Fundamentals of Hemifacial Microsomia

Hemifacial microsomia is a congenital condition characterized by varying degrees of hypoplasia of facial structures, including the mandible, ear, and facial nerve. While the exact embryologic etiology remains speculative, multiple risk factors for hemifacial microsomia have been identified. In order to describe the broad and varied range of deformities that may be present, multiple classification systems have been developed, including Pruzansky–Kaban and OMENS. The anomalies present in each case of hemifacial microsomia are treated according to traditional reconstructive algorithms. Mandibular hypoplasia can be addressed with mandibular distraction or traditional orthognathic surgery. Either autologous or alloplastic materials are used for ear reconstruction, while facial reanimation may be necessary if the facial nerve is severely hypoplastic/absent.