Facial clefts and facial dysplasia: revisiting the classification.

Most craniofacial malformations are identified by their appearance. The majority of the classification systems are mainly clinical or anatomical, not related to the different levels of development of the malformation, and underlying pathology is usually not taken into consideration. In 1976, Tessier first emphasized the relationship between soft tissues and the underlying bone stating that "a fissure of the soft tissue corresponds, as a general rule, with a cleft of the bony structure". He introduced a cleft numbering system around the orbit from 0 to 14 depending on its relationship to the zero line (ie, the vertical midline cleft of the face). The classification, easy to understand, became widely accepted because the recording of the malformations was simple and communication between observers facilitated. It represented a great breakthrough in identifying craniofacial malformations, named clefts by him. In the present paper, the embryological-based classification of craniofacial malformations, proposed in 1983 and in 1990 by us, has been revisited. Its aim was to clarify some unanswered questions regarding apparently atypical or bizarre anomalies and to establish as much as possible the moment when this event occurred. In our opinion, this classification system may well integrate the one proposed by Tessier and tries at the same time to find a correlation between clinical observation and morphogenesis.Terminology is important. The overused term cleft should be reserved to true clefts only, developed from disturbances in the union of the embryonic facial processes, between the lateronasal and maxillary process (or oro-naso-ocular cleft); between the medionasal and maxillary process (or cleft of the lip); between the maxillary processes (or cleft of the palate); and between the maxillary and mandibular process (or macrostomia).For the other types of defects, derived from alteration of bone production centers, the word dysplasia should be used instead. Facial dysplasias have been ranged in a helix form and named after the site of the developmental arrest. Thus, an internasal, nasal, nasomaxillary, maxillary and malar dysplasia, depending on the involved area, have been identified.The classification may provide a useful guide in better understanding the morphogenesis of rare craniofacial malformations.