The pattern of neural tube defects created by secondary reopening of the neural tube.

The usual location of human neural tube defects at the rostral or caudal end of the primary neural tube suggests they are caused by failure of closure of the neural tube. In this study, neural tube defects were created by surgical reopening of the neural tube of 3-day-old duck embryos in one of three sites: the forebrain, cervicothoracic region, or thoracolumbar region. It was determined that of the 31 survivors with forebrain incisions, 39% had exencephaly; of the 42 survivors with thoracolumbar incisions, 31% had myeloschisis; but of the 37 with a cervicothoracic incision, only 14% had exposed spinal cord. This indicates that a rostral-caudal distribution of neural tube defects can be seen in a model created by secondary reopening of the neural tube.