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. Hemifacial microsomia shares many similarities with Treacher Collins syndrome.
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 clinical presentation of hemifacial microsomia (HFM) can be quite variable. In some children, just the ear is affected (microtia or a small, underdeveloped ear), and in other children, multiple parts of the face and body can be affected. While there is no grading scale that is in use universally, the OMENS scale (standing for Orbital, Mandible, Ear, Nerves and Soft tissue) was developed to help describe the heterogeneous phenotype that makes up this malformation. Children with HFM are at higher risk for hearing loss, and should have their hearing tested. A proportion of children with HFM will have extra-cranial anomalies, including abnormalities of the kidneys and cervical spine, which are important to detect early in childhood. Cognition and development is usually typical in children with HFM.
Some have hypothesized that 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. This has not yet been proven in an animal or human model.
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).
References
- ^ "Hemifacial Microsomia" at the Tennessee Craniofacial Center. Accessed 20 January 2008.
- ^ "Hemifacial Microsomia" at the Children's Hospital and Health System of Wisconsin. Accessed 20 January 2008.