Mixed split cord malformation: Are we missing something?

Background: The new classification for split cord malformation, based on the unified theory of embryogenesis includes two types Type I and II defined on the basis of the nature of the medium septum and the state of the dural tube. According to this, these are the only two essential features needed for typing and there is never an overlap between the two main forms. We have described two cases that defy this theory. Case report: We present two patients with split cord malformation who appear to have a combination of features specific to Type I and Type II. Both patients had a partial bony spur within a single dural sac. Conclusion: An overlap between the two forms of split cord malformation does exist. The role of meninx primitiva in the formation of median bony septum is debatable. (C) 2011 Elsevier B.V. All rights reserved.