The embryological basis of craniofacial dysplasias.

Craniofacial dysplasia of a syndromic pattern can usually be classified into one of two easily identifiable groups. In the first group are those malformations of the craniofacial skeleton and soft tissues that are asymmetrical in form and in the other, those that are principally symmetrical. Clinical studies have demonstrated that affected subjects in the symmetrical group frequently improve in terms of facial appearance as growth and development proceed to maturity, while those with asymmetrical defects often deteriorate in this respect. Embryological studies on animal models of these malformations have shown that asymmetrical lateral facial dysplasia and symmetrical mandibulofacial dysplasia exhibit discrete and widely disparate causal mechanisms of malformation. Analysis of these mechanisms and their effects on subsequent growth and development has suggested significant variations in the timing and technique of reconstructive procedures which will enable the surgeon to produce the most effective results when used for the rehabilitation of the afflicted.