In discussing the well known pathologic entity of achondroplasia, the textbooks mention that the disturbance in growth takes place in the bones of the extremities and in those of the pelvis and the skull, and point out that the spine is usually not involved in the process. But it is known that achondroplastic infants are frequently stillborn, and in these cases the spine also may demonstrate marked, even the severest, disturbances of growth, so that the trunk and the extremities together may not be more than one and one-half times the length of the skull. In these cases there is a premature bony union between the vertebral body and the neural arch, bringing about a narrowing of the spinal canal, which is probably the cause of death in the achondroplastic fetus. The foramen occipitale magnum especially seems to be narrow, thus causing a compression of the medulla oblongata.
FREUND E. SPASTIC PARAPLEGIA IN ACHONDROPLASIA. Arch Surg. 1933;27(5):859-867. doi:10.1001/archsurg.1933.01170110044003