Neural crest defects. A neuroanatomic basis for classification of multiple malformations related to phocomelia.

Skeletal and internal structures are shown to be linked anatomically through segmental levels of innervation, or "neurotomes", and are related embryologically to the neural crest. Congenital abnormalities within the same or adjacent neurotomes would explain the distribution of defects in thalidomide embryopathy and morphologically similar multiple malformation syndromes. Classification of these "neural crest defects" on the basis of the segmental nerve supply is suggested.