Hemifacial microsomia

Hemifacial microsomia is a congenital disorder that affects the development of the lower half of the face, most commonly the ears, the mouth and the mandible. It can occur on one side of the face or both. If severe it can lead to difficulties in breathing, obstructing the trachea and requiring a tracheotomy. It is the second most common facial birth defect after clefts, with an incidence in the range of 1 in 3500 to 4500.

Other names
The condition is also known by various other names:
 * Lateral facial dysplasia
 * First and second branchial arch syndrome
 * Oral-mandibular-auricular syndrome
 * Otomandibular dysostosis
 * Craniofacial microsomia

Cause
The condition develops during the fetal stage of pregnancy at approximately 4 weeks of gestation, when some form of vascular problem leads to clotting and a poor supply of blood to the face. This can be caused by a physical trauma, though there is some evidence of it being hereditary. This restricts the developmental ability of that area of the face. Currently there are no definitive reasons for the development of the condition.

Severity
The severity of hemifacial microsomia depends on the extent of the physical injury (the area with a short supply of blood) and the gestational age of the fetus – the earlier the injury, the greater the chance of wide-scale problems.

In some cases, the central nervous system is affected, causing difficulties moving the face symmetrically.

Treatment
Depending upon the treatment required, it is sometimes most appropriate to wait until later in life for a surgical remedy – the childhood growth of the face may highlight or increase the symptoms. When surgery is required, particularly when there is a severe disfiguration of the jaw, it is common to use a rib graft to help correct the shape.

Patients can also benefit from a Bone Anchored Hearing Aid (BAHA).