might be present. Ear abnormalities are generally significant enough that they will require completely reconstructing the ear, or the use of a prosthesis (please see the ear reconstruction section for more details).

If the facial nerve is functioning but has some minor weakness, there is usually not much to do. If there are certain muscles that are obviously weak, Botox can be injected into the normal muscles on the other side and make movement across the face more symmetric. If you are pleased with the results of the botox, then those muscles can be permanently weakened with surgery. If there is severe weakness and poor function of the facial nerve, different techniques may be attempted to restore function.

Often one side of the face will appear thin and gaunt compared to the other because of missing muscle and fat. This can be effectively camouflaged by fat grafting. Fat grafting works by removing fat from other areas of the body (like the abdomen or buttock) via liposuction, preparing the fat, and then injecting it into the areas that need to be plumped. Usually, about 75% of the fat survives and 25% is lost. Because of this, we usually put in a little more than is needed at the time of surgery. More than one session of fat grafting may be necessary to achieve the desired result. Because every child with hemifacial microsomia is so different, we will work closely with you to come up with an individualized treatment plan for your child that fulfills all of their needs.

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