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Hemifacial microsomia is a broad term encompassing various bony and soft tissue abnormalities affecting the eyes, zygomatic bones, mandibular bones, ears, and mouth. Its severity varies widely, with different names based on the affected areas. Common examples include preauricular tags, macrostomia, and microtia. Hemifacial microsomia ranks as the second most prevalent craniofacial disorder in children, occurring in about 1 in 5,600 births, surpassed only by cleft lip and palate.
It is generally believed that this condition arises during embryonic development when the growth of the first and second branchial arches is impaired. These arches involve structures like the zygomatic bones, ears, and mandibular bones. The bones and tissues in these regions are impacted, leading to various names depending on the extent of involvement. The mandibular bone is the most commonly and significantly affected area in hemifacial microsomia. Abnormalities in the mandibular bones can influence surrounding structures. For instance, underdevelopment on one side may cause compensatory deformities in the maxillary bones on the opposite side, along with issues in the zygomatic bones, ear canal, ears, temporomandibular joint, and even the eyes. In cases involving the spine, it is termed Goldenhar syndrome.
In addition to the mandibular bone, other parts may be involved, such as:
The mandibular bone's shape is central to hemifacial microsomia, so the most common classification divides it into four types based on this. Other systems exist, like the SAT and OMES methods, considering factors such as eyes, ears, and nerves. The Pruzansky classification is the simplest and most widely used:
Macrostomia is a rare craniofacial anomaly, affecting 1 in 60,000 to 200,000 individuals. It results from inadequate development of muscles and skin (or bones) at the mouth corners during embryogenesis, leading to enlarged corners and difficulty closing the mouth. Prominent symptoms include milk leakage during infancy. It often co-occurs with preauricular tags, and some infants may have underdeveloped jawbones.
Surgical intervention is typically advised at three months of age, involving suturing the mouth corners and possibly removing preauricular tags. Scars generally heal well. If scarring remains a concern later, options like laser resurfacing or fat injections can improve appearance.