[Maxillofacial abnormalities of syndromes of the 1st branchial arch].

Hemifacial microsomia and Treacher Collins syndrome are the most frequent among the first and second branchial arch syndromes to include anomalies of the facial skeleton. Hemifacial microsomia is almost always unilateral and is characterised by hypoplasia or agenesis of the mandibular ramus. Treacher Collins syndrome is always bilateral and involves specifically the zygomatic bones. The treatment of skeletal anomalies is seldom started before 10-12 years of age, except in severe form with major aesthetic impairment. Such cases are treated at the beginning of school age, on and after 6-8 years. Several operations, including osteotomies of the jaws and bone grafts, are usually necessary to achieve an acceptable result.