Hemifacial Microsomia is a condition that effects the growth of the face unilaterally or bilaterally. The severity of this disorder can vary from mild to severe. Although different facial structures can be effected, the most common areas include the ear, the oral cavity, and the mandible.

Characteristics:
The physical features of Hemifacial Microsomia include the following:
Unilateral or Bilateral underdevelopment of the Mandible (lower jaw)
Unilateral or Bilateral underdevelopment of the ear
Unilateral or Bilateral reduction in size and flattening of the Maxilla (upper jaw)
Narrowing of the opening of the eye

Causes:
The origin of this syndrome is a vascular accident in the fetus. This accident causes the blood supply and production of blood clots in the area of those tissues which will develop into the structures of the ear and lower jaw. The amount of damage caused by the vascular accident is directly related to the period of development in which it occurs as well as the degree of tissue destruction that takes place. Since it is not genetically linked, most cases of hemifacial microsomia are sporadic and the risk of an effected individual to have an affected child is minimal.

Expectations:
Due to the delayed growth and development of the effected areas, the effects of this syndrome will be more evident as the child grows. The lack of the development of the upper and lower jaws can cause breathing problems as well as a dental malocclusion which will need to be addressed surgically and orthodontically.

Treatment:
For these patients, treatment generally requires the expertise of both a craniofacial surgeon and an orthodontist with experience with these problems. The jaw deformity is addressed as early as 3 years of age if the mandibular retrusion is severe enough to cause airway difficulty. This jaw reconstruction can be achieved by extending the mandible with a rib graft or with the utilization of a distraction device.

The distraction of the mandible involves cutting the bones of the jaw (a corticotomy) and placing two pins on either side of the corticotomy. Each day, the pins are manually pushed apart and new bone is generated in the area of the corticotomy. The best approach to reconstructing the jaw is determined by the surgeon and is specific for each patient. If it is needed, ear reconstruction is performed in four stages and usually begin at the age of six years. Throughout life, these patients must maintain adequate dental occlusion through ongoing orthodontic treatment.