Hemifacial Microsomia/Goldenhar Syndrome
Hemifacial microsomia is an underdevelopment of the tissues on one side of the face that occurs in approximately one in 5,000 births. When eye involvement is present, it is also known as Goldenhar syndrome. It affects both sides of the face in approximately 15% of the cases. This condition results in an asymmetry of the face with malformation of the ear and an underdeveloped jaw on the affected side. The functional challenges of this condition include an abnormal bite, hearing loss and related psychosocial issues. This is the second most common facial birth defect after clefts.
Characteristics of hemifacial microsomia include:
- Short mandible canted to affected side
- Malocclusion with chin shifted to affected side
- Microtia or small, or absent, ear
- Diminished cheek soft tissues
- Macrosomia or lateral oral cleft
- Absence or dysfunction of facial nerve on the affected side
Up until fairly recently, this condition was called first and second branchial arch syndrome; even today, it is sometimes referred to by geneticists as oculo-auriculo-vertebral syndrome. The term craniofacial microsomia is sometimes used to describe individuals who also have involvement of the upper face and forehead.
At the current time, no specific gene has been identified that causes this condition, and it is very rare for someone with hemifacial microsomia to pass the trait on to his or her children. The exact cause of this condition remains unknown, but there was some experimental evidence published many years ago that suggested if a small blood vessel ruptures near the developing ear in mice before they are born, after birth they appear to have hemifacial microsomia. More likely, this condition results from an impaired flow of cells (called neural crest cells), which arise next to the spinal cord, and migrate to the face to form the facial skeleton; if not enough of these cells are able to successfully migrate to their intended location, that side of the face ends up being smaller.
Children with hemifacial microsomia have a smaller face on the side that is affected. Parents usually note that the corner of the mouth is higher on this side and that the chin does not exactly line up in the middle of the face. The lower jaw (mandible) is flatter and shorter, and the ear is either smaller or not formed at all (microtia). The jaw joint may be small or even completely absent. Some children will have a cleft extending off the side of the mouth (macrostomia), making the mouth opening larger. Some children will have weakness of the muscles on the affected side of the face. The child’s right side is more likely to be affected than the left side. Up to 25% of the cases are bilateral. Some children are very mildly affected, while others are significantly affected. Intelligence and development are normal.
If a child has a bump or benign tumor of the eyeball, called an “epibulbar dermoid,” then your child may have Goldenhar variant, which may be considered another type of hemifacial microsomia. Children with Goldenhar frequently have fusions of some of the vertebrae (spine) in the neck; however, this almost never requires any treatment.
Craniofacial microsomia is the term given to children with hemifacial microsomia who also have involvement of the upper face and forehead. Typically, the forehead is smaller and is not as far forward as that of the opposite side. The bones around the eye may also be recessed.
The treatment plan for a child with hemifacial microsomia depends upon the severity of the condition. Children who are more mildly affected might not need any intervention at all; whereas, severely affected children require more care. Some doctors believe that treatment should begin at an earlier age, and others believe it is best to wait until more growth has occurred. Mandibular distraction or traditional jaw surgery is needed if the discrepancy of the lower jaw and face are severe between 3-8 years of age. Sometimes a bone graft is used to lengthen the jaw and sometimes a distraction device is used. If a child has an ear anomaly, this is often addressed through multiple surgeries beginning around 7 years of age. Social stigmata usually begin around first grade, so this is the time to discuss intervention, but enough overall body size is needed to obtain the cartilage for reconstruction from the rib cage. If there are soft tissue changes around the lips (macrostomia) or eyes, these are often addressed surgically in the first two years of life. If a child has a facial nerve deficit, nerve grafting and muscle transfers for facial reanimation procedures can be started between 6-8 years of age.