• Hemifacial microsomia is associated with several soft tissue anomalies in addition to the common skeletal manifestations. These include, but are not limited to, microtia, facial nerve palsy, skin tags, soft tissue and muscular hypoplasia, microphthalmos, and macrostomia.
  • The facial deformities associated with hemifacial microsomia are heterogeneous and demonstrate extreme variability of expression. Previous work by Poswillo suggested that early vascular disruption of the developing stapedial artery with expanding hematoma during intrauterine development resulted in destruction of differentiating tissues within the first and second branchial arches. Since this initial hypothesis, additional hypotheses have been put forward for some of the other instances of hemifacial microsomia that occur. One theory involves failure of migration of the neural crest cells of the first and second branchial arches. Other possibilities have been cited such as disruption of the fetal tissues during the prenatal period.