Perspectives : The Role of Clinicians in Understanding Secondary Neurulation.

During the last two decades, there have been remarkable advances in knowledge regarding secondary neurulation. An increased number of cases of occult spinal dysraphism and progress in basic embryology research have provoked the continuous discovery of new disease entities and the reclassification of occult spinal dysraphic lesions. Examples of such changes are described. The characteristics of secondary neurulation compared with those of primary neurulation are listed and discussed. Our fundamental questions include what the evolutionary significance of secondary neurulation is and what the advantages of having secondary neurulation are. However, our current data and speculations are insufficient to support scientific inference. The direction of future progress of research in this field is predicted. The role of clinicians in this progress is emphasized.