Pathogenesis of diastematomyelia: can a surgical model in the chick embryo give some clues about the human malformation?

Abstract

To reproduce diastematomyelia, a sagittal incision was carried out at the level of the rhomboidal sinus of 36- to 40-h-old chick embryos. A small piece of membrane shell, a small agar screen, or a piece of quail isochronous isotopic notochord was inserted into the gap. The embryos were killed and fixed after 9 days' incubation. Diastematomyelia was obtained in several embryos treated with interposition of a membrane screen or a piece of quail notochord. Microscopic examination revealed two hemicords, each containing its own central canal; in some cases one of the cords showed hydromyelia. Absence of the rump was seen in association with experimental diastematomyelia. The interposition of a resorbable agar screen did not succeed in reproducing diastematomyelia. The results of these surgical manipulations suggest that diastematomyelia cannot be explained by a primary disorder of neurulation. It supports the theory of noninvolution of a firm midline structure (probably the neurenteric canal, rapidly surrounded by mesodermal cells originating from the notochord), which prevents the fusion of the separated parts.

An Experimental Animal Model of Split Cord Malformation

“…However, the notochords in these embryos were not split at the same level as seen in SCM. Similar malformations have also been observed in avian embryos [6]. In our present study, an experimental animal model of SCM was produced by the surgical induction of a fistula that mimicked a neurenteric canal, and we examined the relationship between an accessory neurenteric canal and SCM.…”

“…Klessinger et al [5]and Rilliet et al [6]reported an experimental animal model for this condition in avian embryos. In this present study, we experimentally produced SCM in Cynopus pyrrhogaster.…”

Experimental Split Cord Malformations

“…Due to the absence of a suitable animal model, none of the hypotheses have been verified experimentally, despite experimental models that show split neural tubes in embryos [6, 7, 8, 13]. This is the first report of an experimental animal model of ‘true split cord malformation’, in which double spinal cords were developed in the spinal canal.…”

Cutaneous manifestations of split cord malformations

“…3 Recent surgical models involving chick embryos have lent credence to these theories, demonstrating that a resorbable agar screen does not induce an SCM, whereas an implanted membrane shell or notochord does induce the formation of a split cord. 19 These results provide evidence in opposition to the aberrant primary neurulation hypothesis of SCM. Instead, noninvolution of a firm midline structure prevents fusion and allows infiltration of mesodermal cells from the notochord.…”