Split cord malformations: report of three unusual cases.

The unified theory, proposed by Pang et al., explains the embryogenetic mechanisms of all variants of split cord malformations (SCMs). All SCMs originate from one basic error occurring around the time when the primitive neurenteric canal closes. The basic error is the formation of an accessory neurenteric canal between the yolk sac and amnion which is subsequently invested with mesenchyme to form an endomesenchymal tract that splits the notochord and neural plate. Three cases of SCMs which support this unified theory are presented. A 3-month-old girl had a combination of both types of SCMs at the level of T11. The 2nd case, a 2-week-old girl, had type-II SCM associated with a thickened filum terminale, lipomyelomeningocele and ectopic renal tissue within lipoma. A lipomatous tract extending from a subcutaneous lipoma to the intradural fibrous septum contained lymphoid tissues and tubular epithelia in a 3-month-old boy with a type-II SCM. These 3 cases support the unified theory.