Dorsal bony septum: a split cord malformation variant.

Split cord malformations (SCMs) are rare spinal anomalies and their classification is still a matter of debate. There is no widespread consensus on the embryological basis of this entity. The unified theory, proposed by Pang et al. [Neurosurgery 1992;31:451-480], was an attempt to explain the embryogenetic mechanism as a basic error occurring around the time when the primitive neuroenteric canal closes. We report two unusual cases of SCMs with a dorsally situated bony spur. We analyzed the radiological, clinical and surgical features of the lesions and were not able to classify these cases according to the unified theory. Further embryological studies should be conducted to elucidate the mechanisms of occurrence of these lesions, and the dorsal bony septum variant should be considered in SCM surgery.