Anomalous ependyma inducing split cord and meningomyelocele?

The case is that of a female fetus of 17 to 18 weeks' gestation with major defects of the central nervous system: (1) The thoracic vertebrae demonstra ted rachischisis, with segmental diplomyelia; the duplicated cords were dis similar in size and lay side by side within a single meningeal sheath lacki ng a dividing septum or spur. Cranially to the divided cord lay an unsplit segment of "open cord" lacking the posterior elements and exposing the cent rally placed ependyma of the central canal flanked by glial and epidermal l ining, respectively; it could be regarded as an example of a meningomyeloce le. (2) Heterotopic massed ependymal cells, some of which were actively pro liferating, were associated with the choroid plexus in the brain. Minor ano malies included cerebellar heterotopia and the malpositioning of dorsal roo t ganglia outside the meningeal sheath. Because the ependyma is such a powe rful inducer of the development of neighboring tissue, the findings could b e united by a common pathogenic theme, viz problematic ependymal developmen t and migration within both the brain and spinal cord. The causative agent responsible for these abnormalities remains unidentified, but the balance o f evidence suggests that its effect was felt during the second week of post conceptual age.