Congenital alar field defects: clinical and embryological observations.

Congenital malformations of the nasal ala may occur as isolated unilateral nasal alar defects or as part of more severe facial clefting syndromes. The embryologic significance of the isolated alar deformity seems separate from other craniofacial deformities and justified comment. Clinical examples of isolated nasal alar malformations are correlated with a study of 60 human embryos ranging from seven to 10 weeks gestation. These studies indicate that the nasal and alar developmental fields each have a separate critical time during which cells are most susceptible to altered development.