What is Hemifacial Microsomia?
Hemifacial microsomia (HFM) is a condition in which the lower half of one side of the face is underdeveloped and does not grow normally. There may also be a smaller eye or an absent eye. It is the second most common congenital facial deformity after cleft lip and palate with a reported incidence of about 1 in 3,500-4,500 live births.
Hemifacial microsomia affects bone, muscle, fat, and nerves of the face. The condition is progressive and becomes evident as the child matures. The smile is typically slanted upward on the affected side. The child’s chin may also appear slanted. The soft tissue (skin and fat) in this area may be deficient, giving the cheek a flattened appearance. Small skin tags may also be present on the cheek or by the ear on the affected side. The jaw abnormality may range from a small but normally-shaped ramus and condyle (parts of the jaw), resulting in a mild asymmetry, to a complete absence of these structures, resulting in a more severe jaw deformity. Also the ear is either smaller or not formed (microtia). Affected children may have a related cleft lip/ palate or lateral lip cleft (macrostomia). Dentally, there is a shifting of the teeth in the mild cases, to severe crowding and possible missing or impacted teeth in the more severe cases.
Etiology of Hemifacial Microsomia
The possible causes involve the early development of the head and neck (branchial arches), occurring very early in the pregnancy (about 30-45 days). This is not related to anything the mother did or did not do during pregnancy. It is thought that it results from a hemorrhage of the stapedial artery which produces a hematoma in the area of the branchial arches.
Evaluation for Hemifacial Microsomia
Evaluation and treatment requires working closely together with the family to attain the best functional and aesthetic result possible. These infants may be at risk for breathing and feeding problems due to the jaw deformity and need to be evaluated if there are any indications of airway compromise or failure to gain weight. Occasionally a tracheostomy and/or gastrostomy are needed to help with breathing and feeding.
An Ear, Nose, and Throat (ENT) physician should be involved in the evaluation and treatment of any issues to maintain optimal hearing status.
An orthodontist will assess the growth of the facial structures and monitor the eruption of the teeth. At appropriate times various orthodontic interventions will be initiated.
Treatment of Hemifacial Microsomia
Our treatment plan depends on the severity of the child’s condition with HFM. If a cleft lip/palate or macrostomia is present, surgical repair begins at about 3-4 months of age and skin tags may also be excised if present at that time.
The surgery to correct the severe underdevelopment of the lower jaw involves bone grafts using the child’s ribs to lengthen the jaw or by the technique called distraction osetogenesis (placement of a metal device used to lengthen bones). The external ear deformity is typically reconstructed between the ages of 5-7 years old.