Morphogenesis of the spinal canal, normal and stenotic.

The closest formative developmental dependence of the axial skeleton upon the morphogenesis of the intraspinal nervous structures is reflected in the roentgen features of the individual vertebrae as well as of the vertebral column in its entirety. The vertebroneural developmental events are characterized by a steady relative decrease in size of the nervous structures (the first to be laid down and huge in the embryonic period) under a corresponding increase in size of the skeletogenic tissues. There exists experimental evidence that the maintenance of the necessary developmental balance between the two tissues, the bony and the skeletogenic, is a function of the nervous substance. The tight spinal canal appears to result from a failure of the latter neural function leading to overgrowth of the bony structures, viz., to massive vertebrae and laminae encroaching upon the neural contents. Morphogenesis of the normal and tight lumbar spinal canal is discussed with special reference to the developmental interrelations between the cauda equina complex and the lumbar vertebrae.