Hemifacial microsomia: assessment of classification systems

Hemifacial microsomia (HFM) represents a spectrum of congenital malformations involving embryological derivatives of the first and second branchial arches. The multiple anomalies that may exist in HFM present considerable variability in patients with the diagnosis. Numerous classification systems have been devised to facilitate the individualized components of this complex condition. Because multiple HFM classification systems exist, their utility is frequently confusing and selection of a particular system is indeterminate. Several of the better known systems are evaluated using patients with variable expressivity of HFM. This review suggests that there currently exists no ideal classification system for this association of developmental malformations. The systems that were found to be most complete are acknowledged and recommendations or modifications are suggested.