ABSTRACT
We report four patients who provide clinical evidence supporting the hypothesis that axial dysraphic states may result from a primary disturbance in the chordoaxial mesoderm. One infant had complete craniorachischisis, an omphalocele, and ambiguous genitalia. A second infant had anencephaly and an omphalocele. The third had iniencephaly. The fourth had cervical vertebral fusion defects, an occipital menigocele, and a laterality malformation sequence. Alteration in the development of structures derived from the chordoaxial mesoderm could explain all of the structure defects observed in the four patients. This hypothesis accounts for the nature of the defects seen in association with dysraphic disorders and for the genetic relationship observed between neural tube defects and vertebral anomalies.