Hemifacial microsomia: use of the OMENS-Plus classification at the Royal Children's Hospital of Melbourne.

Hemifacial microsomia is the most common facial congenital disability after cleft lip and palate, but as yet its pathogenesis remains unknown. Clinical classification systems have evolved over the last 30 years from those classifying only single components of the disorder, to those classifying according to the combination of deformities, to the most recent systems that grade each anatomical component separately, such as the Orbit, Mandible, Ear, Nerve, and Soft tissue (OMENS) system. The aim of the present study was to review the classification of patients with hemifacial microsomia treated by the Melbourne Craniofacial Unit at the Royal Children's Hospital using the OMENS-Plus system of classification and to correlate the findings with data from other centers. Records of patients treated by the craniofacial unit were reviewed and included in the study if adequate clinical records, photographs, and radiographs (anteroposterior, lateral, basal cephalometry, panoramic views) were available. The data were entered into a database file developed for this purpose. Seventy-one patients were identified from the hospital database, of which six were excluded because of incomplete data. Of the 65 patients, there were 31 (48 percent) with right-sided microsomia, 25 (38 percent) with left-sided microsomia, and nine (14 percent) with bilateral microsomia, with an overall male-to-female ratio of 1.2:1. The majority of patients had a normal orbit (77 percent), mildly hypoplastic mandibular ramus-condyle with functioning temporomandibular joint (57 percent with type M1 or M2a), normal facial nerve (76 percent), and mild soft-tissue hypoplasia (73 percent). There was a similar proportion of patients with mild ear anomalies (53 percent with grade 0 or 1) compared with those with more severe anomalies (47 percent with grade 2 or 3). Correlative analysis demonstrated a slight but positive correlation between the severity gradings of the five individual components. The correlation was lowest between the grading of the nerve and ear and that of the mandible and nerve. The data demonstrate the phenotypic variability of hemifacial microsomia and suggest a degree of relationship among the components of hemifacial microsomia. The OMENS-Plus system has provided a major advancement in the classification of hemifacial microsomia. The authors suggest refinements to the grading of the orbit and nerve components.